Testing hypotheses of skull function with comparative finite element analysis: three methods reveal contrasting results.

Comparative finite element analysis involves standardising aspects of models to test equivalent loading scenarios across species. However, regarding feeding biomechanics of the vertebrate skull, what is considered "equivalent" can depend on the hypothesis. Using 13 diversely-shaped skulls of marsupial bettongs and potoroos (Potoroidae), we demonstrate that scaling muscle forces to standardise specific aspects of biting mechanics can produce clearly opposing comparisons of stress or strain that are differentially suited to address specific kinds of hypotheses.

Unexpectedly uneven distribution of functional trade-offs explains cranial morphological diversity in carnivores.

Functional trade-offs can affect patterns of morphological and ecological evolution as well as the magnitude of morphological changes through evolutionary time. Using morpho-functional landscape modelling on the cranium of 132 carnivore species, we focused on the macroevolutionary effects of the trade-off between bite force and bite velocity. Here, we show that rates of evolution in form (morphology) are decoupled from rates of evolution in function.

Raptorial appendages of the Cambrian apex predator are built for soft prey and speed.

The stem-group euarthropod is one of the largest Cambrian animals and is often considered the quintessential apex predator of its time. This radiodont is commonly interpreted as a demersal hunter, responsible for inflicting injuries seen in benthic trilobites. However, controversy surrounds the ability of to use its spinose frontal appendages to masticate or even manipulate biomineralized prey.

Homo sapiens and Neanderthals share high cerebral cortex integration into adulthood.

There is controversy around the mechanisms that guided the change in brain shape during the evolution of modern humans. It has long been held that different cortical areas evolved independently from each other to develop their unique functional specializations. However, some recent studies suggest that high integration between different cortical areas could facilitate the emergence of equally extreme, highly specialized brain functions.

Biomechanical analyses of pterygotid sea scorpion chelicerae uncover predatory specialisation within eurypterids.

Eurypterids (sea scorpions) are extinct aquatic chelicerates. Within this group, members of Pterygotidae represent some of the largest known marine arthropods. Representatives of this family all have hypertrophied, anteriorly-directed chelicerae and are commonly considered Silurian and Devonian apex predators.

The extinct shark was a transoceanic superpredator: Inferences from 3D modeling.

Although shark teeth are abundant in the fossil record, their bodies are rarely preserved. Thus, our understanding of the anatomy of the extinct remains rudimentary. We used an exceptionally well-preserved fossil to create the first three-dimensional model of the body of this giant shark and used it to infer its movement and feeding ecology.

Earliest evidence for fruit consumption and potential seed dispersal by birds.

The Early Cretaceous diversification of birds was a major event in the history of terrestrial ecosystems, occurring during the earliest phase of the Cretaceous Terrestrial Revolution, long before the origin of the bird crown-group. Frugivorous birds play an important role in seed dispersal today. However, evidence of fruit consumption in early birds from outside the crown-group has been lacking.

Trapped in the morphospace: The relationship between morphological integration and functional performance.

The evolution of complex morphological structures can be characterized by the interplay between different anatomical regions evolving under functional integration in response to shared selective pressures. Using the highly derived humeral morphology of talpid moles as a model, here we test whether functional performance is linked to increased levels of evolutionary integration between humerus subunits and, if so, what the strength is of the relationship. Combining two-dimensional geometric morphometrics, phylogenetic comparative methods, and functional landscape modeling, we demonstrate that the high biomechanical performance of subterranean moles' humeri is coupled with elevated levels of integration, whereas taxa with low-performance values show intermediate or low integration.

More Challenging Diets Sustain Feeding Performance: Applications Toward the Captive Rearing of Wildlife.

The rescue and rehabilitation of young fauna is of substantial importance to conservation. However, it has been suggested that incongruous diets offered in captive environments may alter craniofacial morphology and hinder the success of reintroduced animals. Despite these claims, to what extent dietary variation throughout ontogeny impacts intrapopulation cranial biomechanics has not yet been tested.

