Posts Tagged geologic time

In Consideration of Bitemarks

This guy is holding up a set of Great White shark jaws inside a Megalodon jaw.

So, lately I’ve been thinking about teeth. Dentition is interesting. Choppers can be used to determine diet, infer foraging or hunting behavior, and indicate something about the biotic zones necessary for a species’ survival. All of which is interesting but not really important for our purposes today. Say hello to Mr. Shark.

This aged fellow has been cruising around Earth’s oceans since the Ordovician Period, some 400 million years ago. That’s a lot water under the bridge. Back then tetrapods hadn’t even burst out of the ocean yet, so it’s not surprising that sharks from this time period don’t leave lasting impressions. Even their teeth were dull.

For a good long time sharks just kept a low profile and swaggered around the ocean eating pretty much anything they could grab. Then about 100 million years ago, smack in the middle of the Cretaceous Period, the ancestors of today’s sharks bloomed into the teeth-gnashing monsters we know and love. Even the occasional dinosaur graced the lunch menu if they blundered deep enough in the water.

After a while, along came Megalodon, boasting seven-inch incisors. This guy would have made fearsome land dinosaurs hesitate to dip a toe in the big blue. Of course by then, the dinosaurs were gone and Megalodon and his buddies took advantage and became the world’s largest known shark, a true mega-predator. Tipping the scales between 50 and 100 tons, and reaching a length of seventy feet – Megs was a big old toothy beast.

Like other sharks, Megalodon shed teeth the way humans drop hairs and this helps us understand they once inhabited a global range until they disappeared during the Pleistocene about a million years ago. Minor fluctuations in habitat, climate, and food sources tip the balance for or against survival and after a run of more than 25 million years, Megalodon went extinct. Can’t say I’m sad about that, really. We’ve still got Megalodon’s descendents in the Great White shark and that’s toothy enough for me.

Prehistory is filled with amazing beasties – do you have a favorite? What do you think about Megalodon? Are you sad Megs no longer cruises the ocean, picking off a blue whale here or there? Just thinking how an occasional extinct species makes a sudden surprise reappearance gives a bonfire on the beach a higher safety rating than a week on a cruise ship.

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