Analysis of the fossil suggests that the only two egg-laying mammals, platypuses and land-based echidnas, both descended from ...

By the time you’re an adult, you usually have 24 movable vertebrae (instead of 33) and the rest of the bones are fused together. While most people have a straight spine, some people have additional ...

By analyzing the arrangement of vertebrae in the spines of nearly 400 species of tetrapods—a group of animals with four limbs ...