Shells provide good protection for turtles, but that may not be why those shells originally formed. Denver paleontologist Tyler Lyson says the shells evolved because the turtles’ ancestors, ancient lizards, started digging holes.
Lyson, of the Denver Museum of Nature and Science, studied fossils from South Africa and determined that the digging movements caused these ancient creatures’ rib cages to broaden, thicken and eventually move to fuse with the spine, forming a shell. He says that the shells helped turtles survived the extinction of dinosaurs.
Lyson is currently leading a project called the Valley of the Last Dinosaurs that is delving deeper into the story of the extinction of the dinosaurs and how life on Earth recovered following the extinction.
See a video animation of the fossil record, photos and listen to Lyson speak with Colorado Matters host Ryan Warner at cpr.org