Postcranial Fossils Research Articles

Lufengpithecus inner ear provides evidence of a common locomotor repertoire ancestral to human bipedalism

Various lines of evidence have been used to infer the origin of human bipedalism, but the paucity of hominoid postcranial fossils and the diversity of inferred locomotor modes have tended to confound the reconstruction of ancestral morphotypes. Examination of the bony labyrinth morphology of the inner ear of extinct and living hominoids provides independent evidence for inferring the evolution of hominoid locomotor patterns. New computed tomography data and morphometric analyses of the Late Miocene ape Lufengpithecus indicate that it and other stem great apes possess labyrinths similar to one another and show that hominoids initially evolved from a positional repertoire that included orthogrady, below-branch forelimb suspension and progression, above-branch bipedalism, climbing, clambering, and leaping (hylobatid-like) to one that comprised above-branch quadrupedalism, below-branch forelimb suspension, vertical climbing, limited leaping, terrestrial quadrupedal running and walking, possibly with knuckle walking, and short bouts of bipedalism (chimpanzee-like). The bony labyrinth morphology of Lufengpithecus indicates that it probably conforms more closely to the last common ancestors of crown hominoids and hominids in its locomotor behavior than do other Miocene hominoids. Human bipedalism evolved from this common archetypal Lufengpithecus-like locomotor repertoire. The low evolutionary rate of semicircular canal morphology suggests that Lufengpithecus experienced a relative stasis in locomotor behavior, probably due to the uplift of the Tibetan Plateau, which created a stable environment in the Miocene of southwestern China.

Pleistocene Asian black bear (Ursus thibetanus Cuvier, 1823) in the Iberian Peninsula: new evidence and a complete review

The Asian black bear (Ursus thibetanus Cuvier, 1823) is a medium-sized ursid that currently mostly inhabits environments of dense foliage and forests in southern and eastern Asia. This species is currently extinct in Europe, but during the Middle Pleistocene and the beginning of the Late Pleistocene its distribution was wider and reached until Southern Siberia, the Ural Mountains, Caucasus and western Europe. The main objective of this work is to provide a detailed description of all the Ursus thibetanus remains from the Iberian Peninsula, describing for the first time the new remains, and discuss the chronological framework of the presence of this taxon in the largest of the southern European peninsulas. The Iberian Peninsula has yielded paleontological evidence of this taxon in five sites (Bolomor, Koskobilo, La Llanera, Cau d'en Borràs and Villavieja), and we present new paleontological evidence from the latter three sites, which is important due to the scarcity of U. thibetanus fossil remains. We compare the morphology of these new remains with both European Pleistocene fossils and recent U. thibetanus. Up until recently, its distribution in Iberia was thought to be restricted to the East of the Iberian Peninsula. But the recent identification of U. thibetanus remains in Koskobilo (Navarre) and in La Llanera (Oviedo) has resulted in a wider distribution of this species than what was previously thought. The dental remains from Koskobilo, La Llanera, Villavieja, Bolomor and Cau d'en Borràs fit well within the Pleistocene U. thibetanus from Europe morphologically and metrically. Some Iberian remains are morphologically similar to previously described U. thibetanus Pleistocene fossil subspecies. A M2 from Bolomor is morphologically closer to U. t. mediterraneus (MIS 7), and a M2 from Koskobilo is similar to U. t. kurteni (MIS 6–7). The postcranial fossil remains from Cau d'en Borràs and Villavieja fit well within the recent U. thibetanus range of variation. Except for the remains from Bolomor (MIS 5e and MIS 7), the rest of the Iberian U. thibetanus fossils are difficult to ascribe chronologically. Based on other biochronological proxies, Cau d'en Borràs and Koskobilo can tentatively be assigned to the MIS 7–5 range, Villavieja could be assigned to MIS 13–5, and La Llanera is probably the oldest record of U. thibetanus in Iberia (MIS 15–13). However, until new direct datings are performed on the sites, the proposed chronologies should be regarded with caution.

