New mandibular remains of Callistoe (Metatheria, Sparassodonta) reveal unexpected anatomical, functional, and evolutionary aspects of this carnivorous genus

BABOT, M. JUDITH; ROUGIER, GUILLERMO W.; GARCÍA-LÓPEZ, DANIEL A.; BERTELLI, SARA B.; HERRERA, CLAUDIA M.; DERACO, M. VIRGINIA; GIANNINI, NORBERTO P.

Vertebrate Zoology

Pensoft

Lugar: Frankfurt; Año: 2022 vol. 72 p. 469 - 485

1864-5755

We present a detailed description of the anatomy of the dentary and lower teeth of a new specimen of Callistoe vincei, a largecarnivorous metatherian from the Eocene (?Ypresian) of northwestern Argentina. The recently collected specimen is a young adultrepresented by a partial right dentary with the canine, p1, roots of p3, and very well-preserved m1 to m4. The description includesa comparison with the holotype specimen, a much older individual, and other closely related large sparassodonts (e.g., Armini-heringia). The analysis of this new material allowed identifying plesiomorphic molar features in Callistoe, such as the presence ofa reduced metaconid on the m3 and a tricuspated, basined talonid on m1–m3. We also described the mesowear facets in the lowerdentition, showing that the self-sharpening facet typically present in extinct and extant placental and some marsupial carnivorousforms, was absent in Callistoe. The presence of a short-term cutting edge in the trigonid related to the thinness of the enamel layer,and the associated tooth wear susceptibility, were likely compensated by a dental mechanism (overeruption) to maintain occlusalcontact among antagonist teeth. This process could explain the marked extrusion of the tooth roots observed in Callistoe as well asin other large closely related members of the group.