,,fossils ,a ,/ory ( ! ,rocks & ,_! ,record ( ,prehi/oric ,life ,by ,h>vey ,c4 ,m>kman ,curator ( ,geology & ,paleontology ,cov] ,design & ,murals by ,m>y ,*ilton ,gray ,,d5v] ,,museum ,,( ,,natural ,,hi/ory ,popul> ,s]ies ,no4 #c ,alfr$ ,m4 ,bailey1 ,editor ,?ird ,edition1 ,repr9t$ ,octob] #a1 #aied ,illu/ration3 ,at ,"w on a ,d9osaur ,skeleton ,,cont5ts ,page ,introduction #e ,! ,prehi/oric ,record #e ,v>ieties ( ,fossils #h ,fossilization #i ,floras & ,faunas #ac ,=mations #af ,geological ,"t #ah ,explanation ( ! ,"t ,*>t #bc ,! ,geological ,section #be ,be=e ! ,age ( ,reptiles #ca ,! ,pre-,cambrian ,complex #ca ,cambrian ,life #cc ,! ,ordovician ,record #ce ,silurian ,ev5ts #cf ,devonian ,progress #cg ,c>bonif]\s ,=e/s #dj ,p]mian ,h>d%ips #dc ,! ,age ( ,reptiles #dg ,d9osaurs #dh ,plant ,life & ,climate #ef ,coal & ,fossil ,footpr9ts #eg ,mesozoic ,inv]tebrates #eh ,ext9ct ,birds #fj ,ance/ors ( ! ,mammals #fa ,! ,age ( ,mammals #fd ,prehi/oric ,horses #gj ,ma/odons & ,mammo?s #hj ,! ,ran*o ,la ,brea ,fossil ,pits #hh ,! ,age ( ,man #ic ,supplem5t>y ,read+ #ie ,,li/ ,,( ,,illu/rations ,page ,at ,"w on a ,d9osaur ,skeleton #b ,fossil ,bones 9 ,rock ,=mation #g ,insect ,fossils #aj ,re/oration ( ,rh9oc]os #ab ,d9osaur ,tracks #ag ,"t ,*>t #bb ,geological ,section ,%[+ ,positions ( ,=mations #bf ,m>9e ,b$s ( ! ,b5ton ,=mation #bh ,plesiosaur ,bones 9 ,place #bh ,inv]tebrate ,fossils #cd ,mod]niz$ ,fi%es #ch ,prehi/oric ,plants #da ,m>9e ,reptiles #df ,diplodocus #di ,tra*odon #ea ,/egosaur #eb ,sea ,turtle #ed ,murals1 ,hall ( ,mammals #fc ,u9ta!res & ,contempor>y ,life #fe ,moropus #fg ,titano!res #fi ,oligoc5e ,mammals #ga ,plei/oc5e ,horse #gc ,/ructure ( ,mol> ,tee? #ge ,graz+ ,type ( ,mol> ,tee? #gg ,am]ican ,ma/odon #gi ,long-,jaw$ ,ma/odont #ha ,mol> ,too? ( ,mammo? #hc ,nebraska ,mammo? #he ,ran*o ,la ,brea ,fossils #hg ,folsom ,bison #ij ,man & ,mammo? #ib ,,fossils ,,introduction ,9 ! rec5t gr[? ( k !re has be5 rapid progress 9 two directions4 ,! comm]cial exploitation ( natural res\rces1 be+ fundam5tal to mod]n civilization1 attracts a lib]al %>e ( ! tal5ts & en]gies ( work]s tra9$ = ! indu/rial pr(essions4 ,a second tr5d has specializ$ 9 ! fur!r developm5t ( ! sci5ces :i* are *>act]i/ic ( our "t4 ,su* activities1 9 ! natural hi/ory field1 deal l>gely ) ! ref9em5ts ( exact def9ition1 nom5clature & classification1 all ( :i* means little or no?+ to ! layman :o is o!rwise engag$4 ,= ! latt]1 h[ev]1 !re is a quality ( int]e/ :i* may be describ$ z a :olesome curiosity ab\t :at has happ5$1 h[ x happ5$1 h[ we "k x happ5$1 & :at x may signify to "o :o is nei!r indu/riali/ nor sci5ti/4 ,?is booklet is int5d$ = ! _m :o feel t !re is m to be obta9$ f a natural hi/ory museum ?an an occasional glimpse ( a bewild]+ 8m>vel40 ,9 addition to be+ a guide to fossil exhibits x supplies p>ts ( a great /ory :i* specim5s alone c n relate4 ,,! ,,prehi/oric ,,record ,all t is kn[n ( ! ext9ct plants & animals :i* inhabit$ ! e>? be=e man began ! practice ( record+ 8 obs]vations has be5 obta9$ f a /udy ( ! rocks4 ,! few possible exceptions to ?is rule1 9 :i* animal & plant rema9s h be5 pres]v$ by freez+ or dry+1 are s unusual z to be h>dly wor? m5tion+4 ,explanation ( ?is is t plant & animal tissues quickly decay "u ord9>y conditions :5 life ceases4 ,unless protect$ f de/ructive ag5cies :i* are especially active at ! surface ( ! gr\nd1 ev5 ! heavi] bones ( animals & ! l>ge trunks ( fall5 trees w soon crumble into %apeless masses4 ,! usual me?od employ$ by nature to prep>e a fossil specim5 is s closely relat$ to ! natural process ( rock mak+ t a little k ( t subject w be necess>y 9 ord] to "k :at fossils are & h[ !y are pres]v$ = s long a "t4 ,x %\ld be und]/ood fir/ t a fossil is "s record1 commonly pres]v$ 9 rock1 ( a k9d ( plant or animal :i* no long] exi/s z a liv+ type4 ,?is1 at lea/1 is ! ord9>y s5se ( ! ^w & m elaborate def9itions are ( small s]vice to anyone4 ,x may be necess>y to add1 h[ev]1 t all ?+s :i* h liv$ at any "t are reg>d$ z ei!r plants or animals4 ,nature's way ( produc+ rocks & fossils rema9s a my/]y to _m ( u because we are s wrapp$ up ) ! importance ( f9d+ names = ?+s & mat]ials t we frequ5tly neglect ! consid]ation ( s\rces & hi/ories4 ,ev]yone kn[s a rock :5 he sees x 9 a l>ge mass1 b :5 he looks at s&1 mud1 du/1 or soil1 he seldom ?9ks ( x z relat$ 9 any way to rocks4 ,al?\gh ! diff]5ce is almo/ entirely a matt] ( size1 our use ( words makes x seem unreasonable to speak ( ! f9] p>ticles z rock4 ,!re c be no reality or mean+ 9 ! natural record = an individual :o has fail$ to obs]ve a few simple facts :i* involve *anges go+ on 9 all p>ts ( ! _w at ! pres5t "t4 ,) reg>d to rocks1 x is suppos$ t :at happ5s 9 our day also occurr$ "u l circum/ances ages ago4 ,anyone wi%+ to d s may see = himself t rock masses break d[n :]ev] !y are expos$ to ! elem5ts1 t ! l>g] pieces are r$uc$ to small] fragm5ts1 & t ! f9al product is s& or du/4 ,he may also note t ?is f9ely gr\nd mat]ial is be+ mov$ & sort$1 by ra91 w9d1 & /reams1 transport$ to l[] levels & accumulat$ 9 great quantities :]ev] x f9ds a re/+ place4 ,along ) x g /icks & leaves1 bugs1 %ells1 bones & c>casses ( animals1 "s ( :i* 9 "t may become fossils4 ,9 l>ge lakes & seas !re is a /eady di/ribution ( su* mat]ials ov] broad areas1 ye/]day's accumulation ( s$im5ts be+ buri$ by ! contributions ( today1 ! mo/ rec5t ( ! settl+s always re/+ ^u old] ones until some?+ happ5s to di/urb t arrangem5t4 ,n s readily obs]v$ are o!r p>ts ( ! process1 su* z ! consolidation ( s&s & muds into ! firm s&/ones & %ales :i* we aga9 recognize z rocks4 ,mu* ( ?is requires m ?an ! few score ye>s ( a human lifetime = its accompli%m5t1 b _m ( u h se5 muds become s solidifi$1 by m]ely dry+1 t !y c\ld h>dly be di/+ui%$ f prehi/oric %ales4 ,x is to be not$ also t "s anci5t fossils come f s&/ones :i* are sc>cely m rock-l ?an ! loose s&s ( an ocean bea*4 ,?us we le>n t firm consolidation ( rock-mak+ mat]ials is n always a sign ( great antiquity1 & t h>dness ( rock is n always ess5tial to ! pres]vation ( imb$d$ plants & animals4 ,illu/ration3 ,rh9oc]\s ,bones z ,f\nd 9 ! ,rock ,?is exhibit 0 tak5 f ! fam\s fossil qu>ry at ,agate1 ,nebraska4 ,! fossiliz$ rema9s are /ill p>tially imb$d$ 9 ! s&/one :i* pres]v$ !m = millions ( ye>s4 ,! rocks !mselves mu/ expla9 ! _m ?+s :i* h happ5$ dur+ ! c\rse ( millions ( ye>s1 & ?is !y d rem>kably well :5 c>efully /udi$1 = _m ( ! factors involv$ 9 _! hi/ories leave *>act]i/ic m>ks4 ,*ang+ climates1 ! dra9+ ( seas1 ! uplift+ ( m\nta9 ranges1 all h ways ( regi/]+ _! occurr5ce :i* are z conv9c+ & reliable z any?+ ev] writt5 by man4 ,piece by piece ! /ory has be5 pat*$ toge!r ?r\gh ! ef=ts ( ?\s&s ( inve/igators4 ,p>ts ( ! n>rative rema9 buri$ at inaccessible dep?s1 & :ole *apt]s1 no d\bt1 h be5 de/roy$ by ! same =ces t compos$ ?is trem5d\s record ( prehi/oric times4 ,,v>ieties ,,( ,,fossils ,x w\ld be a s]i\s mi/ake to reg>d nature z divid$ into a numb] ( di/9ct & indep5d5t s*ools ( fossil mak+1 ea* refus+ to use ! me?ods & devices ( ano!r4 ,!re are1 h[ev]1 c]ta9 features :i* /& out s prom95tly t a little classification becomes helpful4 ,:ile ?is proc$ure br+s out diff]5ces x %\ld be und]/ood t processes actually "w toge!r1 sev]al ( !m usually be+ involv$ 9 ! production ( any individual specim54 7#a7 ,impressions ( animals & plants1 or p>ts ( ^!1 are frequ5tly left 9 s(t s& or mud :i* lat] becomes conv]t$ into m durable rock4 ,?is type ( fossils is repres5t$ by animal foot-pr9ts & ! impr9ts ( leaves1 fl[]s1 insects1 & l objects :i* may be m+l$ ) ! f9ely gr\nd mat]ials ( ! common s$im5t>y rocks4 7#b7 ,p>ts ( plants & animals may be gradually replac$ by m9]al matt] ) little or no *ange f orig9al =m & texture4 ,fossils ( ?is class are said to be petrifi$ or turn$ to /one4 ,!y are also kn[n z replacem5ts4 ,! fle%y p>ts ( animals d n petrify4 7#c7 ,_m animals among ! inv]tebrates use m9]al sub/ances = protective or support+ /ructures4 ,small plants ( v>i\s k9ds foll[ a simil> practice4 ,^! /ructures1 be+ produc$ 9 /ony mat]ials1 are readily conv]t$ into fossils4 ,! %ells ( mollusks are ! be/ kn[n illu/rations 9 ?is field1 & all t is requir$ = a %ell to become a fossil is ! ext9ction ( ! species ( animal t produc$ x4 ,fossils ( ?is type are extremely abundant4 7#d7 ,pres]vative sub/ances o!r ?an ^? :i* produce common rocks may be m5tion$ among fossil-mak+ possibilities4 ,bones are kn[n to h be5 pres]v$ 9 asphalt1 & insects 9 res9s1 b su* cases are few 9 comp>ison ) ! products ( o!r me?ods4 7#e7 ,9 r>e in/ances !re has be5 pres]vation ( ext9ct creatures by ! process ( dry+ or by refrig]ation4 ,occasional mummies are f\nd ) %rivel$ fle% & sk9 /ill 9 place1 b bett] pres]vation ( all tissues occurs :5 ! temp]ature is quickly r$uc$ bel[ freez+ po9t & held !re )\t int]ruption4 ,?is c happ5 only 9 ! cold] p>ts ( ! e>? & is always subject to climatic *ange4 ,! effect ( dry+ also may be undone at any "t by a slight increase 9 ! am\nt ( moi/ure4 7#f7 ,coal b$s (t5 produce fossils ( an unusual sort4 ,9 ! =mation ( coal1 plant mat]ial gradually loses "s ( its m p]i%able sub/ances b reta9s c>bon :i* has bett] la/+ qualities & sl[ly accumulates to produce ! seams & b$s t are m9$4 ,9 ! e>ly /ages ( ! process ! orig9al vegetation und]goes little *ange 9 appe>ance b ev5tually practically all ( its "* is lo/4 ,_m fossil leaves are f\nd z ?9 lay]s ( c>bon1 b$d$ 9 ! clays :i* are commonly associat$ ) coal deposits4 7#g7 ,concretions1 :i* are h>d5$ lumps ( m9]al sub/ances occurr+ commonly 9 s&/ones & %ales1 are (t5 mi/ak5 = fossils because ( _! peculi> %apes4 ,h[ev]1 !re are localities 9 :i* ! m9]al solutions h be5 conc5trat$ & deposit$ ar\nd %ells1 leaves1 se$s1 or simil> objects1 ?us produc+ an abundance ( fossils :i* may be obta9$ by op5+ ! concretions4 ,fossils ( ?is type are well kn[n f ,mazon ,creek & o!r di/ricts 9 ,ill9ois1 ,kansas1 ,colorado1 & else:]e4 ,,fossilization ,footpr9ts ne$ little explanation o!r ?an a consid]ation ( ! factors :i* make x possible = !m to be pres]v$4 ,! s& or mud mu/ be nei!r too s(t nor too h>d to take ! =m ( ! foot & reta9 its %ape :5 ! foot is )drawn4 ,!n 9 "s mann] ! impression mu/ be protect$ :ile ! rock-mak+ process goes on4 ,:5 su* protection is obta9$ x is usually 9 ! =m ( m mud & s&1 deposit$ ov] ! surface :i* receiv$ ! impression4 ,at a lat] "t ! cov]+ may be sep>at$ f ! l[] "p ( ! deposit1 :i* s]ves z a mold1 & if ! sep>ation be accompli%$ successfully a natural ca/ ( ! foot w be obta9$ z well z ! mold 9 :i* x 0 produc$4 ,s9ce conditions = p]fect "w are n always pres5t 9 a laboratory ( ?is k9d1 x is n surpris+ t fossil footpr9ts are v r>e consid]+ ! numb] & v>iety ( tracks left by w&]+ animals4 ,impressions ( leaves are expla9$ 9 mu* ! same way except t ! leaf rema9s "u its protective cov]+ until x decays4 ,simil> impressions may be obta9$ f ! bodies ( delicate inv]tebrate animals b !y are seldom pres]v$ because ( ! s(tness ( ! tissues4 ,! small] fi%es provide mu* bett] mat]ial = ! production ( fossils accord+ to ?is me?od4 ,:ile ! fi% is be+ flatt5$ by ! weight ( surr\nd+ s$im5ts1 scales1 f9s1 & s(t bones reta9 _! positions & provide ! necess>y resi/ance to leave an impression ( ! body =m :5 ! fle% is gone4 ,illu/ration3 ,insect ,fossils 7enl>g$7 ,f9e specim5s ( ?is type are obta9$ f an old lake b$ at ,florissant1 ,colorado4 ,! l>g] & m spectacul> fossils1 su* z skeletons1 skulls1 & deta*$ bones are ne>ly always ( ! replacem5t type4 ,replacem5t ( plant & animal sub/ances by m9]al matt] is a sl[ process & 9 y\ng] fossils ! *ange is r>ely complet$1 "s ( ! orig9al mat]ial be+ pres5t 9 a p>tially alt]$ condition or n modifi$ at all4 ,s9ce air does n (t5 c>ry ! necess>y mat]ials & provide o!r ess5tial conditions1 replacem5t may be reg>d$ z some?+ :i* happ5s und]gr\nd or 9 wat]4 ,x is p]haps be/ expla9$ 9 connection ) lime/ones1 because calcite or 8lime0 is frequ5tly ! replac+ sub/ance al?\gh o!r m9]als1 especially qu>tz1 may s]ve ! purpose4 ,besides conv]t+ bony or woody objects into rock sub/ance1 m9]al replacem5ts may assi/ 9 ! production & pres]vation ( fossils 9 ano!r mann]4 ,x (t5 results 9 ! fil+ ( cavities ) "s rock-mak+ sub/ance :i* ret>ds de/ruction ?r\gh cru%+ or o!r injury4 ,9 _m cases1 s-call$ fossil %ells are n %ells at all2 in/ead1 !y are m]ely a /ony fill+ :i* 0 once surr\nd$ by %ell sub/ance4 ,9 o!r in/ances ! orig9al %ell rema9s z x 0 dur+ ! life ( its =m] occupant1 pres]vation ( ! %ell be+ due l>gely to ! sub/itution ( a m9]al fill] = ! s(t animal tissues once pres5t4 ,lime/one comes into exi/5ce ?r\gh a m elaborate process ?an t :i* produces s&/one & %ales4 ,x is "o ( ! ?ree types ( common rocks1 kn[n collectively z ! s$im5t>ies1 9 :i* fossils are f\nd4 ,x diff]s f s&/ones & %ales1 h[ev]1 9 t mu* ( its sub/ance has be5 dissolv$ 9 wat] in/ead ( be+ transport$ 9 ! =m ( f9ely gr\nd rock p>ticles4 ,lime occurs 9 _m v>ieties ( rock :i* are expos$ to ! we> & te> ( ! elem5ts ?r\gh\t ! _w4 ,sl[ly b m or less cont9u\sly x is tak5 f ?is s\rce by gr\nd & surface wat]s com+ 9 contact ) x4 ,p>ticul>ly active is c>bonat$ wat]1 mov+ und]gr\nd ?r\gh pores & crevices4 ,?is und]gr\nd circulation ( m9]al matt] 9 a dissolv$ condition expla9s ! occurr5ce ( fossils 9 l& areas :i* h n necess>ily be5 subm]g$ dur+ any great l5g? ( "t1 = x is well kn[n t plant & animal rema9s are n inv>iably wa%$ into lakes or seas1 & t all s$im5t>y deposits h n be5 built up 9 l>ge bodies ( wat]4 ,"h we are deal+ ) :at is kn[n z ! cont95tal type ( s$im5tation & su* fossils z d9osaurs1 ma/odons1 ?ree-to$ horses1 & o!r =m] inhabitants ( l& areas4 ,9 ord] to become prop]ly fossiliz$1 c]ta9 conditions are absolutely necess>y1 & only a small p]c5tage ( ! once-liv+ multitude secures ! requir$ treatm5t4 ,!re mu/ be pres5t1 soon aft] dea?1 "s protection f ! activities ( ! c>nivor\s birds & bea/s t w\ld sep>ate & scatt] ! p>ts ( a c>cass1 also f ! small] gnaw+ animals t w\ld cont9ue ! de/ruction1 & f9ally f w9d1 sun1 ra91 fro/1 & bact]ial & *emical activities :i* 9 ! c\rse ( only a few ye>s w\ld remove ev]y?+ b possibly a few scraps ( too? enamel1 :i* is ! h>de/ ( animal tissues4 ,a slight cov]+ ( e>? sub/ance 9 any =m s]ves to *eck ! dis9tegration1 & ?is may be acquir$ 9 sev]al ways4 ,animals t p]i% 9 bogs or quicks&s are soon cov]$ ov]2 9 _m localities w9d-bl[n du/ & s& d ! "w2 & flood$ riv] valleys provide an abundance ( mud = ! necess>y burial ( o!rs4 ,ev5 und]gr\nd1 ! decay ( s(t tissues is too rapid to p]mit ( replacem5t by m9]al sub/ance 9 a mann] t w\ld reproduce =m & texture4 ,sk9 & fle% are almo/ inv>iably lo/1 al?\gh 9 a few in/ances ! ?ick scaly hides ( d9osaurs are kn[n to h produc$ natural molds & ca/s by ! me?od expla9$ 9 connection ) footpr9ts & o!r impressions4 ,illu/ration3 ,! skeleton ( ?is prehi/oric ,am]ican rh9oc]os is m\nt$ 9 a 8half %ell0 :i* 0 model$ ov] ! bones to %[ ! =m ( ! liv+ animal4 ,! arti/'s recon/ruction appe>s 9 ! pa9t+ above ! fossil exhibit4 ,) reg>d to ! m durable tissues f\nd 9 ! tee?1 bones1 & %ells ( animals1 or ! woody p>ts ( plants1 ! case is diff]5t4 ,^! p>ts become firmly imb$d$ 9 ! gr\nd1 b moi/ure /ill has access1 & x beg9s to "w imm$iately2 = all wat] mov+ und]gr\nd f9ds soluble sub/ances :i* x picks up & c>ries ) x :]ev] x goes1 & mu* ( ! load consi/s ( m9]al matt] :i* may be unload$ aga9 :5 ! necess>y conditions are f\nd4 ,m9]al-lad5 wat]s w drop "o k9d ( sub/ance to take up ano!r :i* dissolves m readily1 & ?is happ5s soon] or lat] :5 a buri$ bone or log is enc\nt]$4 ,complications ( v>i\s sorts ent] into ! process1 b ! f9al outcome frequ5tly is a complete *ange f "o *emical composition to ano!r :i* is m endur+1 ! trans=mation be+ br\ght ab\t s gradually & ?or\ghly t 9 _m fossils ! inn] /ructure ( ! orig9al tissue is z accurately reproduc$ z ! f9e detail ( surface features4 ,conv]t$ into /one1 h[ev]1 ! result is /ill f> f p]man5t4 ,:ile yet und]gr\nd ! fossil is subject$ to di/ortion & breakage due to e>? movem5ts :i* b5d & dislocate ! rock deposits4 ,:at causes ^! upheavals & depressions ( ! e>?'s surface rema9s ! subject ( mu* discussion1 b t !y h occurr$ on a l>ge scale & cont9ue to occur is cle>ly evid5t4 ,at high] altitudes ! surface rocks & fossils are expos$ to a l>g] v>iety ( de/ructive activities ?an at l[] levels :]e protective cov]+s are m likely to be provid$ & reta9$4 ,once /ripp$ ( t protection !re is little *ance = a fossil to survive4 ,beyond a d\bt !re are _m ?\s&s ( tons ( prehi/oric rema9s damag$ or de/roy$ ea* ye>1 by wea!r & /ream erosion4 ,,floras ,,& ,,faunas ,z ! v>i\s types ( s$im5ts cont9ue to accumulate on l& & 9 wat] !y produce deposits ( s&/ones1 clay/ones1 & lime/ones :i* 9 "t may acquire great ?ickness & cov] wide areas ( sea floor1 or cont95tal surface4 ,usually !re is m or less mix+ ( s$im5ts result+ 9 s&y lime/ones1 limy clays1 & o!r comb9ations4 ,q commonly1 h[ev]1 ! types rema9 fairly pure b become arrang$ 9 lay]s :i* alt]nate f "o k9d ( mat]ial to ano!r4 ,at all times ! "* ( ! deposit w dep5d ^u ! nature ( ! rocks :i* supply ! mat]ials1 & any fossils t may be produc$ w consi/ ( su* plants & animals z live & die dur+ ! "t ! rock is 9 ! mak+4 ,"s ( ! rock lay]s w be ri* 9 plant & animal rema9s1 o!rs q b>r51 ! diff]5ce be+ due p>tly to conditions influ5c+ ! life ( ! region4 ,9 addition1 ! "* & am\nt ( rock-mak+ mat]ials at ! "t may be favorable or unfavorable to ! pres]vation ( fossils4 ,seas1 lakes1 & valleys may at any "t be dra9$1 or enl>g$ & deep5$1 by *anges 9 ! elevation ( und]ly+ rocks4 ,! am\nt & v>iety ( m9]al sub/ances dissolv$ 9 ! wat]s ( a region n only affect ! "* ( rock deposits b also ! plants & animals liv+ 9 ! wat]4 ,"s ( ^! *emical solutions provide cem5t+ mat]ials :i* b9d toge!r ! gra9s ( s&s & mud2 o!rs h a detrim5tal effect ^u cem5t+ mat]ial previ\sly deposit$1 & s con/ruction & de/ruction g on cont9u\sly1 m or less h& 9 h&1 to produce complicat$ & (t5 puzzl+ results4 ,a little m salt1 or a little less ( x1 may *ange completely ! v>iety ( life inhabit+ a body ( wat]4 ,a slight *ange 9 ! dep? ( ! wat] (t5 accompli%es ! same ?+1 = plants & animals are s delicately adju/$ to _! environm5ts t conditions fatal to "o race ( creatures may provide ! exact life requirem5t ( ano!r4 ,?is is a matt] ( practical k :i* is be+ us$ today 9 ! cultivation ( plants & animals = m>ket purposes4 ,x is be+ demon/rat$ cont9u\sly1 also1 ^u liv+ subjects 9 exp]im5tal laboratories ?r\gh\t ! _w2 &1 9 a bigg] way1 ! facts are obs]vable :]ev] life is consid]$ 9 relation to habitat4 ,t any?+ s obvi\s %\ld be reg>d$ z guesswork or !oriz+1 or oppos$ to tru?1 :5 appli$ to =m] inhabitants ( ! e>?1 is some:at surpris+4 ,&1 x may be add$1 ! cultural wor? ( fossil /udy comes to a focus on ?is v po9t1 = m5 & wom5 are n[ m$dl+1 consci\sly or unconsci\sly1 wisely or unwisely1 ) an all-important environm5t ab\t :i* !y h le>n$ v little--"o call$1 among o!r ?