Fossil Hominoids Research Articles

The Distribution and Biogenic Origins of Zinc in the Mineralised Tooth Tissues of Modern and Fossil Hominoids: Implications for Life History, Diet and Taphonomy.

Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel-dentine-junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197-1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.

Principal component and linear discriminant analyses for the classification of hominoid primate specimens based on bone shape data.

In this study, we tested the hypothesis that machine learning methods can accurately classify extant primates based on triquetrum shape data. We then used this classification tool to observe the affinities between extant primates and fossil hominoids. We assessed the discrimination accuracy for an unsupervised and supervised learning pipeline, i.e. with principal component analysis (PCA) and linear discriminant analysis (LDA) feature extraction, when tasked with the classification of extant primates. The trained algorithm is used to classify a sample of known fossil hominoids. For the visualization, PCA and uniform manifold approximation and projection (UMAP) are used. The results show that the discriminant function correctly classified the extant specimens with an F1-score of 0.90 for both PCA and LDA. In addition, the classification of fossil hominoids reflects taxonomy and locomotor behaviour reported in literature. This classification based on shape data using PCA and LDA is a powerful tool that can discriminate between the triquetrum shape of extant primates with high accuracy and quantitatively compare fossil and extant morphology. It can be used to support taxonomic differentiation and aid the further interpretation of fossil remains. Further testing is necessary by including other bones and more species and specimens per species extinct primates.

The evolution of hominoid locomotor versatility: Evidence from Moroto, a 21 Ma site in Uganda

Living hominoids are distinguished by upright torsos and versatile locomotion. It is hypothesized that these features evolved for feeding on fruit from terminal branches in forests. To investigate the evolutionary context of hominoid adaptive origins, we analyzed multiple paleoenvironmental proxies in conjunction with hominoid fossils from the Moroto II site in Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C4 grasses in Africa based on a confirmed age of 21 million years ago (Ma). We demonstrate that the leaf-eating hominoid Morotopithecus consumed water-stressed vegetation, and postcrania from the site indicate ape-like locomotor adaptations. These findings suggest that the origin of hominoid locomotor versatility is associated with foraging on leaves in heterogeneous, open woodlands rather than forests.

Additional hominoid fossils from the early Miocene of the Lothidok Formation, Kenya.

Hominoid fossils are abundant at early Miocene fossil sites in the Lothidok Range, located directly west of Lake Turkana in northern Kenya. The West Turkana Miocene Project (WTMP) has worked in the Lothidok Range since 2008 with the goal of further elucidating the paleobiology of the hominoids through the recovery of new specimens and detailed documentation of their paleoecological context. To date our research has focused largely on the Kalodirr and Moruorot Site Complexes, both radiometrically dated to ~17.5-16.8Ma. Our ongoing fieldwork at the Kalodirr Site Complex resulted in the discovery of new dentognathic specimens of the three previously identified species of fossil hominoids-Turkanapithecus kalakolensis, Simiolus enjiessi, and Afropithecus turkanensis. A new mandible and an isolated M3 of T. kalakolensis from Kalodirr further clarify the lower molar morphology of the species and permit identification of KNM-MO 1 as a mandible of T. kalakolensis. A new mandible of S. enjiessi provides evidence of the relative proportions of the first and second lower molars. A new male specimen of A. turkanensis shows unusual P4 morphology that may be a developmental anomaly or a previously unknown morphological variant. An improved understanding of the lower molar morphology of T. kalakolensis further strengthens its identification as a nyanzapithecine. Our new specimens and subsequent re-identification of existing collections makes it clear that all three Lothidok hominoids are known from both the Moruorot and Kalodirr Site Complexes. The Lothidok Range holds great promise for further documenting hominoid evolution.

