A centuries-old debate on how reptiles keep evolving skin bones is finally settled |
Our bones did not begin deep inside the body. They started in the skin, not long after the first complex animals took shape.
Ever since, skin bones have remained a recurring motif in evolution. Yet we still know surprisingly little about them. Why do they keep reappearing in groups as varied as turtles, crocodiles, lizards, snakes and even dinosaurs? And was there a single ancestor with skin bones that gave rise to them all?
In a new study published in the Biological Journal of the Linnean Society, we explored this question. We combined fossil evidence with modern computational tools to reconstruct 320 million years of reptile skin bone evolution.
What we found concludes a centuries-long debate: skin bones have indeed independently evolved across multiple lizard lineages. In the process, we also traced a unique evolutionary comeback in one of their most iconic groups – goannas.
The oldest skin bones in the fossil record may date back 475 million years. At that time, some of the earliest vertebrates evolved an elaborate bony exoskeleton.
This may seem counterintuitive, since vertebrates are literally defined by the fact that they have backbones. However, their bony internal skeleton didn’t evolve until