3D geometric morphometrics analysis of mandibular fragments of Ouranopithecus macedoniensis from the late Miocene deposits of Central Macedonia, Greece.

OBJECTIVES: To explore mandibular shape differences between Ouranopithecus macedoniensis and a comparative sample of extant great apes using three-dimensional (3D) geometrics morphometrics. Other objectives are to assess mandibular shape variation and homogeneity within Ouranopithecus, explore the effects of size on mandibular shape, and explore the degree of mandibular sexual size dimorphism in Ouranopithecus. MATERIALS AND METHODS: The comparative sample comprises digitized mandibles from adult extant great apes. The 3D analysis includes three datasets: one with landmarks registered on the mandibular corpus and symphysis of mandibles preserving both sides, one on hemimandibles only, and one focused on the ramus and gonial area. Multivariate statistical analyses were conducted, such as ordination analyses (PCA), intra-specific Procrustes distances pairs, pairwise male-female centroid size differences, and correlation analyses. RESULTS: The male and female specimens of Ouranopithecus have mandibular shapes that are quite similar, although differences exist. The Procrustes distances results suggest more shape variation in Ouranopithecus than in the extant great apes. Ouranopithecus shows some similarities in mandibular shape to the larger great apes, Gorilla and Pongo. Moreover, the degree of sexual dimorphism in the small Ouranopithecus sample is greater than any of the great apes. Based on our correlation analyses of principal components (PC) with size, some PCs are significantly correlated with size, with correlation varying from moderate to substantial. DISCUSSION: This study attempted to understand better the variation within the mandibles of O. macedoniensis and the expression of sexual dimorphism in this taxon in more detail than has been done previously. The overall mandibular morphology of Ouranopithecus shows some similarities to those of the larger great apes, which likely reflects similarities in size. Compared to Gorilla and Pongo, O. macedoniensis shows an elevated degree of morphological variation, although limitations relating to sample size apply. Sexual dimorphism in the mandibles of O. macedoniensis appears to be relatively high, seemingly greater than in Gorilla and high even in comparison to Pongo, but this again is possibly in part an artifact of a small sample size.

The earliest known crown-Testudo tortoise from the late Miocene (Vallesian, 9 Ma) of Greece.

We here report on fossil remains of the earliest known crown-Testudo, an extant clade of Mediterranean testudinid tortoises from the late Miocene (Vallesian, MN 10) from the hominoid locality Ravin de la Pluie (RPl) in Greece. The material studied is a small, nearly complete carapace with a clearly distinct hypo-xiphiplastral hinge. This supports the sensu stricto generic assignment. This new terrestrial testudinid specimen is characterized by a possible tectiform, narrow, elongated shell with a pentagonal pygal and a long, posteriorly elevated, lenticular and rounded dorsal epiplastral lip. These unique features differ from those of other known Mediterranean hinged forms and allow the erection of the new species Testudo hellenica sp. nov. This taxon is phylogenetically close to two Greek species, the extant T. marginata and the fossil T. marmorum (Turolian, around 7.3 Ma). This record provides evidence for the first appearance of the genus Testudo sensu stricto at a minimum age of 9 Ma.

First record of Theropithecus (Cercopithecidae) from the Republic of Djibouti.

We describe here several specimens of the genus Theropithecus from the southern shore of Lake Assal in the Republic of Djibouti; they are the first record of the genus from this country. We assign them to a derived stage of T. oswaldi. This identification has implications for the age of the informal 'Formation 1' from this area, which should probably be assigned to the Middle Pleistocene. In addition, the presence of T. oswaldi close to the Bab el Mandeb Strait strongly suggests that the species followed this route to India, rather than a more northern one.

A new three-dimensional geometric morphometrics analysis of the Ouranopithecus macedoniensis cranium (Late Miocene, Central Macedonia, Greece).