A Knuckle‐Walking Signal in the Trabecular Architecture of the African Ape Scaphoid

African ape (Panand Gorilla) carpals have few diagnostic features in their external morphology reflecting knuckle‐walking hand postures, and whether the internal trabecular architecture of their carpals yields a functional signal for knuckle‐walking is unclear. Here we perform a high‐density, multiple‐VOI analysis of trabecular architecture in the scaphoid of knuckle‐walking African apes and non‐knuckle‐walkers (Pongo, Macaca,and Papio). We predict that (1) Gorilla, the taxon with largest body mass, will have the highest trabecular thickness (Tb.Th) and trabecular spacing (Tb.Sp) because Tb.Th and Tb.Sp have been shown to be correlated with body size, (2) bone volume fraction (BV/TV) will be higher in habitually terrestrial taxa than in arboreal taxa, as the forelimb is thought to experience relatively high compressive loads during terrestrial locomotion, (3) Pongo will have the lowest degree of anisotropy (DA) as they engage in variable locomotor behaviors, and (4) pattern of DA distribution will differ between knuckle‐walking and non‐knuckle‐walking taxa, as the consistency and direction of wrist joint loading likely differs among primates with different quadrupedal hand postures.Fifty‐four scaphoids were scanned using high‐resolution µCT (voxel range: 48‐27 μm). Surface models were created from image data and then subjected to a weighted spherical harmonic analysis. Volumes of interest (VOIs) were manually placed into a surface model of the average scaphoid, and then warped to individual specimens using the thin plate spline interpolation function. Trabecular properties were calculated using the BoneJ plugin for ImageJ and MATLAB, and variation in distribution of trabecular parameters among taxa was summarized using a principal component analysis (PCA). Parameter values among species were compared with non‐parametric MANOVAs using a randomized residual permutation procedure, and PC scores were compared using Kruskal‐Wallis ANOVAs. The parameter distribution within each bone was visualized by comparing species‐average color maps of average parameter values.As predicted, Tb.Th and Tb.Sp are greatest in Gorilla, indicating that these parameters are related in part to body size. In contrast, results indicate that BV/TV and DA magnitudes do not follow predictions. Specifically, habitually terrestrial taxa do not have significantly higher BV/TV than arboreal taxa, and taxa that engage in more variable locomotor behaviors (i.e., Pongo) do not have the lowest values of DA. Finally, results indicate that knuckle‐walking African apes can be distinguished from other taxa studied here by pattern of DA distribution, and these differences appear to reflect differences in habitual hand postures and locomotor modes. If this pattern is unique to knuckle‐walking apes among hominoids, and is also identified in the scaphoid of fossil hominoids, then it may be used to indicate whether fossil taxa were habitual knuckle‐walkers.

Phylogenetic analysis of Middle-Late Miocene apes

Despite intensive study, many aspects of the evolutionary history of great apes and humans (Hominidae) are not well understood. In particular, the phylogenetic relationships of many fossil taxa remain poorly resolved. This study aims to provide an updated hypothesis of phylogenetic relationships for Middle-Late Miocene fossil apes, focusing on those taxa typically considered to be great apes. The character matrix compiled here samples 274 characters from the skull, dentition, and postcranium. Multiple iterations were performed to examine the effects of ingroup taxon selection, outgroup constraints, treatment of continuous data, character partitions (craniodental, postcranial), and missing data. Parsimony and Bayesian methods were used to infer phylogenetic relationships. Most European hominoids (Hispanopithecus, Rudapithecus, Dryopithecus, Pierolapithecus) are recovered as stem hominids, not more closely related to orangutans or to African apes and humans (Homininae), whereas Ouranopithecus, Graecopithecus, and Nakalipithecus are inferred to be members of the hominine clade. Asian fossil hominoids, with the exception of Lufengpithecus hudienensis, are recovered as part of the orangutan clade (Ponginae). Results suggest that Kenyapithecus and Griphopithecus are possible stem hominids, whereas Equatorius and Nacholapithecus are consistently recovered as stem hominoids. Oreopithecus and Samburupithecus are not recovered as hominids. Results of Bayesian analyses differ from those of parsimony analyses. Craniodental and postcranial character partitions are incongruent in the placement of hylobatids, which is interpreted as evidence that hylobatids and hominids independently evolved adaptations to suspensory positional behaviors. An understanding of phylogenetic relationships is necessary to address many of the questions asked in paleoanthropology. Thus, the updated hypothesis of phylogenetic relationships presented here can be used to gain a better understanding of important morphological transitions that took place during hominid evolution, ancestral morphotypes at key nodes, and the biogeography of the clade.

Bipedal locomotion in zoo apes: Revisiting the hylobatian model for bipedal origins.

