New hand bones of Hadropithecus stenognathus: implications for the paleobiology of the Archaeolemuridae

A partial, associated skeleton of Hadropithecus stenognathus (AHA-I) was discovered in 2003 at Andrahomana Cave in southeastern Madagascar. Among the postcranial elements found were the first hand bones (right scaphoid, right hamate, left first metacarpal, and right and left fifth metacarpals) attributed to this rare subfossil lemur. These hand bones were compared to those of extant strepsirrhines and catarrhines in order to infer the positional adaptations of Hadropithecus, and they were compared to those of Archaeolemur in order to assess variation in hand morphology among archaeolemurids. The scaphoid tubercle does not project palmarly as in suspensory and climbing taxa, and the hamate has no hook at all (just a small tubercle), which also points to a poorly developed carpal tunnel. There is a distinctive, radioulnarly directed "spiral" facet for articulation with the triquetrum that is most similar in orientation to that of more terrestrial primates (i.e., Lemur catta, Papio, and Gorilla). The first metacarpal is very reduced and represents only 48% of the length of metacarpal V, as in Archaeolemur, which suggests that pollical grasping of arboreal supports was not important. Compared to Archaeolemur, the shaft of metacarpal V is gracile, and the head has no dorsal ridge and lacks characteristics functionally associated with digitigrade, extended metacarpophalangeal joint postures. Proximally, the articular facet for the hamate is oriented more dorsally. Thus, the carpometacarpal joint V appears to have a distinctive hyperextended set, which has no analog among living or extinct primates. The carpals of Hadropithecus are diagnostic of a pronograde, arboreal and terrestrial (although not digitigrade) locomotor repertoire that typifies Lemur catta and some Old World monkeys. No clinging, suspensory, or climbing specializations that characterize indriids or lorises can be found in the hand of this subfossil lemur. The hand of Hadropithecus likely had similar ranges of movement at the radiocarpal and midcarpal joints as of those of pronograde primates, such as lemurids, for which the hand is held in a more extended, pronated, and neutral (i.e., showing less ulnar deviation) position during locomotion in comparison to that of vertical clingers or slow climbers. Although highly autapomorphic, the hand of Hadropithecus resembles that of its sister taxon, Archaeolemur, in having a very reduced pollex and an articular facet on the scaphoid for a sizeable prepollex. These unusual hand features reinforce the monophyly of the Archaeolemuridae.     

New primate carpal bones from Rudabánya (late Miocene, Hungary): taxonomic and functional implications

We describe a scaphoid and two capitates from the late Miocene site of Rudabánya, Hungary using qualitative and quantitative comparisons to a large sample of hominoid, cercopithecoid, and platyrrhine primates. The scaphoid (RUD 202) is not fused to the os centrale and in this way is like most primates other than African apes and humans (hominines). Qualitatively, its morphology is most similar to Pongo, and univariate analyses generally confirm an ape-like morphology with an increased range of mobility. One capitate (RUD 167) is compatible in size to the scaphoid, and its morphology suggests a combination of monkey-like generalized arboreality and ape-like enhanced mobility. RUD 203 is a smaller, fragmentary capitate, about half the size of RUD 167, and preserves only the distal portion of the body with the third metacarpal articular surface. Its morphology is virtually identical to that of RUD 167, and an exact randomization test revealed that it is statistically likely to find two carpal bones of such disparate sizes within one taxon. However, due to morphological similarities with other Miocene hominoids as well as implications for size variation within one taxon and sex, we consider the taxonomic affiliation of RUD 203 to be unresolved. We attribute the scaphoid and RUD 167 capitate to the hominine Rudapithecus hungaricus (formerly Dryopithecus brancoi; see Begun et al., 2008) based on overall morphological similarity to extant apes, particularly Pongo, and not to the pliopithecoid Anapithecus hernyaki, the only other primate known from Rudabánya. The similarities in carpal morphology to suspensory taxa are consistent with previous interpretations of Rudapithecus positional behavior. The scaphoid and the RUD 167 capitate are consistent in size with a partial skeleton including associated postcranial and craniodental specimens from the same level at the locality and may be from the same individual. These are the first carpal bones described from Rudabánya and from this taxon, and they add to our understanding of the evolution of arboreal locomotion in late Miocene apes.     

