Enamel thickness in the Middle Miocene great apes Anoiapithecus, Pierolapithecus and Dryopithecus.

On the basis of industrial computed tomography, relative enamel thickness (RET) is computed in three Middle Miocene (ca 11.9-11.8 Ma) hominoids from Abocador de Can Mata (Vallès-Penedès Basin, Catalonia, Spain): Pierolapithecus catalaunicus from BCV1 and Anoiapithecus brevirostris from C3-Aj, interpreted as stem hominids; and Dryopithecus fontani from C3-Ae of uncertain phylogenetic affinities. Pierolapithecus displays an average RET value of 19.5, Anoiapithecus of 18.6 and Dryopithecus of 10.6. The thick-enamelled condition of Pierolapithecus and Anoiapithecus is also characteristic of afropithecids, including the more derived kenyapithecins from the early Middle Miocene of Eurasia (Griphopithecus and Kenyapithecus). Given the presence of other dentognathic and craniofacial similarities, thick enamel may be interpreted as a symplesiomorphy of the Hominidae (the great ape and human clade), which would have been later independently modified along several lineages. Given the correlation between thick enamel and hard-object feeding, our results suggest that thick enamel might have been the fundamental adaptation that enabled the out-of-Africa dispersal of great-ape ancestors and their subsequent initial radiation throughout Eurasia. The much thinner enamel of Dryopithecus is difficult to interpret given phylogenetic uncertainties, being either a hominine synapomorphy or a convergently developed feature.

Orang-like manual adaptations in the fossil hominoid Hispanopithecus laietanus: first steps towards great ape suspensory behaviours.

Morphological and biometrical analyses of the partial hand IPS18800 of the fossil great ape Hispanopithecus laietanus (=Dryopithecus laietanus), from the Late Miocene (about 9.5Ma) of Can Llobateres (Catalonia, Spain), reveal many similarities with extant orang-utans (Pongo). These similarities are interpreted as adaptations to below-branch suspensory behaviours, including arm-swinging and clambering/postural feeding on slender arboreal supports, due to an orang-like double-locking mechanism. This is confirmed by the long and highly curved phalanges of Hispanopithecus. The short and stout metacarpals with dorsally constricted heads, together with the dorsally extended articular facets on proximal phalanges, indicate the persistence of significant degrees of palmigrady. A powerful grasping capability is indicated by the great development of basal phalangeal tubercles, the marked insertions for the flexors on phalangeal shafts and the large pits for the collateral ligaments. The morphology of the Hispanopithecus long bones of the hand indicates a unique positional repertoire, combining orthogrady with suspensory behaviours and palmigrade quadrupedalism. The retention of powerful grasping and palmigrady suggests that the last common ancestor of hominids might have been more primitive than what can be inferred on the basis of extant taxa, suggesting that pronograde behaviours are compatible with an orthograde bodyplan suitable for climbing and suspension.

Canine reduction in the miocene hominoid Oreopithecus bambolii: behavioural and evolutionary implications.

The degree of canine size sexual dimorphism and relative canine size, which have been related to levels of agonistic behaviour amongst living anthropoid primates, together with relative molar size, are evaluated in the fossil hominoid Oreopithecus bambolii from the Late Miocene of Italy. Although Oreopithecus displays a significant degree of canine height sexual dimorphism, using allometric techniques and body mass estimates for fossil species, it is shown that Oreopithecus males are microdont (smaller postcanine as well as canine teeth than expected) when compared to most living hominoids and its putative ancestor Dryopithecus. Canine reduction in Oreopithecus includes both crown height and, especially, basal area, and most closely resembles the condition found in the pygmy chimpanzee Pan paniscus. Interestingly, it had been previously proposed that Oreopithecus displays, like pygmy chimpanzees, a paedomorphic cranial morphology resulting in a reduction of facial prognathism, which could be related to microdontia in both taxa. Independent canine reduction in several anthropoid lineages (including hominids and P. paniscus) has been related to a relaxation of the selection pressure favouring canine use as a weapon. Although changes in socio-sexual behaviour, as documented in P. paniscus, cannot be currently discarded in Oreopithecus, canine reduction could be also alternatively (although not exclusively) interpreted as an aspect of generalized microdontia. The latter is best considered an adaptive readjustment required by the paedomorphic reduction of prognathism and the resulting lack of space to accommodate the adult dentition. This mechanism of canine reduction highlights the significance of developmental constraints in evolution and had not been previously suggested for any anthropoid primate.

Egarapithecus narcisoi, a new genus of Pliopithecidae (primates, catarrhini) from the Late Miocene of Spain.

Pliopithecid remains from the Spanish locality of Torrent de Febulines (Late Vallesian, MN 10), consisting of right and left mandibular fragments with partial tooth rows and an isolated P(3) probably belonging to the same individual, are described and assigned to Egarapithecus narcisoi gen. et sp. nov. (Pliopithecidae, Crouzeliinae). This is a highly derived species dated at around 9 Ma (Ma = 10(6) years), representing the latest appearance of the family in the European continent. Morphologically it is the most distant member from the inferred primitive pliopithecid morphotype, displaying many autapomorphies that notably accentuate those of the remaining Crouzeliinae. A cladistic analysis based on lower cheek teeth, performed in order to tentatively assess the phylogenetic relationships of Egarapithecus within the Crouzeliinae, indicates that several equally parsimonious cladograms are possible in the light of current evidence. This is due to uncertainties regarding the position of Plesiopliopithecus and Crouzelia (here considered distinct genera), as a result of missing characters and the significant degree of homoplasy apparently involved in crouzeliine dental evolution. Whether Egarapithecus is more closely related to Crouzelia or to Anapithecus (the latter hypothesis tentatively favored here) cannot be definitively resolved with the currently available material and deserves further investigation. It is clear, however, that Egarapithecus is one of the more derived and specialized members of the Pliopithecidae.

Brief communication: Cranial reconstruction of Dryopithecus.

This paper presents the first three-dimensional reconstruction of the cranium of the European Miocene ape, Dryopithecus. The reconstruction is based on remains collected from Can Llobateres, Spain (CLI 18000; Dryopithecus laietanus), D. fontani (St. Gaudens), and D. brancoi (Kordos and Begun [1997] Am. J. Phys. Anthropol. 103:277-294). Previously unrecognized facial fragments from CLI 18000 were included in the reconstruction. The result shows that Dryopithecus had a relatively short face, with a rather short and well-rounded neurocranium. From the lateral perspective, the face is concave at midface, and on the cranium the temporal lines run parallel to each other without forming a sagittal crest.