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Unformatted text preview: 12/19/11 Eonothem Phanerozoic Upper Paleozoic : A Buc kyball T his image depic t s a 'buc kyball' f ullerene wit h noble gas t rapped inside (Universit y of Washingt on) Reading Assignment : Chapt ers 9, and 10 Phanero oic Eonothem The Paleo oic Erathem: Lower, Middle and Upper Paleo oic T he Upper Paleozoic Biologic al F eat ures Unit (Chapt er) Plan: Geologic al F eat ures Paleont ologic al F eat ures Bac k t o Course Syllabus Visit t his web sit e: UCMP Bac k t o Course Plan (weekly sc hedule) t o review t he Hist ory of Lif e of t his int erval of t ime Biological F eatures: T he Evolut ionary Proc esses of Phanerozoic Biot a; F rom Eukaryot es t o Animalia Paleoec ology: T ypes of marine environment s Lif e of Land: T rees grew in swamps: Lyc opods www2.fiu.edu/ longoria/gly1101/UpperPz.html 1/13 12/19/11 Eonothem Phanerozoic Biologic al F eat ures of t he Carbonif erous Syst em Biologic al F eat ures of t he Permian Syst em T he Permian Mass ext inc t ion involving: F usulinids (F oraminif era), Rugose c orals, T abulat e c orals, Bryozoans, Ammonoids DVD: BBC- T he Day T he Eart h Nearly Died. Clic k here t o view a summary of t his T V program Addit ional ref erenc e on t he Permian mass ext inc t ion: Hof f mann, J.H., When lif e nearly c ame t o an end, Nat ional Geographic 198(3):100113,2000. Animals diversif ied on land and invaded f reshwat er habit at s Clic k here f or a summary of Paleozoic Bio- event s Important F acts to Remember Bac k t o Unit Plan Geological F eatures: Read Chapt ers nine and t en of your t ext book Review t he st ory of plat e t ec t onic s F or a more simplist ic model visit t his sit e <ht t p://www.pbs.org/wgbh/aso/t ryit /t ec t onic s> <ht t p://www.enc hant edlearning.c om/subjec t s/ast ronomy/planet s/eart h/Cont inent s.sht ml> Paleogeography Landmasses: Gondwanaland and Eurameric a Bac k t o Unit Plan Paleontological F eatures: Divisions of t ime Chronst rat igraphic Divisions: T he Carbonif erous Syst em T he Invert ebrat es: F usulinids (F oraminif era) Bivalves Insec t s wit h f ixed wing Insec t s wit h f oldable wings T he vert ebrat es: Amphibians T he Plant s: Coal Swamps T he Permian Syst em: Brac hiopoda snails c rinoids Early rept iles: Pelyc osaurs, T herapsids Gymnosperms Bac k t o Unit Plan Phanero oic Eonothem The Paleo oic Erathem Chronost rat igraphic Division of t he Paleozoic Erat herm Permian Syst em Pennsylvanian Upper Carbonif erous Subsyst em Sy s t e m Mississippian Eonot hem Erat hem Subsyst em Phanerozoic Paleozoic Devonian Syst em Middle Silurian Syst em Ordovic ian Syst em Lower www2.fiu.edu/ longoria/gly1101/UpperPz.html 2/13 12/19/11 Eonothem Phanerozoic C Phanero oic Eonothem: T E "V .T .T P M , C . ThePaleo oic Erathem: 543 to 248 m a T P E ( ) S L P ". O E E 543 , :P .A " " , , , , .A 90% .R , P , .T , , , B , M T P P Phanero oic, 300 .D ; N .F - A , P , , A ' S , .L P . P .F c oa l . , U .T , , M P S , P , The Upper Paleo oic = Siluarian + Dev onian S stems T M P P : S D .S C Summar of Middle Paleo oic Ev ents: C arboniferous S stem: 354 292 limestone W .T E E C C .I .I P M M C E .T P N M .T A M L V U T C P N E .T A . U P P . Biological F eatures: S , : G S , , - , .I , . O C , .T www2.fiu.edu/ longoria/gly1101/UpperPz.html 3/13 12/19/11 Eonothem Phanerozoic anc e o of bi d , mammal , and ep ile o ep od c e on land b p e en ing he de ic c a ion of he emb o in ide. T he e a al o a end o a d mild empe a e d ing he Ca bonif e o , a e idenc ed b he dec ea e in l c opod and la ge in ec and an inc ea e in he n mbe of ee f e n . Sc ale ee (lepidodend on ) g e o 35 me e (115 f ee ) f o ming den e f o e c onif e f o med and he e a a la ge a ie of f e n a g o nd le el. . T he f o e nne of T he beginning of he Ca bonif e o gene all had a mo e nif o m, opic al, and h mid c