Fossil apes from the vallès-penedès basin

A Dryopithecine Talus From Abocador de Can Mata (Vallès-Penedès Basin, NE Iberian Peninsula): Morphometric Affinities and Evolutionary Implications for Hominoid Locomotion

OBJECTIVES

The functional interpretation of postcranial remains of Middle Miocene great apes from Europe (dryopithecines) suggests a combination of quadrupedalism and orthograde behaviors without modern analogs. We provide further insights based on an isolated dryopithecine talus (IPS85037) from the Middle Miocene (11.7 Ma) Abocador de Can Mata locality ACM/C8-B* (Vallès-Penedès Basin, NE Iberian Peninsula), which represents the most complete one known to date.

MATERIAL AND METHODS

We compare the specimen with an extant anthropoid sample (n = 68) and the stem hominoid Ekembo heseloni (KMN RU 2036, ~18 Ma, Kenya) using 3D geometric morphometrics. For the two fossil tali, we assess their phenetic affinities using a between-group principal components analysis (bgPCA), estimate body mass based on centroid size, and make locomotor inferences using a partial least-squares regression (PLSR) between talar shape and locomotor repertoire.

RESULTS

Its large inferred body mass (~38 kg) and the possession of several modern hominoid-like features (albeit combined with more plesiomorphic traits) support the attribution of IPS85037 to a male dryopithecine. The bgPCA indicates that IPS85037 falls close to the extant hominoid variation and is less cercopithecoid-like than that of Ekembo, whose inferred locomotor repertoire is vastly dominated by quadrupedalism (81%). In contrast, the locomotor repertoire inferred from IPS85037 combines important quadrupedal (32%) and vertical climbing/clambering (50%) components with only moderate suspension (10%).

DISCUSSION

Our results align with previous inferences derived from other postcranial elements of Middle Miocene dryopithecines and, given their classification as crown hominoids, support the hypothesis that certain suspensory adaptations shared by extant hylobatids and hominids likely evolved independently.

Mutations Inactivating Biosynthesis of Dispensable Carbohydrate-Antigens Prevented Extinctions in Primate/Human Lineage Evolution

The human natural anti-carbohydrate antibodies anti-Gal, anti-Neu5Gc, and anti-Forssman are "living-fossils" that appeared in ancestral apes, monkeys and hominins millions of years ago. These antibodies appeared at various evolutionary periods in few mutated-offspring that lost the ability to synthesize the corresponding dispensable (i.e., nonessential) carbohydrate-antigens, α-gal epitope, Neu5Gc (N-glycolyl neuraminic acid) and Forssman-antigen, respectively. Production of these antibodies is stimulated by environmental antigens such as those of the human microbiota. Elimination of carbohydrate-antigens in the few mutated-offspring was caused by accidental nonsense or missense mutations that inactivated genes encoding enzymes involved in their biosynthesis, while most individuals in parental-populations continued synthesizing these carbohydrate-antigens. It has been suggested that dispensable carbohydrate-antigens which are absent in some mammalian species were evolutionary eliminated due to selective pressure by lethal viruses using these carbohydrate-antigens as "docking" receptors. An alternative selective mechanism which is based on the distribution of anti-Gal, anti-Neu5Gc and anti-Forssman in mammals, is presented in this review and is associated with the protective effects of these natural antibodies. It is suggested that epidemics of lethal enveloped-viruses caused the extinction of parental-populations synthesizing the corresponding carbohydrate-antigens of these antibodies,  independent of the cell adhesion mechanisms of such viruses. However, the few mutated offspring were protected by these natural antibodies which bound to carbohydrate-antigens synthesized on viruses as a result of their replication in individuals of the parental-populations. Recent studies suggest that these antibodies continue to contribute to the immune protection of humans against zoonotic infections by viruses presenting α-gal, Neu5Gc or Forssman antigens.

