GRANTS PASS, Ore. -- Amateur cave explorers have found a new family of spiders in southern Oregon that scientists have dubbed Trogloraptor, or cave robber, for its fearsome front claws.

The spelunkers sent specimens to the California Academy of Sciences in San Francisco. Entomologists there say the spider -- the size of a half dollar -- evolved so distinctly that it requires its own taxonomic family -- the first new spider family from North America since 1870.

The species name, marchingtoni, honours Douglas County sheriff's Deputy Dave Marchington, who led scientists to the cave outside Grants Pass.

Academy entomologist Charles Griswold says the spider spins a crude web, but scientists don't know yet what or how it eats.

The discovery is described in the online edition of the journal ZooKeys.