Onychophora

Onychophora Qnᵻ'kQf@r@ (from ονυχής, onyches, "claws"; and φέρειν, pherein, "to carry"), commonly known as velvet worms (due to their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus pəˈrɪpətəs (after the first described genus, Peripatus), is a phylum of elongate, soft-bodied, many-legged panarthropods. In appearance they have variously been compared to worms with legs, caterpillars, and slugs. They prey upon other invertebrates, which they catch by ejecting an adhesive slime. Approximately 200 species of velvet worms have been described, although the true number of species is likely greater. The two extant families of velvet worms are Peripatidae and Peripatopsidae. They show a peculiar distribution, with the peripatids being predominantly equatorial and tropical, while the peripatopsids are all found south of the equator. It is the only phylum within Animalia that is wholly endemic to terrestrial environments, at least among extant members. Velvet worms are generally considered close relatives of the Arthropoda and Tardigrada, with which they form the proposed taxon Panarthropoda. This makes them of palaeontological interest, as they can help reconstruct the ancestral arthropod. In modern zoology they are particularly renowned for their curious mating behaviours and the bearing of live young in some species. Velvet worms are segmented animals with a flattened cylindrical body cross-section and rows of unstructured body appendages known as oncopods or lobopods (informally: stub feet). They reach lengths between depending on species, with the smallest known being Ooperipatellus nanus and the largest known is Mongeperipatus solorzanoi. The number of leg pairs ranges from as few as 13 (in Ooperipatellus nanus) to as many as 43 (in Plicatoperipatus jamaicensis). Their skin consists of numerous, fine transverse rings and is often inconspicuously coloured orange, red or brown, but sometimes also bright green, blue, gold or white, and occasionally patterned with other colours.