Abstract

A new Early Carboniferous (Mississippian, mid-Viséan) chondrichthyan, Reginaselache morrisi, n. g., n. sp., from non- or marginal marine sandy mudstones of the Tetrapod Unit of the mid-Viséan (330 Ma = top Holkerian/basal Asbian) Ducabrook Formation, northwest of Springsure, central Queensland, is referred to the order Xenacanthiformes. The taxon is represented by robust diplodont teeth with multicristate cusps, a prominent rounded coronal button, and a horseshoe-shaped labial boss. Rare spine fragments from the type locality, and a partial lower jaw from a site close by are also tentatively referred to the taxon. Reginaselache morrisi was a medium-sized, ca. 1 m long shark with numerous teeth, probably feeding on smaller paleoniscoid and other fishes and/or invertebrates. Analysis of the teeth and comparison with those of other Carboniferous and later Paleozoic xenacanthiforms shows that the tooth cusp morphology is closest to those of Triodus Hampe and Bohemiacanthus Schneider. A restricted cladistic analysis of the xenacanthiforms with outgroups Leonodus Mader, Phoebodus St John and Worthen, and Antarctilamna Young supports the family Diplodoselachidae Hampe as a clade comprising just two genera, Diplodoselache and Reginaselache.