A group of scientists found the oldest fossilized skin in history in caves in the United States. It belonged to an ancient reptile that lived in the early Permian period, in the Paleozoic Era. A long long time ago: between 289 and 286 million years ago.
The skin in question is fragmented into very small pieces that, combined, do not reach the size of a human fingernail. It is a sample of epidermis, the outer layer of skin of amniotes, a group of animals that includes terrestrial reptiles, mammals and birds.
Researchers found it along with other fossils, which were hidden in a limestone cave system in Oklahoma. This fossilized skin has at least 21 million years older than others previously found.
If you saw it through a microscope, you would notice that it looks a bit like crocodile or snake skin. Fossilized skin has small hinges between its scales, describes the study report published this week in Current Biology.
Their discovery demonstrates that the epidermis, which was an important evolutionary adaptation in the transition to life on land, already existed when the first amniotes began to branch into different life forms.
Skin and other soft tissues rarely manage to preserve and survive the passage of time. But a series of circumstances collaborated so that, hundreds of millions of years later, this fossilized piece of skin was found. “Animals would have fallen into this cave system during the Early Permian and would have been buried in very fine clay sediments that slowed the decomposition process,” said Ethan Mooney, a paleontologist at the University of Toronto and lead author of the paper, in a statement. release.
The oldest fossilized skin, a clue to study evolutionary processes
An amateur collector found the oldest fossilized skin while working in the Richards Spur cave system, north of Lawton, Oklahoma. The subject donated it to researchers in 2018.
This cave system was also an active oil seepage site. Therefore, the interactions between petroleum hydrocarbons, tar and the lack of oxygen in these deep places surely favored the preservation of the sample.
Experts were able to date the fossil based on previous research published in 2013. “We were totally shocked by what we saw because it is completely different from anything we would have expected,” Mooney noted. “These types of discoveries can really enrich our understanding and perception of these pioneer animals.”
The team determined that the fossilized skin has characteristics similar to those of the extinct species Captorhinus agoutione of the first amniote vertebrates to walk on earth. The analysis indicates this species had flexible and resistant bands of skin or epidermal tissue, which probably had protective functions. However, because the skin fossil is not associated with a skeleton or other remains, it is not possible to precisely identify which species of animal or body region the specimen belongs to.
Among the other fossils found in these caves were several fragments of skin and scales from anamniotes, animals that reproduced in water. The discovery could also shed light on the later development of feathers and hair in several species. Scientists highlight that the fact that this fossilized skin resembles that of currently living reptiles, demonstrates how important these structures are for survival in terrestrial environments.