Hobbies And Interests
Sharks
Sharks come in over 500 different species, according to the Smithsonian National Zoological Park. In sharks, placoid scales cover the entire body and cartilage exists where the notochord -- a skeleton rod in fish acting similar to the spine in humans -- would normally be found. Shark species include the great white shark, made famous by the movie "Jaws," as well as whale sharks, hammerhead sharks, nurse sharks, silky sharks, blue sharks, and angel sharks. Sharks date back hundreds of millions of years; the average shark may go through 20,000 teeth in a lifetime.
Rays
Rays look like an elongated, flattened fish and contain a poisonous barb at the end of their long tail: This often spans several feet. Rays commonly hang out in shallow water, often burying themselves in the sand. Rays exist in all bodies of water around the world, with exception to the colder regions around the Arctic. Species of rays include various types of sting rays, manta rays, eagle rays, as well as varieties of devil rays.
Sawfish
Probably the most unusual type of cartilaginous fish -- at least physically -- is the sawfish, which sports a saw-like snout of several feet. The extended saw helps sawfish to capture their prey; according to National Geographic, the saw probes through plants and sand when searching for prey, but can also detect electrical fields nearby, leading them to food sources. Large members of the sawfish clan can grow several feet in length, some reaching into the teens. Seven different species of sawfish exist and are classified as either part of the Pristis or Pectinata group.
Classification
Cartilaginous fish -- also known as Chondrichthyes -- make-up about 900 species total. All of the species either fall under two subclasses, including Holocephali and Chimaeriformes. Rays, fall under the order Batoidea; sharks on the other hand, are Elasmobranchii.