Investigating the enigmatic Aeolosaurini clade: the caudal biomechanics of Aeolosaurus maximus (Aeolosaurini/Sauropoda) using the neutral pose method and the first case of protonic tail condition in Sauropoda

ABSTRACT

The neck posture and function in sauropods have been widely studied during the last decades. The cartilaginous neutral pose (CNP) method is commonly used in biomechanical reconstructions by positioning the vertebrae with the joint surfaces aligned to obtain the ‘neutral pose’. However, few studies have analysed the posture and function of the tail of sauropods. The published data suggest that most sauropods maintained their tails in a horizontal position. We test the neutral pose hypothesis in the anterior caudal vertebrae (C4 to C9) of Aeolosaurus maximus (Titanosauria, Sauropoda), a member of Aeolosaurini endemic of South America, by using the following methodologies: CNP, and range of movement (RoM). The results show that the tail of A. maximus possibly presented in a sigmoidal format which differs from the horizontal position commonly inferred to other sauropods. A. maximus is the first sauropod with caudal vertebrae presenting in situ protonic posture, which corroborates the neutral pose hypothesis and demonstrates that this characteristic is possibly a feature of the Aeolosaurini clade.

KEYWORDS:

• Biomechanics
• Aeolosaurini
• Aeolosaurus maximus
• sauropods

Acknowledgments

The authors would like to thank the Macrofossil Laboratory of the Universidade Federal do Rio de Janeiro for providing the necessary infrastructure to the development of this research, to the Paleontology Museum Professor Antonio Celso de Arruda Campos, from Monte Alto city, for the excellent service and dedication to paleontological research, and to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) that funded this research. R. Candeiro and L. Berqgvist thank the grant “Bolsa de Produtividade em Pesquisa” provided by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). SLB’s collaborative work with CRAC was funded by a grant from the Fundacão de Amparo a Pesquisa de Goiás (FAPEG) and Newton Fund.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.