Praearcturus

Praearcturus is an extinct genus of arthropod, most likely a scorpion, known from the Devonian period of what is now Britain. It is the only genus in the family Praearcturidae and contains the single species P. gigas.

Praearcturus Temporal range: Lochkovian PreꞒ Ꞓ O S D C P T J K Pg N
Praearcturus sp.
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	incertae sedis
Family:	†Praearcturidae
Genus:	†Praearcturus Woodward, 1871
Species:	†P. gigas
Binomial name
†Praearcturus gigas Woodward, 1871
Synonyms
Bennettarthra annwnensis? Fayers, Trewin & Morrissey, 2010

Taxonomic history

The type fossil was discovered in Rowlestone, England, and was described as a giant isopod in 1871 by Henry Woodward.^[1][2] It was later interpreted as a scorpion by Rolfe (1980), who claimed that it was based on the personal communications by L. Størmer (1974) and E. N. Kjellesvig-Waering (1978) and the published figures by Rolfe (1969).^[3] While type specimen is from the Lower Devonian of Old Red Sandstone,^[4][5] single tergite remain is known from Lower Devonian of Wyoming and fragmentary cuticles referrable to this genus is known from Famennian of Portishead.^[4][6] Based on comparisons to modern scorpions, the species could have reached a total length of nearly 1 metre (3.3 ft), possibly making it one of the largest scorpions known.^[7]

However, a 2024 study was uncertain whether Praearcturus could be identified as a scorpion, due to the fragmentary material showing no definitive features of scorpions and arachnids.^[5] Braddy (2024) also questioned its identity as a scorpion and considered that the original interpretation as a crustacean is more likely, with the supposed pedipalp (claw) of a scorpion more likely being a cheliped of a crustacean. He further supported his argument based on the "grooves and pustular ornament on its carapace and cheliped, and recurved first tergum", and suggested that Bennettarthra could be synonymous with Praearcturus as both taxa show similar morphological features.^[8] In a 2024 conference abstract, however, it was noted that a redescription of Praearcturus is in preparation, which the authors claim confirms the genus' scorpion identity.^[9]