A pale, thread-like arthropod found in a marble cavern called Lange Cave in Sequoia National Park, California, has been identified as a new species of millipede, Illacme tobini. The male specimen—about 20 mm (0.8 inches) long—has roughly 414 legs and four modified limbs (the ninth and tenth pairs) used to transfer sperm. Only this single male has been found, so females are unknown.

The specimen was discovered in October 2006 by cave biologist Jean Krejca (now with Zara Environmental in Texas) during a survey of caves in Sequoia and Kings Canyon National Parks; major surveys ran from 2002 to 2004, with follow-up excursions from 2006 to 2009. Krejca sent the millipede to specialists Paul Marek (Virginia Tech) and William Shear (Hampden‑Sydney College) for analysis. Only one other species of Illacme has ever been discovered: Illacme plenipes, from San Benito County, California, about 150 miles (240 kilometers) from Lange Cave. With up to 750 legs, I. plenipes is the leggiest millipede on the planet. "I never would have expected that a second species of the leggiest animal on the planet would be discovered in a cave 150 miles away," Marek said in a statement. The researchers dubbed the new species Illacme tobini after Ben Tobin, a cave specialist at Grand Canyon National Park who organized the survey that uncovered the new millipede. After the discovery, researchers spent several years looking for more specimens, checking around Lange Cave and 63 other locations in the Sierra Nevada foothills. They turned over leaf litter, logs, and rocks, but found nothing. As a result, the new species is known only from the single male found in Lange Cave, a marble cavern in woodland habitat at the base of Yucca Mountain. The eyeless millipede may feed on fungus, the researchers wrote on Oct. 20 in the journal ZooKeys. Its ninth and tenth leg pairs have been converted into gonopods, the millipede version of penises. These specialized limbs are covered in spikes and shovel-like projections that shuttle sperm from male to female. The millipede also sports about 200 pores that secrete an unidentified substance—perhaps a chemical defense against predators. Researchers say it remains unclear whether Illacme tobini lives solely in caves or can also be found in typical millipede hideouts, such as the undersides of rocks. Illacme plenipes was discovered in 1928, and Illacme tobini is only the second Illacme species to be described, 90 years later. Both species belong to the secretive family Siphonorhinidae, which contains just 12 known species. Illacme species are the only North American representatives; other family members occur in Vietnam, South Africa, India, Indonesia, and Madagascar. The family likely reached these disparate regions when its ancestors spread across the ancient supercontinent Pangea and were separated when it broke apart about 200 million years ago, the researchers wrote.

Alongside many spiders, pseudoscorpions, and flies, cave explorers found a tiny threadlike millipede in unexplored dark marble caves in Sequoia National Park. The specimen was sent to diplopodologists Bill Shear and Paul Marek, who recognized it as an evolutionary cousin of Illacme plenipes. The new species has "only" 414 legs compared with its relative's roughly 750, yet it shares bizarre anatomical features, including a body bearing about 200 poison glands, silk-secreting hairs, and four penises. The study was published in the open-access journal ZooKeys. The new millipede, named Illacme tobini after cave biologist Ben Tobin of the National Park Service, is described by its discoverer Jean Krejca (Zara Environmental LLC) and millipede taxonomists Paul Marek (Virginia Tech) and William A. Shear (Hampden–Sydney College). "I never would have expected that a second species of the leggiest animal on the planet would be discovered in a cave 150 miles away," says Paul Marek, an assistant professor in the Department of Entomology at Virginia Tech. Its closest relative lives under giant sandstone boulders outside San Juan Bautista, California. In addition to its extreme number of legs, the new millipede has bizarre-looking mouthparts of unknown function; four legs modified into gonopods (male reproductive appendages); a body covered in long, silk-secreting hairs; and paired nozzles on each of its more than 100 segments that eject an unknown defensive chemical. The authors note that exploring and documenting Earth's biodiversity can help prevent anonymous extinction, in which a species disappears before its ecological role, potential benefits to humanity, or intrinsic beauty are known.

Marek PE, Krejca JK, Shear WA (2016) A new species of Illacme Cook & Loomis, 1928 from Sequoia National Park, California, with a world catalog of the Siphonorhinidae (Diplopoda, Siphonophorida). ZooKeys 626: 1–43. DOI: 10.3897/zookeys.626.9681

Additional information: Funding from a National Science Foundation Systematics and Biodiversity Sciences grant to J. Bond, P. Sierwald, W. Shear, P. Marek, and T. Jones (DEB-1256139), and from a Virginia Tech USDA NIFA Hatch Project (VA-160028).

Millipedes, the little blunt-headed invertebrates with a habit of coiling up like baby ferns, rarely live up to their name. In Latin, millipede means "thousand feet," though the majority of these arthropods do not surpass the hundred-leg mark. That is not to say these critters want for feet—they have plenty. A newly described species, which was found living alone in a small California cave, almost does the millipede name justice.