The phylogenetic affinities of Otavipithecus namibiensis

The middle Miocene hominoid Otavipithecus namibiensis is the first and most complete fossil ape from sub-equatorial Africa and represents a significant addition to the taxonomically sparse African middle Miocene hominoid fossil record. The Otavipithecus hypodigm comprises the holotype mandible, which presents a unique mosaic of dental and gnathic characters, and several attributed cranial and postcranial elements which resemble the stem hominoid Proconsul. Contrary to initial hopes that this discovery would provide new insights into hominoid morphological diversity and phylogenetic relationships, a variety of conflicting phylogenetic hypotheses have been advanced suggesting ties to virtually every major large-bodied hominoid group (Conroy et al., 1992; Andrews, 1992 a; Conroy, 1994; Pickford et al., 1994; Begun, 1994 a). Cladistic analysis of a matrix of 22 qualitative and ten quantitative characters of the mandible and mandibular dentition found no support for a close phylogenetic relationship between Otavipithecus and either the African ape or great ape clades, or with any of the Eurasian fossil hominoids with which it has previously been compared. A close relationship between Otavipithecus and Kenyapithecus cannot be ruled out, but is deemed unlikely on the basis both of morphological comparisons and the absence of support within a cladistic framework. The present analysis indicates that Otavipithecus is most closely related to Afropithecus, as previously suggested by Andrews (1992 a) among others. Due to lack of statistical support for this result, a conservative interpretation, that these taxa represented related but divergent lineages of a late early Miocene hominoid radiation, is currently favored. Findings are consistent with the allocation of Otavipithecus to Andrews' (1992 a) tribe Afropithecini which represents the sister group to Kenyapithecus and the extant ape clade.     

Side steps: the erratic pattern of hominin postcranial change through time

The hominin fossil record reveals brain-size expansion, canine reduction, premolar metaconid development, and numerous other craniodental features that become more human-like through time. In general, the postcranial skeleton also gets more human-like through time, but in some respects it does not. This is particularly apparent in the overall morphology of one of the most frequently preserved elements, the distal humerus. Some of the earliest hominins display quite human-like morphologies, whereas later specimens are quite unusual among extant species of Hominoidea: when described metrically and subjected to multivariate discriminant analyses in the context of large samples of extant hominoid humeri, the shapes of the earliest hominin fossils are more human-like than many of the later specimens. The Mahalanobis distances between many of the 1.5-2Ma hominin humeri and Homo sapiens are remarkably large. Many of the less well-represented postcranial specimens do not follow a linear path through time of increasing hominization either. This is particularly noticeable in the fore-to-hind limb joint-size proportions, ulnar morphology, and pelvic architecture. The hominin postcranial fossil record reveals many side-steps: there appears to be no simple march toward our human bodies, but a pattern better explained as adaptations to proximate conditions and constrained by ontogeny and history.     

Postcranial functional morphology of Morotopithecus bishopi, with implications for the evolution of modern ape locomotion

The large-bodied hominoid from Moroto, Uganda has until recently been known only from proconsulid like craniodental remains and some vertebrae with modern ape like features. The discovery of two partial femora and the glenoid portion of a scapula demonstrates that the functional anatomy of Morotopithecus differed markedly from other early and middle Miocene hominoids. Previous studies have consistently associated the vertebral remains with a short, stiff back and with orthograde postures. Although the proximal femur more closely resembles the femora of monkeys than of apes and suggests a moderate degree of hip abduction, the distal femur resembles those of extant large bodied apes and suggests a varied loading regime and an arboreal repertoire that may have included substantial vertical climbing. The femoral shaft displays uniformly thick cortical bone, beyond the range of thickness seen in extant primates, and signifies higher axial loading than is typical of most extant primates. The glenoid fossa is broad and uniformly curved as in extant suspensory primates. Overall, Morotopithecus is reconstructed as an arboreal species that probably relied on forelimb-dominated, deliberate and vertical climbing, suspension and quadrupedalism. Morotopithecus thus marks the first appearance of certain aspects of the modern hominoid body plan by at least 20 Ma. If the suspensory and orthograde adaptations linking Morotopithecus to extant apes are synapomorphies, Morotopithecus may be the only well-documented African Miocene hominoid with a close relationship to living apes and humans.     

