Tonneleryon, a new gregarious polychelidan lobster from the early Toarcian Posidonia Shale of Holzmaden (Germany)

Abstract

Polychelidan lobsters are decapod crustaceans characterized by a peculiar morphology: four to five pairs of claws and a flattened body. They were first discovered as fossils long before being discovered in modern deep sea environments. Many aspects of fossil and extant polychelidan biodiversity and ecology still remain poorly understood. This paper documents a new species and genus of polychelidan lobster, Tonneleryon schweigerti n. gen., n. sp. from the Toarcian of Holzmaden (Baden Wurttemberg, Germany). It also re-describes ?Coleia sinuata BEURLEN, 1928, which was confused until now with the new species. Actually, ?Coleia sinuata was described on the basis of a single, poorly preserved, juvenile specimen. Tonneleryon schweigerti is characterized by large eyes, which suggest its vision played an important role in its life-habits. Specimens of Tonneleryon schweigerti are generally preserved in cluster of several individuals, a characteristic unique to this species. All specimens in these accumulation are of similar size and do not possess the characteristics of exuviae such as a split median line or disjunction of carapace and first pleonite. They therefore probably represent a mass-mortality assemblage and suggest this species was gregarious.