Reanalysis of Samburupithecus reveals similarities to nyanzapithecines

Samburupithecus kiptalami is an ape found in Late Miocene deposits (ca. 9.5 Ma) of northern Kenya. Initial assessments of the holotype specimen (KNM-SH 8531), a female-gorilla-sized maxillary fragment preserving the postcanine tooth row, noted similarities to gorillas or to African apes more broadly. More recently, primitive features of the maxilla and dentition have been used to propose a stem hominoid position for Samburupithecus. In particular, Samburupithecus shares some dental features with orepithecids (nyanzapithecines and Oreopithecus). To evaluate these competing hypotheses, and investigate possible affinities to oreopithecids, we reanalyzed the dentition of Samburupithecus quantitatively and assessed qualitative dental and maxillary features shared by oreopithecids and Samburupithecus. Based on the results of our analyses, we suggest that Samburupithecus is a late-occurring African oreopithecid, which we regard as a long-lived family of stem hominoids. The inclusion of Samburupithecus within Oreopithecidae highlights that stem hominoids and oreopithecids, in particular, spanned a large range of body sizes, similar to the range of size variation seen among all extant apes. Finally, the presence of oreopithecids in Africa on either side of a notable gap in the Late Miocene African fossil record of apes (from ∼13 to 10 Ma) demonstrates that the rarity of fossil African apes (i.e., nonhominin hominines) during this period is likely due to sampling biases rather than a recent immigration back into Africa from Eurasia.

New quantitative analyses of the Nacholapithecus kerioi proximal ulna confirm morphological affinities with Equatorius and large papionins

OBJECTIVES

The elbow of Nacholapithecus has been extensively described qualitatively, however its ulnar morphology has never been the focus of an in-depth quantitative analysis before. Hence, our main aim is quantifying the proximal ulnar morphology in Nacholapithecus and exploring whether it is similar to those of Equatorius and Griphopithecus as previously reported.

MATERIALS AND METHODS

We compared Nacholapithecus proximal ulnar morphology with a sample of extant and extinct anthropoids through principal component analysis and agglomerative hierarchical cluster analysis. Moreover, we calculated the Cophenetic Correlation Coefficient and checked for taxonomical group mean differences through MANOVA and pairwise post-hoc comparisons, as well as the phylogenetic signal in the variables used.

RESULTS

The Nacholapithecus ulna displays a moderately long and relatively narrow olecranon, a relatively wide trochlear surface-radial notch width, and a relatively thin sigmoid notch depth. These features resemble those of large papionins and chimpanzees, and some extinct taxa, mainly Equatorius.

DISCUSSION

Results presented here reinforce previous inferences on the functional morphology of the Nacholapithecus elbow, showing adaptations for general quadrupedal behaviors. However, other derived features (e.g., a relatively wide trochlear surface) might be associated with the ape-like traits described for its distal humerus (e.g., wide trochlear groove), thus displaying a combination of primitive and derived features in the proximal ulna. Finally, affinities with large papionins could suggest the presence of some terrestrial habits in Nacholapithecus. However, the lack of evidence in the rest of the skeleton prevents us from suggesting terrestrial affinities in this taxon in a conclusive manner.

The Miocene primate Pliobates is a pliopithecoid

The systematic status of the small-bodied catarrhine primate Pliobates cataloniae, from the Miocene (11.6 Ma) of Spain, is controversial because it displays a mosaic of primitive and derived features compared with extant hominoids (apes and humans). Cladistic analyses have recovered Pliobates as either a stem hominoid or as a pliopithecoid stem catarrhine (i.e., preceding the cercopithecoid-hominoid divergence). Here, we describe additional dental remains of P. cataloniae from another locality that display unambiguous synapomorphies of crouzeliid pliopithecoids. Our cladistic analyses support a close phylogenetic link with poorly-known small crouzeliids from Europe based on (cranio)dental characters but recover pliopithecoids as stem hominoids when postcranial characters are included. We conclude that Pliobates is a derived stem catarrhine that shows postcranial convergences with modern apes in the elbow and wrist joints-thus clarifying pliopithecoid evolution and illustrating the plausibility of independent acquisition of postcranial similarities between hylobatids and hominids.

Paleoenvironmental inferences on the Late Miocene hominoid-bearing site of Can Llobateres (NE Iberian Peninsula): An ecometric approach based on functional dental traits

