Perimecturus is an extinct genus of mantis shrimp that lived during the Early Carboniferous period in what is now Scotland and the United States. The first known specimens were collected near the River Esk in Glencartholm, Scotland, and the genus was named in 1908 by Ben Peach, making it the second genus of Paleozoic mantis shrimp to be described. While many species have been classified in the genus since then, taxonomic revisions in the late 20th and 21st centuries have reassigned most of these to different genera, leaving two named species currently assigned to this genus. The type species, P. parki, was first named in 1882 as a species of Anthrapalaemon and is known from the Viséan-aged Glencartholm Volcanic Beds of Scotland. Fossils of a later species, P. rapax, have been found in the Bear Gulch Limestone of Montana and were first described by Frederick Schram.

Archaeocaris is an extinct genus of mantis shrimp that lived in North America during the Early Carboniferous period. Though it was placed as a member of the family Perimecturidae until 2008, it is currently deemed the only genus in the family Archaeocarididae, and contains two species. The type species, A. vermiformis, was described by Fielding Bradford Meek in 1872 from specimens collected at the base of the Waverly Group in Kentucky. A second species, A. graffhami, was named by Harold Kelly Brooks in 1962 based on a fossil found in the Caney Shale of Oklahoma, with additional remains later found in the Pilot Shale of Nevada.