The relationship between body shape, body size and locomotor mode in extant lepidosaurs

Despite historic work, the mechanisms and evolutionary drivers associated with the adoption of a facultatively bipedal locomotor mode in extant lepidosaurs are unclear. Recent work has provided insights into the biomechanical triggers of bipedal locomotion, but the associated anatomies are yet to be fully understood, particularly with regard to body size across Lepidosauria. Using a dataset derived from museum specimens, representing a range of lepidosaur body shapes, we highlight the differences between obligate quadrupeds and facultative bipeds within this group and demonstrate the value of non-caudal skeletal material in identifying facultative bipeds using osteology alone. We use multiple statistical approaches to identify trends across locomotor modes relative to body size. Body size has a significant effect upon body proportions across the two locomotor modes, especially in the hindlimbs. Forelimbs lengths do not differ significantly across locomotor modes for animals of similar body size, but distal hindlimbs are significantly longer in facultative bipeds. Interestingly, femoral length does not differ across locomotor modes of a similar body size. Our findings contrast with historical tropes, and are significant for future work attempting to identify the factors driving the evolution of a facultatively bipedal locomotor mode in Lepidosauria

Paleobiology of titanosaurs: reproduction, development, histology, pneumaticity, locomotion and neuroanatomy from the South American fossil record

Fil: García, Rodolfo A.. Instituto de Investigación en Paleobiología y Geología. Museo Provincial Carlos Ameghino. Cipolletti; ArgentinaFil: Salgado, Leonardo. Instituto de Investigación en Paleobiología y Geología. General Roca. Río Negro; ArgentinaFil: Fernández, Mariela. Inibioma-Centro Regional Universitario Bariloche. Bariloche. Río Negro; ArgentinaFil: Cerda, Ignacio A.. Instituto de Investigación en Paleobiología y Geología. Museo Provincial Carlos Ameghino. Cipolletti; ArgentinaFil: Carabajal, Ariana Paulina. Museo Carmen Funes. Plaza Huincul. Neuquén; ArgentinaFil: Otero, Alejandro. Museo de La Plata. Universidad Nacional de La Plata; ArgentinaFil: Coria, Rodolfo A.. Instituto de Paleobiología y Geología. Universidad Nacional de Río Negro. Neuquén; ArgentinaFil: Fiorelli, Lucas E.. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica. Anillaco. La Rioja; Argentin

Editorial: Nature-inspired flight - beyond the leap

Whereas humans can outrun horses over large distances (BBC News 2004), because of their adaptation for endurance (Bramble and Lieberman 2004), their swimming performance is mediocre compared to that of tuna and sailfish, and flight is impossible. No wonder that the flight of animals and plants such as birds, bats, insects and autorotating seeds has long since inspired mankind to invent its own flying machines. Just over 100 years old, human-designed aircraft have barely taken off on an evolutionary timescale. Recently engineers have stepped up by designing small unmanned air vehicles at the scale of flying animals and plant seeds that innovate by mimicking nature's successful design principles for highly maneuverable and efficient flight. Here we feature current biomechanics flight research and bioinspired design crème. By featuring the work in nine papers of both fields side-by-side, and motivating the authors to speculate how their work could inspire the other group, we hope to stimulate future interactions between these adjacent fields of research. Here, we provide an overview of the authors' research and designs accompanied by their perspectives on the value of their work for the adjacent fiel

Scaling of elastic energy storage in mammalian limb tendons: do small mammals really lose out?

It is widely believed that elastic energy storage is more important in the locomotion of larger mammals. This is based on: (a) comparison of kangaroos with the smaller kangaroo rat; and (b) calculations that predict that the capacity for elastic energy storage relative to body mass increases with size. Here we argue that: (i) data from kangaroos and kangaroo rats cannot be generalized to other mammals; (ii) the elastic energy storage capacity relative to body mass is not indicative of the importance of elastic energy to an animal; and (iii) the contribution of elastic energy to the mechanical work of locomotion will not increase as rapidly with size as the mass-specific energy storage capacity, because larger mammals must do relatively more mechanical work per stride. We predict how the ratio of elastic energy storage to mechanical work will change with size in quadrupedal mammals by combining empirical scaling relationships from the literature. The results suggest that the percentage contribution of elastic energy to the mechanical work of locomotion decreases with size, so that elastic energy is more important in the locomotion of smaller mammals. This now needs to be tested experimentally

Functional diversification within and between muscle synergists during locomotion

Locomotion arises from the complex and coordinated function of limb muscles. Yet muscle function is dynamic over the course of a single stride and between strides for animals moving at different speeds or on variable terrain. While it is clear that motor unit recruitment can vary between and within muscles, we know little about how work is distributed within and between muscles under in vivo conditions. Here we show that the lateral gastrocnemius (LG) of helmeted guinea fowl (Numida meleagris) performs considerably more work than its synergist, the medial gastrocnemius (MG) and that the proximal region of the MG (pMG) performs more work than the distal region (dMG). Positive work done by the LG was approximately twice that of the proximal MG when the birds walked at 0.5 m s−1, and four times when running at 2.0 m s−1. This is probably due to different moments at the knee, as well as differences in motor unit recruitment. The dMG performed less work than the pMG because its apparent dynamic stiffness was greater, and because it exhibited a greater recruitment of slow-twitch fibres. The greater compliance of the pMG leads to increased stretch of its fascicles at the onset of force, further enhancing force production. Our results demonstrate the capacity for functional diversity between and within muscle synergists, which increases with changes in gait and speed