Diversity of tooth mineralisation patterns at the base of crown chondrichthyans

Abstract The highly specialised dentitions of modern sharks enable them to exploit a wide range of food sources. Exceptional fossil preservation of three Late Devonian basal chondrichthyan taxa from the Anti-Atlas, Morocco, provides the unique opportunity to study these dentitions in detail, including their tooth histology, replacement patterns, and mineralisation sequences. Thin sections and CT-data of tooth files reveal a high histological diversity and evidence a noticeable disparity in mineralisation patterns early in chondrichthyan evolution. The presence of similar tooth histology and mineralisation patterns in phylogenetically and chronostratigraphically distant chondrichthyan taxa opposes a phylogenetic signal. Although the pseudoosteodont histotype is considered plesiomorphic, we found a high disparity regarding the arrangement of dental tissues in early chondrichthyans. Tooth size differences indicate slow tooth replacement rates for Ctenacanthus and Maghriboselache . Smaller differences in Phoebodus suggest an elevated rate. Tooth retention in Maghriboselache might constitute a precursor for the holocephalan evolution of tooth plates.