A review and revision of the Paleozoic proto-stomatopods results in the recognition of a new species of Tyrannophontes Schram, 1969, T. gigantion, from the Middle Pennsylvanian Mazon Creek, Essex biota. A new family, Daidalidae, and new genus, Daidal, are required to separate a previously recognized taxon, T. acanthocercus Jenner, Hof, and Schram, 1998. Both Perimecturus pattoni Peach, 1908 and Gorgonophontes cf. fraiponti (Schöllmann, 2004) appear at present to be best placed within Daidal, the latter as a new species, D. schoellmanni. The genus Gorgonophontes Schram, 1984 is allocated to a new family, Gorgonophontidae. Members of the family Tyrannophontidae reveal features of their maxillipeds that clearly relate them as a sister group to Unipeltata. A cladistic analysis of all known Paleozoic Palaeostomatopoda Brooks, 1962 and Archaeostomatopodea Schram, 1969 reveals a series of stem-group proto-mantis shrimp that lead to the crown-group Unipeltata Latreille, 1825.