Equatorius: a new hominoid genus from the Middle Miocene of Kenya

Ulnar morphology of Pliobates cataloniae (Pliopithecoidea: Crouzeliidae): Insights into catarrhine locomotor diversity and forelimb evolution

Pliobates cataloniae is a small-bodied crouzeliid pliopithecoid from the Miocene (∼11.6 Ma) of Abocador de Can Mata (ACM; Vallès-Penedès Basin, NE Iberian Peninsula). It exhibits a mosaic of primitive (stem catarrhine) and derived (modern hominoid-like) postcranial features. The holotype partial skeleton, from locality ACM/C8-A4, includes an almost complete ulna-a bone that plays a critical role in forearm flexion-extension and pronation-supination. Here, we use landmark-based three-dimensional geometric morphometrics to evaluate the closest morphometric affinities of the Pliobates ulna and explore its implications for the locomotor repertoire of this taxon. The comparative sample includes 156 specimens corresponding to 35 species from 20 anthropoid genera, three lorisid genera, and 10 fossil catarrhines. Our results indicate that the trochlear notch morphology of Pliobates resembles that of stem catarrhines and other nonhominoid primates. However, Pliobates differs from cercopithecoids (especially terrestrial taxa) in radial notch features related to enhanced pronation-supination capabilities, closely resembling the condition displayed by crown hominoids, Ateles, and Loris. In turn, the distal ulna of Pliobates does not overlap with any extant group and differs from the other fossils analyzed, most closely resembling that of hylobatids and lorisids. Pliobates probably had an extensive range of movement in the distal forearm, as indicated by the incipiently expanded semilunar ulnar head, the relatively short styloid process, the deep fovea, and the hooklike styloid process. This suggests that Pliobates would have frequently displayed nonstereotypical limb postures and slow locomotor behaviors. Overall, the ulnar morphology of Pliobates suggests that its locomotor repertoire may have combined cautious above-branch quadrupedalism and eclectic climbing with nonagile suspensory behaviors resembling those of Ateles.

Morphology of the Upper Post Canine Complex of Pleistocene Ponginae From Vietnam-Anatomical Variability and Systematics

OBJECTIVES

To examine the morphological variability of the isolated upper post-canine teeth currently allocated to Pongo and Langsonia from northern Vietnam. To revise the taxonomy and assess the systematics of the Middle and Late Pleistocene Ponginae based on the morphological and metric variation and the identification of derived features within samples.

MATERIALS AND METHODS

A series of correspondent analyses were generated against a large database of morphological (phenetic) characters scored for each tooth. Before analysis, the data was converted into a binary format. This frequently resulted in around 130 character states (variables) being analyzed.

RESULTS

We demonstrate that in terms of morphological and metric variation, the Middle and Late Pleistocene Ponginae samples frequently fall well outside the range observed in extant Pongo pygmaeus, but also the combined range seen in Pan paniscus and P. troglodytes. Many derived features were identified among the fossil samples. We recognize three species of Langsonia from Thẩm Khuyên Cave, one being the original species named by Schwartz and colleagues, while the other two were previously considered to belong to a species and subspecies of Pongo. We recognize two new species of Pongo from the Late Pleistocene of Làng Tráng and Kéo Lèng caves.

DISCUSSION

We conclude that the diversity of Ponginae inhabiting this part of mainland Southeast Asia during the Middle to Late Pleistocene is part of a monophyletic Pongo clade to the exclusion of Langsonia, which we consider a primitive member of the Ponginae.

A New Look at an Old Face: The Hoà Binh Late Pleistocene Pongo Skull and Other Faciodental Fragments From Breccia Caves in Vietnam-A Morphometric Assessment With Taxonomic Implications

OBJECTIVES

The taxonomic status of the Middle and Late Pleistocene pongines from northern Vietnam remains obscure. Two current schemes dominate. The first has multiple species of Pongo and Langsonia occupying the region during the late Middle and Late Pleistocene. The second has just two species, with the large species P. weidenreichi from the Early to Late Pleistocene of China evolving into the smaller P. devosi from the Middle/Late Pleistocene transition. Here, we generate several multivariate analyses against the available faciodental specimens from present-day northern Vietnam to test these two schemes and assess the morphotypes of these specimens.

