Retropluma

Abstract: Decapod crustacean assemblages from the Middle Miocene (lower 'Badenian'=Langhian) volcanoclastic Plasťovce Beds (Sebechleby Formation) in the Slovakian part of the Novohrad-Nograd Basin comprise five species in five families (Callianassidae, Laomediidae, Munididae, Cancridae and Retroplumidae) and are dominated by the cancrid crab Tasadia carniolica (Bittner, 1884). Munida sp. constitutes the first record of this genus from Slovakia and the second from the European Neogene. Burrowing shrimp (Jaxea kuemeli Bachmayer, 1954) are associated with burrows tentatively attributed to this species. The occurrence of Retropluma slovenica Gasparic & Hyžný, 2014, previously recorded from the Lower Miocene of Slovenia, extends both the geographical distribution and stratigraphical range of the species. Differential decapod diversity at four localities in the Plasťovce area can be explained by collecting bias and palaeoenvironmental factors. The palaeosetting is interpreted as a muddy-bottom, nearshore zone with a water depth of approximately 100 m. Abundant articulated crabs suggest rapid burial. Third maxillipeds in open posture in some specimens may indicate respiratory stress of the animals, suggesting episodic events of rapid volcanoclastic flows responsible for killing crabs and promoting their preservation. Species composition of the decapod fauna of the Plasťovce Beds further strengthens similarities with Miocene faunas from the North Sea Basin.