The ancient skin sample, no bigger than a human fingernail, dates back about 289 million years to the early days of the Permian period, when Earth’s continents were joined into a single supercontinent surrounded by a global ocean. This landmass supported a diverse group of ancient plants, reptiles, primitive amphibians and various insects.
The generally warm and dry climate during the Permian played a significant role in helping early reptiles make the transition from semiaquatic to fully land-based lifestyles. The emergence of important reptile groups eventually led to the evolution and further separation of mammals and reptiles — although the Permian ended in a dramatic mass extinction that wiped out about 90 percent of the planet’s species.
Studying fossils from the Permian period provides scientists with valuable insights into the ancestral animals that ultimately evolved into the life forms we know today.
Although the scientists can’t be sure what species the fossilized skin comes from, its microscopic structures show that it was part of a group called the amniotes, which includes mammals, reptiles and birds. The patterning is similar to crocodile skin, indicating that this type of skin may have been found in early reptiles and their relatives.
“Preservation of soft tissue is very rare, and this fossil find really shows us the first major innovation in the structure of the largest organ of the body, which is the skin,” said study co-author Robert Reisz, a paleontologist from the University of Toronto at Mississauga.
An amateur collector found the skin fossil while working at the Richards Spur limestone cave system, a known fossil site north of Lawton, Okla. The collector donated it to the researchers in 2018. The tissue was sent to Reisz and his team and was examined by Ethan Mooney, a paleontology graduate student at the University of Toronto.
Skin and soft tissue fossilization is extremely rare, but the authors believe that the conditions of the clay-rich cave, including oil seepage, provided an optimal environment for preservation. That’s because hydrocarbons in oil seeps can inhibit decomposition and degradation, effectively sealing off soft tissues from oxygen and microbial activity and contributing to its long-term preservation.
Because the fossilized skin was so delicate, the researchers embedded the sample in epoxy and cut it with a fine-tipped diamond saw so they could examine it under the microscope. The researchers were able to date the fossil based on previous research published in 2013.
From their examination, they were also able to discern that the fossil had similar anatomical features to the extinct species Captorhinus aguti, which lived during the Permian and belonged to an early group of reptiles. The research suggests that the species had flexible, tough bands of skin or epidermal tissue that may have served protective, movement or structural functions.
Paul E. Olsen, a paleontologist and professor of earth and environmental sciences at Columbia University who was not involved in the research, said one of the biggest takeaways from this finding is that it addresses some of the mysteries surrounding the transition of the common ancestor to mammals and reptiles. These two branches of life split sometime during the Paleozoic Era, which includes the Permian.
“It’s a wonderful discovery because it prompts more discoveries in the same place … and we may eventually learn what type of skin reptiles had,” Olsen said.
Discoveries in the Permian period provide crucial information about the evolutionary history of life on Earth, the dynamics of ancient ecosystems and the environmental changes during this pivotal time in Earth’s history.
“A lot of people don’t think about what comes before the dinosaurs,” Mooney said, “and in our study, we are able to look back into what some of these ancestors to many of the major groups of [animals] that we know and love today may have looked like.”
Credit: Source link