Bipedal locomotion is a hallmark of being human. Yet the body form from which bipedalism evolved remains unclear. Specifically, the positional behaviour (i.e. orthograde vs. pronograde) and the length of the lumbar spine (i.e. long and mobile vs. short and stiff) of the last common ancestor (LCA) of the African great apes and humans require further investigation. While fossil evidence would be the most conclusive, the paucity of hominid fossils from 5-10 million years ago makes this field of research challenging. In their absence, extant primate anatomy and behaviour may offer some insight into the ancestral body form from which bipedalism could most easily evolve. Here, we quantify the frequency of bipedalism in a large sample (N = 496) of zoo-housed hominoids and cercopithecines. Our results show that while each studied species of ape and monkey can move bipedally, hylobatids are significantly more bipedal and engage in bipedal locomotion more frequently and for greater distances than any other primate sampled. These data support hypotheses of an orthograde, long-backed and arboreal LCA, which is consistent with hominoid fossils from the middle-to-late Miocene. If true, knuckle-walking evolved in parallel in Pan and Gorilla, and the human body form, particularly the long lower back and orthograde posture, is conserved.

Evolutionary trends of the lateral foot in catarrhine primates: Contextualizing the fourth metatarsal of Australopithecus afarensis

In 2000, a complete fourth metatarsal (Mt4) of the ∼3- to 4-Million-year-old hominin Australopithecus afarensis was recovered in Hadar, Ethiopia. This metatarsal presented a mostly human-like morphology, suggesting that a rigid lateral foot may have evolved as early as ∼3.2 Ma. The lateral foot is integral in providing stability during the push off phase of gait and is key in understanding the transition to upright, striding bipedalism. Previous comparisons of this fossil were limited to Pan troglodytes, Gorilla gorilla, and modern humans. This study builds on previous studies by contextualizing the Mt4 morphology of A. afarensis (A.L. 333-160) within a diverse comparative sample of nonhuman hominoids (n = 144) and cercopithecids (n = 138) and incorporates other early hominins (n = 3) and fossil hominoids that precede the Pan-Homo split (n = 4) to better assess the polarity of changes in lateral foot morphology surrounding this divergence. We investigate seven morphological features argued to be functionally linked to human-like bipedalism. Our results show that some human-like characters used to assess midfoot and lateral foot stiffness in the hominin fossil record are present in our Miocene ape sample as well as in living cercopithecids. Furthermore, modern nonhuman hominoids can be generally distinguished from other species in most metrics. These results suggest that the possession of a rigid foot in hominins could represent a conserved trait, whereas the specialized pedal grasping mechanics of extant apes may be more derived, in which case some traits often used to infer bipedal locomotion in early hominins may, instead, reflect a lower reliance on pedal grasping. Another possibility is that early hominins reverted from modern ape Mt4 morphology into a more plesiomorphic condition when terrestrial bipedality became a dominant behavior. More fossils dating around the Pan-Homo divergence time are necessary to test these competing hypotheses.

Morphological differences in the calcaneus among extant great apes investigated by three-dimensional geometric morphometrics

Investigating the morphological differences of the calcaneus in humans and great apes is crucial for reconstructing locomotor repertories of fossil hominins. However, morphological variations in the calcaneus of the great apes (chimpanzees, gorillas, and orangutans) have not been sufficiently studied. This study aims to clarify variations in calcaneal morphology among great apes based on three-dimensional geometric morphometrics. A total of 556 landmarks and semilandmarks were placed on the calcaneal surface to calculate the principal components of shape variations among specimens. Clear interspecific differences in calcaneal morphology were extracted, corresponding to the degree of arboreality of the three species. The most arboreal orangutans possessed comparatively more slender calcaneal tuberosity and deeper pivot region of the cuboid articular surface than chimpanzees and gorillas. However, the most terrestrial gorillas exhibited longer lever arm of the triceps surae muscle, larger peroneal trochlea, more concave plantar surface, more inverted calcaneal tuberosity, more everted cuboid articular surface, and more prominent plantar process than the orangutans and chimpanzees. These interspecific differences possibly reflect the functional adaptation of the calcaneus to locomotor behavior in great apes. Such information might be useful for inferring foot functions and reconstructing the locomotion of fossil hominoids and hominids.

