Another mystery solved

More gaps in evolution are plugged as human knowledge grows of understanding where we and and life on earth came from. It is amazing how we can now piece together the evolution of many species going back 100s of millions of years.

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How the turtle shell evolved has puzzled scientists for years, but new research sheds light on how their hard shells were formed.

Scientists say the ancient fossil skeleton of an extinct South African reptile has helped bridge a 30 to 55-million-year gap.

This ancestor of the modern turtle, Eunotosaurus, is thought to be around 260 million years old.

It had significant differences to a recently found fossil relative.

Eunotosaurus was discovered over a century ago but new research in the journal Current Biology has only now analysed its differences to other turtle fossils.

An extinct reptile fossil has helped scientists discover how turtles hard shells are formed
A turtle's shell is unique in that it is made up of around 50 bones, with ribs, shoulder bones and vertebrae fused together to form a hard external shell.

How it forms today can be observed in a developing turtle embryo. Ribs broaden first followed by the broadening of vertebrae. The final state is the development of an outer layer of skin on the perimeter of the shell.

"The turtle shell is a complex structure whose initial transformations started over 260 million years ago in the Permian period," said lead author of the study, Dr Tyler Lyson from the Smithsonian Institution and Yale University.

"The shell evolved over millions of years and was gradually modified into its present-day shape."

A turtle fossil 210 million years old had a fully developed shell similar to those today, but 10 million years earlier, a fossil discovered in China named Odontochelys semitestac, had an incomplete top shell, called a carapace.