Researchers have made a groundbreaking discovery in an Oklahoma limestone cave system, unearthing what is believed to be the oldest known fossilized skin. The skin sample, dating back between 289 million and 286 million years ago during the early Permian Period, belonged to an ancient reptile. This significant finding sheds light on the evolution of amniotes, a group of animals that includes terrestrial reptiles, mammals, and birds.

The study, published today in Current Biology, describes the newly discovered skin as a fossilized epidermis, which is the outer layer of skin in amniotes. Measuring smaller than a fingernail, it is the first skin-cast fossil to be identified from the Paleozoic Era. The research team also uncovered skin compressions, skin fragments from the ancient reptile known as Captorhinus aguti, and scales belonging to anamniotes, water-dwelling animals. While some of the amniote skin could be traced back to specific ancient creatures, not all specimens could be definitively associated.

Despite its often overlooked nature, the epidermis plays a crucial role in protecting the body against external threats. As the outermost layer, it keeps organisms hydrated and shields them from bacteria and extreme temperatures. The ancient reptile's skin, recovered in the cave and generously donated by Bill and Julie May, appears to have served a similar purpose for its host millions of years ago.

The preservation of all skin samples found in the cave can be attributed to fortuitous circumstances. The animals that fell into the cave system during the early Permian Period became submerged in fine clay sediments, which significantly slowed down the decay process. The cave system itself was also an active site of oil seepage during that time, and interactions between petroleum hydrocarbons and tar likely played a crucial role in preserving the ancient skin.

Upon closer examination, the surface of the fossilized skin bears resemblance to that of crocodiles, with hinges between scales similar to those found in modern-day snakes and worm lizards. The research team highlights in their paper that the morphology of the skin, coupled with its remarkable age, indicates that this important organ for terrestrial vertebrate life was present during the initial stages of amniote diversification. In other words, the epidermis existed when early amniotes began branching out into different forms of life.

The study of ancient reptiles continues to provide valuable insights into their evolutionary history. In 2022, researchers made a significant discovery in Wyoming, unearthing a 150-million-year-old fossil that helped clarify the timeline of rhynchocephalians, a unique reptilian group represented by the tuatara. However, the recently analyzed skin discovered in Oklahoma is a sobering reminder of the profound depths of deep time, as it is more than twice as old as the ancient reptile from Wyoming.

The ancient reptile's skin sample holds immense scientific value, serving as an invaluable piece in understanding the evolution of terrestrial animals throughout history. This groundbreaking find emphasizes the importance of preserving and studying fossils to unlock the mysteries of our past and gain a deeper understanding of the intricate tapestry of life on Earth.