If anxious people have nightmares of being naked in public, it is possible that a restless ammonite dreamed of swimming without a shell, his soft body exposed to the elements and the lingering eyes of predators.
For an unhappy late Jurassic Ammonite, this was not a dream, but a harsh reality. The animal died completely untouched, except for its volute shell, and was buried in this way. According to a recent study published in the Swiss Journal of Paleontology, the death of the ammonite made it an extraordinary fossil – one of the very few records of soft tissue in a creature that is most often immortalized as a shell..
“We know millions and millions of ammonites that have been kept in their shells, so something exceptional had to happen here,” said Thomas Clements, a paleobiologist at the University of Birmingham in England who was not involved in the research. “It’s like finding …” Dr. Clements said, watching. “Well, I don’t even know what it’s like to find it, it’s so weird.”
René Hoffmann, an ammonitologist at Ruhr Bochum University in Germany, who analyzed the study, called the fossil “a paleontological jackpot you only have once in your life.”
To the untrained eye, the fossil looks more like an impressionist painting than an ammonite: a pink, grain-shaped smear, surrounded by swelling, veins, and ovals. It was discovered in the Solnhofen-Eichstätt region of southern Germany, which was, in the days of the Ammonite, about 150 million years ago, an archipelago full of serene, oxygen-deprived lagoons. These conditions allowed soft and dead creatures to sink into the mud unharmed by predators or bacteria, according to Christian Klug, a paleontologist at the University of Zurich in Switzerland and the first author of the paper.
When Dr. Klug first saw the fossil, he knew it was the soft parts of an ammonite, but he didn’t know exactly which soft parts. He left her alone for months until Helmut Tischlinger, a fossil collector and author on paper, sent her photos of the fossil made with ultraviolet light, which revealed the tiny heights and mineral stains in the fossil.
Dr. Klug sequentially reconstructed the anatomy of the creature, from the most visible to the most obscure organs. First, he identified aptychus, a lower jaw that indicated the fossil was an ammonite. Behind the jaws, he found the chitinous layer of the esophagus and then a piece that suggested a digestive tract with cololitis – fecal matter (he used a different word) “that is still in the gut,” Dr. Klug clarified.
“For the most part, soft body reconstruction makes perfect sense,” said Margaret Yacobucci, a paleobiologist at Bowling Green State University in Ohio who was not involved in the research.
Solving the other mystery of the fossil – how the ammonite came to be separated from the shell – was much more difficult. The soft parts were so intact that they still seemed to be wrapped. The authors propose several alternative endings of the life of the ammonite, each possible but uncertain. One suggests that the soft parts of a dead ammonite slipped when the tissue that connects its body to the conch began to decompose.
Another more elaborate explanation is imagining a predator breaking the bark of the ammonite in the back and sucking its body just to throw the empty ammonite. “The best explanation is that a squid-like organism removed the soft parts and was unable to recover it,” said Dr. Klug.
Dr. Clements considers the powerless theory of predators to be “great,” if unlikely; it is assumed that an ammonium body that could be affected would show more visible damage. But it doesn’t have a good alternative. The interpretation of a fossil always raises a degree of doubt, and Dr. Clements predicts that unarmed ammonium will be re-analyzed in the future with robust chemical analysis.
Curiously, the fossilized ammonite is missing its arms, leaving unresolved one of the remarkable mysteries of the anatomy of ammonite. “Did they have many thin and delicate arms, like modern nautilizations, or a few strong arms, like modern colloids?” Dr. Yacobucci asked. “If I had access to a time machine, the first thing I would do is go back to Jurassic to see what kind of weapons the amonoids had.”
If a squid-like predator actually released ammonite from its shell, it may have eaten the creature’s unknown amount of weapons as a consolation prize, feeding both ancient cephalopods and the scientists who study them.
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