Long necks and jaws enable assassin spiders to kill their prey without having to get too close.
The discovery of the nine new assassin spider species is just a small part of a gigantic biological survey of Madagascar now underway by the California Academy of Sciences, supported in part by the National Science Foundation.
"Literally millions of specimens have been collected," said Griswold of the survey. "There will be many more new species of spiders."
Perhaps a hundred unknown species of spiders are already collected and just waiting for biologists to properly study them, he said.
At just 1/16 to 1/4 of in inch (2 to 6 millimeters) in size, the nine new eight-legged assassins stood out early in the survey because they are so unusual.
"This is a rare family of spider," said arachnid expert Norman Platnick of the American Museum of Natural History.
Platnick oversees the world's largest collection of spider specimens. Worldwide there are now about 39,000 known species of spiders. Estimates of how many remain undiscovered range from 40,000 to 200,000, said Platnick.
Assassin spiders have surprised biologists before, said Platnick. In 1854, the first assassin spiders were discovered as fossils in amber from northern Europe. It wasn't until 27 years later, in 1881, that living assassin spiders were discovered in South Africa, Madagascar and Australia.
The genetics of the new assassin spiders have yielded yet another surprise, said Griswold. The genetic map of the assassin spider family history suggests the long necks and jaws evolved more than once, in what's called convergent evolution, he said.
Convergent evolution is analogous to two people stumbling onto a very similar solution to a problem independently of each other. Apparently, the longer necks are an effective solution that caught on more than once. It's just a little family secret that's impossible to detect if you're just looking the spiders themselves, said Griswold.
