|Gonadactylus glaborous in a threatening posture at the mouth of a burrow. Image provided with permission from Roy Caldwell, U.C. Berkeley.|
There are approximately 350 species described to date, ranging in size from 2 to 30 cm (the length of a lima bean to the size of a lobster). The systematics of the Stomatopoda is contentious. It is known that the Stomatopoda were distinguished as a separate group from the rest of the Eumalacostraca very early in the history of the group. Sometimes, they are placed just outside of that group, but the evidence is not yet clear. Their extremely modified raptorial appendages and unusual nervous and digestive systems significantly distinguish them from the rest of the Eumalacostraca.