La phalange distale du pouce d’Orrorin tugenensis (Miocène supérieur du Kenya)

The lion's share of articles dealing with the thumb anatomy of Plio-Pleistocene hominids has focussed on the capacity to manipulate and manufacture tools, and has largely neglected the locomotor aspects. However, in these hominids, the forelimb was still employed in locomotion. Certain of the anatomical characters classically associated with manipulation and/or fabrication of tools are already present in the Late Miocene species Orrorin tugenensis as shown by the terminal thumb phalanx BAR 1901'01. This specimen reveals crucial information suggesting that thumb morphology is not exclusively related to such tool using and manufacturing activities but reflects in a frequently bipedal creature a deeper adaptation concerning the precision grip essential for climbing and balancing, different from that of apes.     

Rudabánya: A late miocene subtropical swamp deposit with evidence of the origin of the African apes and humans

Rudabánya, a rich late Miocene fossil site in northern central Hungary, has yielded an abundant record of fossil primates, including the primitive catarrhine Anapithecus and the early great ape Dryopithecus. While the affinities of Anapithecus are not clear, Dryopithecus is clearly a great ape sharing numerous characteristics of its dental, cranial and postcranial anatomy with living great apes. Like all Miocene hominids (great apes and humans), Dryopithecus is more primitive in a number of ways than any living hominid, which is probably related to the passage of time since the divergence of the various lineages of living hominids, allowing for similar refinements in morphology and adaptation to take place independently. On the other hand, Dryopithecus (and Ouranopithecus) share derived characters with hominines (African apes and humans), and Sivapithecus (and Ankarapithecus) share derived characters with orangutans, thus dating the split between pongines and hominines to a time before the evolution of these fossil great apes. Pongines and hominines follow similar fates in the late Miocene, the pongines moving south into Southeast Asia from southern or eastern Asia and the hominines moving south into East Africa from the Mediterranean region, between 6 to 9 Ma.     

Palaeoenvironments and hominoid evolution

One of the key features that separates humans and their closest relatives (extinct species of the genus Homo and Praeanthropus and the australopithecines Australopithecus and Paranthropus) on the one hand, from the other hominoids, on the other, is their obligate bipedal locomotion when on the ground. This major difference from the generally quadrupedal locomotion practiced by other hominoids (Pan, Gorilla, Pongo and many extinct lineages) is reflected in many parts of the body, including all the major bones in the legs, arms, trunk and cranium. Locomotion has thus been of major interest to those interested in human origins, evolution, classification and phylogeny. A major hurdle to studies of the origins of bipedalism concerns the paucity of African hominoid fossils between 15 Ma, when all the adequately known hominoids were quadrupedal (most were pronograde, but at least one lineage was orthograde), and 4.2 Ma by which time fully bipedal hominids were established in Africa. Examination of Old World geology and palaeontology reveals a great deal about the evolution of palaeoenvironments and faunas during this period, and it is suggested that hominids evolved bipedal locomotion at the same time that there was a fundamental reorganisation of faunas towards the end of the Miocene. This faunal turnover resulted in the establishment of faunal lineages of "modern" aspect in Africa at the expense of "archaic" lineages which either went extinct or suffered a diminution of diversity. Many of the "modern" lineages were adapted to open country habitats in which grass became a major component of the diet as shown by modifications in the cheek teeth. Hominoids, in contrast, retained their traditional diet but were obliged to forage over greater and greater areas in order to do so, and this tactic led to pressures to modify the locomotor system rather than the diet. If bipedal hominids originated during this period, then the family Hominidae (sensu stricto) dates from about 8-7 Ma.     

