Thirteen new species of North American Testudacarus (Torrenticolidae: Testudacarinae) are described: Testudacarus deceptivus O'Neill & Dowling, sp. n., Testudacarus hitchensi O'Neill & Dowling, sp. n., Testudacarus harrisi O'Neill & Dowling, sp. n., Testudacarus dennetti O'Neill & Dowling, sp. n., Testudacarus dawkinsi O'Neill & Dowling, sp. n., Testudacarus radwellae O'Neill & Dowling, sp. n., Testudacarus kirkwoodae O'Neill & Dowling, sp. n., Testudacarus hyporhynchus O'Neill & Dowling, sp. n., Testudacarus smithi O'Neill & Dowling, sp. n., Testudacarus rollerae O'Neill & Dowling, sp. n., Testudacarus elongatus O'Neill & Dowling, sp. n., Testudacarus rectangulatus O'Neill & Dowling, sp. n., and Testudacarus oblongatus O'Neill & Dowling, sp. n. Testudacarus vulgaris Habeeb, 1954 is resurrected from synonymy with Testudacarus minimus and redescribed. Debsacarus (Habeeb, 1961), Testudacarus americanus Marshall, 1943, and Testudacarus minimus Marshall, 1943 are redescribed. All redescriptions are from original types. Species delimination was accomplished through examination of morphology, biogeography, and molecular phylogenetics of the barcoding region of COI. Other species are addressed and a key to world species is presented. For Testudacarinae, this represents the first published: 1) descriptions from multiple specimens (i.e. intraspecific variation); 2) colored photographs; 3) explicit illustrations and discussion of sexual dimorphism within the subfamily; 4) genetic data. A comprehensive testudacarine reference list is also included.
Keywords: Debsacarus; Hydrachnidia; Hydrachnidiae; Testudacarinae; Testudacarus; water mites.