Estimation of the forces exerted on the limb long bones of a white rhinoceros (Ceratotherium simum) using musculoskeletal modelling and simulation.

Heavy animals incur large forces on their limb bones, due to the transmission of body weight and ground reaction forces, and the contractions of the various muscles of the limbs. This is particularly true for rhinoceroses, the heaviest extant animals capable of galloping. Several studies have examined their musculoskeletal system and the forces their bones incur, but no detailed quantification has ever been attempted. Such quantification could help understand better the link between form and function in giant land animals. Here we constructed three-dimensional musculoskeletal models of the forelimb and hindlimb of Ceratotherium simum, the heaviest extant rhino species, and used static optimisation (inverse) simulations to estimate the forces applied on the bones when standing at rest, including magnitudes and directions. Overall, unsurprisingly, the most active muscles were antigravity muscles, which generate moments opposing body weight (thereby incurring the ground reaction force), and thus keep the joints extended, avoiding joint collapse via flexion. Some muscles have an antigravity action around several joints, and thus were found to be highly active, likely specialised in body weight support (ulnaris lateralis; digital flexors). The humerus was subjected to the greatest amount of forces in terms of total magnitude; forces on the humerus furthermore came from a great variety of directions. The radius was mainly subject to high-magnitude compressive joint reaction forces, but to little muscular tension, whereas the opposite pattern was observed for the ulna. The femur had a pattern similar to that of the humerus, and the tibia's pattern was intermediate, being subject to great compression in its caudal side but to great tension in its cranial side (i.e. bending). The fibula was subject to by far the lowest force magnitude. Overall, the forces estimated were consistent with the documented morphofunctional adaptations of C. simum's long bones, which have larger insertion areas for several muscles and a greater robusticity overall than those of lighter rhinos, likely reflecting the intense forces we estimated here. Our estimates of muscle and bone (joint) loading regimes for this giant tetrapod improve the understanding of the links between form and function in supportive tissues and could be extended to other aspects of bone morphology, such as microanatomy.

Comparative forelimb myology and muscular architecture of a juvenile Malayan tapir (Tapirus indicus).

The absence of preserved soft tissues in the fossil record is frequently a hindrance for palaeontologists wishing to investigate morphological shifts in key skeletal systems, such as the limbs. Understanding the soft tissue composition of modern species can aid in understanding changes in musculoskeletal features through evolution, including those pertaining to locomotion. Establishing anatomical differences in soft tissues utilising an extant phylogenetic bracket can, in turn, assist in interpreting morphological changes in hard tissues and modelling musculoskeletal movements during evolutionary transitions (e.g. digit reduction in perissodactyls). Perissodactyls (horses, rhinoceroses, tapirs and their relatives) are known to have originated with a four-toed (tetradactyl) forelimb condition. Equids proceeded to reduce all but their central digit, resulting in monodactyly, whereas tapirs retained the ancestral tetradactyl state. The modern Malayan tapir (Tapirus indicus) has been shown to exhibit fully functional tetradactyly in its forelimb, more so than any other tapir, and represents an ideal case-study for muscular arrangement and architectural comparison with the highly derived monodactyl Equus. Here, we present the first quantification of muscular architecture of a tetradactyl perissodactyl (T. indicus), and compare it to measurements from modern monodactyl caballine horse (Equus ferus caballus). Each muscle of the tapir forelimb was dissected out from a cadaver and measured for architectural properties: muscle-tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and resting fibre length. Comparative parameters [physiological cross-sectional area (PCSA), muscle volume, and % muscle mass] were then calculated from the raw measurements. In the shoulder region, the infraspinatus of T. indicus exhibits dual origination sites on either side of the deflected scapular spine. Within ungulates, this condition has only been previously reported in suids. Differences in relative contribution to limb muscle mass between T. indicus and Equus highlight forelimb muscles that affect mobility in the lateral and medial digits (e.g. extensor digitorum lateralis). These muscles were likely reduced in equids during their evolutionary transition from tetradactyl forest-dwellers to monodactyl, open-habitat specialists. Patterns of PCSA across the forelimb were similar between T. indicus and Equus, with the notable exceptions of the biceps brachii and flexor carpi ulnaris, which were much larger in Equus. The differences observed in PCSA between the tapir and horse forelimb muscles highlight muscles that are essential for maintaining stability in the monodactyl limb while moving at high speeds. This quantitative dataset of muscle architecture in a functionally tetradactyl perissodactyl is a pivotal first step towards reconstructing the locomotor capabilities of extinct, four-toed ancestors of modern perissodactyls, and providing further insights into the equid locomotor transition.

