Acta Palaeontologica Polonica

Species discrimination of the Late Triassic temnospondyl amphibian Metoposaurus diagnosticus

Tomasz Sulej

Acta Palaeontologica Polonica 47 (3), 2002: 535-546

Re-investigation of the skull roof in Metoposaurus diagnosticus from the German Middle Keuper revealed that in contrast to previous opinions, the lacrimal bone in this species enters the orbital margin. The same pattern is demonstrated by the skulls of a newly discovered metoposaur from the Keuper of Krasiejów in Poland. The difference in the shape of the parietal between the population from Krasiejów and the type population of Metoposaurus diagnosticus enables the discrimination of two separate subspecies within Metoposaurus diagnosticus. For the specimens from the Late Carnian of Drawno Beds at Krasiejów, Poland and its lateral equivalents Lehrberg Beds at Stuttgart-Sonnenberg and Kieselsandstein at Fichtenberg, Germany, a new chronosubspecies Metoposaurus diagnosticus krasiejowensis is erected. The new subspecies differs from the older nominal subspecies M. diagnosticus diagnosticus in having a shorter and wider prepineal part of the parietal. If one accepts that the nominal subspecies is the ancestor of M. krasiejowensis the change in the shape of the parietal would be a reversal of the trend towards elongating postorbital part of the skull observed in ancestors of the metoposaurids. It seems that the skull development in ontogeny changed after the anterior shift of the orbits occurred in the phylogenetic history of the metoposaurids. The difference in ornamentation of the interclavicle between European Metoposaurus and North American genera is corroborated by Polish material.

Key words: Amphibia, Temnospondyli, Metoposauridae, Metoposaurus, Triassic, Poland.

Tomasz Sulej [], Instytut Paleobiologii PAN, ul. Twarda 51/55, PL−00−818 Warszawa, Poland.

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