By BBC
Added: Sun, 12 Jul 2009 23:00:00 UTC

Thanks to Kevin for the link.

http://news.bbc.co.uk/2/hi/science/nature/8142664.stm

Scientists have revealed a spectacular insight into turtle evolution - how the unique animals get their shells.

A Japanese team studied the development of turtle embryos to find out why their ribs grow outward and fuse together to form a tough, external carapace.

Reporting in the journal Science, the researchers compared turtle embryos with those of chicks and mice.

They found that, as turtles developed, part of their body wall folded in on itself forcing the ribs outward.

The team of researchers from the Riken Center for Developmental Biology in Kobe, Japan, described the turtle shell as an "evolutionary novelty".

It represents such a leap from the soft-bodied ancestors that turtles share with mammals and birds, that scientists have long puzzled over how exactly it came about.

"Other groups have looked into why the shoulder blade in turtles is encased inside the rib cage," said Olivier Rieppel from Field Museum in Chicago, an expert in reptile evolution who was not involved in this study.

"That makes them unique."

Continue reading:
http://news.bbc.co.uk/2/hi/science/nature/8142664.stm

TAGGED: EVOLUTION