Some researchers have identified petrified skin which belonged to one of the oldest species Paleozoic reptiles: according to estimates, the find dates back to min 21 million years ago compared to previously described fragments of fossil skin and is therefore the oldest example of preserved epidermis ever found. The fossil was collected along with many other finds in Richards Spur limestone cave system in Oklahoma and first described in the journal Current Biology.
“From time to time we have a unique opportunity to look back in time. These kinds of discoveries can greatly enrich our understanding and perception of these pioneer animals,” said the study’s first author Ethan Mooneystudied paleontology at the University of Toronto, but who participated in the project as a student under the supervision of a paleontologist Robert Reisz. Skin and other soft tissues are rarely fossilized, but scientists believe that in this case the skin was preserved due to unique features of the cave systema subterranean environment, probably without oxygen, in which very fine clayey sediments were also present.
“Animals would have fallen into this cave system during the early Permian and been buried there very fine clayey sediments which would delay the decomposition process.” Mooney continued. “But it’s interesting that this cave system was also an active place oil leakage and interactions between petroleum hydrocarbons and tar probably allowed this skin to be preserved.” The skin fossil found is smaller than a fingernail: microscopic examination, performed by the co-author Maho tea from the University of Toronto Mississauga revealed the presence of epidermal tissues, a characteristic feature of the skin of amniotes, a group of land vertebrates that includes reptiles, birds and mammals that evolved from amphibians during the Carboniferous, about 300 million years ago.
Skin has some characteristics shared with extinct and extant reptilesincluding a rough surface similar to that of crocodiles and thinner areas between the epidermal scales that resemble the so-called hinges snakes and lizards. However, since the find is not associated with a skeleton or other remains, it is impossible to determine to which species of animal or region of the body it belonged, but the fact that this ancient skin resembles the skin of today’s animals shows how important these structures are to survival in the terrestrial environment. In fact, reptilian scales represented an important evolutionary adaptation in the transition to life on land, allowing these animals to retain internal fluids more efficiently.
“Skin was a critical feature for vertebrate survival on land,” Mooney explained. “It is a very important barrier that separates the internal processes of the body from the harsh external environment. Finding such an ancient skin fossil is a unique opportunity to peer into the past and see what the skin of some of these early reptiles might have looked like.” The researchers say the skin could represent the structure of the skin of the ancestors of the first terrestrial vertebrates which allowed the evolution of bird feathers and mammalian hair follicles.