A first glimpse at the influence of body mass in the morphological integration of the limb long bones: an investigation in modern rhinoceroses.

The appendicular skeleton of tetrapods is a particularly integrated structure due to the shared developmental origin or similar functional constraints exerted on its elements. Among these constraints, body mass is considered strongly to influence its integration but its effect on shape covariation has rarely been addressed in mammals, especially in heavy taxa. Here, we propose to explore the covariation patterns of the long bones in heavy animals and their link to body mass. We investigate the five modern rhinoceros species, which display an important range of bodyweight. We used a 3D geometric morphometric approach to describe the shape covariation of the six bones composing the stylopodium and zeugopodium both among and within species. Our results indicate that the appendicular skeleton of modern rhinos is a strongly integrated structure. At the interspecific level, the shape covariation is roughly similar between all pairs of bones and mainly concerns the muscular insertions related to powerful flexion and extension movements. The forelimb integration appears higher and more related to body mass than that of the hind limb, suggesting a specialization for weight support. The integration of the stylopodium elements does not seem to relate to body mass in our sample, which suggests a greater effect of shared developmental factors. Conversely, the covariation of the zeugopodium bones seems more associated with body mass, particularly for the radius-ulna pair. The fibula appears poorly integrated with other bones, especially within non-Rhinoceros species, which may represent a case of parcellation due to a functional dissociation between the hind limb bones. The exploration of the integration patterns at the intraspecific level also highlights a more prominent effect of age over individual body mass on shape covariation within C. simum. This study lends support to previous hypotheses indicating a link between high body mass and high integration level.

Paleoecological implications of dental mesowear and hypsodonty in fossil ungulates from Kanapoi.

The Pliocene site of Kanapoi is key to our understanding of the environmental context of the earliest species of Australopithecus. Various approaches have been used to reconstruct the environments of this site, and here we contribute new data and analyses using mesowear and hypsodonty. The dental traits of 98 bovids, suids and rhinocerotids from Kanapoi were analyzed using these proxies. Results indicate that most of the animals analyzed had a relatively abrasive diet. Bovids in the assemblage incorporated more grass into their diet than do modern species of the same tribe or genus. Although Pliocene Kanapoi likely had complex environments, our analysis indicates that grassy habitats were a dominant component of the ecosystem, a conclusion that supports the results of previous investigations of the paleoecology of the site.

Perissodactyla (Rhinocerotidae and Equidae) from Kanapoi.

The Kanapoi collection of Rhinocerotidae, first studied by Hooijer and Patterson (1972), now consists of 25 specimens and substantial reinterpretation of their affinities is made here. Kanapoi post-dates the extinction of Brachypotherium and the whole collection belongs to the Dicerotini. It is important because it includes the type-specimen of Diceros praecox, a species that remains poorly known, but looks slightly larger and more primitive than the modern 'black' rhino, Diceros bicornis. A second species is probably ancestral to the modern 'white' rhino, Ceratotherium simum; it looks identical to the Pleistocene North African Ceratotherium mauritanicum, of which Ceratotherium efficax is probably a synonym. The evolution of the Dicerotini in Africa can be regarded as an increasing divergence in diet and related morphofunctional adaptations in the two lineages. The co-occurrence at Kanapoi of both Diceros and Ceratotherium, with distinct dietary preferences, suggests some habitat heterogeneity, although the low sample size prevents robust paleoecological conclusions. The Equidae are also rare and consist mostly of isolated teeth. I take the most parsimonious option of tentatively including all of them in a single species, whose identification is left open. Dental features of eastern African Pliocene to Pleistocene hipparions may reflect increasing adaptation to grazing.

Brain Volume Fractions in Mammals in Relation to Behavior in Carnivores, Primates, Ungulates, and Rodents.

