It’s an Alga, It’s a Squid. No, It’s a Fish!

Apr 23, 2018

The Platylithophycus cretaceus specimen.
Credit Mike Eklund / American Museum of Natural History


A fossil found in Kansas seventy years ago has been identified as a large cartilaginous fish, like a shark or a ray. That wouldn’t be so noteworthy if the same fossil hadn’t already been identified, twice – first as a green alga, and then as a squid or cuttlefish.


This isn’t the first – nor, in all likelihood, the last – time that a fossil has been misidentified. Allison Bronson, the graduate student at the American Museum of Natural History who made the latest re-identification, quickly rattles off other examples: a fossil that was thought to be a sponge but was actually a land plant, or would-be fungi that turned out to be lungfish teeth. 

Bronson points the finger, not at improving technology, but at paleontologists stuck in their own bubbles of expertise.


“It’s easy to have blinders on,” Bronson said. “If you only have a hammer, every problem tends to look like a nail.”


In this case, three different sets of scientists looked at the same hexagonal texture in the same fossil and saw three different things. Algae experts saw algae, but with some extra protrusions they couldn’t quite explain.

Cephalopod experts saw a cuttlefish bone. And Bronson sees cartilage.

Bronson admits she’s not immune to the hammer-nail effect, noting with some humor that her studies of fossilized shark heads are “pretty niche.” But she and her colleagues used high-tech imaging techniques and did some extra chemical tests to see if their identification would hold up. It did.

Bronson says they are pretty confident they’ve gotten the right answer this time, but doesn’t rule out the possibility of revisions.

“I sure would be disappointed,” Bronson laughed.