Hispanopithecus laietanus from the Late Miocene (9.8 Ma) of Can Llobateres 1 (CLL1; Vallès-Penedès Basin, NE Iberian Peninsula) represents one of the latest occurrences of fossil apes in Western mainland Europe, where they are last recorded at ∼9.5 Ma. The paleoenvironment of CLL1 is thus relevant for understanding the extinction of European hominoids. To refine paleoenvironmental inferences for CLL1, we apply ecometric models based on functional crown type (FCT) variables-a scoring scheme devised to capture macroscopic functional traits of occlusal shape and wear surfaces of herbivorous large mammal molars. Paleotemperature and paleoprecipitation estimates for CLL1 are provided based on published regional regression models linking average FCT of large herbivorous mammal communities to climatic conditions. A mapping to Whittaker's present-day biome classification is also attempted based on these estimates, as well as a case-based reasoning via canonical variate analysis of FCT variables from five relevant biomes. Estimates of mean annual temperature (25 °C) and mean annual precipitation (881 mm) classify CLL1 as a tropical seasonal forest/savanna, only in partial agreement with the canonical variate analysis results, which classify CLL1 as a tropical rainforest with a higher probability. The former biome agrees better with previous inferences derived from fossil plants and mammals, as well as preliminary isotopic data. The misclassification of CLL1 as a tropical forest is attributed to the mixture of forest-adapted taxa with others adapted to more open environments, given that faunal and plant composition indicates the presence of a dense wetland/riparian forest with more open woodlands nearby. The tested FCT ecometric approaches do not provide unambiguous biome classification for CLL1. Nevertheless, our results are consistent with those from other approaches, thus suggesting that FCT variables are potentially useful to investigate paleoenvironmental changes through time and space-including those that led to the extinction of European Miocene apes.

The reconstructed cranium of Pierolapithecus and the evolution of the great ape face

Pierolapithecus catalaunicus (~12 million years ago, northeastern Spain) is key to understanding the mosaic nature of hominid (great ape and human) evolution. Notably, its skeleton indicates that an orthograde (upright) body plan preceded suspensory adaptations in hominid evolution. However, there is ongoing debate about this species, partly because the sole known cranium, preserving a nearly complete face, suffers from taphonomic damage. We 1) carried out a micro computerized tomography (CT) based virtual reconstruction of the Pierolapithecus cranium, 2) assessed its morphological affinities using a series of two-dimensional (2D) and three-dimensional (3D) morphometric analyses, and 3) modeled the evolution of key aspects of ape face form. The reconstruction clarifies many aspects of the facial morphology of Pierolapithecus. Our results indicate that it is most similar to great apes (fossil and extant) in overall face shape and size and is morphologically distinct from other Middle Miocene apes. Crown great apes can be distinguished from other taxa in several facial metrics (e.g., low midfacial prognathism, relatively tall faces) and only some of these features are found in Pierolapithecus, which is most consistent with a stem (basal) hominid position. The inferred morphology at all ancestral nodes within the hominoid (ape and human) tree is closer to great apes than to hylobatids (gibbons and siamangs), which are convergent with other smaller anthropoids. Our analyses support a hominid ancestor that was distinct from all extant and fossil hominids in overall facial shape and shared many features with Pierolapithecus. This reconstructed ancestral morphotype represents a testable hypothesis that can be reevaluated as new fossils are discovered.

A new ape from Türkiye and the radiation of late Miocene hominines

Fossil apes from the eastern Mediterranean are central to the debate on African ape and human (hominine) origins. Current research places them either as hominines, as hominins (humans and our fossil relatives) or as stem hominids, no more closely related to hominines than to pongines (orangutans and their fossil relatives). Here we show, based on our analysis of a newly identified genus, Anadoluvius, from the 8.7 Ma site of Çorakyerler in central Anatolia, that Mediterranean fossil apes are diverse, and are part of the first known radiation of early members of the hominines. The members of this radiation are currently only identified in Europe and Anatolia; generally accepted hominins are only found in Africa from the late Miocene until the Pleistocene. Hominines may have originated in Eurasia during the late Miocene, or they may have dispersed into Eurasia from an unknown African ancestor. The diversity of hominines in Eurasia suggests an in situ origin but does not exclude a dispersal hypothesis.

A reassessment of the distinctiveness of dryopithecine genera from the Iberian Miocene based on enamel-dentine junction geometric morphometric analyses