Morphology of Afropithecus turkanensis from Kenya

Forty-six specimens of a large Miocene hominoid, Afropithecus turkanensis, recently recovered from northern Kenya preserve many morphological details that are described. The specimens include cranial, mandibular, and postcranial parts. They are compared briefly with other Miocene hominoids. It is suggested that Afropithecus may have affinities with Heliopithecus, Kenyapithecus, and the large hominoid from Moroto and Napak, although it is noted that the comparative material is limited in the number of common anatomical parts preserved.     

Size, shape, and asymmetry in fossil hominins: the status of the LB1 cranium based on 3D morphometric analyses

The unique set of morphological characteristics of the Liang Bua hominins (Homo floresiensis) has been attributed to explanations as diverse as insular dwarfism and pathological microcephaly. This study examined the relationship between cranial size and shape across a range of hominin and African ape species to test whether or not cranial morphology of LB1 is consistent with the basic pattern of static allometry present in these various taxa. Correlations between size and 3D cranial shape were explored using principal components analysis in shape space and in Procrustes form space. Additionally, patterns of static allometry within both modern humans and Plio-Pleistocene hominins were used to simulate the expected cranial shapes of each group at the size of LB1. These hypothetical specimens were compared to LB1 both visually and statistically. Results of most analyses indicated that LB1 best fits predictions for a small specimen of fossil Homo but not for a small modern human. This was especially true for analyses of neurocranial landmarks. Results from the whole cranium were less clear about the specific affinities of LB1, but, importantly, demonstrated that aspects of facial morphology associated with smaller size converge on modern human morphology. This suggests that facial similarities between LB1 and anatomically modern humans may not be indicative of a close relationship. Landmark data collected from this study were also used to test the degree of cranial asymmetry in LB1. These comparisons indicated that the cranium is fairly asymmetrical, but within the range of asymmetry exhibited by modern humans and all extant African ape species. Compared to other fossil specimens, the degree of asymmetry in LB1 is moderate and readily explained by the taphonomic processes to which all fossils are subject. Taken together, these findings suggest that H. floresiensis was most likely the diminutive descendant of a species of archaic Homo, although the details of this evolutionary history remain obscure.     

Carnivora from the Plio-Pleistocene hominin site of Drimolen, Gauteng, South Africa

Drimolen is one of the newest and most productive hominin sites in South Africa, and is dated on faunal grounds between 2.0 Ma to 1.5 Ma. This paper provides the first overview of the Carnivora from Drimolen, updating the previously published preliminary faunal list, and describing all currently prepared craniodental and postcranial material. The Drimolen specimens are described in comparison with other modern and fossil South African carnivore material. The carnivores cover a range of taxa including hyaenids, felids, canids and herpestids. Most notable amongst these are the sabretooth Dinofelis aff. piveteaui craniodental and postcranial remains, which are described in detail, and a Chasmaporthetes nitidula cranium. The genus Chasmaporthetes is found at three other sites in the area - Sterkfontein, Swartkrans and Coopers D. There are two models for the geographic origin of Dinofelis piveteaui, in that it may have arisen in either eastern or southern Africa. These possibilities are discussed in the light of the new South African Dinofelis material, as the Drimolen material appears to represent a more primitive form with affinities with D. piveteaui. Fossil leopard material from Kromdraai B and Drimolen is also discussed, as the metapodia assigned to P. pardus from these two sites are very small, but lie within the variation of modern leopards. Such size differences in fossil postcrania may have implications for the niches that these animals may have occupied in the past.     

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.     

First discovery of colobine fossils from the early to middle Pleistocene of southern Taiwan

Here we report on two kinds of cercopithecid fossil monkeys (Cercopithecinae and Colobinae) from the early to middle Pleistocene sediments of the Chochen (=Tsochen) area (Tsailiao-chi or Shinhua Hill), southern Taiwan. The fossil specimens include the first fossil record of colobine monkeys from Taiwan, where only macaque monkeys now occur. All cercopithecine fossils were identified as Macaca cf. Macaca cyclopis, the extant Taiwan macaque, except for one extremely large isolated upper molar, which may belong to another macaque species. On the other hand, all colobine specimens fall within the size variation of extant and extinct Rhinopithecus, but its specific status cannot be determined because of the scantiness of the fossil material. In Taiwan, Rhinopithecus presumably became extinct in the late Pleistocene, probably owing to global cooling and vegetation change, whereas macaques, which are of almost the same body size as Rhinopithecus, survived as M. cyclopis to the present. The contrasting history of survival between the two kinds of monkeys may be due to ecological/behavioral differences between them or as a result of accidental events that occurred in the Pleistocene of Taiwan.     

