ABSTRACT

We describe a large collection of mesotheriid notoungulate specimens, including a well-preserved cranium, from the early to middle Miocene locality of Cerdas, Bolivia. We attempt to classify the specimens into dental wear groups (i.e., ontogenetic groups) based on tooth size, morphology, and position of the posterior mental foramen, and we compare these specimens to those from other middle-latitude localities in Chile (Chucal) and Bolivia (Achiri, Choquecota, Quebrada Honda, and Nazareno). Our metric analyses, using bivariate plots and coefficients of variation (CVs), indicate that nearly all Cerdas specimens pertain to a single species. Our phylogenetic analysis indicates that this species, 'Plesiotypotherium' minus Villarroel 1978, should be referred to a different genus, more closely related to Altitypotherium Croft et al. 2004 (Chucal) and/or Microtypotherium Villarroel 1974b (Choquecota). We do not refer 'P.' minus to a new genus at this time, pending revision of other early to middle Miocene mesotheriids from Bolivia. A smaller species, represented by two specimens, may also be present at Cerdas.

Beth Townsend. Department of Anatomy, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, 85308, USA.
Darin A. Croft. Department of Anatomy, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA.

Key Words: Body Size, CV, Mesotheriidae, Notoungulata, Plesiotypotherium, South America, Tertiary