Perimecturus information

Perimecturus Temporal range: Early Carboniferous (Viséan to Serpukhovian), 345–324 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of P. rapax from the Bear Gulch Limestone
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Stomatopoda
Family:	†Perimecturidae
Genus:	†Perimecturus Peach, 1908
Type species
†Anthrapalaemon parki (= †Perimecturus parki) Peach, 1882
Other species
†P. rapax Schram & Horner, 1978
Synonyms
Synonyms of Perimecturus Palaesquilla Peach & Horne, 1903 (nomen nudum) Synonyms of P. parki Anthrapalaemon parki Peach, 1882 Palaesquilla parki Peach & Horne, 1903 (nomen nudum) Perimecturus communis Peach, 1908 Perimecturus parki duplicicarinatus Peach, 1908 Perimecturus stocki Peach, 1908

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 (only after Archaeocaris). 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.

Unlike other Paleozoic mantis shrimps which had narrow, shrimp-like bodies, Perimecturus had a wide and flattened body more closely resembling that of a lobster. This condition is also seen in modern mantis shrimps, but Perimecturus would have developed this shape separately from them in an example of parallel evolution. Members of this genus had a wide carapace with five ridges, in addition to six other ridges running down the abdomen. The two species differ primarily in the tail fan, with P. rapax having a longer telson spike and lacking the bristles seen in P. parki. In addition, P. parki lacks the serrations on the telson and uropods that P. rapax has. Perimecturus is one of the largest Paleozoic mantis shrimps, with the largest known specimen of P. parki reaching a total length of 15 cm (5.9 in). However, most specimens are notably smaller than this.

Both Perimecturus species lived in fully marine habitats, and are believed to be intolerant of lower salinities. Like all other mantis shrimps, they would have been carnivores that handled prey with their raptorial thoracic appendages. Because the walking appendages are poorly preserved, it remains unclear whether Perimecturus would have been benthopelagic and swam just over the seabed like other early mantis shrimps.