The Strud crustacean fauna (Late Devonian, Belgium): updated review and palaeoecology of an early continental ecosystem

Arthropods were the first known animals to colonise land habitats, with myriapods and arachnids having done so at least by the Silurian. Much later, several lineages of Pancrustacea (hexapods and the paraphyletic crustaceans) also ventured onto land; the hexapods by the Early Devonian, and later at least four other groups of crustaceans, namely isopods, amphipods, ostracods and decapods, most of which generally colonised the continental water bodies. All faced a series of challenges (in particular: gas exchange; desiccation; reproduction; osmoregulation; and exposure to ultraviolet radiation), resulting in many morphological, physiological and ecological adaptations. Nonetheless, whether they reached land via saltwater or freshwater remains poorly documented, mainly because relevant localities are few. The Famennian (Late Devonian) Strud locality in Belgium provided an exceptional source of information on early aquatic continental ecosystems and their plant, vertebrate and arthropod colonisers at a crucial step in the terrestrialisation process. Here, we review and update its crustacean fauna, which inhabited floodplain and temporary pool waters. New anatomical details of the notostracanStrudops goldenbergiLagebroet al., 2015, as well as a new genus and species of spinicaudatan, are described. We also discuss the ecology of this unique, early continental ecosystem and the insights it gives into the terrestrialisation process.