Sharks have been in the world since before the time of dinosaurs. Many facts are known and recorded about modern-day sharks, but scientists also study the sharks that existed millions of years ago.
Fossil remains of plants or animals that lived long ago have taught scientists many things about the existence of prehistoric sharks, those who existed before written records.
However, prehistoric sharks pose a problem for scientists trying to study them and make predictions about their size, what they ate, and other important facts.
Sharks do not have skeletons of bone. Instead, cartilage makes up the body structure of sharks. Usually, fossils contain remnants of bone or other hard material. Any fossil record found of prehistoric sharks is a coincidence~ some may call it luck!
When the shark died, it would land on rocks in the ocean leaving behind an impression. Fossilized shark teeth have also been extremely important in learning about prehistoric sharks. These types of fossils have been invaluable in helping scientists learn about prehistoric sharks.
All prehistoric sharks, except two, are now extinct or no longer in existence. The two prehistoric sharks currently living are the goblin shark and the frilled shark. Both of these species of sharks can trace their ancestry back for millions of years ~ true living fossils!
Incredibly, just as modern-day shark species are still being discovered, so are prehistoric shark species. As recently as 2015, a new species called Pseudomegachasma was discovered by scientists. This shark was a vegetarian and possessed the same type of teeth as a megamouth shark!
The world of prehistoric sharks offers some of the most extreme shark species. Here is a closer look at 4 of the unique prehistoric sharks: Megalodon, Stethacanthus, Xenacanthus, and Edestus.
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Megalodon
Megaladon is perhaps the most famous prehistoric shark and has found a place in modern-day movies and books. Few facts are known about this shark because the only fossil record of this species found and studied has been teeth and a few vertebrae, or small bones forming the backbone.
Scientists believe Megalodon is the largest shark to have ever lived, reaching lengths of 59 feet or greater and weighing 50-70 tons. This is three times as big as a great white shark! Its mouth alone was 7 feet wide, large enough for a very tall human to stand in it upright.
Megalodons were huge predators, and fossilized teeth have been found that were 7 inches long! They were so large that they feasted on huge prey like whales, seals, sea lions, and walruses.
Stethacanthus
Stethacanthus is a little-known prehistoric shark species, but it is definitely one weird fish! It was only about 2 feet long. Instead of a typical dorsal, or back, fin, it had a fin shaped like an ironing board. If the fin’s shape was not odd enough, it also featured denticles, tooth-like scales, on top of it! Its forehead also had these spikes on it.
Scientists believe this oddly shaped fin and scaly forehead might be visually important in order to attract a mate, and it is believed that only males possess this feature!
However, scientists still do not agree about exactly what the fin was used for.
Xenacanthus
Xenacanthus is a type of prehistoric shark believed to have been able to live in freshwater sources. Its body shape is very eel-like, with a dorsal fin running the entire length of its body. What sets Xenacanthus apart from other prehistoric sharks is the spine located on the back of its head.
Scientists believe this spine served as protection against large predators. Some researchers even hypothesize the spine could be poisonous, similar to a modern-day sting ray’s spine.
Edestus
This prehistoric shark is also known as the “scissor-toothed shark,” so obviously, its unique feature must deal with its teeth. Modern-day sharks lose and grow back teeth continuously, but this was not the case with Edestus. In fact, this shark did not lose its worn teeth at all but still grew new teeth. The result of this was a bizarre set of teeth with the old teeth pushed forward out of the mouth!
This shark looked like it had multiple sets of sharp scissor teeth. Scientists are not sure exactly what type of prey Edestus ate or even exactly how the sharp teeth were used.
Resources
https://sharkopedia.discovery.com/shark-topics/prehistoric-sharks
https://sciencing.com/megalodon-kids-5038897.html
https://www.dkfindout.com/us/dinosaurs-and-prehistoric-life/prehistoric-fish/strange-shaped-fish/
