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An artist’s conception Jurassic ammonites

I have always been fascinated by cephalopods. One of my favorite parts of natural history museums is seeing the reconstructions of ancient oceans where the big gray spirals are re-imagined with the colors and textures (and tentacles) of real life. Those stunning reconstructions and thrilling artworks are based on the appearance and anatomy of modern cephalopods…and pretty much nothing else. The soft tissue of orthocones, ammonites, and belemnites is not preserved in the fossil record. Invertebrate paleontologists (and artists) have been forced to flesh in those fabulous shells with information gleaned from octopuses squids, and nautiluses.

Until now! Scientists looking at limestone “pages” from the the extraordinary Solnhofen-Eichstätt deposits southern Germany were perplexed by a weird ancient blob (above). I hope you will take a moment to look at these seemingly meaningless pink and yellow smudges and smears. Such an examination provides testament to the gifts of paleontologist Christian Klug of the University of Zurich who was able to decipher what this truly is: the body of a 150 million year old ammonite somehow removed from its shell and preserved in an anoxic lagoon.

Through Klug’s reconstructive prowess we are able to gift the anatomy of this ancient creature. Ammonoids were common in Earth’s oceans from the Ordovician until the end of the Cretaceous (a 400 million year run) and they are invaluable to geologists as index fossils, but, in some ways we don’t know much about them. Although this fossil helps us to understand their anatomy, it also engenders new questions. For example, how did this particular mollusk die? It is possible it was ripped from its shell by some Jurassic monster which then lost hold of the morsel. After watching the decaying creatures drifting in the tides of the Chesapeake, however, I am more inclined to think that the interstitial tissues which held the ammonite in its shell decayed and the dead animal slid out. This hypothesis is somewhat supported by what is still missing from this extraordinary find: the arms! Ammonite scientists would dearly love to know about the arms of these creatures. Were they numerous and weak like the arms of nautiluses? Were they long and strong like the grabbing arms of cuttlefish? Did ammonites have different sorts of arms for different purposes? (based on modern cephalopods, this would be my guess). We still don’t know, but the very existence of this fossil shows that with luck, infinite patience, and Professor Klug’s sharp eyes, it is possible to discover things lost for hundreds of millions of years. Maybe there are other finds waiting out there in the ancient rock!

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