Uropoden

Uropods are a pair of appendages found at the posterior end of many arthropods, particularly crustaceans and the extinct chelicerates known as eurypterids. They are typically jointed and may vary significantly in form and function depending on the species. In some crustaceans, such as shrimp and lobsters, uropods are flattened and paddle-like, contributing to swimming and locomotion. They can be used for rapid backward escape movements by flicking water. In other groups, like isopods, the uropods might be more segmented and serve diverse purposes including respiration or sensory perception. In some aquatic crustaceans, they can also be involved in the formation of a "tail fan" which is used for steering and propulsion. The specific structure and arrangement of uropods are often important taxonomic characteristics used by scientists to identify and classify different arthropod species. Their evolutionary origins are thought to be linked to the modification of ancestral appendages.