Kalyptorhynchia is a suborder of rhabdocoel flatworms. It contains almost 600 species and has a cosmopolitan distribution.[1]
All kalyptorhynchs have an anterior muscular proboscis which is used to capture prey. The proboscis is located inside an invagination of the epidermis called the proboscis-sheath that is closed by a sphincter at the tip of the body. Another synapomorphy supporting the group is the incorporation of the axonemes within the cell body of sperm cells during spermiogenesis.[2]
Kalyptorhynchs are traditionally classified into two infraorders: Eukalyptorhynchia, with a cone-shaped proboscis, and Schizorhynchia, with a proboscis formed by two opposite parallel muscular sheets. However, molecular studies have shown that Eukalyptorhynchia is not a monophyletic group and further studies are necessary to improve the knowledge about the relationships of the different kalyptorhynch clades.