This Skin Is Nearly 300M Years Old

It looks a lot like crocodile skin, with a pebblelike texture someone might desire for a purse. But for the small sample size, you'd never guess it's 289 million years old, dating to the late Paleozoic Era, when many species were just beginning to venture from water to land. It's extremely rare to find fossilized dinosaur skin. It's even rarer to find fossilized skin from reptiles predating dinosaurs, so you might say the sample, which emerged from a cave in Oklahoma, is the very rarest of the rare. Indeed, it's the oldest fossilized skin on record, at least 21 million years older than mummified animal skin found at sites in Russia and South Africa, Science reports, and "more than 130 million years older than the vast majority of comparable samples," per Popular Science, which explains the dating process.

The skin sample, no larger than a human fingernail, may have come from Captorhinus aguti, a small, lizardlike reptile which accounts for the greatest share of fossils inside the limestone caves of Richards Spur, per CNN. But the researchers, who received the fossil from a private collector in 2018, can't be positive. They are positive about one thing at least: some of the earliest reptiles had scaly skin, much like the snakes and worm lizards of today. The fossil, about a quarter of a millimeter thick, "includes both an inner dermis layer—rarely preserved—and a tough epidermis, characterized by individual bands of folded scales separated by a flexible 'hinge' region with no scales that would have allowed for growth and movement," Science explains.

Skin typically "decomposes very easily," University of Toronto at Mississauga biology professor Robert Reisz, a co-author of a study on the findings published Thursday in Current Biology, tells CNN. But hydrocarbons present in oil seeps reaching into the cave system would've prevented oxygen and microbes from reaching soft tissues, slowing degradation, per the Washington Post. Still, pressing too hard on the delicate skin would've turned it to dust, lead study author and U of T master's student Ethan Mooney tells PopSci. Researchers had to put the sample in epoxy and cut it with a fine-tipped diamond saw to view it under a microscope. "The sheer chance for a soft tissue structure to be preserved, to survive until now ... to have been found… and then described by us is quite an incredible story," says Mooney. (More discoveries stories.)