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.

Dental Microwear Variability on Buccal Tooth Enamel Surfaces of Extant Catarrhini and the Miocene Fossil Dryopithecus laietanus (Hominoidea)

Analyses of buccal tooth microwear have been used to trace dietary habits of modern hunter-gatherer populations. In these populations, the average density and length of striations on the buccal surfaces of teeth are significantly cor-related with the abrasive potential of food items consumed. In non-human pri-mates, tooth microwear patterns on both occlusal and buccal wear facets have been thoroughly studied and the results applied to the characterization of dietary habits of fossil species. In this paper, we present inter- and intra-specific buccal microwear variability analyses in extant Cercopithecoidea (Cercopithecus mitis, C. neglectus, Chlorocebus aethiops, Colobus spp., Papio anubis) and Hominoidea (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus). The results are tentatively compared to buccal microwear patterns of the Miocene fossils Dryopithecus and Oreopithecus. Significant differences in striation density and length are found among the fossil taxa studied and the extant primates, suggesting that buccal microwear can be used to identify dietary differences among taxa. The Dryopithecus buccal microwear pattern most closely resembles that of abrasive, tough plant foods consumers, such as the gorilla, in contrast to stud-ies of dental morphology that suggest a softer, frugivorous diet. Results for Oreopithecus were equivocal, but suggest a more abrasive diet than that previously thought.

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.

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.

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.

A finding of oligocene primates on the European continent

In this paper, we provide evidence that contrary to the current view, primates on the European continent did survive the dramatic extinction/origination event across the Eocene/Oligocene boundary 34 million years ago that severely affected the Eurasian mammal communities (the European "Grande Coupure" and the Asian "Mongolian Remodeling"). The survival of a mouse-sized omomyid for at least 2 million years, recorded in two localities of the Lower Stampian (Lower Oligocene) in a well dated stratigraphic series of fluviatile sediments in the north oriental sector of the Ebro Basin (Northeastern Spain), reflects the size-related survival pattern described recently for other coeval mammalian taxa.

Oreopithecus was a bipedal ape after all: evidence from the iliac cancellous architecture

Textural properties and functional morphology of the hip bone cancellous network of Oreopithecus bambolii, a 9- to 7-million-year-old Late Miocene hominoid from Italy, provide insights into the postural and locomotor behavior of this fossil ape. Digital image processing of calibrated hip bone radiographs reveals the occurrence of trabecular features, which, in humans and fossil hominids, are related to vertical support of the body weight, i.e., to bipedality.

Ape-like or hominid-like? The positional behavior of Oreopithecus bambolii reconsidered

Comparative morphological and functional analyses of the skeletal remains of Oreopithecus bambolii, a hominoid from the Miocene Mediterranean island of Tuscany-Sardinia (Italy), provides evidence that bipedal activities made up a significant part of the positional behavior of this primate. The mosaic pattern of its postcranial morphology is to some degree convergent with that of Australopithecus and functionally intermediate between apes and early hominids. Some unique traits could have been selected only under insular conditions where the absence of predators and the limitation of trophic resources play a crucial role in mammalian evolution.

A Dryopithecus skeleton and the origins of great-ape locomotion

The evolution of skeletal adaptations to orthograde postures, characteristic of extant hominoids, is of great interest as it provides the key to understanding the origins of apes and humans. We report here the recent discovery of an extraordinary partial skeleton of Dryopithecus laietanus from Can Llobateres (Spain). It provides evidence that orthograde postures and locomotion appeared at least 9.5 million years ago. Our results indicate that the body structure of this Miocene ape closely resembles that of extant hominoids and differs from the pronograde pattern of Miocene proconsulids in a set of important morphological characters. Dryopithecus also shows more traits reflecting structural adaptations for suspension than occurs in African apes. A similar positional behaviour is inferred for Sivapithecus indicus, thus strengthening previous hypotheses linking both Miocene forms with Pongo.