Scientists close to solving age-old turtle shell mystery

October 9th, 2008 - 3:54 pm ICT by ANI  

London, Oct 9 (ANI): Discovery of a new fossil could help scientists in unravelling the biggest mysteries of evolutionhow the turtle got its shell.

The researchers discovered a fossil from a 210-million year-old, land-dwelling reptile, called Chinlechelys tenertestaLatin for thin-shelled turtlefrom New Mexico, and discovered that the earliest turtles didn”t have a shell at all.

It is now believed that in the course of millions of years, rows of protective armour plates gradually fused together over the reptile’’s vertebrae, which ultimately resulted into a complete shell.

“Turtles ultimately originated from something that looked like an armadillo,” New Scientist quoted lead author Walter Joyce, a palaeontologist at the Peabody Museum of Natural History in New Haven, Connecticut, as saying.

It was his colleague Spencer Lucas, of the New Mexico Museum of Natural History and Science in Albuquerque, who had earlier found a neck-bone fragment of the new reptile. But Joyce said that the small size of the skeleton made its provenance debatable.

But, recent erosion has uncovered enough pieces of Chinlechelys tenertesta, that scientists can easily trail the origin of the shell.

Joyce said that triassic turtles are few and far between, quite unlike fossils dating from the later Jurassic era, which he claims are so common people stopped collecting them.

And he believes that this is the reason why they resided on land, where fossilisation is far less likely to happen.

“This one’’s by far the thinnest ever found,” said Joyce.

The animal is about 30 centimetres long, with a shell only a millimetre wide. In fact, its dorsal ribs aren”t fully fused to its shell or carapace much like in later fossils and in modern turtles.

“This is a crucial new discovery. This new guy is an animal that belong to the lineage of turtles, it’’s a proto-turtle in a way,” said Guillermo Rougier, at the University of Louisville in Kentucky, who uncovered the first Triassic turtles in northwest Argentina. These and other early turtles had already gained their carapaces and offered few clues as to its origin.

However, C. tenertesta, indicates towards the body form that must have given rise to the shell. But, Joyce believes that it is still unclear as to why turtles evolved their shell.

They speculate that a full shell might offer added protection and stability, the proof of which lies in the pudding their body plan is the world’’s oldest, changing little over 200 million years.

“For some reason just being a turtle is an idea that came along and just really works,” he said. (ANI)

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