Search

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

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

Hegetotheriidae represents one of the most derived clades within the Order Notoungulata. Already diversified in the late Oligocene, its members, many of them with gliriform appearance, are conspicuous components of the terrestrial South American mammalian faunas up to the Pleistocene. However, the knowledge of their diversity during the Colhuehuapian South American Land Mammal Age (early Miocene) is still imperfect. Here it is described a new hegetotheriid, Hegetotheriopsis sulcatus n. gen. et sp., represented by a skull fragment with partial dentition from Colhuehuapian beds of the Sarmiento Formation at Bryn Gwyn, central Patagonia. Many mandibular fragments with teeth from this locality and other putative coeval localities at Northern Patagonia are referred tentatively to this new taxon. Hegetotheriopsis sulcatus shows a unique combination of cranial and dental characters, some previously known for archaeohyracid notoungulates (interpreted as the sister group of Hegetotheriidae) and others that typify to hegetotheriids. The phylogenetic analysis, based on a data matrix from previous studies, points out that Hegetotheriopsis sulcatus represents the earliest diverging hegetotheriid known so far, thus it cannot be classified within neither Hegetotheriinae nor Pachyrukhinae, the two subfamilies in which all hegetotheriids are traditionally included. The occurrence in Colhuehuapian levels of this taxon, more basal than others known for late Oligocene beds (Deseadan), adds at least a 4 million years ghost lineage to the paleontological record of this mammals., Hegetotheriidae constituye uno de los clados más derivados dentro del Orden Notoungulata. Ya diversificado en el Oligoceno tardío, sus representantes, muchos de aspecto gliriforme, son conspicuos componentes de las faunas de mamíferos terrestres sudamericanas hasta el Pleistoceno. Sin embargo, es limitado aún el conocimiento de la diversidad de hegetotéridos para la Edad Mamífero Colhuehuapense (Mioceno temprano). Aquí se describe un nuevo hegetotérido, Hegetotheriopsis sulcatus n. gen. et sp., representado por un fragmento craneano con gran parte de la dentadura procedente de capas colhuehuapeses de la Formación Sarmiento en Bryn Gwyn, Patagonia central. Varios fragmentos mandibulares con dientes procedentes de ésta y otras localidades presuntamente contemporáneas en el norte de Patagonia, se asignan tentativamente a este nuevo taxón. Hegetotheriopsis sulcatus presenta una combinación única de caracteres craneanos y dentarios, algunos previamente conocidos para los notoungulados arqueohirácidos (interpretados como el grupo hermano de Hegetotheriidae) y otros que tipifican a los hegetotéridos. El análisis filogenético, basado en la matriz de datos de estudios previos, señala que Hegetotheriopsis sulcatus constituye el hegetotérido más tempranamente divergente hasta ahora conocido, por lo que no puede ser clasificado dentro de Hegetotheriinae ni Pachyrukhinae, las dos subfamilias en las que tradicionalmente se incluyen a todos los hegetotéridos. La presencia en niveles de edad Colhuehuapense de este taxón, más basal que otros conocidos para capas del Oligoceno tardío (Edad Mamífero Deseadense), introduce un linaje fantasma de al menos 4 millones de años en el registro paleontológico de estos mamíferos.

Hegetotheriidae represents one of the most derived clades within the Order Notoungulata. Already diversified in the late Oligocene, its members, many of them with gliriform appearance, are conspicuous components of the terrestrial South American mammalian faunas up to the Pleistocene. However, the knowledge of their diversity during the Colhuehuapian South American Land Mammal Age (early Miocene) is still imperfect. Here it is described a new hegetotheriid, Hegetotheriopsis sulcatus n. gen. et sp., represented by a skull fragment with partial dentition from Colhuehuapian beds of the Sarmiento Formation at Bryn Gwyn, central Patagonia. Many mandibular fragments with teeth from this locality and other putative coeval localities at Northern Patagonia are referred tentatively to this new taxon. Hegetotheriopsis sulcatus shows a unique combination of cranial and dental characters, some previously known for archaeohyracid notoungulates (interpreted as the sister group of Hegetotheriidae) and others that typify to hegetotheriids. The phylogenetic analysis, based on a data matrix from previous studies, points out that Hegetotheriopsis sulcatus represents the earliest diverging hegetotheriid known so far, thus it cannot be classified within neither Hegetotheriinae nor Pachyrukhinae, the two subfamilies in which all hegetotheriids are traditionally included. The occurrence in Colhuehuapian levels of this taxon, more basal than others known for late Oligocene beds (Deseadan), adds at least a 4 million years ghost lineage to the paleontological record of this mammals., Hegetotheriidae constituye uno de los clados más derivados dentro del Orden Notoungulata. Ya diversificado en el Oligoceno tardío, sus representantes, muchos de aspecto gliriforme, son conspicuos componentes de las faunas de mamíferos terrestres sudamericanas hasta el Pleistoceno. Sin embargo, es limitado aún el conocimiento de la diversidad de hegetotéridos para la Edad Mamífero Colhuehuapense (Mioceno temprano). Aquí se describe un nuevo hegetotérido, Hegetotheriopsis sulcatus n. gen. et sp., representado por un fragmento craneano con gran parte de la dentadura procedente de capas colhuehuapeses de la Formación Sarmiento en Bryn Gwyn, Patagonia central. Varios fragmentos mandibulares con dientes procedentes de ésta y otras localidades presuntamente contemporáneas en el norte de Patagonia, se asignan tentativamente a este nuevo taxón. Hegetotheriopsis sulcatus presenta una combinación única de caracteres craneanos y dentarios, algunos previamente conocidos para los notoungulados arqueohirácidos (interpretados como el grupo hermano de Hegetotheriidae) y otros que tipifican a los hegetotéridos. El análisis filogenético, basado en la matriz de datos de estudios previos, señala que Hegetotheriopsis sulcatus constituye el hegetotérido más tempranamente divergente hasta ahora conocido, por lo que no puede ser clasificado dentro de Hegetotheriinae ni Pachyrukhinae, las dos subfamilias en las que tradicionalmente se incluyen a todos los hegetotéridos. La presencia en niveles de edad Colhuehuapense de este taxón, más basal que otros conocidos para capas del Oligoceno tardío (Edad Mamífero Deseadense), introduce un linaje fantasma de al menos 4 millones de años en el registro paleontológico de estos mamíferos.