Transitions among amphibians (elder)

[Bright-ness' Shadow]

Transitional Vertebrate Fossils FAQ



* Temnospondyls, e.g Pholidogaster (Mississippian, about 330 Ma) -- A group of large labrinthodont amphibians, transitional between the early amphibians (the ichthyostegids, described above) and later amphibians such as rhachitomes and anthracosaurs. Probably also gave rise to modern amphibians (the Lissamphibia) via this chain of six temnospondyl genera , showing progressive modification of the palate, dentition, ear, and pectoral girdle, with steady reduction in body size (Milner, in Benton 1988). Notice, though, that the times are out of order, though they are all from the Pennsylvanian and early Permian. Either some of the "Permian" genera arose earlier, in the Pennsylvanian (quite likely), and/or some of these genera are "cousins", not direct ancestors (also quite likely).
* Dendrerpeton acadianum (early Penn.) -- 4-toed hand, ribs straight, etc.
* Archegosaurus decheni (early Permian) -- Intertemporals lost, etc.
* Eryops megacephalus (late Penn.) -- Occipital condyle splitting in 2, etc.
* Trematops spp. (late Permian) -- Eardrum like modern amphibians, etc.
* Amphibamus lyelli (mid-Penn.) -- Double occipital condyles, ribs very small, etc.
* Doleserpeton annectens or perhaps Schoenfelderpeton (both early Permian) -- First pedicellate teeth! (a classic trait of modern amphibians) etc.

From there we jump to the Mesozoic:

* Triadobatrachus (early Triassic) -- a proto-frog, with a longer trunk and much less specialized hipbone, and a tail still present (but very short).
* Vieraella (early Jurassic) -- first known true frog.
* Karaurus (early Jurassic) -- first known salamander.

Finally, here's a recently found fossil:

* Unnamed proto-anthracosaur -- described by Bolt et al., 1988. This animal combines primitive features of palaeostegalians (e.g. temnospondyl-like vertebrae) with new anthracosaur-like features. Anthracosaurs were the group of large amphibians that are thought to have led, eventually, to the reptiles. Found in a new Lower Carboniferous site in Iowa, from about 320 Ma.

[Daystar]

Originally Posted by pah

Transitional Vertebrate Fossils FAQ



* Temnospondyls, e.g Pholidogaster (Mississippian, about 330 Ma) -- A group of large labrinthodont amphibians, transitional between the early amphibians (the ichthyostegids, described above) and later amphibians such as rhachitomes and anthracosaurs. Probably also gave rise to modern amphibians (the Lissamphibia) via this chain of six temnospondyl genera , showing progressive modification of the palate, dentition, ear, and pectoral girdle, with steady reduction in body size (Milner, in Benton 1988). Notice, though, that the times are out of order, though they are all from the Pennsylvanian and early Permian. Either some of the "Permian" genera arose earlier, in the Pennsylvanian (quite likely), and/or some of these genera are "cousins", not direct ancestors (also quite likely).
* Dendrerpeton acadianum (early Penn.) -- 4-toed hand, ribs straight, etc.
* Archegosaurus decheni (early Permian) -- Intertemporals lost, etc.
* Eryops megacephalus (late Penn.) -- Occipital condyle splitting in 2, etc.
* Trematops spp. (late Permian) -- Eardrum like modern amphibians, etc.
* Amphibamus lyelli (mid-Penn.) -- Double occipital condyles, ribs very small, etc.
* Doleserpeton annectens or perhaps Schoenfelderpeton (both early Permian) -- First pedicellate teeth! (a classic trait of modern amphibians) etc.

From there we jump to the Mesozoic:

* Triadobatrachus (early Triassic) -- a proto-frog, with a longer trunk and much less specialized hipbone, and a tail still present (but very short).
* Vieraella (early Jurassic) -- first known true frog.
* Karaurus (early Jurassic) -- first known salamander.

Finally, here's a recently found fossil:

* Unnamed proto-anthracosaur -- described by Bolt et al., 1988. This animal combines primitive features of palaeostegalians (e.g. temnospondyl-like vertebrae) with new anthracosaur-like features. Anthracosaurs were the group of large amphibians that are thought to have led, eventually, to the reptiles. Found in a new Lower Carboniferous site in Iowa, from about 320 Ma.

"Thought to have led?" All you're doing is describing variations within species, not changes between different species.

[Bright-ness' Shadow]

Originally Posted by Daystar

"Thought to have led?" All you're doing is describing variations within species, not changes between different species.

Ah yeah, I see. A salamander and a frog are of the same species eh?

-pah-