By Blaise Jones
There are 10 orders of shark: saw sharks, angel sharks, dogfish, bramble sharks, cow sharks, frilled sharks, bullhead sharks, carpet sharks, mackerel sharks, and ground sharks. While each of these groups of shark have all the needed traits necessary to be classified as sharks, each group possesses traits and adaptations that make them different from each other.
The largest group of shark are the ground sharks (Carcharhiniformes). These are the “sharkiest” of the sharks, and conform to the body shape that most people imagine when they think of sharks. Some of the most famous species of shark are classified as ground sharks, such as the tiger shark and the hammerhead sharks.
Ground sharks are defined by their elongated snouts and by having a nictitating membrane, a special eyelid that provides ocular protection. There are more than 200 different shark species that are classified as ground sharks, making up half of all the known sharks species.
Bull by the Horns
Bullhead sharks (Heterodontiformes) are distinguished by their smaller size, typically less than five feet long, as well as their pig-like snouts and small spines on their fins. There are only nine species of bullhead sharks, two of which are the horn shark and Port Jackson shark.
Caught in a Bramble
The next group of sharks are the bramble sharks (Echinorhiniformes). There are only two species in this group, the prickly shark and the bramble shark. These two sharks are grouped together due to their thorn-like scales, which gives them a distinctive knobby appearance.
Despite their name, cow sharks (Hexanchiformes) do not have horns or udders. Cow sharks are set apart from others by how evolutionarily primitive they are. Thought to be the oldest living group of shark, cow sharks have six or seven gill slits, instead of the usual five all other sharks possess. Additionally, cow sharks only have one dorsal fin on their back near the tail.
Another odd trait cow sharks possess are their teeth. The top and bottom rows of their jaws have different types of teeth: the top row teeth are more typical looking dagger-like teeth and the bottom row having odd “cockscomb” teeth, many jagged teeth attached together at the base similar to the cockscomb on a rooster’s head.
A Frilling Discovery!
The categorization of the frilled shark (Chlamydoselachidae) is a contested subject. Some people consider it to be a cow shark due to their six gills and deep-water habitat. However, other biologists consider frilled sharks to be their own group due to its odd appearance and unique physiology.
The frilled shark has a long, eel-like body, with a single dorsal fin near the rear. While frilled sharks share the same number of gill slits as cow sharks, their gills possess several traits that set them apart from the cow sharks. Frilled shark gills have feathery tissue that protrude from the gills out into the water. The first gill slits on either side of the frilled shark are elongated and meet at the bottom, forming a ring around the frilled shark’s neck.
Additionally, frilled sharks have a unique tooth shape as well. Each individual tooth has three prongs, giving them the appearance of tridents. It is thought that these teeth help the frilled shark catch squid and octopus, its typical prey.
Mackerel sharks (Lamniformes) include the most famous shark of all, the great white. Mackerel sharks have torpedo-shaped bodies with very conical snouts. One of the key features mackerel sharks possess is a heat-retaining circulatory system. While not truly warmed blooded, mackerel sharks are able to retain their body heat better than other sharks, allowing them to swim in much colder waters than other species of sharks.
Really Ties the Sea Together, Man
Carpet sharks (Orectolobiformes) derived their name from their carpet-like coloration patterns and the fleshly barbs that hang from their face like the tassels of a carpet. This group includes 31 different species, most of which are bottom-dwelling, sluggish species such as the nurse shark and wobbegong shark. The whale shark, largest shark living today, is one of the most famous members of the carpet shark group. The whale shark, which can grow as long as a city bus, spends its days swimming through open water in every ocean on the planet.
Weirdest Thing You Ever Saw
There are nine species of sawsharks (Pristiophoriformes) each possessing a large rostrum with teeth to extend from the sides, resembling a saw. These saw-like rostrums are specialized hunting tools that serve as both a fish finder and a weapon for hunting. Electro-sensing organs on the underside of the rostrum locate fish and the serrated teeth on the sides can stun the fish, which swung back and forth, as well as chop them into pieces. The rostrum can be used to dig into the sediment to uncover hiding prey.
Why Mailmen don’t like to Swim
The dogfish group (Squaliforme) are a varied group of shark, ranging from the one of the smallest shark species, the dwarf lantern shark (eight inches), to one of the world’s largest, the Greenland shark, which can grow to longer than 20 feet. All dogfish sharks are ovoviviparous, which means they their offspring hatch inside the mother’s body and are born fully formed, including a full set of teeth. Immediately after being born, dogfish sharks are ready to hunt immediately.
There are 15 species of angel sharks (Squantiniformes). Angel sharks have a flat body shape and bury themselves under the sand of the sand, waiting to ambush prey from below. While they possess many similar characteristics to their cousins the skates and stingray, the mouth of an angel shark is on the front of its head, instead of below it, and their rear bodies are shark-like, with two small dorsal fins.
“The Encyclopedia of Sharks” by Steve Parker