Evolution of the second orangutan: phylogeny and biogeography of hominid origins

Aim To resolve the phylogeny of humans and their fossil relatives (collectively, hominids), orangutans (Pongo) and various Miocene great apes and to present a biogeographical model for their differentiation in space and time. Location Africa, northern Mediterranean, Asia. Methods Maximum parsimony analysis was used to assess phylogenetic relationships among living large‐bodied hominoids (= humans, chimpanzees, bonobos, gorillas, orangutans), and various related African, Asian and European ape fossils. Biogeographical characteristics were analysed for vicariant replacement, main massings and nodes. A geomorphological correlation was identified for a clade we refer to as the ‘dental hominoids’, and this correlation was used to reconstruct their historical geography. Results Our analyses support the following hypotheses: (1) the living large‐bodied hominoids represent a monophyletic group comprising two sister clades: humans + orangutans, and chimpanzees (including bonobos) + gorillas (collectively, the African apes); and (2) the human–orangutan clade (dental hominoids) includes fossil hominids (Homo, australopiths, Orrorin) and the Miocene‐age apes Hispanopithecus, Ouranopithecus, Ankarapithecus, Sivapithecus, Lufengpithecus, Khoratpithecus and Gigantopithecus (also Plio‐Pleistocene of eastern Asia). We also demonstrate that the distributions of living and fossil genera are largely vicariant, with nodes of geographical overlap or proximity between Gigantopithecus and Sivapithecus in Central Asia, and between Pongo, Gigantopithecus, Lufengpithecus and Khoratpithecus in East Asia. The main massing is represented by five genera and eight species in East Asia. The dental hominoid track is spatially correlated with the East African Rift System (EARS) and the Tethys Orogenic Collage (TOC). Main conclusions Humans and orangutans share a common ancestor that excludes the extant African apes. Molecular analyses are compromised by phenetic procedures such as alignment and are probably based on primitive retentions. We infer that the human–orangutan common ancestor had established a widespread distribution by at least 13 Ma. Vicariant differentiation resulted in the ancestors of hominids in East Africa and various primarily Miocene apes distributed between Spain and Southeast Asia (and possibly also parts of East Africa). The geographical disjunction between early hominids and Asian Pongo is attributed to local extinctions between Europe and Central Asia. The EARS and TOC correlations suggest that these geomorphological features mediated establishment of the ancestral range.     

Longgupo: EarlyHomo colonizer or late plioceneLufengpithecus survivor in south China?

A fragment of mandible and a maxillary incisor of different individuals from the Longgupo Cave, China have been cited as evidence of an early dispersal ofHomo from Africa to Asia. More specifically, these specimens are said to resemble “Homo ergaster” orHomo habilis, rather than the species usually thought to be the first Asian colonizer,Homo erectus. If this supposition is correct, it calls into question which hominid (sensu stricto) first left Africa, and why hominids became a colonizing species. Furthermore, the Longgupo remains have been used to buttress the argument thatHomo erectus evolved uniquely in Asia and was not involved in the origins of modern humans. We question this whole line of argument because the mandibular fragment cannot be distinguished from penecontemporary fossil apes, especially the Late Miocene-Pliocene Chinese genusLufengpithecus, while the incisor is indistinguishable from those of recent and living east Asian people and may be intrusive in the deposit. We believe that the Longgupo mandible represents the relic survival of a Late Miocene ape lineage into a period just prior to the dispersal of hominids into southeastern Asia, with some female dental features that parallel the hominid condition. If the Longgupo mandibular fragment represents a member of theLufengpithecus clade, it demonstrates that hominoids other thanGigantopithecus and the direct ancestor of the orangutan persisted in east Asia into the Late Pliocene, while all other Eurasian large-bodied hominoids disappeared in the Late Miocene.     

Miocene snakes from northeastern Kazakhstan: new data on the evolution of snake assemblages in Siberia

Abstract

The Neogene snake fauna from the central and eastern regions of Eurasia is still largely unknown. This paper reports on a unique snake fauna from the late middle Miocene of the Baikadam and Malyi Kalkaman 1 and 2 localities, northeastern Kazakhstan, which represents the best-documented Miocene snake assemblage in Central Asia. Previous studies admitted that snake fauna could be homogeneous over a large part of Eurasia during the Miocene, with the late middle to early late Miocene assemblages similar to snake assemblages that inhabited Europe in the late early and early middle Miocene. This assumption is partially supported by the presence of Texasophis bohemiacus and Coluber cf. hungaricus, as well as vipers of the ‘V. aspis’ complex. However, the presence of taxa which are (1) probably not related to European representatives (‘Colubrinae’ A and B), (2) probably never occurred in Central and Western Europe and (3) are closely related to species recently inhabiting southern Siberia (Elaphe aff. dione, Gloydius sp.) indicates that faunal dissimilarity was relatively high within Eurasia during the late middle Miocene. This assumption is in accordance with studies of small mammal assemblages which show a decreasing homogenity in the Eurasia in the course of the middle Miocene.     

The distal femoral anatomy of Australopithecus

The anatomy of the distal femoral fragments from Sterkfontein is reviewed, including its orthopaedic and biomechanical implications with respect to locomotion pattern. Comparisons are made with other hominids and a number of quadrupedal primates. Items which are considered are the obliquity and robustness of the shaft, the anterior intercondylar groove, the intercondylar notch, and the contour of the medial and lateral articular surfaces. The distinctive hominid status of these specimens is shown by their extensive adaptation to bipedal locomotion. No feature is found which is not fully commensurate with completely bipedal locomotion; rather, their distinctive hominid character points to a need for a reanalysis of the gait pattern in these early Pleistocene hominids.     

