A new study by a team of scientists led by Robert Reisch and Aaron Leblan from the University of Toronto in Mississauga, Canada shows that a group of small reptiles that lived 289 million years ago could separate tails to escape predators. This is the oldest known science example of such behavior.
Reptiles called Captorhinus weighed less than 2 kg and were smaller in size than predators of that period. A lot of such animals roamed the planet at the beginning of the Permian period. They were distant relatives of all modern reptiles.
Small omnivores and herbivores Captorhinus had to procure food, and also try not to be eaten by large carnivorous amphibians and ancient relatives of mammals. “One of the ways that capotorhynids could do this was to have detachable vertebrae of the tail,” says study author Leblanc. Like many modern species of lizards, for example, skinks that can separate their tails in order to escape or distract a predator, many of the predator’s caudal vertebrae had cracks in the middle.
Probably, the cracks appeared as perforated lines between two sheets of paper towels, allowing the vertebrae to break into two halves along the section.
The authors note that this property was the key to the success of Captorhinus, since they were the most common reptiles of that time. By the end of the Permian period, 251 million years ago, the Capporquinidae spread throughout the ancient Pangea supercontinent.
Separated tails disappeared from the geological record, when Captorhinus died out, and appeared in lizards only 70 million years ago.
Scientists have studied more than 70 caudate vertebrates and partial skeletons of tails with vertebral fractures. The authors found that the cracks formed naturally as the vertebrae developed. The research team found that young Capporquinides had well-formed cracks, whereas in some adult individuals, vertebrae tended to show up. This makes sense, since predators often hunt for young individuals, and they need the opportunity to protect themselves.