Ecomorphology of radii in Canidae: Application to fragmentary fossils from Plio-Pleistocene hominin assemblages

Fragmentary long bone material from fossil Carnivora is rarely considered to support palaeoenvironmental reconstructions. Here, we use morphometry of the radius in extant carnivorans of the dog family (Canidae) to reconstruct the palaeobiology of extinct canids from Olduvai Gorge, Tanzania (Bed I and II) and Koobi Fora, Kenya. We use radius morphometrics to predict adaptation to prey size and introduce a new method for quantifying canid habitat adaptations based on the geographic distributions of the extant species sampled. Linear Discriminant Function Analyses (DFA) and cluster neighbour-joining algorithms are employed to investigate radial morphometrics as described by 29 linear measurements. Results of our analyses suggest that a phylogenetic signal is present in radial morphometrics, even if it does not allow us to accurately discriminate among genera. A binary prey size categorisation of “small-medium” versus “large” prey can be more accurately predicted than a habitat categorisation scheme (Open, Mixed, Closed). The East African fossil specimens examined show morphometric affinities with the golden jackal (Canis aureus) and coyote (Canis latrans) and are likely attributable to the genus Canis. Fragmentary fossil specimens from Olduvai Gorge are predicted as habitat generalists (Open for Bed I and Mixed for Bed II) adapted for hunting small-medium prey, whereas the specimen from Koobi Fora was predicted as inhabiting mixed habitats and adapted for killing large prey. This study supports the inclusion of fossil Canidae in palaeoecological analyses attempting to clarify the palaeoenvironment of early hominin fossil sites

The potential and pitfalls of using simple dental metrics to infer the diets of African antelopes (Mammalia: Bovidae)

The use of mesowear to infer diets of extinct species is fast becoming widespread in palaeoecological studies. Nevertheless, traditional mesowear analyses suffer from a specimen number limitation, in that a minimum number of specimens identified to the species level is necessary to make accurate dietary predictions. This is problematic in many fossil African antelope (Mammalia: Bovidae) assemblages, where isolated teeth cannot always be assigned to species. Hereweexplore the possibility of using simple dental metrics to predict diets on the basis of individual teeth as well as gnathic rows using linear discriminant function analyses.We find that browsers are accurately classified at both the individual and species levels, across all models and tooth positions. Mixed feeders and grazers are classified accurately only sometimes, and this is probably a reflection of the more limited sample size of larger bodied species in our study. Body size was a highly significant predictor of the inaccurate classifications obtained in our models, with larger bodied species tending to grazing classifications and smaller bodied species browsing classifications. Nevertheless, the models correctly classify the majority of specimens we examined to their correct trophic group, as determined through stable isotope analyses or as defined through the literature. The methods outlined hold some promise for determining the diets of isolated fossil specimens unassigned to species in a simple manner and, when used in conjunction with other palaeodietary and palaeoecological proxies, may help determine palaeoenvironments more accurately

First report of Quaternary mammals from the Qalehjough area, Lut Desert, Eastern Iran

Taxonomic study of Quaternary mammal remains from the Qalehjough fossil site, eastern Iran, has resulted in the identification of two mammal orders, Artiodactyla and Perissodactyla, with four families and six taxa. Of particular note was the recovery of Stephanorhinus and a caballoid horse. These remains have provided the first opportunity to examine Late Quaternary faunal assemblages in the northern parts of the Lut Desert, eastern Iran. The Qalehjough faunal assemblage documents some zoogeographic characteristics of the eastern Iranian Plateau, and suggests that palaeoenvironments in this part of Iran during the Pleistocene were more humid and wooded than today. The disappearance of rhinoceroses and caballoid horses from this region is most likely a result of climate change and concomitant habitat loss

Cartesian coordinates in two-dimensional bone histology images

Palaeohistologists who work with well-preserved hominin cortical bone can examine two-dimensional (2D) histology images for quantitative parameters of secondary osteons and Haversian canals to reconstruct past bone remodelling. Standard techniques in this space include area measurements and counts of histology components recorded from an image. The ‘point-count’ technique involves counting all the items (e.g., secondary osteons, osteocyte lacunae) of interest per image area. The open access image analysis software ImageJ/ FIJI facilitates this technique in a user-friendly way. Raw data points are captured and can be saved in a spreadsheet. Aside from the total number of counts, the software also issues Cartesian (XY) coordinates locating each counted point. These XY coordinates are typically neglected within palaeohistological approaches due their assumed irrelevance to research questions of bone remodelling significance. We provide a short evaluation of XY coordinates captured by ImageJ/FIJI from 2D bone histology images, and a protocol for a simple calculation of XY distances that follow the path of point counting. We focus on osteocyte lacunae which serve as a proxy for osteoblast-osteocyte conversion in live bone by replicating the protocol on a bone sample from a Medieval English individual. We discuss the potential of XY coordinates for reconstructing the proximity of osteocyte lacunae and related bone remodelling activity through exchange of nutrients by neighbouring cells. We recommend palaeohistologists report XY coordinate data in their results to ensure better hominin palaeobiology characterisation

Bovid ecomorphology and hominin paleoenvironments of the Shungura Formation, lower Omo River Valley, Ethiopia.