Cranial Morphology of a Pantolestid Eutherian Mammal from the Eocene Bridger Formation,Wyoming, USA: Implications for Relationships and Habitat

Pantolestinae is a eutherian subfamily of mammals whose members are known from the middle early Paleocene through at least the beginning of the Oligocene of North America. They are also known from Europe, and possibly Africa. A lack of information on pantolestine skulls has prevented the use of cranial anatomy in evaluation of this group’s enigmatic higher-level phylogenetic relationships. Conversely, postcranial skeletons are well known and locomotor interpretations based on them are robust. The most complete known skull of a pantolestine, Pantolestes longicaudus (YPM 13525), is described here and compared to potential close fossil relatives and extant mammals. Semicircular canal morphology is used to test locomotor hypotheses. YPM 13525 lacks an ossified bulla. It has a mediolaterally broad basioccipital, a large entoglenoid process, and a deeply incised glaserian fissure of the squamosal, caudal and rostral tympanic processes on the petrosal, a foramen for an internal carotid artery (ICA) that entered the tympanic cavity from a posteromedial position, bony tubes enclosing the main stem and transpromontorial branch of the ICA, a large anterior carotid foramen formed within the basisphenoid, evidence of a stapedial artery ramus superior, a groove on the dorsal aspect of the basisphenoid leading to the piriform fenestra possibly for drainage of the cavernous sinus to an extracranial inferior petrosal sinus, a dorsum sellae with well-developed posterior clinoid processes, a foramen rotundum within the alisphenoid, and a sphenorbital fissure between the alisphenoid and orbitosphenoid. Overall, the morphology is not strikingly similar to any potential close relative and the phylogenetic position of Pantolestinae cannot be estimated without cladistic analysis of a character matrix that includes this new morphology and broadly samples extant and extinct eutherian taxa. Semicircular canal morphology differs from that of two likely terrestrial Paleocene mammals, Aphronorus (another pantolestid) and Eoryctes (a palaeoryctid), suggesting a different, possibly semi-aquatic, lifestyle for Pantolestes.     

New wrist bones of the Malagasy giant subfossil lemurs

Recently discovered wrist bones of the Malagasy subfossil lemurs Babakotia radofilai, Palaeopropithecus ingens, Mesopropithecus dolichobrachion, and Megaladapis madagascariensis shed new light on the postcranial morphologies and positional behaviors that characterized these extinct primates. Wrist bones of P. ingens resemble those of certain modern hominoids in having a relatively enlarged ulnar head and dorsally extended articular surface on the hamate, features related to a large range of rotation at the inferior radioulnar and midcarpal joints. The scaphoid of P. ingens is also similar to that of the extant tree sloth Choloepus in having an elongate, palmarly directed tubercle forming a deep radial margin of the carpal tunnel for the passage of large digital flexors. In contrast, wrist remains of Megaladapis edwardsi and M. madagascariensis exhibit traits observed in the hands of extant pronograde, arboreal primates; these include a dorsopalmarly expanded pisiform and well-developed "spiral" facet on the hamate. Moreover, Megaladapis spp. and Mesopropithecus dolichobrachion possess bony tubercles (e.g., scaphoid tubercle and hamate hamulus) forming the carpal tunnel that are relatively similar in length to those of modern pronograde lemurs. Babakotia and Mesopropithecus differ from Megaladapis in exhibiting features of the midcarpal joint related to frequent supination and radioulnar deviation of the hand characteristic of animals that use vertical and quadrumanous climbing in their foraging behaviors. Comparative analysis of subfossil lemur wrist morphology complements and expands upon prior inferences based on other regions of the postcranial skeleton, and suggests a considerable degree of locomotor and postural heterogeneity among these recently extinct primates.     

The functional morphology of the cercopithecoid wrist and inferior radioulnar joints, and their bearing on some problems in the evolution of the Hominoidea.