MATERIALS AND METHODS

Discriminant factor and principal components analyses were both used against 51 extant hominids (Pongo, Gorilla and the two species of Pan) with 105 faciodental variables to examine the near-complete subfossil Hoà Binh skull. Additional fossils from the Late Pleistocene of this region were also analyzed. All specimens used were original.

RESULTS

We conclude that there was a diverse range of Pongo species in the region of northern Vietnam. We recognize two large and two small species during the Late Pleistocene. One of the larger species occupied this region toward the end of the Late Pleistocene, thus refuting the chronospecies hypothesis.

DISCUSSION

This study suggests the extinction of mainland Pongo species is associated with the rapid decline in habitat during the Late Pleistocene. Orangutan populations further south in Sumatra and Borneo (still then part of Mainland Asia) survived in safe havens of relic rainforests.

Manubriosternal Morphology of Anthropoid Primates

OBJECTIVES

The purpose of this paper is to examine the proportions of the manubrium and sternebrae across anthropoid primates to explore variation hypothesized to be related to thoracic shape and locomotor specialization, and to determine whether the sternoclavicular joint orientation in hominoids reflects hypothesized differences in shoulder joint positioning relative to the thorax.

MATERIALS AND METHODS

Metric data and sternoclavicular joint orientation data were collected from calibrated photographs of manubria and sternebrae from a large sample (n = 244) of extant anthropoid primates, as well as a small sample of fossil taxa. Manubriosternal and rib cage metric data were also collected from CT scans of an additional 52 extant anthropoid torsos. The data were analyzed using descriptive statistics, regression analyses, and linear correlations.

RESULTS

Manubriosternal morphology varies among anthropoids and appears to track thoracic shape and positional repertoire. Hominoids tend to have broader manubria and sterna than monkeys. Ekembo and Equatorius appear to most closely resemble colobines and Alouatta in sternebral shape, suggesting a thorax most similar to these taxa. Neandertals and early anatomically modern humans are most similar to humans, providing no evidence for a relatively broad rib cage. Sternoclavicular joint orientation also differs among hominoids, with all hominoids having more cranially inclined joint surfaces than humans. The human-like value observed for Australopithecus sediba supports the hypothesis that the clavicle in this species was not inclined laterally in resting posture.

CONCLUSIONS

Given the correlation between manubriosternal breadths and thoracic form across anthropoids, this study suggests that manubriosterna may provide useful information for interpreting skeletal form and positional repertoires in fossil anthropoids.

An ape partial postcranial skeleton (KNM-NP 64631) from the Middle Miocene of Napudet, northern Kenya

An ape partial postcranial skeleton (KNM-NP 64631) was recovered during the 2015-2021 field seasons at Napudet, a Middle Miocene (∼13 Ma) locality in northern Kenya. Bony elements representing the shoulder, elbow, hip, and ankle joints, thoracic and lumbar vertebral column, and hands and feet, offer valuable new information about the body plan and positional behaviors of Middle Miocene apes. Body mass estimates from femoral head dimensions suggest that the KNM-NP 64631 individual was smaller-bodied (c. 13-17 kg) than some Miocene taxa from eastern Africa, including Ekembo nyanzae, and probably Equatorius africanus or Kenyapithecus wickeri, and was more comparable to smaller-bodied male Nacholapithecus kerioi individuals. Similar to many Miocene apes, the KNM-NP 64631 individual had hip and hallucal tarsometatarsal joints reflecting habitual hindlimb loading in a variety of postures, a distal tibia with a large medial malleolus, an inflated humeral capitulum, probably a long lumbar spine, and a long pollical proximal phalanx relative to femoral head dimensions. The KNM-NP 64631 individual departs from most Early Miocene apes in its possession of a more steeply beveled radial head and deeper humeral zona conoidea, reflecting enhanced supinating-pronating abilities at the humeroradial joint. The KNM-NP 64631 individual also differs from Early Miocene Ekembo heseloni in having a larger elbow joint (inferred from radial head size) relative to the mediolateral width of the lumbar vertebral bodies and a more asymmetrical talar trochlea, and in these ways recalls inferred joint proportions for, and talocrural morphology of, N. kerioi. Compared to most Early Miocene apes, the KNM-NP 64631 individual likely relied on more forelimb-dominated arboreal behaviors, perhaps including vertical climbing (e.g., extended elbow, hoisting). Moreover, the Napudet ape partial postcranial skeleton suggests that an arboreally adapted body plan characterized by relatively large (here, based on joint size) forelimbs, but lacking orthograde suspensory adaptations, may not have been 'unusual' among Middle Miocene apes.