New femoral remains of Nacholapithecus kerioi: Implications for intraspecific variation and Miocene hominoid evolution

The middle Miocene stem kenyapithecine Nacholapithecus kerioi (16–15 Ma; Nachola, Kenya) is represented by a large number of isolated fossil remains and one of the most complete skeletons in the hominoid fossil record (KNM-BG 35250). Multiple fieldwork seasons performed by Japanese–Kenyan teams during the last part of the 20th century resulted in the discovery of a large sample of Nacholapithecus fossils. Here, we describe the new femoral remains of Nacholapithecus. In well-preserved specimens, we evaluate sex differences and within-species variation using both qualitative and quantitative traits. We use these data to determine whether these specimens are morphologically similar to the species holotype KNM-BG 35250 (which shows some plastic deformation) and to compare Nacholapithecus with other Miocene hominoids and extant anthropoids to evaluate the distinctiveness of its femur. The new fossil evidence reaffirms previously reported descriptions of some distal femoral traits, namely the morphology of the patellar groove. However, results also show that relative femoral head size in Nacholapithecus is smaller, relative neck length is longer, and neck–shaft angle is lower than previously reported for KNM-BG 35250. These traits have a strong functional signal related to the hip joint kinematics, suggesting that the morphology of the proximal femur in Nacholapithecus might be functionally related to quadrupedal-like behaviors instead of more derived antipronograde locomotor modes. Results further demonstrate that other African Miocene apes (with the exception of Turkanapithecus kalakolensis) generally fall within the Nacholapithecus range of variation, whose overall femoral shape resembles that of Ekembo spp. and Equatorius africanus. Our results accord with the previously inferred locomotor repertoire of Nacholapithecus, indicating a combination of generalized arboreal quadrupedalism combined with other antipronograde behaviors (e.g., vertical climbing).

Reassessment of the phylogenetic relationships of the late Miocene apes Hispanopithecus and Rudapithecus based on vestibular morphology

Late Miocene great apes are key to reconstructing the ancestral morphotype from which earliest hominins evolved. Despite consensus that the late Miocene dryopith great apes Hispanopithecus laietanus (Spain) and Rudapithecus hungaricus (Hungary) are closely related (Hominidae), ongoing debate on their phylogenetic relationships with extant apes (stem hominids, hominines, or pongines) complicates our understanding of great ape and human evolution. To clarify this question, we rely on the morphology of the inner ear semicircular canals, which has been shown to be phylogenetically informative. Based on microcomputed tomography scans, we describe the vestibular morphology of Hispanopithecus and Rudapithecus, and compare them with extant hominoids using landmark-free deformation-based three-dimensional geometric morphometric analyses. We also provide critical evidence about the evolutionary patterns of the vestibular apparatus in living and fossil hominoids under different phylogenetic assumptions for dryopiths. Our results are consistent with the distinction of Rudapithecus and Hispanopithecus at the genus rank, and further support their allocation to the Hominidae based on their derived semicircular canal volumetric proportions. Compared with extant hominids, the vestibular morphology of Hispanopithecus and Rudapithecus most closely resembles that of African apes, and differs from the derived condition of orangutans. However, the vestibular morphologies reconstructed for the last common ancestors of dryopiths, crown hominines, and crown hominids are very similar, indicating that hominines are plesiomorphic in this regard. Therefore, our results do not conclusively favor a hominine or stem hominid status for the investigated dryopiths.

PRECISIONS CONCERNING THE DISTRIBUTION AND IDENTIFICATION OF MIOCENE HOMINOIDS FROM INDIA

During the past four decades, the Indian Subcontinent has been a focus of palaeoanthropological research on account of the abundance of Middle and Late Miocene hominoid fossils that have been reported from it. In India, well known hominoid-bearing localities occur at Ramnagar (Lower Siwaliks) and Hari Talyangar (Middle Siwaliks), but there are less well known occurrences in the literature. If so, then current views of hominoid palaeobiogeography would need to be modified to the extent that an earlier passage of large hominoids out of Africa towards the Indian subcontinent than is generally accepted, would need to be postulated. We also examine a claim for the persistence of large hominoids up to the Mio-Pliocene boundary (ca 5.5 Ma) on the basis of a tooth found near Bharari, east of Hari Talyangar. The aim of this paper is to examine the soundness of the basis of claims for the presence of pre-Chinji large bodied hominoids in the region and for their persistence in the subcontinent up to the end of the Miocene epoch. With this aim in mind, in January, 2009, the authors surveyed the zone northwest of Dera Gopipur; 1) to locate the place from which a partial set of upper and lower teeth attributed to Ramapithecus cf. punjabicus were collected by S.S. Gupta and B.C. Verma in the 1978-79 field season of the Geological Survey of India, 2) to recover biochronologically informative faunal remains.