lima e h o gho he ea han e i oda . Sea on if an e e indi inc . T he e ob e a ion a e ba ed on c ompa ing he mo pholog of he plan ha e i in he f o il ec o d i h plan ha a e p e en oda . T he mo pholog of he Ca bonif e o plan e emble he plan ha li e in opic al and mildl empe a e a ea oda . Man of hem lac k g o h ing , gge ing a nif o m c lima e. T hi nif o mi in c lima e ma ha e been he e l of he la ge e pan e of oc ean ha c o e ed he en i e f ac e of he globe e c ep f o a mall, loc ali ed ec ion he e Pangea, he ma i e pe c on inen ha e i ed d ing he la e Paleo oic and ea l T ia ic , a f o ming d ing he Ca bonif e o . Shallo , a m, ma ine a e b o oan , pa ic la l f ene domina ed b b ac hiopod . T hea il a mo ed f i h f om he mode n. Coelac an h ( ee' la kan h) de eloped d ing he pe iod. of en f looded he c on inen . A ellid , e e ab ndan in hi en i ilobi e e e inc ea ingl c a c e De onian bec ame e inc , being am in eam along F o aminif e a ( in , mo l ma ine animal ha c hambe ) bec ame o ab ndan ha n me o ac hed f il e f eede ch a onmen , and he ea f loo a hile f o aminif e e e ab ndan . T he eplac ed i h f i h f a na ha look mo e i h o he l ng- f inned and lobe- f inned f i h ha e e mic o c opic o nea - mic o c opic i h hell- like lime one c e e e f o nd in Indiana. Amphibian inc ea ed in n mbe b emained a he mall. Mo e e le inc he ) long, i h he la ge g o ing o abo 2 me e (6.5 f ee ) long. Nea he end in he n mbe c inoid , bla B o oa b il of he Mi i ippian, plif of f loodplain and del a oid , c o oan , and b lac , mo - like c e han 20 c en ime e (8 and e o ion of he c on inen oc c ed, c a ing an inc ea e p e en . T he del aic en i onmen ppo f e e c o al , oan , hic h e e ab ndan ea lie in he Ca bonif e o . and e e he mo c c e f l hellf i h of he pe iod. F e h a e c lam f i appea along i h an inc ea e in ga opod, bon f i h, and ha k di e i . A fi glanc e, i ma eem ha he ma ine habi a ha g o n allo ing he di e i of ma ine lif e o inc ea e, b in ac ali , he mo emen of he c on inen o f o m one la ge c on inen al ma dec ea ed he ea c oa a ea. T he amo n of pac e a ailable f o ma ine lif e dec lined, and he ea le el all o e he o ld f l c a ed bec a e of he p e enc e of o la ge ic e hee a he o he n pole hic h c k p la ge amo n of a e and loc k i a a f om he a e c c le a ic e. Bec a e o m c h a e i aken o of he a e c c le, he ea le el d op leading o he ma e inc ion of hallo ma ine in e eb a e , he g ad al dec line of amp , and he inc ea e in e e ial habi a . T he e ef f ec a e e e ed hen he glac ie a o ec ede, elea ing he a e ha he had o ed a ic e bac k in o he oc ean , f looding he amp again and he f loodplain . Ca bonif e o oc k f o ma ion of en oc c in pa e n of ipe i h hale and c oal eam al e na ing, indic a ing he c c lic f looding and d ing of an a ea. T he plif of he c on inen c a ed a an i ion o a mo e e e ial en i onmen d ing he Penn l anian pe iod. S amp f o e a ell a e e ial habi a bec ame c ommon and ide p ead. In he amp f o e , he ege a ion a ma ked b he n me o dif f e en g o p ha ee p e en . Seedle plan c h a l c op id e e e emel impo an in hi c omm ni and a e he p ima o c e of c a bon f o he c oal ha i c ha ac e i ic of he pe iod. T he l c opod nde en a majo e inc ion e en af e a d ing end, mo likel c a ed b he ad anc e of glac ie . www2.fiu.edu/ longoria/gly1101/UpperPz.html 4/13 12/19/11 Eonothem Phanerozoic F C , .T , ' .T , , , . T .T , .F C - H , .T - , .A ( ) C , , ( , : ). T , . Permian S stem: 292 M , P . Biological F ea 251 .T P P U .I e :L .I .T .E , , , T . .T , .T , . R :L ( : ); .I , , , . T P M P E .I , , . T 75% 80% .A . S P , , . O , , "A , , www2.fiu.edu/ longoria/gly1101/UpperPz.html D ". A , .M P , .I , 5/13 12/19/11 Eonothem Phanerozoic Pe mian a he la of he ime f o a ne e he ame again. ome o gani m and a pi o al poin f o o he , and lif e on ea h Pe mian f o il ha ha e been ed a inde f o il inc