In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx.
[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.
[3] In frogs, the few caudal vertebrae are fused together to form part of the urostyle.