OBJECTIVES: This study aims to virtually reconstruct the deformed face (XIR-1) and maxilla (RPl-128) of the Late Miocene hominoid Ouranopithecus macedoniensis from Greece, through the application of mirror-imaging and segmentation. Additionally, analysis was conducted through 3D geometric morphometrics, utilizing a comparative sample of fossil hominoids, extant great apes (Gorilla, Pan, and Pongo) and humans, so as to explore shape variation and phenetic similarities between them. MATERIALS AND METHODS: High-resolution computed tomography was used to create digital representations of the XIR-1 and RPl-128 specimens. The virtual reconstruction of the XIR-1 cranium was achieved by mirror-imaging, while the RPl-128 maxilla was virtually segmented and reattached in a correct anatomical position. Anatomical landmarks were registered in three dimensions on a comparative sample of adult crania of extant great apes, humans and fossil hominoids. The data were processed with Procrustes superimposition and analyzed using multivariate statistics methods. RESULTS: Results show that Ouranopithecus macedoniensis falls within or close to the Gorilla convex hull in the principal component analyses, and it is closer to the mean Procrustes shape distance of primarily Gorilla. Both specimens, XIR-1 and RPl-128, are classified as Gorilla based on discriminant function analyses. DISCUSSION: The results of our geometric morphometrics analyses indicate that Ouranopithecus macedoniensis is morphologically more similar to Gorilla than to Homo, Pan, or Pongo, results that can contribute to the evaluation of existing hypotheses about its phylogenetic position.

New Material of the Hominoid Ouranopithecus macedoniensis from the Late Miocene of the Axios Valley (Macedonia, Greece) with Some Remarks on Its Sexual Dimorphism.

New hominoid teeth from the late Miocene locality Ravin de la Pluie (RPl) of the Axios Valley (Macedonia, Greece) are studied in this article. Their morphology, dimensions and proportions are similar to the hominoid Ouranopithecus macedoniensis, allowing their attribution to this taxon. The studied material provides some new morphological characters for the female P3 (small asymmetry, small mesiobuccal crown projection, paracone higher than protocone) and the lower canine (mesial groove: large in the male and small in the female, distobuccal fovea: large in the female and small in the male). The new material enriches the collection of O. macedoniensis. The estimated degree of sexual dimorphism of the RPl O. macedoniensis, calculated by the multivariate size dimorphism method, is compared with those of extant hominoids (Gorilla, Pan, Pongo) and of the late Miocene Lufengpithecus lufengensis from China, which is considered as more dimorphic than any living hominoid. The results suggest that Ouranopithecus multivariate size dimorphism for the premolar, molar and post-canine row is similar to those of Pongo and Lufengpithecus, slightly higher than that of Gorilla and clearly higher than that of Pan. Therefore, O. macedoniensis is apparently one of the most sexually dimorphic hominoids and the RPl assemblage is monospecific.

First discovery of postcranial bones of Ouranopithecus macedoniensis (Primates, Hominoidea) from the late Miocene of Macedonia (Greece).

Two well preserved phalanges, one proximal and one intermediate, are identified and described. They constitute the first postcrania ever described of Ouranopithecus macedoniensis (Primates, Hominoidea) from the late Miocene locality of Ravin de la Pluie (RPl), Macedonia (Greece). They are isolated specimens, and the only ones known for their genus. The hypotheses that these specimens derive either from the hand or from the foot were tested. Comparisons with living apes of known positional behaviour were made to assess the functional signal in these specimens. The proximal phalanx, either manual or pedal, closely matches the proximal phalanges of terrestrial quadrupedal primates or the bipedal primate Homo. With respect to the intermediate phalanx we show that it closely matches phalanges of quadrupedal terrestrial primates. The terrestriality of Ouranopithecus, here reconstructed from phalangeal remains, is in agreement with our previous results of dental studies (thick check teeth enamel and microwear pattern of incisors and molars), which indicate that it was a hard object feeder living near the ground.

Three-dimensional analysis of mandibular dental root morphology in hominoids.

Although often preserved in the fossil record, mandibular dental roots are rarely used for evolutionary studies. This study qualitatively and quantitatively characterizes the three-dimensional morphology of hominoid dental roots. The sample comprises extant apes as well as two fossil species, Khoratpithecus piriyai and Ouranopithecus macedoniensis. The morphological differences between extant genera are observed, quantified and tested for their potential in systematics. Dental roots are imaged using X-ray computerized tomography, conventional microtomography and synchrotron microtomography. Resulting data attest to the high association between taxonomy and tooth root morphology, both qualitatively and quantitatively. A cladistic analysis based on the dental root characters resulted in a tree topology congruent with the consensus phylogeny of hominoids, suggesting that tooth roots might provide useful information in reconstructing hominoid phylogeny. Finally, the evolution of the dental root morphology in apes is discussed.