+s1 8civilization40 ,= any portion ( ! _w a complete-li/ ( ! diff]5t k9ds ( plant inhabitants comprises ! flora ( t region1 & a l summ>y = ! animal life is kn[n z ! fauna ( ! di/rict4 ,x is g5]ally und]/ood t diff]5t species ( bo? plants & animals inhabit diff]5t regions ( ! e>?1 b outside ( pr(essional circles x is only beg9n+ to be recogniz$ t *anges 9 floras & faunas occur f "t to "t1 t slight diff]5ces may be not$ 9 ! c\rse ( obs]vations ext5d+ ov] a p]iod ( only a few ye>s1 & t ev]y?+ 9 a fauna or flora ev5tually may be displac$ by new =ms4 ,x is1 h[ev]1 a conv5i5t practice to use ^! t]ms 9 connection ) "t p]iods1 rock b$s1 & types ( environm5t1 z well z geographical areas4 ,?us we h su* phrases z a 8,cretace\s fauna0 7atta*+ ! "n ( a geologic p]iod71 a 8,b5ton fauna0 7) ref]5ce to ! fossils ( a rock =mation71 a 8m>9e flora0 7us+ ! "n ( an environm5t71 an 8,arctic flora0 7:i* applies to a def9ite portion ( ! e>? surface & its plant inhabitants74 ,faunas include animals :i* _m p]sons d n recognize z su*4 ,sponges1 corals1 insects1 worms1 crabs1 oy/]s1 & a ho/ ( o!r boneless creatures are gr\p$ toge!r z inv]tebrate animals1 :ile ano!r gr\p includes ! fi%es1 amphibians 7toads1 frogs1 & salam&]s ( today71 reptiles 7crocodiles1 liz>ds1 snakes1 & turtles be+ well kn[n v>ieties71 birds1 & mammals4 ,?is second lot1 provid$ ) backbones & skeletons1 comprise ! great division ( v]tebrate animals4 ,floras also include types :i* are commonly se5 b n popul>ly id5tifi$ z plants4 ,! algae are p]haps be/ kn[n z seawe$s1 wat]-silk1 & pond scums2 fungi z toad/ools & m\lds4 ,bo? gr\ps are l>ge & ( important rank 9 ! vegetable k+dom2 only ! algae1 h[ev]1 are recogniz$ z important fossil produc]s4 ,bett] kn[n types ( plants are ! mosses1 f]ns1 ev]gre5s1 grasses1 & ! m conspicu\s fl[]-be>+ =ms1 f we$ size to tree size4 ,_m rocks owe _! "* to ! "w ( l>ge colonies ( plants or animals1 = ! liv+ organisms are frequ5tly ! active ag5cy :i* takes dissolv$ m9]al sub/ance f ! solv5t liquid & gets x back into solid =m4 ,! liquid is1 ( c\rse1 ! wat] 9 :i* ! creatures live1 :ile ! m9]al sub/ance (t5 becomes a commodity requir$ by a plant or animal 9 its mode ( liv+4 ,mollusks h a way ( us+ lime 9 ! production ( %ells1 & _m a b$ ( lime/one consi/s almo/ entirely ( ?is by-product ( molluscan life4 ,t9y coral polyps build complicat$ & beautiful /ructures f ! same m9]al sub/ance4 ,ei!r intact or 9 brok5 condition1 ^! /ructures contribute 9 a l>ge way to ! mak+ ( lime/ones4 ,algae1 among ! l[lie/ ( plants1 h done ext5sive "w along simil> l9es1 & num]\s inv]tebrate animals c\ld be nam$ z important factors 9 ! production ( rocks4 ,_m ( ! %ells & o!r fabrications reta9 _! peculi> patt]ns long aft] ! ext]m9ation ( _! mak]s1 & a highly in=mative "p ( ! fossil record is provid$ 9 ?is mann]4 ,x is also by f> ! l>g] portion ( ! record1 = ! e>li] ages ( prehi/oric "t fail$ to produce a v]tebrate animal ( any k9d1 :ile ! inv]tebrate record dates back to pre-,cambrian "t4 ,,=mations ,if 9 "s "p ( ,nor? ,am]ica !re _h be5 /eady accumulation ( s$im5t>y mat]ials "u con/antly favorable conditions s9ce ! beg9n+ ( ,cambrian "t1 ! result w\ld h be5 a deposit ( s&/ones1 clay/ones1 & lime/ones measur+ ne>ly fifty miles f bottom to top4 ,^! figures are bas$ on actual production 9 ,nor? ,am]ica :]e ext5sive measurem5ts h be5 made 9 _m localities4 ,:5 o!r p>ts ( ! _w are z ?or\ghly inve/igat$ & old] deposits includ$ 9 ! calculations1 ! total ?ickness ( su* b$s w probably be m ?an "o hundr$ miles4 ,no s+le pile ( rocks (f]+ a complete cross section ( ! geological record has ev] be5 produc$1 b portions ( ! section are expos$ to view on all ! cont95ts4 ,9 ord] to c>ry on desirable inve/igations & make comp>isons1 x has be5 necess>y to divide ?is great composite section into small units :i* may be nam$ 9 "s way & plac$ def9itely ) relation to l[] & high]1 or old] & y\ng]1 lay]s4 ,to s]ve ?is purpose !re has be5 develop$ ! idea ( rock =mations1 & "h we h a ^w :i* is n def9$ readily1 ev5 = ! use ( ^? :o are famili> ) x4 ,nev]!less x is us$ s commonly t "s und]/&+ ( its mean+ becomes desirable4 ,a =mation may be reg>d$ z an ext5sive rock mass1 v>iable1 9 ?ickness & o!r proportions1 z well z 9 composition1 b repres5t+ a p]iod ( "t dur+ :i* !re 0 no great *ange 9 ! "* ( plant & animal life1 & no s]i\s int]ruption 9 ! deposit+ ( ! rock-mak+ mat]ials4 ,occasionally ! l[] & upp] limits ( a =mation are well def9$ & readily locat$4 ,frequ5tly1 h[ev]1 ! transition is gradual1 "o =mation m]g+ into ano!r ) no app>5t m>k ( sep>ation4 ,9 su* ev5t ! orig9al description s]ves to e/abli% m or less def9itely ! b\nd>ies ( a =mation4 ,descriptions are publi%$ :5ev] a work] believes he has discov]$ a significant "p ( ! great section :i* has n previ\sly be5 nam$4 ,! usual practice is to apply a "n tak5 f ! locality 9 :i* ! b$s 7 inve/igat$1 & 9 ?is mann] ! names ( =mations become associat$ ) t[ns1 riv]s1 c\nties1 m\nta9s1 /ates & o!r geographical features4 ,! locality :i* supplies ! "n is !n reg>d$ z ! 8type locality0 = ! =mation1 b :]ev] ^! same b$s may be trac$ or o!rwise id5tifi$ ! "o =mation "n applies4 ,illu/ration3 ,d9osaur ,tracks ,an anci5t trail 9 s&/one ( ! ,dakota =mation4 ,ea/ slope ( ! hogback1 we/ ( ,d5v]4 ,! 8,dakota =mation10 to use a conv5i5t illu/ration1 is m5tion$ 9 scores ( reports be>+ on ! geology ( ,colorado1 ,i[a1 ,kansas1 ,nebraska1 ,new ,mexico1 ,texas1 ,utah1 & ,wyom+1 z well z ! ,dakotas4 ,on ! geological map ( ,colorado x appe>s on bo? sides ( ! ,rockies1 scatt]$ 9 /rips & pat*es f nor? to s\? b\nd>y l9es4 ,! b$s are easily locat$ 9 ! foo?ills di/rict we/ ( ,d5v] because ( _! t5d5cy to produce ! prom95t ridges kn[n z hogbacks4 ,_m =mations are expos$ ov] mu* less t]ritory1 "s h ev5 great] ext5t4 ,?ickness may v>y f a few in*es to ?\s&s ( feet1 & no two exposures w be exactly alike ?\gh "s simil>ity necess>ily prevails ?r\gh\t4 8,exposures0 are simply portions ( ! b$s :i* are n conceal$ by loose rock1 soil & vegetation1 or ov]ly+ =mations4 ,canyon walls1 /eep cliffs & m\nta9 slopes1 gullies1 & badl&s provide a l>ge v>iety ( natural exposures4 ,9 su* places rocks & fossils may be /udi$ to be/ advantage4 ,s9ce a =mation may conta9 a v>iety ( b$s1 includ+ s&/ones1 %ales1 lime/ones1 & all sorts ( mixtures1 !re is sometimes ne$ ( subdivid+ x2 b =mations are ! smalle/ units commonly %[n on geological maps4 ,!y are actual rocks :i* fit into a hi/orical s*eme ( ?+s & may be reg>d$ aptly z ! pages ( a book :i* nature has done 9 /one4 ,,geological ,,"t 8,h[ old are !y80 8,h[ c y le>n _! names f ! rocks80 ,^! are typical examples ( que/ions mo/ frequ5tly ask$ conc]n+ fossils4 ,! second "q foll[s ! usual reply to ! fir/1 = prehi/oric plants & animals are z old z ! rocks 9 :i* !y are f\nd4 ,! answ]1 z to age1 mu/ come f ! rocks & :at we h le>n$ ab\t !m ?r\gh _m ye>s ( h>d "w1 ?\ghtful obs]vation1 & c>eful /udy4 ,names1 h[ev]1 come f a diff]5t s\rce4 ,nature1 app>5tly1 manag$ = a long "t to c>ry on )\t ! use ( words4 ,s9ce man began talk+ he has _h no tr\ble inv5t+ names = ?+s :i* int]e/ him4 ,e>ly /ud5ts ( rocks & fossils likewise accompli%$ a great deal )\t be+ able to date ev5ts 9 t]ms ( ye>s al?\gh _m ( _! ef=ts & int]e/s c5t]$ on ! problem ( discov]+ a cont9u\s sequ5ce ( ev5ts 9 ! fragm5ts ( evid5ce t _h be5 uncov]$4 ,?is relatively simple problem has n be5 fully work$ out1 & "s ( ! breaks 9 ! record are recogniz$ z 8"t gaps0 :i* may nev] be conv]t$ into hi/ory4 ,! "q ( "t1 express$ 9 ye>s1 has be5 a puzzle :i* attract$ "s att5tion ev5 9 ! e>lie/ days ( inve/igation4 ,its solution 0 attempt$ by sev]al me?ods long be=e !re 0 suffici5t in=mation to make !m "w satisfactorily1 :i* acc\nts 9 "p = ! extreme v>iation 9 results ( ! calculations4 ,ev5 n[ x is to be expect$ t *anges w h to be made z long z p]t95t /udies are cont9u$4 ,two ( ! mo/ promis+ me?ods ( inve/igation 9 late ye>s h be5 produc+ figures :i* are surpris+ly l>ge4 ,m accuracy ?an ev] be=e is probably pres5t 9 mod]n e/imates b1 except = comp>atively rec5t "t1 !re is yet no way ( kn[+ )9 a range ( millions ( ye>s :5 a creature liv$4 ,a/ronomy & physics 7 us$ 9 e>ly calculations b1 al?\gh tak5 s]i\sly by "s geologi/s1 x 0 soon recogniz$ by o!rs t c]ta9 ev5ts reveal$ by e>? hi/ory c\ld n be expla9$ ) s %ort a "t all[ance z ^! me?ods indicat$4 ,"o ( ! fir/ e/imates provid$ a total ( only tw5ty-five millions ( ye>s & includ$ a great /ret* ( "t dur+ :i* ! e>?1 accord+ to prevail+ !ory1 0 m sun-l ?an rock-l1 a "t :5 planets 7 be+ born & ! e>? c\ld n h be5 9 its pres5t physical condition1 :i* is ! *ief conc]n ( ! geologi/4 ,s9ce ^? e>li] conditions c\ld n h support$ life z we "k x1 our k ( cosmic hi/ory r5d]s small s]vice 9 ! /udy ( fossils4 ,among ! me?ods sugge/$ by a/ronomy & ! laws ( physics is "o :i* is bas$ on ! probable rate at :i* ! e>? cool$ f its molt5 condition to pres5t temp]ature4 ,x is believ$ n[ t ! heat ( ! e>? is n necess>ily due to an orig9al molt5 /ate & t a /eady rate ( cool+ _c be asc]ta9$4 ,any figures bas$ on su* proc$ure1 !re=e1 are discr$it$ today4 ,! am\nt ( salt 9 ! oceans1 & ! "t requir$ = its conc5tration !re by natural processes1 (f]s ano!r way ( attack+ ! problem4 ,x is a well kn[n fact t salt is be+ add$ to ! seas at a fairly con/ant rate2 sea wat]1 !n1 mu/ become salti] f ye> to ye>4 ,! salt comes f rocks expos$ on l& surfaces & is transport$ by ! riv]s :i* dra9 ^! areas4 ,by analyz+ ! riv] wat]s x is possible to e/imate ! am\nt ( salt annually dump$ into ! oceans &1 also by *emical analysis1 x is a comp>atively simple matt] to figure ! total am\nt n[ pres5t 9 ! oceans4 ,"s rec5t calculations indicate t ?irty-five million tons ( salt are be+ add$ ea* ye>1 & ?is figure divid$ into ! total am\nt = all ! ye>s places ! age ( ! oceans at ?ree hundr$ sixty millions ( ye>s4 ,h[ev]1 !re are c]ta9 o!r factors :i* complicate ! problem4 ,= in/ance1 x is kn[n t l& areas expos$ to surface dra9age h n always be5 ( _! pres5t size1 & ! annual production ( salt by ! diff]5t types ( rocks expos$ at v>i\s times 9 ! hi/ory ( ! e>? has n always be5 z x is n[4 ,! rocks also mu/ be old] ?an ! oceans1 b h[ mu* old] _c be det]m9$ by means ( figures obta9$ 9 ?is way4 ,until ! beg9n+ ( ?is c5tury !re 0 little anticipation ( a bett] measur+ /ick ?an "o 9 use at ! "t :i* plac$ its reliance on ! total ?ickness ( ! s$im5t>y deposits & ! l5g? ( "t requir$ to produce ?is great accumulation ( mat]ial :i* is kn[n z ! geological column4 ,s9ce ! total ?ickness1 or height ( ! column1 0 n accurately kn[n1 & ) recogniz$ "t gaps to bridge1 !re 0 little hope ( work+ out a complete *ronology by ?is device1 b x has suppli$ highly desirable & reliable in=mation conc]n+ p>ts ( ! record4 ,! sy/em has be5 some:at improv$ s9ce its e>lie/ use1 & "o ( its late/ applications gives u an age1 = kn[n s$im5t>y rocks1 ( ne>ly half a billion ye>s1 ?is be+ bas$ on a total ?ickness ( "o hundr$ miles & an av]age rate ( #hhj ye>s = ! build+ up ( "o foot ( s$im5ts4 ,its greate/ weakness is due to ! abs5ce ( a reliable factor to take c>e ( long /ret*es ( "t 9 :i* ! s$im5t>y rocks are kn[n to h be5 subject$ to de/ructive processes4 ,a y>d/ick ( ?is "* _c be appli$ to rocks t h be5 de/roy$1 & !re are excell5t reasons = believ+ t ^! int]ruptions may acc\nt = sev]al times ! lapse ( ye>s indicat$ by ! am\nt ( rock rema9+ 9 ! column :i* has be5 piec$ toge!r4 ,foll[+ ! discov]y ( radium1 h[ev]1 ! pres5t c5tury provid$ a new field ( k :i* has contribut$ greatly to ! measurem5t ( geologic "t4 ,! p5etrat+ rays produc$ by radium & o!r radioactive sub/ances are due to extremely sl[ b viol5t dis9tegration ( ! mat]ial4 ,uranium & ?orium are radioactive elem5ts :i* occur 9 ! rocks ( _m p>ts ( ! _w4 ,!re is little or no loss ( mat]ial z ! s-call$ dis9tegration proce$s2 in/ead !re is a complicat$ s]ies ( trans=mations 9 :i* o!r elem5ts are produc$1 radium itself be+ "o ( ^!4 ,helium & lead ev5tually take ! place ( ! less /able elem5ts & ! kn[n rate at :i* ^! products accumulate provides ! highly desir$ key to ! age ( ! rocks4 ,"p ( ! gas1 helium1 may escape1 b except 9 r>e in/ances :]e *emical alt]ation might occur1 !re probably is no loss ( lead4 ,=tunately1 :5 ?is metal is produc$ by radioactivity x diff]s slightly 9 atomic weight f ord9>y lead2 o!rwise ! pres5ce ( ! latt] w\ld introduce a mislead+ factor4 ,s9ce ! spe$ at :i* ! *ange goes on _c be increas$ or decreas$1 x is assum$ t ?r\gh\t pa/ ages x has nev] be5 fa/] or sl[]4 ,! am\nt ( su* *ange t has be5 complet$ 9 any body ( radioactive m9]als may be measur$ by te*niques employ$ 9 physics & *emi/ry4 ,if x is f\nd t ! am\nt ( helium or lead pres5t requires a hundr$ million ye>s = its production at ! work+ spe$ ( ! p>5t elem5ts1 ! m9]al deposit mu/ be at lea/ t old4 ,c]ta9 conditions ( c\rse complicate ! problem s]i\sly3 kn[+ ! age ( a piece ( rock :i* happ5s to conta9 "s radioactive elem5t is ( small s]vice 9 hi/orical /udies unless ! rock c be def9itely associat$ ) a flora or fauna1 or "s out/&+ ev5t disclos$ by geological inve/igations4 ,b !re h be5 a few in/ances 9 :i* mo/ ( ! necess>y conditions 7 pres5t1 & m & bett] opportunities to apply ?is me?od w no d\bt appe>4 ,o!r elem5ts1 or _! radioactive isotopes1 are already be+ employ$ ) good results4 ,"s ( ^!1 su* z c>bon #ad1 are m s5sitive indicators = ! accurate dat+ ( ev5ts 9 comp>atively rec5t "t4 ,:5 x c be us$1 ?is type ( measurem5t is f> less subject to unc]ta9ties ?an any o!r4 ,x promises to elim9ate all ne$ = guess+1 & comes close to a degree ( accuracy :i* is satisfactory to ! sci5ti/1 a p]son :o ?or\ghly dislikes unc]ta9ties ( any k9d4 ,if suitable mat]ial c be f\nd 9 j ! "r places x %\ld accompli% :at ! prec$+ me?od _c d--! accurate measurem5t ( ! great "t breaks :i* int]rupt ! geological record 9 _m places4 ,some?+ along ?is l9e already has be5 accompli%$1 = radioactive mat]ial has be5 f\nd 9 "s ( ! olde/ ( ! rocks4 ,reg>dless ( ! de/ruction go+ on 9 o!r localities1 ^! rocks h cont9u$ to regi/] ! pass+ ( "t1 & a trem5d\s antiquity = ! e>? & "s ( its fir/ inhabitants has be5 indicat$4 ,te/s made on radioactive m9]als f ,gilp9 ,c\nty1 ,colorado1 h e/abli%$ ! age ( late ,cretace\s or e>ly ,c5ozoic rocks at sixty million ye>s1 provid+ a conv5i5t & reasonably accurate date = ! beg9n+ ( ! ,age ( ,mammals4 ,9 ,russia1 "o ( ! olde/ m9]al deposits yet /udi$ 9 ?is way & reg>d$ z e>ly ,pre-,cambrian1 produc$ ! a/oni%+ figure ( #a1hej1jjj1jjj ye>s2 :at we commonly ref] to z geological hi/ory may !re=e be reg>d$ z cov]+ a range ( approximately two billions ( ye>s4 ,! e>?1 9 "s =m or o!r1 has 9 all probability pass$ ?r\gh an e>li] hi/ory ( ano!r billion ye>s or m4 ,:]ev] we may roam1 a portion ( ! prehi/oric record is to be f\nd 9 ! rocks und]foot & n f> f ! surface4 ,=mations z already m5tion$ may be reg>d$ z ! pages--(t5 torn & badly scatt]$--( nature's own book1 9 :i* ! geological p]iods are *apt]s4 ,b in/ead ( numb]+ ^! pages & *apt]s we h nam$ !m1 9 ord] to get ! p>ts reassembl$ 9 ord]ly fa%ion & re/or$ to a condition :i* makes ! book legible4 ,h[ev]1 ! names _c r5d] ! s]vice int5d$ except 9 connection ) a "t *>t & an outl9e ( e>? hi/ory4 ,illu/ration3 ,,geological ,,"t ,figures to ! left d5ote millions ( ye>s t h elaps$ up to rec5t "t ,,c5ozoic ,age ( ,man ,,rec5t ,man & 8 ,culture #a ,,plei/oc5e ,la/ ( ,mammo?s ,ma/odons ,age ( ,mammals #g ,,plioc5e ,horses mod]niz$ #bj ,,mioc5e ,grasses & ,graz+ ,animals ,?ree-to$ ,horses1 ,rh9os1 ,camels #ce ,,oligoc5e ,specialization ( ,primitive ,ance/ors #fj ,,eoc5e ,decl9e ( ar*aic types ,mammals fl\ri%+ ,,mesozoic ,age ( ,reptiles #abe ,,cretace\s ,la/ ( ,great ,reptiles ,specialization ( ,d9osaurs #afj ,,jurassic ,bony ,fi%es ?riv+ ,fl[]+ plants advance ,cycads ,birds & ,fly+ ,reptiles #bjj ,,triassic ,few small mammals ( l[] ord]s ,d9osaurs become prom95t ,,paleozoic ,age ( ,amphibians #bbe ,,p]mian ,reptiles advanc+ ,amphibians dom9ant insects #cjj ,,c>bonif]\s ,d5se =e/s ( spore-be>+ plants ,age ( ,fi%es #cej ,,devonian ,%>k-l ,fi%es ,l& floras e/abli%$ #cge ,,silurian ,fir/ l& animals 7scorpions7 ,armor$ ,fi%es prom95t ,age ( ,inv]tebrates #dbe ,,ordovician ,corals & ,bryozoa ,progress among ,mollusks #ejj ,,cambrian ,bra*iopods ga9+ ,trilobites dom9ant ,advance ( %ell$ animals ,,prot]ozoic ,,e>lie/ ,,life #ajjj ,,upp] ,,pre-,,cambrian ,small m>9e inv]tebrates ,l[e/ ,=ms ( ,plant & ,animal ,life ,few ,fossils ,,ar*eozoic #bjjj ,,l[] ,,pre-,,cambrian ,"s *emical evid5ce ( life ,no fossils ,su* aids h be5 devis$ & revis$ f "t to "t4 ,no figures h be5 (f]$ z f9al or absolutely 8"r0 s9ce ! beg9n+ ( sci5tific inve/igations4 ,"t divisions h be5 propos$ t are n yet 9 common use :ile o!rs h be5 ab&on$ or modifi$4 ,s\rces ( in=mation are s num]\s t appropriate cr$it _c be giv5 fairly = any?+ t is up-to-date4 ,! comb9$ *>t & outl9e "h provid$ is bas$ on "t calculations ( rec5t date b ) figures slightly r\nd$ (f = ! sole purpose ( mak+ !m easi] to rememb]4 ,9 view ( ! /ill exi/5t probability ( error x is felt t ! slight alt]ation ( figures may ju/ify itself4 ,x ne$ n be reg>d$ z mislead+ if ! pres5t purpose be consid]$--! /imulation ( a natural hi/ory int]e/ :i* is n vitally conc]n$ ) ! little diff]5ce betwe5 a ?