New Early Jurassic hermit crabs from Germany and France

Abstract

Decapod crustaceans from the Early Jurassic of southern Germany have been described since the middle of the 19th century, often based on isolated chelae. Among them, the taxon Glyphea amalthei Quenstedt, 1854 from the Late Pliensbachian, has been interpreted in rather different ways and in fact, the original specimens belong to four different decapod crustacean species: a glypheid, an erymid, a ‘thalassinoid’ and a paguroid (hermit crab). The complicated taxonomy of this material is clarified here. New material of chelae and even of an almost complete specimen from Franconia, Germany, allows the description of a new family, genus, and species for the paguroid. Carapace morphology the outline of the chelae and the characteristic occlusal dentition of the fingers make it significantly distinct from all other previously described Jurassic paguroids. One specimen shows a remarkably anomaly, unique in fossil decapods so far: a small chela developed at the outer margin of a bigger one. One more paguroid represented by a few incomplete chelae and a cheliped co-occurring with Schobertella simonsenetlangi n. gen., n. sp. is described here as Cryptopagurus svenhofmanni n. gen., n. sp. A further new species, Schobertella hoelderi, comes from the Angulatenton Formation of southern Germany and extends the fossil record of paguroids now back to the Late Hettangian. The previously described Venipagurus mariae Collins, 2011 from the Sinemurian of Dorset, which was supposed to be the oldest hermit crab is here considered as dubiously placed within paguroids and perhaps could represent a stomatopod. All records of Schobertella n. gen. and Cryptopagurus n. gen. come from claystones or detritic limestones representing non-reefal but well-oxygenated to slightly dysoxic habitats. The paguroid genus Orhomalus Etallon, 1861, is recorded from the Early Jurassic by isolated chelae of two new species, Orhomalus arpi from the uppermost Toarcian of southern Germany, and O. dubrullei from the Upper Pliensbachian of northern France, thus expanding the previously known stratigraphical range of this genus significantly.