Comprehensive postcranial osteology of the black yacare, Caiman yacare (Alligatoridae: Caimaninae): detailed descriptions, illustrations, and comparison across Crocodylia

Abstract

Among extant Crocodylia, the skeletal anatomy of Alligator and Crocodylus has been studied extensively, whereas South American genera, such as Caiman, have received comparatively less attention. Previous works on Caiman yacare and Caiman latirostris have focused on the skull, the associated axial musculature, embryonic development, and bone microstructure; however, studies on the postcranial skeleton remain limited to certain regions. The aim of this study was to provide a detailed description of the postcranial osteology of C. yacare to enhance knowledge of its anatomy. Twenty-one specimens at different ontogenetic stages were processed into dry skeletons or cleared and stained preparations and were analysed by direct observation and microscopy. We provide detailed descriptions of each bone, accompanied by scientific illustrations highlighting osteological features and myological correlations. Results confirm that the postcranial skeletal morphology of C. yacare is highly conserved, closely resembling other crocodylians and sharing substantial similarities with its congeners. Findings are consistent with previous studies on the composition of the rib cage, basipodium and phalangeal formula of C. yacare. The following vertebral column regionalization is proposed: 8C-13T-3L-2S-30–40Q, in line with other Caimaninae. This work provides a more comprehensive understanding of the skeletal anatomy of the black yacare and establishes a baseline for future morphofunctional, palaeontological, and embryological research.