The environmental background of hominid emergence and the appearance of the genusHomo

The human biologist usually considers ecology of recent humanity. This essay explores the question of whether the human biologist specialising in the ecology of living peoples has anything to learn from the palaeo-anthropologist, studying ancient hominids andtheir adaptive mechanisms over a deep time dimension. Since the Hominidae are under discussion, the definition of the hominids is reviewed. Historically, three phases are recognised. A rethinking of the classification of the hominoids has become necessary for the old and classical systematics, which divided this superfamily into the Hominidae and the Pongidae, is now outmoded. Since no consensus on such a re-classification has yet been reached, the author adheres to the classical system for the time being. The Hominidae emerged between about 8 and 5 million years ago. At that time, Africa was subject to major cooling and aridification and considerable changes in the flora and fauna were occurring. Wet forests were retreating, savanna was spreading and the animals of Africa were undergoing many changes, partly by faunal interchange with Asia following the drying up of the Mediterranean, and partly by autochthonous evolution among the pre-existing species of the continent. The Hominidae could well have emerged from the striking environmental modifications of this late Miocene phase. Critical changes occurred in hominid evolution between 3 and 2 million years before the present. The pre-existing speciesAustralopithecus africanus acquired the form of a postulated derivedA. africanus; the hominid lineage underwent cladogenetic splitting into robust and hyper-robust australopithecines and the genusHomo; Homo babilis appeared; stone tools are first found in the archaeological record; spoken language seems to have been acquired. These sensational events, within the space of one million years, took place against the background of conspicuous changes in the climate and physical geography of Africa, the flora and non-hominid fauna. Mankind became increasingly dependent upon stone culture. Hence a new element was added to the range of modes of adjustment, an element which must have greatly increased the ecological flexibility of the hominids. From the end of the Pliocene era onwards, culture should be seen as a constituent of man's environment and, at the same time, a highly advantageous component of human adaptational processes. In later and recent mankind, it may be difficult to extricate the respective roles of biological, social and physical factors, on the one hand, and cultural aspects on the other, as mechanisms and facilitators of adaptation to diverse econiches.     

Australopithecus afarensis : bipédie stricte ou associée à une composante arboricole ? Critiques et révision du matériel fémoral

Although much research has been carried out on Australopithecus afarensis locomotion, no consensus has yet been reached. Our new critic study on femoral material brings to the fore a strictly bipedal behaviour within this taxon. Our results are based on the pertinence of human anatomical characteristics among A. afarensis and on the absence of characteristics revealing arboreal displacement. These results have emerged from our different observation and interpretation of some preceding authors concerning the anatomy of these fossil hominids. It is important to underline that apomorphic characteristics of this species are difficult to interpret. They must not however be used to support the idea of arboreal displacement simply based on the fact of a no totally human morphe. We believe that present day humans do not necessarily reflect the earliest strict bipedal anatomic model. An the other hand, it appears that the disagreement between the two locomotor hypothesis for A. afarensis that are bipedalism and arboreal displacement, facing the possibility of bipedalism associated with negligible arboreal displacement, results more from an evolutionary fact than from a real scientific conflict.     

Our ancestors' ancestor: Ouranopithecus is a greek link in human ancestry

Recent discoveries of the late Miocene hominoid Ouranopithecus shed new light on the evolution of hominids. These discoveries result from the strategy of the Allied armies during the First World War. In the midst of “the war to end all wars,” the North African soldiers of Camille Arambourg excavated the first mammalian fossils found in northern Greece, in the region of Macedonia, the country of Alexander the Great. On the tracks of these strange paleontological pioneers, a modern French and Greek team has unearthed a large hominoid primate, a missing link between fossilapes and primitive Australopithecus, which lived in southeastern Europe 9 to 10 million years ago. A reconstruction of Ouranopithecus and its surroundings gives us a rare glimpse into the world of the earliest hominids.     

