Vivian Allen
I am an English postdoc researcher studying locomotion biomechanics in an evolutionary context. My current research project aims to test the hypothesis that the apparent out-competition of Mesozoic Pseudosuchia (crocodiles and their extinct relatives) by the Ornithodira (dinosaurs, pterosaurs and allies) during the Late Triassic extinction event may be partially explained by differences in locomotor performance between the two groups. We are using locomotion data (Electromyography and marker-based biplanar xray kinematics [XROMM]) captured from extant pseudosuchian (Crocodilus niloticus, the Nile crocodile) and ornithodiran (Eudromia elegans, elegant crested tinamou) archosaurs to inform biomechanical models of ten key extinct taxa from both lines. Rigorous forwards simulation using these models will then be used to address hypotheses of relative performance between pseudosuchia and ornithodira.
My previous project analysed the biomechanics underlying sesamoid bone formation. Using bird and lizard patellar sesamoids as an exemplar, we used musculoskeletal modeling/simulation (SIMM), customized animation software (MAYA / MATLAB) and biplanar xray with scientific rotoscoping (XROMM) to study the biomechanics of tendon/sesamoid complexes. We found that, like humans, avian and squamate patellar sesamoids decrease knee extension force but increase extension velocity. Earlier work in includes quantification of variation in limb kinematics and dynamics in 'sprawling' animals, which involved working with Caiman (a personal career highlight). Very, very pretty animals. They bite hard though. My PhD research focused on characterising locomotion in the extant Archosauria (Aves + Crocodilia, and related extinct groups) and the use of data from extant representatives to generate and test hypotheses regarding locomotion in extinct archosaurs, particularly theropod dinosaurs.
Supervisors: Martin S. Fischer, John Hutchinson, and Monica Daley
My previous project analysed the biomechanics underlying sesamoid bone formation. Using bird and lizard patellar sesamoids as an exemplar, we used musculoskeletal modeling/simulation (SIMM), customized animation software (MAYA / MATLAB) and biplanar xray with scientific rotoscoping (XROMM) to study the biomechanics of tendon/sesamoid complexes. We found that, like humans, avian and squamate patellar sesamoids decrease knee extension force but increase extension velocity. Earlier work in includes quantification of variation in limb kinematics and dynamics in 'sprawling' animals, which involved working with Caiman (a personal career highlight). Very, very pretty animals. They bite hard though. My PhD research focused on characterising locomotion in the extant Archosauria (Aves + Crocodilia, and related extinct groups) and the use of data from extant representatives to generate and test hypotheses regarding locomotion in extinct archosaurs, particularly theropod dinosaurs.
Supervisors: Martin S. Fischer, John Hutchinson, and Monica Daley
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Papers by Vivian Allen
One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals.
Methodology/Principal Findings
Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary.
Conclusions/Significance
Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced “avian” lung structure and high locomotor costs.
One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals.
Methodology/Principal Findings
Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary.
Conclusions/Significance
Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced “avian” lung structure and high locomotor costs.