The ninth vertebra is also called the sacral vertebra. It is bigger in size and hard. Transverse process of this vertebra is hard, flat and wide. This feature of the ninth vertebra enables it to be differentiated from other vertebrae very easily. The posterior end of this vertebra has been transformed into two convex parts. The Urostyle is attached with these two convex parts. The transverse process attaching with the Ilium of the pelvic girdle bears their weight.
Fig: Ninth vertebra
The up looking spoon like thick fold that comes out from the front of every neural arch is called pre-zygapophysis. It gives the body firmness by attaching itself with the two post-zygapophysis of the vertebra in front.
The two down looking spoon like folds that come out from the back of every neural arch are called posti-zygapophyss. They remain attached with the pre-zygapophyses of the posterior vertebra. As a result the attachment of the vertebrae becomes firm.