obruchevichthys skeleton

Obruchevichthys gracilis

A jaw fragment of Obruchevichthys gracilis was recovered from Upper Frasnian (Late Devonian) deposits in Latvia. This specimen, originally identified as a lobe-fin fish, was reclassified as a tetrapod after Per Ahlberg reported that it shared many diagnostic features with the jaw of Elginerpeton, a tetrapod of similar age from Scotland.

Obruchevichthys and Elginerpeton predate the other Late Devonian tetrapods by 5-8 million years. This, and the fact that both tetrapods share several unique features, suggest that they represent a distinct and presumably short-lived radiation that diverged prior to the emergence of other tetrapods.

Associate fauna include placoderms (Bothriolepis), an acanthodian (Devonichus), lungfishes, a porolepiform lobe-fin (Holoptychius) and jawless heterostracans (Psammolepis).

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G.R. Morton's Transitional Forms: Fish to Amphibian:
Clack, J.A. 2002. Gaining Ground: The Origin and Early Evolution of Tetrapods. Bloomington: Indiana Univ. Press.
Scientific Papers
Ahlberg, P.E. 1991. "Tetrapod or near-tetrapod fossils from the Upper Devonian of Scotland." Nature 354: 298-301.
Ahlberg, P.E. 1995. "Elginerpeton pancheni and the earliest tetrapod clade." Nature 373: 420-425.
Carroll, R. 1995. "Between Fish and Amphibians." Nature 373: 389-390.
Clack, J.A. 1997. "Devonian tetrapod trackways and trackmakers: a review of the fossils and footprints." Paleogeography, Paleoclimatology, Paleoecology 130: 227-250.
Daeschler, E.B. and N. Shubin. 1995. "Tetrapod Origins." Paleobiology 21(4): 404-409.
Vorobyeva, E.I. 1977. "Morphology and nature of evolution of crossopterygian fishes." Trudy Paleontological Institute Akademie Nauk SSSR 163: 1-239 [in Russian].

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