Hominoid phalanges from the middle Miocene site of Paşalar, Turkey

Eleven proximal and ten intermediate partial or complete hominoid phalanges have been recovered from the middle Miocene site of Pa?alar in Turkey. Based on species representation at Pa?alar, it is likely that most or all of the phalanges belong to Griphopithecus alpani rather than Kenyapithecus kizili, but both species may be represented. All of the complete or nearly complete phalanges appear to be manual, so comparisons to extant and other fossil primate species were limited to manual phalanges. Comparisons were made to extant hominoid and cercopithecoid primate genera expressing a variety of positional repertoires and varying degrees of arboreality and terrestriality. The comparisons consisted of a series of bivariate indices derived from previous publications on Miocene catarrhine phalangeal morphology. The proximal phalanges have dorsally expanded proximal articular surfaces, which is characteristic of cercopithecoids and most other Miocene hominoids, and indicates that the predominant positional behaviors involved pronograde quadrupedalism. Among the extant primates, many of the proximal and intermediate phalangeal indices clearly distinguish more habitually terrestrial taxa from those that are predominantly arboreal, and especially from taxa that commonly engage in suspensory activities. For nearly every index, the values of the Pa?alar phalanges occupy an intermediate position-most similar to values for Pan and, to a lesser extent, Macaca-indicating a generalized morphology and probably the use of both arboreal and terrestrial substrates. At least some terrestrial activity is also compatible with reconstructions of the Pa?alar habitat. Most proximal and intermediate phalanges of other middle and late Miocene hominoids have similar index values to those of the Pa?alar specimens, revealing broadly similar manual phalangeal morphology among many Miocene hominoids.     

Enamel thickness,microstructure and development in Afropithecus turkanensis

Afropithecus turkanensis, a 17-17.5 million year old large-bodied hominoid from Kenya, has previously been reported to be the oldest known thick-enamelled Miocene ape. Most investigations of enamel thickness in Miocene apes have been limited to opportunistic or destructive studies of small samples. Recently, more comprehensive studies of enamel thickness and microstructure in Proconsul, Lufengpithecus, and Dryopithecus, as well as extant apes and fossil humans, have provided information on rates and patterns of dental development, including crown formation time, and have begun to provide a comparative context for interpretation of the evolution of these characters throughout the past 20 million years of hominoid evolution. In this study, enamel thickness and aspects of the enamel microstructure in two A. turkanensis second molars were quantified and provide insight into rates of enamel apposition, numbers of cells actively secreting enamel, and the time required to form regions of the crown. The average value for relative enamel thickness in the two molars is 21.4, which is a lower value than a previous analysis of this species, but which is still relatively thick compared to extant apes. This value is similar to those of several Miocene hominoids, a fossil hominid, and modern humans. Certain aspects of the enamel microstructure are similar to Proconsul nyanzae, Dryopithecus laietanus, Lufengpithecus lufengensis, Graecopithecus freybergi and Pongo pygmaeus, while other features differ from extant and fossil hominoids. Crown formation times for the two teeth are 2.4-2.6 years and 2.9-3.1 years respectively. These times are similar to a number of extant and fossil hominoids, some of which appear to show additional developmental similarities, including thick enamel. Although thick enamel may be formed through several developmental pathways, most Miocene hominoids and fossil hominids with relatively thick enamel are characterized by a relatively long period of cuspal enamel formation and a rapid rate of enamel secretion throughout the whole cusp, but a shorter total crown formation time than thinner-enamelled extant apes.     

