urostyle

A prolongation backward of the spinal column, especially of the last vertebra, in certain fishes and amphibians: in some Amphibia forming the greater part of the so-called sacrum, or a long bone in the axis of the spinal column behind the sacrum proper, and approximately coextensive with the length of the ilia.

A styliform process forming the posterior extremity of the vertebral column in some fishes and amphibians.

A styliform process forming the posterior extremity of the vertebral column in some fishes and amphibians.