Biomechanical analyses of Cambrian euarthropod limbs reveal their effectiveness in mastication and durophagy.

Durophagy arose in the Cambrian and greatly influenced the diversification of biomineralized defensive structures throughout the Phanerozoic. Spinose gnathobases on protopodites of Cambrian euarthropod limbs are considered key innovations for shell-crushing, yet few studies have demonstrated their effectiveness with biomechanical models. Here we present finite-element analysis models of two Cambrian trilobites with prominent gnathobases- and -and compare these to the protopodites of the Cambrian euarthropod and the modern American horseshoe crab, .

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls.

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterize the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using three-dimensional geometric morphometrics and virtual dissections.

Quantitatively assessing mekosuchine crocodile locomotion by geometric morphometric and finite element analysis of the forelimb.

Morphological shifts observed in the fossil record of a lineage potentially indicate concomitant shifts in ecology of that lineage. Mekosuchine crocodiles of Cenozoic Australia display departures from the typical eusuchian body-plan both in the cranium and postcranium. Previous qualitative studies have suggested that these crocodiles had a more terrestrial habitus than extant crocodylians, yet the capacity of mekosuchine locomotion remains to be tested.

Morphometric analysis of the hominin talus: Evolutionary and functional implications.

The adoption of bipedalism is a key benchmark in human evolution that has impacted talar morphology. Here, we investigate talar morphological variability in extinct and extant hominins using a 3D geometric morphometric approach. The evolutionary timing and appearance of modern human-like features and their contributions to bipedal locomotion were evaluated on the talus as a whole, each articular facet separately, and multiple combinations of facets.

The influence of mobility strategy on the modern human talus.

Objectives: The primate talus is known to have a shape that varies according to differences in locomotion and substrate use. While the modern human talus is morphologically specialized for bipedal walking, relatively little is known on how its morphology varies in relation to cultural and environmental differences across time. Here we compare tali of modern human populations with different subsistence economies and lifestyles to explore how cultural practices and environmental factors influence external talar shape.

Head to head: the case for fighting behaviour in using finite-element analysis.

The largest antlers of any known deer species belonged to the extinct giant deer . It has been argued that their antlers were too large for use in fighting, instead being used only in ritualized displays to attract mates. Here, we used finite-element analysis to test whether the antlers of could have withstood forces generated during fighting.

Impact of transition to a subterranean lifestyle on morphological disparity and integration in talpid moles (Mammalia, Talpidae).

Background: Understanding the mechanisms promoting or constraining morphological diversification within clades is a central topic in evolutionary biology. Ecological transitions are of particular interest because of their influence upon the selective forces and factors involved in phenotypic evolution. Here we focused on the humerus and mandibles of talpid moles to test whether the transition to the subterranean lifestyle impacted morphological disparity and phenotypic traits covariation between these two structures.

Evolution of the vomer and its implications for cranial kinesis in Paraves.

Most living birds exhibit cranial kinesis-movement between the rostrum and braincase-in which force is transferred through the palatal and jugal bars. The palate alone distinguishes the Paleognathae from the Neognathae, with cranial kinesis more developed in neognaths. Most previous palatal studies were based on 2D data and rarely incorporated data from stem birds despite great interest in their kinetic abilities.

Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress.

Reconstructing the detailed dietary behaviour of extinct hominins is challenging-particularly for a species such as Australopithecus africanus, which has a highly variable dental morphology that suggests a broad diet. The dietary responses of extinct hominins to seasonal fluctuations in food availability are poorly understood, and nursing behaviours even less so; most of the direct information currently available has been obtained from high-resolution trace-element geochemical analysis of Homo sapiens (both modern and fossil), Homo neanderthalensis and living apes. Here we apply high-resolution trace-element analysis to two A.

Morphological integration affects the evolution of midline cranial base, lateral basicranium, and face across primates.

