The craniodental anatomy of Miocene apes from the Vallès-Penedès Basin (PrimatesHominidae): Implications for the origin of extant great apes

Resumen

In this doctoral dissertation, the craniodental fossil remains of Middle and Late Miocene hominoids from the Vallès-Penedès Basin (NE Iberian Peninsula) are described, with the aim to investigate the phylogenetic position of the recorded taxa as well as to revise their systematics and alfa-taxonomy. The need for this study is justified by the important number of cranial remains of these taxa recovered during the last decade. The dissertation therefore includes the description of some previously-unpublished dentognathic remains, as well as an exhaustive description of all the available cranial remains, with the aid of non-invasive techniques (computed tomography) enabling the observation of internal craniodental morphology. The studied remains are compared with other hominoids (both extant and extinct), and on this basis, previously-proposed phylogenetic hypotheses and taxonomic schemes are critically evaluated. Regarding previously-unpublished remains, two maxillary specimens from two Middle Miocene localities of the local stratigraphic series of Abocador de Can Mata (ACM, els Hostalets de Pierola) are described, being attributed to Anoiapithecus brevirostris, previously described based on a more complete specimen from one of these localities. The other specimen comes from ACM/C1-E*, which is correlated to subchron C5An.2n and has an estimated age of 12.4-12.3 Ma, thereby representing the oldest record (first appearance datum) of hominoids in the whole Iberian Peninsula. With regard to the systematics and alfa-taxonomy of the Vallès-Penedès hominoids, the comparisons of internal and external craniodental morphology (including dental occlusal morphology, relative enamel thickness, external cranial features, and paranasal sinuses) supports the recognition of five species and four distinct genera within a single subfamily Dryopithecinae (Primates: Hominoidea: Hominidae): the Middle Miocene Pierolapithecus catalaunicus, Anoiapithecus brevirostris and Dryopithecus fontani, included in tribe Dryopithecini; as well as the Late Miocene Hispanopithecus laietanus and Hispanopithecus crusafonti, included in tribe Hispanopithecini. The purported synonymy between both Pierolapithecus and Anoiapithecus with Dryopithecus is therefore rejected based on the presence of significant differences in cranial morphology, whereas the distinction between H. laietanus and the material from Rudabánya (Hungary) is reaffirmed at the (sub)genus level. Given the lack of cranial material and its more primitive dental morphology, the attribution of H. crusafonti to genus Hispanopithecus remains provisional. Comparisons of the Vallès-Penedès remains with those from the similarly-aged French locality of La Grive support the traditional attribution of the latter to D. fontani, so that Pierolapithecus is currently not recorded outside the Vallès-Penedès Basin. Finally, from a phylogenetic viewpoint, the various competing hypotheses previously-proposed for the Vallès-Penedès dryopithecines are evaluated in the light of their external and internal cranial morphology. These taxa are characterized by a mosaic of primitive hominoid features and more derived crown-hominid features, indicating that they are best interpreted as basal members of the great-ape-and-human clade (i.e., stem hominids). In particular, dryopithecines lack clear synapomorphies of both (shared by orangutans and their closest extinct relatives) and hominines (derived features shared by extant African apes), thus supporting the view that dryopithecines precede the pongine-hominine split. However, the lack of clear autapomorphies suggests that dryopithecines must not necessarily constitute a monophyletic clade.