Archosauromorpha: from early diapsids to archosaurs
Résumé
This chapter reviews and summarizes the histological data currently available on the bone histology of early (mainly Permo-Triassic) archosauromorphs, including archosauriforms and pseudosuchian (crurotarsal) archosaurs. Recent research worldwide has considerably expanded our knowledge of this subject. Emphasis is placed here on the histology of long bones rather than of flat dermal bones and osteoderms. Fast-growing fibrolamellar bone patterns, often associated with growth cycles, are observed in most taxa (notably among rhynchosaurs and allokotosaurs), at least during early and middle stages of ontogeny. Some taxa at various levels in the evolutionary tree seem to revert to a more plesiomorphic growth condition, expressed by the reliance on a slow-growing lamellar-zonal bone pattern throughout ontogeny. These data are discussed from various points of view, notably growth dynamics and thermometabolism.