Body mass estimates from postcranial skeletons and implication for positional behavior in Nacholapithecus kerioi: Evolutionary scenarios of modern apes

This study reported the body mass (BM) estimates of the Middle Miocene fossil hominoid Nacholapithecus kerioi from Africa. The average BM estimates from all forelimb and hindlimb skeletal elements was 22.7 kg, which is slightly higher than the previously reported estimate of ~22 kg. This study revealed that Nacholapithecus has a unique body proportion with an enlarged forelimb relative to a smaller hindlimb, suggesting an antipronograde posture/locomotion, which may be related to the long clavicle, robust ribs, and some hominoid-like vertebral morphology. Because the BM of Nacholapithecus in this study was estimated to be below 30 kg, Nacholapithecus probably did not have relatively shorter and robust femora, which may result from other mechanical constraints, as seen in extant African hominoids. The BM estimate of Nacholapithecus suggests that full substantial modifications of the trunk and forelimb anatomy for risk avoidance and foraging efficiency, as seen in extant great apes, would not be expected in Nacholapithecus. Because larger monkeys are less arboreal (e.g., Mandrillus sphinx or Papio spp.), and the maximum BM among extant constant arboreal cercopithecoids is ~24 kg (male Nasalis larvatus), Nacholapithecus would be a constant arboreal primate. Although caution should be applied because of targeting only males in this study, arboreal quadrupedalism with upright posture and occasional antipronograde locomotion (e.g., climbing, chambering, descending, arm-swing, and sway) using the powerful grasping capacity of the hand and foot may be assumed for positional behavior of Nacholapithecus.

Systematics of Miocene apes: State of the art of a neverending controversy

Hominoids diverged from cercopithecoids during the Oligocene in Afro-Arabia, initially radiating in that continent and subsequently dispersing into Eurasia. From the Late Miocene onward, the geographic range of hominoids progressively shrank, except for hominins, which dispersed out of Africa during the Pleistocene. Although the overall picture of hominoid evolution is clear based on available fossil evidence, many uncertainties persist regarding the phylogeny and paleobiogeography of Miocene apes (nonhominin hominoids), owing to their sparse record, pervasive homoplasy, and the decimated current diversity of this group. We review Miocene ape systematics and evolution by focusing on the most parsimonious cladograms published during the last decade. First, we provide a historical account of the progress made in Miocene ape phylogeny and paleobiogeography, report an updated classification of Miocene apes, and provide a list of Miocene ape species-locality occurrences together with an analysis of their paleobiodiversity dynamics. Second, we discuss various critical issues of Miocene ape phylogeny and paleobiogeography (hylobatid and crown hominid origins, plus the relationships of Oreopithecus) in the light of the highly divergent results obtained from cladistic analyses of craniodental and postcranial characters separately. We conclude that cladistic efforts to disentangle Miocene ape phylogeny are potentially biased by a long-branch attraction problem caused by the numerous postcranial similarities shared between hylobatids and hominids-despite the increasingly held view that they are likely homoplastic to a large extent, as illustrated by Sivapithecus and Pierolapithecus-and further aggravated by abundant missing data owing to incomplete preservation. Finally, we argue that-besides the recovery of additional fossils, the retrieval of paleoproteomic data, and a better integration between cladistics and geometric morphometrics-Miocene ape phylogenetics should take advantage of total-evidence (tip-dating) Bayesian methods of phylogenetic inference combining morphologic, molecular, and chronostratigraphic data. This would hopefully help ascertain whether hylobatid divergence was more basal than currently supported.

