It is possible for someone to have extra bones there ... seeing as I have six lumbar vertebrae instead of five, and an extra pair of floating ribs, why not !!
The sphenoid, ethmoid, sacrum, coccyx, and mandible are all irregular bones.
The hip bones.
the vertebrate's at the bottom is the coccyx
coccyx
the vertebrate's at the bottom is the coccyx
sacrum.
coccyx
pelvis
Sacrum, and Coccyx
The coccyx are 3 small bones fused together at the bottom of your spine, often this means that a fall (trying to land on your bottom) may result in damage/fractures etc to the bones.
bottom two bones of spine
Tracing down the spine the pelvis leads to the coccyx, aka the tailbone, though the femurs of your legs also extend past the bottom of your pelvis. The pelvis itself is made of the sacrum (back) and os coxa (sides) (and some people include the coccyx.)