Nemertodermatida is a small group of marine invertebrates belonging to the phylum Platyhelminthes. They are characterized by their elongated, flat bodies and lack of a coelom, which is a body cavity found in more complex organisms. These creatures are typically found in marine environments, often living in sediment or among algae. Members of Nemertodermatida are known for their unique reproductive strategies and simple body structure. They possess a nervous system and exhibit a range of behaviors, including movement through ciliary action. Their ecological role includes being part of the benthic community, contributing to the overall biodiversity of marine ecosystems.