Opilioacariformes is the rarest order of mites.  Less than two dozen species are known from around the world, primarily from the tropics and subtropics.  Individuals are relatively large (2-3 mm), long-legged, and have leathery bodies gray to lilac or bluish in color and resemble small opilionids with banded legs.  Opilioacarans may be the 'missing link' between the two major orders (Acariformes & Parasitiformes) of mites.  For example, they have a pair of finger-like processes that are thought to be homologous with the parasitiform tritosternum and have large dentate rutella like many acariformans.