l de b ac hiopod , ammonoid , f ilinid , c onodon , and o he ma ine in e eb a e . Some gene a oc c i hin c h pec if ic ime f ame ha a a a e named f o hem and pe mi a ig aphic iden if ic a ion h o gh he p e enc e o ab enc e of pec if ied f o il . See Biologic al P inc iple f o a e ie of he e c onc ep Sc hi oc oel : A g o p of animal ph la, inc l ding B o oa, B ac hiopoda, Pho onida, Sip nc loidea, Ec hi oidea, P iap loidea, Moll c a, Annelida, and A h opoda, all c ha ac e i ed b he appea anc e of he c oelom a a pac e in he emb onic me ode m. Lophopho e: A ho e hoe- haped c ilia ed o gan loc a ed nea and pho onid ha i ed o ga he f ood. he mo h of b ac hiopod , b o oan , Bac k o Uni Plan NOT ES ON T HE CLASSIF ICAT ION OF ----------------------------------------The Permian Mass E tinction- 90- 95% of ma ine pec ie bec ame e inc in he Pe mian Lif e in he Pe mian: Wi h he f o ma ion of he pe - c on inen Pangea in he Pe mian, c on inen al a ea e c eeded ha of oc eanic a ea f o he f i ime in geologic al hi o . T he e l of hi ne global c onf ig a ion a he e en i e de elopmen and di e if ic a ion of Pe mian e e ial e eb a e f a na and ac c ompan ing ed c ion of Pe mian ma ine c omm ni ie . Among e e ial f a na af f ec ed inc l ded in ec , amphibian , ep ile ( hic h e ol ed d ing he Ca bonif e o ), a ell a he dominan e e ial g o p, he he ap id (mammal- like ep ile ). T he e e ial f lo a a p edominan l c ompo ed of g mno pe m , inc l ding he c onif e . Lif e in he ea a imila o ha f o nd in middle De onian c omm ni ie f ollo ing he la e De onian c i i . Common g o p inc l ded he b ac hiopod , ammonoid , ga opod , c inoid , bon f i h, ha k , and f linid f o aminif e a. Co al and ilobi e e e al o p e e n , b ee e c eedingl a e. O gani m af f ec ed: T he Pe mian ma e inc ion oc c ed abo 248 million ea ago and a he g ea e ma e inc ion e e ec o ded in ea h hi o ; e en la ge han he p e io l di c ed O do ic ian and De onian c i e and he be e kno n End C e ac eo e inc ion ha f elled he dino a . Nine o nine - f i e pe c en of ma ine pec ie e e elimina ed a a e l of hi Pe mian e en . T he p ima ma ine and e e ial ic im inc l ded he f linid f o aminif e a, ilobi e , go e and ab la e c o al , bla oid , ac an hodian , plac ode m , and pel c o a , hic h did no i e be ond he Pe mian bo nda . O he g o p ha ee b an iall ed c ed inc l ded he b o oan , b ac hiopod , ammonoid , ha k , bon f i h, c inoid , e p e id , o ac ode , and ec hinode m www2.fiu.edu/ longoria/gly1101/UpperPz.html 6/13 12/19/11 Eonothem Phanerozoic Causes of t he Per mian E t inc t ion: :A P G , .O P O G D .A , P , / , . P T :T P F P .H P .A P .S , , , , P P C F . :A P .I , , , , .T , P V E . :T P S .T .E - C , , .T .T P .C N A R (NCAR) B ,C C , , . A P 250 250 I :: F , P .A E , ' - 90 70 - , U W .C Mo e on he B ck ball : Co mic S o a a a 'Ne E idence Tie Ma E inc ion o Ma i e Colli ion ' <h p://ne .na ionalgeog aphic.com/ne /2001/02/0222_b ck ball .h ml> Wha a e B ck ball ? - a m ch highe le el of comple ca bon molec le called b ckmin e f lle ene , o B ck ball , i h he noble (o chemicall non eac i e) ga e heli m and a gon apped in ide hei cage c e . F lle ene , hich con ain a lea 60 ca bon a om and ha e a c e e embling a occe ball o a geode ic dome, a e named fo B ckmin e F lle , ho in en ed he geode ic dome. See pic e abo e www2.fiu.edu/ longoria/gly1101/UpperPz.html 7/13 12/19/11 Eonothem Phanerozoic T he O igin of Ve eb a e A c ho da e (ph l m Cho da a) i an animal ha ha , a lea d ing pa of i lif e c c le, a no oc ho d, a do al hollo ne e c o d, and gill li . Ve eb a e , hic h a e animal i h bac kbone , a e impl a bph l m of c ho da e . T he anc e o and ea l membe of he ph l m Cho da a e e of - bodied o gani m ha lef f e f o il . A a e l, e kno li le abo he ea l e ol iona hi o of he c ho da e o e eb a e . S p i ingl , a c lo e ela ion hip e i be een ec hinode m and c ho da e , and he ma e en ha e ha ed a c ommon anc e o ( ee ph logen ee abo e). T hi i bec a e in he de eloping emb o of ec hinode m and c ho da e , c ell di ide b adial c lea age o ha he c ell a e aligned di ec l abo e eac h o he . In all o he in e eb a e , c ell nde go pi al c lea age, hic h e l in ha ing c ell ne ed be een eac h o he in cce i e o . The Fishes: The most primitive vertebrates are fish, and some of the oldest fish remains are found in the Upper Cambrian Deadwood Formation in northeastern Wyoming. .Here phosphatic scales and plates of Anat olepis, a primitive member of the class Agnatha (jawless fish), have been recovered from marine sediments. All known Cambrian and Ordovician fossil fish have been found in shallow, nearshore marine deposits, whe reas the earliest nonmarine (freshwater) fish remains have been found in Silurian strata. This does not prove that fish originated in the oceans, but it does lend strong support to the idea. As a group, fish range from the Late Cambrian to the present. The Agnatha: are the oldest and most primitive of class of fish and typified by the os tracode rms , whose name means bony skin" are . These are armored, jawless fish that first evolved during the Late Cambrian, reached their zenith during the Silurian and Devonian, and then became extinct. The majority of ostracoderms lived on the seafloor. A typical examples of ostracoderm are the genera Hemic claspis and Pt eraspis Hemic claspis which is a bottom- dwelling ostracoderm. Vertical scales allowed Hemic claspis to wiggle sideways, propelling itself along the seafloor, and the eyes on the top of its head allowed it to see such predators as cephalopods and jawed fish approaching from above. While moving along the sea bottom, it probably sucked up small bits of food and sediments through its jawless mouth. Pt eraspis, was more elongated and probably an activeswimmer, although it also seemingly fed on small pieces of food that it was able to suck up. Primiti e ja e d fis h: The evolution of jaws was a major evolutionary advance among primitive vertebrates. Although their jawless ancestors could only feed on detritus, jawed fish could chew food and become active predators, thus opening many new ecologic niches. The vertebrate jaw is an excellent example of evolutionary opportunism. Various studies suggest that the jaw originally evolved from the first three gill arches of jawless fish. Because the gills are soft, they are supported by gill arches of bone or cartilage. The evolution of the jaw may thus have been related to respiration rather than to feeding. By evolving joints in the forward gill arches, jawless fish could open their mouths wider. Every time a fish opened and closed its mouth, it would pump more water past the gills, thereby increasing the oxygen intake. The modification from rigid to hinged forward gill arches let fish increase both their food consumption and oxygen intake, and the evolution of the jaw as a feeding structure rapidly followed. The fossil remains of www2.fiu.edu/ longoria/gly1101/UpperPz.html 8/13 12/19/11 Eonothem Phanerozoic the first jawed fish are found in Lower Silurian rocks and belong to the acanthodians (Class Acanthodii), a group of small, enigmatic fish characterized by large spines, paired fins, scales covering much of the body, jaws, teeth, and greatly reduced body armor. Although their relationship to other fish is not well established, many scientists think the acanthodians included the probable ancestors of the present- day bony and cartilaginous fish groups. The acanthodians were most abundant during the Devonian, declined in importance through the Carboniferous, and became extinct during the Permian. The other jawed fish, the placode rms (Class Placodermii), whose name means "plateskinned," evolved during the Late Silurian. Placoderms were heavily armored, jawed fish that lived in