A vast diversity of catarrhines primates has been uncovered in the Middle to Late Miocene (12.5-9.6 Ma) of the Vallès-Penedès Basin (northeastern Spain), including several hominid species (Pierolapithecus catalaunicus, Anoiapithecus brevirostris, Dryopithecus fontani, Hispanopithecus laietanus, and Hispanopithecus crusafonti) plus some remains attributed to 'Sivapithecus' occidentalis (of uncertain taxonomic validity). However, Pierolapithecus and Anoiapithecus have also been considered junior synonyms of Dryopithecus by some authors, which entail a lower generic diversity and an inflated intrageneric variation of the latter genus. Since the distinction of these taxa partly relies on dental features, the detailed and quantitative analysis of tooth shape might help disentangling the taxonomic diversity of these Miocene hominids. Using diffeomorphic surface matching and three-dimensional geometric morphometrics, we investigate the enamel-dentine junction shape (which is a reliable taxonomic proxy) of these Miocene hominids, with the aim of investigating their degree of intra- and intergeneric variation compared with that of extant great ape genera. We conducted statistical analyses, including between-group principal component analyses, canonical variate analyses, and permutation tests, to investigate whether the individual and combined (i.e., Dryopithecus s.l.) variation of the extinct genera exceeds that of the extant great apes. Our results indicate that Pierolapithecus, Anoiapithecus, Dryopithecus, and Hispanopithecus show morphological differences of enamel-dentine junction shape relative to the extant great apes that are consistent with their attribution to different genera. Specifically, the variation displayed by the Middle Miocene taxa combined exceeds that of extant great ape genera, thus undermining the single-genus hypothesis. 'Sivapithecus' occidentalis specimens fall close to Dryopithecus but in the absence of well-preserved comparable teeth for Pierolapithecus and Anoiapithecus, their taxonomic attribution remains uncertain. Among the Hispanopithecus sample, IPS1802 from Can Llobateres stands out and might either be an outlier in terms of morphology, or represent another dryopithecine taxon.

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.

A revised (earliest Vallesian) age for the hominoid-bearing locality of Can Mata 1 based on new magnetostratigraphic and biostratigraphic data from Abocador de Can Mata (Vallès-Penedès Basin, NE Iberian Peninsula)

The Abocador de Can Mata (ACM) composite stratigraphic sequence (els Hostalets de Pierola, Vallès-Penedès Basin, NE Iberian Peninsula) has yielded a diverse primate assemblage from the late Aragonian (Middle to Late Miocene). Detailed litho-, bio-, and magnetostratigraphic control has enabled an accurate dating of these fossil remains. Comparable data, however, were lacking for the nearby locality of Can Mata 1 (CM1), which yielded a dryopithecine canine of a female individual. Given the lack of hipparionin equids and giraffids, CM1 has been correlated to the latest Aragonian (Mammal Neogene [MN] zone MN7+8). Here we revise the age of CM1 based on fieldwork and associated paleomagnetic samplings undertaken in 2018-2021. Our results extend the ACM composite sequence upward and indicate that CM1 correlates to the earliest Vallesian (MN9). The updated ACM sequence has a thickness of ∼300 m and comprises 12 magnetozones correlated to subchrons C5Ar.1r to C5n.2n (∼12.6-11.1 Ma; latest MN6 to earliest MN9, late Aragonian to earliest Vallesian). CM1 is correlated to C5r.1r (11.146-11.056 Ma), with an interpolated age of 11.11 Ma, thus postdating the dispersal of hipparionin horses into the Vallès-Penedès Basin-which is correlated to the previous subchron C5r.1n, with an interpolated age of 11.18 Ma, and by definition marks the beginning of the Vallesian. CM1 also minimally postdates the earliest record of giraffids at ACM-representing their earliest well-dated occurrence in the basin-being correlated to C5r.1n with an interpolated age of 11.11 Ma. We conclude that CM1 has an earliest Vallesian (MN9) age of ∼11.1 Ma, intermediate between the Aragonian dryopithecins and the Vallesian hispanopithecins. Ongoing paleontological surveillance at ACM thus offers the prospect to yield additional earliest Vallesian ape remains, which are essential to clarify their taxonomic allocation as well as to confirm whether hispanopithecins evolved locally from dryopithecins rather than immigrating from elsewhere during MN9.

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.

Examination of magnitudes of integration in the catarrhine vertebral column

The evolution of novel vertebral morphologies observed in humans and other extant hominoids may be related to changes in the magnitudes and/or patterns of covariation among traits. To examine this, we tested magnitudes of integration in the vertebral column of cercopithecoids and hominoids, including humans. Three-dimensional surface scans of 14 vertebral elements from 30 Cercopithecus, 32 Chlorocebus, 39 Macaca, 45 Hylobates, 31 Pan, and 86 Homo specimens were used. A resampling method was used to generate distributions of integration coefficient of variation scores for vertebral elements individually using interlandmark distances. Interspecific comparisons of mean integration coefficient of variation were conducted using Mann-Whitney U tests with Bonferroni adjustment. The results showed that hominoids generally had lower mean integration coefficient of variation than cercopithecoids. In addition, humans showed lower mean integration coefficient of variation than other hominoids in their last thoracic and lumbar vertebrae. Cercopithecoids and Hylobates showed relatively lower mean integration coefficient of variation in cervical vertebrae than in thoracolumbar vertebrae. Pan and Homo showed relatively lower mean integration coefficient of variation in the last thoracic and lumbar vertebrae in the thoracolumbar region, except for the L1 of Pan. The results suggest fewer integration-mediated constraints on the evolution of vertebral morphology in hominoids when compared with cercopithecoids. The weaker magnitudes of integration in lumbar vertebrae in humans when compared with chimpanzees likewise suggest fewer constraints on the evolution of novel lumbar vertebrae morphology in humans.

