ALT Despite their similar appearances to crabs, cyclids were not closely related to them, or any other decapods. In fact, their actual placement within crustacea is still somewhat controversial, and they have been flipped around multiple times, notably as potential relatives of copepods and fish lice on occasion. One example of a Mesozoic member of the group is Juracyclus, which is so far the only the member of the group known from the Jurassic, specifically the lower Jurassic Posidonia shale in Germany, hence the species name.
ALT Cyclids were among the only “classic” groups of Paleozoic arthropods to survive the Permian boundary extinction, with the other two being the Thylacocephala and Euthycarcinoidea Yunnanocyclus is known from some of the earliest Triassic sediments in China, this taxon lived only a few million years after the devastating Permian-Triassic boundary, showcasing how quickly life was able to recover in some areas.
ALT By the time of the Cretaceous, Cyclids are so far represented by only a singular family, the Alsasuacarididae, and what a weird family this was. Unfortunately it seems this family, and the Cyclida as a whole, died out during the KPg boundary event, alongside the non avian dinosaurs, but still what an incredible run they had. The namesake of the family, Alsasuacaris lived from the Albian all the way to the Maastrichtian. This specific species lived in Spain during the Albian-Cenomanian. These guys are quite the oddballs compared to other cyclids, as they’re quite small, only a few millimeters long, and features well developed orbits, flat carapaces, and most interestingly of all, were potentially ectoparasites on fish, which would make them the only family of cyclids that preformed this lifestyle.
