A morphology-based parsimony analysis (50 taxa; 110 characters) focused on relationships among basal acariform mites places Eriophyoidea (formerly in Trombidiformes) within Nematalycidae (Sarcoptiformes). Although both taxa have worm-like bodies, this grouping is unexpected because it combines obligate plant inhabitants (Eriophyoidea) with obligate inhabitants of deep-soil or mineral regolith (Nematalycidae sensu stricto). The Eriophyoidea + Nematalycidae clade, which is strongly supported (Bremer =5; bootstrap =85%), retains moderately good support (Bremer=3; bootstrap=66%) when three ratio-based characters pertaining to body shape are excluded. A total of eleven unambiguous synapomorphies unite all or some of Nematalycidae with Eriophyoidea. These include an annulated opisthosoma, an unpaired vi seta on the prodorsum, fusion of the palp trochanter with the palp femur, and a large relative distance between the anus and the genitalia. Three of the four Triassic genera of eriophyoid-like mites were also included in our analysis. Although all four genera have been tentatively placed within a new superfamily, we found no support for the monophyly of this group. One other interesting result of the analysis is the placement of a "living fossil", Proterorhagia oztotloica (Proterorhagiidae), as sister to the rest of Acariformes. However, support for this relationship is weak.