We have a four year old, so our household is experiencing an uptick in dinosaur-literacy. One day in the course of googling at said four year old’s request, I made a fascinating discovery:
Only three fossil sturgeon skeletons have ever been found.
All three were lodged inside the belly of a hadrosaur (duck-billed dinosaur).
What gives? Weren’t hadrosaurs vegetarian?
Interestingly enough, the sturgeon fossils were preserved whole and fully articulated– they hadn’t been chewed or mangled up in the dinosaur’s gizzard.
As far as anybody can tell, what happened is occasionally a hadrosaur was tooling around doing its hadrosaur thing and suddenly dropped dead (disease, starvation, getting eaten by T. rex, etc). Since hadrosaurs were semi-aquatic, whenever they died it was likely to be in or near water. So their carcass would bob along until it hit a quiet muddy bank area and ripen as carcasses do. Apparently Cretaceous sturgeon were either scavengers or enjoyed the flavor of other scavengers like worms and crabs; either way, they’d snuggle up inside the hadrosaur corpse for a buffet, get stuck, and fossilize along with their real estate.
Sturgeon don’t have a lot of bones– they’re technically in the bony fish family, but they apparently decided millions of years ago that bones are for suckers and dropped them. (They don’t even have a vertebrae! Just a nekkid cartilaginous notochord around the spinal cord– as I discovered one day whilst watching this fish-cleaning tutorial.) The only hard tissues left are a few bones making up the skull and the scutes on their skin. The rest of the fish is gooey enough that the body falls apart quickly and the hard parts scatter. That might explain why so many of the fossils we’ve found came from inside a hadrosaur corpse– it made a nice quiet nook where the sturgeon remains were protected from being knocked apart by waves or scavengers.
Interestingly, I did once see a warning to would-be sturgeon farmers to always keep ponds and tanks open and clear of debris. Apparently they don’t go backwards very well; if there’s a lot of junk on the bottom they get stuck. With so little morphological change over the last 70+ million years, it stands to reason that ancient sturgeon didn’t have much of a reverse gear either.
Moral of the story: next time you’re tempted to curl up inside a stinky dinosaur corpse, make sure you have an escape route.
Until next time…..