Osteology of the temnospondyl Trematosaurus brauni Burmeister, 1849 from the Middle Buntsandstein of Bernburg, Germany

Abstract

The slender-skulled temnospondyl Trematosaurus brauni forms the most common tetrapod in the Early Triassic of Germany, and is documented by numerous finds from Merkel's Quarry at Bernburg (Saale). The revision of the available material includes 75 skulls with a size range between 10.9 and 41 cm skull length, and a small suite of postcranial elements. T. brauni is characterized by a temporal sulcus of lateral line with two portions, a well-established occipital sulcus, a preorbital region slightly shorter than half skull length, and a wide interorbital distance with very small rounded orbits. Individual variation was substantial, ranging from wide-triangular-skulled morphs to ones with slightly elongate preorbital region. Despite the size range, few ontogenetic changes have been identified: (1) the length of orbit decreased gently proportionally with size, and (2) the width of postorbital skull table relative decreased proportionally with size. Phylogenetic analysis finds T. brauni to nest with the very similar Trematosuchus well within a clade of slender-skulled trematosauroids. Together, the two genera form the sister taxon of Tertrema and the rostrum-bearing lonchorhynchines, whereas Trematolestes and Tertremoides assume a more basal position within a monophyletic Trematosauridae, which forms the sister taxon of the short-snouted metoposaurid relatives.