biramous appendage

A biramous appendage is a limb that has two branches. This type of appendage is thought to have evolved from a double-branched limb, with a basal part called a protopodite that bears two branches: an inner endopodite and an outer exopodite.1

While many crustaceans have adapted their appendages, the biramous structure is a foundational form. For example, the walking legs of many malacostracans have become uniramous, meaning they have only one branch, by not developing the exopodite. The appendages of crustaceans can vary greatly in form and function, changing throughout their life cycles and serving purposes such as sensory input, swimming, and feeding.1