Portable x-ray fluorescence spectroscopy geochemical sourcing of Miocene primate fossils from Kenya

Understanding the biogeography and evolution of Miocene catarrhines relies on accurate specimen provenience. It has long been speculated that some catarrhine specimens among the early collections from Miocene sites in Kenya have incorrect provenience data. The provenience of one of these, the holotype of Equatorius africanus (NHM M16649), was previously revised based on x-ray fluorescence spectroscopy. Here we use nondestructive portable x-ray fluorescence spectroscopy to test the provenience of additional catarrhine specimens that, based hat two specimens purportedly from the Early Miocene site of Rusinga (KNM-RU 1681 and KNM-RU 1999) are instead from Maboko, three specimens purportedly from the Middle Miocene site of Fort Ternan (KNM-FT 8, KNM-FT 41, and KNM-FT 3318) are instead from Songhor, and one specimen accessioned as being from Songhor (KNM-SO 5352) is from that site. Elemental data reveal that two of the specimens (KNM-FT 3318 and KNM-RU 1681) are likely to have been collected at sites other than their museum-accessioned provenience, while two others (KNM-RU 1999, and KNM-FT 41) were confirmed to have correct provenience. Results for both KNM-FT 8 and KNM-SO 5352, while somewhat equivocal, are best interpreted as supporting their accessioned provenience. Our results have implications for the distribution of certain catarrhine species during the Miocene in Kenya. Confirmation of the provenience of the specimens also facilitates taxonomic attribution, and resulted in additions to the morphological characterizations of some species. The protocol presented here has potential for wider application to assessing questions of provenience for fossils from other locations and periods.

Morphological affinities of a fossil ulna (KNM-WS 65401) from Buluk, Kenya

The morphological affinities of a primate proximal ulna (KNM-WS 65401) recovered from the late Early Miocene site Buluk, Kenya, are appraised. Nineteen three-dimensional landmarks on ulnae from 36 extant anthropoid species (n = 152 individuals) and KNM-WS 65401, as well as a subset of 14 landmarks on six ulnae belonging to other East African Miocene catarrhine taxa, were collected. To quantify ulnar shape, three-dimensional geometric morphometric techniques were used and linear dimensions commonly cited in the literature were derived from the landmark data. KNM-WS 65401 is situated between monkeys and hominoids in the principal components morphospace. KNM-WS 65401 shares features such as a short olecranon process, broad trochlear notch, and laterally oriented radial notch with extant hominoids, whereas features such as an anteriorly directed trochlear notch and flat, proximodistally elongated, and anteroposteriorly narrow radial notch are shared with extant monkeys. Principal component scores and linear metrics generally align KNM-WS 65401 with both suspensors and arboreal quadrupeds, but quadratic and linear discriminant analyses of principal component score data provide posterior probabilities of 80% and 83%, respectively, for assignment of KNM-WS 65401 to the suspensory group. Compared with fossil ulnae from other Miocene primates, KNM-WS 65401 is morphologically most distinct from KNM-LG 6, attributed to Dendropithecus macinnesi, and morphologically most similar to KNM-WK 16950R, attributed to Turkanapithecus kalakolensis. The KNM-WS 65401 individual likely possessed more enhanced capabilities for elbow joint extension, perhaps during suspensory behaviors, compared with other Miocene primates in the sample.

A proximal radius of Barberapithecus huerzeleri from Castell de Barberà: Implications for locomotor diversity among pliopithecoids

