Just about any elementary school student can rattle off the characteristics that make mammals special: They’re warm-blooded, have fur or hair, and nearly all are born alive.
A new study suggests mammals are unique in one more way — the makeup of their spines.
Led by Associate Professor of Organismic and Evolutionary Biology and curator of vertebrate paleontology Stephanie Pierce and postdoctoral researcher Katrina Jones, the study challenges the notion that specialization in mammal backbones dates back to the earliest land animals. The research is described in a September paper in Science.
“The spine is basically like a series of beads on a string, with each bead representing a single bone — a vertebra,” said Pierce. “In most four-legged animals, like lizards, the vertebrae all look and function the same. But mammal backbones are different. The different sections or regions of the spine — like the neck, thorax, and lower back — take on very different shapes. They function separately and so can adapt to different ways of life, like running, flying, digging, and climbing.”
To understand how those specialized regions came to be, Pierce and Jones decided to look back at the fossil record.
“There are no animals alive today that can record the transition from a ‘reptile-like’ ancestor to a mammal” said Jones, the lead author of the study. “To do that we must dive into the fossil record and look at the extinct forerunners of mammals, the nonmammalian synapsids.”
But studying fossils isn’t easy.