The new fossil record of <italic>Stegolophodon latidens</italic> from the Xiaolongtan locality, Yunnan, China, and the discussion on the age of the <italic>Lufengpithecus keiyuanensis</italic>

Lufengpithecus keiyuanensis from the Xiaolongtan Coal Mine is the earliest known Miocene fossil hominoids in southern China, yet its chronological context has long been subjected to disputes, in being either of late Middle Miocene or early Late Miocene age. This controversy is largely due to the uncertainty of the exact positions of previously discovered fossils in the outcrops, and the different chronological interpretations for some proboscidean and suid fossils from associated fossil faunal assemblages. Here we report the first discovery of Stegolophodon latidens from Xiaolongtan with an unambiguous stratigraphic provenance, which provides important evidence in constraining the age of Lufengpithecus keiyuanensis . Stegolophodon has a very high evolutionary rate of dental morphology, and exhibits a pronounced evolutionary trend with time: from the pentalophodont m3 of the Early Miocene or early Middle Miocene, to the pentalophodont M3 and hexalophodont m3 of the late Middle Miocene, to the 5.5-lophed (five principal lophs followed by an extreme well-developed cingulum) M3 and hexa- to heptalophodont m3 of the early Late Miocene, and to the hexalophodont M3 and hepta- to octalophodont m3 of the middle Late Miocene. The newly discovered Stegolophodon latidens bears a 5.5-lophed M3 and a heptalophodont m3, the second and subsequent lophs/lophids show a slight chevron structure, and the pretrite mesoconelets shift mesially and fuse with the corresponding pretrite anterior central conules, forming a “Y-shape”. These traits are similar to, or even slightly more derived than those of Stegolophodon from the lower part of the Dhok Pathan Formation (9.3−8.3 Ma) in the Middle Siwaliks of the Indian Subcontinent. The materials described here can all be assigned to Stegolophodon latidens which was originally discovered from the Yenangyaung fauna, the lower Irrawaddy Formation of Myanmar, deemed of early Late Miocene age. Revisions on the other proboscidean and suid materials also support an early Late Miocene age for Xiaolongtan Fauna. The new fossils were discovered from the upper part of the lignite layers, close to the bottom of the greyish marls of the Buzhaoba Formation. Based on the original records in the geological reports of the Xiaolongtan Coal Mine, the descriptions of the previous publications, as well as the accounts of the fossil finders, the Xiaolongtan coal mine possesses only one fossiliferous layer, which locates in the upper part on the Xiaolongtan Formation (lignite layers). Therefore, the new fossils situate possibly in the same layer as Lufengpithecus keiyuanensis that were found in the 1950’s and 1980’s. From the recent palaeomagnetic investigations, the age of this fossil layer should be 11.6/11.7 Ma, close to the boundary between the Middle and the late Miocene; however, seems to be slightly older than Stegolophodon latidens from the Siwaliks. Further investigations should be carried out to resolve this inconsistency.

New Middle Miocene Ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record.

The fossil record of 'lesser apes' (i.e. hylobatids = gibbons and siamangs) is virtually non-existent before the latest Miocene of East Asia. However, molecular data strongly and consistently suggest that hylobatids should be present by approximately 20 Ma; thus, there are large temporal, geographical, and morphological gaps between early fossil apes in Africa and the earliest fossil hylobatids in China. Here, we describe a new approximately 12.5-13.8 Ma fossil ape from the Lower Siwaliks of Ramnagar, India, that fills in these long-standing gaps with implications for hylobatid origins. This ape represents the first new hominoid species discovered at Ramnagar in nearly a century, the first new Siwalik ape taxon in more than 30 years, and likely extends the hylobatid fossil record by approximately 5 Myr, providing a minimum age for hylobatid dispersal coeval to that of great apes. The presence of crown hylobatid molar features in the new species indicates an adaptive shift to a more frugivorous diet during the Middle Miocene, consistent with other proposed adaptations to frugivory (e.g. uricase gene silencing) during this time period as well.

