Greererpeton

Greererpeton burkemorani ("crawler from Greer, West Virginia") is an extinct genus of colosteid stem-tetrapods from the Early Carboniferous period (late Viséan) of North America. Greererpeton was first described by famed vertebrate paleontologist Alfred S. Romer in 1969.[1] The skull was redescribed by Timothy R. Smithson in 1982,[2] while postcranial remains were redescribed by Stephen J. Godfrey in 1989.[3]

Life restoration by Dmitry Bogdanov

Greererpeton
Temporal range: Viséan 345.3–328.3 Ma
Specimen CMNH 11090, one of the largest and most complete Greererpeton skeletons known
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Family: †Colosteidae
Genus: †Greererpeton
Species:
†G. burkemorani
Binomial name
†Greererpeton burkemorani
Romer, 1969

Greererpeton were probably aquatic, with an elongated body adapted for swimming. Adults were similar in size to modern Asian giant salamaders (Andrias), which could grow up to 1.5 metres (4.9 ft) in total length. The body was elongated, with about 40 vertebrae, while the flattened skull 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 in Andrias. 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.[4]

Paleobiology

There is a large amount of evidence that Greererpeton and other colosteids were completely aquatic animals.[5] Grooves on the side of the skull indicate that Greererpeton had lateral lines, sensory organs commonly found only in fish and aquatic stem-tetrapods. The stapes 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 of Greererpeton 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) considered Greererpeton to be biologically similar to the modern Asian giant salamanders (Andrias), the largest living amphibians. Preserved Greererpeton 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. Young Andrias congregate in shallow water while older individuals were bottom-dwelling predators preferring deeper rivers. Given that small Greererpeton skeletons have been found in groups while larger ones are solitary, it is presumable that Greererpeton behaved similarly.[3]

Footnotes
  1. Romer, Alfred S. (14 March 1969). "A temnospondylous labyrinthodont from the Lower Carboniferous". Kirtlandia. 6: 1–20.
  2. Smithson, T. R. (1 September 1982). "The cranial morphology of Greererpeton burkemorani Romer (Amphibia: Temnospondyli)". Zoological Journal of the Linnean Society. 76 (1): 29–90. doi:10.1111/j.1096-3642.1982.tb01955.x. ISSN 0024-4082.
  3. Godfrey, S.J. (2 February 1989). "The postcranial skeletal anatomy of the carboniferous tetrapod Greererpeton burkemorani Romer, 1969". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 323 (1213): 75–133. doi:10.1098/rstb.1989.0002. JSTOR 2396758.
  4. M. Alan Kazlev (1998) The Carboniferous Period of the Paleozoic Era: 299 to 359 million years ago Archived 2008-06-21 at the Wayback Machine, Palaeos.org, Retrieved on 2008-06-23
  5. Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 51. ISBN 978-1-84028-152-1.
  6. Janis, Christine M.; Farmer, Colleen (May 1999). "Proposed habitats of early tetrapods: gills, kidneys, and the water–land transition". Zoological Journal of the Linnean Society. 126 (1): 117–126. doi:10.1006/zjls.1998.0169. ISSN 0024-4082.
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