\s& million ye>s & n9e hundr$ n9ety-n9e million ye>s4 ,,explanation ,,( ,,! ,,"t ,,*>t ,! :ole ( geological "t has be5 divid$ & subdivid$ accord+ to v>y+ practices4 ,! developm5t ( life is p]haps ! "o out/&+ feature ( ! "t divisions1 b = ! mo/ "p ! *anges 9 floras & faunas h be5 gradual r ?an abrupt1 & ?is makes x v difficult to draw %>p l9es or to visualize beg9n+s & end+s ( ! v>i\s /ages ( developm5t4 ,occasionally !re is good excuse = draw+ a l9e1 :]e ! record is brok5 & resum$ aga9 aft] a long lapse ( "t4 ,! pr9cipal cause ( su* breaks is ! elevation ( great l& masses1 :i* br+s on an int]val ( erosion & surface de/ruction = ! areas uplift$4 ,^! movem5ts ( p>ts ( ! e>?'s cru/ h be5 exceptionally pron\nc$ at c]ta9 times1 (t5 culm9at+ 9 ! production ( m\nta9 sy/ems1 & because ( ! extreme *anges !y introduce are kn[n z revolutions4 ,! major divisions ( prehi/oric "t h be5 e/abli%$1 at lea/ 9 "p1 by su* revolutions2 cru/al1 climatic1 or o!r di/urbances1 on a small] scale & recurr+ ) great] frequ5cy1 may be reg>d$ z e/abli%+ b\nd>ies = ! m9or divisions4 ,h5ce we h five great ,eras ( geological hi/ory1 & ^! are divid$ aga9 into ,p]iods4 ,! "t *>t %[s an arrangem5t commonly us$ 9 ,am]ica4 ,9 ! fir/ column ! names ( ! ,eras are /at$ 9 te*nical =m4 ,closely co9cid+ ) ^! t]ms are ! popul> names ( ! ,ages :i* appe> 9 ! second column4 ,^! names1 describ+ ! dom9ant life ( ea* age1 are v conv5i5t4 ,! m sci5tific t]ms us$ = ! eras1 :ile s]v+ ess5tially ! same purpose1 are a little m sy/ematic & g5]aliz$ 9 t !y ref] to anci5t life 7,paleozoic71 middle life 7,mesozoic71 & rec5t life 7,c5ozoic71 )\t be+ specific z to any class ( animals or plants = any "o division ( "t4 ,! p]iod names1 9 ! c5tral column1 h be5 d]iv$ f miscellane\s s\rces1 "s ( !m f geographical di/ricts1 "s f descriptive ref]5ces to prom95t features ( ! rocks1 o!rs indicat+ a degree ( approa* to rec5t "t4 ,9 paleontology 7fossil /udy7 x has long be5 a practice to cut ! p]iods into l[]1 middle1 & upp] divisions1 & 9 a few cases x has be5 f\nd desirable to make two p]iods out ( an old "o4 ,:at 0 once kn[n z ! ,l[] ,c>bonif]\s is n[ commonly recogniz$ z ! ,mississippian p]iod :ile ! upp] portion has become ! ,p5nsylvanian4 ,! ,l[] ,cretace\s is n[ ! ,coman*ean ( "s au?ors4 ,bo? old & new practices are responsible = a little confusion at ! pres5t "t4 ,a =m] division into ,prim>y1 ,second>y1 ,t]ti>y1 & ,quat]n>y eras has be5 p>tly ab&on$1 b ! t]m 8,quat]n>y0 /ill applies to ! ,age ( ,man1 :ile 8,t]ti>y "t0 rema9s 9 good usage = ! balance ( ! ,c5ozoic era4 ,among ! new] introductions may be m5tion$ ! use ( a ,paleoc5e p]iod :i* prec$es ! ,eoc5e4 ,geologi/s are n entirely 9 agreem5t z to ! necessity = ?is addition & _m w\ld n give x equival5t rank ) o!r p]iods4 ,9 ! int]e/ ( simplicity ^! mod]n ref9em5ts h be5 omitt$ f ! *>t4 ,! figures appe>+ 9 ! ?ird column1 betwe5 ! ,ages & ,p]iods1 indicate ! millions ( ye>s t h elaps$ up to pres5t "t4 ,!y d5ote ! age ( ! rocks at ! beg9n+ ( ea* p]iod4 ,! age ( a plant or animal :i* liv$ 9 ,eoc5e "t w\ld be1 accord+ to ?is scale1 some:]e betwe5 #ce million & #fj million ye>s4 ,9 practice x is usually possible to det]m9e :e!r a fossil 0 emb$d$ 9 ! rocks dur+ an e>ly or late portion ( ! p]iod1 & ?us its age may be e/abli%$ )9 a %ort] range1 b x is impossible to be exact1 ev5 9 t]ms ( millions ( ye>s1 ) reg>d to any?+ z f> back 9 prehi/ory z ! ,eoc5e p]iod4 ,! p]iod 9 :i* we are liv+ today is kn[n z ,rec5t4 ,x began at ! close ( ! ,ice ,age or ,plei/oc5e p]iod ab\t t5 ?\s& ye>s ago & repres5ts s little ( e>? hi/ory s9ce ! beg9n+ ( life t a *>t _m times ! l5g? ( ?is page w\ld be requir$ to %[ ! re/ ( ! p]iods 9 proportion4 ,! ,cambrian p]iod is an e>ly *apt] 9 :i* ! /ory ( prehi/oric life sudd5ly becomes cle> & ri*ly v>i$4 ,x is1 h[ev]1 mu* f>!r f ! beg9n+ ( ! record ?an x is f ! pres5t1 & ! ,pre-,cambrian eras w\ld require a great deal m space 9 ord] to %[ _! relative l5g?s4 ,! ,ar*eozoic & ,prot]ozoic eras h to "s ext5t be5 divid$ into p]iods1 b ! great antiquity ( ! rocks has obscur$ mu* ( _! hi/ory1 & divisions e/abli%$ = "o locality h be5 ( little s]vice else:]e4 ,consequ5tly1 ! p]iod names are 9 less g5]al use & ! common practice is to ref] to all ?is great /ret* ( "t z ,pre-,cambrian4 ,9 ! la/ column1 at ! "r ( ! *>t1 "s ( ! hi/orical features are indicat$4 ,?is column %\ld be read f bottom to top 9 ord] to get ! prop] developm5t ( ! /ory1 & at be/ ?is sket*y outl9e ( ev5ts c be no m ?an sugge/ive ( ! progress & decl9e ?r\gh :i* ! e>?'s inhabitants h pass$4 ,rocks ( e p]iod except probably ! ,silurian are kn[n to h be5 deposit$ some:]e 9 ! ,colorado area1 al?\gh 9 mo/ cases ! record = ea* p]iod is f> f complete4 ,=mations are too num]\s & too v>i$ locally to be %[n on a *>t ( ?is type4 ,,! ,,geological ,,section ,9 ! /udy ( fossils !re are two important field aids usually available4 ,= any locality !re %\ld be a geological map & a section %[+ ! sequ5ce & "* ( ! /rata4 ,on a small-scale map _m ( ! local details h to be omitt$1 b ! position ( ! l>g] exposures is indicat$ &1 ) ?is in=mation at h&1 ! fossil-be>+ /rata may be locat$ ) ! help ( a geological section4 ,! latt] is frequ5tly obta9$ f te*nical reports publi%$ by ,/ate & ,national ,geological ,surveys4 ,frequ5tly1 h[ev]1 x is possible to obta9 only a g5]al plan = a giv5 locality1 & a great deal ( lit]ature may h to be scann$ 9 ord] to get t4 ,excell5t geological maps ( ,colorado h be5 publi%$ by ! ,colorado ,geological ,survey & ! ,unit$ ,/ates ,geological ,survey4 ,x (t5 happ5s t a =mation is n :]e we expect to f9d x1 ?is be+ due to sev]al possible factors4 ,! s$im5ts may n h be5 deposit$ !re1 or !y may h be5 remov$ by erosion4 ,:]e ! /ructure has be5 di/urb$ by fold+ & fault+1 a multitude ( complications is introduc$4 ,! expect$ sequ5ce is sometimes inv]t$ & repeat$ ?r\gh a s]ies ( folds4 ,=mations also may be mov$ miles out ( place by fault+4 ,bo? ?ickness & "* ( s$im5ts may v>y consid]ably )9 a =mation4 ,9 "s regions ! geology is v simple1 9 o!rs extremely difficult to und]/&4 ,illu/ration3 ,,=mations ( ! ,,d5v]-,,foo?ills ,,region ,a ,,g5]aliz$ ,,section ,,%[+ ,,"s ,,( ,,! ,,surface ,,features ,,r$ ,,b$s ,,hogbacks ,,table ,,m\nta9 ,,d5v] ,,di/rict ,,region ,,( ,,m\nta9-,,mak+ ,,uplift ,=mations bord]+ ! m\nta9s h be5 b5t into upright positions4 ,,p]iods ,,rec5t ,,plei/oc5e ,,plioc5e ,,mioc5e ,,oligoc5e ,,eoc5e ,,cretace\s ,,?ickness ,,s(t ,,s&/ones ,,grits ,,clays ,,d5v] ,,arapahoe #bjjj ft4 ,,s&/ones1 ,,%ales ,,lignite ,,l>amie #ajjj ft4 ,,yell[i% ,,s&s ,,%ales ,,fox ,,hills #ajjj ft4 ,,s(t ,,d>k ,,gray ,,or ,,ru/y ,,%ale ,,pi]re #ejjj ft4 ,,lime/ones ,,%ales ,,niobr>a #ejj ft4 ,,d>k ,,%ales ,,lime ,,b5ton #djj ft4 ,,gray ,,or ,,buff ,,s&/ones ,,clays ,,dakota #cjj ft4 ,,%ales1 ,,s&/one ,,lime ,,morrison #bjj ft4 ,,jurassic ,,triassic ,,p]mian ,,deep-,,r$ ,,s&y ,,%ales1 ,,lime1 ,,gypsum ,,lyk9s #gjj ft4 ,,c>bonif]\s ,,massive ,,p9k ,,or ,,:ite ,,s&/one ,,lyons #bjj ft4 ,,r$ ,,or ,,br[n ,,s&/one ,,f\nta9 #aejj ft4 ,,conglom]ate ,,devonian ,,silurian ,,ordovician ,,cambrian ,,pre-,,cambrian ,,metamorphic ,,intrud$ ,,rocks ,,idaho ,,spr+s ,,s*i/1 ,,gneiss1 ,,qu>tzite 7,,"p7 ,,basem5t ,,rocks ( ,,igne\s ,,orig9 ,a g5]aliz$ section = ! we/]n "p ( ! ,d5v] ,bas9 is introduc$ "h = ! use ( local /ud5ts4 ,! =mations normally pres5t 9 ?is region are %[n 9 _! usual position4 ,!y are briefly describ$ on ! *>t1 & _! ?ickness is indicat$ by figures :i* may be reg>d$ z ne> ! maximum = ! di/rict4 ,! section w apply to mo/ ( ! foo?ills area betwe5 ,morrison & ,b\ld] ?\gh surface features & ?ickness ( b$s w v>y consid]ably f place to place4 ,c]ta9 ( ! =mations are kn[n to be fossil be>+1 o!rs b>r5 or ne>ly s4 ,:5 fossils are pres5t !y are usually re/rict$ to c]ta9 localities1 & ^! may be widely scatt]$4 ,! foll[+ rem>ks apply to ! possibilities = f9d+ fossils 9 ! =mations nam$4 ,d5v] & ,arapahoe4 ,leaf impressions ( palms1 f]ns1 & num]\s species ( well-kn[n trees & %rubs are common 9 _m localities4 ,petrifi$ wood is fairly abundant1 & a few scatt]$ bones ( reptiles & mammals h be5 f\nd4 ,! two =mations are treat$ z a unit because ! ,arapahoe is nei!r conspicu\s nor %>ply def9$4 ,d5v] b$s are well expos$ on ! slopes ( ,table ,m\nta9 at ,gold52 fossils1 h[ev]1 h be5 obta9$ f sev]al localities ne>] ! city ( ,d5v]1 notably f ! hills j we/ ( ,ov]l& ,p>k4 ,l>amie4 ,plant mat]ial is locally abundant1 pr9cipally ! leaves ( famili> decidu\s trees1 palms1 & f]ns4 ,_m ( ! clay pits be+ work$ ne> ,gold5 are 9 ?is =mation4 ,oy/]s & a few o!r mollusks may be f\nd 9 "s places4 ,fox ,hills4 ,bett] exposures ( ?is =mation are locat$ to ! nor? ( ,d5v]4 ,m>9e mollusks are mo/ frequ5tly f\nd4 ,pi]re4 ,9 addition to ! *>act]i/ic d>k %ales1 ?is =mation includes "s limy mat]ial & s&/one b$s1 bo? ( :i* are fossilif]\s 9 places4 ,two types ( m>9e mollusks are *>act]i/ic3 ,inoc]amus1 g5]ic "n = sev]al species ( clam-l bivalves readily id5tifi$ by conc5tric elevations :i* produce a rippl$ effect on ! %ell surfaces2 & ,baculites1 cephalopods ) /raight1 *amb]$ %ells :i* (t5 break at ! suture l9es1 :]e ! fossil is weak5$ by ! *amb] walls4 ,small oy/] %ells are fairly common also4 ,! =mation is to be f\nd "s di/ance to ! ea/ ( ! prom95t hogback :]e x wea!rs into smoo? surfaces 9 ! =m ( broad valleys & flats1 ) r\nd$ cont\rs on ! few elevations t may be pres5t4 ,x =ms a s(t1 flaky soil :5 dry1 is a /icky 8gumbo0 :5 wet4 ,! clay is g5]ally ( a r d>k grayi% color :5 fre%ly expos$ b x takes on a ru/y appe>ance aft] wea!r+4 ,at v>i\s levels !re are num]\s iron-cem5t$ concretions1 _m ( :i* conta9 fossil %ells4 ,illu/ration3 ,m>9e ,b$s ( ! ,b5ton ,=mation1 ,nor!a/]n ,colorado ,a /ream *annel has cut deeply into ! =mation1 uncov]+ & p>tly de/roy+ a plesiosaur skeleton :i* 0 f\nd at ! level :]e ! m5 are /&+4 ,illu/ration3 ,plesiosaur ,bones 9 ,place ,b5ton =mation4 ,surface rubble has be5 cle>$ away1 & sev]al v]tebrae are p>tially uncov]$ 9 ! area at ! "r ( ! hamm]4 ,niobr>a4 ,! =mation conta9s fossils r simil> to ^? ( ! ,pi]re4 ,%>k's tee? h be5 f\nd 9 "s ( ! l[] b$s4 ,lime/one is a prom95t feature1 (t5 =m+ a well def9$ ridge ne> ! foot ( ! ea/]n slope ( ! ma9 hogback4 ,! lime/ones commonly h a *alky "*4 ,b5ton4 ,! =mation is n especially productive 9 ?is region4 ,m>9e %ells are num]\s 9 "s localities1 & bones ( m>9e reptiles h be5 f\nd at v>i\s places4 ,z usually se51 x is almo/ entirely compos$ ( impure clay %ales1 v d>k1 br[ni%-gray to almo/ black1 & commonly int]b$d$ ) ?9 pat*es ( :ite b5tonite1 yell[ o*re1 gypsum1 & lime/one4 ,dakota4 ,?is =mation produces ! high hogback :i* is usually pres5t "s di/ance ea/ ( ! ,r$ ,rocks4 ,!re are g5]ally two or ?ree lay]s ( massive1 light-color$ s&/one sep>at$ by clays :i* are us$ ext5sively 9 ! mak+ ( bricks & pott]y4 ,leaf impressions & "s fi% scales are f\nd 9 ! clays & occasionally 9 ! s&/one4 ,! hogback is a good m>k] f :i* to locate o!r =mations1 because ( its prom95ce 9 ! foo?ills l&scape4 ,morrison4 ,good d9osaur mat]ial has be5 tak5 f ! ,canon ,city & ,morrison di/ricts4 ,! =mation is to be f\nd on ! l[] we/ slope ( ! ,dakota hogback4 ,x consi/s ( cont95tal deposits ( ! /ream & lake types4 ,!re is consid]able s&/one 9 ?is =mation & a little lime/one is to be f\nd "h & !re1 b ! mo/ *>act]i/ic feature is 9 ! %ales4 ,:5 fre%ly expos$1 ! %ales are delicately t9t$ ) gray1 gre51 & m>oon1 a bronze-gre5 be+ r prom95t4 ,?is =mation is highly v>iable 9 "*1 ) mu* ( ! clay (t5 buri$ "u ! valley floor4 ,9 addition to ! bones ( reptiles1 !re are plant fossils1 usually ( poor quality1 & fre%-wat] ga/ropods m or less abundant 9 "s localities4 ,lyk9s4 ,outcrops are n prom95t1 ow+ to ! small am\nt ( wea!r-resi/+ mat]ials4 ,! s&y clays are commonly ( a deep r$ color mottl$ ) spots ( light gray4 ,a :ite lime/one is sometimes pres5t ne> ! middle ( ^! deposits1 & gypsum b$s are includ$ locally4 ,! =mation is (t5 indicat$ only by r$ soil 9 ! depressions betwe5 ridges4 ,few fossils h be5 report$4 ,lyons4 ,?is =mation is usually prom95t z ! ea/]n wall ( ! uplift$ ,r$ ,rocks s]ies4 ,9 "s localities x =ms a ridge ( p9k or :ite s&/one di/9ctly sep>at$ f ! old] s$im5ts to ! we/4 ,v few fossils are f\nd4 ,f\nta94 ,exposures usually are br[n to r$ 9 color1 ?\gh sometimes a dirty :ite4 ,! prom95t rocks are r co>se s&/one1 commonly ) a gritty texture due to ! angul> "* ( ! s& or gravel f :i* !y 7 made4 ,^! are ! we/]nmo/ ( ! ,r$ ,b$s & ! olde/ ( ! uplift$ s$im5t>y rocks bord]+ ! foo?ills 9 mo/ ( our area4 ,fossils h be5 f\nd 9 ! =mation1 b x is practically b>r5 = ! t]ritory "h consid]$4 99 99 99 99 99 99 99 99 ,?is geological section also illu/rates a me?od ( dat+ cru/al movem5ts & ! bir? ( m\nta9 ranges1 = ! fold+ ( ! /rata along ! flanks ( ! ,rocky ,m\nta9s has a great deal ( significance 9 ?is connection4 ,! s$im5t>y lay]s 7 orig9ally deposit$ ov] mu* ( ! pres5t m\nta9 area 9 a horizontal position1 & only ^? =mations 9 exi/5ce at ! "t c\ld be di/ort$ by ! upheavals :i* produc$ ! new elevations4 ,( ! s]ies g5]ally involv$ 9 ! movem5t ! ,l>amie b$s are ! y\nge/4 ,s9ce ^! b$s _h n be5 =m$ until ne> ! close ( ! ,cretace\s p]iod x is to be assum$ t ! m\nta9s mu/ be ( m rec5t date1 y\ng] ?an ! topmo/ ( ! de=m$ b$s & at lea/ z old z ! l[]mo/ ( ! undi/urb$ =mations ov]ly+ !m4 ,"s di/urbance is evid5t also 9 ! ,arapahoe & ,d5v] b$s :i* ov]lie ! ,l>amie1 b ?is is believ$ to h occurr$ sometime aft] ! occasion ( ! fir/ great uplift4 ,volcanic mat]ials 9 ^! b$s lead to ! belief t ! s$im5ts 7 deposit$ dur+ a p]iod ( volcanic activity br\ght on by ! cru/al fold+ :i* t]m9at$ ! ,mesozoic era4 ,h5ce ! conclusion arises t ! age ( ! ,d5v] & ,arapahoe b$s mu/ co9cide closely ) "s ( ! e>li] /ages 9 ! hi/ory ( ! m\nta9 sy/em4 ,?is int]val is (t5 ref]r$ to z ,po/-,l>amie "t4 ,,be=e ,,! ,,age ,,( ,,reptiles ,,! ,,pre-,,cambrian ,,complex ,! rocks ( ,pre-,cambrian "t h be5 buri$ deeply "u ! accumulation ( y\ng] s$im5ts1 & ! result+ pressure 9 _m places has be5 trem5d\s4 ,9 addition to ! effects ( pressure !re also is record$ 9 ^! anci5t =mations ! repeat$ movem5ts ( ! mat]ials s9ce !y 7 fir/ deposit$4 ,v]tical & side adju/m5ts ( p>ts1 ) relation to o!r p>ts1 h di/ort$ ! orig9al arrangem5t ( ! rock p>ticles to su* an ext5t t ord9>y fossils w\ld ev5tually become unrecognizable4 ,^! cru%+1 gr9d+1 & knead+ =ces work+ ?r\gh millions ( ye>s alone w\ld acc\nt = ! abs5ce ( fossils f ! old] deposits4 ,frequ5tly ! rocks h become s *ang$ 9 =m t _! orig9al "* c only be conjectur$1 & because ( ?is *ange !y are kn[n z metamorphic rocks4 ,a few b$s ( ,ar*eozoic age rema9 9 ne>ly _! orig9al condition1 b !y are ei!r )\t fossils or !y h produc$ v que/ionable & unsatisfactory specim5s4 ,! exi/5ce ( life dur+ ^! e>ly /ages ( e>? hi/ory is indicat$ l>gely by *emical r ?an fossil evid5ce4 ,mu* ( ! anci5t lime/one has be5 conv]t$ into m>ble1 b x is n unreasonable to believe t plants & animals 7 in/rum5tal 9 ! production ( ?is type ( rock z !y are today4 ,c]ta9 v>ieties ( iron ore deposits are n[ be+ built up by ! aid ( plants1 & simil> ores 9 ! anci5t rocks may h _h a l orig94 ,! pres5ce ( great quantities ( c>bon1 9 ! =m ( graphite1 may be reg>d$ also z a sign ( life1 = ?is sub/ance is accumulat$ on a l>ge scale by liv+ plants1 & may be reta9$ 9 a solid =m aft] ! p>tial decay ( ! plant tissues4 ,s f> z ! direct evid5ce goes1 !re is no sign ( any creature ( l>ge size or ( su* complicat$ /ructure z ! common plants & animals ( today4 ,! *emi/ry ( ! m9]al deposits is n entirely conv9c+ z to ! pres5ce ( life1 b x is reg>d$ z highly probable t microscopic1 s+le-cell$ plants & animals1 comp>able to mod]n algae & protozoa1 7 9 exi/5ce dur+ ,ar*ean "t4 ,?r\gh\t lat] eras !re is unmi/akable evid5ce ( gradual developm5t f simpl] to m elaborate life-=ms & ! ,ar*eozoic is commonly reg>d$ z a "t ( prep>ation dur+ :i* simple organisms ( "s k9d 7 becom+ adapt$ to e>ly conditions :i* c\ld n support life on a high] plane4 ,! importance ( ! "w done by su* l[ly creatures 9 ! prep>ation ( suitable environm5ts = m advanc$ modes ( liv+ is ov]look$ almo/ entirely4 ,dur+ ! next era1 ! ,prot]ozoic1 ! record ( life becomes some:at cle>]4 ,fossils are h>dly to be reg>d$ z abundant b !re 7 sev]al well-def9$ types ( animals :i* left %ells & o!r p>ts compos$ ( m9]al matt]4 ,among ^! may be m5tion$ ! ,radiol>ia1 ,=am9if]a1 ,bryozoa1 & ,sponges4 ,radiol>ia produc$ delicate1 (t5 lace-l %ells ( _m patt]ns adorn$ ) ! radiat+ filam5ts or sp9es :i* h sugge/$ ! "n = ?is gr\p4 ,=am9if]a produc$ m9ute %ells1 sometimes _m *amb]$1 & (t5 be>+ a confus+ resemblance to ! "w ( snails4 ,common *alk is compos$ almo/ entirely ( su* %ells & fragm5ts ( !m4 ,sponges & ,bryozoa are animals ( slightly high] organization4 ,!y are _m-cell$ in/ead ( "o-cell$ & ! cells h special "w to p]=m1 :i* is a mo/ important /ep 9 ! direction ( ! specialization :i* *>act]izes ! /ructural & life patt]n ( lat] arrivals4 ,! ,bryozoa liv$ 9 moss-l colonies :i* h be5 important rock-mak]s2 ! fossil =ms be> "s resemblance to corals4 ,sponges are too well kn[n to require description al?\gh ! famili> article ( comm]ce is m]ely ! framework ( once-liv+ animals4 ,!y repres5t ! e>lie/ organization ( true animal bodies ev5 ?\gh 9 appe>ance !y may h a resemblance to plants4 ,actual plants ( ?is era 7 ( ! algae class1 aquatic 9 habit z 7 _! animal neighbors1 ! fir/ to leave a record 9 ! =m ( fossils4 ,?is record1 obscure & di/ort$1 has long be5 a s\rce ( p]plexity to inve/igators4 ,)\t well-def9$ floras & faunas to guide !m1 & ) rocks frequ5tly 9 *aotic relation%ips1 e>ly geologi/s 7 cont5t to reg>d x all z a 8,pre-,cambrian complex40 ,rec5t /udies h contribut$ a great deal ( in=mation n available "s ye>s ago4 ,x is q possible t m advanc$ types ( life 7 9 abundance be=e ! close ( ! second era1 b mat]ial on :i* to base s\nd op9ion is /ill sc>ce4 ,rocks ( ,pre-,cambrian age are pl5tiful 9 ! foo?ills region we/ ( ,d5v]4 ,! s*i/s1 gneisses1 & qu>tzites expos$ = "s miles imm$iately beyond ! r$-b$s are "p ( ?is great complex4 ,! ,idaho ,spr+s =mation is kn[n to be "o ( ! olde/ 9 ?is di/rict1 al?\gh its exact age has n be5 det]m9$4 ,o!r =mations are recogniz$ among ! metamorphic rocks ( ! region b none has contribut$ to our k ( e>ly life4 ,,cambrian ,,life ,!re c be no mi/ake z to ! prolific developm5t ( life 9 ,cambrian seas1 = fossils ( ?is age are to be f\nd 9 _m p>ts ( ! _w1 :]e anci5t sea bottoms n[ =m "p ( ! l& surface4 ,inv]tebrate animals appe> to h made mu* progress1 b plants 7 ei!r sc>ce or too small & delicate to be productive ( fossils4 ,x is probable1 h[ev]1 t seawe$s & o!r algae 7 fl\ri%+ along ) ! inv]tebrates1 because animal life is directly or indirectly dep5d5t on ! exi/5ce ( plants4 ,! latt] su/a9 !mselves by tak+ c>bon & nitrog5 f air1 wat]1 & soil1 b animals mu/ obta9 _! requirem5ts by eat+ plants or eat+ ea* o!r4 ,!y _c obta9 :at !y ne$ f ! inorganic _w )\t ?is help f ! vegetable k+dom4 ,"o gr\p ( animals /&s out prom95tly above all its contempor>ies4 ,kn[n z ! trilobites !y 7 by f> ! mo/ di/+ui%$ & mo/ *>act]i/ic ( ,cambrian inv]tebrates4 ,trilobites inhabit$ ! w>m] seas ( ?is p]iod & sev]al lat] ones1 b 7 ext9ct by ! end ( ! ,paleozoic era4 ,hundr$s ( species h be5 describ$1 mo/ ( !m "u f\r in*es 9 l5g?4 ,well-kn[n di/ant relatives n[ liv+ are ! %rimps1 & o!r cru/aceans4 ,! "n ,trilobite has ref]5ce to ! ?ree lobes :i* are app>5t 9 ! =m ( ! upp] surface1 ! c5tral lobe =m+ a broad ridge ext5d+ along ! back4 ,b5ea? ! out] lobes on ea* side !re 01 dur+ life1 a r[ ( %ort1 jo9t$ legs us$ = swimm+ & walk+1 b ^! delicate app5dages are seldom pres]v$ 9 ! fossils4 ,second 9 importance among ! animals ( ! p]iod 7 ! bra*iopods or lamp-%ells1 n true mollusks al?\gh !y 7 provid$ ) simil> %ells compos$ ( calcium phosphate or calcium c>bonate4 ,%ells are ( two p>ts 7bivalv$7 z 9 ! case ( clams1 b ! valves are above & b5ea? ! body in/ead ( on ! "r & left sides1 :i* is ! arrangem5t among mollusks4 ,al?\gh abundant z individuals1 !re 7 only a few species dur+ ! e>li] "p ( ! p]iod2 ! numb] ( species increas$1 h[ev]1 & ! race became v p]si/5t4 ,ab\t sev5 ?\s& species h be5 describ$1 & ! race is n yet ext9ct al?