Onychophora: Systematics

Living onychophorans are divided into two groups, the equatorial Peripatidae, and the Peripatopsidae of Australia and Asia. These differ little from each other, at least in their gross morphology. Cambrian onychophoran-like organisms were more diverse, but just how they were related to living onychophorans is not settled. Some of these fossils also resemble the tardigrades or "water bears", a clade of microscopic aquatic animals rather similar to the Onychophora.

The Onychophora are probably close relatives of tardigrades and arthropods, and are currently placed with those groups in a larger taxon called the Ecdysozoa, which is based on the common ability of its members to molt.