Intraspecific variation and taphonomy of a new erymid lobster (Crustacea: Decapoda) from the Middle Jurassic of Belmont (Beaujolais, France)

Erymid lobsters are relatively common in Jurassic rocks, but usually only occur as isolated carapaces or chelae. As a consequence, intraspecific variation, possible sexual dimorphism and heterochely remain poorly known in this group. New material from the Middle Jurassic (Aalenian) of Belmont, France, consists of specimens belonging to approximately 20 individuals with well-preserved carapaces retaining both chelipeds. A re-evaluation of selected taxa of the Erymidae is presented, in which Eryma, Palaeastacus and Erymastacus are considered valid genera. However, Stenodactylina is interpreted to be a junior subjective synonym of Erymastacus. Intraspecific variation in the length and curvature of fingers in Erymastacus lagardettei nov. sp., is highlighted, raising doubts as to the relevance of isolated chelae as the basis for new species designation. Interestingly, carapaces from Belmont often exhibit damaged posterior parts, which are here tentatively interpreted as cephalopod scavenging marks.