DNA remains found in a 6 million-year-old turtle fossil

September 28 (Reuters) – DNA fragments have been discovered in the fossilized remains dating back six million years ago of a sea turtle closely related to today’s Kemp’s Ridley and Olive Ridley turtles, marking one of the rare cases in which genetic material has been identified in such… Antiquity. The fossils of a vertebrate animal, researchers said Thursday.

The researchers said some bone cells, called osteocytes, were exquisitely preserved in the fossil, which was excavated along the Caribbean coast of Panama in 2015. The fossil is partial, with a relatively complete carapace – the turtle’s shell – but not the rest of the skeleton. . They said the turtle was about a foot (30 cm) long when it was alive.

Paleontologist Edwin Cadena, lead author of the study, said that in some bone cells, the cell nucleus was preserved and reacted with a chemical solution that allowed researchers to identify the presence of DNA residue, a molecule that carries genetic information for the development and functioning of the organism. From the study published in the Journal of Vertebrate Paleontology.

“I want to point out that we did not extract DNA, we were only able to identify the presence of traces of DNA in the nucleus,” added Cadena of the Universidad del Rosario in Bogotá and the Smithsonian Tropical Research Institute.

DNA is quite perishable, although some ancient remains have been preserved in the right conditions. Last year, researchers announced the discovery of DNA from animals, plants and microbes dating back about 2 million years ago from sediments in far northern Greenland.

The only vertebrate fossils older than the newly described turtle found with similar DNA remains were from two dinosaurs: Tyrannosaurus, which lived about 66 million years ago, and Brachylophosaurus, which lived about 78 million years ago, Cadena said. DNA remains have also been reported in insects dating back tens of millions of years, Cadena said.

Cadena said the turtle belongs to the same genus – Lepidochelys – as two of the world’s seven living species of sea turtles – the Kemp’s ridley, the world’s smallest sea turtle, and the olive ridley. The Kemp’s Ridley, which has a triangular head and a slightly hooked bill, is found primarily in the Gulf of Mexico. The olive ridley, which closely resembles the Kemp’s ridley, has a larger distribution, and is found primarily in the tropical regions of the Pacific, Indian, and Atlantic Oceans.

The fossil represents the oldest known member of Lepidochelys and helps shed light on the poorly understood evolutionary history of the genus, researchers said. Cadena said they did not identify it by species because the remains were too incomplete.

“Every fossil, and every fossil site, has specific conditions for preservation, which in some cases can favor the preservation of original biomolecular remains such as proteins and DNA,” Cadena said.

“Maybe in the future, with more studies of this kind, we can at some point sequence very small pieces of DNA and infer things about their relatives or involve this information in a broader molecular evolutionary study,” Cadena added.

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