New Spider Family Discovered in Pacific NW Caves

Trogloraptor hangs beneath rudimentary webs beneath cave ceilings. It is about four centimeters wide when its legs are extended—larger than the size of a half-dollar coin.

Trogloraptor or "cave robber" spider.

(SAN FRANCISCO) - A team of scientists and cave conservationists discovered a relatively huge, unique spider in caves and forests of the Pacific Northwest. The novel combination of evolutionary features in this spider, Trogloraptor, compelled them to recognize a new family. A study of the new family and its evolutionary and conservation significance was published in the open access journal ZooKeys on August 17.

The forests of the coastal regions from California to British Columbia are renowned for their unique and ancient animals and plants, such as coast redwoods, tailed frogs, mountain beavers—and now, a large, newly discovered spider. Trogloraptor (or "cave robber") is named for its cave home and spectacular, elongate claws. It is a spider so evolutionarily special that it represents not only a new genus and species, but also a new family (Trogloraptoridae). Even for the species-rich insects and arachnids, to discover a new, previously unknown family is rare.

A team of citizen scientists from the Western Cave Conservancy and arachnologists from the California Academy of Sciences found these spiders living in caves in southwest Oregon. Colleagues from San Diego State University found more in old-growth redwood forests. Charles Griswold, Curator of Arachnology, Joel Ledford, postdoctoral researcher, and Tracy Audisio, graduate student, all at the California Academy of Sciences, collected, analyzed, and described the new family. Audisio's participation was supported by the Harriet Exline Frizzell Memorial Fund and by the Summer Systematics Institute at the Academy, which is funded by the National Science Foundation.

Trogloraptor hangs beneath rudimentary webs beneath cave ceilings. It is about four centimeters wide when its legs are extended—larger than the size of a half-dollar coin. Their extraordinary, raptorial claws suggest that they are fierce, specialized predators, but their prey and attack behavior remain unknown.

The anatomy of Trogloraptor forces arachnologists to revise their understanding of spider evolution. Strong evidence suggests that Trogloraptor is a close relative of goblin spiders (Oonopidae), but Trogloraptor possesses a mosaic of ancient, widespread features and evolutionary novelties.

The true distribution of Trogloraptor remains unknown: that such a relatively large, peculiar animal could elude discovery until 2012 suggests that more may be lurking in the forests and caves of western North America.

These findings were published in: Griswold C, Audisio T, Ledford J. 2012. An extraordinary new family of spiders from caves in the Pacific Northwest (Araneae, Trogloraptoridae, new family). ZooKeys 215: 77-102. http://dx.doi.org/10.3897/zookeys.215.3547

Source: The California Academy of Sciences; an international center for scientific exploration and education and is at the forefront of efforts to understand two of the most important topics of our time: life and its sustainability. The Academy has a staff of over 50 professional educators and Ph.D.-level scientists, supported by more than 100 Research and Field Associates and over 300 Fellows. Its research strengths fall into three broad areas: California biodiversity, global hotspots, and ocean ecosystems. Visit research.calacademy.org.