Craniomandibular morphology supporting the diphyletic origin of mangabeys and a new genus of the Cercocebus/Mandrillus clade, Procercocebus

Previous studies have noted skeletal and dental differences supporting the diphyletic origin of the mangabeys. Documented postcranial and dental characters are congruent with molecular data and thus support a close relationship between Cercocebus and Mandrillus (mandrills and drills) on the one hand and Lophocebus, Papio (baboons), and Theropithecus (geladas) on the other. Most of these characters, however, are postcranial and difficult to assess in the papionin fossil record because associated material is rare. In order to assess the African papionin fossil record and determine the evolutionary history of this group, cranial characters are critical. Here, a set of craniomandibular morphologies are documented that support the diphyletic origin of the mangabeys and more broadly support the molecular African papionin clades (i.e., Cercocebus/Mandrillus vs. Lophocebus/Papio/Theropithecus). These characters are then used to identify a series of fossil crania from Taung as representative of a new member of the Cercocebus/Mandrillus clade, Procercocebus antiquus. Procercocebus antiquus is closest in morphology to the extant taxon Cercocebus torquatus, and a probable ancestor-descendant relationship between Procercocebus and Cercocebus is suggested. Paleoecological reconstructions also suggest that a predator-prey relationship between African crowned eagles and the Procercocebus-Cercocebus lineage has existed for approximately the last two million years. Implications for Cercocebus biogeography and evolution are discussed.     

The hominoid proximal radius: re-interpreting locomotor behaviors in early hominins

Studies of fossil hominins are traditionally taxonomically narrow and often exclude comparisons with hylobatids. Hence, results of functional analyses of postcrania, interpreted as indicating that early hominins are "African-ape-like" in their postcranial skeletons and positional behaviors, may reflect an artifact of inadequate taxonomic and morphological breadth of the comparative sample. To address this problem and better understand early hominin positional behaviors, this study included hylobatids in a comparative analysis, focusing on the hominoid elbow joint. Specifically, morphometric variables of the proximal radius were derived from measurements from a sample of all genera of extant hominoids and casts of extinct hominin species. Univariate and multivariate analyses were performed on these data. Results show that early hominins are morphologically diverse and are not, as a group, similar to any one extant group. Instead, the fossils resemble Pan, Gorilla, and Hylobates, and are not like modern Homo sapiens or Pongo. This suggests that the morphology of Hylobates may reflect a morphotype for all later hominoids, thus complicating the functional interpretations of fossil hominins. The implications of these results are that the proximal radius is not a sensitive indicator of locomotor behavior among hominoids since the morphology in hylobatids and Gorilla and Pan is similar despite widely varying positional repertoires. Furthermore, inferences of function from form in extinct hominins can be drastically affected by the comparative outgroup selection. A re-evaluation of the functional morphology of the proximal radius in early hominins is addressed.     

A closer look at the “Protopithecus” fossil assemblages: new genus and species from Bahia,Brazil

The recently extinct large-bodied New World monkey Protopithecus brasiliensis Lund 1836 was named based on a distal humerus and proximal femur found in the Lagoa Santa cave system in the southeastern Brazilian state of Minas Gerais. These bones are from an animal about twice the size of the largest extant platyrrhines. One hundred and seventy-five years later, a nearly complete skeleton was discovered in the Toca da Boa Vista caves in the neighboring state of Bahia and was allocated to the same taxon as it was the first platyrrhine fossil of comparable size found since the originals. Our detailed study of the equivalent elements, however, reveals important morphological differences that do not correspond to intraspecific variation as we know it in related platyrrhine taxa. The presence of both an expanded brachioradialis flange on the humerus and gluteal tuberosity on the femur of the Bahian skeleton distinguishes it from the Lagoa Santa fossil as well as from all other platyrrhines. Further cranial and postcranial evidence suggests a closer relationship of the former with the alouattine Alouatta, while the limited Lund material fits more comfortably with the ateline clade. Therefore, we propose to limit P. brasiliensis Lund to the distal humerus and proximal femur from Lagoa Santa and erect a new genus and species for the skeleton from Toca da Boa Vista. Cartelles coimbrafilhoi was a large-bodied frugivore with a relatively small brain and diverse locomotor repertoire including both suspension and climbing that expands the range of platyrrhine biodiversity beyond the dimensions of the living neotropical primates.     