Taxonomic attribution of the KNM-ER 1500 partial skeleton from the Burgi Member of the Koobi Fora Formation, Kenya

Paranthropus boisei is well represented in the eastern African fossil record by craniodental remains, but very few postcranial fossils can be securely attributed to this taxon. For this reason, KNM-ER 1500 from East Turkana, Kenya, is especially important. KNM-ER 1500 is a badly weathered and fragmented postcranial skeleton associated with a small piece of mandibular corpus. It derives from the Burgi Member, which has yielded diagnostic craniodental fossils attributable to P. boisei, Homo habilis, Homo rudolfensis and Homo erectus. Although it has been proposed that KNM-ER 1500 may be attributable to P. boisei based on the small mandibular fragment, this hypothesis remained challenging to test. Here we re-examine the preserved portions of KNM-ER 1500 and reassess support for its taxonomic attribution. There are compelling features of the mandible, proximal femur, and especially the proximal radius that support attribution of KNM-ER 1500 to P. boisei. These features include the absolute width of the mandible and its lack of a lateral intertoral sulcus, an anteroposteriorly compressed femoral neck with a distinctive posteroinferior marginal ridge, the rim of the radial head that is proximodistally uniform in thickness around its circumference, and a long radial neck that is elliptical in cross section. No feature serves to align KNM-ER 1500 with Homo to the exclusion of Paranthropus. KNM-ER 1500 was a small-bodied individual and attributing this specimen to P. boisei confirms that significant postcranial-size dimorphism was present in this species.

Updated study of adult and subadult pectoral girdle bones from Sima de los Huesos site (Sierra de Atapuerca, Burgos, Spain). Anatomical and age estimation keys.

Here we present an updated inventory and study of pectoral girdle remains recovered from the Sima de los Huesos (SH) site. Here, we describe the key morphological traits of adults and, for the first time, subadult specimens. Because morphological traits can change with age, we also discuss some shortcomings related to age estimation in postcranial fossil specimens. Adult clavicles from the SH are long with a low robusticity index and marked curvatures in the superior view. Among these traits, only extreme clavicular length seems to characterize subadult individuals. Neandertals share all these traits. In the case of the scapula, the SH specimens share a relatively long and narrow glenoid fossa with Neandertals. This trait is also present in subadult individuals. Additionally, most specimens from SH, adults, and subadults showed a dorsal axillary sulcus on the scapular lateral border, a trait also present in most adult and subadult Neandertals. These traits in adult and subadult specimens supports substantial genetic control for many of them in both human species.

Bone histology in a fossil elephant (Elephas maximus) from Pulau Bangka, Indonesia

ABSTRACT Analyses of Pleistocene fossil proboscideans have long been used as indirect evidence for climactic and environmental shifts in the Sunda shelf of Southeast Asia. Reconstructing the biological effects of rainforest expansion at the Last Glacial Maximum on elephants can be enhanced by a better understanding of fossil proboscidean palaeobiology. We studied fragmented post-cranial fossil remains of an Asian elephant (Elephas maximus) from Pulau Bangka, an island to the east of Sumatra, hypothesised to be within the Late Pleistocene Sundaland savannah corridor. Bone histology of the humerus, rib, and vertebrae from the Bangka fossil were examined and compared with modern conspecifics to reconstruct remodelling. We measured secondary osteon population density, osteon area, diameter, and infill ratios in Haversian bone. Intra-skeletally, we found that the histology of the largely weight-bearing humerus indicated slower remodelling than that of the ribs and vertebrae, which are less biomechanically constrained. Inter-skeletally, the fossil rib histology showed relatively smaller osteons and Haversian canals when compared to the modern samples. Differences in lifestyles, including range-expansion, may have influenced micro-morphometric differences in elephant rib histology. Our results contribute indirect evidence of the effects of climactic variability in the Sunda palaeoenvironment on Pleistocene fauna.

