A group of legless, serpentine animals that fall under the category of amphibians, often mistaken for snakes or worms. Unlike other amphibians, they have a unique trait of having a ringed, worm-like body. They belong to the broader group of animals and are a subcategory within it. Despite their resemblance to squids and bivalves, they are not mollusks but are often studied in conjunction with these creatures due to their unique biological characteristics.