Vertebrate(Lecture ppt) Ch 9-2 (10) amphibian Lepospondyli

Vertebrate(Lecture ppt) Ch 9-2 (10) amphibian Lepospondyli...

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Unformatted text preview: Lepospondyls 莢莢莢 : Introduction The lepospondyls consist of four orders of mostly small aquatic tetrapods. All are limited to the Carboniferous and/or early Permian. They may or may not be an artificial (polyphyletic) group. They may be ancestral to modern amphibians. has recently been suggested that the Lepospondyls are closely related to the ancestry of the amniotes ( reptiles etc) see Terrestrial Vertebrates- Michel Laurin. (MAK 981217) Lepospondyli : Rana > Rambo. That is, this is the frog & salamander stem of the crown group tetrapods*. Range: from the Early Carboniferous . Phylogeny: Tetrapoda* : Reptilomorpha + *: Nectridia + (( Aïstopoda + Adelogyrinidae ) + Microsauria ) Characters: Possibly paraphyletic group united mostly by relatively small size and lack of labyrinthodont dentition. Single, spool-shaped vertebral centrum. May be stem group for Lissamphibia , rather than temnospondyls . Others eliminate this taxon altogether. Links: Amphibia [Lepospondyli after Laurin & Reisz, 1997] ; Amphibians ; Evolución . ATW030204 A Lepospondyl Cladogram TETRAPODA |-- REPTILOMORPHA Lepospondyli 莢莢莢 |-- Nectridia `--+--+-- Aïstopoda | `-- Adelogyrinidae `-- Microsauria |-- Lysorophia | | LISSAMPHIBIA Nectridia 莢莢莢 : Ctenerpeton, Diplocaulus, Keraterpeton, Sauropleura, Scincosaurus . Range: lwC–upP (lwP?) of Eur., NAm, and NAfr. Phylogeny: Lepospondyli : (( Aïstopoda + Adelogyrinidae ) + Microsauria ) + *. Introduction: The Nectridia were a group of small to medium-sized paleozoic amphibians, mostly aquatic, usually included within the lepospondyl group. Most forms resemble modern newts, with elongate flatened tails. A few late speed forms however developed strange boomerang-shape heads. These remarkable heads probably served as hydrofoils to provide lift in slow-moving streams. The Nectridia were a surprisingly succesful group during the Early Permian, but may have been unable to cope with the increasingly arid conditions at the end of the Permian, and died out without leaving any descendants. The nectridians are best known from Diplocaulus and similar small to medium sized (length to 50 or 100 cm) members of the Keraterpontidae, the most extreme members of the Nectridean group, characterised by skulls possessing large backward or sideways directed "horns" or perhaps more accurately, hydroplanes. Keraterpontidae would have fed on small fish and aquatic invertebrates, and were themselves preyed upon by larger amphibians and freshwater sharks. (MAK 981010) Characters: Primitively, skull table narrow and moveable on jugal; tabular horns in some forms (Keraterpetontidae); primitively, skull table narrow and moveable on jugal; some skull kinesis (Diplocaulids lose kinesis – very large tabular horns); body laterally compressed, fan-shaped, symmetrical neural and hemal arches; little flexibility in trunk; elongate in tail (not trunk); trunk limbs interdigitate through neural spines; limbs small; secondarily aquatic....
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This note was uploaded on 12/28/2011 for the course LSCI 102 taught by Professor Chien-pingwang during the Fall '11 term at National Cheng Kung University.

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Vertebrate(Lecture ppt) Ch 9-2 (10) amphibian Lepospondyli...

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