The cercopithecoid wrist joint differs from the wrist joints of hominoids in several ways. The distal ulna, the distal radius, the pisiform, the triquetrum, the hamate, and the base of the fifth metacarpal are on the one hand remarkably alike among cercopithecoid genera, and on the other remarkably distinct from homologous bones in the Hominoidea. Functionally, the triquetrum and the pisiform, in conjuction with the ulnar styloid process, check the proximal carpal row during ulnar deviation, and are possibly important in stabilizing the wrist during dorsiflexion as well. The head of the ulna almost certainly betokens a range of radioulnar supination in cercopithecoids that is substantially less than is to be found in any of the hominoid genera. The articulation between the hamate bone and the base of the fifth metacarpal allows for considerable dorsiflexion in the Cercopithecoidea; this potential was not evidenct in any of the hominoids examined. Behaviorally, the cercopithecoid wrist can most profitably be viewed as an adaptation for a quadrupedal life style involving dorsiflexion of the wrist and palmigrade/digitigrade substrate contact. The hominoid wrist joint is not adapted for such a behavioral potential.     

A Tachyglossid-Like Humerus from the Early Cretaceous of South-Eastern Australia

A partial right humerus has been recovered from the Early Cretaceous (Albian) Eumeralla Formation at Dinosaur Cove in south-eastern Australia. General morphology, size and the presence of a single epicondylar foramen (the entepicondylar) suggest that the bone is from a mammal or an advanced therapsid reptile. The humerus is similar in size, shape and torsion to the equivalent bone of extant and late Neogene echidnas (Tachyglossidae) but, contrary to the situation in extant monotremes, in which the ulna and radius articulate with a single, largely bulbous condyle, it bears a shallow, pulley-shaped (i.e. trochlear-form) ulnar articulation that is confluent ventro-laterally with the bulbous radial condyle. This form of ulnar articulation distinguishes this bone from the humeri of most advanced therapsids and members of several major groups of Mesozoic mammals, which have a condylar ulnar articulation, but parallels the situation found in therian mammals and in some other lineages of Mesozoic mammals. As in extant monotremes the distal humerus is greatly expanded transversely and humeral torsion is strong. Transverse expansion of the distal humerus is evident in the humeri of the fossorial docodont Haldanodon, highly-fossorial talpids and some clearly fossorial dicynodont therapsids, but the fossil shows greatest overall similarity to extant monotremes and it is possible that the peculiar elbow joint of extant monotremes evolved from a condition approximating that of the fossil. On the basis of comparisons with Mesozoic and Cainozoic mammalian taxa in which humeral morphology is known, the Dinosaur Cove humerus is tentatively attributed to a monotreme. However, several apparently primitive features of the bone exclude the animal concerned from the extant families Tachyglossidae and Ornithorhynchidae and suggest that, if it is a monotreme, it is a stem-group monotreme. Whatever, the animal's true affinity, the gross morphology of its humerus indicates considerable capacity for rotation-thrust digging.     

Evolutionary convergence of primitive sabertooth craniomandibular morphology: the clouded leopard (<Emphasis Type="Italic">Neofelis nebulosa</Emphasis>) and <Emphasis Type="Italic">Paramachairodus ogygia</Emphasis> compared

The sabertoothed felids were among the most unusual predators in the late Tertiary ecosystems, and the sabertooth morphology is regarded as being absent from the modern ecosystems. In recent years, the primitive Paramachairodus has become well known and has yielded much valuable information on the primitive skull morphology among sabercats, providing the first evidence-based scenarios for the evolution of skull morphology in later sabercats. However, comparison of craniomandibular morphology of the extant clouded leopard Neofelis nebulosa and Paramachairodus reveals numerous similarities and subsequent divergence from other extant great cats. In several key aspects, the clouded leopard has approached a primitive sabercat craniomandibular morphology and has diverged markedly from its sister group, the Panthera lineage. A primitive sabertooth condition arose six times in the Tertiary period, not five as is traditionally advocated. The clouded leopard appears to be a useful model for understanding primitive sabercat morphology and could shed important light on sabercat evolution. The unusual nature of the clouded leopard implies that increased efforts should be spent on insuring the continuing survival of this rare and endangered species. Electronic Supplementary Material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Partial skeleton of Proconsul nyanzae from Mfangano Island,Kenya

