With approximately 1,500 extant species, freshwater crabs (Decapoda: Brachyura) are among the most diverse decapod crustaceans. Nevertheless, their fossil record is extremely limited: only Potamidae, Potamonautidae and Trichodactylidae are reported up to the Eocene of the Neotropics so far. This work documents unusually large decapod claws from the Upper Cretaceous (Campanian) continental deposits of Velaux and vicinity (southern France), in close association with large vertebrate remains. In addition to (1) the systematic assignment of these claws, the study addresses (2) the salinity trends in the deposit environment from its faunal assemblage and the elementary chemical patterns of fossils, and (3) the likely scenario for their auto/allochtony in the Velaux fluvial system. These claws belong to a new taxon, Dinocarcinus velauciensis n. gen. n. sp., referred to as Portunoidea sensu lato, a group of “true” crabs nowadays linked to marine systems. However, the faunal assemblage, the claw taphonomy and the carbonates Y/Ho signatures support their ancient freshwater/terrestrial ecology, making them the oldest reported continental brachyurans and extending the presence of crabs in freshwater environments by 40 Ma. Either as primary or as secondary freshwater crabs, the occurrence of these portunoids in Velaux is an evidence for the independent colonizations of continental environments by multiple brachyuran clades over time, as early as the Campanian.

中文翻译：

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最古老的淡水螃蟹：恐龙骨头上的爪子

淡水蟹（大约十万种）的现存物种约为1500种，是十足类甲壳动物中种类最多的一种。然而，它们的化石记录极为有限：迄今为止，据报道直到新新世始新世才有Pot科，Pot科和毛act科。这项工作记录了Velaux及其附近地区（法国南部）上白垩纪（Campanian）大陆沉积物中异常大型的十足足爪，与大型脊椎动物残骸密切相关。除了（1）这些爪的系统分配之外，该研究还针对（2）从动物群的组合和化石的基本化学模式出发的沉积环境中的盐度趋势，以及（3）它们的自动/分配作用的可能情况在Velaux河流系统中。这些爪子属于新的分类单元，Dinocarcinus velauciensis ñ。gen。。sp。，被称为Portunoidea sensu lato，是当今与海洋系统相关的一组“真”蟹。然而，动物的组合，爪形的爪状排列和碳酸盐的Y / Ho签名支持了它们古老的淡水/陆地生态学，使其成为最古老的大陆短吻鳄，并将蟹在淡水环境中的存在扩展了40 Ma。无论是作为初级或次级淡水蟹，在Velaux中这些门类动物的出现都证明了早在Campanian时期，多个腕壳类进化枝就在大陆环境中独立定居。