Are Sharks Related to Dinosaurs?

Were you aware that shark fossils date back 400 million years or more? When you plug in the often-cited fact that dinosaurs died out some 65 million years ago, you start to see just how tough, adaptable, and ancient the humble shark really is.

But are sharks directly related to dinosaurs? Are sharks one of the few surviving dinosaur family members, swimming and hiding in the ocean, safe from the catastrophic events that laid low their prehistoric ancestors?

While there are both similarities and connections between sharks and dinosaurs, it’s not right at all to say that sharks and dinosaurs are “related” in any meaningful biological sense. The first and most important thing to note is that no water-dwelling reptile or other aquatic species, no matter how ‘dinosaur-like’ in our minds, was never considered by experts to be a true dinosaur.

Qualities of a Dinosaur

According to the Natural History Museum in London, UK, there is a list of distinctive characteristics that defined what a ‘dinosaur’ was. As you can see, none of these can meaningfully compare to a shark.

1. Dinosaurs had an upright stance, with legs perpendicular to their body, unlike the ‘sprawl’ stance that is more common to reptiles in general.
2. Dinosaurs laid eggs — far fewer than half of all shark species lay eggs, where the others all give birth to live young.
3. Dinosaurs lived on land, not in the sea.
4. Dinosaur skulls have a hole between the eye socket and nostril, a feature shared commonly among many dinosaur species.
5. Dinosaur skills featured large, strong jaw muscles that attached to the top of the skull via two holds directly behind the eye socket.

Why People Think Sharks and Dinosaurs Were Related

What is it that’s behind the curiosity regarding sharks and dinosaurs, then? What is it about these creatures that makes people either assume that the two must be closely related, or even ask the question?

Fearsome Demeanor

The first and perhaps the most obvious parallel is the way that both predators are so fearsome and seemingly savage. While not all dinosaurs were predators, or even meat eaters, there certainly were a number of them who were apex predators in their time, much like the shark in the ocean we know today.

Both sharks and dinosaurs share the kind of fearsome characteristics that even history’s greatest predator and killer — humanity — is afraid to go back into the water from time to time…just as we’d be afraid to go back into the jungle if we knew dinosaurs could be lurking here and there.

Teeth, Teeth, and More Teeth

The next similarity that draws comparisons between the two is the seemingly endless rows of teeth. One physical characteristic that sharks and dinosaurs did share was their many rows of teeth that meant teeth were replaced quickly. A great white shark replaces all of its teeth every 230 days or so, and the Tyrannosaurus Rex replaced all of its teeth every 2-3 years.

It’s not just the dropping and replacing of teeth that draws this connection between dinosaurs and sharks, but also the fact that the teeth are a noticeable and fearsome feature of both creatures. When one thinks of either a dinosaur predator or a modern shark, they tend to focus on gaping mouths filled with razor-sharp teeth.

The “Meg” The Largest Shark ever?

About 45 million years after the dinosaurs disappeared, there emerged a new ocean predator called megalodon. At some 60 feet in length, 12 feet in height, and 60 tons in weight, the megalodon is one of the largest and fiercest predators to live anywhere on Earth, on the land or in the sea.

The megalodon met its end about 3.6 million years ago, however, when smaller, faster sharks like the Great White and others among the 500 or so species of shark we know today manage to compete in the environment far better.

As fearsome as the megalodon was — and surviving fossils of their jaws prove that — it was also slow, only managing a top speed of about 15-mph, where other sharks could swim twice as fast as that.

Its slow speed caused it to lose out on key food sources, and before long the megalodon died out. So what’s the connection to dinosaurs?

Once again, the megalodon was not technically a dinosaur, but the combination of huge size, ferocious rows of teeth, and status as an apex predator, not to mention the fact that it first lived tens of millions of years ago, all help people point to “the Meg” being some vestige of the dinosaur world.

Sharks lived before the Dinosaurs

This brings us to the final point, which is that dinosaurs and sharks do indeed share a long history. The oldest shark teeth fossils that have been found point to sharks living more than 400 million years ago.

That being so, it means that sharks are actually far older than dinosaurs, emerging during the late Ordovician Period, whereas dinosaurs only first emerged during the Triassic period between 200 and 250 million years ago.

There’s a tendency among people to assign almost anything that lived tens or hundreds of millions of years ago the “dinosaur” epithet, especially when it was also an apex predator armed with dozens of spearhead-like teeth.

We have other articles on animals that are related, or not to dinosaurs. We have put these in a list for ease of access below.

• Are Chickens dinosaurs?
• Are Alligators dinosaurs
• Are Turtles related to dinosaurs
• Are lizards related to dinosaurs
• Are crocodiles related to dinosaurs
• Is a rhinoceros a Dinosaur?

There’s Crossover, but No Direct Relation

So, what we can see is that there’s plenty of crossover between dinosaurs and sharks. They have lived during the same periods, sharks were (and are) fearsome predatory carnivores like so many dinosaurs were, and some variants of sharks — IE the megalodon — were the largest and most savage predators ever to stalk the Earth.

However, the most important thing to note here is that as a water-dwelling animal, a shark could never be called a dinosaur anyway, not even the megalodon. Dinosaur is a term that was used only to be applied to the land-dwelling creatures. What’s more, sharks are not reptiles, nor are they related to birds.

We’ve always talked about dinosaurs as being large reptiles, but deeper research has shown that many were more related to modern birds because of how they stood and behaved, and because fossils show that many dinosaurs were feathered, and not entirely scaled as movies show.

Conclusion

Sharks are part of the fish world, broadly speaking. In addition, the majority of them give birth to live young, which really makes them closer to mammals than birds or reptiles, both of which lay eggs.

Crossover and similarities we can see, but in all the ways that matter, dinosaurs and sharks are quite separate and different.

Sources

https://en.wikipedia.org/wiki/Megalodon

https://www.livescience.com/secret-to-sharks-success-evolution