\gh ! numb] ( liv+ species is relatively small4 ,cambrian life evid5tly includ$ repres5tatives ( all ! great divisions ( inv]tebrates2 sponges1 jelly-fi%es1 worms1 & primitive corals h be5 report$4 ,at ! end ( ! p]iod !re 0 an elaborate molluscan fauna4 ,! clos+ ( ! p]iod 9 ,nor? ,am]ica 0 app>5tly a g5tle elevation ( cont95tal areas & a consequ5t )drawal ( ! sea4 ,illu/ration3 ,inv]tebrate ,fossils ,only a few prom95t types h be5 select$ f ?\s&s ( inv]tebrates kn[n to zoologi/s4 ,! =ms illu/rat$ are ( frequ5t occurr5ce z fossils4 ,,cr9oids ,,cephalopods ,coil$ types ,ammonite ,scaphite ,/raight-%ell type ,baculite ,,trilobite ,,bra*iopods ,,bivalves ,inoc]amus ,oy/] ,,ga/ropods ,snail-l ,univalves ,,protozoa ,,unicellul> ,,=ms ,radiol>ia 7,microscopic7 ,fusul9a lime/one ,=am9if]a 7,enl>g$7 ,,multicellul> ,,=ms ,cup coral ,reef coral ,sponge ,bryozoa ,,! ,,ordovician ,,record ,ext5sive l& areas mu/ h subsid$ aga9 e>ly 9 ! ,ordovician p]iod = m>9e s$im5ts 7 laid d[n ov] a l>ge "p ( ! ,nor? ,am]ican int]ior1 & ?ree epo*s or subdivisions ( ! p]iod h be5 bas$ on z _m invasions ( ! sea4 ,9 ^! anci5t deposits ! record ( life cont9ues to %[ new =ms4 ,no?+ ( a v spectacul> sort is record$ o!r ?an a great increase 9 ! numb] ( species among types t 7 e/abli%$ 9 e>li] p]iods4 ,trilobites 7 at _! be/1 bra*iopods cont9u$ to fl\ri%1 & ! mollusks made new progress1 especially ! cephalopods1 a gr\p :i* includes our cuttle fi%es & squids4 ,"s ( ^! pr$atory creatures atta9$ l>ge size & 7 no d\bt ma/]s ( ! sea4 ,typical =ms 7 provid$ ) tap]+ *amb]$ %ells t occasionally rea*$ a l5g? ( twelve or m feet4 ,mo/ ( ! %ells 7 /raight & trumpet-l or b slightly curv$4 ,"s 7 closely coil$ & 9 ?is respect m l ! well-kn[n nautilus n[ 9 exi/5ce4 ,! bryozoans became v common 9 ! lat] "p ( ! p]iod & corals made slight advances4 ,some:at ( a novelty at ?is "t 7 ! cr9oids1 commonly kn[n z 8/one lilies0 al?\gh n plants at all4 ,!y h be5 describ$ z />fi%es ) back turn$ d[nw>d & a ?ick /em atta*$ b5ea?4 ,:]e !y liv$ 9 great abundance ! lime/one deposits may consi/ almo/ entirely ( _! /ems4 ,cr9oids cont9u$ to produce a v>iety ( =ms ?r\gh\t sev]al ( ! succe$+ p]iods4 ,! bra*iopods 7 commone/ ( all animals repres5t+ ?is p]iod1 h[ev]1 & _! wide di/ribution1 toge!r ) _! kn[n pref]5ce = w>m wat]s1 is tak5 to be an indication ( mild temp]atures prevail+ ov] a l>ge portion ( ! e>?4 ,l& plants are indicat$ by spore-be>+ =ms relat$ to ! f]ns & mosses4 ,impressions ( su* plants h be5 f\nd 9 ,europe b1 s9ce mo/ ( ! kn[n rocks ( ?is age 7 =m$ 9 seas1 ! m>9e algae are m abundant z fossils4 ,9 ! ,colorado area1 rocks ( ,ordovician "t are expos$ only 9 m\nta9\s areas :]e !y h be5 lift$ high above _! orig9al levels4 ,!y are n especially ri* 9 fossils al?\gh !y h produc$ "s fi% rema9s :i* are ( int]e/ 9 t !y sugge/ an age ( v]tebrates :i* is j ahead4 ,,silurian ,,ev5ts ,s9ce l& floras & faunas _h n yet become conspicu\s ! fossil record = ?is p]iod is limit$ to ^? areas :i* 7 invad$ by ! sea4 ,app>5tly !re 0 no su* invasion ( ! pres5t ,colorado region1 = rocks ( ?is age are n 9 evid5ce4 ,if !y exi/ at all !y are re/rict$ to localiz$ di/ricts :i* are deeply buri$ "u s$im5ts ( lat] p]iods4 ,!re may h be5 no ,silurian deposition 9 ?is area1 or su* rocks may h be5 produc$ only to be de/roy$ by elevation & consequ5t subjection to wea!r+ & erosion dur+ a long int]val ( "t1 9 :i* !y 7 completely remov$4 ,9 ! region ( ! ,colorado ,rockies !re is no evid5ce ( return+ seas until late ,devonian "t4 ,9 o!r p>ts ( ! _w1 h[ev]1 !re 0 ext5sive deposition ( rock-mak+ s$im5ts 9 seas :i* 7 inhabit$ by algae & inv]tebrates ( ! types previ\sly describ$4 ,among ! common animals ( ! "t !re 7 /ill num]\s species ( bra*iopods1 trilobites1 corals1 cr9oids1 & bryozoans4 ,9 addition to ! primitive cone-%ap$1 cup corals !re 7 sev]al advanc$ types b ! habit ( build+ l>ge reefs 0 n yet e/abli%$4 8,sea scorpions10 really l>ge cru/aceans1 fl\ri%$ dur+ ,silurian "t1 & late 9 ! p]iod !re appe>$ a race ( true scorpions :i* liv$ on dry l& or betwe5 high & l[ tides along ! sea%ore4 ,^! 7 small] & mu* l mod]n desc5dants b probably !y did n w&] f> f ! ocean %ores :]e an abundance ( food 0 available4 ,^! little scorpions1 ! l>ge/ measur+ only two & a half in*es 9 l5g?1 are ! olde/ air-brea?+ l& animals ( ! fossil record4 ,x 0 n until ! p]iod 0 well advanc$ t fi%es became num]\s1 & mu* ( our k ( ! beg9n+ ( an 8,age ( ,fi%es0 has be5 obta9$ f ,european fossils4 ,al?\gh fi%es are class$ ) ! v]tebrate or backbon$ animals !re are l>ge gr\ps :i* d n h bony skeletons b are provid$ in/ead ) a simple framework ( c>tilage4 ,among ! e>li] & m primitive types 7 ! o/racod]ms or bony-sk9n$ fi%es ) no int]nal bones & only a small am\nt ( bony sub/ance 9 ! armor-l plates & scales :i* cov]$ ! =w>d portion ( ! body4 ,! o/racod]ms comprise a small gr\p ( fi%es ab\t :i* v little is kn[n4 ,!y appe> to h be5 inhabitants ( fre%-wat] /reams z well z lagoons bord]+ ! seas1 & may h be5 relat$ to ! small %>ks ( ! "t4 ,!y liv$ dur+ ! ,ordovician1 ,silurian1 & ,devonian p]iods1 & left no desc5dants n[ recogniz$ among liv+ creatures4 ,a mu* l>g] type ( armor$ fi%es is kn[n z ! ar?rodires1 a "n :i* ref]s to a po9t$ neck & an arrangem5t ( ! armor plates to p]mit a movem5t ( ! head4 ,^! 7 ! mo/ f]oci\s fi%es ( ! ,silurian & ,devonian seas1 "s ( !m rea*+ a l5g? ( tw5ty feet ?\gh mo/ 7 mu* small]4 ,_! jaws 7 provid$ ) =midable %e>+ & cru%+ plates in/ead ( tee?4 ,,devonian ,,progress ,! ,devonian is "o ( ! mo/ out/&+ ( all p]iods f ! viewpo9t ( life developm5t4 ,dom9ance ( ! fi%es is its greate/ a*ievem5t1 ! inv]tebrates rema9+ ab\t z !y 7 & ! high] v]tebrates b>ely 9 evid5ce1 b life on a l>ge scale 0 no long] conf9$ to ! seas4 ,fre%-wat] fi%es became prom95t & l& plants well e/abli%$4 ,! fir/ =e/s appe>$1 ) f]n-l plants pr$om9at+ al?\gh woody trees ( sev]al types & consid]able size 7 includ$4 ,x is q possible t ext5sive l& areas _h be5 well suppli$ ) vegetation dur+ e>li] times1 b ! delicate tissues ( plants are f> less likely to be pres]v$ ?an ! limy p>ts ( animals4 ,! fossil record1 !re=e1 _c be expect$ to reveal m ?an a sugge/ion ( ! progress made at ?is level ( liv+4 ,! /ory ( plant life becomes mu* cle>] 9 ! next p]iod :5 conditions 7 m favorable = ! production & pres]vation ( plant fossils4 ,l& animals ( ! "t are almo/ unkn[n4 ,a few snails & scorpions h be5 f\nd1 & "s footpr9ts made by e>ly amphibians4 ,insects probably 7 9 exi/5ce al?\gh ! evid5ce is n q cle> on ?is po9t4 ,! increas+ numb] ( fre%-wat] fi%es1 h[ev]1 may be reg>d$ z a sure indication t inl& conditions 7 becom+ m favorable = plant & animal inhabitants ( all k9ds4 ,! ext5t ( developm5t among ! fi%es _c be accurately indicat$ by nam+ a few types1 = x is ma9ly 9 ! numb] ( species & g5]a )9 ! l>g] gr\ps t progress is se54 ,9 g5]al x may be /at$ t ! fi%es ( ! p]iod _h n yet acquir$ ! bony skeleton & typical =m ( famili> mod]n species4 ,skeletons 7 ( c>tilage1 p>tly h>d5$ 9 "s in/ances by lime4 ,armor plates 7 cu/om>y ) c]ta9 races b 7 n pres5t among all fi%es4 ,nei!r 7 ^! armor$ =ms exceptionally l>ge1 z comp>$ ) liv+ %>ks4 ,al?\gh occasional giants appe>$1 ! majority 7 small4 ,_m 7 sluggi% creatures ) poorly-develop$ jaws1 liv+ z scav5g]s on sea & /ream bottoms4 ,tail f9s 7 usually unbalanc$ z 9 ! %>ks1 or po9t$ & r\nd$ r ?an ev5ly =k$4 ,illu/ration3 ,mod]niz$ ,types ( ,fi%es f ,eoc5e ,%ales ( ,s\?we/]n ,wyom+ ,! great tribe ( true bony fi%es1 su* z ! cod & p]*1 :i* includes m ?an n9ety p]c5t ( ! fi%es liv+ today1 0 n yet 9 exi/5ce4 ,ab\t "o-?ird ( ! _m k9ds ( fi%es !n liv+ 7 relat$ to ! %>ks1 a gr\p :i* is relatively insignificant 9 rec5t ye>s4 ,ne>ly "o-f\r? ( ! total belong$ to a tribe ( enamel-scal$ fi%es1 n[ repres5t$ only by a few /urgeon & g>-pike4 ,lung fi%es h nev] be5 a l>ge gr\p b x is notewor?y t !y h _h exi/5ce s9ce ,middle ,devonian "t4 ,liv+ memb]s ( ! race1 inhabitants ( ,africa & ,s\? ,am]ica1 make a practice ( burr[+ into ! mud ( /ream *annels dur+ dry seasons & are provid$ ) lungs :i* enable !m to brea! air 9 ! mann] ( high] v]tebrates4 ,!y survive ! complete dry+-up ( ! /reams & live = mon?s )\t wat]4 ,o!r =ms1 ) less developm5t ( lungs1 frequ5t /agnant pools & come to ! surface occasionally = a brea? ( air4 ,all are provid$ ) gills also1 :i* enables !m to obta9 _! oxyg5 z o!r fi%es d4 ,!y are believ$ to be a connect+ l9k betwe5 ! fi%es & ! e>ly amphibians4 ,m accurately1 p]haps1 !y %\ld be reg>d$ z hold+ an int]m$iate position )\t be+ directly ance/ral to any high] type ( v]tebrate animal4 ,/ill dom9ant among ! inv]tebrates 7 ! bra*iopods1 on ! :ole av]ag+ a little l>g] 9 size1 & o!rwise indicat+ cong5ial times = t type ( organism4 ,!y rea*$ ! peak ( _! developm5t dur+ ?is p]iod4 ,trilobites 7 decl9+ al?\gh a few new & /rangely ornam5t$ v>ieties made a brief appe>ance4 ,cr9oids app>5tly f\nd liv+ conditions less favorable dur+ ,devonian "t1 b 9 a lat] era !y aga9 became prom95t4 ,corals 7 favor$ only at times & 9 c]ta9 localities4 ,along ) ! cr9oids !y appe> to h suff]$ f ! pres5ce ( an unusual am\nt ( mud 9 ! wat]s ( _! cu/om>y habitats4 ,bo? _h a pref]5ce = cle> wat] z indicat$ by ! abs5ce ( fossils f lime/ones conta9+ m ?an a v small p]c5tage ( muddy s$im5ts4 ,cru/aceans1 simil> to ! sea-scorpions & bett] kn[n z eurypt]ids1 became prom95t among fre%-wat] animals4 ,"s 7 unusually l>ge = creatures ( ?is class1 l5g?s ( sev]al feet be+ record$ f fragm5ts4 ,ga/ropod mollusks came into prom95ce 9 localities :]e liv+ conditions 7 favorable4 ,bivalves cont9u$ to ?rive b ! cephalopods _h a r meag] developm5t consid]+ ! heights !y 7 to a*ieve 9 subsequ5t p]iods4 ,9 we/]n ,nor? ,am]ica ! l>ge expanse ( t]ritory kn[n z ! ,great ,pla9s 0 evid5tly well above sea level dur+ ?is entire p]iod1 = no b$s ( ?is age are f\nd 9 ea/]n ,colorado4 ,we/ ( ! ,front ,range1 h[ev]1 !re 0 "s deposition ( m>9e s$im5ts dur+ late ,devonian "t4 ,=mations ( ?is age are expos$ ne> ,salida & ,gl5wood ,spr+s1 on ! ,:ite ,riv] ,plateau1 & 9 ! ,san ,juan region4 ,! ,c>bonif]\s p]iod gets its "n f ! va/ deposits ( coal :i* 7 develop$ dur+ t "t 9 _m p>ts ( ! nor!rn hemisph]e4 ,depress$ l& surfaces bord]+ ! cont95ts1 & ext5d+ well into ! int]ior ( pres5t b\nd>ies1 support$ d5se gr[?s ( vegetation & provid$ ! swampy conditions mo/ favorable to coal production4 ,v>ieties ( plants :i* are n[ ( small size & l[ly position 9 ! botanical _w acquir$ ! proportions ( l>ge trees4 ,,c>bonif]\s ,,=e/s ,be/-kn[n fossils ( ! p]iod are c>boniz$ portions ( ! l>g] trees1 & impressions left 9 ! muds & s&s ( anci5t bogs4 ,=e/ trees ( sev]al k9ds rea*$ ! height ( a hundr$ feet1 ) a trunk diamet] ( two to six feet4 ,?is size (t5 is exce$$ 9 mod]n =e/s1 b by trees ( an entirely diff]5t type4 ,consid]+ ! am\nt ( developm5t among ! plants ( e>li] p]iods1 ,c>bonif]\s =e/s provide an out/&+ spectacle ( advanc+ life4 ,q common among ! l>g] trees 7 two v>ieties ( club-mosses1 also kn[n z scale trees4 ,!y 7 cone-be>+ ev]gre5s ) only slight resemblance to mod]n conif]s4 ,in/ead ( se$s !y produc$ spores1 a me?od ( reproduction :i* is practic$ among f]ns4 ,! trunks 7 m>k$ f bottom to top ) uni=m patt]ns ( cu%ions & sc>s indicat+ ! po9ts at :i* leaves 7 atta*$ dur+ ! e>li] /ages ( gr[?4 ,9 ! ,lepidod5drons ! r[s ( scale-l cu%ions w9d spirally upw>d :ile among ! ,sigill>ia !re is a v]tical arrangem5t ( leaf-sc>s :i* resemble ! impr9ts ( a seal1 ^! impressions be+ 9 /raight & p>allel r[s on a surface :i* may be ei!r ribb$ or smoo?4 ,! leaves ( scale trees 7 /iff & sl5d]1 & arrang$ 9 grass-l tufts at ! top4 ,calamites1 relat$ to our horsetail ru%es1 7 some:at small] ?an ! scale trees4 ,_! trunks consi/$ ( a ?91 woody cyl9d] ) a pi?y int]ior1 & 7 m>k$ at int]vals by nodes :i* gave !m ! 8jo9t$0 appe>ance ( a bamboo /em4 ,leaves 7 arrang$ 9 circles ar\nd ! nodes ( ma9 /em or bran*es4 ,spore-be>+ cones appe>$ at ! tips ( ! /ems4 ,illu/ration3 ,prehi/oric ,plants ,"s ( ! l>g] & bett] kn[n plants ( pa/ ages are %[n z recon/ruct$ by arti/s4 ,f9] details ( ! recon/ructions (t5 h to be neglect$ because ( unc]ta9ties due to ! scatt]$ & fragm5t>y "* ( ! fossil record4 ,,leaf ,,impressions ,c>bonif]\s ,f]ns ,/rap-leaf ,conif] 7,cordaites7 ,,mod]niz$ ,,types ,sequoia ,cone & foliage ,mioc5e ,fossils 7,florissant ,%ales7 ,maple ,will[ ,eoc5e palm 7,d5v] ,b$s7 ,,horse ,,tail ,,ru%es ,re/oration 7,calamites7 ,fossils ,leaves & ,/em ,,cycads ,re/oration ,fossil ,trunk ,,club ,,mosses ,re/oration 7,sigill>ia7 ,fossils ,trunk ,impressions ,,scale ,,trees ,re/oration 7,lepidod5dron7 ,fossil ,leaf sc>s ,also includ$ among ! l>g] trees 7 ! ,cordaites or l>ge-leav$ ev]gre5s1 tall & sl5d]1 se$-be>+ b n true conif]s z yet4 ,leaves 7 /rap-%ap$ or grass-l1 ! l>g] ones hav+ a l5g? ( six feet & a wid? ( six in*es4 ,trunks 7 woody1 resembl+ p9e1 b ) a c5tral pi?4 ,! fl[]s 7 small & resembl$ catk9s 9 =m4 ,f]ns & f]nlike plants 7 s num]\s t ! p]iod has be5 kn[n z an age ( f]ns4 ,e>li] k ( ^! =e/s 0 bas$ on fossils ( a fragm5t>y "* f :i* an accurate association ( p>ts c\ld r>ely be obta9$4 ,a g5]al relation%ip ) ! f]ns 0 app>5t1 b c>eful /udy ( additional mat]ial has giv5 u a r diff]5t view ( ,c>bonif]\s plant life & we note a highly div]sifi$ array ( =ms ) _m sugge/ions ( mod]n t5d5cies4 ,! flora z a :ole may be reg>d$ z highly specializ$ = ! conditions :i* prevail$ at ! "t & 7 n to cont9ue ?r\gh subsequ5t p]iods4 ,w>m temp]atures & abundant moi/ure 7 ess5tial especially to spore-be>+ types1 & ! cold1 arid conditions ( ! next p]iod put an end to _m ( ! gr\ps1 or greatly r$uc$ _! prom95ce4 ,?is c\ld be reg>d$ equally well z an age ( insects1 = "s ( ^! inv]tebrates acquir$ ! greate/ size !y h ev] _h1 p>ticul>ly ! dragonflies ) a w+-spread ( m ?an two feet 9 "o ( ! l>ge/ fossils s f> discov]$4 ,cockroa*es numb]+ upw>ds ( five hundr$ species h be5 nam$4 ,?\gh l>ge !y are h>dly to be reg>d$ z giants1 l5g?s ( ?ree or f\r in*es be+ ab\t ! limit4 ,"s ( ! insect types ( today q evid5tly exi/$ among ! inhabitants ( ,c>bonif]\s =e/s1 b x is app>5t t !re 7 also "s antiquat$ =ms :i* may h desc5d$ f ! trilobites4 ,al?\gh "s au?orities reg>d ?is z ! p]iod 9 :i* insects orig9at$1 !re are o!rs :o ma9ta9 t def9ite beg9n+s are n e/abli%$ s readily on pres5t evid5ce4 ,spid]s are believ$ to h made _! appe>ance at ?is "t4 ,f\r-foot$ v]tebrates resembl+ salam&]s 7 prom95t animals ( ! ,c>bonif]\s swamps4 ,at fir/ adapt$ to a life 9 wat] & lat] to l& conditions1 !y are kn[n z amphibians1 ! "n be+ bas$ on ! ability to live 9 two diff]5t k9ds ( environm5t4 ,common liv+ repres5tatives ( ?is gr\p are ! toads & frogs1 b ^! tailless =ms are n kn[n among fossils ( ! ,paleozoic era & are almo/ unkn[n ?r\gh\t ! ,mesozoic4 ,! ,age ( ,amphibians1 z we apply t phrase1 0 def9itely n an age ( toads & frogs4 ,^! primitive l& animals 7 ( diff]5t types1 rang+ f mu* small] sizes up to ! l5g? ( a crocodile4 ,mo/ ( !m _h %ort legs1 & feet :i* 7 suitable = locomotion ^u l&1 b _m ( ! creatures probably sp5t mo/ ( _! lives 9 ! wat]4 ,tails 7 usually high & flatt5$ z if = swimm+1 sometimes long1 at o!r times greatly %ort5$ 9 proportion to ! body4 ,heads 7 g5]ally l>ge1 jaws long1 & m\?s wide4 ,be=e ! close ( ! p]iod true reptiles appe>1 b ?is race ( animals is de/9$ to make a m spectacul> advance ?an ! amphibians & w be discuss$ 9 connection ) ,mesozoic life4 ,! amphibians1 h[ev]1 are reg>d$ z be+ ! ance/ors ( ! reptiles z well z ! high] quadrup$s :i* foll[ !m4 ,al?\gh liv+ reptiles are readily di/+ui%$ f liv+ amphibians !re is a diff]5t situation ) reg>d to ^! primitive =ms1 = among ! fossils x becomes increas+ly difficult to sep>ate ! two gr\ps z new mat]ial is inve/igat$4 ,inv]tebrates _h _! ups & d[ns dur+ ! p]iod4 ,trilobites became sc>ce1 & bra*iopods = a "t 7 ! mo/ abundant ( ! %ell$ animals b lat] decl9$ rapidly4 ,9 favorable localities ! cr9oids e/abli%$ a wond]ful record = new species be=e ! p]iod _h advanc$ v f>4 ,hundr$s ( species ( ,c>bonif]\s inv]tebrates are kn[n1 & 9 _m ( ! rocks ( ! p]iod !y are ! only fossils to be f\nd1 = ! v]tebrates 7 /ill unable to v5ture f> f ! swampy di/ricts1 & mu* inl& t]ritory 0 too well dra9$ to support ei!r ! floras or faunas !n exi/+4 ,9 ! ,colorado area !re are bo? m>9e & cont95tal =mations b ! great coal-mak+ =e/s & _! inhabitants 7 limit$ to o!r localities4 ,z a consequ5ce ?is region is n fam\s = ,c>bonif]\s fossils4 ,,p]mian ,,h>d%ips ,= a "t !re 0 no great *ange 9 ,nor? ,am]ica foll[+ ! op5+ ( ! ,p]mian4 ,!n began a s]ies ( m\nta9-mak+ movem5ts & cont95tal uplifts :i* dra9$ ! swamps1 lakes1 & inl& seas4 ,) ! pass+ ( ! vegetation :i* _h e/abli%$ itself 9 & ar\nd ^! areas mu* ( ! animal life foll[$4 ,x is probable t a consid]able proportion ( ! m>9e life surviv$1 mu* m ?an is indicat$ by ! fossil record1 b ! rec$+ seas c>ri$ ! survivors into t]ritory :i* is n[ inaccessible to fossil hunt]s4 ,aft] ,middle ,p]mian "t ! climate ev]y:]e seems to h be5 cold & dry4 ,by ! end ( ! p]iod !re _h be5 accompli%$ m geographical *ange ?r\gh\t ! _w ?an at any "t s9ce ! beg9n+ ( ! ,paleozoic era4 ,traces ( ! cru/al movem5ts :i* produc$ new m\nta9 ranges c be foll[$ 9 ,europe1 ,asia1 & ,nor? ,am]ica4 ,! ,appala*ian region 0 rais$ to a great height1 possibly 9 excess ( ?ree miles4 ,a major di/urbance ( ?is "* is kn[n among geologi/s z a revolution1 & to ?is p>ticul> "o ! "n 8,appala*ian ,revolution0 has be5 giv54 ,! elevation ( cont95ts necess>ily *anges _! coa/ l9es4 ,?is1 9 turn1 influ5ces ocean curr5ts :i* h an important be>+ on climatic conditions4 ,9 addition to ?is1 ! elevation ( m\nta9 sy/ems n only re>ranges ! di/ribution ( hot & cold w9ds ov] ! l& areas b x may produce b>ri]s to ! migrations ( floras & faunas1 conf9+ !m to areas 9 :i* x is no long] possible to live4 ,:5 ! effect ^u plants & animals is consid]$1 x is easi] to und]/& :y a l9e is drawn across ! geological "t *>t at su* a po9t & an era ( prehi/ory is reg>d$ z clos$4 ,dur+ ! ,p]mian p]iod !re 0 record$ 9 ! rocks m widespread glacial action ?an ev] be=e or s9ce4 ,) less inl& wat] to provide ! necess>y evaporation !re 0 a m>k$ decrease 9 ra9fall1 & arid or semi-arid conditions replac$ ! hospitable climate t _h be5 su* an important factor 9 ! prolific life ( ! ,c>bonif]\s4 ,! /ruggle = exi/5ce became int5se1 b h>di] types ( plants & animals1 ) great] ability to adapt !mselves to adv]se conditions1 e/abli%$ !mselves "h & !re1 z ance/ral =ms became ext9ct4 ,mo/ ( ! l>ge spore-be>+ trees di$ out & se$-produc+ v>ieties began to acquire prom95ce1 among !m ! conif]\s ev]gre5s4 ,f]ns1 h[ev]1 prov$ _! adaptability by produc+ "s new =ms :i* became prom95t 9 ,p]mian floras4 ,! prehi/oric amphibians h be5 divid$ into ?ree ord]s1 "o ( :i* includes all ! l>g] =ms4 ,?is gr\p1 kn[n z ! labyr9?odonts1 cont9u$ on ?r\gh ,p]mian "t b began to %[ backw>d t5d5cies1 ) dw9dl+ limbs & a return to life 9 ! wat]4 ,among ! l>g] l& v>ieties are typical fossils rang+ f ab\t fifte5 in*es to five feet 9 l5g?4 ,9 outw>d appe>ance !y diff]$ f ,c>bonif]\s amphibians4 ,"o ( ! o!r ord]s1 includ+ a great div]sity ( small] =ms1 became ext9ct dur+ ?is p]iod1 leav+ no kn[n desc5dants4 ,! ?ird ord] is reg>d$ z ! olde/1 & probably ! ance/ral gr\p f :i* ! mod]n newts & salam&]s orig9at$4 ,! mo/ successful ( ,p]mian l& animals 7 ! peculi> reptiles t le>n$ to live 9 dri] regions4 ,l ! horn$ toad & ,gila mon/] ( our arid s\?we/]n ,unit$ ,/ates1 ! l>g] ,p]mian reptiles 7 f\r-foot$ animals4 ,9 size & %ape !y 7 n greatly diff]5t f amphibians !n liv+4 ,an exception to ?is rule1 among "s ( !m1 is ! developm5t ( long1 bony sp9es above ! v]tebrae ( ! back4 ,a fairly common fossil ( ?is type1 f\nd 9 ,texas & kn[n z ,dimetrodon1 _h a total l5g? ( six feet1 ab\t half ( ?is be+ 9 ! tail4 ,! tips ( ! sp9es adorn+ ! back rea*$ a height ( ?ree feet or m & !re 0 probably a cov]+ ( sk9 ov] ^! bones1 :i* w\ld produce a sail-l /ructure or 8f90 ( l>ge size4 ,its use has n be5 expla9$ b x provides an easy "n = ^! odd creatures--! 