The leggiest animal known on Earth

The leggiest animal known on Earth
With up to 750 legs, the millipede Illacme plenipes Cook and Loomis, 1928 (see photos) is the leggiest
animal known on Earth. According to Marek, Shear and Bond (2012), who provided a recent, detailed
redescription of the species (http://www.pensoft.net/journals/zookeys/article/3831/abstract/) in the
periodical Zookeys, it is endemic to the northwestern foothills of the Gabilan Range in San Benito
County, Silicon Valley, California. Illacme plenipes is only known from 3 localities in a 4.5 km2 area. At
present, two families are recognized in the order: Siphonophoridae and Siphonorhinidae. Among these
families, three genera occur in the United States and Illacme is the only known Western Hemisphere
representative of Siphonorhinidae.
Illacme plenipes was described by O.F. Cook and H.F. Loomis in 1928 from seven individuals collected
from a site located “a short distance after crossing the divide between Salinas and San Juan Bautista…in a
small valley of a northern slope wooded with oaks, under a rather large stone”. In 2005 and 2007, new
specimens were collected from near the type locality. Individuals of the species are strictly associated
with large arkose sandstone boulders (see photo), and are extremely rare, with only 17 specimens known
to exist in natural history collections. In contrast with its small size and unassuming outward appearance,
the microanatomy of the species is strikingly complex (see photos). Based on functional morphology of
related species, the extreme number of legs is hypothesized to be associated with a life spent burrowing
deep underground, and clinging to the surface of sandstone boulders.