Petromyzontidae, commonly known as lampreys, are a family of jawless fish found in both freshwater and marine environments. They are characterized by their elongated bodies, a round mouth filled with sharp teeth, and a lack of paired fins. Lampreys are known for their unique feeding habits, as many species are parasitic, attaching to other fish to feed on their blood and bodily fluids. These ancient creatures have a long evolutionary history, dating back over 360 million years. Lampreys play important ecological roles in their habitats, serving as both predators and prey. Their life cycle includes a larval stage, where they live buried in sediment, before transforming into adults that migrate to spawn in freshwater rivers.