8f9-back liz>ds40 ,rock deposits produc$ 9 arid regions usually h *>act]s :i* are n difficult to recognize4 ,gritty texture1 irregul> b$d+1 r$ color1 & gypsum are common features4 ,=mations ( ,p]mian age are to be f\nd 9 ,colorado b bett] fossil deposits h be5 discov]$ 9 ,kansas & ,texas4 ,illu/ration3 ,m>9e ,reptiles3 ,plesiosaur 7,l[] ,skeleton7 & ,mosasaur ,! ,mesozoic ,era produc$ _m types ( reptiles besides ! d9osaurs4 ,two ( ! m>9e =ms are %[n 9 ?is illu/ration1 bo? f ,cretace\s b$s ( ! we/]n ,unit$ ,/ates4 ,plesiosaurs 7 ! giants ( ! seas 9 _! "t1 l5g?s ( =ty to fifty feet be+ n uncommon4 ,a long flat tail provid$ locomotion = ! mosasaurs :]eas ! plesiosaurs resort$ to ! peculi> limb /ructures kn[n z flipp]s or paddles4 ,,! ,,age ,,( ,,reptiles ,! ,mesozoic1 or era ( middle life1 0 a long /ret* ( "t dur+ :i* !re 0 m>vel\s developm5t among ! reptiles4 ,_m /range types 7 produc$ & mo/ ( !m became ext9ct be=e ! end ( ! era4 ,! reptilian /ock bran*$ out 9 _m directions4 ,types em]g$ :i* diff]$ f "o ano!r s widely t _! mutual relation%ips h become obscure4 ,hide\s & fanta/ic creatures sugge/+ sea s]p5ts & dragons 7 worldwide 9 di/ribution4 ,reptiles ( ! air & seas acquir$ l>ge size & weird =ms1 b great] advances 7 made ^u l&4 ,! fly+ reptiles or pt]osaurs fl\ri%$ 9 ,jurassic times ) "s ( ! l>g] v>ieties surviv+ until ne> ! close ( ! ,cretace\s4 ,al?\gh ^! w+$ liz>ds 7 ! fir/ ( ! v]tebrates to fly !y are n to be confus$ ) birds4 ,!y 7 )\t fea!rs1 & ! e>li] =ms 7 provid$ ) long tails be>+ a flatt5$ rudd]-l tip4 ,"o ( ! be/ kn[n ( ?is type _h a l5g? ( ab\t eighte5 in*es4 ,its jaws 7 long & provid$ ) %>p tee?4 ,! w+s 7 membranes atta*$ to body & legs1 /ret*$ & manipulat$ by means ( greatly elongat$ f+]s4 ,9 lat] types !re 0 a r$uction 9 too? equipm5t & l5g? ( tail4 ,pt]anodon1 f\nd 9 ,kansas1 _h a w+ spread ( tw5ty-five feet1 a l>ge too?less beak1 a %ort body1 & a m]e /ub ( a tail4 ,x 0 "o ( ! la/ ( ^! w+$ mon/]s4 ,sev]al types ( m>9e reptiles appe>$ dur+ ?is era1 among !m ! plesiosaurs :i* fir/ appe>$ 9 ,triassic seas4 ,^! peculi> animals 7 s]p5t-l ) reg>d to ! "* ( head1 neck1 & tail1 b 9 o!r respects 7 q diff]5t1 ! %ort b>rel-%ap$ body be+ provid$ ) f\r l>ge paddles correspond+ to ! usual limbs ( quadrup$s4 ,fossil rema9s ( ^! animals are common 9 _m ,jurassic & ,cretace\s deposits1 "s ( ! l>ge/ exce$+ =ty feet 9 l5g?4 ,mosasaurs1 also m>9e c>nivores1 inhabit$ %all[ ,cretace\s seas ?r\gh\t ! _w & are especially abundant z fossils 9 ! ,kansas *alk b$s4 ,^! 7 elongat$ =ms ) a resemblance to salam&]s 9 "s respects b provid$ ) long po9t$ jaws & %>p tee?4 ,swimm+ 0 accompli%$ l>gely by ! tail ?\gh probably aid$ to "s ext5t by f\r webb$ paddles or flipp]s4 ,! i*?yosaurs 7 m fi%-l 9 con/ruction1 z ! "n implies4 ,! limbs 7 %ort & broad1 & !re 0 usually pres5t a well-develop$ tail-f9 z well z a l>ge f9 on ! back4 ,!y 7 especially abundant 9 ,jurassic "t4 ,fossils are fairly common 9 m>9e deposits ( we/]n ,nor? ,am]ica4 ,mosasaurs & i*?yosaurs 7 ab\t half z long z ! plesiosaurs4 ,,d9osaurs ,mo/ spectacul> ( ! prehi/oric reptiles 7 ! d9osaurs1 a l>ge gr\p ( animals v>y+ greatly z to size1 =m1 & habits4 ,!y 7 adapt$ = a life on l& ?\gh _m ( !m probably sp5t mu* ( _! "t p>tly subm]g$ 9 ! wat]s ( lakes & /reams4 ,!re is little t c be said ( ! gr\p z a :ole o!r ?an t all ( !m 7 reptiles4 ,fur!r ?an t x is necess>y to reg>d !m z belong+ to sev]al diff]5t subdivisions ( ! ,reptilia4 ,classification has be5 difficult & ! names us$ = ! v>i\s subdivisions are (t5 mislead+ to ! layman :o tries to und]/& ! t]m9ology4 ,ance/ral reptiles 7 five-to$ & five-f+]$ b among ! d9osaurs !re 7 _m dep>tures f ! /&>d =mula4 ,?ree or f\r ( ! digits 7 commonly well develop$1 ! o!rs :5 pres5t be+ %ort5$ or r$uc$ to m]e rudim5ts4 ,e>ly 9 ! hi/ory ( d9osaurs !re 0 a division ( ! /ock into two ma9 bran*es1 ea* ( :i* includes a v>iety ( types & sizes1 & is aga9 subdivid$4 ,! two ma9 gr\ps are be/ recogniz$ by ! con/ruction ( ! bony framework :i* comprises ! pelvic girdle or hip region ( ! skeleton4 ,9 ord] to avoid te*nical difficulties1 h[ev]1 ! rema9+ discussion ( ^! int]e/+ reptiles w be conf9$ to a few names & descriptions :i* s]ve to illu/rate r\ghly ! great am\nt ( v>iation t develop$ f ! comp>atively simple ance/ral patt]n4 ,! plan accord+ to :i* ! d9osaurs are usually classifi$ is b>ely sugge/$ by ! types describ$4 ,! meat-eat]s 7 active creatures provid$ ) p[]ful jaws & tee?4 ,!y 7 un>mor$1 mov$ ab\t on _! h9d feet1 & dur+ _! "t 7 ! mo/ highly advanc$ ( all animals4 ,tyrannosaurus ) a l5g? ( =ty-five feet or m1 & ,de9odon1 ne>ly z l>ge1 7 among ! greate/ ( ^!4 ,bo? liv$ 9 ! ,cretace\s p]iod4 ,_! tee? 7 simple b /rong1 knife-l1 curv$1 & f9ely s]rat$4 ,skulls 7 l>ge & ! =elimbs 7 r$uc$ almo/ to a /ate ( uselessness4 ,l>ge c>nivores liv$ also dur+ ,jurassic "t & ev5 z f> back z late ,triassic4 ,e>ly ,triassic =ms 7 ( small] size4 ,m primitive fle%-eat+ d9osaurs ( ! ,triassic & ,jurassic p]iods 7 delicately proportion$ & lightly built bip$s be>+ "s resemblance to birds4 ,/ru?iomimus1 :i* means o/ri*-resembl+1 0 ab\t ! size ( ! bird :i* provides ! "n4 ,x 0 sl5d] 9 ! limbs1 ?ree-to$1 long neck$1 long tail$4 ,! skull 0 small1 =elegs long = a bip$4 ,unlike mo/ d9osaurs x 0 too?less4 ,all ^! bird-l c>nivores 7 small z comp>$ ) o!r contempor>y =ms4 ,compsogna?us1 ( ,g]many1 & "o ( ! smalle/ ( all d9osaurs1 _h a l5g? ( less ?an ?ree feet1 includ+ ! long tail4 ,illu/ration3 ,"o ( ! ,l>ge ,jurassic ,d9osaurs 7,diplodocus longus7 ,?is magnific5t specim51 exhibit$ by ! ,d5v] ,museum ( ,natural ,hi/ory1 has a l5g? ( sev5ty-five feet six in*es4 ,two ye>s 7 requir$ to complete ! task ( remov+ ! bones f ! matrix rock & prep>+ !m = m\nt+4 ,diplodocus 0 "o ( _m l>ge reptiles :i* inhabit$ we/]n ,nor? ,am]ica a hundr$ & fifty million ye>s ago4 ,! skeleton 0 obta9$ f ! ,morrison b$s ( ea/]n ,utah4 ,! same =mation is expos$ 9 _m ,colorado localities1 includ+ ! foo?ills we/ ( ,d5v]1 :]e x acquir$ its "n f ! t[n ( ,morrison4 ,9 ,jurassic "t !re became prom95t a gr\p ( l>ge d9osaurs :i* 7 m equally develop$ z to =e & h9d limbs4 ,!y 7 sluggi% creatures1 quadrup$al 9 _! mann] ( locomotion1 veget>ians 9 reg>d to _! diet4 ,"s ( !m rea*$ enorm\s proportions & x is believ$ t !y resort$ to life 9 ! wat] 9 ord] to get "p ( ! weight (f _! feet4 ,diplodocus & ,brontosaurus are ! names ( well-kn[n giants 9 ?is gr\p4 ,!y _h long necks & tails1 v small skulls1 7 ! l>ge/ ( all l& animals & are kn[n to h rea*$ a l5g? ( eighty feet or m4 ,"s e/imates1 bas$ on measurem5ts ( incomplete skeletons1 h exce$$ "o hundr$ feet1 b ^! extremes are some:at que/ionable4 ,diplodocus 0 ! m elongat$ ( ! two1 ) mu* ( its l5g? 9 ! :ip-l tail4 ,our m\nt$ skeleton has a l5g? ( sev5ty-five feet six in*es1 measur$ along ! v]tebrae4 ,its height at ! pelvis is twelve feet six in*es4 ,! tee? ( ^! l>ge quadrup$s are ( a slightly broad5$ & blunt$ =m :i* has caus$ "s speculation z to _! possible use4 ,x has ev5 be5 sugge/$ t ! animals 7 fi%-eat]s b ?is seems impossible 9 view ( ! great size & g5]al *>act]i/ics ( ! gr\p4 ,al?\gh !y diff] extremely 9 "s respects1 !y are reg>d$ z be+ m closely relat$ to ! c>nivores ?an to ! h]bivores ( ! second great bran* ( ! tribe4 ,! unque/ion$ h]bivores1 con/itut+ ?is second bran* ( ! d9osaurian race1 also include bo? bip$s & quadrup$s4 ,! bett] kn[n plant-eat]s 7 l>ge animals b n su* mon/]s z ,tyrannosaurus or ,brontosaurus4 ,( ! bip$s1 ,tra*odon is p]haps be/ kn[n4 ,x is "o ( ! duck-bill$ d9osaurs :i* _h an av]age l5g? ( ab\t ?irty feet4 ,! duckbills 7 un>mor$1 active animals1 good swimm]s z well z runn]s4 ,!y 7 prom95t & widely di/ribut$ dur+ late ,cretace\s "t4 ,_m skeletons h be5 f\nd 9 we/]n ,nor? ,am]ica4 ,natural ca/s & impressions ( mummifi$ rema9s indicate t ! hides 7 scaly & ! feet provid$ ) webs betwe5 ! toes4 ,! bill 0 broad1 flat1 & too?less1 b ! sides ( ! m\? 7 provid$ ) a l>ge numb] ( simple tee? closely arrang$ 9 p>allel r[s4 ,! f9e skeleton exhibit$ 9 our hall is ?irty feet six in*es 9 l5g?4 ,ne> relatives ( ,tra*odon1 su* z ,cory?osaurus _h holl[1 bony cre/s1 combs1 or tubul> /ructures on top ( ! head4 ,^! may h be5 ( "s s]vice 9 connection ) brea?+ :ile fe$+ "u wat]4 ,illu/ration3 ,a ,duck-bill$ ,d9osaur ( ! ,cretace\s ,p]iod 7,tra*odon mirabilis7 ,illu/ration3 ,/egosaur 7,/egosaurus /5ops7 ,among ! quadrup$al veget>ians an int]e/+ family is repres5t$ by ,/egosaurus1 a late ,jurassic d9osaur hav+ a l5g? ( ab\t tw5ty feet4 ,^! creatures _h heavy limbs1 all us$ 9 walk+1 an ar*$ back1 & almo/ no bra9 at all4 ,a d\ble r[ ( l>ge flatt5$ plates /&+ upright & ext5d+ f ! re> ( ! skull ne>ly to ! tip ( ! tail provid$ "s protection = ! back ( ! animal1 b o!rwise !re 0 no def5sive armor4 ,sev]al long spikes at ! end ( ! tail probably s]v$ z weapons4 ,! m\nt$ skeleton 9 our collection 0 obta9$ f ,g>d5 ,p>k1 ne> ,canon ,city1 ,colorado1 a di/rict :i* has long be5 fam\s = d9osaur rema9s4 ,! ankylosaurs 7 m completely armor$ ) closely set bony plates fitt+ neatly ov] ! body4 ,!y 7 ( ab\t ! same size z ! /egosaurs b ! body 0 broad & some:at flatt5$4 ,^! armor$ quadrup$s app>5tly liv$ only dur+ ! ,cretace\s p]iod1 aft] ! disappe>ance ( ! /egosaurs4 ,_! too? equipm5t 0 v poor & 9 a few cases entirely lack+4 ,ankylosaurus & ,nodosaurus are good examples ( ! type4 ,!y h be5 describ$ z animat$ tanks & are sometimes ref]r$ to z hav+ ! appe>ance ( enorm\s horn$ toads4 ,among ! la/ ( ! d9osaurs to come & g 7 ! horn$ quadrup$s kn[n z ! ,c]atopsia4 ,_! entire hi/ory appe>s to h be5 conf9$ to ! ,upp] ,cretace\s & ! clos+ /ages ( ! reptilian era 9 ,am]ica4 ,tric]atops & ,monoclonius are well-kn[n repres5tatives ( ! gr\p4 ,besides ! horns1 :i* appe>$ above ! eyes or ne> ! c5t] ( ! nose1 !re 0 a broad1 flatt5$1 backw>d ext5sion ( "s ( ! skull bones :i* produc$ a great frill or coll> rea*+ ov] ! neck z f> back z ! %\ld]s4 ,?is frill1 comb9$ ) ! l>ge skull1 gave ! animal ! appe>ance ( be+ ne>ly "o-?ird head4 ,tric]atops _h ?ree horns1 ,monoclonius only "o4 ,! av]age l5g? ( ! animals 0 slightly "u tw5ty feet4 ,al?\gh v little is kn[n ab\t ! ance/ry ( ! horn$ d9osaurs a valuable discov]y 9 ,mongolia may ?r[ "s light on ! subject4 ,a small d9osaur ) a well-develop$ frill1 b no horns1 once inhabit$ ! region ( ! pres5t ,gobi des]t1 & 9 recognition ( ! app>5t relation%ip x has be5 nam$ ,protoc]atops4 ,9 addition to num]\s skeletons1 sev]al ne/s ( eggs 7 f\nd 9 association ) ! bones4 ,until ?is discov]y 0 made1 d9osaur eggs _h be5 practically unkn[n4 ,a reproduction ( "o ( ^! ne/s is among our exhibits4 ,illu/ration3 ,a ,sea ,turtle ( ,cretace\s ,"t 7,proto/ega gigas7 ,?is m>9e animal belongs to a gr\p :i* became ext9ct ne> ! close ( ! great reptilian era1 b a few relat$ =ms /ill survive4 ,_! weight is greatly r$uc$ by ! peculi> con/ruction ( ! %ell1 & ! front feet are enl>g$ = use z o>s1 an excell5t illu/ration ( ! mann] 9 :i* a l& type c become adapt$ to life 9 ! sea4 ,) ! possible exception ( a v few %ort-liv$ survivals d9osaurs 7 ext9ct be=e ! op5+ ( ! ,age ( ,mammals1 _m ( !m = millions ( ye>s4 ,along ) !m w5t o!r types ( anci5t reptiles1 & ! cause ( _! ext9ction is a problem :i* may nev] be solv$4 ,conditions rema9$ favorable = ! turtles1 :i* made _! fir/ appe>ance dur+ ,triassic "t1 & = ! crocodiles1 :i* date back to ! ,jurassic p]iod4 ,snakes 7 only at ! beg9n+ ( _! hi/ory z ! era clos$4 ,! survival ( ^! mod]n =ms sugge/s t !y 7 favor$ to a great] ext5t ?an ! d9osaurs dur+ a prolong$ p]iod ( *ang+ conditions ! full details ( :i* are unkn[n to u4 ,9 g5]al x is to be expect$ t disa/] w\ld fir/ ov]come ! highly specializ$ creatures1 su* z ! d9osaurs1 :i* _h become m delicately adju/$ to ! p>ticul> environm5ts 9 :i* !y liv$4 ,x appe>s t "s ( !m _h be5 too progressive up to a c]ta9 po9t1 b n suffici5tly adaptable to get beyond t /age1 or =tunate en\gh to make _! advances 9 directions t c\ld be foll[$1 ?r\gh fluctuations 9 ! matt] ( food supply1 pr$atory enemies1 climate1 & o!r factors :i* be> ^u success & failure4 ,! reptilian era clos$ ) exceptional volcanic activities 9 _m p>ts ( ! _w1 b ^! _c acc\nt = ! disappe>ance ( ! highly div]sifi$ & abundant reptilian life4 ,! eruptions 7 m]ely incid5tal to movem5ts & readju/m5ts 9 l>ge masses ( rock compris+ ! e>?'s cru/ or surface4 ,su* cru/al fold+ & elevations always h be5 ( s]i\s consequ5ces to bo? plants & animals because ( _! effect ^u dra9age & climate4 ,!re 7 di/urbances ( ?is k9d 9 we/]n ,nor? ,am]ica 9 late ,jurassic "t1 ) fold+ & uplift 9 ! region ( ! ,si]ras & probably ext5d+ f ,mexico to s\!rn ,alaska4 ,a great tr\gh to ! ea/ ( ?is elevat$ di/rict 0 produc$ 9 ! c\rse ( ^! movem5ts & provid$ access to ! sea f s\? to nor?4 ,dur+ ! ,cretace\s p]iod !re 7 repeat$ invasions & retreats ( ! sea by way ( ?is great depression1 consequ5t ^u slight *anges 9 ! elevation ( ! floor4 ,h5ce !re are num]\s m>9e =mations 9 ,colorado & adjo9+ /ates1 "s ( !m ri* 9 fossils4 ,be=e ! close ( ! ,cretace\s p]iod ! sea _h made its f9al dep>ture f ?is region1 & ! ,mesozoic era 0 t]m9at$ by revolution>y di/urbances :i* br\ght ab\t ! uplift+ ( a new m\nta9 sy/em4 ,! ,rocky ,m\nta9s may be reg>d$ z "p ( ?is sy/em & to h _h _! bir? at ?is "t4 ,! ,rockies1 h[ev]1 %[ unmi/akable signs ( repeat$ elevation1 ) int]vals ( erosion dur+ :i* !re 0 great r$uction ( _! total height4 ,:at we see ( !m today is ! result ( m ?an fifty million ye>s ( cont9u\s geological activity4 ,,plant ,,life ,,& ,,climate ,"s idea ( ! ,mesozoic climate is obta9$ f ! "* & di/ribution ( ! plant life4 ,triassic floras are n l>ge & !re is v little fossil evid5ce = ! e>li] half ( ! p]iod4 ,x is q possible t arid or des]t conditions prevail$ = a "t 9 mu* ( ,nor? ,am]ica1 z at ! close ( ! ,paleozoic era4 ,plant life 0 at fir/ n abundant1 & conditions 7 unfavorable = ! production ( fossils4 ,9 ,upp] ,triassic rocks ( ,virg9ia1 h[ev]1 !re are signs ( swampy conditions1 ) ru%es & f]ns pr$om9at+4 ,adjo9+ =e/ areas 7 well timb]$ ) l>ge conif]\s ev]gre5s :i* %[ no annual gr[? r+s1 z simil> trees d 9 regions :]e cold w9t]s alt]nate ) w>m summ]s4 ,?is sugge/s1 = t "t & place at lea/1 a uni=mly w>m climate1 lack+ seasonal v>iations4 ,w>m temp]ature or subtropical climates are indicat$ aga9 by "s ( ! ,jurassic & ,cretace\s plants1 b int]vals ( l[] temp]atures & v>iable climates are also app>5t4 ,palms1 figs1 & o!r trees1 v simil> to mod]n types n[ liv+ only 9 w>m] regions1 7 widely di/ribut$ 9 late ,cretace\s "t1 & _! range 0 ext5d$ into regions :i* h s9ce become too cold to support su* gr[?s4 ,! tr5d t[>d mod]n =ms 9 ! plant _w 0 gradual1 b ?r\gh\t ! era !re 7 occasional novelties t attract ! att5tion ( botani/s4 ,f]ns & horsetail ru%es1 rem9isc5t ( ! ,paleozoic =e/s1 soon began to lose _! prom95ce z ! se$-be>+ trees ga9$ ! asc5d5cy4 ,mesozoic "t c\ld well be call$ ! age ( cycads1 because ( ! /rik+ p]=mance ( ?is plant gr\p4 ,diff]5t v>ieties fl\ri%$ 9 ! ?ree p]iods1 ) ! ,jurassic /&+ out z ! "t ( greate/ abundance4 ,to ! un9itiat$1 ! usual cycad fossils resemble 8petrifi$ p9eapples10 b ^! are m]ely ! sc>r$ /ems or trunks ( small to m$ium-siz$ trees ) a tuft$ arrangem5t ( leaves at ! top1 & usually )\t bran*es4 ,foliage & habit ( gr[? sugge/ some?+ m l l>ge f]ns or l[-gr[+ palms1 ) %ort1 ?ick trunks seldom m ?an fifte5 feet tall & _m ( !m "u ?ree feet4 ,! leaves are r>ely f\nd entire or atta*$ to ! trunks1 b occasional discov]ies indicate a leaf-l5g? ( ab\t t5 feet4 ,al?\gh !y are class$ among ! fir/ & l[e/ ( se$-be>+ plants1 & 9 ?is respect are relat$ to ! conif]s1 _! appe>ance 0 q unlike t ( ! mod]n cone-be>+ ev]gre5s4 ,m ne>ly resembl+ ! common conif]s ( today 7 ! sequoias1 ( e>ly ,mesozoic orig9 & f> m abundant dur+ ,cretace\s "t ?an !y are at pres5t4 ,! maid5hair trees1 n[ repres5t$ by a s+le species ( ,g9kgo :i* is cultivat$ pr9cipally 9 ,*9a & ,japan1 7 nev] v prom95t b are ( int]e/ z an anci5t family t p]si/$ ?r\gh\t ! ,mesozoic & d[n to our own "t4 ,be=e ! close ( ! ,cretace\s p]iod ! fl[]+ plants _h greatly outnumb]$ ! spore-be>+ gr\ps1 su* z ! f]ns & horsetails :i* 7 =m]ly s abundant4 ,we "k little ( e>ly fl[]s1 h[ev]1 except 9 connection ) trees1 ! l>ge gayly color$ blossoms ( ! type n[ conspicu\s 9 woodl&s1 mead[s1 & g>d5s be+ lat] arrivals & poor subjects = pres]vation z fossils4 ,cretace\s floras 7 surpris+ly mod]n 9 "*1 f> 9 advance ( ! animal life4 ,popl>s1 plane trees1 magnolias1 palms1 figs1 oaks1 & buck?orns 7 abundant at ! close ( ! ,cretace\s1 z indicat$ by fossils ( ! ,l>amie =mation1 :i* is ! surface rock 9 _m localities ne> ,d5v]4 ,also abundant 9 v>i\s places at ?is "t 7 walnut1 hazelnut1 laurel1 tulip1 maple1 bee*1 bir*1 breadfruit1 ivy1 holly1 & _m o!r well-kn[n trees & %rubs4 ,s$ges & grasses1 :i* became s important to ! h]bivor\s mammals ( ! next era1 made _! fir/ appe>ance 9 ,cretace\s "t b 7 !n inconspicu\s4 ,,coal ,,& ,,fossil ,,footpr9ts ,! abundance ( plant life 9 ! ,colorado area dur+ ! ,cretace\s p]iod is indicat$ by ! ext5t ( coal deposits ( ?is age4 ,ab\t "o-f\r? ! area ( ! /ate is und]la9 by coal seams v>y+ 9 ?ickness f a few in*es to fifty feet or m1 mo/ ( x be+ ,cretace\s4 ,9 ! nor!rn ,colorado di/rict ! coal-be>+ =mation is ! ,l>amie4 ,ne> ,d5v] !re is "s coal 9 ! ,arapahoe =mation :i* ov]lies ! ,l>amie & is ( lat] age4 ,coal m9es (t5 produce excell5t plant fossils1 & occasionally o!r evid5ce ( prehi/oric life4 ,9 a m9e ne> ,canon ,city1 ,colorado1 a s]ies ( natural ca/s ( d9osaur feet 0 tak5 f ! ov]ly+ rock aft] ! coal _h be5 remov$4 ,"o ( ^!1 9 ! ,d5v] ,museum ( ,natural ,hi/ory1 is se5 to consi/ ( s&/one inside a v ?9 lay] ( d>k clay4 ,flatt5$ aga9/ ! l[] surface is ! c>boniz$ /em ( a ,cretace\s plant :i* grew 9 ! swamp :]e ! coal deposit 0 =m$4 ,s9ce ! %ape ( d9osaur feet is unmi/akable we c only assume t a l>ge reptile ( ?is type walk$ ov] ! surface ( swampy gr\nd 9 :i* a great ?ickness ( decay+ vegetation _h accumulat$4 ,a lay] ( mud settl$ ov] ! top & became suffici5tly firm to reta9 ! mold ( ! feet z ! animal mov$ along4 ,any plant mat]ial ei!r on ! mud or includ$ 9 x 0 pu%$ to ! bottom ( ! impressions & flatt5$ out by ! weight ( ! huge creature4 ,!n s& 0 wa%$ into ! footpr9ts f "s ne>by s\rce dur+ a heavy ra9/orm4 ,foll[+ ^! ev5ts !re 0 probably a subsid5ce ( ! area1 & a great ?ickness ( rock-mak+ s$im5ts 0 built ov] ! anci5t swamp4 ,! buri$ vegetation gradually became conv]t$ into coal1 ! s& consolidat$ into a firm s&/one1 & ! mud produc$ ! %ales =m+ ! ro( ( ! pres5t m9e1 :i* is n[ at an elevation ( a mile above sea level z a consequ5ce ( ! g5]al uplift+ ( ! ,rocky ,m\nta9 region dur+ late ,cretace\s & subsequ5t "t4 ,:5 ! coal 0 remov$1 ! h>d s&/one ca/s sep>at$ readily f ! s(t] %ales surr\nd+ !m4 ,a small am\nt ( ! %ale adh]es to ! s&/one1 & "s ( ! flatt5$ vegetation1 n[ 9 ! condition ( coal1 /ill rema9s atta*$4 ,,mesozoic ,,inv]tebrates ,z 9 o!r eras1 ! inv]tebrates fluctuate ) ! p]iods4 ,*>act]i/ic =ms appe>1 become m or less prom95t1 !n 9 _m cases decl9e or disappe>4 ,v>iations among ! mollusks are p>ticul>ly helpful 9 ! id5tification ( rocks :i* orig9at$ 9 ! ,cretace\s seas4 ,clam-l bivalves ( ! g5us ,inoc]amus1 ! /raight-%ell$ ammonids kn[n z ,baculites1 & oy/]s1 are locally common 9 "s ( ! =mations expos$ a few miles we/ ( ,d5v]4 ,! ammonids1 or 8ammonites10 7 extremely abundant ?r\gh\t ! _w dur+ ,mesozoic "t4 ,_! %ells 7 *amb]$ l ^? ( ! pe>ly nautilus1 a relat$ cephalopod mollusk inhabit+ tropical seas at ! pres5t "t4 ,:ile only f\r species ( ! ,nautilus tribe are liv+ today1 ?