elpistostege skeleton

Elpistostege watsoni

When Stanley Westoll reported on the first Elpistostege fossil (a partial skull roof) in 1938, he identified it as an early amphibian. With the discovery of additional fossils (dermal elements of skulls along with associated vertebrae and scales) in 1970 and during the 1980s, however, it was found to be a comparable to Panderichthys, a lobe-fin fish from Latvia. Elpistostege differs from Panderichthys mainly in its longer snout, smaller and more rounded orbits and slightly different pattern and proportion of dermal bones in the skull. The redescription of Elpistostege based on these newer specimens led Hans-Peter Schultze and Marius Arsenault to conclude that Panderichthys and Elpistostege exhibited a variety of features intermediate between those of the tristichopterid lobe-fins (e.g., Eusthenopteron) and the early tetrapods. A more recent paper by Per Ahlberg concludes that Elpistostege is more closely allied with the stem tetrapods than is Panderichthys.

Elpistostege is a member of the famous Miguasha fish fauna from the Escuminac Formation in Quebec. Long considered a lake deposit, this site is now believed to have been estuarine. The site was unusually rich in vertebrates of which the most famous is the lobe-fin Eusthenopteron foordii. Other vertebrates include an armored jawless fish (Escuminaspis), two anaspid-like jawless fishes (Endeilepis, Euphanerops), two placoderms (Bothriolepis and Plourdosteus), acanthodians (Diplacanthus), an early rayfin (Cheirolepis) and three other lobe-fins (Holoptychius, Miguashaia, and Scaumenacia).

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Web:
UNEP World Conservation Monitoring Centre's web ste on Miguasha Provincal Park:
www.wcmc.org.uk/protected_areas/data/wh/miguasha.html
Books:
Clack, J.A. 2002. Gaining Ground: The Origin and Early Evolution of Tetrapods. Bloomington: Indiana Univ. Press.
Janvier, P. 1996. Early Vertebrates. Claredon Press: Oxford.
Long, J.A. 1995. The Rise of Fishes: 500 Million Years of Evolution. John Hopkins Univ. Press. Baltimore and London.
Maisey, J.G. 1996. Discovering Fossil Fishes. Henry Holt & Co: New York.
Scientific Papers
Ahlberg, P.E., E. Luksevics and E. Mark-Kurik. 2000. A near-tetrapod from the Baltic Middle Devonian. Paleontology 43(3): 533-548.
Schultze, H.P and M. Arsenault. 1985. The panderichthyid fish Elpistostege: a close relative of tetrapods? Paleontology 28: 293-309.
Westoll, T.S. 1938. Ancestry of the tetrapods. Nature 141:127.

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