Pliopithecoids are a diverse group of Miocene catarrhine primates from Eurasia. Their positional behavior is still unknown, and many species are known exclusively from dentognathic remains. Here, we describe a proximal radius (IPS66267) from the late Miocene of Castell de Barberà (Vallès-Penedès Basin, NE Iberian Peninsula) that represents the first postcranial specimen of the pliopithecoid Barberapithecus huerzeleri. A body mass estimate based on the radius is compared with dental estimates, and its morphology is compared with that of extant and fossil anthropoids by qualitative means as well as by landmark-based three-dimensional geometric morphometrics. The estimated body mass of ∼5 kg for IPS66267 closely matches the dental estimates for the (female) holotype, thereby discounting an alternative attribution to the large-bodied hominoid recorded at Castell de Barberà. In multiple features (oval and moderately tilted head with a pronounced lateral lip and a restricted articular area for the capitulum; proximodistally expanded proximal radioulnar joint; and short, robust, and anteroposteriorly compressed neck), the specimen differs from hominoids and resembles instead extant nonateline monkeys and stem catarrhines. The results of the morphometric analysis further indicate that the Barberapithecus proximal radius shows closer similarities with nonsuspensory arboreal cercopithecoids and the dendropithecid Simiolus. From a locomotor viewpoint, the radius of Barberapithecus lacks most of the features functionally related to climbing and/or suspensory behaviors and displays instead a proximal radioulnar joint that would have been particularly stable under pronation. On the other hand, the Barberapithecus radius differs from other stem catarrhines in the less anteroposteriorly compressed and less tilted radial head with a deeper capitular fovea, suggesting a somewhat enhanced mobility at the elbow joint. We conclude that pronograde arboreal quadrupedalism was the main component of the locomotor repertoire of Barberapithecus but that, similar to other crouzeliids, it might have displayed better climbing abilities than pliopithecids.

Wrist morphology reveals substantial locomotor diversity among early catarrhines: an analysis of capitates from the early Miocene of Tinderet (Kenya)

Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old World monkeys, and their extinct relatives). However, locomotor diversity within this group has eluded characterization, bolstering a narrative that nearly all early catarrhines shared a primitive locomotor repertoire resembling that of the well-described arboreal quadruped Ekembo heseloni. Here we describe and analyse seven catarrhine capitates from the Tinderet Miocene sequence of Kenya, dated to ~20 Ma. 3D morphometrics derived from these specimens and a sample of extant and fossil capitates are subjected to a series of multivariate comparisons, with results suggesting a variety of locomotor repertoires were present in this early Miocene setting. One of the fossil specimens is uniquely derived among early and middle Miocene capitates, representing the earliest known instance of great ape-like wrist morphology and supporting the presence of a behaviourally advanced ape at Songhor. We suggest Rangwapithecus as this catarrhine’s identity, and posit expression of derived, ape-like features as a criterion for distinguishing this taxon from Proconsul africanus. We also introduce a procedure for quantitative estimation of locomotor diversity and find the Tinderet sample to equal or exceed large extant catarrhine groups in this metric, demonstrating greater functional diversity among early catarrhines than previously recognised.

Phenetic and functional analyses of the distal ulna of Australopithecus afarensis and Australopithecus africanus

The morphology of the distal portion of the hominoid ulna is poorly studied despite its important functional role at the wrist joint. There are five qualitatively well-described fossil hominin distal ulnae belonging to Australopithecus afarensis and Australopithecus africanus, but there have been few efforts to quantify their morphology or relate it to their functional abilities. This article presents an effort to do so, using three-dimensional geometric morphometrics to analyze the shape of the distal ulna of the Plio-Pleistocene hominins and an extant comparative sample of great apes and humans. For the extant taxa, results show that the morphology of Pan and Pongo is distinct from that of Homo, and that these differences are likely related to climbing, clambering and below-branch suspension in the former, and the release of the limbs from locomotion and (potentially) tool manufacture in the latter. For the australopiths, results indicate that the A. afarensis sample is relatively heterogeneous. These results are driven by the morphology of A.L. 333-12, which is the largest ulna in the sample and has a unique combination of traits when compared with the other two A. afarensis specimens. Overall, the morphology of all the hominins was most consistent with the pattern displayed by extant great apes, and specifically Pan and Pongo; however, large overlap in shape in the distal ulna in the extant sample indicates that other areas of the skeleton may be more informative for functional analyses.

The Middle Miocene ape Pierolapithecus catalaunicus exhibits extant great ape-like morphometric affinities on its patella: inferences on knee function and evolution

