epiproct

Epiproct is a term used in invertebrate anatomy to refer to a posterior dorsal plate or lobe on the terminal body region. The precise form and position of the epiproct vary across groups, and in different phyla it is associated with other tail or pygidial structures such as the telson, hypoproct, or paraprocts. The name derives from Greek, roughly meaning “upon the anus.”

In insects, the epiproct is typically the dorsal plate of the last abdominal segment. Its shape can range from a small process to a more extensive plate and it may be modified or reduced in different taxa. The epiproct often lies near the cerci and paraprocts and can be an important taxonomic character in groups such as mayflies and other orders where the terminal abdominal morphology aids species identification.

In crustaceans, especially malacostracans, the epiproct is involved in the tail region and may be described as a dorsal component of the telson or as a small plate associated with the tail fan. Its presence, absence, or distinctive shape is used in systematics of certain crustacean lineages.

In annelids, the epiproct refers to the dorsal portion of the pygidium, the last body segment, and is part of the terminal projec­tion along with the ventral hypoproct. The epiproct can be a simple plate or a more elaborate structure depending on the species.

Etymology reflects its position near the anus. See also telson, hypoproct, paraproct, and pygidium.