How to Read a Fossil Shark Tooth: Megalodon, Otodus and the Megatooth Family

Fossil megalodon tooth from Florida

By Adam Kelliher

People pick up a megalodon tooth at the counter and the first question is always the same: how big was the shark? Fair question. The honest answer is that the tooth is nearly all we have, so the tooth has to do the talking.

Why it's always teeth

Shark skeletons are cartilage, and cartilage rots fast. Tooth enamel doesn't. The Florida Museum's researchers put it plainly: megalodon is known from fossil teeth and a few rare vertebrae, and a shark sheds thousands of teeth over its life. That's why you can hold one and almost never see a skeleton.[2]

Fossil megalodon tooth from Florida
Megalodon tooth from Florida. Broad, flat blade with fine even serrations and no side cusplets. (photo: Rubble Rock & Gem)

Three things to look at

  1. Serrations. Megalodon teeth are uniformly serrated, like a steak knife.[1]
  2. Side cusplets. The little mini-teeth beside the main blade. Megalodon's early ancestor Otodus obliquus, about 60 million years ago, had big triangular cusplets, no serrations and a heavy root. Megalodon lost the cusplets.[1][3]
  3. Shape. The old three-pronged teeth worked like a fork for grabbing fast fish. The later broad blades were built for cutting big, fleshy prey like whales and dolphins.[1]

That change took a long time. The Florida Museum work traced the last step, from Carcharocles chubutensis to megalodon, over about 12 million years.[1] So if you line up an Otodus tooth from Khouribga, Morocco next to a megalodon tooth from Florida, you're looking at two ends of a very long story.

So how big was it?

Megalodon teeth can top 7 inches. Newer equations based on tooth width, not height, put the biggest sharks at up to about 65 feet, with a margin of error of around 10 feet for the largest ones. The researchers themselves say the question isn't settled without a skeleton.[2] I'd take any exact number on a sales tag with a grain of salt.

Not the great white's granddad

For a long time megalodon was treated as the great white's ancestor because the teeth look alike. Current thinking at the Florida Museum is that they're cousins that last shared an ancestor about 60 million years ago.[2][4] We also carry smaller fossil mako teeth from Florida if you want a second lineage for comparison.

Megalodon ruled the oceans from roughly 23 to 3.6 million years ago.[2] Come see the trays in the shop, or browse the fossil collection.

See what's new: browse our newest arrivals for the latest pieces added to the shop.

Sources

  1. Florida Museum. How megalodon's teeth evolved into the 'ultimate cutting tools'.
  2. Florida Museum. School lesson gone wrong leads to new, bigger megalodon size estimate.
  3. Florida Museum FOSSIL Project. Megalodon evolution along the Calvert Cliffs.
  4. Florida Museum. Megalodon Shark, 100 Years.

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