Phylogeny, evolutionary history and taxonomy of the Mustelidae based on sequences of the cytochrome b gene and a complex repetitive flanking region

The Mustelidae is a diverse family of carnivores which includes weasels, polecats, mink, tayra, martens, otters, badgers and, according to some authors, skunks. Evolutionary relationships within the family are under debate at a number of different taxonomic levels, and incongruencies between molecular and morphological results are important. We analysed a total of 241 cytochrome b (cyt b) gene sequences and 33 sequences of a complex repetitive flanking region from 33 different species to compile an extensive molecular phylogeny for the Mustelidae. We analysed these sequences and constructed phylogenetic trees using Bayesian and neighbor‐joining methods that are evaluated to propose changes to the taxonomy of the family. The peripheral position of skunks in phylogenetic trees based on both loci suggests that they should be considered a separate family, Mephitidae. The subfamily Melinae is the basal group within the Mustelidae and trees based on the cyt b gene suggest that the American badger, Taxidea taxus, should be considered a separate monotypic subfamily, Taxidiinae. Otters classified within the genera Lutra, Amblonyx and Aonyx are grouped within the same clade in cyt b and combined partial cyt b and flanking region trees and show reduced levels of inter specific divergence, suggesting that they could be classified together under a single genus, Lutra. The Bayesian tree based on combined data from both loci supports the idea that subfamily Mustelinae is paraphyletic, as otters (subfamily Lutrinae) are included in this subfamily. Low levels of genetic divergence among European polecat, Mustela putorius, steppe polecat, Mustela eversmannii, and European mink, Mustela lutreola, suggest that these species could be considered subspecies within a single species, Mustela putorius. Our results are consistent with a rapid diversification of mustelid lineages in six different radiation episodes identified since the Early Eocene, the oldest events being the separation of subfamilies and the split of marten (Martes, Gulo) and weasel (Mustela) lineages in the Early Middle Miocene. The separation of New World from Old World lineages and the split of the remaining genera are estimated to have occurred in Late Miocene. The most recent events have been the differentiation of species within genera and this probably occurred in four radiation episodes at the end of Late Miocene, Early Pliocene, Late Pliocene and Pleistocene epochs.     

Cross-sectional geometric properties of the Otavipithecus mandible

Cross-sectional geometric properties of the postcanine mandibular corpus are determined for the only known specimen of Otavipithecus namibiensis, a middle Miocene hominoid from southern Africa. It is shown that Otavipithecus is unique in that several important mechanical properties of its mandible, including maximum and minimum moments of inertia and distribution of cortical bone, differ from patterns seen in both extant hominoids and the early hominids Australopithecus africanus and Australopithecus (Paranthropus) robustus. This is particularly apparent in the mechanical design of the posterior portion of the mandibular corpus for resisting increased torsional and transverse bending moments. Cortical index values at the level of M₂ also reveal that both Otavipithecus and A. africanus are similarly designed to resist increased masticatory loads with relatively less cortical bone area, a highly efficient mechanical design. © 1996 Wiley-Liss, Inc.     

Sivapithecus simonsi,a new species of miocene hominoid,with comments on the phylogenetic status of the ramapithecinae

The Ramapithecinae are an extinct, mainly Miocene group of hominoids, whose relationship to modern taxa is disputed. Some regard them as hominids, while others view them as ancestral toPongo,or even as the group ancestral to both hominids and extant apes. In this paper a systematic revision of Ramapithecinae is undertaken. Sivapithecus sivalensis andRamapithecus punjabicus are considered the same species, with the former name having priority. A new Indian species,Sivapithecus simonsi,is recognized. Ramapithecine anatomy is reviewed and compared with that of gracileAustralopithecus, early and middle MioceneProconsul andDryopithecus, and living pongidsPan, Gorilla, andPongo.Ramapithecines are shown to be much more primitive or “ape-like” than some have argued. Anatomical data are evaluated cladistically with several results. Parallel evolution in the jaws, teeth, and facial structure of hominoids appears to be the rule rather than the exception. Bearing this in mind, nevertheless, from the available evidence of anatomy, ramapithecines are cladistically hominids.     

The adoption of bipedalism by the hominids: A new hypothesis

The hypothesis is advanced that the habitual adoption of the bipedal stance and of bipedal locomotion in the hominids arose from the development of a defence mechanism, namely, the throwing of stones. It is argued that for stone-throwing to become an effective weapon, modifications to the whole post-cranial skeleton and musculature, as well as to the central nervous system are required; including the development of a low centre of gravity and a «launching platform» of relatively high mass. It is represented that hominids, from the earliest Australopithecines to modern man, exhibit modifications to the post-cranial structures that are more consonant with this hypothesis than with the interpretation that the modifications were directed initially and principally towards bipedalism. Such an interpretation is shown to create several anomalies which disappear when viewed in the context of the stated hypothesis. The importance of the hypothesis for the evolution of Homo and especially for his brain and higher thought processes is commented upon.     

