DOI: 10.3897/vz.72.e86348

Authors: Omar Rafael Regalado Fernández, Ingmar Werneburg

Abstract: A literature review showed that there is not a defined consensus on what specimens belong to Plateosaurus in current phylogenetic analyses, and after the assignation of SMNS 13200 as the neotype for Plateosaurus, the specimen composition of Plateosaurus as an operational taxonomic unit (OTU) needs to be addressed in further iterations of phylogenetic analyses. At least one of the specimens used to illustrate plateosaurian anatomy contains several characters identified in more derived sauropodomorphs commonly referred to as massopodans. This partial skeleton, traditionally known as specimen ‘GPIT IV’, was found in the lower dinosaur bone bed of the Obere Mühle, a Trossingen Formation outcrop, during an excavation in 1922 near the city of Tübingen, Germany. The holotype of Plateosaurus trossingensis and several other specimens referred to as this species were found in this level, which was initially interpreted as a synchronic deposit of animals. However, the current understanding of the Trossingen Formation indicates that this bed was probably a constant accumulation of carcasses through miring and transport down a river for hundreds of years. In this work, a framework to compare phylogenetic signals with morphological and histological data is provided to help in the species delineation of Plateosaurus, and support is found to refer the historic specimen ‘GPIT IV’ as a new genus and a new species.

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DOI: 10.3897/vz.72.e82709

Authors: M. Judith Babot, Guillermo W. Rougier, Daniel A. García-López, Sara B. Bertelli, Claudia M. Herrera, M. Virginia Deraco, Norberto P. Giannini

Abstract: We present a detailed description of the anatomy of the dentary and lower teeth of a new specimen of Callistoe vincei, a large carnivorous metatherian from the Eocene (?Ypresian) of northwestern Argentina. The recently collected specimen is a young adult represented by a partial right dentary with the canine, p1, roots of p3, and very well-preserved m1 to m4. The description includes a comparison with the holotype specimen, a much older individual, and other closely related large sparassodonts (e.g., Arminiheringia). The analysis of this new material allowed identifying plesiomorphic molar features in Callistoe, such as the presence of a reduced metaconid on the m3 and a tricuspated, basined talonid on m1–m3. We also described the mesowear facets in the lower dentition, showing that the self-sharpening facet typically present in extinct and extant placental and some marsupial carnivorous forms, 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 occlusal contact among antagonist teeth. This process could explain the marked extrusion of the tooth roots observed in Callistoe as well as in other large closely related members of the group.

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