Paleontologists discover extra-limbed reptile

A reptile from the dawn of the dinosaur age had an extra digit on each limb, Canadian paleontologists have found.

About 240 million years ago, most tetrapods, four-limbed vertebrates, had five digits on each limb.

Polydactyly, or extra digits, occasionally happens in modern pandas, moles, humans and cats. The extra digits are rare and usually stunted, rather than resembling a full finger or toe.

Researchers at the Canadian Museum of Nature say a marine reptile unearthed in China's Hubei province had six fully formed digits.

The newly described creature is an amniote, a group that includes reptiles, birds and mammals.

Xiao-Chun Wu and colleagues in China say the extra digit unexpectedly re-emerged in the marine reptile about 242 million years ago.

The pattern resembles one seen in the earliest four-limbed animals more than 100 million years before, the team said. The pattern has not been found in its contemporaries from the Early Triassic period.

The creature's extra digits appear in front of the usual set, the researchers wrote in Thursday's issue of the journal Nature.

They speculate its wide, short limbs may have helped it to "swim" underwater.

The fossil is housed at the Shanghai Science and Technology Museum.