Journal of Vertebrate Paleontology 29(3):758–770, September 2009 # 2009 by the Society of Vertebrate Paleontology ARTICLE TAXONOMIC REVISON OF THE BASAL NEORNITHISCHIAN TAXA THESCELOSAURUS AND BUGENASAURA CLINT A. BOYD,*,1 CALEB MARSHALL BROWN,2 RODNEY D. SCHEETZ,3 and JULIA A. CLARKE1,4 1Department of Marine, Earth, and Atmospheric Sciences, Campus Box 8208, North Carolina State University, Raleigh, North Carolina 27695 U.S.A.,
[email protected]; 2Department of Biological Sciences, 2500 University Drive North West, University of Calgary, Calgary, AB, T2N 1N4, Canada,
[email protected]; 3Earth Science Museum, Brigham Young University, Provo, Utah 84602 U.S.A.,
[email protected]; 4North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, North Carolina 27601 U.S.A.,
[email protected]. ABSTRACT—Considerable controversy surrounds the taxonomy and phylogenetic relationships of Maastrichtian basal neornithischian taxa from North America. Discovery of previously unrecognized cranial material from the paratype specimen of Thescelosaurus neglectus (USNM 7758), along with the examination of two new specimens that preserve nearly complete skulls and mandibles, allows for reevaluation of specimens previously referred to Thescelosaurus that preserve cranial material, including the holotypes of Bugenasaura infernalis (SDSM 7210) and Parksosaurus warreni (ROM 804). A phylogenetic analysis was conducted that included as terminals the holotypes of B. infernalis and P. warreni, the type series of T. neglectus, and six specimens previously referred to Thescelosaurus. This analysis is the first to recover a clade containing all basal neornithischian taxa from the Cretaceous of North America, within which P. warreni is recovered as the sister taxon to a Thescelosaurus clade whose monophyly is supported by five cranial autapomorphies.