Morphometrics of the mandible of Metoposaurus krasiejowensis Sulej, 2002 and its ecological implications

Abstract

Amphibians, due to their ecological plasticity, are some of the best environmental indicators among vertebrates nowadays and in the fossil record. One such example is the extinct family Metoposauridae Watson, 1919. Metoposaurids were abundant amphibians in Late Triassic Pangea. The remains of the genus Metoposaurus Lydekker, 1890 have been found in Germany, Poland and Portugal with three species, respectively Metoposaurus diagnosticus (Meyer, 1842), Metoposaurus krasiejowensis Sulej, 2002 and Metoposaurus algarvensis Brusatte, Butler, Mateus and Steyer, 2015. Since the majority of studies concern the skull and the pectoral girdle, in this work M. krasiejowensis has been analysed through a morphometric study of the mandible. This was made possible by the high abundance of fossils found in Krasiejów (SW Poland) in the last 20 years. The characteristics considered are the morphology of the mandible corpus and its most relevant bones, the adaptation to stress during biting and the dermal ornamentation. The results reveal that not only do these characters have great intraspecific variability, but that at least two groups of a single population of M. krasiejowensis probably had different lifestyles, one more aquatic and the other more terrestrial.