Shark diversity is awesome!

Ever heard of a shark with wings? Aquilolomna milarcae, a.k.a. the Eagle shark, lived in the late Cretaceous. It had a wingspan of 1.9 metres!

Of course, these “wings” weren’t like the ones on birds. They were long fins that helped the Eagle shark to glide slowly through the water. It didn’t need to go fast because it (probably) lived on a diet of plankton. Scientists note that it shared physical similarities with plankton feeders alive today.

You can find out more about the Eagle shark and its shape by visiting New Scientist magazine.

We can’t see Eagle sharks anymore, but there are still some very unusual sharks swimming in the world’s oceans.

Hammerhead shark

One of the world’s most famous sharks has to be the Hammerhead shark. It has a distinctive head shaped like, yes you’ve guessed it, a hammer.

Many people don’t realise that the Hammerhead is not a single species. There are ten species of Hammerhead shark. The smallest is only 90 centimetres long and the largest grows to 6.1 metres.

It’s not only the length that varies between species. There are differences in the shape of their “hammers” too. The Scalloped hammerhead shark has a line of notches across the front of its hammer, giving it a wavy scalloped edge. The Great hammerhead has a straight edge with one deep notch in the middle.

Having a head shaped like a hammer helps these sharks to find food. Because their eyes are set far apart, with one on each end of the hammer, these shark have a very wide field of vision.

The hammers also carry sensory equipment that enable the sharks to detect electrical signals coming from their prey. Other shark species share this ability. The advantage of the hammer shape is that it provides more space for this equipment.

Whale sharks have patterns unique to the individual on their backs
Whale sharks

Megamouth shark

If the Megamouth shark is lesser known, it shouldn’t be. Who can forget a shark with a name like Megamouth? Its scientific name is possibly even better. In Latin this fish is called Megachasma pelagios.

As the name suggests, Megamouth has an extremely large mouth. On a 5 metre long individual, the mouth is 1.3 metres across. We don’t have to worry about being swallowed up by it however. This species lives on plankton.

You’d have to search hard to see Megamouth. It lives in the deep ocean and comes to the surface at night. Scientists first knew of its existence in 1976 when one fish became tangled in an anchor off Hawaii.

Encounters with Megamouth are so rare that scientists have no idea about the size of its population.

Whale shark

When asked to name the world’s biggest fish some people say “the whale of course!” That’s not quite right because the whale is an air breathing mammal whose ancestors lived on land.

However, just to keep things confusing, the world’s biggest fish has “whale” in its name. It is the whale shark.

Whale sharks are usually around 14 metres long but can grow up to 18 metres. That’s around twice the length of the Great white shark.

Whale sharks are easy to recognise. Not only are they huge, their backs are decorated with pale spots and stripes. In the same way that our finger prints are unique, each individual whale shark has a unique pattern on its back.

Scientists aren’t sure how long whale sharks live for. Recent attempts at measurement suggest up to 130 years.

Greenland shark

Elderly whale sharks are mere babies next to the oldest Greenland shark individuals. Research shows that Greenland sharks can live for up to 400 years. This makes them the oldest vertebrates on Earth.

Greenland sharks grow incredibly slowly, just one centimetre a year. They also take a very long time to mature. Females don’t reproduce until they are around 150 years old. With all the environmental issues we’re facing, this makes the Greenland shark population incredibly vulnerable.

Glow in the dark sharks

In 2021 scientists in New Zealand have found that three species of deepwater shark glow in the dark. These are the Kitefin shark, the Blackbelly lantern shark, and the Southern lantern shark.

The Kitefin is 180 centimetres long and is now the world’s largest glowing vertebrate!

You’d think that lighting up would make these sharks stand out for miles, but not so. Scientists think that the bioluminescence acts as camouflage when the sharks are seen from below, silhouetted against the weak sunlight from above. This may help the sharks when hunting or protect them from predators.

To see a photograph, visit this report on the Guardian website. You might also be interested in reading this article about the important role that sharks play in ecosystems.

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