A partial skeleton attributed to Proconsul nyanzae (KNM-MW 13142) is described. The fossils were found at a site on Mfangano Island, Kenya, which dates to 17.9 ± .1 million years ago. KNM-MW 13142 consists of six partial vertebrae (T12-S1), a nearly complete hipbone, most of the right femur and left femoral shaft, a fragmentary tibia and fibula, and a nearly complete talus and calcaneus. This skeleton provides the first pelvic fossil known for any East African Miocene hominoid. The new Proconsul specimen is compared to a large sample of extant anthropoids to determine its functional and phylogenetic affinities. In most aspects of its anatomy, KNM-MW 13142 closely resembles nonhominoid anthropoids. This individual had a long, flexible spine, narrow torso, and habitually pronograde posture, features characteristic of most extant monkeys. Evidence of spinal musculature suggests a generalized condition intermediate between that of cercopithecoids and hylobatids. The hindlimb of KNM-MW 13142 exhibits relatively mobile hip and ankle joints, with structural properties of the femur like those of hominoids. This mix of features implies a pattern of posture and locomotion that is unlike that of any extant primate. Many aspects of the Proconsul nyanzae locomotor skeleton may represent the primitive catarrhine condition. © 1993 Wiley-Liss, Inc.     

Knuckle-walking in Sivapithecus? The combined effects of homology and homoplasy with possible implications for pongine dispersals

Sivapithecus is a Miocene great ape from South Asia that is orangutan-like cranially but is distinctive postcranially. Work by others shows that the humerus resembles large terrestrial cercopithecoids proximally and suspensory hominoids distally, but most functional interpretations nevertheless situate Sivapithecus in an arboreal setting. We present a new quantitative analysis of the Sivapithecus capitate and hamate. Though the functional morphology of both bones suggests some degree of arboreality, the overall morphology is most similar to knuckle-walking African apes. Other features of the Sivapithecus humerus and hind limb are also functionally consistent with knuckle-walking, and we suggest that this locomotor behavior is a valid alternative functional interpretation of the postcranial morphology. We speculate that knuckle-walking in Sivapithecus would have evolved independently from African apes, perhaps for similar ecological reasons. The discovery of a possible pongine knuckle-walker challenges the hypotheses that (1) knuckle-walking evolved only once in hominoids and (2) knuckle-walking is too highly specialized to be the positional behavior from which human bipedalism evolved. The possibility of knuckle-walking in Sivapithecus may help to explain not only the curious combination of characters that typify the postcranium but also the unique postcranial morphology of extant Pongo. Furthermore, it may clarify the distribution of fossil pongines across many ecological zones in Eurasia in the Miocene and Pleistocene, as well as, independently, the spread of African apes across a diversity of environments in equatorial Africa.     

The Hand of Cercopithecoides williamsi (Mammalia,Primates): Earliest Evidence for Thumb Reduction among Colobine Monkeys

Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marked reduction of its first metacarpal relative to the medial metacarpals. Thus, KNM-ER 4420 is the first documented occurrence of cercopithecid pollical reduction in the fossil record. In the size of its first metacarpal relative to the medial metacarpals, C. williamsi is similar to extant African colobines, but different from cercopithecines, extant Asian colobines and the Late Miocene colobines Microcolobus and Mesopithecus. This feature clearly links the genus Cercopithecoides with the extant African colobine clade and makes it the first definitive African colobine in the fossil record. The postcranial adaptations to terrestriality in Cercopithecoides are most likely secondary, while ancestral colobinans (and colobines) were arboreal. Finally, the absence of any evidence for pollical reduction in Mesopithecus implies either independent thumb reduction in African and Asian colobines or multiple colobine dispersal events out of Africa. Based on the available evidence, we consider the first scenario more likely.     

The first fossil Paussine (Coleoptera: Carabidae) from Mexican amber

Eohomopterus simojovelensis n. sp., the first fossil record of the subfamily Paussinae (Coleoptera: Carabidae) from the Miocene amber of the Simojovel area, Chiapas, Mexico, is described. The morphology of the new species is compared withEohomopterus poinari Nagel, 1997 from Dominican amber as well as with extant representatives ofEohomopterus, and the biogeographical implications are discussed.      

