Ontogeny of a sexually selected structure in an extant archosaur Gavialis gangeticus (Pseudosuchia: Crocodylia) with implications for sexual dimorphism in dinosaurs

PeerJ

article

David Hone¹  Jordan C. Mallon²  Patrick Hennessey¹  Lawrence M. Witmer⁵ 

[1] School of Biological and Chemical Sciences, Queen Mary University of London;Beaty Centre for Species Discovery and Palaeobiology Section;Department of Earth Sciences, Carleton University;Department of Biology, Georgia Southern University;Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University

关键词: Crocodilian;    Archosaur;    Dinosaur;    Sexual selection;    Dimorphism;    Ontogeny;   

DOI  :  10.7717/peerj.9134

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Despite strong evidence for sexual selection in various display traits and other exaggerated structures in large extinct reptiles, such as dinosaurs, detecting sexual dimorphism in them remains difficult. Their relatively small sample sizes, long growth periods, and difficulties distinguishing the sexes of fossil specimens mean that there are little compelling data on dimorphism in these animals. The extant gharial (Gavialis gangeticus) is a large and endangered crocodylian that is sexually dimorphic in size, but males also possesses a sexually selected structure, the ghara, which has an osteological correlate in the presence of a fossa associated with the nares. This makes the species a unique model for potentially assessing dimorphism in fossil lineages, such as dinosaurs and pterosaurs, because it is a large, slow-growing, egg-laying archosaur. Here we assess the dimorphism of G. gangeticus across 106 specimens and show that the presence of a narial fossa diagnoses adult male gharials. Males are larger than females, but the level of size dimorphism, and that of other cranial features, is low and difficult to detect without a priori knowledge of the sexes, even with this large dataset. By extension, dimorphism in extinct reptiles is very difficult to detect in the absence of sex specific characters, such as the narial fossa.

【 授权许可】

CC BY