Skin In The Evolutionary Game : Ancient clue to animals' emergence from the waters. 

Dry, scaly skin is not something humans prize. But in the broad scheme of things, a tough, watertight hide is part of what enabled the ancestors of modern reptiles, birds and mammals to move inland while their thin-skinned amphibian cousins remained close to water.

IN A STUDY published in the journal Current Biology, scientists announced the discovery of the oldest identified piece of fossilized skin.

The pebbly scrap on, no longer than a human fingernail, most likely belonged to an ancient reptile and provides more insight into the evolution of skin.

The fragment is one of countless traces of prehistoric life preserved in the Richards Spur limestone cave system near an oil seep in southwestern Oklahoma.

When animals fell into the caves 289 million years ago, conditions were ideal for preservation : fine clay sediments rapidly buried the bodies, low levels of oxygen in the groundwater slowed the decay process, and hydrocarbons from the oil made the tissues less hospitable to bacteria. The tar seeped into the fossils staining them.

In 2018, Bill May, a retired forensic analyst, shared some tiny flakes from the Richards Spur that he couldn't identify with Robert Reisz, a paleontologist at the University of Toronto Mississauga.

'' We got very excited by what we saw under the microscope,'' Dr. Reisz, an author of the paper.

Tough, impermeable skin was a key evolutionary adaptation for backboned animals as they took over the land, ''because in order to survive in terrestrial environments, you want to not to dry out,'' said Ethan Mooney, a graduate student who worked with Dr. Reisz on the paper.

The fossilized tissue bore a striking resemblance to the scaly skin of a modern crocodile. [ Kate Golembiewski ].


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