Early Miocene catarrhine dietary behaviour: the influence of the Red Queen Effect on incisor shape and curvature

The early Miocene catarrhine fossil record of East Africa represents a diverse and extensive adaptive radiation. It is well accepted that these taxa encompass a dietary range similar to extant hominoids, in addition to some potentially novel dietary behaviour. There have been numerous attempts to infer diet for these taxa from patterns of dental allometry and incisor and molar microwear, however, morphometric analyses until now have been restricted to the post-canine dentition. It has already been demonstrated that given the key functional role of the incisors in pre-processing food items prior to mastication, there is a positive correlation between diet and incisal curvature (Deane, A.S., Kremer, E.P., Begun, D.R., 2005. A new approach to quantifying anatomical curvatures using High Resolution Polynomial Curve Fitting (HR-PCF). Am. J. Phys. Anthropol. 128(3), 630-638.; Deane, A.S., 2007. Inferring dietary behaviour for Miocene hominoids: A high-resolution morphometric approach to incisal crown curvature. Ph.D. Dissertation. The University of Toronto.). This study seeks to re-examine existing dietary hypotheses for large-bodied early Miocene fossil catarrhines by contrasting the incisal curvature for these taxa with comparative models derived from prior studies of the correlation between extant hominoid incisor curvature and feeding behaviour. Incisor curvature was quantified for 78 fossil incisors representing seven genera, and the results confirm that early Miocene fossil catarrhines represent a dietary continuum ranging from more folivorous (i.e., Rangwapithecus) to more frugivorous (i.e., Proconsul) diets, as well as novel dietary behaviours that are potentially similar to extant ceboids (i.e., Afropithecus). Additionally, early Miocene fossil catarrhine incisors are less curved than extant hominoid incisors, indicating a general pattern of increasing mesio-distal and labial curvature through time. This pattern of morphological shifting is consistent with the Red Queen Effect (Van Valen, L., 1973. A new evolutionary law. Evol. Theory 1, 1-30), which predicts that taxa that are removed from one another by geological time, although potentially having similar diets, may exhibit differing degrees of a similar dietary adaptation (i.e., differing degrees of incisal curvature).     

Similarities in Aegyptopithecus and Afropithecus facial morphology

Recently discovered cranial fossils from the Oligocene deposits of the Fayum depression in Egypt provide many details of the facial morphology of Aegyptopithecus zeuxis. Similar features are found in the Miocene hominoid Afropithecus turkanensis. Their presence is the first good evidence of a strong phenetic link between the Oligocene and Miocene hominoids of Africa. A comparison of trait lists emphasizes the similarities of the two fossil species, and leads us to conclude that the two fossil genera share many primitive facial features. In addition, we studied facial morphology using finite-element scaling analysis and found that the two genera show similarities in morphological integration, or the way in which biological landmarks relate to one another in three dimensions to define the form of the organism. Size differences between the two genera are much greater than the relatively minor shape differences. Analysis of variability in landmark location among the four Aegyptopithecus specimens indicates that variability within the sample is not different from that found within two samples of modern macaques. We propose that the shape differences found among the four Aegyptopithecus specimens simply reflect individual variation in facial characteristics, and that the similarities in facial morphology between Aegyptopithecus and Afropithecus probably represent a complex of primitive facial features retained over millions of years.     

Plio-Pleistocene cercopithecids from Kanam East, western Kenya

This paper describes cercopithecid craniodental and postcranial fossils recovered by L. S. B. Leakey at Kanam East, Kenya during the early 1930s. These fossil monkeys have been generally assumed to have been derived from early Pliocene horizons, but their exact geographical and stratigraphical provenience is unknown. Although the question of the evolutionary significance of these specimens must await the recovery of more securely dated material from Kanam East, some general conclusions can be drawn concerning their taxonomic affinities and paleobiology. Based on comparative studies of the craniodental material, at least three extant genera are represented—Colobus,Lophocebus, andCercopithecus. The postcranial fossils include a number of hindlimb specimens, as well as the manubrium of a sternum and a caudal vertebra. Identification of the postcranial remains to particular genera is not possible, but they are similar in morphology to modern arboreal and semiterrestrial cercopithecid monkeys of small to medium size. It is evident that Kanam East had a diverse cercopithecid community, similar to those found today in forested and woodland habitats, and this may be of some significance in reconstructing the paleoecology of the site. Because the fossil record of most extant cercopithecid genera is rather sparse at Plio-Pleistocene sites in Africa, Kanam East represents one of only a few sites that has yielded material that can be assigned toColobus,Lophocebus, orCercopithecus. The fossil monkeys from the site, therefore, provide additional evidence to help reconstruct the paleobiology, as well as the patterns of species diversity and community structure that characterized the cercopithecid radiation during the Plio-Pleistocene.