The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from <10 kg hatchlings to >6000 adults in <20 years. These raise fascinating questions about the morphological transformations involved, peak rates, and scaling of limb muscle sizes as well body's centre mass that could have influenced ontogenetic locomotion T. rex. Here we address these using three-dimensionally scanned computer models four large, well-preserved fossil specimens a putative juvenile...

Abstract Inertial properties of animal bodies and segments are critical input parameters for biomechanical analysis standing moving, thus important paleobiological inquiries into the broader behaviors, ecology evolution extinct taxa such as dinosaurs. But how accurately can these be estimated? Computational modeling was used to estimate inertial including mass, density, center mass (COM) extant crocodiles (adult juvenile Crocodylus johnstoni ) birds ( Gallus gallus ; junglefowl broiler...

Crocodylians exhibit a fascinating diversity of terrestrial gaits and limb motions that remain poorly described are great importance to understanding their natural history evolution. Their musculoskeletal anatomy is pivotal this yet only qualitative studies muscle-tendon unit exist. The relative masses internal architecture (fascicle lengths physiological cross-sectional areas) muscles the pectoral pelvic limbs American alligators (Alligator mississippiensis Daudin 1801) were recorded for an...

The colossal size and body plan of sauropod dinosaurs are unparalleled in terrestrial vertebrates. However, to date, there have been only limited attempts examine temporal phylogenetic patterns the bauplan. Here, we combine three-dimensional computational models with reconstructions quantify evolution whole-body shape segment properties across radiation. Limitations associated absence soft tissue preservation fossils result large error bars about mean absolute predictions. applying any...

Abstract Ontogenetic information is crucial to understand life histories and represents a true challenge in dinosaurs due the scarcity of growth series available. Mussaurus patagonicus was sauropodomorph dinosaur close origin Sauropoda known from hatchling, juvenile mature specimens, providing sufficiently complete ontogenetic reconstruct general patterns ontogeny. Here, order quantify how body shape its relationship with locomotor stance (quadruped/biped) changed ontogeny, (~1 year old)...

Crocodiles and their kin (Crocodylidae) use asymmetrical (bounding galloping) gaits when moving rapidly. Despite being morphologically ecologically similar, it seems alligators (Alligatoridae) do not. To investigate a possible anatomical basis for this apparent major difference in locomotor capabilities, we measured relative masses internal architecture (fascicle lengths physiological cross-sectional areas) of muscles the pectoral pelvic limbs 40 individuals from six representative species...

Orobates pabsti, a basal diadectid from the lower Permian, is key fossil for understanding of early amniote evolution. Quantitative analysis anatomical information suffers fragmentation bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe steps taken digitally reconstruct MNG 10181, holotype specimen subsequently use digital reconstruction assess body mass, position...

Many of the major locomotor transitions during evolution Archosauria, lineage including crocodiles and birds as well extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling erect modes locomotion involved drastic changes limb anatomy function in several lineages, sauropodomorph dinosaurs. We present biomechanical computer models two extremes Archosauria an analysis joint ranges motion moment arms forelimb...

Biomechanical modeling shows that archosaur leg muscle leverage evolved gradually, yet with a Jurassic pulse of specialization.

The arrangement and physiology of muscle fibres can strongly influence musculoskeletal function whole-organismal performance. However, experimental investigation during in vivo activity is typically limited to relatively few muscles a given system. Computational models simulations the system partly overcome these limitations, by exploring dynamics muscles, tendons other tissues robust quantitative fashion. Here, high-fidelity, 26-degree-of-freedom model was developed hindlimb small ground...

Background One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved lineage leading to birds. Although it well established that high, sustained growth rates and, presumably, high activity levels are ancestral for pterosaurs (clade Ornithodira), other independent lines evidence metabolic rates, locomotor costs, needed. For example, studies have suggested that, because...