New Sivapithecus postcranial specimens from the Siwaliks of Pakistan

Several new postcranial elements of Sivapithecus from the Siwaliks of Pakistan are described. These include a distal femur from the U-level of the Dhok Pathan Formation, a navicular from the Chinji Formation, and seven manual and pedal phalanges from the Nagri Formation. The functional morphology of these elements adds new detail to the reconstruction ofSivapithecus positional behavior. Femoral cross-sectional geometry indicates that the shaft was adapted to support mediolaterally directed loading. Femoral condylar asymmetry and a broad but shallow trochlea are distinctly ape-like, revealing capabilities for both rotation and withstanding eccentric loading in the knee. The navicular is characterized by features relating to a broad mid-tarsus and broad distal articulations for the cuneiforms. It also lacks a navicular tubercle as in Pongo. These features suggest that the foot was capable of a powerful grip on large supports, with an inversion/supination capability that would permit foot placement in a variety of positions. The morphology of the new phalanges, including evidence for a relatively large pollex, similarly suggests powerful grasping, consistent with prior evidence from the hallux and tarsus. The functional features of the new specimens permit refinement of previous interpretations of Sivapithecus positional capabilities. They suggest a locomotor repertoire dominated by pronograde activities and also such antipronograde activities as vertical climbing and clambering, but not by antipronograde suspensory activities as practiced by extant apes.     

The most basal beaked whale Ninoziphius platyrostris Muizon, 1983: clues on the evolutionary history of the family Ziphiidae (Cetacea: Odontoceti)

Ninoziphius platyrostris, from the late Neogene of Peru, is one of the best‐known fossil beaked whales (Odontoceti: Ziphiidae), with a holotype including the skull with ear bones, mandibles, teeth, and postcranial elements. Furthermore, based on several characters, including a complete functional upper and lower dentition, it is usually considered as one of the most archaic ziphiids. However, the poorly preserved dorsal portion of the holotype skull has led to unresolved phylogenetic relationships. With the addition of two newly prepared skulls from the same Peruvian locality we redescribed N. platyrostris. In the light of recent ziphiid discoveries, an emended diagnosis of the species is proposed here. In our cladistic analysis Ninoziphius is the most basal stem ziphiid. Newly observed or reassessed morphological traits allow functional and ecological considerations. The morphology of the oral apparatus suggests that Ninoziphius was less specialized for suction feeding than most extant ziphiids. Tooth wear in the holotype may indicate benthic feeding. Although the vertebral column of Ninoziphius corresponds to less developed locomotor abilities for deep dives, its cranial morphology does not provide definitive arguments for an echolocation system less efficient than in deep diving extant ziphiids. Finally, the phylogenetic tree produced was used to detail the evolutionary history of several major ziphiid features (dental reduction, development of mandibular tusks, and increased body size). © 2013 The Linnean Society of London     

Associated cranial and forelimb remains attributed to Australopithecus afarensis from Hadar, Ethiopia

A partial skeleton from Hadar, Ethiopia (A.L. 438-1) attributed to Australopithecus afarensis is comprised of part of the mandible, a frontal bone fragment, a complete left ulna, two second metacarpals, one third metacarpal, plus parts of the clavicle, humerus, radius, and right ulna. It is one of only a few early hominin specimens to preserve both cranial and postcranial elements. It also includes the first complete ulna from a large A. afarensis individual, and the first associated metacarpal and forelimb remains. This specimen, dated to approximately 3Ma, is among the geologically youngest A. afarensis fossils and is also one of the largest individuals known. Its ulnar to mandibular proportions are similar to those of the geologically older and much smaller A.L. 288-1, suggesting that body size increased without disproportional enlargement of the mandible. Overall, however, analysis of this large specimen and of the diminutive A.L. 288-1 demonstrates that the functional morphology of the A. afarensis upper limb was similar at all body sizes; there is no evidence to support the hypothesis that more than one hominin species is present at Hadar. Morphologically, all apparent apomorphic traits of the elbow, forearm, wrist, and hand of A.L. 438-1 are shared uniquely with humans. Compared to humans, A.L. 438-1 does have a more curved ulna, although A.L. 288-1 does not, and it appears to have had slightly less well-developed manipulatory capabilities of its hands, although still more derived than in apes. We conclude that selection for effective arboreality in the upper limb of Australopithecus afarensis was weaker than in non-hominins, and that manipulative ability was of greater selective advantage than in extant great apes.     

