Phyllocarida

Phyllocarida is a subclass of Malacostraca, a group within the larger crustacean class. These ancient crustaceans are characterized by their flattened, leaf-like carapace that covers most of their body. Unlike many other malacostracans, their carapace does not fuse with the tergites of the thorax. Phyllocarids possess a long, segmented abdomen, which is fully exposed. They typically have multiple pairs of pleopods on this abdomen, which they use for swimming. Their antennae are well-developed, and they often have large, stalked eyes. Phyllocarids are primarily marine and are found in a variety of habitats, from shallow coastal waters to the deep sea. They are generally filter feeders or detritivores. The subclass includes only a few extant (living) orders, with the most well-known being the Leptostraca. Fossil evidence suggests that phyllocarids were much more diverse and abundant in ancient seas. Their lineage extends back to the Paleozoic Era, making them some of the oldest known crustacean groups. The Neocaridina genus, often seen in the aquarium trade, is a freshwater shrimp and not a phyllocarid.