A new species ofPalatobaena(Testudines: Baenidae) and a maximum parsimony and Bayesian phylogenetic analysis of Baenidae

Abstract

NewPalatobaenamaterial from the Hell Creek Formation (Maastrichtian), including the first skull and shell association, from southwestern North Dakota represents a new species named hereinPalatobaena cohen.the material consists of 4 skulls, 2 lower jaws, and 2 shells and represents a true biological population (spatially and temporally restricted), which provides unprecedented access to ontogenetic and other intraspecific variation found in this taxon. the skull's round shape and lack of a lingual ridge on the greatly expanded triturating surface indicate itsPalatobaenaaffinities, but it differs from both previously existingPalatobaenataxa in a number of features. the addition of shell characters to the most inclusive baenid phylogenetic analyses (Maximum parsimony and Bayesian) to date indicate thatPa. cohenis sister taxon to the otherPalatobaenataxa. Notably, both the maximum parsimony analysis and Bayesian analysis provide strong support forPlesiobaena antiquaas sister to thePalatobaenaclade. in addition, both analyses provide strong support forStygiochelys estesias sister to the Eocene clade ofBaena arenosaandChisternon undatum, which significantly reduces this clades' ghost lineage. the baenid topology reveals a demonstrably homoplastic trend towards the reduction of the temporal emargination and unique thickening of the posterior portion of the parietals that corresponds with the K/T boundary and is hypothesized to have provided limited protection from increasingly effective mammalian predators.