The mosaic nature of the Miocene ape postcranium hinders the reconstruction of the positional behavior and locomotion of these taxa based on isolated elements only. The fossil great ape Pierolapithecus catalaunicus (IPS 21350 skeleton; 11.9 Ma) exhibits a relatively wide and shallow thorax with moderate hand length and phalangeal curvature, dorsally-oriented metacarpophalangeal joints, and loss of ulnocarpal articulation. This evidence reveals enhanced orthograde postures without modern ape-like below-branch suspensory adaptations. Therefore, it has been proposed that natural selection enhanced vertical climbing (and not suspension per se) in Pierolapithecus catalaunicus. Although limb long bones are not available for this species, its patella (IPS 21350.37) can potentially provide insights into its knee function and thus on the complexity of its total morphological pattern. Here we provide a detailed description and morphometric analyses of IPS 21350.37, which are based on four external dimensions intended to capture the overall patellar shape. Our results reveal that the patella of Pierolapithecus is similar to that of extant great apes: proximodistally short, mediolaterally broad and anteroposteriorly thin. Previous biomechanical studies of the anthropoid knee based on the same measurements proposed that the modern great ape patella reflects a mobile knee joint while the long, narrow and thick patella of platyrrhine and especially cercopithecoid monkeys would increase the quadriceps moment arm in knee extension during walking, galloping, climbing and leaping. The patella of Pierolapithecus differs not only from that of monkeys and hylobatids, but also from that of basal hominoids (e.g., Proconsul and Nacholapithecus), which display slightly thinner patellae than extant great apes (the previously-inferred plesiomorphic hominoid condition). If patellar shape in Pierolapithecus is related to modern great ape-like knee function, our results suggest that increased knee mobility might have originally evolved in relation to enhanced climbing capabilities in great apes (such as specialized vertical climbing).

The nasal and paranasal architecture of the Middle Miocene ape Pierolapithecus catalaunicus (primates: Hominidae): phylogenetic implications

The internal (nasal and paranasal) cranial anatomy of the Middle Miocene (11.9 Ma [millions of years ago]) great ape Pierolapithecus catalaunicus (Hominidae: Dryopithecini) is described on the basis of computed-tomography scans of the holotype specimen (IPS21350), with particular emphasis on its phylogenetic implications. Pierolapithecus displays the following characters: an anteriorly-restricted maxillary sinus that posteriorly spreads towards the ethmoidal area (thus resembling the pongine condition), although being situated well above the molar roots (as in kenyapithecins, other dryopithecins and pongines); lack of frontal sinus (a synapomorphy of derived pongines, independently acquired by both cercopithecoids and hylobatids); posteriorly-situated turbinals (as in Pongo); anteriorly-projecting nasolacrimal canal (as in Pongo); and probably stepped nasal floor with non-overlapping premaxillary-maxillary contact (as in dryopithecines and stem hominoids, although it cannot be conclusively shown due to bone damage). Overall, Pierolapithecus displays a mosaic of primitive hominid and derived pongine features that are inconsistent with this taxon being a hominine (as previously suggested). Two alternative phylogenetic interpretations are possible: Pierolapithecus may be a stem member of the Hominidae as previously suggested in its original description, or alternatively this taxon may be a stem member of the Ponginae s.l. (with the European dryopithecines being the sister taxon to the Asian pongines).

European Miocene hominids and the origin of the African ape and human clade

In 1871, Darwin famously opined, "In each great region of the world the living mammals are closely related to the extinct species of the same region. It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere." Although this quote is frequently recalled today, Darwin's next line is rarely acknowledged: "But it is useless to speculate on this subject, for an ape nearly as large as a man, namely the Dryopithecus of Lartet, which was closely allied to the anthropomorphous Hylobates, existed in Europe during the Upper Miocene period; and since so remote a period the earth has certainly undergone many great revolutions, and there has been ample time for migration on the largest scale."

First hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar)

For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia.

Miocene Hominids and the Origins of the African Apes and Humans

In the past 20 years, new discoveries of fossil apes from the Miocene have transformed our ideas about the timing, geography, and causes of the evolution of the African apes and humans. Darwin predicted that the common ancestor of African apes and humans would be found in Africa. Yet the majority of fossil great apes are from Europe and Asia. I briefly review the fossil record of great apes and then examine the main competing hypotheses of our origins, African or European, inspired by these recent discoveries, concluding that elements of both ideas are likely to be correct. Given current interpretations of the paleobiology of fossil apes and relationships among living hominids, I suggest that the last common ancestor of chimpanzees and humans was morphologically unique, but more chimpanzee-like than hominin-like: a knuckle-walker with a chimpanzee-sized brain, canine sexual dimorphism, and many probable behavioral similarities to living chimpanzees.

