A Lower Carboniferous xenacanthiform shark from Australia

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.

ACKNOWLEDGMENTS

We are grateful to the Hawkins and Cann families, former and present owners of Ducabrook Station, as well as those of neighboring stations, for alerting us to the material and allowing access; to C. and J. van der Smissen (Brisbane) for finding and donating the jaw specimen; A. Warren (Melbourne) for preparation; and M. Brazeau (Berlin) for identifying the fragment as shark. S.T. thanks C. Duffin (London), O. Hampe (Berlin), J. Schneider (Freiberg), and G. D. Johnston (Dallas) for discussions and information on xenacanth teeth; and Hampe for help with histology. E. Daeschler (Philadelphia), S. McLean (Hancock Museum), J. Bolt and W. Simpson (FMNH), and the late C. Patterson (NHM) assisted with and gave permission to use museum collections and specimens. We are grateful to R. van der Kamp for translations; J. Bracefield, J. Ford, C. Northwood, and K. Stumkat for SEM and research assistance; C. Bonde and B. Tangey for preparation, curation, and databasing of specimens; and to all field work participants. Work was initiated when S.T. was ARC Australian Research Fellow (1995–2000), financially assisted 1997–1999 and 2000–2002 by ARC grants A39700915 and 00000629 to her and A. A. Warren. The Ian Potter Foundation, Melbourne, and the Field Museum provided travel grants to S.T. to visit the U.S.A. in 1997. We thank the Queensland Museum Board for basic facilities; QM librarians are ever helpful and Geoscience Australia also provided documents. Two referees and editor Dr. Charlie Underwood provided critical comments for the improvement of the manuscript in review.

Handling editor: Charlie Underwood.