both freshwater and the ocean, and, like the acanthodians, reached their peak of abundance and diversity during the Devonian. The placoderms showed considerable variety, including small bottom dwellers, as well as large major predators such as Dunk leost eus, a Late Devonian fish that lived in the midcontinental North American epeiric seas. It was by far the largest fish of the time, reaching a length of more than 12 m. It had a heavily armored head and shoulder region, a huge jaw lined with razor- sharp bony teeth, and a flexible tail, all features consistent with its status as a ferocious predator. Age s of Fis h: Besides the abundant acanthodians, placoderms, and ostracoderms, other fish groups, such as the cartilaginous and bony fish, also evolved during the Devonian Pe riod. Small wonder, then, that the Devonian is informally called the "Age of Fish," because all major fish groups were present during this time period. The cartilaginous fis h: (Class Chrondrichthyes), represented today by sharks, rays, and skates, first evolved during the Early Devonian, and by the Late Devonian, primitive marine sharks such as Cladoselache were quite abundant. Cartilaginous fish have never been as numerous or as diverse as their cousins, the bony fish, but they were, and still are, important members of the marine vertebrate fauna. The bon fis h: (Class Oste ichthyes) also first evolved during the Devonian. Because bony fish are the most varied and numerous of all the fishes, and because the amphibians evolved from them, their evolutionary history is particularly important. There are two groups of bony fish: the common ra -finne d fis h (subclass Actinopterygii) and the less familiar lobe -finne d fis h (subclass Sarcopterygii). The term ra -f inned refers to the way the fins are supported by thin bones that spread away from the body. From a modest freshwater beginning during the Devonian, ray- finned fish, which include most of the familiar fish such as trout, bass, perch, salmon, and tuna, rapidly diversified to dominate the Mesozoic and Cenozoic seas. Present- day lobe-f inned f ish are characterized by muscular fins. The fins do not have radiating bones but rather have articulating bones with the fin attached to the body by a fleshy shaft. Such an arrangement allows for a powerful stroke of the fin, making the fish an effective swimmer. Three orders of lobe- finned fish are recognized: coe lacanths , lungfis h, and cros s opte r gians . Coe lacanths : (order Coelacanthimorpha) are marine lobe- finned fish that evolved during the Middle Devonian and were thought to have gone ex tinct at the end of the Cretaceous. In 1938, however, a fisherman caught a coelacanth in the deep waters off Madagascar and since then, several dozen more have been caught, both there and in Indonesia. www2.fiu.edu/ longoria/gly1101/UpperPz.html 9/13 12/19/11 Eonothem Phanerozoic Lungfis h: (order Dipnoi) were fairly abundant during the Devonian, but today only three freshwater genera exist, one each in South America, Africa, and Australia. Their present day distribution presumably reflects the Mesozoic breakup of Gondwana. The lung" of a modernday lungfish is actually a modified swim bladder that most fish use for buoyancy in swimming. In lungfish, this structure absorbs oxygen, allowing them to breath air when the lakes or streams in which they live become stagnant and dry up. During such times, they burrow into the sediment to prevent dehydration and breath through their swim bladder until the stream begins flowing or the lake they were living in fills with water. When they are back in the water, lungfish then rely on gill respiration. The cros s opte r gians : (order Crossopterygii) are an important group of lobe- finned fish, because it is probably from them that amphibians evolved. However, the transition between crossopterygians and true amphibians is