\s&s ( species ( ammonids sw>m$ ! prehi/oric seas4 ,_m new =ms came into exi/5ce 9 ,triassic "t b few surviv$ ! p]iod4 ,a pron\nc$ revival occurr$ 9 ! ,jurassic1 only to be foll[$ by a decl9e & ev5tual ext9ction at ! close ( ! ,cretace\s4 ,ammonites measur+ ?ree or f\r in*es across ! diamet] ( ! coil$ %ell 7 ab\t av]age size1 b diamet]s up to ?ree or f\r feet 7 n uncommon4 ,ext]nally ! %ells 7 ornam5t$ ) ribs1 knobs1 & sp9es2 inside 0 a pe>ly l9+4 ,! p>titions 7 ?9 & compos$ ( ! same pe>l-l sub/ance z ! l9+4 ,ea* p>tition becomes wavy z x approa*es ! %ell1 & ! l9e ( union has a di/9ct patt]n :i* is se5 9 specim5s :i* h lo/ ! out] %ell lay]4 ,?is wavy suture l9e becomes m complicat$ 9 ! lat] memb]s ( ! race1 & ! peculi> m>k+s develop$ by ! repeat$ p>titions provide a conv5i5t me?od ( id5tification4 ,! belemnites or ink-fi%es1 reg>d$ z ance/ors ( ! cuttlefi%es n[ liv+1 comprise ano!r gr\p ( c>nivor\s mollusks4 ,^!1 h[ev]1 _h lo/ ! ext]nal %ell1 & ! usual fossil is "p ( an int]nal %ell or 8skeleton10 kn[n z ! gu>d4 ,?is limy /ructure has ! =m ( a po9t$ cig>1 & is seldom ov] a foot long al?\gh ! total body-l5g? ( ! l>g] animals 0 commonly ab\t six to eight feet4 ,sev]al hundr$ species h be5 describ$1 ! majority be+ ( ,jurassic age4 ,!y decl9$ rapidly t[>d ! close ( ! era4 ,! inv]tebrate life ( ! ,mesozoic 0 /rongly dom9at$ by mollusks1 ) cephalopods 9 fir/ place1 ! bivalve pelecypods & ! s+le-valve ga/ropods or snail-l =ms %>+ subord9ate positions4 ,! dom9at+ trilobites1 sea-scorpions1 & tetracorals ( ! ,paleozoic _h disappe>$1 :ile ! bra*iopods & cr9oids 7 greatly modifi$ & m l ! =ms :i* live today4 ,cr9oids became mod]ately abundant at v>i\s times1 b 9 _m ways diff]5t f _! relatives ( ! prec$+ era4 ,"s ( ! l>ge/ kn[n species1 ) /ems e/imat$ z fifty feet long1 h be5 f\nd 9 l[] ,jurassic rocks4 ,a great abundance ( microscopic life is indicat$ by ! frequ5t occurr5ce ( *alk 9 ! ,cretace\s =mations4 ,corals ( ! mod]n reef-build+ type 7hexacorals7 7 common 9 ! w>m seas ( a l>ge "p ( ! _w4 ,! insects ( ! e>ly ,mesozoic are repres5t$ by few fossils al?\gh x is evid5t "s new =ms 7 becom+ e/abli%$4 ,! w>m climates prevail+ ?r\gh\t mu* ( ! _w appe> to h be5 a favorable factor 9 ! progress ( insect life4 ,9 addition to ! old] cockroa* & dragon-fly types may be m5tion$ ! arrival ( gras%opp]s1 cicadas1 caddis-flies1 beetles1 & ants4 ,sev]al hundr$ species are f\nd 9 ,jurassic rocks1 & by ! end ( ! ,cretace\s p]iod mo/ ( ! insect families n[ kn[n to u 7 probably 9 exi/5ce4 ,! record is s]i\sly obscur$ by ! erosion ( rocks :i* s frequ5tly m>ks ! end ( a p]iod1 also by ! small size ( ! subjects1 & by ! exceptional conditions requir$ = ! production ( su* delicate fossils4 ,among ! la/ ( ! famili> insects to appe> 7 ! bees & butt]flies4 ,^! evid5tly came 9 ) ! m advanc$ types ( fl[]+ plants t produce ! nect> on :i* _m insects fe$4 ,x is probable1 too1 t )\t ! arrival ( ^! insects & _! s]vice 9 ! poll9ation ( fl[]s1 ! floras ( today w\ld be r diff]5t f :at !y are4 ,,ext9ct ,,birds ,x is n surpris+ to f9d t birds made _! fir/ appe>ance 9 ! ,mesozoic era1 = ( all animals !y are mo/ l ! reptiles z a class4 ,fea!rs are ab\t ! only dep5dable *>act]i/ic ( ! entire gr\p1 ne>ly e o!r feature be+ mat*$ by "s reptilian creature ( great antiquity4 ,! ne/+ habit1 :i* includes c>e ( ! "y z well z ! eggs1 is a matt] ( progress :i* relates to flight & to w>m] body temp]ature4 ,x appe>s to h be5 develop$ by =e/-dwell+ types liv+ among trees & ne/+ !re 9 comp>ative safety f enemies pr[l+ on ! gr\nd4 ,! olde/ kn[n prehi/oric birds 7 f\nd 9 li?ographic /one ( ,upp] ,jurassic age4 ,ar*aeopt]ix 0 discov]$ 9 #ahfa at ,sol5h(51 ,g]many4 ,sixte5 ye>s lat] a simil> bird 9 a bett] /ate ( pres]vation 0 f\nd 9 ,bav>ia4 ,! latt] 0 nam$ ,ar*aeornis4 ,^! ,jurassic fossils are reg>d$ z true birds by "s au?orities1 :ile o!rs believe !m to be m ne>ly relat$ to ! reptiles1 ! op9ions be+ bas$ on c>eful /udies ( ! skulls & o!r skeletal features4 ,bo? birds _h tee? ( reptilian "*1 & x is evid5t t !re 0 no beak1 = ! jaws 7 cov]$ ) scaly sk94 ,! bony con/ruction ( ! long tail w\ld sugge/ liz>ds r ?an birds1 7 x n = ! pres5ce ( fea!rs :i* 7 atta*$ at ea* side4 ,head1 neck1 & p>ts ( ! body 7 cov]$ ) scales4 ,w+s 7 well provid$ ) /\t fea!rs b ! skeletal framework indicates t ! birds 7 glid]s r ?an true fly]s4 ,claws on ! w+s s]v$ l f+]s to aid 9 climb+ among ! bran*es ( trees1 a practice :i* is occasionally not$ among ! "y ( liv+ birds4 ,9 adult birds ( today1 h[ev]1 ! claw-l app5dages ( ! =e limbs are greatly r$uc$ & ( little s]vice4 ,! next fossil birds ( importance h be5 f\nd 9 ,cretace\s rocks ( ,kansas1 bo? ( !m fi%]s ( ! seas in/ead ( =e/ inhabitants4 ,i*?yornis 0 a small bird1 /&+ ab\t eight in*es 9 height1 a p[]ful fly] ) reptilian jaws & tee?4 ,hesp]ornis 0 built = div+ & swimm+1 l ! loon1 b 0 some:at l>g] & provid$ ) tee?4 ,its w+s 7 too poorly develop$ to be ( use 9 fly+4 ,too!d birds became ext9ct ) ! close ( ,cretace\s "t1 & ! ance/ors ( mod]n types 7 9 exi/5ce be=e ! ,age ( ,mammals1 b fossil rema9s are few & poorly pres]v$4 ,l>ge o/ri*-l birds1 h[ev]1 are kn[n to h liv$ 9 ,nor? ,am]ica dur+ ! ,eoc5e p]iod4 ,"o ( ^!1 nam$ ,diatryma1 /&s ne>ly sev5 feet tall 9 ! recon/ruct$ skeleton4 ,its legs are heavy1 w+s greatly r$uc$1 beak massive4 ,9 its relation to mod]n birds x is possibly ne>] to ! cranes ?an ! o/ri*es4 ,flightless birds ( l>ge size are kn[n f _m p>ts ( ! _w & seem to h be5 prom95t ?r\gh\t ! ,c5ozoic era1 z !y are today 9 ! s\!rn hemisph]e4 ,aepyornis liv$ 9 ,madagasc> dur+ ! ,plei/oc5e p]iod & may h become ext9ct q rec5tly4 ,its eggs are ! l>ge/ kn[n among fossils1 sev]al times ! size ( an o/ri* egg4 ,also 9 ?is p]iod ! moas 7 liv+ 9 ,new ,zeal& :]e _! rema9s are /ill abundant4 ,"o ( ! l>ge/1 kn[n z ,d9ornis1 _h ab\t ! same =m z ,diatryma b ! neck 0 long]1 head & beak small]1 legs bett] fitt$ = runn+1 height ab\t elev5 feet4 ,a mu* small] flightless bird1 ! dodo1 became ext9ct 9 mod]n "t4 ,?is =m] inhabitant ( ,mauritius & o!r isl&s ( ! ,indian ,ocean 0 relat$ to ! doves & pigeons1 & _h lo/ its p[] ( flight ?r\gh disuse ( ! w+s4 ,x 0 a clumsy1 def5seless bird weigh+ possibly z mu* z fifty p\nds4 ,actual rema9s are few & incomplete1 & descriptions publi%$ by ! explor]s :o knew ! bird two c5turies ago are n entirely tru/wor?y4 ,9 ! ,plei/oc5e ,ran*o la ,brea b$s ( ,cali=nia ! l>ge/ ( all prehi/oric fly+ birds has be5 f\nd1 a vulture be>+ ! "n ( ,t]atornis4 ,re-assembl$ skeletons %[ !m to be slightly bigg] ?an exi/+ condors4 ,,ance/ors ,,( ,,! ,,mammals ,! monotremes or egg-lay+ types ( mammals su* z ! duck-bill & sp9y anteat]s :i* n[ inhabit ,au/ralia are almo/ unkn[n z fossils4 ,m>supials1 ! next high] liv+ gr\p1 :i* includes ! opossum & kang>oo1 appe>$ at ! end ( ,cretace\s "t along ) ! plac5tals or high] mammals :i* dom9ate ! hi/ory ( ! ,c5ozoic era4 ,nev]!less1 !re are a few tee? & jaws f rocks ( ,triassic & ,jurassic age to indicate t small mammals1 f ! size ( mice to slightly l>g] ?an rats1 exi/$ ?r\gh\t mo/ ( ! ,age ( ,reptiles4 ,!re is no complete skeleton ( any ( ! e>li] =ms1 & little is kn[n ( _! relation%ips ei!r ) liv+ ord]s ( mammals or ) probable ance/ors among ! reptiles4 ,! record becomes some:at cle>] t[>d ! end ( ! era b x is obscur$ aga9 by ! great di/urbances :i* foll[$4 ,look+ back among e>li] l& animals = ! orig9 ( ! fir/ mammalian /ock x is necess>y to g z f> z ,p]mian or ev5 ,c>bonif]\s "t4 ,reptiles !n liv+ _h _m /ructural features 9 common ) mammals1 & mammal-l =ms cont9u$ to fl\ri% until late 9 ! ,triassic4 ,an int]e/+ gr\p ( su* animals1 nam$ !rapsids1 0 "o ( ! e>lie/ reptilian /ocks to appe>1 & is well kn[n f fossils f\nd 9 ! ,r$ ,b$s ( ,texas & ,new ,mexico1 9 ,europe1 ,s\? ,africa1 & ,asia4 ,q a v>iety ( types is includ$ 9 ?is gr\p1 ) _m advances 9 d5tition1 & modifications ( ! skull1 limbs & pelvic con/ruction :i* /rongly sugge/s a relation%ip to ! mammals4 ,illu/ration3 ,murals ,ov] ,fossil ,exhibits1 ,hall ( ,mammals ,top3 ,eoc5e2 ,protylopus1 ,tanyorh9us1 ,patri(elis1 ,u9ta!rium1 ,turtle1 ,crocodile1 ,eohippus4 ,middle3 ,upp] ,oligoc5e2 ,mesohippus1 ,m]ycoidodon1 ,hoplophoneus1 ,metamynodon1 ,poebro!rium1 ,trigonias4 ,bottom3 ,plioc5e2 ,teleoc]as1 ,turtle1 ,syn!toc]as1 ,amebelodon1 ,teleoc]as4 ,,! ,,age ,,( ,,mammals ,! /rik+ feature ( life developm5t 9 ! ,c5ozoic era is ! great progress & expansion ov] ! e>? ( ! mammalian races4 ,! division ( ! era into p]iods1 h[ev]1 0 bas$ l>gely on a /udy ( fossil mollusks4 ,9 ! ,p>is bas9 ( ,france1 x 0 notic$ by ! geologi/s ( a c5tury ago t ! y\nge/ ( ! s$im5t>y b$s conta9$ ! greate/ numb] ( rec5t or /ill liv+ species4 ,successively d[nw>d into ! old] b$s ! p]c5tage ( rec5t species decreas$ until !re 7 practically no liv+ species repres5t$ 9 ! olde/ rocks ( ! s]ies4 ,f ! p]c5tage ( rec5t =ms among prehi/oric ones x 0 propos$ t ! foll[+ division be made3 ,eoc5e1 mean+ dawn ( ! rec5t2 ,mioc5e1 mean+ less rec5t2 & ,plioc5e1 mean+ m rec5t4 ,sometime lat] x 0 sugge/$ t ano!r p]iod be add$1 & to ?is 0 giv5 ! "n ,plei/oc5e1 mean+ mo/ rec5t4 ,9 #ahed1 ! old] ,mioc5e =mations 7 segregat$ & ref]r$ to a newly provid$ ,oligoc5e p]iod1 ?is "n mean+ little ( ! rec5t4 ,e>ly geologi/s gr\p$ ! rocks 9 ?ree great divisions1 apply+ ! names ,prim>y1 ,second>y1 & ,t]ti>y4 ,to ^! 0 add$ aft]w>ds ! "n ,quat]n>y1 :i* appli$ to ! y\nge/ =mations ( ! e>?4 ,only two ( ^! t]ms rema9 9 common use at pres5t3 x is a frequ5t practice to ref] to ! comb9$ ,eoc5e1 ,oligoc5e1 ,mioc5e & ,plioc5e p]iods z ! 8,t]ti>y0 division ( ,c5ozoic "t2 to ! ,plei/oc5e & ,rec5t p]iods z ! 8,quat]n>y0 division4 ,! geology ( "s remote future may be cle>] ) reg>d to ! full significance ( ?is subdivision ( ! ,age ( ,mammals into two p>ts4 ,x may be t a great era 0 conclud$ at ! end ( ,plioc5e "t z o!rs h be5 conclud$1 by ! usual e>? di/urbances & climatic *anges & by ! decl9e ( animals once prom95t 9 ! faunas ( ! _w4 ,ev5ts ( su* "* h regi/]$ _! occurr5ce b may ev5tually prove to h be5 a s]ies ( m9or ev5ts n comp>able ) ! revolution>y *anges t t]m9at$ o!r great "t divisions4 ,! favor$ practice ( includ+ ourselves & our times 9 ! ,c5ozoic is bas$ on a tr5d ( op9ion :i* holds t no great era has be5 end$ s9ce ! ,age ( ,reptiles 0 conclud$4 ,illu/ration3 ,skulls ( ! clumsy1 six-horn$ u9ta!re & ! e>ly1 hornless titano!re =m "p ( ?is ,eoc5e display4 ,9 ! mural ^! animals & ! little 8?ree-to$0 ,eohippus1 smalle/ ( horses1 are pictur$ ) a contempor>y turtle & crocodile4 ,! olde/ ( ,eoc5e rocks %[ a great v>iety ( mammals & a /range assortm5t ( =ms f> 9 advance ( ! ,mesozoic record4 ,ance/ries & successive /ages ( developm5t h be5 only p>tially work$ out1 ?\gh details h be5 bett] pres]v$ = "s ( ! gr\ps ?an = o!rs4 ,"s oddly %ap$ creatures su* z ! u9ta!res rea*$ _! full developm5t 9 a relatively %ort "t & pass$ out ( ! picture be=e ! end ( ! p]iod4 ,^! animals1 repres5t$ 9 our collection by ,u9tacolo!rium1 acquir$ l>ge bodies & _m horns1 b a peculi> too? equipm5t fitt$ !m = a special diet :i* app>5tly fail$ to be suppli$ 9 suffici5t abundance at a critical "t4 ,on ! o!r h&1 we f9d 9 ?is p]iod ! ance/ors ( m successful gr\ps1 "s ( :i* cont9ue on into mod]n times4 ,only a few ( ^! hi/ories c be trac$ 9 a brief sket*1 b 9 a g5]al way x may be /at$ t ! successful races _h mode/ beg9n+s & t !y develop$ v sl[ly into :at !y are n[1 by a process ( adju/+ !mselves1 or by becom+ bett] adapt$ to new or previ\sly unus$ conditions 9 _! respective environm5ts4 ,9 _! e>ly /ages ! v>i\s types _h mu* 9 common2 !y 7 g5]aliz$1 r ?an specializ$ = any p>ticul> k9d ( exi/5ce4 ,:at !y 7 fitt$ = is be/ indicat$ by _! tee? & feet1 ?\gh o!r /ructural features frequ5tly contribute valuable in=mation4 ,! rise ( m5tality is indicat$ by skull capacities & ! increas+ developm5t ( ! upp] lobes ( ! bra91 z reveal$ by ca/s tak5 f ! int]ior ( skulls4 ,! creodonts 7 ! e>lie/ & mo/ primitive ( ! fle%-eat+ mammals or c>nivores4 ,_m ( !m 7 small ( body & bra91 & equipp$ ) tee? t indicate a mix$ or l>gely insectivor\s diet1 or possibly ! habit ( fe$+ on c>rion4 ,al?\gh !re 0 consid]able v>iation among !m1 & "s t5d5cy t[>d specialization1 !re 0 little to sugge/ ! com+ ( m progressive gr\ps su* z ! cats & dogs1 ) tee? p]fect$ = ! te>+ & cutt+ ( fle%1 & feet especially fitt$ = ! life ( hunt]s4 ,! ance/ry ( ! cats _c be trac$ f>!r back ?an ! ,oligoc5e b x probably connects some:]e prior to t "t ) ! creodonts4 ,cynodictis1 an ,oligoc5e c>nivore slightly "u two feet 9 l5g? is commonly reg>d$ z a primitive dog1 b its *>act]s are s g5]aliz$ t x probably diff]s b little f ! ance/ors ( _m o!r c>nivores4 ,! skeleton ( ?is animal sugge/s a sl5d] & flexible body l t ( ! weasel1 ) some:at %ort5$ limbs & a long tail4 ,x liv$ 9 =e/$ regions & 0 probably m or less ( a tree dwell]4 ,! m advanc$ c>nivores requir$ long] legs1 bett] adapt$ = runn+ & ov]tak+ ! prey1 :i* is ! dog's way ( hunt+1 or = /alk+ & spr++ ^u ! qu>ry1 :i* is ! me?od ( ! cat4 ,illu/ration3 ,moropus 7,moropus cooki7 ,?\gh its tee? cle>ly indicate a diet ( plant mat]ial1 ?is /range animal _h claws on its toes1 l ! c>nivores4 ,x is probable t ! claws 7 us$ 9 digg+ = roots1 z indicat$ by ! arti/4 ,a prom95t gr\p ( mammals today is t kn[n z ! ungulates1 or ho($ animals1 :i* includes ! horses1 cattle1 de]1 sw9e1 rh9oc]oses1 tapirs1 & o!r types bo? liv+ & ext9ct4 ,_! probable ance/ors 7 ! condyl>?s1 primitive ungulates ( ! ,eoc5e p]iod4 ,"o ( ^!1 kn[n z ,ph5acodus1 s]ves well to illu/rate ! g5]al "* ( ! e>ly ho($ mammals4 ,x 0 ab\t five & "o-half feet long1 r l>ge = its "t1 ) long tail & %ort limbs1 l[ elongat$ skull & small bra91 v simil> 9 _m respects to ! creodonts or ance/ral c>nivores4 ,! tee?1 h[ev]1 7 p>tially ( ! gr9d+ type s ess5tial to ! welf>e ( plant fe$]s4 ,! condyl>?s 7 five-to$ animals & evid5tly provid$ ) small ho(s1 b ! m progressive ungulates soon lo/ "o or m ( ! toes1 & a division ( ! gr\p into odd-to$ & ev5-to$ bran*es became firmly e/abli%$4 ,consequ5tly1 ! families ( ungulates hav+ "o1 ?ree1 or five toes are class$ toge!r z be+ closely relat$ to "o ano!r1 & ^? hav+ two or f\r toes are segregat$ 9 a second lot4 ,! odd-to$ clan1 kn[n z p]issodactyls1 includ$ su* animals z ! horses1 rh9oc]oses1 tapirs1 & titano!res1 ea* ( ^! types be+ plac$ 9 a sep>ate family4 ,! ev5-to$ clan has be5 treat$ 9 a simil> way & nam$ ! artiodactyls4 ,9 ?is division are su* families z sw9e1 cattle1 de]1 camels1 oreodonts1 & o!rs4 ,! odd-to$ gr\p dom9at$ among ! l>g] animals ( ,nor? ,am]ica = a "t b has be5 completely replac$ by ! ev5-to$ division :i* is /ill fl\ri%+1 al?\gh "s ( ! old] families h become ext9ct4 ,among ! exhibits ( ! ,d5v] ,museum ( ,natural ,hi/ory may be se5 complete skeletons ( ext9ct horses1 rh9oc]oses1 titano!res1 & *alico!res repres5t+ ! p]issodactyls4 ,moropus 0 "o ( ! *alico!res1 an exceptional family :i* nev] became v prom95t al?\gh x _h a prolong$ hi/ory & p]si/$ 9 ,europe & ,asia aft] its ext9ction 9 ,nor? ,am]ica4 ,! family is gr\p$ ) ! ungulates because ( _m simil>ities f\nd 9 ! mol> tee?1 skulls1 & o!r p>ts ( ! skeletons1 b ! toes 7 provid$ ) claws in/ead ( ho(s4 ,! use ( ^! claws is some:at ( a puzzle3 possibly = def5se aga9/ c>nivor\s enemies1 = dragg+ d[n bran*es 9 ord] to obta9 food1 or = digg+ roots :i* may h be5 an important "p ( ! diet4 ,titano!res are repres5t$ 9 our collection by ! skeletons ( ! l>ge1 horn$ type :i* 0 ! la/ ( ! race & de/9$ to ext9ction by ! middle ( ! ,oligoc5e p]iod4 ,small] hornless v>ieties ( ,eoc5e "t are illu/rat$ by skulls4 ,?is family ( ungulates _h an unprogressive d5tal equipm5t1 & a small bra9 9 a flatt5$ skull4 ,! mol> tee? readily di/+ui% ! gr\p f o!r ungulates & enable u to trace ! relation%ip betwe5 e>li] & lat] v>ieties4 ,^! tee? 7 ( a type :i* is soon de/roy$ by we>1 & x is evid5t t ! animals surviv$ only s long z _! environm5t provid$ !m ) an abundance ( s(t vegetation4 ,illu/ration3 ,titano!res ( ,oligoc5e ,"t ,! "n ( ^! animals ref]s to ! l>ge size ?\gh !y 7 greatly exce$$ 9 bulk by ! ma/odons & mammo?s ( lat] p]iods4 ,ance/ral titano!res1 dat+ back to ! ,eoc5e1 7 hornless animals ( mu* small] size4 ,^! spl5did specim5s 7 obta9$ 9 ,weld ,c\nty1 ,colorado4 ,! l>ge assortm5t ( rh9oc]os mat]ial provides an idea ( ! great abundance & v>iety ( =ms 9 ?is family :i* 0 once prom95t 9 ,nor? ,am]ica b no long] among ! inhabitants ( t cont95t4 ,"s ( ! m\nt$ skeletons h be5 re/or$ on "o side to %[ h[ ^! animals appe>$ 9 ! fle%4 ,( ! ev5-to$ ungulates !re are also sev]al types illu/rat$ by complete skeletons4 ,m]yco*o]us1 ! subject ( "o ( our m\nt$ gr\ps1 repres5ts ! oreodonts1 a l>ge family ( mammals ^: hi/ory beg9s ) ! ,upp] ,eoc5e & ends 9 ! ,l[] ,plioc5e4 ,! oreodonts 7 small animals1 r pig-l 9 =m & q common 9 ! we/]n pla9s region %ortly aft] ! "t ( ! titano!res4 ,anci5t sw9e are repres5t$ 9 our exhibits by two m\nt$ skeletons :i* 7 obta9$ f nor!a/]n ,colorado1 :]e ! bones 7 f\nd associat$ ) rh9oc]os & titano!re rema9s4 ,"s ( ^! animals 7 ( v l>ge proportions1 & ! entire family is commonly kn[n z ! 