Fossil apes and human evolution

Humans diverged from apes (chimpanzees, specifically) toward the end of the Miocene ~9.3 million to 6.5 million years ago. Understanding the origins of the human lineage (hominins) requires reconstructing the morphology, behavior, and environment of the chimpanzee-human last common ancestor. Modern hominoids (that is, humans and apes) share multiple features (for example, an orthograde body plan facilitating upright positional behaviors). However, the fossil record indicates that living hominoids constitute narrow representatives of an ancient radiation of more widely distributed, diverse species, none of which exhibit the entire suite of locomotor adaptations present in the extant relatives. Hence, some modern ape similarities might have evolved in parallel in response to similar selection pressures. Current evidence suggests that hominins originated in Africa from Miocene ape ancestors unlike any living species.

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.

Palaeoecological differences underlie rare co-occurrence of Miocene European primates

Background

The two main primate groups recorded throughout the European Miocene, hominoids and pliopithecoids, seldom co-occur. Due to both their rarity and insufficiently understood palaeoecology, it is currently unclear whether the infrequent co-occurrence of these groups is due to sampling bias or reflects different ecological preferences. Here we rely on the densely sampled primate-bearing sequence of Abocador de Can Mata (ACM) in Spain to test whether turnovers in primate assemblages are correlated with palaeoenvironmental changes. We reconstruct dietary evolution through time (ca. 12.6–11.4 Ma), and hence climate and habitat, using tooth-wear patterns and carbon and oxygen isotope compositions of enamel of the ubiquitous musk-deer Micromeryx.

Results

Our results reveal that primate species composition is strongly correlated with distinct environmental phases. Large-bodied hominoids (dryopithecines) are recorded in humid, densely-forested environments on the lowermost portion of the ACM sequence. In contrast, pliopithecoids inhabited less humid, patchy ecosystems, being replaced by dryopithecines and the small-bodied Pliobates toward the top of the series in gallery forests embedded in mosaic environments.

Conclusions

These results support the view that pliopithecoid primates preferred less humid habitats than hominoids, and reveal that differences in behavioural ecology were the main factor underpinning their rare co-occurrence during the European Miocene. Our findings further support that ACM hominoids, like Miocene apes as a whole, inhabited more seasonal environments than extant apes. Finally, this study highlights the importance of high-resolution, local investigations to complement larger-scale analyses and illustrates that continuous and densely sampled fossiliferous sequences are essential for deciphering the complex interplay between biotic and abiotic factors that shaped past diversity.

The evolution of the vestibular apparatus in apes and humans

Phylogenetic relationships among extinct hominoids (apes and humans) are controversial due to pervasive homoplasy and the incompleteness of the fossil record. The bony labyrinth might contribute to this debate, as it displays strong phylogenetic signal among other mammals. However, the potential of the vestibular apparatus for phylogenetic reconstruction among fossil apes remains understudied. Here we test and quantify the phylogenetic signal embedded in the vestibular morphology of extant anthropoids (monkeys, apes and humans) and two extinct apes (Oreopithecus and Australopithecus) as captured by a deformation-based 3D geometric morphometric analysis. We also reconstruct the ancestral morphology of various hominoid clades based on phylogenetically-informed maximum likelihood methods. Besides revealing strong phylogenetic signal in the vestibule and enabling the proposal of potential synapomorphies for various hominoid clades, our results confirm the relevance of vestibular morphology for addressing the controversial phylogenetic relationships of fossil apes.

Early anthropoid femora reveal divergent adaptive trajectories in catarrhine hind-limb evolution

The divergence of crown catarrhines—i.e., the split of cercopithecoids (Old World monkeys) from hominoids (apes and humans)—is a poorly understood phase in our shared evolutionary history with other primates. The two groups differ in the anatomy of the hip joint, a pattern that has been linked to their locomotor strategies: relatively restricted motion in cercopithecoids vs. more eclectic movements in hominoids. Here we take advantage of the first well-preserved proximal femur of the early Oligocene stem catarrhine Aegyptopithecus to investigate the evolution of this anatomical region using 3D morphometric and phylogenetically-informed evolutionary analyses. Our analyses reveal that cercopithecoids and hominoids have undergone divergent evolutionary transformations of the proximal femur from a similar ancestral morphology that is not seen in any living anthropoid, but is preserved in Aegyptopithecus, stem platyrrhines, and stem cercopithecoids. These results highlight the relevance of fossil evidence for illuminating key adaptive shifts in primate evolution.

