Taxonomic attribution of the La Grive hominoid teeth

The reconstructed cranium of Pierolapithecus and the evolution of the great ape face

Pierolapithecus catalaunicus (~12 million years ago, northeastern Spain) is key to understanding the mosaic nature of hominid (great ape and human) evolution. Notably, its skeleton indicates that an orthograde (upright) body plan preceded suspensory adaptations in hominid evolution. However, there is ongoing debate about this species, partly because the sole known cranium, preserving a nearly complete face, suffers from taphonomic damage. We 1) carried out a micro computerized tomography (CT) based virtual reconstruction of the Pierolapithecus cranium, 2) assessed its morphological affinities using a series of two-dimensional (2D) and three-dimensional (3D) morphometric analyses, and 3) modeled the evolution of key aspects of ape face form. The reconstruction clarifies many aspects of the facial morphology of Pierolapithecus. Our results indicate that it is most similar to great apes (fossil and extant) in overall face shape and size and is morphologically distinct from other Middle Miocene apes. Crown great apes can be distinguished from other taxa in several facial metrics (e.g., low midfacial prognathism, relatively tall faces) and only some of these features are found in Pierolapithecus, which is most consistent with a stem (basal) hominid position. The inferred morphology at all ancestral nodes within the hominoid (ape and human) tree is closer to great apes than to hylobatids (gibbons and siamangs), which are convergent with other smaller anthropoids. Our analyses support a hominid ancestor that was distinct from all extant and fossil hominids in overall facial shape and shared many features with Pierolapithecus. This reconstructed ancestral morphotype represents a testable hypothesis that can be reevaluated as new fossils are discovered.

A reassessment of the distinctiveness of dryopithecine genera from the Iberian Miocene based on enamel-dentine junction geometric morphometric analyses

A vast diversity of catarrhines primates has been uncovered in the Middle to Late Miocene (12.5-9.6 Ma) of the Vallès-Penedès Basin (northeastern Spain), including several hominid species (Pierolapithecus catalaunicus, Anoiapithecus brevirostris, Dryopithecus fontani, Hispanopithecus laietanus, and Hispanopithecus crusafonti) plus some remains attributed to 'Sivapithecus' occidentalis (of uncertain taxonomic validity). However, Pierolapithecus and Anoiapithecus have also been considered junior synonyms of Dryopithecus by some authors, which entail a lower generic diversity and an inflated intrageneric variation of the latter genus. Since the distinction of these taxa partly relies on dental features, the detailed and quantitative analysis of tooth shape might help disentangling the taxonomic diversity of these Miocene hominids. Using diffeomorphic surface matching and three-dimensional geometric morphometrics, we investigate the enamel-dentine junction shape (which is a reliable taxonomic proxy) of these Miocene hominids, with the aim of investigating their degree of intra- and intergeneric variation compared with that of extant great ape genera. We conducted statistical analyses, including between-group principal component analyses, canonical variate analyses, and permutation tests, to investigate whether the individual and combined (i.e., Dryopithecus s.l.) variation of the extinct genera exceeds that of the extant great apes. Our results indicate that Pierolapithecus, Anoiapithecus, Dryopithecus, and Hispanopithecus show morphological differences of enamel-dentine junction shape relative to the extant great apes that are consistent with their attribution to different genera. Specifically, the variation displayed by the Middle Miocene taxa combined exceeds that of extant great ape genera, thus undermining the single-genus hypothesis. 'Sivapithecus' occidentalis specimens fall close to Dryopithecus but in the absence of well-preserved comparable teeth for Pierolapithecus and Anoiapithecus, their taxonomic attribution remains uncertain. Among the Hispanopithecus sample, IPS1802 from Can Llobateres stands out and might either be an outlier in terms of morphology, or represent another dryopithecine taxon.

Can Pallars i Llobateres: A new hominoid-bearing locality from the late Miocene of the Vallès-Penedès Basin (NE Iberian Peninsula)

In the Iberian Peninsula, Miocene apes (Hominoidea) are generally rare and mostly restricted to the Vallès-Penedès Basin. Here we report a new hominoid maxillary fragment with M² from this basin. It was surface-collected in March 2017 from the site of Can Pallars i Llobateres (CPL, Sant Quirze del Vallès), where fossil apes had not been previously recorded. The locality of provenance (CPL-M), which has delivered no further fossil remains, is located very close (ca. 50 m) to previously known CPL outcrops, and not very far (ca. 500 m in NW direction) from the classical hominoid-bearing locality of Can Poncic 1. Here we describe the new fossil and, based on the size and proportions of the M², justify its taxonomic attribution to Hispanopithecus cf. laietanus, a species previously recorded from several Vallesian sites of the Vallès-Penedès Basin. Based on the associated mammalian fauna from CPL, we also provide a biochronological dating and a paleoenvironmental reconstruction for the site. The associated fauna enables an unambiguous correlation to the Cricetulodon hartenbergeri - Progonomys hispanicus interval local subzone, with an estimated age of 9.98-9.73 Ma (late Vallesian, MN10). Therefore, CPL-M is roughly coeval with the Hispanopithecus laietanus-bearing localities of Can Llobateres 1 and Can Feu 1, and minimally older than those of La Tarumba 1 and Can Llobateres 2. In contrast, CPL-M is younger than the early Vallesian (MN9) localities of Can Poncic 1 (the type locality of Hispanopithecus crusafonti) as well as Polinyà 2 (Gabarró) and Estació Depuradora d'Aigües Residuals-Riu Ripoll 13, where Hispanopithecus sp. is recorded. The associated fauna from CPL indicates a densely forested and humid paleoenvironment with nearby freshwater. This supports the view that Hispanopithecus might have been restricted to dense wetland forests soon before its extinction during the late Vallesian, due to progressive climatic deterioration. Coupled with the existence of other fossiliferous outcrops in the area, this find is most promising for the prospect of discovering additional fossil hominoid remains in the future.