Mantis shrimp (Stomatopoda) are extant, marine, predatory arthropods, but these malacostracan pancrustaceans are also occasionally preserved in fossil assemblages, particularly in Carboniferous and Cretaceous deposits. Carboniferous species fall into two suborders—Palaeostomatopodea and Archaeostomatopodea—and represent the ancestral forms that gave rise to modern lineages. Herein, we describe hitherto unknown specimens belonging to the archaeostomatopod genus Tyrannophontes from the Pennsylvanian-aged Wea Shale Member, eastern Nebraska. We explore the preservation of these fossils using scanning electron microscopy and energy dispersive X-ray spectroscopy. These approaches reveal additional morphological characteristics, including unique appendicular data, such as the earliest occurrence of biramous gilled appendages in Stomatopoda. We suggest that further examination of black shales will likely uncover novel records of these rare pancrustaceans.