not as simple as it was once portrayed. The group of crossopterygians that appears to be ancestral to amphibians are rhipidistians. These fish, reaching lengths of over 2 m, were the dominant freshwater predators during the Late Paleozoic. E henop e on, a good example of a rhipidistian crossopterygian and the classic example of the transitional form between fish and amphibians, had an elongated body that helped it move swiftly through the water and paired, muscular fins that many scientists thought could be used for moving on land. The structural similarity between crossopterygian fish and the earliest amphibians is striking and one of the most widely cited examples of a transition from one major group to another.. However, recent discoveries of older lobe- finned fish and tetrapods like Acan ho ega, and newly published findings of tetrapod- like fish, are filling in the gaps in the time of the evolution between fish and tetrapods. Before discussing this transition and the evolution of amphibians, it is useful to place the evolutionary history of Paleozoic fish in the larger context of Paleozoic evolutionary events. Certainly, the evolution and diversification of jawed fish as well as eurypterids and ammonoids had a profound effect on the marine ecosystem. Previously defenseless organisms either evolved defensive mechanisms or suffered great losses, possibly even extinction. Ostracoderms, although armored, would also have been easy prey for the swifter jawed fishes. Ostracoderms became extinct by the end of the Devonian, a time that coincides with the rapid evolution of jawed fish. Placoderms, like acanthodians, greatly decreased in abundance after the Devonian and became extinct by the end of the Paleozoic. In contrast, cartilaginous and ray- finned bony fish expanded during the Late Paleozoic, as did the ammonoid cephalopods, the other major predators of the Late Paleozoic seas. Amphibians - Ve rte brate s Invade the land Although amphibians were the first vertebrates to live on land, they were not the first land- living organisms. Land plants, which probably evolved from green algae, first evolved during the Ordovician. Furthermore, insects, millipedes, spiders, and even snails invaded the land before amphibians. Fossil evidence indicates that such land- dwelling arthropods as scorpions and flightless insects had evolved by at least the Devonian. The transition from water to land required animals to surmount several barriers. The most critical were desiccation, reproduction, the effects of gravity, and the extraction of oxygen from the atmosphere by lungs rather than from water by gills. Up until the 1990s, the traditional evolutionary sequence had a www2.fiu.edu/ longoria/gly1101/UpperPz.html 10/13 12/19/11 Eonothem Phanerozoic Rhipidistian crossopterygian, like Eust henopt eron, evolving into a primitive amphibian like Ichthyostega. At that time, fossils of those two genera were about all paleontologists had to work with, and although there were gaps in morphology, the link between crossopterygians and these earliest amphibians was easy to see. Crossopterygians already had a backbone and limbs that could be used for walking and lungs that could extract oxygen. The oldest amphibian fossils, on the other hand, found in the Upper Devonian Old Red Sandstone of eastern Greenland and belonging to such genera as Icht h ost ega, had streamlined bodies, long tails, and fins along their backs, in addition to four legs, a strong backbone, a ribcage, and pelvic and pectoral girdles, all of which were structural adaptations for walking on land. These earliest amphibians thus appear to have inherited many characteristics from the crossopterygians with little modification. However, with the discovery of such fossils as Acant host ega and others like it, the transition between fish and amphibians involves a number of new genera that