The Tully Monster Mystery Will Never Be Solved | Deserter

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For a creature harangued with accusations of being “problematic” and a “freak,” Tully’s monster was actually quite delightful. His body was long and soft like an overripe cucumber, tapering to a spade-shaped tail fin at its rear. On the front of the creature, where one might expect a head, its body instead tapers into an appendage not unlike an elephant’s trunk and ends in a serrated, grasping pincer. And as a puzzling final decoration, a pair of eyes at either end of the horizontal stem sit above the creature like a strange oar.

This 300-million-year-old creature has been mysterious ever since it was discovered decades ago. It’s an animal with no obvious ancestors or descendants, an organism seemingly out of place in any place or time or, well, situation. It’s the kind of fossil that makes me wonder if, one day, it might be debunked as a hoax; the creature’s neck-like snout convinced even a Loch Ness sincere that Tully was Nessie’s ancient ancestor.

For decades, scientists have been trying to fit the monster Tully into the tree of life. People have, on various occasions, suggested that the creature was a worm, or maybe a lobster, or some kind of snail, or maybe a fish? Different scientists have alternated between calling the creature a vertebrate or an invertebrate, and each new theory inevitably leads to triumphant headlines declaring that, finally, the mystery of the Tully monster had been “solved.” The latest of these headlines arrived this week, accompanying a new article published in the magazine Paleontology which aims to swing the vertebrate-invertebrate pendulum back in favor of the spineless.

Was this what Tully’s monster looked like? Credit: Nobu Tamura/Wikimedia Commons, CC BY-SA

Over the years, I have followed the mystery of the Tully monster and other “problematic” fossils as they have apparently been solved. Just last year, the mystery of the “alien goldfish”, the mystery of the “skeletal tubes”, and the mystery of the “half a billion year old creature without anus” was solved. With so many of these stories circulating, it’s easy to lose sight of what, exactly, is being “solved” here. The obvious and most common answer is taxonomy, where each of these creatures can be classified on the sprawling tree of life. The alien goldfish was a mollusk; the skeleton tubes belonged to an ancient medusa who made tubes; and the creature without anus was an ancestor of spiders and insects. This question of classification forms the titular mystery of Tully’s monster: what kind of animal was it?

The Tully monster roamed the tropical coastal waters of what is now Illinois, along with more legible relatives of modern day shrimp, jellyfish, sharks and sea cucumbers. The species was discovered in 1958 when Francis Tully, a retired pipe fitter and amateur paleontologist, found an iron lump that had broken in two. Nodules are common in Mazon Creek, where millions of years ago they hardened through chemical reactions around dead animals and plants and were later discarded by coal miners in fossil-laden piles. This particular cracked ironstone held the impression of a blimp-like creature that Tully had never seen before. He took his discovery to the Field Museum, where it baffled even paleontologists; he was soon nicknamed the Tully monster. In 1966, Eugene Richardson, curator of the fossil invertebrate museum, described the fossil in Science and nicknamed him Tullimonstrum gregarioussimply latinizing his nickname.

This is pretty much what Tully’s monster looks like. Source: Ghedoghedo/Wikimedia, CC BY-SA

Years of collecting have unearthed thousands of Tully monsters, ranging in size from a few inches to nearly a foot in length. The creature became the state fossil of Illinois, as well as the face of many U-Haul trucks. As the fame of the Tully monster has grown, so have attempts to classify it. In his 1966 description of the fossil, Richardson went little further than “worm-like”. In 1979, a geologist suggested it was an “aberrant member” of molluscs, perhaps something like a sea slug. About a decade later, a new analysis has suggested that the Tully monster’s closest relatives were sea slugs or extinct, oddly toothed creatures called conodonts. Somewhere along the way, another paleontologist concluded that the fossil must have been one of two unrelated types of worm.

