Sharks have been around for 450 million years, they are older than even dinosaurs. Throughout this long history, there have been a huge variety of species of sharks. Here is a list of five of the coolest prehistoric sharks that ever lived:

Megalodon

The Megalodon, named after its massive teeth that could grow to 7.1 inches in length, was the largest known shark species to ever live. Most of the megalodon shark facts we know come from studying their massive teeth. Megalodons are estimated to have grown anywhere between a massive 400 and 100 feet in length and weighed as much as 100 tons. Megalodon sharks lived 19.8 to 2.6 million years ago during the Cenozoic Era. These sharks are now extinct, but during their time they swam in every ocean across the globe.

Megalodon sharks were fearsome predators with a bite force of 10.8 to 18.2 tons per square inch. They have approximately 276 teeth in 5 rows that grew in their massive 6.6 foot wide mouths. As megalodons are cartilagens like all sharks, the only remaining fossils are their massive teeth. Their teeth were thick and serrated used to efficiently kill their prey. They are believed to have eaten everything from dolphins, sea turtles, smaller sharks, giant squids, and even the Leviathan, the largest and predatory sperm whale. Megalodons are cool because they are the stuff of our worst nightmares, massive apex predators that roamed the oceans.

Helicoprion

Helicoprion was a shark that lived during the Permian era around 290 million years ago. Though it went extinct around 250 million years ago, it was a survivor that lived through the Permian-Triassic mass extinction event. There are four known species of Helicoprion and they are estimated to have grown anywhere from 10 feet to 25 feet in length. Scientists also believe that Helicoprion had long, pointed noses. Helicoprions are believed to the be the antecedents of more ghost sharks

What makes Helicoprions so interesting is they have a massive tooth whorl on their lower jaw. This tooth whorl hinged on a joint and acted like a saw blade that spun to grind against its prey. These tooth whorls contained three rows of over a hundred teeth. The largest tooth whorl found was 6.7 inches in diameter. Helicoprion has no teeth on the upper jaw so it only use its tooth whorl to eat. Helicoprions are an interesting evolutionary species, since we know of no modern species that uses a tooth whorl to kill prey.

Stethacanthus

Stehacanthus is a really old species of shark. It is estimated to died out 350 million years ago and lived through the Late Devonian and Early Carboniferous eras. The Stethacanthus was a small shark, growing only about 2.3 feet in length. However this small shark had some pretty big physical features that made it a really unique species.

Stethacanthus is most recognized by its anvil shaped dorsal fin. Stethacanthus also had a spine brush complex, small spiked scales around its crest, a whip attached to its dorsal fin, and pelvic girdles. Though it is thought that stethacanthus was a slow moving, relatively unsuccessful predator, these unique physical traits make it a standout prehistoric species.

Xenacanthus

Xenacanthus lived around 202 million years ago during the Late Devonian period. Unlike modern sharks, Xenacanthus was a freshwater fish. Xenacanthus looks like a mix between an eel and shark. It measured about 3 feet in length and and weighed around 5-10 pounds. Xenacanthus had a ribbon-like dorsal fin that ran down the entire length of the back connecting with the anal fin. There are at least twenty known species of Xenacanthus.

Since they had an eel-like body it was believed the swam and hunted like modern eels. They had a distinctive spiky spine that ran up their heads and protected them from predators. Scientists also speculate that it also used poison to defend itself. Xenacanthus also had unusual v-shaped teeth that sat in a jaw made of bone. Unlike other prehistoric sharks, this unique jaw preserved easily and has let scientists learn a lot about this species. All the physical differences between Xenacanthus and modern sharks are what make it so fascinating.

Edestus

The Edestus is also known as the scissor tooth shark. It was named for its unusual teeth that grew in a single row along curved jawlines that were hinged and worked like a giant pair of serrated scissors. It is estimated the Edestus lived around 300 million years ago during the Late Carboniferous era. It was related the Helicoprion. There are five known species of Edestus, the largest being comparable to the modern great white shark in size.

Edestus were incredibly unusual as they did not shed their teeth like most sharks, but their teeth continuously grew. The construct of the jaw and the ever growing teeth have baffled scientists as these are inefficient evolutionary developments. The ever-growing teeth led them to protrude out of the jaw line making biting and chewing incredibly difficult. The shape of the jaw created probably made swimming require more energy and signaled prey of an oncoming attack. Though not much is really known about these creatures, this seemingly inefficient evolutionary development is what makes this species really interesting.

These are just some of the known prehistoric shark species that once roamed this earth. These unique species give you an idea of how diverse both prehistoric and modern sharks can be. Whether you are studying megalodon shark facts or learning about the habits of basking sharks, sharks are a fun and interesting species to learn about.