The volume fraction (VF) of a given brain region, or the proper mass, ought to reflect the importance of that region in the life of a given species. This study sought to examine the VF of various brain regions across 61 different species of mammals to discern if there were regularities or differences among mammalian orders. We examined the brains of carnivores (n = 17), ungulates (n = 8), rodents (n = 7), primates (n = 11), and other mammals (n = 18) from the online collections at the National Museum of Health and Medicine. We measured and obtained the VF of several brain regions: the striatum, thalamus, neocortex, cerebellum, hippocampus, and piriform area. We refined our analyses by using phylogenetic size correction, yielding the corrected (c)VF. Our groups showed marked differences in gross brain architecture. Primates and carnivores were divergent in some measures, particularly the cVF of the striatum, even though their overall brain size range was roughly the same. Rodents predictably had relatively large cVFs of subcortical structures due to the fact that their neocortical cVF was smaller, particularly when compared to primates. Not so predictably, rodents had the largest cerebellar cVF, and there were marked discrepancies in cerebellar data across groups. Ungulates had a larger piriform area than primates, perhaps due to their olfactory processing abilities. We provide interpretations of our results in the light of the comparative behavioral and neuroanatomical literature.

VAGINOSCOPIC IDENTIFICATION OF A VERTICAL VAGINAL SEPTUM IN ONE PRIMIPAROUS AND THREE NULLIPAROUS SOUTHERN WHITE RHINOCEROS (CERATOTHERIUM SIMUM SIMUM).

Vaginoscopy using a 10-mm, 30° forward viewing rigid endoscope was used to evaluate the caudal reproductive tract of four subadult southern white rhinoceros (Ceratotherium simum simum). A vertical vaginal septum was documented in all four animals, including a primiparous cow that gave birth to a stillborn calf 14 months before vaginoscopy. Vaginoscopy using a 57-cm-long, 10-mm, 30° forward viewing endoscope provides adequate visualization of the caudal reproductive track in the southern white rhinoceros, and a detailed description of the vertical vaginal septum is presented. Additionally, the presence of a vertical vaginal septum in a primiparous southern white rhinoceros suggests the presence of this anatomic structure cannot be used as a proxy of nulliparity for captive southern white rhinoceros.

Dietary traits of the ungulates from the HWK EE site at Olduvai Gorge (Tanzania): Diachronic changes and seasonality.

The Oldowan site HWK EE (Olduvai Gorge, Tanzania) has yielded a large fossil and stone tool assemblage at the transition from Lower to Middle Bed II, ∼1.7 Ma. Integrated tooth wear and stable isotope analyses were performed on the three most abundant ungulate taxa from HWK EE, namely Alcelaphini, cf. Antidorcas recki (Antilopini) and Equus oldowayensis (Equini), to infer dietary traits in each taxon. Some paleodietary changes were observed for cf. A. recki and E. oldowayensis based on tooth wear at the transition from the Lemuta to the Lower Augitic Sandstone (LAS) interval within the HWK EE sequence. Stable carbon and oxygen isotope data show no significant changes in bulk diet or hydroclimate between the Lemuta and LAS intervals. The combined tooth wear and stable isotope data suggest similar paleoecological conditions across the two HWK EE intervals, but that differences in vegetation consumed among ungulates may have resulted in changes in dietary niches. Integrating tooth wear and stable isotope analyses permits the characterization of ungulate diets and habitats at HWK EE where C4 dominated and minor mixed C3 and C4 habitats were present. Our results provide a better understanding of the paleoenvironmental conditions of the Lemuta and LAS intervals. The LAS assemblage was mostly accumulated during relatively dry periods at Olduvai Gorge when grasses were not as readily available and grazing animals may have been more nutritionally-stressed than during the formation of the Lemuta assemblage. This helps to contextualize variations in hominin and carnivore feeding behavior observed from the faunal assemblages produced during the two main occupations of the site.

Parathyroid, Thyroid and Recurrent Laryngeal Nerve Anatomy in an Indian Rhinoceros (Rhinoceros unicornis).

