I can only imagine the patience required of fossil octopus experts.

Octopus are squishy. Their principal hard parts are their beaks and, in some deep sea species, an internal shell that anchors swimming fins. But that’s just about all. At least with ancient sharks, the fish were constantly dropping teeth into the fossil record even when their cartilaginous skeletons were more likely to rot away. Ancient octopus had a limited number of hard parts per individual, held in mostly soft bodies that readily decayed away. They are not easy to find. Which is why Pohlsepia mazonensis was such a stunning discovery.

You’ve probably heard of the famous Mazon Creek fossil beds of 300 million years ago because of that lovely enigma, the Tully monster. But even those beautiful fossils undersell how spectacular the Mazon Creek layers are. Fresher and saltier bodies of water alternated back and forth during the Carboniferous, supporting different faunas including everything from sharks to spiders. Conditions were so right that even soft-bodied animals that normally rot to nothing were encapsulated in fine detail within rocky concretions. Pohlsepia was found in such a lump, as described in 2000, what seemed to be the world’s oldest octopus.