Objectives: The basicranium and face are two integrated bony structures displaying great morphological diversity across primates. Previous studies in hominids determined that the basicranium is composed of two independent modules: the midline basicranium, mostly influenced by brain size, and the lateral basicranium, predominantly associated with facial shape. To better assess how morphological integration impacts the evolution of primate cranial shape diversity, we test to determine whether the relationships found in hominids are retained across the order.

Raptor talon shape and biomechanical performance are controlled by relative prey size but not by allometry.

Most birds of prey (raptors), rely heavily on their talons for capturing prey. However, the relationship between talon shape and the ability to take prey is poorly understood. In this study we investigate whether raptor talons have evolved primarily in response to adaptive pressures exerted by different dietary demands, or if talon morphology is largely constrained by allometric or phylogenetic factors.

Computational biomechanical analyses demonstrate similar shell-crushing abilities in modern and ancient arthropods.

The biology of the American horseshoe crab, , is well documented-including its dietary habits, particularly the ability to crush shell with gnathobasic walking appendages-but virtually nothing is known about the feeding biomechanics of this iconic arthropod. is also considered the archetypal functional analogue of various extinct groups with serial gnathobasic appendages, including eurypterids, trilobites and other early arthropods, especially from the mid-Cambrian (508 Myr) Burgess Shale of Canada. Exceptionally preserved specimens of show evidence suggestive of durophagous (shell-crushing) tendencies-including thick gnathobasic spine cuticle and shelly gut contents-but the masticatory capabilities of this fossil species have yet to be compared with modern durophagous arthropods.

Comparative Three-Dimensional Moment Arm Analysis of the Sauropod Forelimb: Implications for the Transition to a Wide-Gauge Stance in Titanosaurs.

The evolution of extraordinarily large size among Sauropoda was associated with a number of biomechanical adaptations. Changes in muscle moment arms undoubtedly accompanied these adaptations, but since muscles rarely fossilize, our ability to understand them has been restricted. Here, we use three-dimensional (3D) musculoskeletal modeling to reconstruct and quantitatively assess leverage of forelimb muscles in the transition from the narrow-gauge stance of basal sauropods to a wide-gauge stance in titanosaurs.

Three-Dimensional Musculoskeletal Modeling of the Sauropodomorph Hind Limb: The Effect of Postural Change on Muscle Leverage.

The biomechanical constraints for life at massive size can be directly observed in the evolutionary history of sauropodomorph dinosaurs. Members of this lineage underwent a number of major postural transitions as they increased in size from relatively small bipedal dinosaurs to massive titanosaurs that include the largest terrestrial animals of all time. To better understand the impact of gigantic size on the biomechanics of sauropods, we used three-dimensional musculoskeletal modeling to investigate how hind limb musculature was affected, first by the development of a quadrupedal stance from a bipedal one, and later in the transition from a narrow-gauge to a wide-gauge stance.

A new, three-dimensional geometric morphometric approach to assess egg shape.

This paper proposes a new methodology to quantify patterns of egg shape variation using geometric morphometrics of three-dimensional landmarks captured on digitally reconstructed eggshells and demonstrates its performance in capturing shape variation at multiple biological levels. This methodology offers unique benefits to complement established linear measurement or two-dimensional (2D) contour profiling techniques by (i) providing a more precise representation of eggshell curvature by accounting for variation across the entire surface of the egg; (ii) avoids the occurrence of correlations from combining multiple egg shape features; (iii) avoids error stemming from projecting a highly-curved three-dimensional (3D) object into 2D space; and (iv) enables integration into 3D workflows such as finite elements analysis. To demonstrate, we quantify patterns of egg shape variation and estimate morphological disparity at multiple biological levels, within and between clutches and among species of four passerine species of different lineages, using volumetric dataset obtained from micro computed tomography.

The biomechanics of foraging determines face length among kangaroos and their relatives.

Increasing body size is accompanied by facial elongation across a number of mammalian taxa. This trend forms the basis of a proposed evolutionary rule, cranial evolutionary allometry (CREA). However, facial length has also been widely associated with the varying mechanical resistance of foods.