Families and genera of Holothyrina are redefined and redescribed A new family, Neothyridae, is created for the first Neotropical species, Neothyrus ana, n. gen., n. sp., from Iquitos area, Peru. Holothyrina is regarded as a suborder of Anactinotrichida, together with Gamasina and Ixodina. All similarities between Holothyrina and the order Opilioacarida are regarded as plesiomorphic. Holothyridae is regarded to consist of three genera: HolothyrusGervais, 1842 (typespecies H. coccinella Gervais, 1842), Hammenius n. gen. (type-species H. Jujuge n. sp.), and Thonius n. gen. (type-species Holothyrus longipes Thorell, 1882). Hammen ius ingii n. sp. is also described. Both Hammenius and Thonius are distributed from Seychelle Islands to New Guinea, but Holothyrus is restricted to Mauritius.