A micro-CT based study of molar enamel thickness and its distribution pattern in Late Miocene Lufengpithecus lufengensis from Yunnan in Southwestern China

ABSTRACT Molar enamel thickness and distribution pattern inform on the functional and dietary adaptation of extant and fossil primates. However, no systematic analysis of enamel thickness has been conducted on Lufengpithecus, a large-bodied fossil hominoid that lived in Southwest China during the late Miocene. In this study, we quantify two-dimensional (2D) enamel thickness and distribution of 68 lightly worn molars of Lufengpithecus (L.) lufengensis using micro-CT scanning data and compare it with modern humans, extant great apes, and fossil hominoids. The results indicate L. lufengensis has relatively thick enamel. It is slightly thicker than extant Pongo and comparable to some thick-enamel fossil pongines, but thinner than modern humans and most fossil hominins. The enamel distribution of L. lufengensis is distinctively unbalanced with relatively more enamel deposited on the cuspal region than the basal region in the molar crown, different from that found in modern humans and extant great apes. Concerning its palaeoecological and functional adaptations, we suggest that the features of thick-enamel and unbalanced distribution pattern in L. lufengensis is related to its adaptation to tough food and broader diets in a seasonal subtropical habitat.

Uplift of the Hengduan Mountains on the southeastern margin of the Tibetan Plateau in the late Miocene and its paleoenvironmental impact on hominoid diversity

The southeastern margin of the Tibetan Plateau has a number of well-known Late Miocene localities that have yielded fossil hominoids belonging to Lufengpithecus and Khoratpithecus. These localities provide critical evidence about the evolutionary history of hominoids, including their response to environmental changes associated with uplift of the Tibetan Plateau. Here we present magnetostratigraphic dating of the Baoshan hominoid locality in Yunnan, southwestern China, which, based on preliminary biochronological evidence, was previously assumed to be the youngest known Miocene hominoid locality in Eurasia. Paleomagnetic investigations yield three normal and three reversed magnetozones, which can be best correlated, in conjunction with biostratigraphic constraints, to Chrons C3n.4n to C3Ar. The Baoshan hominoid is derived from a horizon correlated with the lowest part of C3r, having an estimated age of ~6.0 Ma. This indicates that the Baoshan hominoid is slightly younger than L. cf. lufengensis from Zhaotong, dated to ~6.2 Ma, and L. lufengensis from Lufeng, dated to ~6.9–6.2 Ma. Our results, coupled with previously published magnetochronology, indicate that hominoids occurred in Southeast Asia from the latest Middle Miocene to the terminal Miocene (~13–6 Ma). The period after 6 Ma coincides with the uplift of the Hengduan Mountains, especially the Gaoligong Mountain. We propose that the Late Miocene uplift of these N-S oriented mountains on the southeastern margin of the Tibetan Plateau created a barrier to the warm and moist Indian monsoon from the west, and this led to a cooler and drier climate in the southeastern margin of the Tibetan Plateau. This paleoenvironmental change potentially had a profound impact on the diversity of the hominoid community in southwestern China and Southeast Asia.

Ontogenetic insights into the significance of mandibular corpus shape variation in hominoids: Developmental covariation between M2 crypt formation and corpus shape.

Here, we quantify and compare the cross-sectional shape of the mandibular corpus between M1 and M2 during growth in Pan paniscus, Pan troglodytes, and Pongo pygmaeus. The goal is to assess the hypothesis that the shape of the corpus is influenced by the development of permanent molars in their crypts, by examining ontogenetic changes in corpus shape and investigating covariation between corpus shape and M2 and M3 molar crypt forms. Ontogenetic changes in mandibular corpus shape were assessed using landmarks and semilandmarks, and measurements of length, width, and height were used to quantify molar crypts (M2 and M3 ). Ontogenetic changes in corpus growth from the eruption of M1 to the eruption of M3 were evaluated for each species through generalized Procrustes analysis and principal components analysis in shape-space and form-space. The relationship between corpus shape and molar crypt form was investigated at three different developmental stages using two-block partial least squares (2B-PLS) analysis. The results show clear differences in growth patterns among all three species and provide evidence that species-level differences in mandibular corpus growth occur prior to the emergence of M1 . The results of the 2B-PLS analysis reveal that significant covariance between corpus shape and molar crypt form is limited to the developmental stage marked by the emergence of M1 , with covariance between corpus shape and M2 crypt width. Corpora that are relatively narrower in the inferior portion of the cross section covary with relatively narrower M2 crypts. These results have important implications for understanding the taxonomic and phylogenetic significance of mandibular corpus shape variation in the hominoid fossil record.

