The family Crotalomorphidae, fam. nov., with type genus Crotalomorpha, gen. nov., are described to validate these names, the previous usage of which was based on nomenclatorially unavailable names. This monobasic family and genus is based on three physogastric, gravid females representing the type species, Crotalomorpha camini sp. nov., collected from beneath the elytra of harpaline carabid beetles of the subgenus Agonoderus, genus Stenolophus, in Kansas and Nebraska, USA. The unique mixture of primitive and derivative characteristics of this taxon and its relationships among others of the cohort Heterostigmata are discussed, and a rationale for considering Crotalomorphidae as the sister group of Dolichocybidae is presented.