Decapods (Crustacea: Brachyura) from the Jurassic of Germany and Lithuania, with descriptions of new species of Planoprosopon and Tanidromites

Abstract

A Callovian erratic boulder from Pleistocene glacial drift deposits of NE Germany yielded a ‘prosopid’ crab, which is described here as a new species of the genus Planoprosopon SCHWEITZER FELDMANN & LAZAR, Planoprosopon quadratum. It represents the first unequivocal record of Planoprosopon from the Middle Jurassic and thus one of the stratigraphically oldest records of the genus. Another new species, Planoprosopon thiedeae, is described from the Kimmeridgian of SW Germany. Tanidromites lithuanicus n. sp., a member of Tanidromitidae, is recorded from the Callovian of Lithuania. It is compared with new well-preserved material of other representatives of this genus. Tanidromites richardsoni (WOODWARD) is recorded for the first time from the Bajocian of SW Germany. Tanidromites insignis (V. MEYER), Tanidromites sculpta (QUENSTEDT), and Tanidromites scheffnerae n. sp., all coming from the Kimmeridgian of SW Germany, are briefly described. Prosopon aequilatum V. MEYER is excluded from Tanidromites and now assigned to Eodromites PATRULIUS, and a neotype is designated for this species. Possibly, the early diversification of crabs took place during the Middle Jurassic in more temperate, Subboreal shallow water areas lacking reefal habitats and accelerated when reefs occupied these areas in the Late Jurassic.