The palaeoecology of the Upper Ndolanya Beds at Laetoli,Tanzania

The palaeoecology of the fauna from the Ndolanya Beds, Laetoli, Tanzania, has been analysed to reconstruct the environment of this 2.6 Ma site. Community profiles have been constructed in relation to three variables that carry ecological meaning: body weight, locomotor adaptations and feeding preferences. Comparing the similarities and differences in the structure of the fossil faunas with those of modern environments allows us to draw inferences about palaeoenvironmental conditions, and this is based on a comparative dataset of 15 modern environments (44 localities) covering a wide range of climatic and ecological conditions across Asia, Africa and Central America. In addition, 16 fossil sites in East and South Africa have been analysed in the same way, and both sets of comparative data have been used as the basis for comparison with an ecological diversity analysis of the fauna from the Upper Ndolanya Beds. The Ndolanya fauna is characterized by a predominance of medium to large sized terrestrial and herbivorous species.There is evidence of taphonomic bias that eliminated many of the smaller species. A comparison of multivariate analyses of 23 selected modern localities conducted both with and without the small species included, indicates that the loss of these species does not adversely influence the results of an ecological diversity analysis. The evidence suggests that at the time of the deposition of the Ndolanya Beds the Laetoli region was a semi-arid bushland. This is considerably drier and more open than is suggested for the earlier Laetolil Beds.     

Bovid postcranial ecomorphological survey of the Laetoli paleoenvironment

Here we report on a bovid postcranial ecomorphological survey of the fossil assemblages from the Plio-Pleistocene site of Laetoli, Tanzania. A global sample of extant bovids (n=205), cervids (n=14), and tragulids (n=5) from seven known habitat types constitutes the comparative data set. All long bones, carpals, tarsals, and phalanges were measured. Discriminant function analyses (DFA) were conducted in order to evaluate the ability of each element to accurately predict habitat affiliation. The baseline of chance accuracy for DFAs (i.e., the percentage of correct predictions that can be expected when habitat assignments are randomized) served as the cut-off point between good and bad habitat predictors. A total of 22 elements yielded percentages of correct classification over the baseline of accuracy, and these were extended to the Laetoli fossil assemblages. Summaries of the number of specimens predicted to belong to each habitat type were used to reconstruct the paleoenvironment. The results indicate that, at the time of the deposition of the Laetolil Beds, the area had heavy woodland-bushland cover with some lighter tree and bush cover and grass available. These results lend strong support to recent suggestions that the area was on the more wooded end of the habitat spectrum, contra initial conclusions that it represented a mosaic of more open habitats. The results also indicate that, during the deposition of the Ndolanya Beds, the environment had become more open and the grassland component of the environment had increased significantly. Light woodland-bushland and an abundance of grass cover dominated the landscape, although tracts of land with denser vegetation likely existed. This conclusion agrees with earlier suggestions that the area was a semiarid bushland.     

Fluid–structure interaction modeling of compliant aortic valves using the lattice Boltzmann CFD and FEM methods

Biomechanics and Modeling in Mechanobiology - The lattice Boltzmann method (LBM) has been increasingly used as a stand-alone CFD solver in various biomechanical applications. This study proposes a...     

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.