New York, Jan 6 (IANS): Researchers have found that snakes may not have evolved the way it was thought previously as they found that their vertebral bones are similar to those found in the backbone of four-legged lizards.

"Our findings turn the sequence of evolutionary events on its head," said P. David Polly from Indiana University in the US.

The study provides a new perspective on Hox genes, which govern the boundaries of the neck, trunk, lumbar, sacral and tail regions of limbed animals.

The functions of Hox genes were previously thought to have been disrupted in snakes, resulting in seemingly simplified body forms.

Snakes differ from mammals, birds and most other reptiles because they lack forelimbs, shoulder girdles and breast bones.

It was thought that when they lost their limbs, they also lost the regional distinctions that separated their backbones into neck, trunk, lumbar and other regions.

Yet when the researchers examined the shapes of individual vertebral bones in snakes, lizards, alligators and mice, they found snakes had regional differentiation like that of lizards.

When combined with information from fossils, these findings indicate that the direction of snake evolution is the opposite of what had been concluded from developmental genetics alone, the researchers said.

The findings appeared in the journal Nature.