Osteohistological characterization and ontogeny of Caiuajara dobruskii (Pterosauria, Pterodactyloidea, Tapejaridae)

Abstract

Caiuajara dobruskii is a tapejarine pterosaur from a unique pterosaur bonebed in southern Brazil, where hundreds of bones referred to this species have been described. Despite its abundance, specimens were found disarticulated and/or disassociated, hindering ontogenetic interpretations from anatomy. Osteohistology is a proper approach to obtain information on ontogeny as well as other palaeobiological information. Here, we analyse 28 thin sections of distinct appendicular bones, from 18 different specimens belonging to Caiuajara dobruskii. All samples display a fibrolamellar microstructure, which suggests that Caiuajara dobruskii had high metabolic rates throughout its life history. We propose five different histology-based ontogenetic stages: Early juvenile; Late juvenile; Juvenile-to-subadult transition; Subadult; and Adult. When compared with other pterosaur ontogenetic series, Caiuajara had a higher bone deposition ratio than other pterosaurs such as Pterodaustro and Rhamphorhynchus, even when compared with the youngest individuals of those taxa. The fact that this bonebed shows a large accumulation of juvenile specimens in this bonebed, whereby adults are rare and senile are absent, suggest that C. dobruskii might have developed similar to some behaviours present in extant birds, as a breeding point and/or creching.