Onychophora (from Ancient Greek, onyches, "claws"; and pherein, "to carry"), commonly known as velvet worms (due to their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, Peripatus), is a phylum of elongate, soft-bodied, many-legged panarthropods.[1][2] In appearance they have variously been compared to worms with legs, caterpillars, and slugs.[3] They prey upon smaller animals such as insects, which they catch by squirting an adhesive slime. Approximately 200 species 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.[4] Velvet worms are considered close relatives of the Arthropoda and Tardigrada, with which they form the taxon Panarthropoda.[5] 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 behaviour and for bearing live young.