No abstract

Hypotheses regarding patterns of stress, strain and deformation in the craniofacial skeleton are central to adaptive explanations for the evolution of primate craniofacial form. The complexity of craniofacial skeletal morphology makes it difficult to evaluate these hypotheses with in vivo bone strain data. In this paper, new in vivo bone strain data from the intraorbital surfaces of the supraorbital torus, postorbital bar and postorbital septum, the anterior surface of the postorbital bar, and the anterior root of the zygoma are combined with published data from the supraorbital region and zygomatic arch to evaluate the validity of a finite-element model (FEM) of a macaque cranium during mastication. The behavior of this model is then used to test hypotheses regarding the overall deformation regime in the craniofacial haft of macaques. This FEM constitutes a hypothesis regarding deformation of the facial skeleton during mastication. A simplified verbal description of the deformation regime in the macaque FEM is as follows. Inferior bending and twisting of the zygomatic arches about a rostrocaudal axis exerts inferolaterally directed tensile forces on the lateral orbital wall, bending the wall and the supraorbital torus in frontal planes and bending and shearing the infraorbital region and anterior zygoma root in frontal planes. Similar deformation regimes also characterize the crania of Homo and Gorilla under in vitro loading conditions and may be shared among extant catarrhines. Relatively high strain magnitudes in the anterior root of the zygoma suggest that the morphology of this region may be important for resisting forces generated during feeding.

Attempts to establish relationships between mandibular morphology and either traditional dietary categories or geometric and material properties of primate diets have not been particularly successful. Using our conceptual framework of the feeding factors impacting mandibular morphology, we argue that this is because dietary categories and food geometric and material properties affect mandibular morphology only through intervening variables that are currently poorly understood, i.e., feeding behavior, mandibular loading, and stress and strain regimes. Our studies of 3-dimensional jaw kinematics in macaques and capuchins show that, although jaw movement profiles during chewing are affected by food material properties and species-level effects, patterns of jaw movements in these two species are broadly similar. However, because mandibular loading, stress, and strain regimes are determined by interactions between feeding behavior (such as jaw kinematics) and mandibular morphology, it is difficult to say whether these similarities in chewing kinematics also mean similarities in loading, stress, and strain. Comparative analyses of the scaling of daily feeding time and chew cycle duration reveal only weak support for the hypothesis that larger primates chew more than smaller primates. Consideration of these results suggests that better data are needed on the relationship between dietary categories, food material and geometric properties, the amount of time/cycles associated with different feeding behaviors (ingestion, premolar biting, mastication), and mandible stress and strain patterns if we are to understand fully relationships between mandibular morphology and diet in primates.

modes of bats vary widely among families, so we focused on a single family, the Pteropodidae. This family consists of ca. 186 species distributed throughout the paleotropics (Wilson and Reeder, 2005) and is characterized by fruit and nectar-feeding, non-echolocating Accepted 26 None of the bats in our study flew at constant speed, so we used multiple regression to isolate the changes in wing kinematics that correlated with changes in flight speed, horizontal acceleration and vertical acceleration. We uncovered several significant trends that were consistent among species. Our results demonstrate that for medium-to large-sized bats, the ways that bats modulate their wing kinematics to produce thrust and lift over the course of a wingbeat cycle are independent of body size. Supplementary material available online at

Feeding is the set of behaviors whereby organisms acquire and process the energy required for survival and reproduction. Thus, feeding system morphology is presumably subject to selection to maintain or improve feeding performance. Relationships among feeding system morphology, feeding behavior, and diet not only explain the morphological diversity of extant primates, but can also be used to reconstruct feeding behavior and diet in fossil taxa. Dental morphology has long been known to reflect aspects of feeding behavior and diet but strong relationships of craniomandibular morphology to feeding behavior and diet have yet to be defined.

Experimental measurements and analysis of the flight of bats are presented, including kinematic analysis of high-speed stereo videography of straight and turning flight, and measurements of the wake velocity field behind the bat. The kinematic data reveal that, at relatively slow flight speeds, wing motion is quite complex, including a sharp retraction of the wing during the upstroke and a broad sweep of the partially extended wing during the downstroke. The data also indicate that the flight speed and elevation are not constant, but oscillate in synchrony with both the horizontal and vertical movements of the wing. PIV measurements in the transverse (Trefftz) plane of the wake indicate a complex 'wake vortex' structure dominated by a strong wing tip vortex shed from the wing tip during the downstroke and either the wing tip or a more proximal joint during the upstroke. Data synthesis of several discrete realizations suggests a 'cartoon' of the wake structure during the entire wing beat cycle. Considerable work remains to be done to confirm and amplify these results.

No abstract

No abstract