TAXONOMIC REVIEW OF THE GENUS Asmithwoodwardia (MAMMALIA: PANPERISSODACTYLA LITOPTERNA) OF THE PALEOGENE OF SOUTH AMERICA

FERREIRA T. Z.; BERGQVIST, LILIAN P.; GELFO, J. N.

Bahía

Congreso; VII Congresso Latinoamericano de Paleontologia de Vertebrados; 2022

The genus Asmithwoodwardia includes the species A. subtrigona (Eocene, Patagonia, Argentina) and A. scotti (Paleogene, Rio de Janeiro, Brazil). This genus was originally assigned to the Phenacodontidae, later reassigned to the Hyopsodontidae and, currently, to the Didolodontidae or Protolipternidae, depending on different authors’ views. One of the reasons for so many reassignments is that the holotype of A. subtrigona, an isolated molar, has been interpreted both as an M2 and an M3 by different authors, leading to different taxonomic interpretations. The monophyly of the genus has also been questioned. Therefore, the present work’s objectives are: (1) identifying the dental locus of the holotype of A. subtrigona using morphometric methods, (2) reviewing the genus Asmithwoodwardia. We studied 31 specimens of the genus housed at the Museu de Ciências da Terra (Rio de Janeiro, Brasil), the Laboratorio de Investigaciones en Evolución y Biodiversidad (Esquel, Argentina), the Museo de La Plata (La Plata, Argentina) and the Museo Argentino de Ciencias Naturales “Bernadino Rivadavia” (Buenos Aires, Argentina). To identify the tooth’s locus, we used linear and geometric morphometrics, and also morphological analysis. Other M1-3 of bunodont ungulates were used for comparison. For the linear morphometric analysis, we used the angle between the tooth’s distal face and the alignment of the paracone and metacone; for the geometric morphometric, we used 17 landmarks. On the morphological analysis, we observed the development and placement of the metacone. The holotypes of A. subtrigona and A. scotti were coded and included in a phylogenetic matrix of 87 characters and 26 taxa to test their relationships with other bunodont ungulates. Every analysis suggested a greater similarity of the holotype of A. subtrigona with M3s, corroborating, by more objective methods, previous interpretations of it as being an M3. The phylogenetic analysis agreed with previous interpretations of the polyphyletic nature of this genus. Currently, A. scotti represents a taxon present at lower latitudes, with a simpler structure (narrower M3 lacking a hypocone), while A. subtrigona represents a more advanced form, present at the higher latitudes of Patagonia. [CNPq; FAPERJ]