DIVERSIFICATION PATTERNS AND THE ORIGIN OF CAVIOIDEA SENSU STRICTO: FOSSILS, GHOST LINEAGES, AND MOLECULAR CLOCK ESTIMATES

PÉREZ, M. E.; POL, D.

LAS VEGAS

Congreso; 71 SOCIETY OF VERTEBRATE PALEONTOLOGY; 2011

Cavioidea sensu stricto is broadly distributed in South America and is currently represented by cavies, maras and capybaras. These forms are divergent and include the largest body the crown group of Cavioidea s.s., which has an abundant fossil record in post-Colloncuran sediments of South America. The stem group includes an assemblage of fossil taxa recorded from the Deseadan to the Colloncuran in the southern half of South America. The a morphological cladistic study. Although previous studies characterized the evolution of Cavioidea s.s. along a single phyletic line, our analysis shows that the history of the group (late Oligocene), was previously undetected, and generated the basal cavioid Asteromys and all major lineages leading to later appearing protohypsodont species. The second radiation can be traced back to the Santacrucian (early Miocene), marking the appearance of numerous euhypsodont lineages. The third radiation is evidenced by the early appearance of Prodolichotis of Laventan age (middle Miocene) and indicates the minimum age for the origin of crown cavioids. Bayesian relaxed molecular clock estimates (using four genes of ten cavioids) provided 95% highest posterior density (HPD) for the age of this node that range between 11.6 and 24.7 Ma, with a maximum probability estimate of 17 Ma (predating the this taxon. Here we report the internal morphology of the splanchnocranium of P. catalaunicus (IPS21350, holotype) by using non-invasive, computed-tomography techniques. This specimen displays a restricted maxillary sinus that expands posteriorly occupying the ethmoidal area, as in the Miocene pongine Sivapithecus and extant orangutans (Pongo). The frontal area of Pierolapithecus is characterized by the lack of a true frontal sinus, being occupied by a slight porosity, thus differing from the pneumatized condition of most fossil and extant great apes (except for Pongo and Sivapithecus). The nasolacrimal duct is less vertically-oriented than in extant African apes (Pan and Gorilla), thus more closely resembling the procumbent condition of orangutans, which might be interpreted as a pongine synapomorphy correlated to the greater projection of the nasals. The largest development of the turbinals is attained quite posteriorly, over the distal M2 level, thus more closely resembling orangutans (M3 level) than African apes (M1 level). Due to bone damage, it cannot be ascertained whether the premaxilla minimally overlaped the hard palate, althought it surely displayed a more primitive condition than extant great apes. Overall, the internal facial anatomy of Pierolapithecus more closely resembles that of the Pongo-clade than that of African apes (Homininae), by displaying several putative pongine synapomorphies that suggest that the former might be interpreted as a stem Ponginae s.l. (including both Dryopithecini and Pongini) instead of a stem Hominidae or Homininae (as previously suggested).