Palaeoecology ofKolpochoerus heseloni (= K. limnetes): a multiproxy approach

Ecomorphology of the cervid intermediate phalanx and its implications for palaeoenvironmental reconstruction

This paper reports on newly developed ecomorphological models for the cervid intermediate phalanx. Using a geometric morphometric approach, we quantitatively assess the overall gracility of the bone, the depth and concavity of the proximal articulation and the roundness and symmetry of the distal articulation in the intermediate phalanx, to establish relationships between morphology, locomotor behavior and environment. The morphology of the phalanx was found to vary along a gradient from gracile phalanges with shallow proximal articulations in forms adapted to yielding substrate, to robust phalanges with deeper proximal articulations in taxa adapted to firm substrate. Phylogeny and allometry are accounted for using regressions and phylogenetic comparative methods. Although the results indicate phylogeny explains part of the morphological variation, overall the shape of the intermediate phalanx appears mainly driven by differences in function. Consequently, this element promises to be a useful palaeoenvironmental proxy that can be applied on fossil assemblages with cervid remains.

Anatomical adaptions of pits in two types of ray parenchyma cells in Populus tomentosa during the xylem differentiation

Pits in ray parenchyma cells are important to understand the functional anatomy of the ray parenchyma network in the xylem but have been less studied. Herein, pits in two types of ray parenchyma cells, contact cells and isolation cells, across different developmental stages were qualitatively studied using 48-year-old Populus tomentosa trees. The timing of differentiation and death was determined by histochemical staining and polarized light microscopy. The dimension, shape and density of pits as well as cell wall thickness were measured using SEM and optical microscopy images of semi-thin radial sections and macerated ray parenchyma cells, and analyzed by multi-factor analyses of variance. Results showed that secondary wall thickening and lignification of contact cells begun near the cambium, contrarily those of isolation cells have started until the transition zone. But even in the sapwood, contact cell walls were still much thinner than isolation cell walls. Moreover, district anatomical adaptions of pits during the xylem differentiation were present between horizontal walls and tangential walls, between contact cells and isolation cells. Ray pits were simple to slightly bordered, whereas sieve-like pits were only shown on tangential walls of isolation cells. Pit density of horizontal walls was similar between contact cells and isolation cells, nevertheless greater pits were present on tangential walls, especially for isolation cells. In addition, pits of ray parenchyma cells in the heartwood were smaller and more bordered than those in the sapwood, particularly on the horizontal walls. Moreover, isolation cells had pits with the smaller dimensions, greater pits on the tangential walls, more bordered pits on horizontal walls, as well as longer and narrower cell morphology with much thicker cell walls than contact cells. To a certain extent, all these anatomical adaptations were developed to ensure distinct functions of the two types of ray parenchyma cells in the xylem and finally to support tree growth in demand.

Ecomorphology of the cervid calcaneus as a proxy for paleoenvironmental reconstruction

This study presents new ecomorphological models for the cervid calcaneus that can be used to make predictions about the nature of ancient environments. Using geometric morphometrics to quantitatively assess the length of the articular surface supporting the malleolus, the length and orientation of the tuber calcanei, and the position of the articular facets, we aimed to establish correlations between morphological traits, locomotor behavior, and environmental parameters in extant cervids. The morphology of the calcaneus was found to primarily vary with locomotor strategy and habitat, along a continuum from habitats with an open vegetation structure to habitats with a closed vegetation structure. Confounding factors, including sexual dimorphism, allometry, and phylogeny were accounted for using Principal Component Analysis, regressions and phylogenetic comparative methods. The results of our analyses suggested that these factors did not substantially obscure habitat predictions. As such, the calcaneus provides a valuable proxy for paleoenvironmental reconstruction that is broadly applicable to Quaternary fossil assemblages with a sufficiently large sample of cervids.

The case of the grass-eating suids in the Plio-Pleistocene Turkana Basin: 3D dental topography in relation to diet in extant and fossil pigs

Two separate subfamilies of Plio-Pleistocene African pigs (suids) consecutively evolved hypsodont and horizodont molars with flat occlusal surfaces, commonly interpreted as an adaptive trait to a grazing diet, similar to that of the present warthogs (Phacochoerus spp.). To investigate this in detail, we studied the 3D-dental topography of fossil specimens from the Turkana Basin, using geographic information systems-based methods. To establish baselines for interpretation of the Turkana Basin suids, topography of third molars of extant suids with known diets were analyzed: grazing warthog (Phacochoerus africanus), herbivorous mixed-feeder forest hog (Hylochoerus meinertzhageni), omnivorous generalist wild boar (Sus scrofa), omnivorous fruit and tuber eater bush pig (Potamochoerus spp.), and omnivorous fruit eater babirusa (Babyrousa spp.) In addition, we analyzed supposedly browsing Miocene suids, Listriodon spp. The same topographic measures were applied to Plio-Pleistocene specimens from the Turkana Basin, Kenya: Notochoerus euilus, Notochoerus scotti, Kolpochoerus heseloni, and Metridiochoerus andrewsi. With some differences between techniques, 3D-dental topography analysis of extant suid molars mostly predicts the dietary differences between the species correctly. The grazing P. africanus differs from both the omnivorous suids and the herbivorous mixed-feeder H. meinertzhageni in all except one metrics. The omnivorous mostly tropical suids, Potamochoerus and Babyrousa, primarily differ from the generalist, S. scrofa, in the orientation patch count analysis, showing higher occlusal complexity in the latter. Although, there might be significant gaps between the morphological changes and the ecological changes, we conclude that based on comparison of dental topography with the present-day suids, N. scotti and M. andrewsi were most likely highly specialized grazers, while N. euilus and K. heseloni retained more of their ancestral, omnivorous heritage, but consumed grasses more than the extant omnivorous suids. RESEARCH HIGHLIGHTS: Dental topography can predict different diets in present-day wild pigs. The Plio-Pleistocene pigs in the Turkana Basin had dental topography mostly similar to extant grazing warthog, although some species also had resemblances to omnivorous forest pigs.