INTRODUCTION: The parathyroid gland was first identified in the Indian rhinoceros in 1849 by Sir Richard Owen. We performed a necropsy in an Indian rhinoceros, recapitulating Owen's dissection and display what appear to be the initial identification of the recurrent laryngeal nerve in situ and the anatomy and histology of the largest rhinoceros parathyroid glands yet identified. MATERIALS AND METHODS: Patrick T. Rhino, a 41-year-old Indian rhinoceros was born in 1974. His early years were unremarkable. In 2006, he was donated to White Oak Conservation in Yulee, Florida, where he bred and sustained minor injuries. In his geriatric years, he developed a cataract and degenerative joint disease (DJD). At age 41, he developed progressive ataxia and lameness and was euthanized to minimize suffering when he was unable to stand. ROS, FH, SH and medication history were unremarkable. Physical exam was age and species appropriate. Pre-mortem serum demonstrated: creat 1.8 mg/dL (0.8-2.1), calcium 10.6 mg/dL (9.7-13.1), phos 3.8 mg/dL (2.5-6.7), alk phos 69 U/L (26-158) and intact PTH 44.1 pg/mL (rhinoceros reference range: unknown). Necropsy revealed intervertebral DJD with thoracic spondylosis, which combined with osteoporosis, resulted in thoracic myelopathy and ataxia. The neck block was sent in formalin to the Yale University School of Medicine. RESULTS: Detailed dissection was performed under loupe magnification. Presumed structures were photographed in situ and biopsied. The thyroid was identified deep to the strap muscles, received its blood supply from the inferior and superior thyroid arteries and was blue in color. The right recurrent laryngeal nerve, identified and photographed in situ for the first time in the rhinoceros, was deep to the inferior thyroid artery and was traced throughout its cervical course. Single parathyroid glands identified on the lateral thyroid lobes received their blood supply from the inferior thyroid arteries and were confirmed histologically. They appear to be the largest parathyroids yet identified in the rhinoceros with estimated weights of 6,280 and 11,000 mg, respectively. Although the etiology of the parathyroid gland enlargement is unknown, the specimen has been preserved recapitulating the dissection performed by Sir Richard Owen. CONCLUSION: The parathyroids, thyroid and recurrent laryngeal nerve were identified in an Indian rhinoceros. This appears to be the first display of the rhinoceros recurrent laryngeal nerve in situ, and the parathyroid glands are the largest yet identified in the rhinoceros.

IDENTIFICATION OF A NASOCONCHAL PARANASAL SINUS IN THE WHITE RHINOCEROS ( CERATOTHERIUM SIMUM).

African rhinoceros are poached for their horns using indiscriminate and aggressive methods. Rhinoceros that survive these attacks often have severe facial trauma, and treatment is limited by a lack of understanding and published information of the normal anatomy. This study was performed to investigate and describe the anatomy of the most commonly injured area of the head of the white rhinoceros ( Ceratotherium simum). Two white rhinoceros cadaver heads were imaged by computed tomography and grossly dissected. A combined dorsal conchal sinus and nasal sinus (named the nasoconchal sinus) was identified and confirmed to be readily exposed by horn removal. The nasoconchal sinus communicates via a relatively large opening with the middle nasal meatus of the nasal cavity. Awareness of the combined sinus space and its single communicating pathway will assist with accurate assessment and treatment of trauma to the dorsal facial region of the white rhinoceros.

Comparative cranial ontogeny of Tapirus (Mammalia: Perissodactyla: Tapiridae).

Skull morphology in tapirs is particularly interesting due to the presence of a proboscis with important trophic, sensory and behavioral functions. Several studies have dealt with tapir skull osteology but chiefly in a comparative framework between fossil and recent species of tapirs. Only one study examined an aspect of cranial ontogeny, development of the sagittal crest (Holbrook. J Zool Soc Lond 2002; 256; 215). Our goal is to describe in detail the morphological changes that occur during the postnatal ontogeny of the skull in two representative tapir species, Tapirus terrestris and Tapirus indicus, and to explore possible functional consequences of their developmental trajectories. We compared qualitative features of the skull on a growth series of 46 specimens of T. terrestris ordered on the basis of the sequence of eruption and tooth wear, dividing the sample into three age classes: class Y (very young juvenile), class J (from young juvenile to young adult) and class A (full and old adult). The qualitative morphological analysis consisted of describing changes in the series in each skull bone and major skull structure, including the type and degree of transformation (e.g. appearance, fusion) of cranial features (e.g. processes, foramina) and articulations (sutures, synchondroses, and synovial joints). We then measured 23 cranial variables in 46 specimens of T. terrestris that included the entire ontogenetic series from newborn to old adults. We applied statistical multivariate techniques to describe allometric growth, and compared the results with the allometric trends calculated for a sample of 25 specimens of T. indicus. Results show that the skull structure was largely conserved throughout the postnatal ontogeny in T. terrestris, so class Y was remarkably similar to class A in overall shape, with the most significant changes localized in the masticatory apparatus, specifically the maxillary tuber as a support of the large-sized permanent postcanine dentition, and correlated changes in diastemata, mandibular body, and sagittal and nuchal crests. In the nasal region, ontogenetic remodeling affected the space for the meatal diverticulum and the surfaces for the origin of the proboscis musculature. Overall, ontogenetic trajectories exhibited more negative allometric components in T. indicus than in T. terrestris, and they shared 47.83% of allometric trends. Tapirus indicus differed most significantly from T. terrestris in the allometry of postcanine toothrows, diastemata and mandibular body. Thus, some allometric trends seem to be highly conserved among the species studied, and the changes observed showed a strong functional and likely adaptive basis in this lineage of ungulates.