Diversity of Pleistocene megamammals from southern Amazon, Mato Grosso state, Brazil

The Amazon region is a key area to understand the South America history, displaying a significant importance in the study of Pleistocene mammal fossils. Here, we present the taxonomic account of the first megafaunal records of the Quaternary deposits from bed and alluvial terraces from the Teles Pires River and its tributaries, in northern Mato Grosso state, southern Brazilian Amazon. Teeth, partial dentaries and postcranial fossil specimens have been described and identified as immature to senile individuals of Notiomastodon platensis, cf. Eremotherium and Toxodon platensis. These species were well-dispersed along the Pleistocene in South America, including the Amazon region. This paper brings up the paleontological potential of the upper Teles Pires basin, midwest Brazil, for South American Pleistocene megafauna. Further studies are necessary in order to obtain more information regarding the location and genesis of the fossiliferous assemblages, and the paleoecological and taphonomic aspects of the megamammal paleocommunities in the southern Amazon.

First Snout with Complete Teeth Row of Small Titanosaur in Indo-Pakistan Found from the Latest Maastrichtian Vitakri Formation of Pakistan; Associated Cranial and Postcranial Skeletons of <i>Saraikimasoom vitakri</i> (Poripuchia, Stocky Titanosauria, Sauropoda) from Pakistan and Referred Fossils from India

Titanosaurs articulated cranial elements especially jaw bones with articulated complete teeth row are extraordinarily rare. Here the holotypic snout with articulated jaw bones and complete teeth row of Saraikimasoom vitakri are being presented which has international significance and contributes to understanding the evolutionary relationships and paleobiogeographic history of the vertebrates of Indo-Pakistan subcontinent. The completeness of the skeleton, in particular the presence of a well-preserved skull has a significant influence on resolution of titanosaur phylogeny. Here Saraikimasoom vitakri holotypic snout from South Kinwa, and referred jaw with articulated pointed and rounded teeth along with associated postcranial fossils from north Kinwa, and other associated materials from Mari Bohri, mid-Sangiali, Zubra Basti Nala and Grut localities of Pakistan are being presented. All these assemblages show consistent results.

The alpha taxonomy of Australopithecus at Sterkfontein: The postcranial evidence

The possibility that the fossils attributed to Australopithecus africanus represent more than a single species is of significance because of the pivotal role that A. africanus has played in discussions about hominin evolution. The A. africanus hypodigm that is currently widely recognized evinces considerable variation in a number of craniodental characters, and this has led to speculation that more than one australopith taxon may be represented among the specimens from Sterkfontein. Although crania, mandibles and teeth have dominated these taxonomic discussions, the Sterkfontein postcranial remains also have been invoked. While several workers have proposed that some of the craniodental remains from Sterkfontein can be partitioned into two groups, there is a notable lack of agreement among them as to their actual sorting. Most of the craniodental observations that have been put forward in support of arguments for taxonomic heterogeneity of the Sterkfontein australopith assemblage have been subjective and anecdotal in nature. So too, the postcranial evidence that has been cited in support of more than one australopith species at Sterkfontein has been largely subjective, and limited to a small number of elements. The results of quantitative statistical analyses of the craniodental and postcranial fossils that have been undertaken to date are not necessarily consistent with the hypothesis of taxonomic heterogeneity.

Excavation, reconstruction and taphonomy of the StW 573 Australopithecus prometheus skeleton from Sterkfontein Caves, South Africa

Postcranial bones may provide valuable information about fossil taxa relating to their locomotor habits, manipulative abilities and body sizes. Distinctive features of the postcranial skeleton are sometimes noted in species diagnoses. Although numerous isolated postcranial fossils have become accepted by many workers as belonging to a particular species, it is worthwhile revisiting the evidence for each attribution before including them in comparative samples in relation to the descriptions of new fossils, functional analyses in relation to particular taxa, or in evolutionary contexts. Although some workers eschew the taxonomic attribution of postcranial fossils as being less important (or interesting) than interpreting their functional morphology, it is impossible to consider the evolution of functional anatomy in a taxonomic and phylogenetic vacuum. There are 21 widely recognized hominin taxa that have been described from sites in Africa dated from the Late Miocene to the Middle Pleistocene; postcranial elements have been attributed to 17 of these. The bones that have been thus assigned range from many parts of a skeleton to isolated elements. However, the extent to which postcranial material can be reliably attributed to a specific taxon varies considerably from site to site and species to species, and is often the subject of considerable debate. Here, we review the postcranial remains attributed to African hominin taxa from the Late Miocene to the Middle and Late Pleistocene and place these assignations into categories of reliability. The catalog of attributions presented here may serve as a guide for making taxonomic decisions in the future.