Gradual evolution in the African hunting dog lineage Systematic implications

The hunting dog, Lycaon pictus, is one of the most representative species of the extant African fauna and one of the most efficient predators in the World. This species is actually a relict within Sub-Saharan Africa, but its lineage is well recorded in Eurasia during the Pliocene, and in Eurasia and Africa during the Early Pleistocene, while its record during the Middle Pleistocene is not well documented. Though postcranial skeletal remains dating from the Early Pleistocene show a tetradactyl forelimb, a characteristic feature of the extant lycaon, unique among canids, the upper and lower dentitions show gradual evolution from a primitive morphology in the Late Pliocene specimens to the highly specialized trenchant carnassials of the extant predatory species. We propose a new systematics for the lineage, grouping all the forms within the genus Lycaon. To cite this article: B. Martínez-Navarro, L. Rook, C. R. Palevol 2 (2003).     

The femur of extinct bunodont otters in Africa (Carnivora,Mustelidae, Lutrinae)

This study compares fossil femora attributed to extinct African bunodont lutrines with extant mustelids and ursids to reconstruct locomotor behavior. Due to the immense size differences among taxa, shape data were used to compare morphology. Based on morphological differences, the fossil femora are suggested to belong to different taxa with different locomotor abilities and habitat preferences. The Langebaanweg femur is the oldest and has a typical mustelid morphology suggesting that it was a locomotor generalist like most mustelids. The West Turkana form is more like extant nonbunodont otters, but much larger, and may have belonged to a semiaquatic taxon. The enormous Omo femur shares some features with truly aquatic taxa (e.g., Enhydra) and is the most likely to have been fully aquatic. The same may hold true for the Hadar species as it is most similar to that from the Omo. If these femora truly belong to bunodont lutrines, then they are more diverse in postcranial morphology than in dental morphology.     

Additional materials of Myanmarpithecus yarshensis (Amphipithecidae, Primates) from the middle Eocene Pondaung Formation

Myanmarpithecus yarshensis is an amphipithecid primate from the middle Eocene Pondaung Formation in Myanmar. It was previously known based on maxillary fragments with P⁴–M³ and mandibular fragments with C–P₃ and M_2–3. This study reports new materials for the genus, including a humeral head fragment, a lingual fragment of the right M², a lingual fragment of the right M³, and a left I¹. These new materials were collected from approximately the same point, and likely belonged to the same individual. The upper molar morphology and size of the new materials show similarity to those of the type specimen, indicating that the new materials can be assigned to M. yarshensis. The humeral head is the first postcranial element that is associated with dental materials for amphipithecids. The morphological similarity between the previously reported larger humerus and this specimen confirms the assignment of the former specimen to Amphipithecidae and suggests common locomotor adaptations in the family. The upper central incisor is large relative to the molar fragments, but is within the variation among extant platyrrhines. The tooth is spatulate-shaped and high crowned, and lacks the mesial process, indicating similarity to I¹ of haplorhines and clear differences from that of adapoids. It has been suggested that amphipithecids, including Myanmarpithecus, have affinities with notharctine adapoids, but the morphology of I¹ does not support the notharctine hypothesis of the Amphipithecidae.     

Quantitative analyses of cross-sectional shape of the distal radius in three species of macaques

