You probably know the typical “shark” shape: cylindrical and streamlined, like a torpedo, with a pointed snout and lots of sharp teeth. And yes, many sharks do fit this particular mold, like the great white or the blacktip reef shark. But sharks are actually quite diverse and come in many unique and unusual forms. Let’s check out some of the weirder sharks out there.
What a Big Mouth You Have…
We often think of sharks as being highly specialized predators that will eat just about anything in their path, and that is the case for a lot of them. However, there are three species that buck that trend: the whale shark, basking shark and megamouth shark are all filter feeders that swim with their mouths open, lazily straining tiny organisms from the water they take in and expel through their gills.
Of these, the strangest is the megamouth. A rarely encountered shark that prefers very deep waters, this shark was not even known to humans until 1976. Since then, over 60 encounters have been recorded. The body shape of the megamouth isn’t particularly unusual, but its head is another story. It’s very large and rounded, with a huge mouth that gives the shark its name. Unlike most sharks that have sharp teeth and protruding snouts, the megamouth features two rubbery lips and tiny teeth. It draws in plankton and small fish with small luminous spots around its mouth.
|A Megamouth Shark||Scientific Name: Megachasma pelagios|
What a Long Tail You Have…
The thresher shark at first glance may look like your average shark, until you realize that something seems a bit…out of proportion. Look again. Notice anything a little off? the tail of the thresher shark makes up half of its entire body! The thresher shark is named for its tail, which resembles a thresher or scythe. It uses its elongated upper tailfin to smack fish, stunning them so it can eat them.
There are three species of thresher shark, and they all prefer open offshore waters where they live mostly solitary lives. Though they can grow quite large (over 20 feet long!), they are not considered dangerous to humans.
|A Thresher Shark||Scientific Name: Genus Alopias|
What a…Uhm, Weird Head You Have…
But of all the odd-looking sharks, the strangest is undoubtedly the hammerhead. The heads of these sharks are extremely flattened so that from above, they look like a hammer or an uppercase letter “T”. The shark’s eyes are located on each end of this hammer shape. The unique head structure is scientifically known as a “cephalofoil” and comes in a number of shapes and sizes within the hammerhead family. The bonnethead, for example, features a rounded, shovel-shaped cephalofoil. Meanwhile, the winghead shark has a cephalofoil that can be as wide as half the length of its entire body.
Several theories have been put forth to explain the function of these strange structures. Some scientists believe it enhances the sharks’ field of vision, while others think the hammer shape helps increase the range of unique sensory receptors known as the ampullae of Lorenzini. Sweeping their head back and forth as they swim can help them better detect prey, such as their favorite treat: the stingray.
|A Hammerhead Shark (Genus Sphyrna)||A Bonnethead Shark (Sphyrna tiburo)|
What Strange Relatives You Have…
As weird as some modern day sharks are, they don’t hold a candle to their ancestors. Prehistoric sharks had features that would make a hammerhead’s cephalofoil seem downright normal by comparison. Helicoprion and Sarcoprion, for example, were very early sharks that had spiral “tooth whorls” in their lower jaws that gave them the appearance of having a buzz-saw blade in their mouth.
Stethacanthus was another ancient shark relative. Instead of the normal triangular dorsal fin that many of today’s sharks possess, Stethacanthus had a large anvil-shaped structure. The function of this modified fin is not known for certain, though scientists believe it may have been used in mating, or used to attach to other animals like the remora, a type of modern fish that uses a modified dorsal fin as a suction cup to hitch a ride on larger fish.
Probably the most unusual-looking prehistoric sharks were the Xenacanths, an order that included Xenacanthus and Orthacanthus. These ancient fish resembled eels more than sharks, with long tapering tails and a slender bodies. They also had a long spine projecting backwards from the head. Unlike most modern sharks, Xenacanths lived in freshwater rather than saltwater environments.
There are over 500 species of sharks, and countless different types of all shapes and sizes have swam the seas in the 450 million years since they first appeared on Earth. While the typical shark form has proven to be highly effective and efficient for these ocean predators, hundreds of millions of years of evolution has given rise to a highly diverse and unusual range of shark body types adapted to their specific needs. So the next time you think about sharks, give a thought to the strange ones out there.