New fossil shows how soft-shelled turtles have barely changed in 120 million years
Chinese researchers have found the earliest recorded fossil of a soft-shelled turtle, showing how little the species has changed over the last 120 million years.
The Perochelys lamadongensis, found at the early Cretaceous Jiufotang formation in western Liaoning province, was so similar to soft-shelled turtles today that the researchers were not sure where it fit in the evolutionary tree.
Writing in the latest issue of the Journal of Vertebrate Paleontology, the researchers from the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology said the similarity of the ancient fossil to the modern animal was a "rare phenomenon".
"High levels of homoplasy" make it difficult to place the new discovery easily within the fossil record, the researchers said, referring to the independent evolution of similar features in species of different lineages.
The new discovery indicates that the biology of the soft-shelled turtle "has remained virtually unchanged for the last 120 million years", the paper concluded.
Chinese researchers previously claimed they had discovered the world's earliest soft-shelled turtle in Sichuan province in 1950, naming it Sinaspideretes wimani, but the conclusion has since been discredited.
In 2013, Japanese researchers said they had found a 130 million year old soft-shelled turtle, Kappachelys okurai, but the discovery remains in dispute because the claim is only based on two small bone fragments.