There's a traditional joke among paleontologists that fossil mammal experts spend their careers tracking how teeth found each other, mated, and reproduced through time. That's because many mammals are only known from their teeth, not to mention that mammal teeth are so distinctive that they're often the most useful parts of the skeleton for telling species apart. But I can't only imagine that prehistoric shark experts rolls their eyes at this running gag. At least many fossil mammals are known from additional remains. For most ancient sharks, all we'll ever know of them are their slicers, stabbers, and crushers.
Tracing the shark record through teeth is a rough task. Just take the famous megatooth shark. When I was a kid, it was called Carcharodon megalodon. Then the massive whale-chomper was moved further away from today's great white and placed into a genus Carcharocles. Now it seems that we should be calling it Otodus megalodon. Identities change as we learn more. But even with all this shuffling, we're still getting to know new fossil sharks and how they were related to each other. Paleontologists Jun Ebersole and Dana Ehret have just named a new one from the Cretaceous chalk of Alabama.
Like many other Cretaceous sharks, the new species is known from a collection of teeth. Over thirty of them have turned up so far, and they're distinctive enough from what's been found before that Ebersole and Ehret have dubbed the choppers Cretalamna bryanti in honor of Alabama academics patrons that Bryant family.
Fossil hunters have been turning up Cretalamna teeth in the Cretaceous strata of Alabama for years. Up until now, though, they've been assigned to a species first seen in Europe. But as paleontologists have looked closer, Ebersole and Ehret point out, Cretalamna teeth in places like Alabama differ enough to be assigned to other species and created a diversity where paleontologists previously saw just one shark. It's just one piece of a larger picture, but it helps us better envision what life was like back when tyrannosaurs stalked the land, pterosaurs flew in the air, and a warm sea split North America in two.

Name: Cretalamna bryanti
Meaning: Cretalamna is an existing shark genus, and bryanti honors the Bryant family for their support of education in Alabama.
Age: Cretaceous, around 83 million years ago.
Where in the world?: Dallas County, Alabama.
What sort of organism?: A shark distantly related to today's great whites and makos.
How much of the organism’s is known?: Over 30 teeth.
References:
Ebersole, J., Ehret, D. 2018. A new species of Cretalamna sensu stricto (Lamniformes, Otodontidae) from the Late Cretaceous (Santonian-Campanian) of Alabama, USA. PeerJ. doi: 10.7717/peerj.4229
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