Hair microstructure of the first time found calf of woolly rhinoceros Coelodonta antiquitatis.

Hair microstructure of the first calf of the woolly rhinoceros Coelodonta antiquitatis found in Sakha in 2014 (the neck and hind leg hair) was examined by the light and electron scanning microscopy. The calf hair features were compared with those of two adults studied earlier. The calf coat color was much lighter than in adults, from pale ashy to blond. The extent of hair differentiation, dimensional and pigmentation indices were lower in the calf than in adult rhinoceroses. There was no medulla in the calf hairs, while in those of adults it was occasionally found. The cortical and cuticular layer microstructure was similar in all the animals compared. In both calf and adult hairs, there were traces of mechanical damage.

Radiographic protocol and normal anatomy of the hind feet in the white rhinoceros (Ceratotherium simum).

Foot pathology is a common and important health concern in captive rhinoceroses worldwide, but osteopathologies are rarely diagnosed, partly because of a lack of radiographic protocols. Here, we aimed to develop the first radiographic protocol for rhinoceros feet and describe the radiographic anatomy of the white rhinoceros (Ceratotherium simum) hind foot (pes). Computed tomographic images were obtained of nine cadaver pedes from seven different white rhinoceroses and assessed for pathology. A single foot deemed free of pathology was radiographed using a range of different projections and exposures to determine the best protocol. 3D models were produced from the CT images and were displayed with the real radiographs to describe the normal radiographic anatomy of the white rhinoceros pes. An optimal radiographic projection was determined for each bone in the rhinoceros pes focusing on highlighting areas where pathology has been previously described. The projections deemed to be most useful were D60Pr-PlDiO (digit III), D45Pr45M-PlDiLO (digit II), and D40Pr35L-PlDiLO (digit IV). The primary beam was centered 5-7 cm proximal to the cuticle on the digit of interest. Articular surfaces, ridges, grooves, tubercles, processes and fossae were identified. The radiographic protocol we have developed along with the normal radiographic anatomy we have described will allow for more accessible and effective diagnosis of white rhinoceros foot osteopathologies.

CT based 3D reconstruction of the forefoot's blood supply in a white rhinoceros.

BACKGROUND: The white rhinoceros (Ceratotherium simum) is close to extinction, listed as "Near Threatened", with a decreasing population on the Red List of Threatened Species of the International Union for Conservation of Nature. In at least 50% of the specimens in captivity, podiatric diseases, such as osteitis, osteomyelitis, chip fractures, enthesophytes, fractures and osteoarthritis were found during necropsy. These osteal deformations cause further pathogenic alterations in the soft tissues, particularly in the digital cushion. The literature provides good description of the skeleton of the rhino's limbs, but similar for the vascular system is non-existent. In order to recognize the symptoms in an early state and for a successful surgical treatment, precise knowledge of the vascular anatomy is essential. The purpose of our study was to provide detailed anatomical description of the blood supply of the digits and that of the digital cushion. RESULTS: The blood supply of the distal foot, digits and digital cushions were perfectly visible on the reconstructed and coloured 3D models. The deep palmar arch provided not only the blood supply to the digits but had a palmaro-distal running branch which developed a trifurcation proximal to the proximal sesamoid bones of the third digit. Two of its branches participated in the blood supply of the digits' proximal palmar surface, while the major branch supplied the digital cushion from proximal direction. CONCLUSIONS: Our findings show a unique blood supply: the main vessels of the digital cushion stem both directly from the deep palmar arch and from the digits' own arteries. The detailed description of vessels may be useful in planning surgery of the region and also in cases where the veins of the ear are not accessible.

