Abstract

Dicentrodus possessed bicuspid teeth with a flat base and nonserrated or finely serrated, labio-lingually compressed, highly unequal cusps. Originally known from the late Visean–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.

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