A unique Middle Miocene European hominoid and the origins of the great ape and human clade

The great ape and human clade (Primates: Hominidae) currently includes orangutans, gorillas, chimpanzees, bonobos, and humans. When, where, and from which taxon hominids evolved are among the most exciting questions yet to be resolved. Within the Afropithecidae, the Kenyapithecinae (Kenyapithecini + Equatorini) have been proposed as the sister taxon of hominids, but thus far the fragmentary and scarce Middle Miocene fossil record has hampered testing this hypothesis. Here we describe a male partial face with mandible of a previously undescribed fossil hominid, Anoiapithecus brevirostris gen. et sp. nov., from the Middle Miocene (11.9 Ma) of Spain, which enables testing this hypothesis. Morphological and geometric morphometrics analyses of this material show a unique facial pattern for hominoids. This taxon combines autapomorphic features--such as a strongly reduced facial prognathism--with kenyapithecine (more specifically, kenyapithecin) and hominid synapomorphies. This combination supports a sister-group relationship between kenyapithecins (Griphopithecus + Kenyapithecus) and hominids. The presence of both groups in Eurasia during the Middle Miocene and the retention in kenyapithecins of a primitive hominoid postcranial body plan support a Eurasian origin of the Hominidae. Alternatively, the two extant hominid clades (Homininae and Ponginae) might have independently evolved in Africa and Eurasia from an ancestral, Middle Miocene stock, so that the supposed crown-hominid synapomorphies might be homoplastic.

The deciduous dentition of Griphopithecus alpani from Paşalar, Turkey

Seventy-four hominoid primary teeth have been recovered from the middle Miocene site of Paşalar, Turkey, constituting the largest sample of deciduous teeth for any species of fossil ape. Morphological features that characterize the permanent teeth of Griphopithecus alpani from the site have also been identified in some of these deciduous teeth, including a lingual pillar on the di(1)s. These features plus the overwhelming preponderance of G. alpani permanent teeth at the site suggest that all of the deciduous teeth belong to this species. Contrary to the situation in the permanent teeth, nothing in the morphology of the primary dentition suggests the representation of a second species. The age profile of the non-adult hominoids was reconstructed based on the degree and type of wear recorded on the dp4s, the most abundant deciduous tooth in the sample, assuming a similar eruption chronology to that of Pan troglodytes. This analysis indicates underrepresentation of very young individuals in the sample and high mortality for individuals belonging to the 3-5-years age cohort, a situation that could be due to the effects of stress related to weaning. The coefficient of variation and range-index values obtained for the majority of tooth types are equal to or greater than the comparable values in a sample of P. troglodytes, in some cases at much smaller sample sizes. One possible explanation for this is that there was greater sexual dimorphism in the G. alpani deciduous dentition than in Pan, which would mirror the condition of the permanent dentition.

