Cranial Anatomy and Paleoneurology of the Extinct Sloth Catonyx tarijensis (Xenarthra, Mylodontidae) From the Late Pleistocene of Oruro, Southwestern Bolivia

Abstract

Extinct scelidotheriine sloths are among the most peculiar fossil mammals from South America. In recent decades, the external cranial anatomy of Pleistocene scelidotheres such as Scelidotherium, Catonyx, and Valgipes has been the subject of numerous studies, but their endocranial anatomy remains almost completely unknown. Today, computed tomographic (CT) scanning methodologies permit the exploration of previously inaccessible anatomical areas through a completely non-destructive process. For this reason, we undertook an analysis of the external and internal cranial anatomy of Catonyx tarijensis from the late Pleistocene of the Department of Oruro, in southwestern Bolivia. One particularly well-preserved specimen allowed detailed observation of all the main cranial osteological features, including the ear region and an almost complete hyoid apparatus, previously unknown for this taxon. Moreover, CT-scanning and subsequent elaboration of digital models of this specimen allowed observation of the brain cavity and cranial sinuses, and reconstruction of the trajectory of the main cranial nerves for the first time in an extinct scelidotheriine sloth. Additionally, we recovered the first three-dimensional reconstructions of the nasal cavity and the turbinates of an extinct sloth. In contrast to the usual depiction, the combined information from the external and internal anatomy suggests reduced lingual protrusion in Catonyx tarijensis, or at least a consistently more limited protrusion of the tongue in comparison with other mylodontid sloths such as Glossotherium robustum. The new morphological information recovered from this extinct sloth is compared with the available information for both extant and extinct forms, providing insights in the paleobiology of the extinct species. The present study reveals the importance of applying these novel non-destructive techniques to elucidate the evolutionary history of sloths.

Osteología Craneana Y Taxonomía De Pronothrotherium (Xenarthra, Folivora, Nothrotheriidae) Del Mioceno Tardío–plioceno Temprano De La Provincia De Catamarca (Argentina)

“…6). It is interposed between the lacrimal dorsolaterally and the maxilla ventromedially, excluding any orbital contact between the lacrimal and the maxilla, as in Nothrotheriops (Stock, 1925), as well as basal megatherioids, Eucholoeops and other megalonychids, Bradypus, and scelidotheriine mylodontids (Gaudin, 2004;Gaudin et al, 2015; but see Boscaini et al, 2020a). The jugal contacts the frontal posterodorsally.…”

: The sloths Scelidotheriinae (Xenarthra, Folivora): taxonomy, biocronology, and biogeography

“…El género Catonyx se registra durante el Pleistoceno temprano-tardío de Argentina, Pleistoceno tardío de Bolivia, Uruguay, Chile, Perú y Ecuador (Corona et al, 2013;, Miño-Boilini, 2016, Miño-Boilini et al, 2019b, Boscaini et al, 2020. En Argentina, se recuperaron restos en las provincias de Buenos Aires, Corrientes, Córdoba, Salta, Tucumán, Entre Ríos y San Luis (Miño-Boilini, 2016).…”

“…Fuera de Argentina se registra durante el Pleistoceno medio-tardío del valle de Tarija y Padcaya (Coltorti et al, 2007;Miño-Boilini et al, 2019b). Recientemente, Boscaini et al (2020) refirieron nuevos materiales provenientes del Pleistoceno tardío (Departamento de Oruro) a C. tarijen-sis, este registro amplia el rango la distribución a latitudes más septentrionales, así como a las altas altitudes del Altiplano boliviano. También la especie es registrada en el Pleistoceno tardío de Uruguay (Departamento San José) (Corona et al, 2013).…”

Comparative anatomy and phylogenetic contribution of intracranial osseous canals and cavities in armadillos and glyptodonts (Xenarthra, Cingulata)

“…External cranial and postcranial skeletal anatomy are already well known for many groups within Cingulata, but the internal cranial anatomy remains understudied. However, its study has already provided data of systematic interest for both the extant and extinct xenarthran diversity (Billet et al, 2015;Billet et al, 2017;Boscaini et al, 2020;Boscaini et al, 2018;Fernicola et al, 2012;Tambusso & Fariña, 2015a;Tambusso & Fariña, 2015b;Tambusso et al, 2021;Zurita et al, 2011). Intracranial osseous canals provide important pathways for innervation and vascularization of the head (Evans & de Lahunta, 2012).…”