DNA remnants found in fossil of 6 million year old turtle

Remnants of DNA have been discovered in fossilised remains dating to 6 million years ago of a sea turtle closely related to today’s Kemp’s ridley and olive ridley turtles

Remnants of DNA have been discovered in fossilised remains dating to 6 million years ago of a sea turtle closely related to today's Kemp's ridley and olive ridley turtles, marking one of the rare times genetic material has been identified in such ancient fossils of a vertebrate, researchers said on Thursday.

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

In some of the osteocytes, the cell nuclei were preserved and reacted to a chemical solution that allowed the researchers to recognise the presence of remnants of DNA, the molecule that carries genetic information for an organism's development and functioning, said palaeontologist Edwin Cadena, lead author of the study published in the Journal of Vertebrate Paleontology.

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"I want to point out that we did not extract DNA, we only were able to recognise the presence of DNA traces in the nuclei," added Cadena, of Universidad del Rosario in Bogota and the Smithsonian Tropical Research Institute.

DNA is quite perishable, though in the right conditions it has been preserved in some ancient remains. Researchers last year reported the discovery of DNA from animals, plants and microbes dating to about 2 million years ago from sediment at Greenland's remote northernmost point.

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