Tumidochelia randyi, new genus, new species is described from the continental slope of the northern Gulf of Mexico at depths ranging from 482 to 2974 m. It is distinguished from the other genera and species of Tanaidomorpha by having: an inflated "shield-like" laterally compressed expansion of the inner distal side of the cheliped carpus, and a biramous uropod with a dorsal process on the inner distal margin of the protopod. Tumidochelia randyi is placed in the family Colletteidae Larsen & Wilson, although no phylogenetic analysis has been performed to support this designation.