Abstract Ornithischia (the ‘bird‐hipped’ dinosaurs) encompasses bipedal, facultative quadrupedal and taxa. Primitive ornithischians were small bipeds, but large body size obligate quadrupedality evolved independently in all major ornithischian lineages. Numerous pelvic hind limb features distinguish from the majority of other non‐avian dinosaurs. However, some these features, notably a retroverted pubis elongate iliac preacetabular process, appeared convergently maniraptoran theropods,...

Comparative analyses of locomotion in tetrapods reveal two patterns stride cycle variability. Tachymetabolic (birds and mammals) have lower inter-cycle variation duration than bradymetabolic (amphibians, lizards, turtles crocodilians). This pattern has been linked to the fact that birds mammals share enlarged cerebella, relatively heavily myelinated Ia afferents, γ-motoneurons their muscle spindles. Both tachymetabolic tetrapod lineages also possess an encapsulated Golgi tendon morphology,...

The three-dimensional anatomy of the ostrich (Struthio camelus) knee (femorotibial, femorofibular, and femoropatellar) joint has scarcely been studied, could elucidate certain mechanobiological properties sesamoid bones. adult is unique in that it double patellae, while another similar ratite bird, emu, none. Understanding why these patellae form what purpose they may serve dually important for future studies on ratites as well understanding characteristics bone development. For this...

Abstract Throughout their 250 Myr history, archosaurian reptiles have exhibited a wide array of body sizes, shapes, and locomotor habits, especially in regard to terrestriality. These features make Archosauria useful clade with which study the interplay between size, shape, behavior, how this may influenced evolution. Here, digital volumetric models 80 taxa are used explore mass properties proportions relate each other posture archosaurs. One-way, nonparametric, multivariate analysis...

Electromyography (EMG) is used to understand muscle activity patterns in animals. Understanding how much variation exists homologous muscles across animal clades during similar behaviours important for evaluating the evolution of functions and neuromuscular control. We compared a range archosaurian species appendicular muscles, including these EMG varied ontogeny phylogeny, reconstruct evolutionary history activation locomotion. electrodes were implanted into turkeys, pheasants, quail,...

Background: One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved lineage leading to birds.Although it well established that high, sustained growth rates and, presumably, high activity levels are ancestral for pterosaurs (clade Ornithodira), other independent lines evidence metabolic rates, locomotor costs, needed.For example, studies have suggested that, because...

Abstract Archosaurian reptiles (including living crocodiles and birds) had an explosive diversification of locomotor form function since the Triassic approximately 250 million years ago. Their limb muscle physiology biomechanics are pivotal to our understanding how their diversity evolution relate function. Muscle contraction velocity, force, power in extinct archosaurs such as early crocodiles, pterosaurs, or non-avian dinosaurs not available from fossil material, but needed for...

Based on our plot in Figure 6, we stated that the data paper support view DME was a reasonable first approximation for modeling growth non-avian dinosaurs.However, several inconsistencies were introduced this plot, fact brought to attention by Myhrvold (2013).Errors include using minimum mass of 9693 kg ''Sue'' instead published 9501 kg, and femoral lengths Kilbourne Makovicky (2010) ones Table 3 paper.An important source ambiguity came light as reviewed data: ''Jane'' specimen's femur,...

The three-dimensional anatomy of the ostrich ( Struthio camelus ) knee (femorotibial, femorofibular, and femoropatellar) joint has scarcely been studied, could elucidate certain mechanobiological properties sesamoid bones. adult is unique in that it double patellae, while another similar ratite bird, emu, none. Understanding why these patellae form what purpose they may serve dually important for future studies on ratites as well understanding characteristics bone development. For this...

The three-dimensional anatomy of the ostrich ( Struthio camelus ) knee (femorotibial, femorofibular, and femoropatellar) joint has scarcely been studied, could elucidate certain mechanobiological properties sesamoid bones. adult is unique in that it double patellae, while another similar ratite bird, emu, none. Understanding why these patellae form what purpose they may serve dually important for future studies on ratites as well understanding characteristics bone development. For this...