The proximal femur is key for understanding locomotion in primates. Here, the authors analyze the evolution of the proximal femur in catarrhines, including a new Aegyptopithecus fossil, and suggest that Old World monkeys and hominoids diverged from an ancestral state similar to Aegyptopithecus.

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

OBJECTIVES

This study aims to virtually reconstruct the deformed face (XIR-1) and maxilla (RPl-128) of the Late Miocene hominoid Ouranopithecus macedoniensis from Greece, through the application of mirror-imaging and segmentation. Additionally, analysis was conducted through 3D geometric morphometrics, utilizing a comparative sample of fossil hominoids, extant great apes (Gorilla, Pan, and Pongo) and humans, so as to explore shape variation and phenetic similarities between them.

MATERIALS AND METHODS

High-resolution computed tomography was used to create digital representations of the XIR-1 and RPl-128 specimens. The virtual reconstruction of the XIR-1 cranium was achieved by mirror-imaging, while the RPl-128 maxilla was virtually segmented and reattached in a correct anatomical position. Anatomical landmarks were registered in three dimensions on a comparative sample of adult crania of extant great apes, humans and fossil hominoids. The data were processed with Procrustes superimposition and analyzed using multivariate statistics methods.

RESULTS

Results show that Ouranopithecus macedoniensis falls within or close to the Gorilla convex hull in the principal component analyses, and it is closer to the mean Procrustes shape distance of primarily Gorilla. Both specimens, XIR-1 and RPl-128, are classified as Gorilla based on discriminant function analyses.

DISCUSSION

The results of our geometric morphometrics analyses indicate that Ouranopithecus macedoniensis is morphologically more similar to Gorilla than to Homo, Pan, or Pongo, results that can contribute to the evaluation of existing hypotheses about its phylogenetic position.

The morphology and evolutionary history of the glenohumeral joint of hominoids: A review

The glenohumeral joint, the most mobile joint in the body of hominoids, is involved in the locomotion of all extant primates apart from humans. Over the last few decades, our knowledge of how variation in its morphological characteristics relates to different locomotor behaviors within extant primates has greatly improved, including features of the proximal humerus and the glenoid cavity of the scapula, as well as the muscles that function to move the joint (the rotator cuff muscles). The glenohumeral joint is a region with a strong morphofunctional signal, and hence, its study can shed light on the locomotor behaviors of crucial ancestral nodes in the evolutionary history of hominoids (e.g., the last common ancestor between humans and chimpanzees). Hominoids, in particular, are distinct in showing round and relatively big proximal humeri with lowered tubercles and flattened and oval glenoid cavities, morphology suited to engage in a wide range of motions, which enables the use of locomotor behaviors such as suspension. The comparison with extant taxa has enabled more informed functional interpretations of morphology in extinct primates, including hominoids, from the Early Miocene through to the emergence of hominins. Here, I review our current understanding of glenohumeral joint functional morphology and its evolution throughout the Miocene and Pleistocene, as well as highlighting the areas where a deeper study of this joint is still needed.

Can Pallars i Llobateres: A new hominoid-bearing locality from the late Miocene of the Vallès-Penedès Basin (NE Iberian Peninsula)

