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Pazinato, Paula G.; Jauvion, Clement; Schweigert, Guenter; Haug, Joachim T. and Haug, Carolin (2020): After 100 years: a detailed view of an eumalacostracan crustacean from the Upper Jurassic Solnhofen Lagerstatte with raptorial appendages unique to Euarthropoda. In: Lethaia, Vol. 54, No. 1: pp. 55-72 [PDF, 8MB]


The Solnhofen Konservat-Lagerstatte yields a great number of remarkably preserved fossils of eumalacostracan crustaceans that help us understand the early radiation of several groups with modern representatives. One fossil from there, Francocaris grimmi Broili, 1917 is a small shrimp-like crustacean originally described about 100 years ago as a mysidacean crustacean (opossum shrimps and relatives) from latest Kimmeridgian - early Tithonian (Upper Jurassic) of the Solnhofen Lithographic Limestones of Southern Germany. New material with exceptionally preserved specimens, allied with modern imaging techniques (mostly composite fluorescence microscopy), allows us to provide a detailed re-description of this species. The most striking feature of Francocaris grimmi is an extremely elongated thoracopod 7 with its distal elements forming a spiny sub-chela. This character supports a sister group relationship of Francocaris grimmi with Eucopiidae, an ingroup of Lophogastrida, pelagic peracaridans common in marine environments throughout the world. We also discuss other supposed fossil representatives of Lophogastrida, identifying all of them as problematic at best. The structure of the sub-chela in F. grimmi indicates an original use in raptorial behaviour. Francocaris grimmi appears to be unique in possessing such a far posterior sub-chelate appendage as a major raptorial structure. In most representatives of Euarthropoda in which sub-chelate appendages occur and are used for food intake, they are usually closer to the mouth.

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