Taxonomic revision and phylogenetic relationships of basal neoceratopsia (Dinosauria: Ornithischia)

Alphataxonomic review of all known nonceratopsid neoceratopsian species resulted in an autapomorphy based rediagnosis of most taxa, but also invalidation of several fragmentary taxa such as Kulceratops, Microceratops, and Turanoceratops. This revision identified fourteen valid or potentially valid taxa for phylogenetic analysis. A total of 122 cladistic characters were scored for fourteen basal ceratopsian and nine ceratopsid ingroup species, as well as three outgroups. In spite of large amounts of missing data analysis of this matrix yielded a highly resolved result with good support for some nodes. Chaoyangsaurus and an another undescribed Jurassic taxon form a small clade at the base of Neoceratopsia. Neoceratopsian monophyly is very robust and Archaeoceratops represents the basalmost neoceratopsian species. Contrary to most previously published hypotheses, Montanoceratops is more closely related to Leptoceratops and Udanoceratops than to ceratopsids, and this clade is classified as the Leptoceratopsidae. Protoceratops and Bagaceratops form an endemic Mongolian clade that is the sister taxon to a clade comprising Zuniceratops and the Ceratopsidae. Within Ceratopsidae, the traditional centrosaurine-chasmosaurine split is supported. Cumulative species appearance in the fossil record follows a near exponential curve, indicating higher speciation rates within the Ceratopsidae relative to the neoceratopsian stem. Based on this comprehensive analysis, several minor emendations to recent phylogenetic taxonomic classifications of Ceratopsia are proposed.; Comparisons of fit between the phylogeny and the stratigraphic record of ceratopsians were assessed using recently developed quantitative methods such as the Manhattan Stratigraphic Metric*, and suggest a better than random fit between the two patterns. In order to examine this fit locally rather than globally, a new measure, the Nodal Manhattan Stratigraphic Metric (NMSM) is developed here. NMSM analysis indicates that most nodes within the trees found here have better than random fits with first appearance dates, with the exception of the Leptoceratopsidae.; Optimization of continental distributions of ceratopsians between North America and Asia indicates a minimum of three dispersal events. Considering the size of the clade, this is relatively less intercontinental dispersal than observed in other dinosaur clades with sympatric and coeval distributions.