👉 A calacanthus is a type of fish that belongs to the family Cetacea, which includes dolphins, whales, and porpoises. These fish are known for their streamlined bodies and ability to swim at speeds up to 50 miles per hour (80 km/h). Calacanthus have a unique adaptation called the "calacanth", which is a series of appendages that extend from the head and tail, forming a keel-like structure.