Osteopathology in the feet of rhinoceroses: lesion type and distribution.

An estimated 1,170 white (Ceratotherium simum), black (Diceros bicornis), greater one-horned (Rhinoceros unicornis), and Sumatran (Dicerorhinus sumatrensis) rhinoceroses are kept in captivity worldwide, where they are a popular public attraction and serve important roles in education and conservation. Rhinoceroses in captivity are reportedly affected by a variety of foot conditions, including abscesses, nail cracking, and pododermatitis, but there are few studies reporting associated bony pathology in these species. This study aimed to describe osteopathology in rhinoceros feet and identify normal and abnormal osteologic features of rhinoceros feet. The metacarpal-tarsal and phalangeal bones from 81 feet (67 skeletal specimens and 14 cadaveric feet), derived from 27 rhinoceroses of various species, were evaluated in the study (1 black, 11 white, 2 greater one-horned, 3 Javan, 9 Sumatran, and 1 unknown). Bones were examined visually (skeletal specimens) or by computed tomography (cadaver specimens) for evidence of bony lesions. Of the 27 rhinoceroses examined, 22 showed some degree of bone pathology in at least one limb. Six broad categories of pathologic change were identified, with numbers in parentheses representing numbers of rhinoceroses with lesions in at least one limb/number of rhinoceroses examined: enthesopathy (20/27), osteoarthritis (15/27), pathologic bone remodeling (12/27), osteitis-osteomyelitis (3/27), fracture (3/8), and subluxation (3/8). The frequency of pathologic changes in fore- and hind limbs was not significantly different. Most (91%) enthesopathies were observed on the proximal phalanges of the digits, and osteoarthritis was most common in the distal interphalangeal joints of the medial and lateral digits (32 and 26%, respectively). In addition to the pathology described, all examined rhinoceroses also had multiple small surface lucencies in the distal limb bones as an apparently normal anatomic feature. This study is an important first step in identifying both normal and pathologic features of rhinoceros feet and hopefully will thereby contribute to the improved knowledge and care of these species.

A new discovery in the permafrost of Yakutia sheds light on the nasal horn morphology of the woolly rhinoceros.

Extinct woolly rhinoceroses were iconic representatives of the Late Pleistocene mammoth fauna of Eurasia. These animals were characterized by two huge keratinous horns. In adults, the length of the nasal horn often exceeded one meter. The nasal horn of Coelodonta was characterized by an unusual feature for rhinoceroses-the width of its base was considerably narrower than the width of the rugosity area on the nasal bones of the skull. In this study, a new discovery of woolly rhinoceros' nasal horn in the permafrost of Yakutia is described. This specimen shows that the shape of the base of the woolly rhino's nasal horn corresponds well to the shape (length and width) of the nasal rugosity area. The base of the nasal horn of Coelodonta was markedly elongated anteroposteriorly compared to extant rhinoceroses. Its length was about 150% of the width. We therefore suggest that the narrower shape of the nasal horn base in the majority of previously found specimens was associated with secondary damage after burial caused by maceration.

Sagittal crest morphology decoupled from relative bite performance in Pleistocene tapirs (Perissodactyla: Tapiridae).

Bite force is often associated with specific morphological features, such as sagittal crests. The presence of a pronounced sagittal crest in some tapirs (Perissodactyla: Tapiridae) was recently shown to be negatively correlated with hard-object feeding, in contrast with similar cranial structures in carnivorans. The aim of this study was to investigate bite forces and sagittal crest heights across a wide range of modern and extinct tapirs and apply a comparative investigation to establish whether these features are correlated across a broad phylogenetic scope. We examined a sample of 71 specimens representing 15 tapir species (5 extant, 10 extinct) using the dry-skull method, linear measurements of cranial features, phylogenetic reconstruction, and comparative analyses. Tapirs were found to exhibit variation in bite force and sagittal crest height across their phylogeny and between different biogeographical realms, with high-crested morphologies occurring mostly in Neotropical species. The highest bite forces within tapirs appear to be driven by estimates for the masseter-pterygoid muscle complex, rather than predicted forces for the temporalis muscle. Our results demonstrate that relative sagittal crest height is poorly correlated with relative cranial bite force, suggesting high force application is not a driver for pronounced sagittal crests in this sample. The divergent biomechanical capabilities of different contemporaneous tapirids may have allowed multiple species to occupy overlapping territories and partition resources to avoid excess competition. Bite forces in tapirs peak in Pleistocene species, independent of body size, suggesting possible dietary shifts as a potential result of climatic changes during this epoch.

