INTRODUCTION

The Cretaceous ichthyosaur fauna has been traditionally referred to as a single genus, Platypterygius Huene, 1922 (McGowan 1972, Sander 2000). Several species have been recognized from the Albian and Cenomanian including P. australis and P. longmani (synonymized by Kear 2003, McGowan and Motani 2003) from Australia, P. hauthali from Argentina, P. platydactylus and P. hercynicus from Germany, P. campylodon from England and France, P. kiprijanoffi and P. bannovkensis from Russia, and P. americanus from North America (Nace 1939, Wade 1984, 1990, Bardet 1992, 1994, Maisch and Matzke 2000, McGowan and Motani 2003, Kear 2003, Fernández and Aguirre-Urreta 2005). Maxwell and Caldwell (2006) have argued for a second yet unnamed North American species (UALVP 45636) from Northwest Territories, Canada, based on four distal facets that occur on the humerus.

Until recently, all of the diagnostic P. americanus specimens have been recovered from Wyoming, and only fragmentary remains are known from Texas, Oregon, and British Columbia. The published record of Ichthyosaurs in Texas consists of isolated vertebrae (McNulty and Slaughter 1962, Slaughter and Hoover 1963). The identification of these Texas specimens was based entirely on stratigraphic occurrences and not on characters diagnostic at the generic level. We describe here a partial ichthyosaur skeleton (DMNH 11843) of Platypterygius Huene 1922 and briefly discuss the taxonomic utility of limb characters employed in species level diagnoses of ichthyosaurs.

Institutional Abbreviations. DMNH, Museum of Nature and Science, Dallas, Texas; MLP, Museo de La Plata, La Plata, Argentina; QM, Queensland Museum, Brisbane, Australia; UALVP, University of Alberta, Laboratory for Vertebrate Paleontology, Edmonton, Alberta, Canada; SMU, Southern Methodist University; UW, University of Wyoming.