are intermediary between the two groups. Panderichthys, a large (up to 1.3 m long), Late Devonian (~380 million years ago) lobe- finned fish from Latvia, was essentially a contemporary of Eust henopt eron. It had a large tetrapod- like head with a pointed snout, dorsally lo cated eyes, and modifications to that part of the skull related to the ear region. From paleoenvironmental evidence, Panderichthys lived in shallow tidal flats or estuaries, using its lobe fins to maneuver around in the shallow waters. Acant host ega, a Late Devonian (365 million years ago) tetrapod seemed to be the perfect intermediary between fish and true land- dwelling tetrapods. However, its limbs could not support its weight on land, and thus it was an aquatic animal, using its limbs to navigate in water, rather than walking on land. In 2006, an exciting discovery of a 1.2- 2.8 m long, 375- million- year- old (Late Devonian) "fishapod" was announced. Discovered on Ellesmere Island, Canada, Tik t aalik roseae, from the Inuktitut meaning "large fish in a stream," was hailed as an intermediary between the lobe- finned fish like Panderichthys and the earliest tetrapod, Acant host ega Tik t aalik roseae is truly a "fishapod" in that it has a mixture of both fish and tetrapod characteristics. For example, it has gills and fish scales but also a broad skull, eyes on top of its head, a flexible neck and large rib cage that could support its body on land or in shal low water, and lungs, all of which are tetrapod features. What really excited scientists, however, was that Tik t aalik roseae has the beginnings of a true tetrapod forelimb, com plete with functional wrist bones and five digits, as well as a modified ear region. Sedimentological evidence suggests Tiktaalik roseae lived in a shallow water habitat associated with Late Devonian floodplains of Laurasia. the oldest known amphib ian, Ichthyostega, had skeletal features that allowed it to spend its life on land. Because amphibians did not evolve until the Late Devonian, they were a minor element of the Devonian terrestrial ecosystem. Like other groups that moved into new and previously unoccupied niches, am phibians underwent rapid adaptive radiation and became abundant during the Carboniferous and Early Permian. The Late Paleozoic amphibians did not at all resemble the familiar frogs, toads, newts, and salamanders that make up the modern amphibian fauna. Rather, they displayed a broad spectrum of sizes, shapes, and modes of life. One group of amphibians were the labyrinthodonts, so named for the labyrinthine wrinkling and folding of the chewing surface of their teeth. Most labyrinthodonts were large animals, as much as 2 m in length. These typically sluggish creatures www2.fiu.edu/ longoria/gly1101/UpperPz.html 11/13 12/19/11 Eonothem Phanerozoic lived inswamps and streams, eating fish, vegetation, insects, and other small amphibians. Labyrinthodonts were abundant during the Carboniferous when swampy conditions were widespread but soon declined in abundance during the Permian, perhaps in response to changing climatic conditions. Only a few species survived into the Triassic. Evolution of Re ptile s : The Land is Conque re d - Earl Re ptile s Amphibians were limited in colonizing the land because they had to return to water to lay their gelatinous eggs. The evolution of the amniote egg freed reptiles from this constraint. In such an egg, the developing embryo is surrounded by a liquid- filled sac called the amnion and provided with both a yolk, or food sac, and an allantois, or waste sac. In this way the emerging reptile is in essence a miniature adult, bypassing the need for a larval stage in the water. The evolution of the amniote egg allowed vertebrates to colonize all parts of the land, because they no longer had to return to the water as part of their reproductive cycle. Many of the differences