Morphology and paleoecology of a hybodontiform with serrated teeth, Priohybodus arambourgi, from the Late Jurassic of northeastern Brazil.

Hybodontiformes was a diverse, successful, and important group of shark-like chondrichthyans known from a variety of ecosystems. Some representatives of the order had a wide palaeogeographic distribution, as is the case with Priohybodus arambourgi. With a multicuspidate crown, P. arambourgi was the first hybodontiform to develop fully serrated cutting edges on its teeth, a feature shared with many modern sharks (Neoselachii). Although Hybodontiformes comprises a group of early-diverging sharks with relevant diversity and abundance in different ecosystems across the Paleozoic and Mesozoic, the morphometry of preserved teeth has been weakly explored. Here, we present the first record of this taxon for the Aliança Formation (Tithonian) of the Tucano Basin, northeastern Brazil. The results demonstrated morphometric correlations of the features encompassed in the central cusp and lateral cusplets, indicating a non-allometric relationship in the increase of the crowns. P. arambourgi had a homodont dentition that preserves an ante-mortem wear pattern on the top of the central cusp, an important trait recognized as result for prey preferences. A comparison of the assemblages of P. arambourgi also demonstrates intraspecific variation among populations in Gondwana, indicating morphological plasticity of this species from Africa and South America. Finally, we compare the morphology of P. arambourgi with modern sharks, inferring the likely size, feeding mechanisms and prey preferences for a hybodontiform.