Stéphane Hua

Bone histology as a clue in the interpretation of functional adaptations in the Thalattosuchia (Reptilia, Crocodylia)

ABSTRACT The histological study of various bones in the families Teleosauridae and Metriorhynchidae reveals common, but also contrasting structural features of the skeleton. Both display a zonal pattern of bone tissue, suggesting a cyclic growth and an ecto-poikilothermic physiology, quite similar to those of recent crocodiles. However, the Teleosauridae exhibit no peculiar skeletal specializations related to marine life, which suggests that they had an amphibious, rather than a truly marine habitat. Conversely, the skeleton of the Metriorhynchidae displays a certain degree of structural lightening, especially obvious in their skull, but also present in their femora and ribs. This structural specialization of the skeleton, together with the supposed physiological regime of the Metriorhynchidae, had definite bearings on their body trim in water, locomotor capabilities, and activity cycles. These various topics are discussed with reference to the ecological and eco-physiological adaptations of the Thalattos...

A PRIMITIVE MARINE GAVIALOID FROM THE PALEOCENE OF MOROCCO

Abstract The discovery of a new genus and species of gavialoid at the Danian–Thanetian boundary, in the Oulad Abdoun Basin of Morocco, is consistent with an African origin of Gavialoidea. Argochampsa krebsi, n.g. n.sp., exhibits a particular shape of the anterior end of its premaxillae, transversely broad and strongly bent downwards, a shape found in distantly related taxa, such as pholidosaurids and Terminonaris. A phylogenetic analysis, suggests that A. krebsi is a primitive gavialoid, placed with Eogavialis africanum between ‘thoracosaurs’ (primitive Gavialoidea) and more derived taxa. This analysis supports the previous morphological analysis, which suggests a close relationship of Tomistominae with Crocodylinae, in contrast with the molecular analysis which give a closer relationships between Tomistoma and Gavialis. The marine nature of the layer where Argochampsa comes from is consistent with a marine origin for Argochampsa. This demonstrates the existence of marine adaptation in fossil species of primitive gavialoids, which may explain the dispersal of the fossil gavialoids to South America and Asia during and after the Oligocene.