Astragalus of Pondaungimys (Rodentia, Anomaluroidea) from the late middle Eocene Pondaung Formation, central Myanmar

ABSTRACTA well-preserved astragalus of the anomaluroid rodent Pondaungimys anomaluropsis is described from the late middle Eocene Pondaung Formation of central Myanmar. This specimen is the first postcranial element of a rodent from the Pondaung Formation and the oldest postcranial fossil currently known for Anomaluroidea. It illuminates plesiomorphous postcranial conditions in early anomaluroids and provides a basis for reconstructing the evolution of arboreal locomotion in this group of rodents. In contrast to those of living anomaluroids, the astragalus of Pondaungimys bears features indicating a less mobile ankle, specifically including a reduced range of plantarflexion at the upper ankle joint and a diminished capacity for inversion at the lower ankle joint. Its anatomy suggests that early anomaluroids were generalized quadrupeds, with intermediate arboreal adaptations between those of paramyids and modern anomaluroids. A cladistic analysis based on astragalar characters corroborates a basal position for Pondaungimys among anomaluroids. The phylogenetic signal derived from astragalar morphology is consistent with recent assessments of relationships among living anomaluroids based on craniodental characters and molecular data. Stem anomaluroids such as Pondaungimys apparently lacked the ability to glide, a locomotor pattern that is retained in extant Zenkerella.

New hominin postcranial remains from locality OMO 323, Shungura Formation, Lower Omo Valley, southwestern Ethiopia

Postcranial bones may provide valuable information about fossil taxa relating to their locomotor habits, manipulative abilities and body sizes. Distinctive features of the postcranial skeleton are sometimes noted in species diagnoses. Although numerous isolated postcranial fossils have become accepted by many workers as belonging to a particular species, it is worthwhile revisiting the evidence for each attribution before including them in comparative samples in relation to the descriptions of new fossils, functional analyses in relation to particular taxa, or in evolutionary contexts. Although some workers eschew the taxonomic attribution of postcranial fossils as being less important (or interesting) than interpreting their functional morphology, it is impossible to consider the evolution of functional anatomy in a taxonomic and phylogenetic vacuum. There are 21 widely recognized hominin taxa that have been described from sites in Africa dated from the Late Miocene to the Middle Pleistocene; postcranial elements have been attributed to 17 of these. The bones that have been thus assigned range from many parts of a skeleton to isolated elements. However, the extent to which postcranial material can be reliably attributed to a specific taxon varies considerably from site to site and species to species, and is often the subject of considerable debate. Here, we review the postcranial remains attributed to African hominin taxa from the Late Miocene to the Middle and Late Pleistocene and place these assignations into categories of reliability. The catalog of attributions presented here may serve as a guide for making taxonomic decisions in the future.

Morphology and structure of Homo erectus humeri from Zhoukoudian, Locality 1.

