Mandibular dentition in the Late Triassic temnospondyl amphibian Metoposaurus

The Temnospondyli are a large and diverse group of stemtetrapods (sensu Laurin and Reisz 1997) known from the Early Carboniferous to the Early Cretaceous; their remains have been found on all continents, from Greenland to Antarctica. The Metoposauridae are a short−ranging temnospondyl group recorded only from the Late Triassic; they are characterized by an anterior position of the orbits, a broad parasphenoid and a large quadrate foramen. However, unclear is the taxonomic value of the external location of tusks on the dentary. Our analysis of tooth rows in Metoposaurus diagnosticus krasiejowensis from the Triassic (Late Carnian) of Krasiejów (Silesia, SW Poland) shows that the external location of tusks on the dentary is not a synapomorphy for Metoposauridae but a character of great intraspecific variability. Variability of the arrangement of the internal tooth row on the upper jaw has also been observed.