8giant pigs40 ,camels & closely relat$ =ms 7 q abundant 9 ,nor? ,am]ica f e>ly ,oligoc5e to comp>atively rec5t "t4 ,num]\s types 7 develop$ dur+ ! c\rse ( _! hi/ory1 "s small & delicately =m$1 o!rs tall & clumsy & mu* l ! giraffe 9 /ructure4 ,p>ts ( _m ( ^! creatures h be5 f\nd b ! only completely prep>$ skeletons 9 our collection are ( ! little gazelle-camel1 ,/5omylus1 f ,l[] ,mioc5e deposits 9 nor?we/]n ,nebraska4 ,plei/oc5e bisons are repres5t$ by sev]al complete skeletons & num]\s skulls & horncores1 "s ( ! species %[+ an extreme developm5t 9 ! l5g? ( horns4 ,) two ( ! bison skeletons are %[n prehi/oric weapon po9ts1 f\nd ) ! bones & indicat+ t ^! animals 7 hunt$ by primitive m5 at "s "t ne> ! close ( ! ,ice ,age4 ,! artifacts fir/ discov]$ ne> ,folsom1 ,new ,mexico1 by field work]s ( our ,museum1 h become kn[n to ar*eologi/s z ,folsom po9ts4 ,,prehi/oric ,,horses ,! pa/ hi/ory ( horses is well kn[n f an abundance ( fossil mat]ial1 rang+ 9 age f ! ,eoc5e d[n to ! pres5t4 ,mod]n horses h only "o toe 9 ea* foot1 b !re are remnants ( two additional toes :i* may be se5 only 9 ! bony /ructure und]ly+ ! sk94 ,mo/ ( _! ance/ral relatives 7 ?ree-to$ z f> back z ! ,oligoc5e p]iod4 ,dur+ ,eoc5e "t1 h[ev]1 !re 0 a /age :i* may be reg>d$ z f\r-to$ al?\gh x 0 evid5tly a tempor>y condition1 l9k+ kn[n horses ) m remote =ms hav+ five toes4 ,illu/ration3 ,oligoc5e ,mammals ,f ,weld ,c\nty1 ,colorado ,! giant pigs 7,ar*aeo!rium mortoni7 at ! left ( ! gr\p1 & ! rh9oc]os 7,trigonias osborni7 7 common animals ( ! we/]n pla9s region at "o "t4 ,eohippus1 ! 8dawn horse0 z x has be5 call$1 is "o ( ! olde/ & be/ kn[n ( ! ,am]ican horses4 ,its relation to exi/+ memb]s ( ! family c be trac$ by means ( *anges 9 too? /ructure z well z 9 ! gradual r$uction 9 ! numb] ( toes t is se5 among int]m$iate =ms4 ,its ance/ors "s day may be positively id5tifi$ 9 t gr\p ( g5]aliz$1 primitive1 five-to$1 ho($ mammals :i* are kn[n to h liv$ at ! beg9n+ ( ! mammalian era1 b su* id5tification has n yet be5 e/abli%$4 ,ev5 ,eohippus bore little resemblance to ! famili> horse ( today4 ,its height 0 only elev5 in*es1 & 9 body =m x _h mu* ( ! appe>ance ( a mod]n dog4 ,!re 7 f\r toes on ! front foot1 "o ( !m decid$ly %ort] ?an ! o!rs b complete 9 all its p>ts1 & evid5tly capable ( s]vice 9 c>ry+ a portion ( ! animal's weight4 ,! h9d foot _h ?ree complete toes & a t9y remnant ( a f\r? :i* c\ld n h be5 app>5t ext]nally4 ,z *anges 9 ! /ructure ( ! feet progress$1 ! c5tral toe ( ! orig9al five cont9u$ to increase 9 size :ile ! adjac5t digits became relatively %ort] & ev5tually s r$uc$ 9 l5g? t !y c\ld t\* ! gr\nd no long]4 ,! small] bones at ! extremities1 correspond+ to ! jo9ts ( our f+]s & toes1 ev5tually disappe>$ f ! side toes4 ,!n ! long] bones ( ! out] digits lo/ ! broad5$ support+ surface1 :]e ! miss+ toes _h be5 atta*$1 & became r$uc$ to po9t$ remnants kn[n z spl9ts4 ,extreme %ort5+ ( ! spl9t bones ev5tually leaves only a small knob :i* is (t5 ref]r$ to z a rudim5t>y toe4 ,9 ! skeleton ( a l>ge horse ! spl9ts are readily se51 b 9 "s ( ! e>li] species !y are s small t !y may easily be de/roy$ or ov]look$ by ! collector :o removes ! fossiliz$ mat]ial f ! surr\nd+ rocks4 ,ev5 !n1 ! bones ( ! wri/ & ankle may indicate 9 an unmi/akable mann] t an additional toe once 0 pres5t1 = ea* bone is support$ by ano!r1 & at ! po9t ( atta*m5t !re is a *>act]i/ic surface ^: purpose is usually obvi\s4 ,?r\gh\t ! ,c5ozoic era ! *anges cont9u$4 ,among ! horses ( ! ,nor? ,am]ican ,oligoc5e 7 ,mesohippus1 approximately ! size ( a collie dog1 & ,miohippus :i* 0 slightly l>g]4 ,bo? 7 ?ree-to$1 b ! rudim5t>y spl9t ( a f\r? toe 0 /ill pres5t 9 ! front foot4 ,p>ahippus & ,m]y*ippus c>ri$ on dur+ ! ,mioc5e p]iod1 ! latt] be+ *>act]i/ic ( ! "t1 & %[+1 9 addition to o!r progress1 a decid$ tr5d t[>d ! mod]n /ructure ( mol> tee?4 ,!re 0 "s increase 9 size b ! l>ge/ horse ( t p]iod 0 h>dly m ?an a small pony4 ,illu/ration3 ,a ,plei/oc5e ,horse ( ! ,texas ,pla9s 7,equus scotti7 ,hipp>ion & ,protohippus1 liv+ dur+ ,upp] ,mioc5e & ,plioc5e "t1 repres5t lat] /ages ( ! ?ree-to$ condition4 ,! side toes 7 completely =m$ b greatly %ort5$1 only ! c5tral toe t\*+ ! gr\nd4 ,9 "s ( ! species ! out] toes _h also become v sl5d]1 approa*+ ! spl9t condition4 ,by ?is "t ! mol> tee? 7 long] & bett] adapt$ = fe$+ on grasses :i* 7 becom+ suffici5tly abundant to attract "s ( ! =e/ dwell]s into ! op5 c\ntry4 ,dur+ ! ,plioc5e p]iod1 9 ! g5us ,pliohippus & also 9 ,hipp>ion1 ! feet 7 f> advanc$ 9 /ructure1 ) mo/ ( ! species s+le-to$1 ! side digits hav+ rea*$ ! spl9t /age4 ,plei/oc5e horses ( ! g5us ,equus1 l liv+ species ( t g5us1 7 /rictly "o-to$ animals1 rang+ ov] grassy areas & highly specializ$ = a life 9 t k9d ( environm5t4 ,specialization is to be not$ p>tly 9 ! foot & leg /ructures :]e ! modifications h contribut$ to great] spe$ & travell+ ability4 ,?is is ( great s]vice to an animal ( ! pla9s :]e food & wat] are (t5 sc>ce1 & great di/ances frequ5tly h to be cov]$ 9 ord] to obta9 su/5ance4 ,! horse1 z we "k x1 is built = spe$1 its limbs & feet be+ elongat$ to p]mit a great] /ride1 & also modifi$ to decrease ! weight )\t loss ( /r5g?4 ,! ord9>y ball-&-socket jo9t is replac$ by a pulley-l con/ruction :i* limits ! direction ( movem5t b provides an excell5t me*anism = locomotion1 especially ov] flat1 op5 gr\nd4 ,flexibility 9 o!r directions is sacrific$ = great] /r5g?1 & ! foot incid5tally becomes less suit$ = o!r purposes4 ,?is is :at is meant by 8specialization0--a dep>ture f 8g5]alization40 ,! /udy ( fossils provides num]\s illu/rations ( specializ$ developm5t :i* contributes greatly to an int]e/ 9 prehi/oric life4 ,any specializ$ /ructure or habit :i* increases fitness = a p>ticul> way ( liv+ is also kn[n z an 8adaptation40 ,q 9 l9e ) ! idea ( specialization & adaptation is ! *ange :i* occurr$ 9 ! con/ruction ( ! horses' tee?1 = ! d5tal equipm5t ( ! mod]n graz+ animals diff]s widely f t ( ! br[s+ creatures :i* liv$ on ! s(t leaves & o!r plant sub/ances ( ! =e/s4 ,illu/ration3 ,! ,/ructure ( ,mol> ,tee? ,! l>ge l[] mol> ( a long-jaw$ ma/odon %[s worn & unworn cusps1 ) ! enamel lay] =m+ a heavy bord] ar\nd ! c5tral d5t9e :]e ! surface cov]+ has be5 worn ?r\gh4 ,9 ! gr9d+ tee? ( rh9oc]oses 7illu/rat$ at ! "r7 ! cr[n patt]n is q diff]5t1 b bo? types are adapt$ = s(t] foods & are simil> 9 hav+ ! protective enamel on ! outside only4 ,! c5tral too? %[s ! condition aft] ! %all[ surface depressions h be5 remov$ by we>4 ,! *eek tee? or gr9d+ equipm5t ( ! horses und]w5t z complete a *ange z ! feet4 ,modification result$ 9 a new type ( too? :i* enabl$ h]bivor\s animals to take advantage ( a k9d ( vegetation :i* 0 late 9 arriv+ & has s9ce become ! pr9cipal diet ( ! ungulates4 ,! grasses are co>se & h>% z comp>$ ) ! leaves ( =e/ %rubb]y1 requir+ m ?or\gh gr9d+ to make !m dige/ible4 ,9 addition !y conta9 m9ute p>ticles ( silica1 :i* is a highly abrasive m9]al t quickly we>s d[n ! too? sub/ance1 especially ! s(t] mat]ials f\nd 9 too? con/ruction4 ,an increase 9 ! l5g? ( ! too? w\ld (fset ! excessive we> b w\ld n necess>ily produce a bett] me*anism = gr9d+4 ,! fulfillm5t ( ! new requirem5ts is to be se5 9 ! *ange f :at is kn[n z ! l[-cr[n$1 br[s+ type ( mol>1 to ! high-cr[n$1 graz+ type4 ,details ( ! *anges t may be trac$ ?r\gh millions ( ye>s ( gradual adju/m5t become app>5t only f ! exam9ation ( a great deal ( fossil mat]ial4 ,z comp>$ ) e>li] types ( con/ruction1 a mod]n mol> too? may appe> extremely complicat$1 b ! process :i* br\ght ab\t ! improv$ quality is v simple4 ,a little discussion ( too? /ructure1 h[ev]1 is requir$ to make ?is cle>4 ,a too?1 z ev]yone kn[s1 is p>tly imb$d$ 9 ! jaw1 p>tly expos$ outside ! gum4 ,9 a %ort-cr[n$ too? ! expos$ portion is kn[n z ! cr[n1 & ! "p imb$d$ 9 ! jaw consi/s ( "o or m roots :i* are comp>atively long4 ,! cr[n is ne>ly always protect$ by a ?9 lay] ( h>d enamel4 ,9 a gr9d+ too?1 ! work+ surface has a numb] ( m or less prom95t elevations kn[n z cusps4 ,! enamel lay] completely cov]s ?is surface until we> beg9s4 ,z ! too? goes into s]vice ! signs ( use beg9 to appe>2 ! enamel is soon worn f ! tops ( ! cusps1 & ! und]ly+ sub/ance1 call$ d5t9e1 becomes expos$4 ,?is is f> less resi/ant to we>1 & z ! enamel cont9ues to be r$uc$ ! too? becomes less effici5t z a gr9d+ device1 p>tly because ( ! smoo?+ (f ( ! surface1 p>tly because ( ! relative s(tness ( ! inn] mat]ial :i* is be+ expos$ 9 increas+ quantity4 ,a v old mol> too? ( ! l[-cr[n$ type has a smoo? surface f :i* almo/ ! la/ trace ( ! enamel has be5 remov$4 ,9 _m prehi/oric animals ! enamel is ( a d>k] color ?an ! d5t9e or cem5t1 ?is diff]5ce 9 color enabl+ "o to see at a glance h[ ! tee? are con/ruct$4 ,illu/ration3 ,graz+ ,type ( ,mol> ,tee? ,! side view ( ! bison's mol> & premol> equipm5t illu/rates ! elongat$ con/ruction :i* is common among graz+ animals4 ,9 ! patt]n ( ! gr9d+ surface may be se5 a cross section ( ! enamel lay]s4 ,"o lay] surr\nds ea* too? :ile two fold$ 8cyl9d]s0 ( ! same mat]ial occupy ! int]ior4 ,9 a long-cr[n$ too? ! roots are usually v %ort1 = mu* ( ! cr[n itself is imb$d$ 9 jaw bone1 & ! long] roots are n requir$4 ,gr[? ( ! too? is usually complet$ aft] a few ye>s2 !n z x is gradually worn away x is cont9u\sly mov$ upw>d by ! production ( new bone "u ! roots1 :i* sl[ly fills ! bottom ( ! socket & cont9ues to provide ! necess>y support4 ,an equally important diff]5ce betwe5 ! two types ( tee?1 h[ev]1 is to be se5 9 ! arrangem5t ( ! enamel1 ! long-cr[n$ type be+ provid$ ) ?is durable sub/ance on ! inside ( ! cr[n in/ead ( hav+ a m]e protective cap on ! outside4 ,! m complicat$ /ructure 0 develop$ f ! simpl] =m by ! easy me?od ( deep5+ c]ta9 depressions locat$ betwe5 cusps at ! top ( ! too?4 ,z ! cr[n ( ! too? increas$ its l5g? ^! depressions rema9$ tuck$ 91 & ev5tually became deep pits r\ghly cyl9drical 9 %ape4 ,9 addition to ! enamel & d5t9e1 a ?ird too? sub/ance1 kn[n z ! cem5t1 made its appe>ance at ab\t ?is "t1 & we f9d t quantities ( ?is new mat]ial 7 deposit$ outside ! cr[n enamel & also inside ! enamel walls ( ! pit1 9 ?is way produc+ a firmly consolidat$ /ructure o!rwise weak5$ by deep *annels & holl[ pockets4 ,! cem5t diff]s only slightly f ! d5t9e b is deposit$ :ile ! uncut too? is 9 ! gum tissues ( ! m\?1 ! enamel & d5t9e elem5ts be+ =m$ e>li] 9 ! embryonic too? be=e x em]ges f ! jaw bone4 ,a too? con/ruct$ by su* a process1 if cross-section$ ?r\gh ! cr[n1 w be f\nd to consi/ ( successive lay]s ( h>d & s(t] mat]ials4 ,9 liv+ animals ! top ( ! too? soon we>s (f & ! enamel lay]s /& 9 high] relief because ( _! great] resi/ance to we>4 ,a r\gh5$ surface ( excell5t gr9d+ quality is ?us provid$1 & z long z ! we> cont9ues !re rema9s ! same relative am\nt ( enamel to reta9 ! r\ghness1 & resi/ abrasion4 ,among ! v>i\s types ( graz+ animals !re is a m>k$ diff]5ce 9 ! arrangem5t & =m ( ! enamel lay]s4 ,)9 a species ( g5us1 h[ev]1 ! complicat$ enamel patt]ns ( ! mol> tee? are consi/5tly simil>4 ,9 ! case ( horses especially1 ^! patt]ns provide a mo/ helpful key to ! id5tification ( ext9ct =ms4 ,! g5]al patt]n1 9 any ( ! m mod]n horses1 may be und]/ood m readily if ! wavy enamel lay]s be reg>d$ z =m+ a set ( cyl9d]s ) deeply cr9kl$ walls4 ,ne> ! out] bord] ( ! too?1 surr\nd$ by a ?9 lay] ( cem5t1 is ! enclos+ cyl9d] :i* repres5ts ! enamel cap ( ! old-fa%ion$1 l[-cr[n$ too?4 ,inside ( ?is is ! c5tral mass ( d5t9e :i* has be5 p5etrat$ by two ( ! deep pits previ\sly m5tion$4 ,! orig9al enamel cap has be5 depress$ into ^! pits1 =m+ two inn] cyl9d]s :i* are fill$ ) cem5t4 ,in/ead ( be+ circul> 9 outl9e1 :5 ! cap is worn ?r\gh at ! gr9d+ surface ^! inn] cyl9d] walls are se5 to be wr9kl$ & fold$ s z to produce a mo/ irregul> patt]n4 ,h[ev]1 if sev]al tee? ( ! same k9d ( horse are comp>$1 x w be f\nd t ! edges ( ^! cyl9d]s produce figures :i* are rem>kably uni=m & *>act]i/ic = t species4 ,illu/ration3 ,am]ican ,ma/odon 7,ma/odon am]icanus7 ,a true ma/odon ( ! %ort-jaw$ type4 ,,ma/odons ,,& ,,mammo?s ,elephant-l mammals bo? liv+ & ext9ct are class$ toge!r 9 a s+le ord] be>+ ! "n ,proboscidea4 ,liv+ memb]s ( ! gr\p are ! elephants1 ( :i* ! l>ge ,indian & ,african species are be/ kn[n4 ,among prehi/oric repres5tatives ! mo/ frequ5tly m5tion$ 9 ! popul> lit]ature ( ,nor? ,am]ican animals are ! foll[+3 ,! ,am]ican ,ma/odon1 an immigrant f ,sib]ia :i* rang$ ov] ne>ly all ( ! ,unit$ ,/ates & ,canada4 ,x 0 pr9cipally a =e/ dwell]1 r>ely f\nd 9 pla9s regions1 0 abundant dur+ ! ,plei/oc5e p]iod & may h be5 kn[n to ! e>ly ,am]ican ,indians2 ,! ,woolly ,mammo?1 :i* 0 ab\t n9e feet tall4 ,x rang$ ov] ,briti% ,columbia into ! ,unit$ ,/ates & across to ! ,atlantic1 disappe>+ 9 late ,plei/oc5e "t2 ,! ,columbian ,mammo?1 ab\t elev5 feet tall1 liv$ 9 ! e>ly half ( ! ,plei/oc5e p]iod1 rang+ ov] ! w>m] portions ( ,nor? ,am]ica1 includ+ practically all ( ! ,unit$ ,/ates & mu* ( ,mexico2 ,! ,imp]ial ,mammo?1 rea*+ a height ( m ?an ?irte5 feet1 & becom+ ext9ct 9 ! ,middle ,plei/oc5e4 ,x 0 a we/]n =m1 rema9s be+ f\nd f ,nebraska to ,mexico ,city4 ,orig9ally plac$ 9 ! g5us ,elephas1 ! mammo?s are ref]r$ to commonly z elephants1 ?\gh te*nically !y %\ld n be reg>d$ z su*4 ,rec5t explorations & rese>*es h add$ greatly to our k ( ^! animals b h also caus$ mu* confusion ) reg>d to sci5tific names1 = _m new subdivisions ( ! l>g] gr\p are n[ recogniz$1 & x has become necess>y to *ange "s ( ! old] nom5clature4 ,illu/ration3 ,a ,long-,jaw$ ,ma/odont 7,trilophodon phippsi74 ,"o ( ! ,e>ly ,am]ican ,proboscideans ,! l>ge mammo? exhibit$ by ! ,museum be>s ! impressive "n ( ,ar*idiskodon m]idionalis nebrasc5sis4 ,fifty ye>s ago x might h be5 id5tifi$ simply z a specim5 ( ! imp]ial elephant & 9 su* case w\ld h receiv$ ! old "n ( t species1 :i* 0 ,elephas imp]ator4 ,b late 9 ! la/ c5tury x 0 propos$ t ! mammo?s be recogniz$ by "s o!r "n to di/+ui% !m m %>ply f liv+ elephants4 ,! "n sugge/$ = ! new g5us ?us e/abli%$ 0 ,ar*idiskodon1 9 recognition ( ! m ar*aic or primitive con/ruction ( ! enamel plates 9 ! mammo?s mol> tee?4 ,! specific "n1 m]idionalis1 _h be5 giv5 to a k9d ( mammo? :i* is well kn[n f ! s\!rn "p ( ,europe1 & ! ,lat9 "n1 signify+ 8s\!rn10 _h be5 appli$ to diff]5tiate ?is species f ! nor!rn or woolly mammo?4 ,?is mammo?1 h[ev]1 _h disappe>$ f s\!rn ,europe & = _m ye>s its subsequ5t hi/ory rema9$ a my/]y4 ,! late ,dr4 ,h5ry ,fairfield ,osborn _h be5 engag$ 9 an ext5sive /udy ( ! subject1 & :5 ! ne>ly p]fect skeleton f ,angus1 ,nebraska1 0 br\ght to 8 att5tion he recogniz$ x z be+ closely relat$ to m]idionalis1 & consid]$ x to be a record ( ! migration ( t species into ,nor? ,am]ica4 ,because ( m9or v>iations f ! typical mammo? ( s\!rn ,europe he reg>d$ x z a v>iety or subspecies :i* _h desc5d$ f ! latt]1 & ! subspecific "n1 nebrasc5sis1 0 add$ to take c>e ( ?is situation1 us+ a ,lat9iz$ =m ( ! "n ( ! ,/ate 9 :i* ! skeleton 0 f\nd4 ,) ! k we n[ h ( ^! mammo?s x becomes app>5t t ,ar*idiskodon m]idionalis nebrasc5sis is an ance/or ( ! imp]ial mammo?1 curr5tly kn[n z ,ar*idiskodon imp]ator1 & n id5tical ) x4 ,?is in/ance is typical ( ! mann] 9 :i* prehi/oric animals obta9 _! names4 ,al?\gh giv5 a ,lat9 =m1 ^! te*nical names are d]iv$ f _m languages1 & ! root words are appli$ ) ref]5ce to any?+ t happ5s to appeal to ! au?or z significant4 ,consequ5tly !re is seldom a "n ( ?is k9d :i* may be translat$ directly into natural hi/ory or sci5ce4 ,x is a mi/ake to believe t ^! /range phrases conceal important te*nical in=mation :i* is available only to ^? :o are famili> ) dead & =eign languages4 ,actually !y conta9 no?+ ( ! sort1 & ! mo/ enlight5$ ( ! ,greeks & ,romans c\ld n f9d x !re4 ,:5 a "n is ne$$ !re is none bett] ?an ! "o provid$ by ! speciali/ :o is skill$ 9 ! bus9ess ( nam+ ?+s4 ,"s te*nical ability is requir$1 to apply ! "n :]e x prop]ly belongs1 b te*nical k is n obta9$ f su* s\rces4 ,names1 9 any =m1 h ano!r purpose to s]ve4 ,!re is no magic 9 !m & !re ne$ be no my/]y ab\t !m4 ,illu/ration3 ,mol> ,too? ( ,mammo? ,?is type ( too? is con/ruct$ = long cont9u$ use & w )/& ! we> ( m abrasive foods4 ,! position ( ! :ite enamel plates is se5 9 ?is view ( ! gr9d+ surface4 ,^! plates ext5d all ! way to ! base ( ! too?1 :i* is ( ! long-cr[n$ v>iety & n to be de/roy$ by ! we>+ away ( a s+le outside lay] ( enamel4 ,o!r specim5s 9 ! ,museum collection are ! long-jaw$ ma/odonts1 s nam$ because ( ! elongat$ jaws & protrud+ *9 :i* is (t5 mi/ak5 = a tusk4 ,e>ly memb]s ( ?is gr\p _h m *eek tee? ?an lat] types ( ma/odons1 & long] jaws 7 requir$ = _! accommodation4 ,"s ( !m _h flatt5$ l[] tusks :i* evid5tly 7 us$ = digg+ purposes4 ,^! are popul>ly kn[n z 8%ovel tusk]s40 ,! m mod]n ,am]ican ma/odon _h %ort] jaws &1 l ! mammo?s & elephants1 only "o pair ( tusks4 ,bo? ! long-jaw$ & %ort-jaw$ types are repres5t$ by complete skeletons1 & also by tusks1 jaws1 & tee? ( _m individuals4 ,! ,am]ican ma/odons & ma/odonts 7 ( ab\t ! same size z ! small] mammo?s4 ,! diff]5ce betwe5 ma/odons & mammo?s is mo/ readily recogniz$ 9 ! /ructure ( ! gr9d+ tee?1 ! mol>s & pre-mol>s4 ,9 ! ma/odon ^! tee? are ( ! %ort-cr[n$ type1 :ile 9 ! mammo?s1 z 9 ! mod]n elephants1 !y are long-cr[n$4 ,! diff]5ce betwe5 ^! two types ( mol>s has be5 describ$ ) ref]5ce to horses1 & ! *ange f ! old] to ! mod]n =m may be reg>d$ z com+ ab\t 9 ! same g5]al way1 ?r\gh a s]ies ( gradual modifications4 ,9 bo? horse & mammo? ! f9al developm5t %[s int]nal enamel ext5d+ f ! gr9d+ surface ne>ly to ! roots4 ,o!rwise1 h[ev]1 !re is almo/ no resemblance1 = ! mammo? too? is made up ( flatt5$ enamel plates1 ! numb] ( :i* is v>iable = diff]5t species4 ,9 ! jaws ( a v "y individual ^! plates may be se5 z sep>ate p>ts4 ,z ! too? cont9ues to gr[1 ! plates become cem5t$ toge!r1 & :5 ! ends ( ! plate are worn d[n x may be obs]v$ t ea* consi/s ( a lay] ( enamel surr\nd+ a flat c5tral core ( d5t9e4 ,! type ( con/ruction is r m obvi\s 9 ! mammo? too? ?an 9 t ( a horse1 p>tly because ( ! l>g] size1 & p>tly because ( ! relative simplicity ( con/ruction4 ,! e>li] hi/ory ( ! ,proboscidea is n record$ 9 ! rocks ( ,nor? ,am]ica1 = ! gr\p 0 ( ,african orig9 & its migrations did n ext5d z f> z ! ,new ,_w until middle ,c5ozoic times4 ,! ma/odons & mammo?s 7 ! l>ge/ ( l& animals s9ce ! ,age ( ,reptiles1 b _! ,old ,_w ance/ors 7 n conspicu\s because ( _! bulk4 ,_m ( ^! anci5t =ms1 ev5 9 ! e>lie/ /ages1 reveal "s ( ! prom95t *>act]s t dom9ate ! entire gr\p4 ,none ( !m1 h[ev]1 %\ld be reg>d$ z a m9iature mammo? or ma/odon1 = ^! highly specializ$ types 7 p]fect$ only at a comp>atively rec5t date1 & by a process t works v sl[ly4 ,among ! e>li] =ms !re 7 also "s oddities :i* fail$ to survive or to produce a successful bran* ( ! /ock su* z ! elephants4 ,illu/ration3 ,nebraska ,mammo? 