The first tritylodontid (Synapsida, Cynodontia) fossil from Scandinavia.

Lower Jurassic (Pliensbachian) sand- and siltstones of the Hasle Formation on the Danish Island of Bornholm have yielded a diverse invertebrate and vertebrate assemblage dominated by marine taxa. Recently, dental and skeletal remains of terrestrial animals have also been collected from this rock unit, including the first tritylodontid tooth from Scandinavia. Here we describe the new fossil (NHMD 1725979), identified as a left lower postcanine. Even though precise taxonomic placement within Tritylodontidae is difficult, the preserved morphological characters are shared to varying extent with the Middle Jurassic – Lower Cretaceous genera Polistodon, Montirictus, Nuurtherium, Stereognathus, Xenocretosuchus, and Shartegodon. Hence, NHMD 1725979 may represent the stratigraphically oldest occurrence of a derived tritylodontid.