First partial face and upper dentition of the Middle Miocene hominoid Dryopithecus fontani from Abocador de Can Mata (Vallès‐Penedès Basin,Catalonia, NE Spain): Taxonomic and phylogenetic implications

A well‐preserved 11.8‐million‐years‐old lower face attributed to the seminal taxon Dryopithecus fontani (Primates, Hominidae) from the Catalan site ACM/C3‐Ae of the Hostalets de Pierola area (Vallès‐Penedès Basin, Catalonia, NE Spain) is described. The new data indicate that D. fontani is distinct at the genus level from Late Miocene European taxa previously attributed to Dryopithecus, which are here reassigned to Hispanopithecus. The new facial specimen also suggests that D. fontani and the Middle Miocene Pierolapithecus catalaunicus are not synonymous. Anatomical and morphometric analyses further indicate that the new specimen shows a combination of lower facial features—hitherto unknown in Miocene hominoids—that resembles the facial pattern of Gorilla, thus providing the first nondental evidence of gorilla‐like lower facial morphology in the fossil record. Considering the current evidence, the gorilla‐like facial pattern of D. fontani is inferred to be derived relative to previously known stem hominids, and might indicate that this taxon is either an early member of the Homininae or, alternatively, a stem hominid convergent with the lower facial pattern of Gorilla. The biogeographic implications of both alternatives are discussed. This new finding in the Hostalets de Pierola section reinforces the importance of this area for understanding the elusive question of the Middle Miocene origin and early radiation of great apes. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Uplift of the roof of africa and its bearing on the evolution of mankind

Evidence concerning the geomorphological evolution of the Western Rift Valley, sedimentation within the valley and comparison of the fossil mammalian faunas of Western Uganda and East Africa indicate that the mountain ranges which now flank the Western Rift were uplifted in three or more stages beginning during the upper Miocene and that they reached climatically important altitudes during the upper Pliocene, at which time they began to modify regional climatic patterns in East Africa. Their main effect was the xerification of conditions over much of the region east of the mountains. The regional climatic effects due to the mountain ranges were themselves modified by global climatic changes related to the onset of the Glacial Period, the two phenomena combining to yield the Present day climatic regime of East Africa. As the climate changed, so did the flora and fauna. Faunal response was of three main kinds: a) dispersal into East Africa of pre-existing forms already adapted to more xeric conditions (many bovids, some cercopithecids), b) autochthonous evolution of forms adapted to mesic environments into forms adapted to more xeric conditions (suids, elephantids, some bovids, hominids), c) displacement of species ranges of those lineages unable to adapt to changing conditions (i.e. local extinctions) (Anancus, Brachypotherium). Autochthonous evolvers, including hominids, adopted two main strategies reflected in their hard anatomy: a) dietary shift (suids, proboscideans, bovids and later Pliocene hominids) and b) locomotor changes (early Pliocene hominids).     

Fossil pollen grains of Asteraceae from the Miocene of Patagonia: Nassauviinae affinity

Fossil pollen grains with morphological features unique in the subtribe Nassauviinae (tribe Mutisieae, Asteraceae) occur in Miocene marine deposits of eastern Patagonia, southern South America. A new morphogenus and two morphospecies are proposed to assemble fossil pollen grains characterized by having a complex bilayered exine structure with delicate columellae, separated by an internal tectum. Subprolate specimens with Trixis exine type (ectosexine thinner than endosexine, straight internal tectum) are referred to Huanilipollis cabrerae. This species is similar to pollen of recent Holocheilus, Jungia, and Proustia. Suboblate specimens with Oxyphyllum exine type (ectosexine and endosexine equally thick, zigzag internal tectum) are referred to Huanilipollis criscii. This species is similar to pollen of recent Triptilion. The spore/pollen sequences in which Nassauviinae pollen types occur suggest a wide range of vegetation types varying from forest dominated during the Early Miocene (Chenque Formation) to virtually xerophytic ones during the Late Miocene (Puerto Madryn Formation). The subtribe Nassauviinae comprises 25 genera and ca. 320 species of vines, shrubs and low trees endemic to America with a wide range of ecological preferences; the nearest living relatives of the fossil types being mostly confined to humid landscapes. The unusual occurrence of these groups during the arid characterized Late Miocene time could be attributed to the complex interplay of the mountain uplift and global circulation patterns. These forcing factors would have created a mosaic of different habitats with both patches of forest and dry-adapted species developing in relatively small regions. This is the first fossil record of Nassauviinae and confirms that this subtribe of Asteraceae was already differentiated in the Miocene.     

