Reappraisal of the record of the genus Paraisurus (Chondrichthyes; Lamniformes) from the Lower Cretaceous of Northern Italy

Isolated and associated teeth of the poorly known lamniform shark Paraisurus macrorhizus are described from the Lower Cretaceous of northern Italy. These fossils, coming from a quarry located in the surroundings of the city of Trento (Trentino-Alto Adige, northeastern Italy), were preliminarily reported in 1927 by D'Erasmo with a problematic age attribution. Based on calcareous nannofossil analyses of the embedding matrix, the fossils are herein assigned to the Albian. The fossil record of Paraisurus is briefly reviewed, and a comparative morphometric analysis is carried out. The PCA analysis on a small data set highlights the existence of two distinct morphotypes that correspond to the two species Paraisurus macrorhizus and P. compressus. This analysis also suggests that P. amudarjensis should be regarded as a junior synonym of P. compressus. Specialised dental features of the genus Paraisurus are also discussed.