BackgroundRegional diversity in the morphology of the H. erectus postcranium is not broadly documented, in part, because of the paucity of Asian sites preserving postcranial fossils. Yet, such an understanding of the initial hominin taxon to spread throughout multiple regions of the world is fundamental to documenting the adaptive responses to selective forces operating during this period of human evolution.MethodsThe current study reports the first humeral rigidity and strength properties of East Asian H. erectus and places its diaphyseal robusticity into broader regional and temporal contexts. We estimate true cross-sectional properties of Zhoukoudian Humerus II and quantify new diaphyseal properties of Humerus III using high resolution computed tomography. Comparative data for African H. erectus and Eurasian Late Pleistocene H. sapiens were assembled, and new data were generated from two modern Chinese populations.ResultsDifferences between East Asian and African H. erectus were inconsistently expressed in humeral cortical thickness. In contrast, East Asian H. erectus appears to exhibit greater humeral robusticity compared to African H. erectus when standardizing diaphyseal properties by the product of estimated body mass and humeral length. East Asian H. erectus humeri typically differed less in standardized properties from those of side-matched Late Pleistocene hominins (e.g., Neanderthals and more recent Upper Paleolithic modern humans) than did African H. erectus, and often fell in the lower range of Late Pleistocene humeral rigidity or strength properties.DiscussionQuantitative comparisons indicate that regional variability in humeral midshaft robusticity may characterize H. erectus to a greater extent than presently recognized. This may suggest a temporal difference within H. erectus, or possibly different ecogeographical trends and/or upper limb loading patterns across the taxon. Both discovery and analysis of more adult H. erectus humeri are critical to further evaluating and potentially distinguishing between these possibilities.

First occurrence of Palaeotheriidae (Perissodactyla) from the late–middle Eocene of eastern Thrace (Greece)

A detailed assessment of postcranial fossils collected at Balouk Keui (Thrace, Greece) in the mid-19th Century by the naturalist Auguste Viquesnel enabled us to identify the material as pertaining to Palaeotherium sp., cf. P. magnum, which constitutes the easternmost occurrence of the genus during the Eocene. We have constrained the geographic and stratigraphic provenance of the fossil by reassessing information about Viquesnel's itinerary and observations. Although the exact age of the fossil remains uncertain, the occurrence of a palaeothere in the Thrace Basin during the Eocene indicates a wider geographic distribution for the genus, which had previously been restricted to western and central Europe. The palaeothere of Balouk Keui confirms that the palaeogeographic range of this group included the Balkans during the middle–late Eocene. This discovery also shows that at least intermittent land connections between western Europe, Southeast Asia, and perhaps Central Iran facilitated mammalian dispersal during the middle–late Eocene, before the famous Grande Coupure.

Comparative analysis of trabecular bone structure and orientation in South African hominin tali

Tali of several hominin taxa are preserved in the fossil record and studies of the external morphology of these often show a mosaic of human-like and ape-like features. This has contributed to a growing recognition of variability characterizing locomotor kinematics of Australopithecus. In contrast, locomotor kinematics of another Plio-Pleistocene hominin, Paranthropus, are substantially less well-documented, in part, because of the paucity of postcranial fossils securely attributed to the genus. Since the talus transmits locomotor-based loads through the ankle and its internal structure is hypothesized to reflect accommodation to such loads, it is a cornerstone structure for reconstructing locomotor kinematics. Here we quantify and characterize trabecular bone morphology within tali attributed to Australopithecus africanus (StW 102, StW 363, StW 486) and Paranthropus robustus (TM 1517), making quantitative comparisons to modern humans, extant non-human apes, baboons, and a hominin talus attributed to Paranthropus boisei (KNM-ER 1464). Using high-resolution images of fossil tali (25 μm voxels), nine trabecular bone subregions of interest beneath the articular surface of the talar trochlea were segmented to quantify localized patterns in distribution and primary strut orientation. It was found that trabecular strut orientation and shape, in some cases, can discriminate amongst species characterized by different locomotor foot kinematics. Discriminant function analyses using standard trabecular bone structural properties align TM 1517 with Pan and Gorilla, while other hominin tali structurally most resemble those of baboons. In primary strut orientation, Paranthropus tali (KNM-ER 1464 and TM 1517) resemble the human condition in the anterior-medial subregion, where strut orientation appears positioned to distribute compressive loads medially and distally toward the talar head. In A. africanus tali (particularly StW 486), primary strut orientation in this region resembles that of apes. These results suggest that Paranthropus may have had a human-like medial weight shift during the last half of stance phase but Australopithecus did not.

