Caudal vertebrae

Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx.

In many reptiles, some of the caudal vertebrae bear ribs, the caudal ribs, though these are often fused with the vertebrae.^[1]

The caudal vertebrae often articulate with haemal arches ventrally.^[1]

The number of caudal vertebrae in animals can vary greatly. Anguid lizards have been reported to have as many as 111 caudal vertebrae,^[1] whereas as few as seven are present in the tail of the early therapsid Tapinocaninus.^[2]

In lepidosaurs and captorhinids, the caudal vertebrae possess fracture planes at mid-length that allow caudal autotomy.^[3]

In frogs, the few caudal vertebrae are fused together to form part of the urostyle.^[4]

References

1. Romer, Alfred Sherwood (1956). Osteology of the Reptiles.
2. Rubidge, Bruce S.; Govender, Romala; Romano, Marco (2019-10-18). "The postcranial skeleton of the basal tapinocephalid dinocephalian Tapinocaninus pamelae (Synapsida: Therapsida) from the South African Karoo Supergroup". Journal of Systematic Palaeontology. 17 (20): 1767–1789. doi:10.1080/14772019.2018.1559244. eISSN 1478-0941. ISSN 1477-2019.
3. LeBlanc, A. R. H.; MacDougall, M. J.; Haridy, Y.; Scott, D.; Reisz, R. R. (2018). "Caudal autotomy as anti-predatory behaviour in Palaeozoic reptiles". Scientific Reports. 8 (1): 3328. doi:10.1038/s41598-018-21526-3. ISSN 2045-2322. PMC 5838224.
4. Senevirathne, Gayani; Baumgart, Stephanie; Shubin, Nathaniel; Hanken, James; Shubin, Neil H. (2020-02-11). "Ontogeny of the anuran urostyle and the developmental context of evolutionary novelty". Proceedings of the National Academy of Sciences. 117 (6): 3034–3044. doi:10.1073/pnas.1917506117. eISSN 1091-6490. ISSN 0027-8424. PMC 7022158.