The Shungura Formation in the lower Omo River Valley, southern Ethiopia, has yielded an important paleontological and archeological record from the Pliocene and Pleistocene of eastern Africa. Fossils are common throughout the sequence and provide evidence of paleoenvironments and environmental change through time. This study developed discriminant function ecomorphology models that linked astragalus morphology to broadly defined habitat categories (open, light cover, heavy cover, forest, and wetlands) using modern bovids of known ecology. These models used seven variables suitable for use on fragmentary fossils and had overall classification success rates of >82%. Four hundred and one fossils were analyzed from Shungura Formation members B through G (3.4-1.9 million years ago). Analysis by member documented the full range of ecomorph categories, demonstrating that a wide range of habitats existed along the axis of the paleo-Omo River. Heavy cover ecomorphs, reflecting habitats such as woodland and heavy bushland, were the most common in the fossil sample. The trend of increasing open cover habitats from Members C through F suggested by other paleoenvironmental proxies was documented by the increase in open habitat ecomorphs during this interval. However, finer grained analysis demonstrated considerable variability in ecomorph frequencies over time, suggesting that substantial short-term variability is masked when grouping samples by member. The hominin genera Australopithecus, Homo, and Paranthropus are associated with a range of ecomorphs, indicating that all three genera were living in temporally variable and heterogeneous landscapes. Australopithecus finds were predominantly associated with lower frequencies of open habitat ecomorphs, and high frequencies of heavy cover ecomorphs, perhaps indicating a more woodland focus for this genus

Exploring morphological generality in the Old World monkey postcranium using an ecomorphological framework

Nearly all primates are ecologically dependent on trees but they are nonetheless found in an enormous range of habitats, from highly xeric environments to dense rainforest. Most primates have a relatively ‘generalised’ skeleton, enabling locomotor flexibility and facilitating other crucial functions, such as manual foraging and grooming. In this paper we explore associations between habitat, locomotion and morphology in the forelimbs of cercopithecids (Old World monkeys), contextualising their skeletal ecomorphological patterns with those of other mammals, and complementing functional morphological analyses with phylogenetic comparative techniques. We investigate the ecomorphological signals present in the generalised primate postcranium, and how an ancestral arboreal ‘bauplan’ might be modified to incorporate terrestriality or exploit distinct arboreal substrates. Analysis of ecomorphological variation in guenons indicates that terrestrial Chlorocebus species retain core elements of a general guenon form, with modifications for terrestriality that vary by species. Adaptation to different modes of arboreality has also occurred in Cercopithecus. The considerable morphological similarity in the guenons sampled emphasises the importance of generality in the primate postcranium – much forelimb variation appears to have emerged stochastically, with a smaller number of traits having a strong functional signal. Analysis of a broader sample of cercopithecids and comparison with felids, suids and bovids indicates that although the cercopithecid humerus has functional morphological signals that enable specimens to be assigned with a reasonable degree of certainty to habitat groups, there is considerable overlap in the specimens assigned to each habitat group. This probably reflects ecological dependence on trees, even in predominantly terrestrial species, as well as the multiple functions of the forelimb and, in some cases, wide geographic distributions that promote intraspecific variation. The use of phylogenetic correction reduced the discriminatory power of the models, indicating that, like allometry, phylogeny contains important ecomorphological information, and should not necessarily be factored out of analyses

Orangutans venture out of the rainforest and into the Anthropocene

Conservation benefits from understanding how adaptability and threat interact to determine a taxon’s vulnerability. Recognizing how interactions with humans have shaped taxa such as the critically endangered orangutan (Pongo spp.) offers insights into this relationship. Orangutans are viewed as icons of wild nature, and most efforts to prevent their extinction have focused on protecting minimally disturbed habitat, with limited success. We synthesize fossil, archeological, genetic, and behavioral evidence to demonstrate that at least 70,000 years of human influence have shaped orangutan distribution, abundance, and ecology and will likely continue to do so in the future. Our findings indicate that orangutans are vulnerable to hunting but appear flexible in response to some other human activities. This highlights the need for a multifaceted, landscape-level approach to orangutan conservation that leverages sound policy and cooperation among government, private sector, and community stakeholders to prevent hunting, mitigate human-orangutan conflict, and preserve and reconnect remaining natural forests. Broad cooperation can be encouraged through incentives and strategies that focus on the common interests and concerns of different stakeholders. Orangutans provide an illustrative example of how acknowledging the long and pervasive influence of humans can improve strategies to preserve biodiversity in the Anthropocene