Oldest Known Fossilized Skin is 21 Million Years Older than Previous Examples
Published:29 Feb.2024 Source:Cell Press
Researchers have identified a 3D fragment of fossilized skin that is at least 21 million years than previously described skin fossils. The skin, which belonged to an early species of Paleozoic reptile collected from the Richards Spur limestone cave system in Oklahoma, has a pebbled surface and most closely resembles crocodile skin. It's the oldest example of preserved epidermis, the outermost layer of skin in terrestrial reptiles, birds, and mammals, which was an important evolutionary adaptation in the transition to life on land.
Skin and other soft tissues are rarely fossilized, but the researchers think that skin preservation was possible in this case because of the cave system's unique features, which included fine clay sediments that slowed decomposition, oil seepage, and a cave environment that was likely an oxygenless environment. But the kicker is that this cave system was also an active oil seepage site during the Permian, and interactions between hydrocarbons in petroleum and tar are likely what allowed this skin to be preserved.
The skin shares features with ancient and extant reptiles, including a pebbled surface similar to crocodile skin, and hinged regions between epidermal scales that resemble skin structures in snakes and worm lizards. The fact that this ancient skin resembles the skin of reptiles alive today shows how important these structures are for survival in terrestrial environments. The researchers say that this skin may represent the ancestral skin structure for terrestrial vertebrates in early amniotes that allowed for the eventual evolution of bird feathers and mammalian hair follicles.