Insights into South American Native Ungulate and Caviomorph Paleobiology

In the five chapters of this dissertation, I investigate the paleobiology of SouthAmerican native ungulates (SANUs) and caviomorph rodents. Although these studies involve different taxonomic groups and employ disparate methods, most rely on previously undescribed fossils to interrogate broader evolutionary questions. In the first chapter, I describe early Miocene litopterns (a group of SANUs) from Pampa Castillo, Aysén Region, Chile, and perform a phylogenetic analysis of one of its subgroups, Proterotheriidae. Litoptern taxa from Pampa Castillo include the macraucheniid Theosodon and proterotheriids Thoatherium and Picturotherium, corroborating the fauna’s assignment to the Santacrucian South American land mammal age (SALMA). My phylogenetic analysis, which indicates that “Anisolambdidae” forms a non-monophyletic cluster within Proterotheriidae, is the foundation of a new stem-based definition for Proterotheriidae. This chapter was published in the Journal of Systematic Palaeontology in 2020. My second chapter describes two new proterotheriids from the middle Miocene of Quebrada Honda, Tarija Department, Bolivia, and analyzes litoptern diversity and body size evolution in a phylogenetic context. These taxa, Olisanophus riorosarioensis gen. et sp. nov. and Olisanophus akilachuta gen. et sp. nov., greatly clarify proterotheriid evolution in mid-latitude South America. The diversity analysis indicates that these groups were more diverse than previously appreciated, particularly during the Paleogene. Macraucheniids increased in body size throughout the Cenozoic, whereas proterotheriids followed a similar trend during the Paleogene, but did not change in size during the Neogene. This chapter was published in Ameghiniana in 2020. Cavioid, chinchilloid, and erethizontoid caviomorph rodents from Pampa Castillo are described in the third chapter. Cavioids are represented by Luantus minor, Eocardia cf. excavata, and Neoreomys australis, the last of which is the most abundant