Abstract

A total of 16 species have been named or referred to the genus Triceratops. Surprisingly, the genus has never been formally diagnosed until recently. The first named species, T. alticornus, is not demonstrably referrable to Triceratops. Accordingly, the second named species, T. horridus, is here designated the type species of the genus. All other named species of Triceratops are here considered to be conspecific and thus invalid taxa. The supposed diagnostic differences among them fall well within normal ranges of variation in examples of large and small extant reptilian and mammalian species. Even more conclusive data are the stratigraphic and geographic distribution of the “type specimens” of the 16 “species” of Triceratops. Eleven of the sixteen type specimens were collected from the same stratigraphic unit (Lance Formation) and from a small area about one-quarter the size of the state of Rhode Island.

Introduction

The selection of diagnostic anatomical features that enable us to distinguish between different taxa (either species or genera) of related extinct organisms should and must be a topic of critical importance to all paleobiologists. The criteria by which such diagnostic features are selected often hinge on personal whims and prejudices. Only rarely are they chosen by consensus or based on established rules or procedures. The disturbing impression one receives of paleontologic studies is the apparently pervasive attitude that “if it's different, it must be given a new name.”