WHAT IS A GIRAFFE-LIKE CAMEL? A TAXONOMIC REVISION OF THE MIOCENE CAMEL, OXYDACTYLUS

Camels were a common and diverse group in North America from their origin in the late middle Eocene through the late Pleistocene, but the systematics of most groups is poorly understood, especially in light of the huge unstudied collections in the American Museum of Natural History. We undertook a systematic study of the early Miocene genus Oxydactylus, from the late Arikareean and early Hemingfordian. Prior to this study, there were eight named species referred to as Oxydactylus, which had become a taxonomic wastebasket for all early Miocene camels with long legs and long necks. We conducted a suite of over 24 measurements of skulls, teeth and jaws, as well as selected skeletal elements. Using univariate statistical methods (mean, standard deviation, and coefficient of variability, or CV) and bivariate analytical methods, we tried to see how many different species could be discriminated. CVs of the total samples were high, but CV<10 for the least variable tooth measurements. In addition, CVs are known to be high in many groups of artiodactyls. Bivariate plots showed complete overlap of all the “species” with no breaks that could be used to separate size groups. When the total variability of the sample is considered, and the effects of sexual dimorphism identified, there is no justification for more than a single species, Oxydactylus longipes Peterson, 1904. All other names that have been given to specimens are junior synonyms, including O. benedentatus, O. campestris, O. lacota, O. lulli, and O. wyomingensis.