Geopalaeontological setting,chronology and palaeoenvironmental evolution of the Baccinello-Cinigiano Basin continental successions (Late Miocene,Italy)

The Latest Miocene succession of the Baccinello-Cinigiano Basin in southern Tuscany (Italy) recorded a faunal turnover documenting the extinction of an older, insular, endemic faunal complex characterised by the extinct ape Oreopithecus bambolii and the setting of a new, continental, European faunal complex including the colobine monkey Mesopithecus. A similar turnover pattern (Late Miocene ape/Latest Miocene Cercopithecidae) is generally observed in Late Miocene continental successions of Eurasia, from Spain to central Europe, Southwest Europe, the near East, and Southwest Asia. Abundant literature reports that the Late Miocene Eurasian hominoid primate distribution closely tracks the climatic/environmental changes occurring during the 12–9 Ma interval, until their extinction in western Europe. In the primate record, the dispersion of Cercopithecidae and the contraction of hominids is interpreted as an event depicting a pattern of “continentalisation” in the Old World. The sedimentary succession of the Baccinello-Cinigiano basin, one of the longest continuous vertebrate-bearing continental successions in the Neogene Italian record, contributes to the debate on this hypothesis. This paper provides an overview of the main characteristics of the sedimentary succession, the chronological constraints (biochronology, radiometric datings, magnetostratigraphy), and the palaeoenvironmental evolution as derived from palaeobiological approaches and from the study of stable carbon and oxygen isotope contents along the entire sedimentary succession. The 2 myr geological history of the Baccinello Cinigiano Basin, which documents the evolutionary history of Oreopithecus and associated faunas, does not have a direct relation with the event of the Messinian Salinity Crisis. The evolutionary history of Baccinello-Cinigiano Basin and its palaeontological record have been mainly driven by the regional tectonism and palaeogeographic changes that affected the northern Tyrrhenian regions in Late Miocene (Latest Tortonian–Messinian) times.     

Positional behavior and substrate use in wild adult bearded capuchin monkeys (Sapajus libidinosus)

Natural selection for positional behavior (posture and locomotion) has at least partially driven the evolution of anatomical form and function in the order Primates. Examination of bipedal behaviors associated with daily activity patterns, foraging, and terrestrial habitat use in nonhuman primates, particularly those that adopt bipedal postures and use bipedal locomotion, allows us to refine hypotheses concerning the evolution of bipedalism in humans. This study describes the positional behavior of wild bearded capuchins (Sapajus libidinosus), a species that is known for its use of terrestrial substrates and its habitual use of stones as tools. Here, we test the association of terrestrial substrate use with bipedal posture and locomotion, and the influence of sex (which co‐varies with body mass in adults of this species) on positional behavior and substrate use. Behavior and location of 16 wild adult bearded capuchins from two groups were sampled systematically at 15 s intervals for 2 min periods for 1 year (10,244 samples). Despite their different body masses, adult males (average 3.5 kg) and females (average 2.1 kg) in this study did not differ substantially in their positional behaviors, postures, or use of substrates for particular activities. The monkeys used terrestrial substrates in 27% of samples. Bipedal postures and behaviors, while not a prominent feature of their behavior, occurred in different forms on the two substrates. The monkeys crouched bipedally in trees, but did not use other bipedal postures in trees. While on terrestrial substrates, they also crouched bipedally but occasionally stood upright and moved bipedally with orthograde posture. Bearded capuchin monkeys' behavior supports the suggestion from anatomical analysis that S. libidinosus is morphologically better adapted than its congeners to adopt orthograde postures.     

The arboreal leaping theory of the origin of pterosaur flight

Three theories about the origin of flight in pterosaurs have been proposed: 1) the arboreal parachuting theory (passive falling from trees leading to gliding and eventually to powered flight); 2) the cursorial theory (bipedal running and leaping leading directly to powered flight); and 3) the arboreal leaping theory (active leaping between branches and trees leading to powered flight). The available evidence as to the functional morphology of pterosaurs, and in particular their hindlimb, is reviewed and used to test the three theories. Pterosaurs were well suited for arboreality and their hindlimb morphology argues against cursoriality, but supports an arboreal leaping lifestyle for early pterosaurs or their immediate ancestors.