Question

what is called as fused bones in vertebral column.

Answer 1

The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate, in which the notochord (a flexible rod of uniform composition) found in all chordates has been replaced by a segmented series of bones—vertebrae separated by intervertebral discs.[1]The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord.

Answer 2

Fused bones in the vertebral column are the 5 fused sacral vertebrae and 4 fused coccygeal vertebrae.