3D digital endocast of the Early Miocene (Colhuehuapian) Sipalocyon externa (Metatheria, Sparassodonta) - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2020

3D digital endocast of the Early Miocene (Colhuehuapian) Sipalocyon externa (Metatheria, Sparassodonta)

Résumé

The skull of Sipalocyon externa Ameghino, 1902 (Hathliacynidae) from Sacanana, Chubut, Sarmiento Formation, Colhuehuapian age, is studied (MACN-CH 1911). We first record the taxon for this locality, which includes the sparassodonts Acrocyon riggsi Simpson 1930 and a large Borhyaenoidae. The skull is almost complete and was studied through µCT-scanning, representing the first digital encephalic cavity cast(c) for Sparassodonta and one of the few known for stem marsupials. Body mass of the specimen was estimated based on teeth measurements, following Gordon´s equations (1.7kg), and skull centroid-size inspired by Zelditch (2.8kg). Considering the mean body mass, its encephalization quotient with and without olfactory bulbs is respectively: 0.32 and 0.30 (Jerison equations) or 0.41 and 0.38 (Eisenberg equations). The estimates for S. externa stand between that recorded by Macrini for the marsupials Didelphis virginiana (Kerr, 1792) and Dasyurus hallucatus Gould, 1842 but are larger than those of the stem marsupial Pucadelphys andinus Marshall and De Muizon, 1988. The olfactory bulbc represents 5.88% of the total endocranial volume, which is smaller than the values for P. andinus (11.7%) and other marsupials (8%–11%). The paraflocculusc corresponds to 2.65%, representing a large proportion of the endocast. This agrees with a deep subarquate fossa (a primitive condition for Metatheria). Vascular organization is largely conservative in this species. Similar to other sparassodonts, the major venous drainage from the endocranium was through the cerebrospinal system instead of jugular vein. In addition, we detected for the first time in this group an accessory transverse sinus enclosed by cranial bone. *This is a contribution to project PICT 2015-966
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Dates et versions

hal-03100804 , version 1 (07-01-2021)

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  • HAL Id : hal-03100804 , version 1

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Charlène Gaillard, Sergio Daniel Tarquini, Santiago Hernández del Pino, S. Ladevèze, Analia Forasiepi. 3D digital endocast of the Early Miocene (Colhuehuapian) Sipalocyon externa (Metatheria, Sparassodonta). Reunión de Comunicaciones de la Asociación Paleontológica Argentina, Nov 2019, La Plata, Argentina. pp.R81. ⟨hal-03100804⟩
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