DIGITAL RECONSTRUCTION OF THE INNER EAR OF PROTYPOTHERIUM (MAMMALIA; NOTOUNGULATA)

AGUIAR, B.; ULLOA-GUAIQUIN, KAREN; PAULINA-CARABAJAL, ARIANA; VERA, BÁRBARA

General Roca

Otro; Reunión de la Asociación Paleontológica Argentina; 2023

Asociación Paleontológica Argentina

Notoungulata includes diverse native ungulates that played a vital role in South America´sCenozoic ecosystems in terms of variety, form, and lifestyles. Among them, theInteratheriinae Protypotherium stands out as the most diverse and widely distributedNeogene genus. MAPBAR 8371 (curated in the Museo Paleontológico Bariloche) wasassigned to Protypotherium sp. This specimen is a well-preserved skull from the CollónCurá Formation (Comallo, Río Negro Province, Argentina). It conserves most of theneurocranium, craniofacial region, and molariform series. We digitalized the skull usinga Cone Beam Computed Tomograph (in Consultorios Albarracín, San Carlos deBariloche) to explore the internal anatomy, especially the inner ear. The performedsegmentation was made with the software Mimics (21.0). In the inner ear a segment ofthe semicircular canals, the vestibular region, and the cochlea, crucial elements forbalance and hearing were identified. There are also anterior and posterior ampullaecanals, as well as a section of the crus commune. In the vestibular region, specifically onits lateral-external face, the fenestra vestibuli and the fenestra cochleae were observed.The bulge, corresponding to the spherical recess containing the saccule, is conspicuousand positioned above the fenestra vestibuli. The morphology of the vestibule in thisspecimen, exhibiting significant dilation, is comparable to that described in Cochilius, anearly Miocene Interatheriinae. In the right inner ear of MAPBAR 8371, the cochlear canalis fully preserved, with two complete turns counted. This is consistent with that ofdescribed in other notoungulates, such as Pachyrukhos, Cochilius, and Altitypotherium,while it, differs from Notostylops (2.25). These results suggest that the inner ear ofProtypotherium shares both similarities and distinctions with other Typotheria members,particularly Cochilius and Notostylops. In order to provide more detailed descriptions, notonly of the inner ear but also of the neuroanatomy and craniofacial soft tissues, theinternal anatomy in these groups needs to be more extensively explored.