New data on Mustelidae (Carnivora) from Southeast Asia: Siamogale thailandica, a peculiar otter-like mustelid from the late middle Miocene Mae Moh Basin, northern Thailand.

We report new dental remains of Mustelidae from the late middle Miocene of Mae Moh Basin, northern Thailand, improving the poor fossil record of the family in Southeast Asia. Siamogale thailandica is a poorly known mustelid, previously recorded from just a single tooth. Here we present over a hundred new specimens attributable to this species. S. thailandica shows a combination of primitive and convergent features of the dentition that makes its original subfamilial assignment to Lutrinae doubtful. Evidence from the dental morphology suggests that it belongs to a bunodont otter-like mustelid that evolved in convergence with "true" otters (Lutrinae) toward a semi-aquatic way of life. Autapomorphic features such as the height and the position of the m1 metaconid and the shape of the P4 lingual shelf make S. thailandica unique among Mustelidae. The morphology of this species is mostly similar to Mionictis species and Lartetictis dubia, reported in the Miocene of North America and Europe, respectively. These similarities could imply immigration events to Thailand in the early or middle Miocene. Alternately, the lineage leading to Siamogale might have deeper origins from an endemic early Miocene Southeast Asian mustelid.

The oldest African fox (Vulpes riffautae n. sp., Canidae, Carnivora) recovered in late Miocene deposits of the Djurab desert, Chad.

We report on the oldest fox (Canidae) ever found in Africa. It is dated to 7 Ma based on the degree of evolution of the whole fauna. It belongs to a new species. Its overall size and some morphological characteristics distinguish the Chadian specimen from all the other foxes. The presence of Vulpes and of the genus Eucyon in slightly younger African locality, as well as in southwestern Europe in the late Miocene, may indicate that canids migrated in Europe from Africa through a trans-Mediterranean route.

The earliest modern mongoose (Carnivora, Herpestidae) from Africa (late Miocene of Chad).

We report on the earliest modern mongooses of Africa, from the late Miocene (ca. 7 Ma) of the hominid locality TM 266, Toros-Menalla, Chad. The material is based on fragmentary dentitions of three individuals. The main diagnostic feature of the Chadian species is the great development of the shear in the carnassials, which distinguishes the Chadian specimens from all extant herpestids except Herpestes and Galerella. In comparison with most extinct and extant Herpestes, the species from Toros-Menalla differs by a markedly smaller size and, depending on the species, relatively more elongated carnassials, more transversely elongated M1 and more reduced p4. On the basis of a great morphological similarity and the absence of significant differences, we assign our material to Galerella sanguinea; the Chadian finding therefore represents the earliest appearance of an extant species of Herpestidae. This record ties the first appearance of the genus to a minimum age of ca. 7 Ma, which is consistent with the estimated divergence date of 11.4 Ma known from the literature for the species of Galerella.

The deciduous lower dentition of Ouranopithecus macedoniensis (Primates, Hominoidea) from the late Miocene deposits of Macedonia, Greece.

Two mandibular fragments with associated milk teeth assigned to the late Miocene hominoid primate Ouranopithecus macedoniensis are analyzed. The fossils, which belong to a single individual, were found in the Vallesian locality of "Ravin de la Pluie" of the Axios Valley (Macedonia, Greece). The material is described here and compared with extant and extinct hominoids, allowing assessment of the evolutionary trends in the deciduous lower dentition within the Hominoidea. Hylobatids represent the more primitive pattern. Gorilla is slightly more derived than hylobatids, but less derived than Pongo and Pan, the latter being the most derived. With relatively smaller deciduous canines and more molarized deciduous premolars, Ouranopithecus is more derived than both Pan and Gorilla. Among the fossil hominoids, Proconsul, representing the primitive condition, has a very simple dp(3)and a dp(4)that has a trigonid that is taller than the talonid and which lacks a hypoconulid. Griphopithecus is more derived than Proconsul in having a dp(4) with a lower trigonid, a hypoconulid, and a less oblique cristid obliqua. Australopithecus and Paranthropus possess a similar morphology to that of Homo, while Ardipithecus appears to be more primitive than the latter genera. Ouranopithecus has a more derived lower milk dentition than Proconsul and Griphopithecus, but less derived than Australopithecus and Paranthropus. The comparison of the lower milk dentition of Ouranopithecus confirms our previous conclusions suggesting that this fossil hominoid shares derived characters with Australopithecus and Homo.

