Scientists in the United States say they have found a new family of spiders in the caves of California and Oregon.

It is the first such discovery in North America for more than 140 years.

Spanning more than seven centimetres with its legs extended, the 'Trogloraptor' or 'cave robber' has pointed fearsome claws.

Curator of Arachnology at the California Academy of Sciences, Charles Griswold, told the Today programme presenter Sarah Montague that the discovery marked a "historic moment".