7,ar*idiskodon m]idionalis nebrasc5sis7 ,! e>lie/ kn[n memb] ( ! ord] 0 ,mo]i!rium1 an animal ( ! size ( a tapir1 liv+ 9 ,egypt dur+ ! late ,eoc5e & e>ly ,oligoc5e "t4 ,at ?is /age ! *>act]i/ic specializations lead+ to ! ma/odons & mammo?s 7 app>5t b n f> advanc$4 ,! proboscis 0 probably mu* l ! flexible sn\t ( mod]n tapirs1 = ! ne$ ( a long trunk _h n yet arriv$4 ,9 upp] & l[] jaws ! second pair ( incisor tee? 7 becom+ l>ge & prom95t4 ,! enorm\s tusks ( ! mammo?s lat] develop$ f ! enl>gem5t ( ! same pair ( upp] incisors1 & 9 "s ( ! long-jaw$ ma/odonts ! l[] pair also produc$ l>ge tusks1 ?\gh frequ5tly ! l[] tusks 7 n prom95t4 ,d9o!rium _h d[nw>d-gr[+ tusks 9 ! l[] jaws1 none 9 ! upp]4 ,?is g5us 0 fairly common 9 ! ,mioc5e ( ,europe1 ,asia1 & ,africa4 ,9 ! tropics x surviv$ ?r\gh\t ! ,plioc5e & possibly into ! ,plei/oc5e4 ,"s ( ! species acquir$ ! size ( elephants1 b x is app>5t t !y 7 n ance/ral to any ( ! m progressive types4 ,!y are to be reg>d$ r z an (f%oot f ! ma9 l9e ( desc5t4 ,9 #ahei only t5 species ( ! elephant-l mammals 7 kn[n1 & all 7 ref]r$ to a s+le g5us4 ,at ! pres5t "t elev5 g5]a appe> to be well f\nd$1 & ! numb] ( recogniz$ species has rea*$ a hundr$1 if x has n already pass$ t figure4 ,new discov]ies are expect$ to add to ! exi/+ total4 ,) ?is mass ( mat]ial be=e u we note c]ta9 def9ite tr5ds among ! m progressive types4 ,! increas+ weight 0 accompani$ by ! developm5t ( /rong1 upright limbs 9 :i* ! bones h a column> position in/ead ( ! angul> assembly :i* prevails among mo/ ( ! mammals4 ,z ! tusks increas$ 9 size !re 0 a %ort5+ ( bo? skull & neck to br+ ! weight clos] to ! po9t ( support4 ,! front tee? disappe>$ except ! second pair ( upp] incisors :i* rema9 z tusks 9 ! mod]n elephant4 ,! *eek tee? pres5t 9 ! %ort5$ jaws ( ! mammo? 7 r$uc$ to "o pair at a "t 9 ! upp] set & ano!r pair bel[4 ,f a simple1 l[-cr[n$ orig9 ^! gr9d+ tee? develop$ into ! m successful high-cr[n$ patt]n ) num]\s plates ( enamel inside4 ,a preh5sile upp] lip acquir$ ! l5g? & usefulness ( ! elephants trunk4 ,illu/ration3 ,ran*o la ,brea ,fossils ,"o ( ! mo/ unusual ( ! _m animals t h be5 tak5 f ! t> pits is ! l>ge gr\nd slo?1 se5 at ! left 9 ?is gr\p4 ,su* slo?s 7 v abundant dur+ ,plei/oc5e "t1 & "s may h liv$ up to a few ?\s& ye>s ago4 ,ar*aeologi/s h f\nd indications t ^! creatures may h be5 hunt$ by cave-dwell+ peoples ( ! ,am]ican ,s\?we/4 ,o!r skeletons include ! sab]-too? tig]1 *>act]iz$ by ! long curv$ upp] can9e tee? :i* und\bt$ly 7 us$ = /abb+ & sla%+1 & ! dire wolf1 ! small] ( ! two :i* are fac+ ! slo?4 ,! arti/'s recon/ruction ( ?is sc5e also %[s ! great vulture1 ,t]atornis1 :i* is ! l>ge/ kn[n bird ( flight4 ,ov]-specialization 9 ! production ( tusks appe>s to h be5 ! pr9cipal factor 9 ! d[nfall ( ! mammo?s4 ,! l>ge size ( ! animals & ! difficulties ( f9d+ suffici5t food to su/a9 life mu/ h be5 a s]i\s h&icap at times1 b _! ability & incl9ation to travel ov] long di/ances enabl$ "s ( !m to f9d tol]able liv+ conditions until ! end ( ! ,glacial ,p]iod4 ,!y are n[ ext9ct & ! ne>e/ liv+ relatives are ! elephants1 some:at r$uc$ 9 size ( tusks & body b o!rwise v simil>4 ,!re are _m o!r tribes ( mammals ^: anci5t hi/ory is p>tially kn[n ?\gh brok5 by p]iods ( "t = :i* !re is no fossil evid5ce4 ,all h und]gone *anges 9 :i* v>i\s =ms & degrees ( specialization are featur$2 ?is g5]al process is be/ reveal$ by ! horses & elephant-l animals :i* h left a cle>] record4 ,= o!r gr\ps ! /ory w\ld diff] b little except z to names & specific details4 ,,! ,,ran*o ,,la ,,brea ,,fossil ,,pits ,! ,la ,brea t> pits1 z !y are (t5 call$1 provide a rem>kable record ( ,plei/oc5e life 9 s\?we/]n ,nor? ,am]ica4 ,scatt]$ ov] an area ( ab\t ?irty acres j (f ,wil%ire ,b\lev>d 9 ,los ,angeles1 ^! bone deposits 7 kn[n1 z f> back z #ahge1 to conta9 ! rema9s ( prehi/oric animals4 ,x 0 n until #aije1 h[ev]1 t _! value 0 recogniz$ by paleontologi/s4 ,9 t ye> ! ,univ]sity ( ,cali=nia began an inve/igation1 & excavations 7 c>ri$ on at int]vals by v>i\s in/itutions dur+ ! next t5 ye>s4 ,a great deal ( mat]ial 0 acquir$ by ! ,los ,angeles ,museum ( ,hi/ory1 ,sci5ce1 & ,art1 :]e _m skeletons1 skulls1 & o!r int]e/+ specim5s h be5 plac$ on exhibition4 ,! pits h ! =m ( small crat]s =m$ by ! seep+ ( oil f ! und]ly+ rocks4 ,! seeps appe> to h be5 active dur+ "p ( ! ,plei/oc5e p]iod b app>5tly n at ! beg9n+4 ,! oil is ri* 9 asphalt :i* has s]v$ z a pres]vative = ! bones1 & ow+ to its /icky prop]ties has be5 an effective animal trap = ?\s&s ( ye>s4 ,! fossil b$s at pres5t are ( oil-soak$ e>? & s&4 ,9 pa/ times !re mu/ h be5 a great] p]c5tage ( oil1 (t5 conceal$ by a lay] ( du/ or pools ( wat]4 ,! l>ge numb] ( c>nivor\s animals f\nd 9 ! deposits sugge/s t !y 7 attract$ by ! cries & /ruggles ( creatures w&]+ c>elessly into ! asphalt & s]v+ z live bait to keep ! traps 9 cont9u\s op]ation4 ,animals f\nd !re include _m species /ill liv+ 9 ! locality1 "s t h migrat$ to o!r t]ritory1 & a l>ge numb] t h become ext9ct4 ,among ! latt] may be m5tion$ species t diff] b slightly f liv+ relatives1 o!rs t h left no desc5dants4 ,horses1 bison1 & wolves1 ?\gh ext9ct species1 7 ( relatively mod]n types4 ,on ! o!r h& ! l>ge slo?s & sab]-too? cats seem r out ( place4 ,true cats are repres5t$ by ! m\nta9-lion1 bob-cat1 & a species ( lion :i* is ne>ly "o-f\r? l>g] ?an any ( ! great cats ( ! ,old ,_w4 ,a long-legg$ camel1 ) a height ( approximately eight feet to ! top ( ! head1 0 among ! native animals ( ! di/rict4 ,skunks1 weasels1 badg]s1 squirrels1 rabbits1 be>1 de]1 & antelope 7 m or less abundant4 ,! ,la ,brea gr\p exhibit$ by ! ,d5v] ,museum ( ,natural ,hi/ory includes ! foll[+ species3 horse 7,equus occid5talis71 bison 7,bison antiquus71 wolf 7,a5ocyon dirus71 sab] too? 7,smilodon cali=nicus71 slo? 7,mylodon h>lani74 ,horses _h entirely disappe>$ f ! ,nor? ,am]ican cont95t by ! "t ! fir/ :ite man arriv$4 ,equus occid5talis 0 "o ( ! sev]al species liv+ dur+ ! ,plei/oc5e p]iod1 ?is "o app>5tly be+ re/rict$ to ,cali=nia & p]haps adjac5t /ates4 ,bison antiquus 0 slightly l>g] ?an ! pla9s bison ( rec5t times & _h x horns set at a *>act]i/ic diff]5t angle4 ,! species 0 fir/ describ$ f ,k5tucky & appe>s to h _h a wide di/ribution4 ,! wolves 9 ?is gr\p are ab\t ! size ( timb] wolves1 b h heavi] skulls ) less bra9 capacity1 massive tee? especially adapt$ to bit+ & cru%+ l>ge bones1 & limbs ( r light con/ruction4 ,!y probably assembl$ 9 packs :]e meat 0 abundant &1 hunt+ 9 ?is fa%ion1 7 able to attack & ov]come ! l>g] ungulates & ed5tates4 ,to mo/ visitors ! l>ge gr\nd slo? is ! mo/ int]e/+ animal ( ! gr\p4 ,?is ed5tate animal is %[n at ! edge ( ! pool ) "o foot /uck 9 ! 8t>40 ,! ed5tates are a gr\p ( primitive animals ) v simple tee?1 if any4 ,tee? are usually lack+ 9 ! front "p ( ! m\?1 sometimes entirely abs5t1 z among anteat]s4 ,bett] kn[n liv+ repres5tatives ( ! gr\p are ! tree slo?s1 armadillos1 & anteat]s ( ,s\? ,am]ica4 ,gr\nd-slo?s 7 prom95t among ,s\? ,am]ican mammals dur+ mu* ( ,c5ozoic "t4 ,dur+ ,plioc5e & ,mioc5e "t !re 0 a m>k$ t5d5cy to l>ge size1 & x 0 pr9cipally dur+ ^! two p]iods t !y appe>$ 9 ! ,unit$ ,/ates area4 ,mylodon 0 "o ( ! l>g] ,nor? ,am]ican gr\nd-slo?s4 ,its tee?1 )\t ! protective enamel :i* is pres5t among high] mammals1 are re/rict$ to ! *eek region1 & h ! =m ( simple pegs2 in/ead ( be+ specializ$ !y /& close to ! extreme ( g5]alization4 ,! con/ruction ( ! entire skeleton is massive1 sugge/+ great /r5g? ) sl[ movem5ts4 ,! h&s are well develop$1 provid$ ) /\t claws1 & mu/ h s]v$ ! creature well z protection aga9/ attacks by pr$atory neighbors4 ,we h "s idea z to :at caus$ ! ext]m9ation ( ! gr\nd-slo?s 9 ?is p>ticul> region1 b ! complete disappe>ance ( su* a l>ge & widely di/ribut$ gr\p at ! close ( ! ,plei/oc5e p]iod is a my/]y t may nev] be expla9$4 ,illu/ration3 ,! ,folsom1 ,new ,mexico1 ,bison 7,bison taylori7 ,! sab]-too? cat1 sometimes ref]r$ to z a tig]1 0 specializ$ z a meat eat] ?\gh h>dly z a hunt+ animal4 ,9 ! ,la ,brea region its pr9cipal food 0 probably ! fle% ( ! sluggi% gr\nd-slo?s4 ,! size 0 equal to t ( ! ,african lion1 ) h9d limbs slightly long] & ! front legs m p[]fully develop$4 ,! mo/ rem>kable *>act]i/ic is to be f\nd 9 ! developm5t ( ! upp] can9e tee? & modifications ( ! skull :i* 7 necess>y to enable ! animal to use ^! tee? z weapons4 ,9 ord] to make ! 8sab]s0 effective x 0 necess>y to get ! l[] jaws out ( ! way1 & ?is 0 provid$ = 9 an unusual type ( h+e :i* enabl$ ! m\? to op5 wid] ?an is possible 9 ! case ( ! less specializ$ c>nivores4 ,judg+ by all ! /ructural features ( ! skeleton1 ,smilodon c\ld n h liv$ well on small animals1 = x 0 n equipp$ to capture t k9d ( prey4 ,x is evid5t t l>ge mammals 7 pref]r$1 & t ! me?od ( attack 0 to spr+ ^u ! victim & cl+ !re ) ! p[]fully develop$ =e limbs until ! kill 0 complet$ by /abb+ into a vuln]able spot4 ,t ! position ( ! l>ge sab]s ne> ! front ( ! m\? int]f]$ ) normal fe$+1 is a reasonable conclusion4 ,!re are also anatomical features :i* lead to ! belief t ?is c>nivore 0 a blood suck]1 p]haps m ?an x 0 meat-eat]4 ,if mo/ ( ^! conclusions are correct we h "h ano!r case ( ov]-specialization & a possible explanation ( ! ext9ction ( two species4 ,su* evid5ce z we h is f> f conclusive1 = !re is no pro( t ,ran*o ,la ,brea 0 ! la/ /& ( ei!r ! sab]-too? or ! gr\nd-slo?4 ,bo? races 7 widely di/ribut$ & _! liv+ conditions c\ld n h be5 exactly duplicat$ 9 o!r localities4 ,x has be5 sugge/$1 h[ev]1 t ,smilodon ate ! la/ ( ,mylodon1 & />v$ soon aft]w>d because x _h become unable to p>take ( o!r foods4 ,! conjecture is (f]$ = :at x is wor?1 toge!r ) ! facts on :i* ! /ory has be5 bas$4 ,! geological record = ,plei/oc5e "t is n z complete z "o might imag9e4 ,num]\s localities h produc$ repres5tative fossils b ! yield is r>ely l>ge en\gh to solve _m ( ! riddles :i* are con/antly aris+ z inve/igation proce$s4 ,aside f ^? areas :i* bord]$ ! retreat+ ice cap & :]e liv+ conditions 7 f> f favorable1 ! s$im5t>y deposits ( ?is p]iod are n cont9u\s ov] l>ge areas4 ,_m ,plei/oc5e fossils are f\nd 9 /ream *annel b$s :i* are always subject to removal by subsequ5t floods4 ,illu/ration3 ,e>ly ,man 9 ,nor? ,am]ica ,!re is abundant evid5ce to indicate t ! great elephants ( ,plei/oc5e "t 7 hunt$ by primitive ,am]icans ^: only weapons 7 d>ts or spe>s tipp$ ) po9ts ( /one4 ,a skull & ! l[] jaws ( sev]al mammo?s are %[n "h4 ,isolat$ pat*es ( fossil-be>+ s$im5ts frequ5tly record ! migration ( animals 9 unmi/akable t]ms1 b ! details ( ! w&]+s & ! conditions enc\nt]$ 9 ! newly e/abli%$ habitats are (t5 left 9 d\bt4 ,to correlate ! facts reveal$ at "o locality ) f9d+s at o!r places &1 if possible1 to date all prehi/oric ev5ts ) a great] degree ( accuracy are among ! major tasks ( curr5t inve/igations4 ,,! ,,age ,,( ,,man ,! ,plei/oc5e or 8,ice ,age10 & ! ,rec5t p]iod 9 :i* we are liv+ at ! pres5t mom5t are n %>ply sep>at$ by any ev5t readily recogniz$ or dat$1 & ! two comb9$ are ( v %ort duration z comp>$ ) o!r p]iods m cle>ly e/abli%$ by ! pass+ ( c5turies4 ,toge!r !y comprise ! ,age ( ,man z commonly recogniz$1 ) ab\t a million ye>s repres5t+ ! ,plei/oc5e p]iod1 "s t5 to tw5ty ?\s& ye>s ! ,rec5t4 ,:5 geologi/s ( ! n9ete5? c5tury sugge/$ t ! com+ ( man %\ld be reg>d$ z ! beg9n+ ( a new era1 ! "n ,psy*ozoic 0 propos$1 & to "s ext5t ?is t]m has be5 appli$ to ! pres5t p]iod4 ,m 9 keep+ ) o!r p]iod names is ,holoc5e1 mean+ entirely rec5t4 ,common usage1 h[ev]1 applies ! simple t]m ,rec5t to ?is unf9i%$ *apt] :i* is also )\t a cle>-cut beg9n+4 ,zoologically1 man is m]ely "o ( ! creatures t arriv$ 9 ! c\rse ( "t1 along ) o!r mammals4 ,j :5 he arriv$ & h[ he look$ at ! "t ( 8 com+ _c be det]m9$ f a /udy ( fossils4 ,p]haps x is ( no importance4 ,!re is no?+ to indicate 8 exi/5ce be=e ! ,c5ozoic1 no completely satisfactory pro( ( exi/5ce be=e ! ,plei/oc5e p]iod4 ,z ) o!r inhabitants ( ! e>?1 x is probable t he became prom95t only aft] a great deal ( competition ) o!r creatures :i* kept 8 ance/ors subm]g$ = ?\s&s ( ye>s4 ,! ,ice ,age1 ) its *eck ^u ! progress ( compet+ animals1 und\bt$ly gave him an advantage4 ,8 sup]ior m5tality enabl$ him to ov]come adv]sity by me?ods n available to o!r mammals2 8 inv5tive & me*anical g5ius mu/ h be5 greatly /r5g!n$ by 8 exp]i5ce dur+ ?is int]val4 ,at ab\t ?is po9t1 :]e prehi/ory beg9s to m]ge into hi/ory1 ! geologi/ & paleontologi/ mu/ let o!r int]pret]s c>ry on4 ,ar*eologi/s & an?ropologi/s take up ! "w1 & ?r\gh _! ef=ts _m details h be5 add$ to our k ( ! human race4 ,! /udy ( biology1 :i* is ! sci5ce ( life1 has provid$ an in/ructive viewpo9t t enables u to see ourselves aga9/ ! va/ backgr\nd built up by inve/igations into ! nature ( ! e>? & its anci5t inhabitants4 ,?is sci5ce deals ) liv+ creatures z organisms--plants & animals s organiz$ z to be capable ( exi/5ce only 9 an environm5t :i* provides exact life requirem5ts4 ,! ,age ( ,man has be5 v>i\sly *>act]iz$ z an age ( s\l1 ( high] intellig5ce1 ( culture1 & f9ally1 ( civilization1 fre$om & democracy4 ,! 8cr[n+ glory0 ( ! organic _w is pictur$ 9 hi/ory z a creature :o has busi$ himself = ?\s&s ( ye>s ) ! build+ up & te>+ d[n ( civilizations4 ,prehi/ory reveals ?is habit z some?+ unique 9 ! human "*1 = !re is no o!r organism t has specializ$ s p]si/5tly 9 ! creation ( its own environm5t1 no o!r t has _h ! comb9$ p[] & tal5t to produce s mu* *ange4 ,m ?an any?+ else1 ! prehi/oric record is a lesson 9 adaptation1 :i* 9 its broade/ s5se means fitness = life "u p>ticul> conditions1 & always subject to organic law4 ,man's ef=ts to br+ ab\t an adju/m5t betwe5 himself & 8 civilization h c5t]$ l>gely on ! me?od ( =c+ himself into ! mold t happ5s to be pres5t1 "o patt]n today1 ano!r tomorr[4 ,no creature ( ! pa/ has _h to adapt itself to any?+ s radically new or s ?or\ghly revolution>y4 ,! vital problem n[ is :e!r ?is man-made environm5t w prove helpful or disa/r\s4 ,?\gh "o ( its names is 8culture10 x has gr[n sporadically & unev5ly1 ) little evid5ce ( ! cultivation t is impli$ & requir$4 ,p>ts h be5 exp&$ to extraord9>y proportions :ile o!rs equally ess5tial h be5 ret>d$ 9 _! gr[?4 ,a m intellig5t h&l+ ( ?is environm5t factor seems to be possible1 & ! pres5t mania = 8organization0 may become temp]$ ) an awak5+ consci\sness ( organic requirem5ts :]e organism & environm5t are involv$4 ,once we grasp ! idea t 8culture0 results f man's ef=t to improve 8 liv+1 by putt+ into 8 environm5t some?+ t 0 n !re be=e--!n1 surely1 ?is hi/ory ( a billion ye>s ( liv+1 & z _m 8ways ( life10 %\ld tea* u some?+ we ought to "k z we g into an all-out endeavor to tea* a :ole _w h[ to obta9 a "o-&-only way4 ,we may /& at ! beg9n+ ( an era = :i* an appropriate "n has n yet be5 sugge/$4 ,civilization1 on ! o!r h&1 may provide only a m9or epo* to be add$ 9 "s remote "t to ! /ory ( fossils4 ,,supplem5t>y ,,read+ ,! lit]ature p]ta9+ to fossils is widely scatt]$ & usually too te*nical = ! layman4 ,x is bett] to use ! res\rces ( ! ne>e/ libr>y ?an to feel t a specifi$ li/ ( books is necess>y4 ,any textbook on geology1 zoology1 or botany w provide helpful in=mation4 ,mo/ books ( ?is type w be f\nd int]e/+ & readable if us$ to solve def9ite problems sugge/$ by ! /ud5t's imm$iate curiosity4 ,v few c be read f beg9n+ to end )\t a great deal ( ef=t & disc\ragem5t4 ,! foll[+ h be5 prom95t among ! books consult$ by ! au?or3 ,textbook ( ,geology2 by ,pirsson & ,s*u*]t4 ,?is "w has und]gone sev]al revisions & curr5tly appe>s 9 two volumes3 ,physical ,geology by ,longwell1 ,knopf1 & ,fl9t2 ,hi/orical ,geology by ,c4 ,o4 ,dunb>4 ,publi%$ by ,john ,wiley ,sons4 7,hi/orical geology cov]s ! entire range ( prehi/oric life--plant1 inv]tebrate1 & v]tebrate47 ,hi/orical ,geology 7,! ,geologic ,hi/ory ( ,nor? ,am]ica72 by ,russell ,c4 ,hussey4 ,publi%$ by ,mc,graw-,hill4 ,concise1 int]e/+1 & in=mative4 ,geology & ,natural ,res\rces ( ,colorado2 by ,r4 ,d4 ,george4 ,publi%$ by ! ,univ]sity ( ,colorado4 ,conta9s an excell5t summ>y ( ! hi/orical geology & s$im5t>y =mations ( ,colorado4 ,v]tebrate ,paleontology2 by ,alfr$ ,%]wood ,rom]4 ,publi%$ by ! ,univ]sity ( ,*icago ,press4 ,?is is "o ( ! mo/ compreh5sive & up-to-date treatm5ts ( ! subject = /ud5ts desir+ to g beyond ! elem5t>y /age4 ,a ,hi/ory ( ,l& ,mammals 9 ! ,we/]n ,hemisph]e2 by ,william ,b]ryman ,scott4 ,publi%$ by ,! ,macmillan ,company4 ,?is well-kn[n acc\nt ( liv+ & ext9ct mammals is "o ( ! favorites among /ud5ts4 ,! ,age ( ,mammals2 by ,h5ry ,fairfield ,osborn4 ,a classic 9 ?is field ( lit]ature1 b = advanc$ read+4 ,! book is n[ out ( pr9t4 ,! ,d9osaur ,book2 by ,edw9 ,h4 ,colb]t4 ,publi%$ by ! ,am]ican ,museum ( ,natural ,hi/ory1 ,new ,york4 ,an illu/rat$ /ory ( amphibian & reptilian evolution4 ,d[n to ,e>?2 by ,c>ey ,croneis & ,william ,c4 ,krumbe94 ,publi%$ by ! ,univ]sity ( ,*icago ,press4 ,an excell5t popul>ization ( ! e>? sci5ces--geology & paleontology4 ,lexicon ( ,geologic ,names ( ! ,unit$ ,/ates2 compil$ by ,m4 ,grace ,wilm>?4 ,bullet9 #hif 79 two p>ts7 ( ! ,unit$ ,/ates ,geological ,survey4 ,a ri* s\rce ( in=mation conc]n+ ! age1 "*1 & di/ribution ( geologic =mations1 ) num]\s ref]5ces to fossil-be>+ b$s4 ,bibliography ( ,nor? ,am]ican ,geology 7includ+ paleontology72 v>i\s bullet9s ( ! ,unit$ ,/ates ,geological ,survey4 ,:]e libr>y facilities provide access to ! te*nical lit]ature ( museums1 univ]sities1 & sci5tific societies1 ?is is a valuable aid 9 locat+ publications deal+ ) orig9al "w 9 paleontology4 ,bullet9s #gdf & #gdg cov] ! ye>s betwe5 #aghe & #aiah2 ,bul4 #hbc 7#aiah-aibh72 ,bul4 #icg 7#aibi-aici72 ,bul4 #ich 7#aidj-aida72 ,bul4 #idi 7#aidb-aidc72 ,bul4 #ieb 7#aidd-aide72 ,bul4 #ieh 7#aidj-aidg72 ,bul4 #ifh 7#aidh72 ,bul #igg 7#aidi74 ,prep>ation is a cont9u\s process ) rec5t bullet9s appe>+ at "o or two ye> int]vals4 ,anci5t ,man 9 ,nor? ,am]ica & ,prehi/oric ,indians ( ! ,s\?we/2 by ,h4 ,m4 ,worm+ton4 ,publi%$ by ,d5v] ,museum ( ,natural ,hi/ory1 ,city ,p>k1 ,d5v] #f1 ,colorado4 ,bo? volumes conta9 au!ntic & up-to-date acc\nts ( e>ly ,am]ican cultures4 ,,maps ,geologic ,maps4 ,unit$ ,/ates ,geological ,survey3 map ( ! ,unit$ ,/ates 7#aicb72 map ( ,colorado 7#aice74 ,geologic maps ( a few o!r /ates are available2 in=mation reg>d+ ^! may be obta9$ f /ate univ]sities or /ate geological surveys4 ,note3 ,bullet9s ( ! ,u4,s4,g4,s4 are pur*asable f ! ,sup]9t5d5t ( ,docum5ts1 ,wa%+ton1 ,d4 ,c4 ,maps are sold by ! ,director ( ! ,geological ,survey1 ,wa%+ton1 ,d4 ,c4 ,transcrib]'s ,notes --,sil5tly correct$ a few typos --,re/or$ "o accid5tal omission 9 ! ,table ( ,illu/rations --,reta9$ publication in=mation f ! pr9t$ edition3 ?is e,book is public-doma9 9 ! c\ntry ( publication4 --,9 ! text v]sions only1 text 9 italics is delimit$ by und]scores4