High-resolution paleomagnetic constraint on the oldest hominoid- fossil-bearing sequence in the Xiaolongtan Basin, southeast margin of the Tibetan Plateau and its geologic implications

Abstract Sediments in the Xiaolongtan Basin at the southeastern margin of the Tibetan Plateau (SEMTP) not only contain an abundance of the oldest Chinese hominoid fossils, but also a record of the evolution of the Indian monsoon and the uplift of the southeastern Tibetan Plateau. However, these Middle–Upper Miocene sedimentary sequences have lacked a precise chronology, hampering our ability to reconstruct the regional tectonic uplift and the paleoecological environment. We carried out high-resolution paleomagnetic dating throughout the fluviolacustrine sequence in the Xiaolongtan Basin. The 487.5 m-thick sequence here revealed 11 reversed and 11 normal zones that span from chron 5n.2n to chron 5ACr, yielding magnetostratigraphic ages of ~14.1–10.0 Ma for the section, and 12.5 Ma and 11.7 Ma for the two hominoid-fossil bearing beds. Combined with lithological analyses and the evidence for ecological characteristics, we suggest that four notable ecological environmental phases had emerged in the Xiaolongtan Basin after it was formed at around 14.1 Ma. These were as follows: Phase I (14.1–12.6 Ma) with humid-hot forest steppe, Phase II (12.6–11.6 Ma) with subtropical evergreen broad-leaved forest, Phase III (11.6–10.0 Ma) with a hot-dry and evaporative shallow lake and Phase IV (after 10.0 Ma) with a subtropical semiarid steppe environment. After ~10.0 Ma deposition gradually ceased, albeit recurring sporadically until the Early Pleistocene.

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

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. 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 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. 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 hominoid fossils from Moroto II, Uganda and their bearing on the taxonomic and adaptive status of Morotopithecus bishopi

The early Miocene site of Moroto II, Uganda has yielded some of the oldest known hominoid fossils. A new partial mandible (UMP MORII 03'551) is notable for its long tooth row and large, narrow M2 with well-developed cristids - a morphological combination previously unknown for large bodied catarrhines of the Early Miocene and suggesting folivory. The tooth proportions are compatible with belonging to the same taxon as the maxilla UMP 62-11, the holotype of Morotopithecus bishopi; likewise, the long tooth row and vertical planum of UMP MORII 03'551 suggest that it may represent the same taxon as mandible(s) UMP 66-01 and UMP 62-10. Canine size strongly suggests UMP MORII 03'551 is a female. Comparisons of the tooth crown morphology and tooth row proportions, relative enamel thickness, enamel-dentine junction morphology, long-period line periodicity, and dental wear patterns support significant morphological, developmental, and inferred dietary differentiation, and therefore generic-level distinctiveness, among Afropithecus, Morotopithecus and the Proconsul clade. An isolated M1 (UMP MORII 03'559) is morphologically dissimilar, and much smaller than the actual or inferred size of molars in UMP MORII 03'551, UMP 66-01 and UMP 62-10, supporting the presence of two hominoid taxa at Moroto II, M. bishopi and a smaller bodied proconsulid. Given the high level of body mass dimorphism inferred for Morotopithecus and other early Miocene catarrhines, the known postcrania from Moroto II could be attributable to either taxon. However, UMP MORII 03'551 and the femora UMP MORII 94'80 derive from the same stratigraphic interval, while the isolated M1 was deposited later, increasing the likelihood that the mandible and femora are from the same individual. These new fossils expand our understanding of the taxonomic and adaptive diversity of early Miocene catarrhines.