Do animals have a sacrum bone?

Question

Do animals have a sacrum bone?

Answer 1

The sacrum is formed by the fusion of several vertebrae together to provide a solid connection for the support of the pelvic girdle, and so (naturally enough) is found only in vertebrates, and only terrestrial vertebrates at that.

Of the terrestrial vertebrates, not even all of them have a sacrum.  It's not present in some amphibians, and has been secondarily lost in groups like snakes and whales.