because snakes can mate better
tailbone of a human whale pelvis bone
It is referred to as the pelvic girdle. Boas and pythons are the only snakes that still have them, and that's where their spurs are connected to.
Most of the "higher evolved" animals I can think of have a vestigial structure or two. The most common example given is of the vestigial leg structures that can be found in the back of whales. Ostriches can't fly so i think their wings are considered vestigial. Humans have a vestigial tail bone.
Both humans and snakes have an exoskeleton made of bone and some cartilage. Both poses a skull, a jaw, vertebrae, and ribs. Some snakes also have a vestigial pelvis.
Hip bone, leg bone, head bone.
The penis is a soft tissue structure and is not part of the pelvic bone.
pelvic bone
The shape of the pelvic bones and the frontal bones differ.
That is the tail bone.
Snakes have pelvic bones for the same reason we have tail bones. Evolution. At some point in the history of life, snakes had legs and humans had tails.
I think the pelvic is near your hip bone. :D