The Stenotritidae are the smallest of all formally recognized bee families, with only 21 species in two genera, all of them restricted to Australia. Historically, they were generally considered to belong in the family Colletidae, but the stenotritids are presently considered their sister taxon, and deserving of family status. Of prime importance is the stenotritids have unmodified mouthparts, whereas colletids are separated from all other bees by having bilobed glossae. Fossil brood cells of a stenotritid bee have been found in the Pleistocene of the Eyre Peninsula, South Australia.