Shark week 4: megalodon tooth colonized by boring clams

Alert readers probably noticed that I titled the first post in this series “Matt’s first megalodon tooth“, implying that there would be other megalodon teeth to follow. Here’s my second one.

At first glance, this is a pretty jacked-up megalodon tooth. It is pocked with circular and ovoid craters, and has a big fat hole drilled right through it. Hardly collector grade! And in fact that’s what first caught my attention about this tooth — it’s a 6-incher that was being offered for an enticingly low price. But I got even more excited when I clicked past the thumbnail image on the sale site and saw precisely how this tooth was damaged. This is not random, senseless taphonomic battery (ahem); this tooth was colonized by a bunch of boring clams.

Like Adam Savage — and, I suspect, most collectors-of-things — I am fascinated by objects and the stories that they tell. And this tooth tells several stories. First, it’s a huge tooth from a huge shark, a truly vast, multi-ton animal heavier than a T. rex and longer than my house. Second, it’s a fossil that’s millions of years old, evidence of an extinct species from a vanished ecology, one where gigantic sharks and macroraptorial sperm whales hunted small baleen whales, early seals and sea lions, and manatees and sea cows. And third, it’s a relic of another, entirely different ecology, one in which this shed tooth sank to the sea floor and was colonized by a host of smaller organisms, including most obviously hole-boring clams. In effect, this one tooth was a miniature reef, supporting multiple species of invertebrates. The traces left by those invertebrates are themselves ichnofossils, so this tooth is a body fossil with ichnofossils dug out of it. It’s turtles all the way down!

Can we figure out what any of those invertebrates were? Just a few years ago that would have been a challenging task for a non-specialist, but fortunately in 2019 Harry Maisch and colleagues published a really cool paper, “Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay, North Carolina, USA: implications for processes of lag deposit formation”. That paper is very well illustrated, and the figures basically serve as a field guide for anyone who wants to identify similar traces in rocks or teeth of equivalent age. I will take up that sword in a future post.

Incidentally, this is now the biggest tooth in my little collection, just slightly — but noticeably — bigger than my first megalodon tooth: 157mm on the long side, vs 155mm, and 112mm max root width, vs 107mm.

Bonus goofy observation: I strongly suspect that no other megalodon tooth in the world beats this one in simulating a Star Trek phaser.

Reference

Maisch IV, H.M., Becker, M.A. and Chamberlain Jr, J.A. 2020. Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay, North Carolina, USA: implications for processes of lag deposit formation. Ichnos 27(2): 122-141.