Anthracotheres from the Oligocene of Aubenas-les-Alpes, France

The Oligocene locality at Aubenas-les-Alpes, France, has yielded an interesting sample of anthracotheres representing two subfamilies, Anthracotheriinae and Bothriodontinae. The large dental remains are attributed to Anthracotherium magnum, the smaller dental and postcranial fossils are attributed to Elomeryx crispus. The phalanges of the latter species are proximo-distally shortened, suggesting a brachypothere-like distal limb morphology, in contrast to the elongated pedal elements that are usually found in anthracotheres. The presence of these two taxa at the site agrees with correlation to MP 25.

The record of camelids (Artiodactyla, Camelidae) from the Valsequillo Basin, late Pleistocene of Puebla State, Central Mexico: taxonomy, diet, and geographic distribution

Dental and postcranial fossil material referable to camelids, which has been recovered from Quaternary deposits that outcrop in the Valsequillo Basin, Puebla State, central Mexico, is formally described. A comparative study indicates the presence of two species of camelids, including Hemiauchenia macrocephala and Camelops hesternus. The sample referable to H. macrocephala includes maxillary and mandibular fragments, isolated teeth, and several postcranial remains (astragalus, metapodials, and proximal phalanges), which show the following diagnostic features of the species: molariforms covered by a layer of cementum; a mandible increasing in depth from p4 to m3; p4 triangular in outline; long and slender metapodials; and proximal phalanges with a W-shaped suspensory ligament scar. The sample referable to C. hesternus is represented by maxillary and mandibular fragments, isolated teeth, and metapodials, sharing with the species its large size; P4 quadrate in outline; p4 triangular in outline and simply folded; and a mandible that is significantly deeper from p4 to m3. A microwear analysis was performed in order to characterize the diet of studied samples, indicating a browser and mixed feeding behavior in H. macrocephala and C. hesternus respectively. The differences in size and trophic regimes in these species should explained the resource partitioning between them. In the late Pleistocene these camelids were common in Mexican sites between the 19°-25° N, and the record from the Valsequillo Basin is one of the few sites where both species have been reported.

Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India.

Cambaytheres (Cambaytherium, Nakusia and Kalitherium) are recently discovered early Eocene placental mammals from the Indo-Pakistan region. They have been assigned to either Perissodactyla (the clade including horses, tapirs and rhinos, which is a member of the superorder Laurasiatheria) or Anthracobunidae, an obscure family that has been variously considered artiodactyls or perissodactyls, but most recently placed at the base of Proboscidea or of Tethytheria (Proboscidea+Sirenia, superorder Afrotheria). Here we report new dental, cranial and postcranial fossils of Cambaytherium, from the Cambay Shale Formation, Gujarat, India (~54.5 Myr). These fossils demonstrate that cambaytheres occupy a pivotal position as the sister taxon of Perissodactyla, thereby providing insight on the phylogenetic and biogeographic origin of Perissodactyla. The presence of the sister group of perissodactyls in western India near or before the time of collision suggests that Perissodactyla may have originated on the Indian Plate during its final drift toward Asia.