In the Iberian Peninsula, Miocene apes (Hominoidea) are generally rare and mostly restricted to the Vallès-Penedès Basin. Here we report a new hominoid maxillary fragment with M² from this basin. It was surface-collected in March 2017 from the site of Can Pallars i Llobateres (CPL, Sant Quirze del Vallès), where fossil apes had not been previously recorded. The locality of provenance (CPL-M), which has delivered no further fossil remains, is located very close (ca. 50 m) to previously known CPL outcrops, and not very far (ca. 500 m in NW direction) from the classical hominoid-bearing locality of Can Poncic 1. Here we describe the new fossil and, based on the size and proportions of the M², justify its taxonomic attribution to Hispanopithecus cf. laietanus, a species previously recorded from several Vallesian sites of the Vallès-Penedès Basin. Based on the associated mammalian fauna from CPL, we also provide a biochronological dating and a paleoenvironmental reconstruction for the site. The associated fauna enables an unambiguous correlation to the Cricetulodon hartenbergeri - Progonomys hispanicus interval local subzone, with an estimated age of 9.98-9.73 Ma (late Vallesian, MN10). Therefore, CPL-M is roughly coeval with the Hispanopithecus laietanus-bearing localities of Can Llobateres 1 and Can Feu 1, and minimally older than those of La Tarumba 1 and Can Llobateres 2. In contrast, CPL-M is younger than the early Vallesian (MN9) localities of Can Poncic 1 (the type locality of Hispanopithecus crusafonti) as well as Polinyà 2 (Gabarró) and Estació Depuradora d'Aigües Residuals-Riu Ripoll 13, where Hispanopithecus sp. is recorded. The associated fauna from CPL indicates a densely forested and humid paleoenvironment with nearby freshwater. This supports the view that Hispanopithecus might have been restricted to dense wetland forests soon before its extinction during the late Vallesian, due to progressive climatic deterioration. Coupled with the existence of other fossiliferous outcrops in the area, this find is most promising for the prospect of discovering additional fossil hominoid remains in the future.

Understanding climate's influence on the extinction of Oreopithecus (late Miocene, Tusco-Sardinian paleobioprovince, Italy)

Despite its long history of scientific study, the causes underlying the extinction of the insular hominoid Oreopithecus bambolii are still a matter of ongoing debate. While some authors consider intense tectonism and invading species the cause of its extinction ca. 6.7 Ma, others propose climatic change as the main contributing factor. We rely on long-term patterns of tooth wear and hypsodonty of the Baccinello and Fiume Santo herbivore-faunas to reconstruct changes in habitat prior to, during and after the extinction. While a mosaic of habitats was represented in Baccinello V1 (as shown by a record of browsers, mixed feeders and species engaged in grazing), more closed forests (higher proportion of browsers, shortage of mixed feeders and lack of grazers) characterised Baccinello V2. Finally, there was a partial loss of canopy cover and development of open-patches and low-abrasive grasses in Baccinello V3 (as denoted by new records of taxa involved in grazing)-although still dominated by a forested habitat (since browse was a component in all diets). Our results provide evidence for two perceptible shifts in climate, one between 8.1 and 7.1 Ma and other ca. 6.7 Ma, though this latter was not drastic enough to lead to intensive forest loss, substantially alter the local vegetation or affect Oreopithecus lifestyle-especially if considering the growing evidence of its versatile diet. Although the disappearance of Oreopithecus is complex, our data reject the hypothesis of environmental change as the main factor in the extinction of Oreopithecus and Maremma fauna. When our results are analysed together with other evidence, faunal interaction and predation by invading species from mainland Europe seems to be the most parsimonious explanation for this extinction event. This contrasts with European hominoid extinctions that were associated with major climatic shifts that led to environmental uniformity and restriction of the preferred habitats of Miocene apes.

Why Do We Produce Anti-Gal

The natural anti-Gal antibody is one of the multiple natural anti-carbohydrate antibodies produced in humans against a wide range of carbohydrate antigens on GI bacteria. The antibody is unique to humans, apes, and Old World monkeys, and it binds specifically to a mammalian carbohydrate antigen called the α-gal epitope that is synthesized in nonprimate mammals, lemurs (prosimians) and New World monkeys by the glycosylation enzyme α1,3GT. The α1,3GT gene (GGTA1) appeared in mammals >100 million years ago, prior to the split between marsupial and placental mammals. This gene has been conserved in its active form, in all mammals, except for Old World monkeys, apes, and humans. Inactivation of the α1,3GT gene in ancestral Old World primates occurred 20–30 million years ago and could have been associated with epidemics of enveloped viruses in the Eurasia-Africa continent. It is suggested that prior to such epidemics, few ancestral Old World primates acquired deletion point mutations that inactivated the α1,3GT gene and eliminated α-gal epitopes. This resulted in loss of immune tolerance to the α-gal epitope and thus, in production of the anti-Gal antibody against antigens on bacteria colonizing the GI tract. This accidental inactivation of the α1,3GT gene in very small populations is analogous to the highly rare blood type “Bombay” individuals who do not synthesize blood group H (O antigen) because of inactivation of the α1,2-fucosyltransferase gene. The loss of immune tolerance to blood group H antigen has resulted in production of natural anti-blood group H antibodies in the blood group Bombay individuals. It is suggested that anti-Gal protected against infections by enveloped viruses presenting α-gal epitopes, which were lethal to the parental primate populations that conserved active α1,3GT and thus, synthesized α-gal epitopes. Alternative causes for the elimination of Old World primates synthesizing α-gal epitopes could be bacteria or protozoa parasites presenting α-gal or α-gal-like epitopes, and bacterial toxins, or detrimental viruses that used α-gal epitopes in these primates as “docking receptors.” Ultimately, any of these proposed selective processes could result in extinction of Old World primates synthesizing α-gal epitopes on their cells. These ancestral primates were replaced by offspring populations lacking α-gal epitopes and producing the anti-Gal antibody, which continues to be produced by Old World monkeys, apes, and humans. New World monkeys and lemurs were protected from pathogens of the Old World by oceanic barriers, thus they continue to synthesize α-gal epitopes and lack the ability to produce the anti-Gal antibody. This scenario of few individuals in a large population having a mutation(s) that inactivates a glycosyltransferase gene thus, resulting in production of evolutionary advantageous natural antibodies against the eliminated carbohydrate antigen, may reflect one of the mechanisms inducing changes in the carbohydrate profile of various mammalian populations.

