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.

KEYWORDS:

• Cretaceous
• pterosaur
• Caiuajara
• osteohistology
• ontogenetic stages

Acknowledgments

The authors thank Vilson Greinert (CENPALEO, Mafra) for preparing specimens before taking the samples for the osteohistological analyses. João Henrique Zahdi Ricetti (CENPALEO), for helping with the bone samples and photographs; Maria Erivânia Izídio Souza, (Universidade Federal de Pernambuco), for helping to prepare the osteohistological slices. Mário Fritch (Universidade do Contestado, Mafra), Marina Bento Soares (LAPUG – Museu Nacional/UFRJ) for access to their laboratory for the preparation of slides, Enelise Katia Piovesan (LITPEG-Universidade Federal de Pernambuco) for slides imaging. We would also thank Dr. Mariana Valéria de Araújo Sena and the two anonymous reviewers for valuable discussions that improved this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior #88887.478992/2020-00 - Brasil (CAPES 88887.478992/2020-00) to EVA; Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP [#PV1-00187-0052.01.00/21]) to RAMB, and BH (FUNCAP [#PV1-0187-00054.01.00/21]); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro #E- 26/202.905/2018 to BH (FAPERJ [#E-26/002.360/2020]) to AWAK (FAPERJ [#E- 26/201.095/2022]); and to JMS (FAPERJ [#E-26/010.002178/2019]); and Conselho Nacional de Desenvolvimento Científico e Tecnológico to JMS (CNPq #314222/2020-0) and to AWAK (CNPq #313461/2018-0; CNPq #406779/2021-0; and CNPq #406902/2022-4 - INCT PALEOVERT]. We take the opportunity to thank the Government of the Federal Republic of Germany for funding equipment that helped the development of the present study.