metaxygnathus skeleton

Metaxygnathus denticulatus

  Metaxygnathus, recovered from Late Devonian deposits in New South Wales, Australia, is one of only two Devonian tetrapod body fossils found outside of Euramerica; the other tetraod, Sinostega, was recently discovered in northwest China.

The remains of Metaxygnathus is limited to an isolated lower jaw. The fact that the fossil was described in 1977 (several years before the spate of new findings) and that it was located in Australia rather than Euramerica has led some researchers to question whether it really is a tetrapod. However, a re-evaluation by Jennifer Clack has confirmed its tetrapod status.

The age of the deposits from which Metaxygnathus recovered is a matter of debate. Jennifer Clack reported that it's age ranges somewhere from the Frasnian-Famennian boundry to the late Famennian. In contrast, the Australian paleontologist Gavin Young reports that the site dates to the late Frasnian (as cited in Long and Gordon, 2004).

Associated fauna include two placoderms (Bothriolepis and Remigolepis) and a lunfish (Soederberghia).

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Books:
Clack, J.A. 2002. Gaining Ground: The Origin and Early Evolution of Tetrapods. Bloomington: Indiana Univ. Press.
Long, J.A. 1995. The Rise of Fishes: 500 Million Years of Evolution.
John Hopkins Univ. Press: Baltimore and London.
Scientific Papers
Campbell, K.S.W. and M.W. Bell. 1977. "A primitive amphibian from the Late Devonian of New South Wales." Alcheringa 1: 369-382.
Clack, J.A. 1988. "New material of the early tetrapod Acanthostega from the Upper Devonian of East Greenland." Paleontology 31: 699-724.
Clack, J.A. 1997. "Devonian tetrapod trackways and trackmakers: a review of the fossils and footprints." Paleogeography, Paleoclimatology, Paleoecology 130: 227-250.
Long, J.A. and M.S. Gordon. 2004. "The greatest step in vertebrate history: a paleobiological review of the fish-tetrapod transition." Physiological and Biochemical Zoology 77(5): 700-719.
Young, G.C. 1999. "Preliminary report on the biostratigraphy of new placoderm discoveries in the Hervey Group (Upper Devonian) of central New South Wales." Records of the West Australian Museum 57(supplement): 139-150.

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