between amphibians and reptiles are physiologic and are not preserved in the fossil record. Nevertheless, amphibians and reptiles differ sufficiently in skull structure, jawbones, ear location, and limb and vertebral construction to suggest that reptiles evolved from labyrinthodont ancestors by the Late Mississippian. This assessment is based on the discovery of a well- preserved fossil skeleton of the oldest known reptile, Westlothiana, and other fossil reptile skeletons from Late Mississippian- aged rocks in Scotland. Other early reptile fossils occur in the Lower Pennsylvanian Joggins Formation in Nova Scotia, Canada. Here remains of Hylonomus are found in the sediments filling in tree trunks. These earliest reptiles from Scotland and Canada were small and agile and fed largely on grubs and insects. They are loosely grouped together as protoroth rids , whose members include the earliest known reptiles. During the Permian Period, reptiles diversified and began displacing many amphibians. The reptiles succeeded partly because of their advanced method of reproduction and their more advanced jaws and teeth, as well as their ability to move rapidly on land. The pe l cos aurs , or finback reptiles, evolved from the protorothyrids during the Pennsylvanian and were the dominant reptile group by the Early Permian. They evolved into a diverse assemblage of herbivores, exemplified by the herbivore Edapho a and carnivores such as Dime odon. An interesting feature of the pelycosaurs is their sail. It was formed by vertebral spines that, in life, were covered with skin. The sail has been variously explained as a type of sexual display, a means of protection, and a display to look more ferocious. The current consensus seems to be that the sail served as some type of thermoregulatory device, raising the reptile's temperature by catching the sun's rays or cooling it by facing the wind. Because pely cosaurs are considered the group from which therapsids evolved, it is interesting that they may have had some sort of body- temperature control. The pelycosaurs became extinct during the Permian and were succeeded by the therapsids, mammal- like reptiles that evolved from the carnivorous pelycosaur lineage and rapidly diversified into herbivorous and carnivorous lineages. The raps ids were small- to medium- sized animals that displayed the beginnings of many mammalian features: fewer bones in the skull, because many of the small skull bones were fused; enlarged lower jawbone; differentiation of teeth for various functions such as nipping, tearing, and chewing food; and more vertically placed legs for greater flexibility, as opposed to the way the legs sprawled out to the side in primitive reptiles. In addition, many paleontologists think www2.fiu.edu/ longoria/gly1101/UpperPz.html 12/13 12/19/11 Eonothem Phanerozoic therapsids were endothermic, or warm- blooded, enabling them to maintain a constant internal body temperature. This characteristic would have let them expand into a variety of habitats, and indeed, the Permian rocks in which their fos sil remains are found are distributed not only in low latitudes but in middle and high latitudes as well. As the Paleozoic Erathem came to an end, the therapsids constituted about 90% of the known reptile genera and occupied a wide range of ecologic niches. The mass extinctions that decimated the marine fauna at the close of the Paleozoic had an equally great effect on the terrestrial population. By the end of the Permian, about 90% of all marine invertebrate species were extinct, compared with more than two- thirds of all amphibians and reptiles. Plants, in contrast, apparently did not experience as great a turnover as animals. Clich here to review the Evolution of Plants Bac k o Uni Plan www2.fiu.edu/ longoria/gly1101/UpperPz.html 13/13 ...
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