Dicentrodus (Chondrichthyes: Xenacanthida) from the Early Carboniferous (Visean: upper St Louis Formation) of Iowa, USA

Dicentrodus possessed bicuspid teeth with a flat base and nonserrated or finely serrated, labio-lingually compressed, highly unequal cusps. Originally known from the late Viscan-early Serpukhovian of Scotland (D. bicuspidatus), it is now known also to occur in the middle Visean of North America. This is the earliest occurrence of a xenacanthid yet reported from North America; its presence is based on incomplete teeth, which are easily distinguished from other xenacanthid genera. The cross-continental distribution of Dicentrodus, like that of other xenacanthid genera, can be explained by an increasing body of data that intimate that xenacanthids were euryhaline sharks and not restricted to a freshwater habitat.