Natural anti-carbohydrate antibodies contributing to evolutionary survival of primates in viral epidemics?

Humans produce multiple natural antibodies against carbohydrate antigens on gastrointestinal bacteria. Two such antibodies appeared in primates in recent geological times. Anti-Gal, abundant in humans, apes and Old-World monkeys, appeared 20-30 million years ago (mya) following inactivation of the α1,3GT gene (GGTA1). This gene encodes in other mammals the enzyme α1,3galactosyltransferase (α1,3GT) that synthesizes α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R) which bind anti-Gal. Anti-Neu5Gc, found only in humans, appeared in hominins <6 mya, following elimination of N-glycolylneuraminic-acid (Neu5Gc) because of inactivation of CMAH, the gene encoding hydroxylase that converts N-acetylneuraminic-acid (Neu5Ac) into Neu5Gc. These antibodies, were initially produced in few individuals that acquired random mutations inactivating the corresponding genes and eliminating α-gal epitopes or Neu5Gc, which became nonself antigens. It is suggested that these evolutionary selection events were induced by epidemics of enveloped viruses, lethal to ancestral Old World primates or hominins. Such viruses presented α-gal epitopes or Neu5Gc, synthesized in primates that conserved active GGTA1 or CMAH, respectively, and were lethal to their hosts. The natural anti-Gal or anti-Neu5Gc antibodies, produced in offspring lacking the corresponding carbohydrate antigens, neutralized and destroyed viruses presenting α-gal epitopes or Neu5Gc. These antibodies further induced rapid, effective immune responses against virus antigens, thus preventing infections from reaching lethal stages. These epidemics ultimately resulted in extinction of primate populations synthesizing these carbohydrate antigens and their replacement with offspring populations lacking the antigens and producing protective antibodies against them. Similar events could mediate the elimination of various carbohydrate antigens, thus preventing the complete extinction of other vertebrate species.

Morphology and environment in some fossil Hominoids and Pedetids (Mammalia)

Linking the environment to functional anatomy is not an easy exercise, especially when dealing with fossils, which are often fragmentary and represent animals that are extinct. A holistic approach permits us to fill the gaps in reconstructing the evolutionary patterns in fossil groups. Identifying the environment where animals lived can help to interpret some anatomical structures and, vice versa, the functional morphological pattern can help to refine some fossil environments. Two examples focusing on locomotor behaviours in fossil mammals are considered in this paper: the hominoids and the origins of hominid bipedalism and the springing adaptations in fossil rodents (Pedetidae) in connection with different habitats. In the first case, the limits of the chimp-based models and the necessity to take into account detailed environmental reconstructions will be addressed. The famous 'savannah hypothesis' is no longer tenable because the palaeontological data support a more vegetated environment for the origins of bipedal hominids. Data from the environment will be considered. The earliest putative hominid fossils which preserve skeletal remains of the locomotor apparatus show mixed adaptations to terrestrial bipedalism and arboreal activities. The second example focuses on the variation in springing adaptations in Pedetidae in the Lower Miocene of East Africa and Southern Africa. In the East, the sites where Pedetidae were preserved were mainly forested, whereas in the South the region was more open and drier, with extensive grassy patches. In the first case, pedetids were robust and heavy jumpers, whereas in the South they were smaller, their skeleton more gracile and their springing was lighter. During the desertification of the southern part of Africa, the large pedetid species became extinct, but a smaller species developed. In the case of primates, as in the case of rodents, the skeletal morphology was adapted to its environment.