Compiled by | Xin Yu
The skin provides animals with a sensitive, flexible, and waterproof barrier. However, after the death of an animal, the skin cannot be preserved for a long time, making it difficult for scientists to study the evolution of this organ in ancient creatures.Now, researchers from the University of Toronto in Canada have discovered a fragment of reptilian skin fossil that is more than 20 million years older than any previously described animal skin fossils. This fragment can be traced back to the late Paleozoic era when many species began to emerge from the water and live on land. The related research results were published on January 11th in "Current Biology".Phil Bell, a paleontologist from the University of New England who was not involved in the study, said that how animal skin adapted to this dramatic transition has always been a blank spot in paleontology research. This new discovery suggests that the complex structure of reptilian scales has "hardly changed" since its initial evolution.Skin fossils are rare and precious. Ethan Mooney, the main author of the study and a master's student in paleontology at the University of Toronto, pointed out that in caves, small sediments and low oxygen conditions help slow down the decomposition of fossils. The Richards Spur limestone cave in Oklahoma, USA, is buried with the most diverse and well-preserved Paleozoic fossils in the world. The cave is filled with oil and tar from nearby Woodford Shale, which seep into the fossils, further protecting them from decay.The Richards Spur is buried with many fossils of large sail-backed reptiles, a lizard-like reptile about the size of a Komodo dragon, with obvious overlapping teeth. Most of the specimens are just skeletons. However, the newly-described fossil still preserves part of the outermost layer of the skin, the scale-shaped epidermis. Mooney pointed out that the development of a thick and waterproof epidermis is crucial for its survival on land.While studying these fossils, researchers also discovered a series of subtle spots. Initially, Tea Maho, a biologist at the University of Toronto, thought these spots were small fragments of bone that were smaller than fingernails and as fine as human hair. But microscopic analysis revealed that they were actually very well-preserved reptile skin. This fossil includes a rarely preserved dermis and a tough epidermis, characterized by a single folded scale band separated by a flexible "hinge" region.This fossil fragment has a history of nearly 300 million years and is the oldest documented skin fossil. Robert Reisz, the corresponding author of the study and a paleontologist at the University of Toronto, said that although some mummified skin fragments have been found in Russian and South African sites, they have not been carefully analyzed and are at least 21 million years younger than the fossils found at Richards Spur.Based on the structure of this fossil and its similarity to other fossils, researchers believe that it belongs to some kind of reptile because its wrinkled pebble-like texture is very similar to crocodile skin, and the "hinge" region is similar to the skin structure of modern snakes and worm lizards."It is not surprising that some of the earliest reptiles had typical scale-like skin, but it is exciting to confirm this for the first time in the fossil record," said Bell.Related paper information:
https://doi.org/10.1016/j.cub.2023.12.008
China Science News (2nd edition, international) - January 15, 2024Editor | Zhao LuLayout | Guo GangPlease scan the QR code below for 3 seconds
