The word "Family Petromyzontidae" refers to a type of fish commonly known as lampreys. Synonyms for this family of fish include jawless fish, lamprey eels, and slimy eels. Lampreys are characterized by their unique cylindrical-shaped bodies and their lack of jaws. These fish have been around for nearly 360 million years, and they play an important role in various ecosystems. While lampreys are not typically kept as pets, they are fascinating creatures to learn about and observe in their natural habitats. If you're interested in learning more about Petromyzontidae or any other type of fish, there are plenty of resources available online and in books.