An examination of dental development in Graecopithecus freybergi (=Ouranopithecus macedoniensis).

This study examined enamel thickness and dental development in Graecopithecus freybergi (=Ouranopithecus macedoniensis), a late Miocene hominoid from Greece. Comparative emphasis was placed on Proconsul, Afropithecus, Dryopithecus, Lufengpithecus, and Gigantopithecus, fossil apes that vary in enamel thickness and patterns of development. In addition, comparisons were made with Paranthropus to investigate reported similarities in enamel thickness. Several sections of a right lower third molar were generated, from which enamel thickness and aspects of the enamel and dentine microstructure were determined. Data from parallel sections shed light on the effects of section obliquity, which may influence determination of both enamel thickness and crown formation time. Graecopithecus has relatively thick enamel, greater than any fossil ape but less than Paranthropus, with which it does show similarity in prism path and Hunter-Schreger band morphology. Aspects of enamel microstructure, including the periodicity and daily secretion rate, are similar to most extant and fossil apes, especially Afropithecus. Total crown formation time was estimated to be 3.5 years, which is greater than published values for modern Homo, similar to Pan, and less than Gigantopithecus. Data on dentine secretion and extension rates suggest that coronal dentine formation was relatively slow, but comparative data are very limited. Graecopithecus shares a crown formation pattern with several thick-enamelled hominoids, in which cuspal enamel makes up a very large portion of crown area, is formed by a large cell cohort, and is formed in less than half of the total time of formation. In Paranthropus, this pattern appears to be even more extreme, which may result in thicker enamel formed in an even shorter time. Developmental similarities between Paranthropus and Graecopithecus are interpreted to be parallelisms due to similarities in the mechanical demands of their diets.

Teeth and paleoanthropology.

Teeth have a very significant place in paleoanthropology. Their number is one of the keys of the primate taxonomy and classification. They have been used for systematics, phylogeny, paleobiology, or paleoenvironment. Some examples are given on the use of dental formula, morphology, wear or microwear, and biogeochemistry in paleoanthopologic studies.

Enamel hypoplasia in a pliocene hominid from Chad.

Abel is the first Australopithecine known west of the East African Rift Valley. The fossil finds include a perisymphyseal fragment of an adult mandible with well-preserved crowns of the right I2-P4 and the left C-P4. Abel's dentition displays many enamel defects, which are described in detail for each tooth. Pitting affected every tooth, while larger, shallow depressions were observed on the canines alone. From two to four pit bands occurred on the different teeth, each resulting from a separate hypoplastic episode. In modern humans, a large number of causes, both environmental and genetic, have been suggested for such enamel defects. It seems probable that Abel's pathology was systemic. However, the occurrence of a number of bands and the variable intensity of the attacks make it difficult to say whether there was a single, repetitive cause or different etiologies. Possible causes discussed here include recurrent fevers and seasonal nutritional deficiencies.

Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad.

All six known specimens of the early hominid Sahelanthropus tchadensis come from Toros-Menalla site 266 (TM 266), a single locality in the Djurab Desert, northern Chad, central Africa. Here we present a preliminary analysis of the palaeontological and palaeoecological context of these finds. The rich fauna from TM 266 includes a significant aquatic component such as fish, crocodiles and amphibious mammals, alongside animals associated with gallery forest and savannah, such as primates, rodents, elephants, equids and bovids. The fauna suggests a biochronological age between 6 and 7 million years. Taken together with the sedimentological evidence, the fauna suggests that S. tchadensis lived close to a lake, but not far from a sandy desert, perhaps the oldest record of desert conditions in the Neogene of northern central Africa.

A new hominid from the Upper Miocene of Chad, Central Africa.

The search for the earliest fossil evidence of the human lineage has been concentrated in East Africa. Here we report the discovery of six hominid specimens from Chad, central Africa, 2,500 km from the East African Rift Valley. The fossils include a nearly complete cranium and fragmentary lower jaws. The associated fauna suggest the fossils are between 6 and 7 million years old. The fossils display a unique mosaic of primitive and derived characters, and constitute a new genus and species of hominid. The distance from the Rift Valley, and the great antiquity of the fossils, suggest that the earliest members of the hominid clade were more widely distributed than has been thought, and that the divergence between the human and chimpanzee lineages was earlier than indicated by most molecular studies.