| Greererpeton | |
|---|---|
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| Specimen CMNH 11090, one of the largest and most completeGreererpeton skeletons known | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Family: | †Colosteidae |
| Genus: | †Greererpeton |
| Species: | †G. burkemorani |
| Binomial name | |
| †Greererpeton burkemorani Romer, 1969 | |
Greererpeton burkemorani ("crawler fromGreer, West Virginia") is an extinctgenus ofcolosteidstem-tetrapods from the EarlyCarboniferous period (lateViséan) of North America.Greererpeton was first described by famed vertebrate paleontologistAlfred S. Romer in 1969, based on a skull and partial skeleton from theBluefield Formation.[1] The skull was redescribed byTimothy R. Smithson in 1982,[2] while postcranial remains were redescribed byStephen J. Godfrey in 1989.[3]
Greererpeton were probably aquatic, with an elongated body adapted for swimming. Adults have overall length of 1.0–1.4 metres (3.3–4.6 ft)[3] or 1.5 metres (4.9 ft),[4] similar in size to modern Asian giant salamanders (Andrias). The body was elongated, with about 40vertebrae, while the flattenedskull reached about 18 centimetres (7.1 in) long in adult specimens. The most complete adult specimen only preserved 12 tail vertebrae, only about a third the length of the body as inAndrias. However, smaller specimens have been found preserving over 30 vertebrae, so it is not inconceivable that a complete tail was approximately as long as the body.[3] The limbs were short, though not vestigial; the fingers were still well-developed.Greererpeton were carnivores which probably lived in rivers and swamps.[5]
There is a large amount of evidence thatGreererpeton and other colosteids were completely aquatic animals.[4] Grooves on the side of the skull indicate thatGreererpeton hadlateral lines, sensory organs commonly found only in fish and aquatic stem-tetrapods. Thestapes bone at the rear of the skull is massive, probably used as a support for the skull. This contrasts with the stapes of terrestrial animals such as frogs, mammals, and lizards. In these groups the bone is thin and sensitive to vibration, so it is used for sensitive hearing. The thick stapes ofGreererpeton is an indication that did not have good hearing like terrestrial animals.[2]Greererpeton retains a postbranchial lamina on its shoulder blade, which may have been indicative of internal gills like those of fish. However, the erratic distribution of postbranchial laminae in aquatic and terrestrial fish and amphibians makes this conclusion questionable.[6]
Godfrey (1989) consideredGreererpeton to be biologically similar to the modernAsian giant salamanders (Andrias), the largest living amphibians. PreservedGreererpeton skeletons have their bodies lay completely flat, with their tails twisted over to lay flat perpendicular to the body. These preservational quirks may indicate that the body was flattened dorsoventrally (from top-to-bottom), while the tail was flattened mediolaterally (from side-to-side) into a fin-like structure used for swimming. YoungAndrias congregate in shallow water while older individuals were bottom-dwelling predators preferring deeper rivers. Given that smallGreererpeton skeletons have been found in groups while larger ones are solitary, it is presumable thatGreererpeton behaved similarly.[3]
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