Dental microwear texture analysis of Pliocene Suidae from Hadar and Kanapoi in the context of early hominin dietary breadth expansion

Stable carbon isotope studies suggest that early hominins may have diversified their diet as early as 3.76 Ma. Early Pliocene hominins, including Australopithecus anamensis, had diets that were dominated by C₃ resources while Late Pliocene hominins, including Australopithecus afarensis-a putative descendant of A. anamensis-had diets that included both C₃ and C₄ resources. It has been hypothesized that the expansion of C₄ grasslands in eastern Africa during the Pliocene could have prompted hominins to incorporate C₄ resources in their diets. However, dental microwear analyses suggest that diet diversification did not involve changes in the mechanical properties of the foods consumed. To provide contextual and comparative information on this issue, the diet of suids from the A. anamensis site of Kanapoi and the A. afarensis site of Hadar is investigated. Using dental microwear texture analyses, it is shown that despite significant dietary overlap, there is evidence for dietary niche partitioning among suids. Based on comparisons with the diet of extant African suids, it is inferred that Nyanzachoerus pattersoni (n = 21) was a mixed feeder, Nyanzachoerus jaegeri (n = 4) and Notochoerus euilus (n = 61) were habitual grazers, and Kolpochoerus afarensis (n = 34) had a broad diet that included hard brittle foods and underground resources. The dental microwear of Ny. pattersoni and Ny. jaegeri/No. euilus do not differ significantly between Kanapoi and Hadar. Most differences are driven by K. afarensis, a suid absent at Kanapoi but present at Hadar. Food availability probably differed between Hadar and Kanapoi, and it is likely that A. afarensis did not exploit some of the foods (e.g., underground resources) consumed by suids. It is hypothesized that despite the incorporation of C₄ resources in the diet, a significant dietary change towards flexible diets in the hominin lineage had yet to come.

Contextualising primate origins--an ecomorphological framework

Ecomorphology - the characterisation of the adaptive relationship between an organism's morphology and its ecological role - has long been central to theories of the origin and early evolution of the primate order. This is exemplified by two of the most influential theories of primate origins: Matt Cartmill's Visual Predation Hypothesis, and Bob Sussman's Angiosperm Co-Evolution Hypothesis. However, the study of primate origins is constrained by the absence of data directly documenting the events under investigation, and has to rely instead on a fragmentary fossil record and the methodological assumptions inherent in phylogenetic comparative analyses of extant species. These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form-function relationships are critical for the functional interpretation of the morphology of extinct species. Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. This contribution will review current perspectives on the origin and early evolution of primates, paying particular attention to their phylogenetic (including cladistic relationships and character evolution) and environmental (including chronology, geography, and physical environments) contextualisation, before attempting an up-to-date ecomorphological synthesis of primate origins.

Ecological continuity between Lower and Upper Bed II, Olduvai Gorge, Tanzania

The sediments of Bed II at Olduvai Gorge, Tanzania, have received less scientific scrutiny than Bed I strata, likely due to the lower density of fossil hominins in the younger layers. Nevertheless, Bed II provides important contextual information about changes over time in early hominin environments. Mammal fossils from Bed II are separated into older and younger faunas by a regional disconformity under which lies an aeolian tuff, the Lemuta Member, dated to ∼1.74 Ma (millions of years ago). Differences between the faunal communities above and below the Lemuta Member have been previously noted and interpreted as evidence for distinct environmental change. Here, we investigate the palaeoecological conditions that characterised the transition between older and younger Bed II sites via analysis of their mammalian community ecological niche exploitation profiles, comparing these to known modern habitats. We present a comprehensive species list for both Bed II faunas. An initial correspondence analysis points to palaeoecological differences in pre- and post-Lemuta Member assemblages, although neither is representative of a forest habitat. When taphonomic differences in body mass profiles are taken into account, however, ecological differences appear far less important. Based on a resampling procedure to generate modern locality data with body mass profiles similar to the Bed II faunas, discriminant correspondence analyses liken both fossil assemblages to modern woodland habitats, with Lower Bed II having some affinity to floodplain and marshy woodlands, likely related to the presence of the Olduvai palaeolake in this stratigraphic interval. A comparison of the Bed II faunas to each other suggests that their differences could reasonably be sampled from within a single modern habitat. Although additional evidence points to an increase in aridity subsequent to the Lemuta Member, the importance of woodland habitats throughout Bed II is clear.