All these identifications seemed plausible, but somehow impossible to prove. The ironstones of Mazon Creek have preserved beautiful silhouettes of even the most diaphanous creatures, but no organic matter from the animal itself. But in 2016, two unrelated articles, coincidentally, both appeared in the magazine Nature, came out with new lines of evidence suggesting that the Tully monster was a vertebrate. A team of researchers discovered microscopic pigments in the eyes of Tully fossils, examined them with a scanning electron microscope and found a carpet of pigment granules in the shape of a “meatball” and “sausage” a unique feature of vertebrates. The other team reexamined a white streak running down the center of the Tully monster’s body that had previously been interpreted as the weird creature’s gut tube, considering that the other fossils found at Mazon Creek had black gut tubes and some fossils of Tully’s monsters had a black line in addition to a white one. Then the researchers identified the white line as a notochord, a flexible rod found only in vertebrates.

Was this what Tully’s monster looked like? Credit: Entelognathus/Wikimedia, CC BY-SA

The latter group suggested that the Tully monster’s closest living relative was a lamprey, the noodle-like fish with nightmarish concentric rings of teeth. Notoriety cardsThe New York Times, The Atlantic, AND American scientisthe declared the Tully mystery finally solved, and people flocked to the streets to bang celebratory pots and pans and play celebratory vuvuzelas.

But nothing about 300 million years ago has ever been truly established, and a year later a group of half-hearted paleontologists fired back in an article in Paleontology partly titled “Tully’s Monster Isn’t a Vertebrate”. He dismissed the claims in both previous papers, noting that lampreys have been found in Mazon Creek that look nothing like the Tully monster and citing the many beautifully complex eyes of the invertebrate kingdom—just consider the octopus! “If you’re going to make extraordinary claims, you need extraordinary evidence,” Lauren Sallan, a paleobiologist at the University of Pennsylvania and author of the Paleontology paper, he said in a press release.

Over the next few years, the papers kept coming. A 2019 analysis of Tully’s monster eyes in the diary Proceedings of the Royal Society B has thrown a hat in the ring of invertebrates and a 2020 soft tissue analysis Geobiology he threw a coin into the vertebrate fountain. And now a document from 2023 that creates a 3D model of the monster Tully in Paleontology he joined the ranks of would-be mystery solvers, claiming the creature was an invertebrate due to segmentation in its head region.

Was this what Tully’s monster looked like? Credit: /Wikimedia Commons, CC BY-SA

Opening of the beloved musical The Fiddler on the Roof, the inhabitants of the Russian shtetl village of Anatevka sing a song about their traditions, aptly named “Tradition”. The song reaches an iconic climax as the villagers, divided over the identity of a recently sold ungulate at market, begin shouting “Horse! Mule! Horse! Mule!” before returning to sing the tradition together once again. That’s how I feel every time it’s breathlessly announced that the mystery of the Tully monster has been solved yet again. The headlines read like fact, as if the debate has actually been resolved. The Tully Monster didn’t have a backbone after all! The Tully Monster’s eyes prove it’s a vertebrate! The True Nature of the Tully Monster Revealed! Of course I want more endless documents on this unusual creature. Researching Tully’s monster’s true role in the history of life on Earth is an important question, one that could ultimately actually be answered with new tools, new fossils, or even new researchers. This is the great tradition of science: getting ever closer to our best approximation of the truth.

But as I see it, taxonomy isn’t the only, or even the most interesting, issue at play here. Knowing whether or not the Tully monster had a notochord is not solve the mysteries of a truly bizarre creature that once swarmed Chicago’s sunken canyons as Cubs fans did in 2016 (a huge year for Illinois creatures, past and present). I could spend hours speculating about how the creature’s dumbbell-shaped eyes may have been scanning the tropical waters for prey, what colors adorned its soft and perhaps slimy body, and most importantly, all the ways it used the its mouth-snout curved for food, certainly, but any elongated snout raises a number of evolutionary questions. The existence of a living thing is about much more than who its relatives are. And the closer we get to the truth, the more the unfathomable time gap comes to mind.

Anyway, see you next year when the mystery of the Tully monster is solved once again, and BYOV (bring your vuvuzela)!

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