I conducted quantitative analyses of the cross-sectional shape of the distal radial shaft in three species of macaques, which differ in locomotor behavior: semi-terrestrial Japanese macaques (Macaca fuscata), arboreal long tailed macaques (M. fascicularis), and relatively terrestrial rhesus macaques (M. mulatta). I took CT scans of the distal radial shafts of a total of 180 specimens at the level of the inferior radio-ulnar articulation. From each CT image, the periosteal outline of the radius was traced automatically by a digital imaging technique. I determined five points (landmarks) on the outline by developing a standardized morphometric technique. Bone surface lengths were measured by using these landmarks and their soft tissue correlates were investigated. The results of this study were as follows: (1) Semi-terrestrial M. fuscata has features that are approximately intermediate between those of the other two species. M. fuscata has a relatively small groove for M. abductor pollicis longus and a large groove for Mm. extensor carpi radialis longus et brevis. These characters resemble those of M. fascicularis. On the other hand, the ulnar notch of M. fuscata is relatively large, a character which is similar to that of M. mulatta. Moreover, compared to the other two macaques, the surface of the flexor muscles of M. fuscata is intermediate in size. (2) The more terrestrial M. mulatta has a relatively large groove for M. abductor pollicis longus and a small groove for Mm. extensor carpi radialis longus et brevis. Moreover, M. mulatta has a relatively large ulnar notch and a small surface for the flexor muscles. (3) The arboreal M. fascicularis has similar features to those of M. fuscata for the first and second relative size index. However, in the ulnar notch, M. fascicularis has a peculiar character and the surface for the flexor muscles is relatively large compared to those of the other two species. These results can be interpreted in terms of positional habits and presumed functional demands. A form-functional study by Lemelin and Schmitt also corroborates the interpretations of the present study. Thus, the distal region of the forearm strongly reflects muscular development and joint resultant force, and is an important region for investigating locomotor adaptations in primates. The present study reveals the possibility of using this type of morphometric analysis for reconstructing the positional behavior of fossil primates.     

Distal Humeral Morphology Indicates Locomotory Divergence in Extinct Giant Kangaroos

Previous studies of the morphology of the humerus in kangaroos showed that the shape of the proximal humerus could distinguish between arboreal and terrestrial taxa among living mammals, and that the extinct “giant” kangaroos (members of the extinct subfamily Sthenurinae and the extinct macropodine genus Protemnodon) had divergent humeral anatomies from extant kangaroos. Here, we use 2D geometric morphometrics to capture the shape of the distal humerus in a range of extant and extinct marsupials and obtain similar results: sthenurines have humeral morphologies more similar to arboreal mammals, while large Protemnodon species (P. brehus and P. anak) have humeral morphologies more similar to terrestrial quadrupedal mammals. Our results provide further evidence for prior hypotheses: that sthenurines did not employ a locomotor mode that involved loading the forelimbs (likely employing bipedal striding as an alternative to quadrupedal or pentapedal locomotion at slow gaits), and that large Protemnodon species were more reliant on quadrupedal locomotion than their extant relatives. This greater diversity of locomotor modes among large Pleistocene kangaroos echoes studies that show a greater diversity in other aspects of ecology, such as diet and habitat occupancy.

     

A 3D quantitative comparison of trapezium and trapezoid relative articular and nonarticular surface areas in modern humans and great apes

The structure and functions of the modern human hand are critical components of what distinguishes Homo sapiens from the great apes (Gorilla, Pan, and Pongo). In this study, attention is focused on the trapezium and trapezoid, the two most lateral bones of the distal carpal row, in the four extant hominid genera, representing the first time they have been quantified and analyzed together as a morphological-functional complex. Our objective is to quantify the relative articular and nonarticular surface areas of these two bones and to test whether modern humans exhibit significant shape differences from the great apes, as predicted by previous qualitative analyses and the functional demands of differing manipulative and locomotor strategies. Modern humans were predicted to show larger relative first metacarpal and scaphoid surfaces on the trapezium because of the regular recruitment of the thumb during manipulative behaviors; alternatively, great apes were predicted to show larger relative second metacarpal and scaphoid surfaces on the trapezoid because of the functional demands on the hands during locomotor behaviors. Modern humans were also expected to exhibit larger relative mutual joint surfaces between the trapezoid and adjacent carpals than do the great apes because of assumed transverse loads generated by the functional demands of the modern human power grip. Using 3D bone models acquired through laser digitizing, the relative articular and nonarticular areas on each bone are quantified and compared. Multivariate analyses of these data clearly distinguish modern humans from the great apes. In total, the observed differences between modern humans and the great apes support morphological predictions based on the fact that this region of the human wrist is no longer involved in weight-bearing during locomotor behavior and is instead recruited solely for manipulative behaviors. The results provide the beginnings of a 3D comparative standard against which further extant and fossil primate wrist bones can be compared within the contexts of manipulative and locomotor behaviors.