Mammalian femora across the Cretaceous–Paleogene boundary in eastern Montana

Our understanding of latest Cretaceous and earliest Paleogene mammalian evolution is based almost entirely on the dental fossil record. Mammalian postcranial fossils are rare and mostly found as isolated elements in latest Cretaceous and earliest Paleogene vertebrate microfossil assemblages of North America. Although placing these fossils in a tooth-based taxonomic framework is difficult, they can provide insight into locomotor diversity and habitat preference to complement diet reconstructions and diversity estimates from dental fossils. Here, we describe 64 femora of mammals recovered from latest Cretaceous (Lancian) and earliest Paleogene (Puercan) localities in eastern Montana. We sorted these based on morphology and size (morphotypes). In some cases, morphotypes were tentatively assigned to dentally based taxa that are known from these strata.Although our resulting femoral dataset is small relative to the study area's dental dataset, we show several key findings. First, there is a greater morphological diversity of multituberculate femora than previously recognized, especially in the latest Cretaceous sample. In contrast, metatherians, which have a high relative abundance in Lancian Hell Creek Formation dental assemblages, are absent from our postcranial samples; eutherian femora are only present in the Puercan assemblages. Second, we record a minor decrease in morphotype richness across the K–Pg boundary that is associated with an increase in mean specimen size, due to the appearance of a few significantly larger-bodied, immigrant taxa. Among the eutherians, there are two specimens of larger-bodied early Puercan archaic ungulates, a very large specimen of a middle/late Puercan taeniodont, pantodont, or triisodontid, as well as a specimen possibly attributed to a “plesiadapiform” archaic primate. Third, preliminary functional morphologic analyses of the more complete specimens suggest that locomotor diversity increased from mainly arboreal or terrestrial/saltatorial multituberculates in the latest Cretaceous to include a fossorial multituberculate and potentially an arboreal eutherian in the early Paleocene. These patterns parallel those previously reported from a dental dataset and indicate that postcranial data are valuable as an independent means to test hypotheses of taxonomic and ecomorphological diversity across the K–Pg boundary.

Cercopithecoid primate postcranial fossils from Cooper's D, South Africa

Among several highly fossiliferous localities in the Bloubank Valley (Gauteng, South Africa), the Cooper's Cave System has been known since 1938 and has produced a rich fossil assemblage, including some remains of the early hominin Paranthropus robustus. In 2001, excavations began at a new locality, Cooper's D, which dates to ∼1.4-1.5Ma. Although hominins are relatively rare in the assemblage, remains of cercopithecoid primates are much more common. Craniodental fossils currently indicate the possible presence of at least three large-bodied cercopithecoid primate genera at Cooper's D: Gorgopithecus, Papio, and Theropithecus. In this study, we identify and describe >100 cercopithecoid primate postcranial fossils representing all regions of the appendicular skeleton. The specimens come from several age classes and size morphs; more than one third of the fossils described are from sub-adult and juvenile individuals. The adult postcranial fossils vary substantially in size, with body masses estimated between 30 and 60kg (from 16 of the better preserved specimens). The functional morphology of the postcranial remains indicate that these elements come from animals that likely utilized terrestrial substrates, but they remain difficult to definitively attribute to Gorgopithecus, Theropithecus, or Papio given the absence of associated skeletons. The smaller specimens likely belong to Papio while the larger ones can be attributed to the other two genera. Because Cooper's D has also yielded fossils of the early hominin Paranthropus robustus, this raises the question of how these four large-bodied, mostly terrestrial primates sympatrically utilized the landscape.

Hominin stature, body mass, and walking speed estimates based on 1.5 million-year-old fossil footprints at Ileret, Kenya

The early Pleistocene marks a period of major transition in hominin body form, including increases in body mass and stature relative to earlier hominins. However, because complete postcranial fossils with reliable taxonomic attributions are rare, efforts to estimate hominin mass and stature are complicated by the frequent albeit necessary use of isolated, and often fragmentary, skeletal elements. The recent discovery of 1.52 million year old hominin footprints from multiple horizons in Ileret, Kenya, provides new data on the complete foot size of early Pleistocene hominins as well as stride lengths and other characteristics of their gaits. This study reports the results of controlled experiments with habitually unshod Daasanach adults from Ileret to examine the relationships between stride length and speed, and also those between footprint size, body mass, and stature. Based on significant relationships among these variables, we estimate travel speeds ranging between 0.45 m/s and 2.2 m/s from the fossil hominin footprint trails at Ileret. The fossil footprints of seven individuals show evidence of heavy (mean = 50.0 kg; range: 41.5–60.3 kg) and tall individuals (mean = 169.5 cm; range: 152.6–185.8 cm), suggesting that these prints were most likely made by Homo erectus and/or male Paranthropus boisei. The large sizes of these footprints provide strong evidence that hominin body size increased during the early Pleistocene.