Middle Miocene dispersals of apes

The earliest record of fossil apes outside Africa is in the latest early Miocene of Turkey and eastern Europe. There were at least 2, and perhaps 4, species of ape, which were found associated with subtropical mixed environments of forest and more open woodland. Postcranial morphology is similar to that of early Miocene primates and indicates mainly generalized arboreal quadrupedal behaviours similar to those of less specialized New World monkeys such as Cebus. Robust jaws and thick enamelled teeth indicate a hard fruit diet. The 2 best known species of fossil ape are known from the site of Paşalar in Turkey. They have almost identical molar and jaw morphology. Molar morphology is also similar to that of specimens from Germany and Slovakia, but there are significant differences in the anterior teeth of the 2 Paşalar species. The more common species, Griphopithecus alpani, shares mainly primitive characters with early and middle Miocene apes in Africa, and it is most similar phenetically to Equatorius africanus from Maboko Island and Kipsaramon. The second species is assigned to a new species of Kenyapithecus, an African genus from Fort Ternan in Kenya, on the basis of a number of shared derived characters of the anterior dentition, and it is considered likely that there is a phylogenetic link between them. The African sites all date from the middle Miocene, similar in age to the Turkish and European ones, and the earliest emigration of apes from Africa coincides with the closure of the Tethys Sea preceding the Langhian transgression. Environments indicated for the African sites are mixtures of seasonal woodlands with some forest vegetation. The postcrania of both African taxa again indicate generalized arboreal adaptation but lacking specialized arboreal function. This middle Miocene radiation of both African and non-African apes was preceded by a radiation of arboreal catarrhine primates in the early Miocene, among which were the earliest apes. The earliest Miocene apes in the genus Proconsul and Rangwapithecus were arboreal, and because of their association with the fruits of evergreen rain forest plants at Mfwangano Island, it would appear that they were forest adapted, i.e. were living in multi-storied evergreen forest. The same or similar species of the same genera from Rusinga Island, together with other genera such as Nyanzapithecus and the small ape Limnopithecus, were associated with plants and animals indicating seasonal woodland environments, probably with gallery forest forming corridors alongside rivers. While the stem ancestors of the Hominoidea were almost certainly forest adapted, the evidence of environments associated with apes in the later part of the early Miocene and the middle Miocene of East Africa indicates more seasonal woodlands, similar to those reconstructed for the middle Miocene of Paşalar in Turkey. This environmental shift was probably a requisite for the successful emigration of apes out of Africa and made possible later movement between the continents for much of the middle Miocene, including possible re-entry of at least one ape lineage back into Africa.

Lingual incisor traits in modern hominoids and an assessment of their utility for fossil hominoid taxonomy

The morphology of the anterior dentition has received scant attention for purposes of taxonomic discrimination. Recently, however, lingual incisor morphology was used in differentiating several Miocene ape species and genera. This paper assesses the utility of this morphology for taxonomic discrimination by examining the nature and patterns of variation in lingual incisor morphology in extensive samples of modern chimpanzees, gorillas, orangutans, and gibbons. This paper documents discrete morphological traits on the lingual side of incisors. Trait frequencies are used in univariate and multivariate analyses to examine the apportionment of variation in species, subspecies, and populations. A correlation between lingual incisor traits, tooth dimensions, and sex attempts to determine if such factors affect the manifestation of traits. Finally, the findings are applied to understanding patterns of variation in the Miocene hominids. The study demonstrates that: 1) lingual incisor morphology differs substantially between the hylobatids and great apes; 2) variation in incisor traits is high within species, and most of it is found within local populations; and 3) incisor traits do not correlate significantly with incisor dimensions or sex. Species and to some extent subspecies of extant hominoids can be differentiated statistically using lingual incisor traits, but the frequency of traits such as continuous or discontinuous cingulum, or the presence or absence of pillars, differentiates them. Given this pattern of variation, I argue that it is necessary to assume and document similar patterns of variation in Miocene apes before incisor morphology is used for differentiating taxa.

Anatomy of the nasal cavity and paranasal sinuses in Aegyptopithecus and early Miocene African catarrhines

Neontological comparisons suggest that paranasal sinus anatomy is diagnostic of several catarrhine clades such as Cercopithecoidea, Hominoidea, Homininae, and Ponginae. However, while the loss of sinuses in cercopithecoids is generally recognized as a derived condition, determining the polarity of character-state changes within noncercopithecoid catarrhines requires knowledge of the primitive catarrhine condition. To address this problem, the paranasal sinus anatomy of Aegyptopithecus and several early Miocene catarrhines was investigated. Two partial facial skeletons of Aegyptopithecus were subjected to computed tomography in order to reveal their internal anatomy. These data were compared with facial and palatal specimens of Proconsul, Limnopithecus, Dendropithecus, Rangwapithecus, and Kalepithecus in the National Museums of Kenya in Nairobi, and to wet and dry specimens of living taxa. Results confirm that cercopithecoid paranasal anatomy is derived, and reveal that the sinus anatomy of stem catarrhines included a hominoid-like maxillary sinus as well as an ethmofrontal system like that of hominines. Accordingly, these two features do not constitute evidence for the hominoid, hominid, or hominine status of any fossil species. Conversely, the absence of the ethmofrontal sinus system in Sivapithecus and Pongo is synapomorphic. In addition, features of the nasal cavity of Limnopithecus and Kalepithecus support previous suggestions that these taxa are stem catarrhines rather than hominoids.