Sharks Outlived Dinosaurs — and Here’s How They Did It

Shark fossils have been found dating back to more than 400 million years, meaning they are one of the oldest creatures on the planet, outliving even the dinosaurs, surviving mass extinctions, and extreme weather changes.

So how did they do it? Well, they are adept at evolving to suit their environments, and have quite the record of adapting when needed. Here are just some of the ways they’ve done it.

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July 06, 2021

By: Lucy Sherriff

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Swimming

They’ve figured out how to swim without expending too much energy, and to maneuver quickly and with agility to help them hunt prey. Their bodies taper at both the tail and the nose, meaning they’re streamlined and reduce water resistance. They have dermal denticles, which are sharp scales covering the skin of most shark species, providing protection and decreasing drag when they swim — meaning they’re also pretty noiseless. They also have cartilage rather than bone, which is lighter and more flexible, and allows them to conserve energy and swim long distances. Their livers produce a fatty oil called squalene, which helps them remain afloat. On top of all that, their pectoral fins allow them to dive, swim upward, and change direction at a moment’s notice. Many shark tails, also known as caudal fins, are larger on top than the bottom, allowing them to swim more efficiently. Some sharks also have a horizontal keel on their fins, a mechanism which reduces turbulence and allows them to swim faster.

Teeth

Not all shark teeth are the same, but many sharks have evolved from having conical, non-serrated teeth to triangular teeth that are flat and serrated like a steak knife, helping them bite off chunks of flesh from their prey. Other bottom-dwelling sharks that feed on mollusks have teeth that are more suited to grinding shells and cracking them open, while goblin sharks have needle-like teeth to pierce fish. When a shark loses a tooth, a new one grows to replace it.

Migration patterns

Sharks can swim for thousands of miles in search of food, and can lounge in deep and shallow water, warm and cold water, depending on what’s needed. They have flexibility in their diet, meaning they can switch prey if their usual food is in short supply.

Sixth sense

Sharks have a sixth sense — the ability to sense electromagnetic fields both from the Earth and from the electric fields marine animals create when they move. Their snouts are covered with sensory organs, called ampullae of Lorenzini that pick up electric signals from potential prey. They use this for navigation for hunting prey — especially food that’s buried under the sand. Hammerhead sharks in particular are very good at this due to their head shape, which essentially acts like a metal detector, helping it find prey under the sea bed. Sharks can detect vibrations in the water through cells they have in the middle of their bodies, allowing them to sense ripples in the water so they can hunt at night. Their inner ears also perceive nearby movement.