Revisional studies on Thoracophoracarus K. Viets, 1914 (Arachnida, Acari, Hydrachnidia, Arrenuridae)

Five species from Europe and Africa attributed to the genus Thoracophoracarus K. Viets, 1914 are redescribed from type material. Thoracophoracarus sinearcus (K. Viets, 1924), probably based on a deformed Arrenurus Dugès, 1834 male, is considered a species incerta. Thoracophoracarus mammosus (K. Viets, 1925) is synonymized with T. petioluriger (K. Viets, 1925). Thoracophoracarus cooki n. sp., T. silvarum n. sp. and T. felix n. sp. are described from Madagascar, representing a distinct species group endemic to the island, characterized by absence of idiosomal humps and round, not longish, acetabular fields. The phylogeny of the genus is discussed.