Biomechanical determinants of transverse and rotary gallop in cursorial mammals.

Transverse and rotary gallop differ in the placement of the leading hindfeet and forefeet: ipsilateral in the former gait, contralateral in the latter. We analysed 351 filmed sequences to assess the gallop type of 89 investigated mammalian species belonging to Carnivora, Artiodactyla and Perissodactyla orders. Twenty-three biometrical, ecological and physiological parameters were collected for each species both from literature data and from animal specimens. Most of the species showed only one kind of gallop: transverse (42%) or rotary (39%), while some species performed rotary gallop only at high speed (19%). In a factorial analysis, the first principal component (PC), which accounted for 40% of the total variance, was positively correlated to the relative speed and negatively correlated to size and body mass. The second PC was correlated to the ratio between distal and proximal limb segments. Large size and longer proximal limb segments were associated with transverse gallop, while rotary and speed-dependent species showed higher metacarpus/humerus and metatarsus/femur length ratio and faster relative speeds. The resulting limb excursion angles were proportional to the square-root of the Froude number, and significantly higher in rotary gallopers. The gait pattern analysis indicated significant differences between transverse and rotary gallop in forelimb and hindlimb duty factor (t-test; P<0.001), and in duration of the forelimb contact (t-test; P=0.045). Our results show that an exclusive gallop gait is adopted by a large number of mammalian species, and indicate that the gallop pattern depends on diverse environmental, morphometrical and biomechanical characters.

Another one bites the dust: faecal silica levels in large herbivores correlate with high-crowned teeth.

The circumstances of the evolution of hypsodonty (= high-crowned teeth) are a bone of contention. Hypsodonty is usually linked to diet abrasiveness, either from siliceous phytoliths (monocotyledons) or from grit (dusty environments). However, any empirical quantitative approach testing the relation of ingested silica and hypsodonty is lacking. In this study, faecal silica content was quantified as acid detergent insoluble ash and used as proxy for silica ingested by large African herbivores of different digestive types, feeding strategies and hypsodonty levels. Separate sample sets were used for the dry (n = 15 species) and wet (n = 13 species) season. Average faecal silica contents were 17-46 g kg(-1) dry matter (DM) for browsing and 52-163 g kg(-1) DM for grazing herbivores. No difference was detected between the wet (97.5 ± 14.4 g kg(-1) DM) and dry season (93.5 ± 13.7 g kg(-1) DM) faecal silica. In a phylogenetically controlled analysis, a strong positive correlation (dry season r = 0.80, p < 0.0005; wet season r = 0.74, p < 0.005) was found between hypsodonty index and faecal silica levels. While surprisingly our results do not indicate major seasonal changes in silica ingested, the correlation of faecal silica and hypsodonty supports a scenario of a dominant role of abrasive silica in the evolution of high-crowned teeth.

Giant rhinoceros Paraceratherium and other vertebrates from Oligocene and middle Miocene deposits of the Kagizman-Tuzluca Basin, Eastern Turkey.

A recent fieldwork in the Kagizman-Tuzluca Basin in northeastern Turkey led us to the discovery of three vertebrate localities which yielded some limb bones of the giant rhino Paraceratherium, a crocodile tooth, and some small mammals, respectively. These discoveries allowed, for the first time to date some parts of the sedimentary units of this basin. This study also shows that the dispersal area of Paraceratherium is wider than it was known before. Eastern Turkey has several Cenozoic sedimentary basins formed during the collision of the Arabian and Eurasian plates. They are poorly documented for vertebrate paleontology. Consequently, the timing of tectonic activities, which led to the formation of the East Anatolian accretionary complex, is not constrained enough with a solid chronological framework. This study provides the first biostratigraphic evidences for the infill under the control of the compressive tectonic regime, which built the East Anatolian Plateau.