A Paleopopulation of Coryphodon lobatus (Mammalia: Pantodonta) from Deardorff Hill Coryphodon Quarry, Piceance Creek Basin, Colorado

A unique early middle Wasatchian paucispecific bone bed from Deardorff Hill in the Piceance Creek Basin of Colorado contains a minimum of 12 individuals of Coryphodon lobatus that range in age from subadult ‘‘yearlings’’ to senescent individuals. The preponderance of Coryphodon material in this assemblage (92% of the 700+ complete bones represent a single species of Coryphodon) argues for a ‘‘catastrophic’’ origin for this assemblage. The Deardorff Hill Coryphodon Quarry preserves one of the most complete dental eruption sequences reported to date for Coryphodon and allows interpretation of demographic and life history attributes not ordinarily observable, such as evidence of seasonality in births. In addition, females are disproportionate in number to males, further confirming that this species had a polygynous social structure. Mass mortality assemblages are useful in eliciting a better understanding of the range of variation in single populations. Metrically, the molars of C. lobatus specimens from Deardorff Hill Coryphodon Quarry have coefficients of variation ranging from 4 to 11, which are comparable to metric variation observed in other mass death Coryphodon assemblages. An understanding of the range of variation in this highly variable taxon is of particular importance in the taxonomy and phylogenetic relationships of this ubiquitous Eocene mammal.