Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs

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.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.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

Cyclical growth in the long limb bones of a sauropod dinosaur

Structures indicative of cyclical growth are described for the first time in a long limb bone of a half-grown sauropod dinosaur. This provides a mean by which age and growth rate are tentatively assessed. The significance of the findings in terms of sauropod physiology is discussed and it is concluded that the data are accordant with an imperfect mass homeothermy and incipient (mass) endothermy as a model of sauropod physiology

The dragonflies of the Dordogne: their value as indicators of mid-term ecological changes

The long term study of the dragonfly community of the Department de la Dordogne (F-24000, South Western France) , as well as the monitoring , over 25 succeeding years, of the changes in the distribution of some local populations , led us to discuss , in this particular case, the value of using adult Dragonflies and Damselflies as « ecological indicators ». It seems indeed possible to correlate local changes in distribution and abundance of adults through time with recent modifications of the local biota by human activities . The reactions of the Odonata to these changes are species specifie, and appear to be mainly connected with their larval ecology . The implications of these findings for a more satisfactory management of the local biota are finally considere

Complementary study on the biology of the semi-desertic amphibia Bufo pentoni: sekelettochronological and ecodemographic data

Observation de 74 B. p. adultes collectés dans le nord du Sénégal. Structure d'âge et recrutement de la population. Maturité sexuelle à 2 ans d'âge environ. Durée de vie: six ans maximum. La structure d'âge hétérogène observée serait une adaptation au milieu très particulier du Sahe

Relationship between bone growth rate and the thickness of calcified cartilage in the long bones of the Galloanserae (Aves)

The histological features of mineralized tissues can be preserved for hundreds of millions of years, and are therefore important potential sources of information for reconstructing the life history traits of extinct species. Bone growth rates and the duration of the growth period have recently been estimated in fossil archosaurs from periosteal ossification (a mechanism responsible for bone diametral growth). Similarly, data on endochondral ossification (the mechanism responsible for bone longitudinal growth) may also yield information on growth duration and rate among extinct vertebrates, as long as potentially informative structures are preserved. However, in order to carry out palaeobiological estimations of growth rate and/or the duration of growth, it is first necessary to quantify in extant species the relationship between these life history traits and the histological features of endochondral ossification that are potentially preserved in the fossil record. Here we analyse the ontogenetic variation of both bone longitudinal growth rate and the thickness of the calcified cartilage in the femora of two Galloanserae (Aves) and find a significant positive relationship between these variables in both species. We discuss possible factors underlying interspecific differences in this relationship, and conclude that it could be applied with caution to draw palaeobiological inferences