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Is it an invertebrate? Is it a vertebrate? It's the Tully monster!\n\nFurther reading:\n3D Tully monster probably not related to vertebrates\nHas the "Tully monster" mystery finally been solved after 65 years?\n\nPossibly what the Tully monster looked like while alive:\n\n\n\nShow transcript:\nWelcome to Strange Animals Podcast. I\u2019m your host, Kate Shaw.\nThis week we\u2019re going to learn about an ancient creature surrounded by mystery. When I was working on last week\u2019s updates episode, I found some new information about it and intended to include it as an update. Then I realized I was referencing a Patreon episode, which I also reworked into a chapter of the Beyond Bigfoot & Nessie book. So instead, I included the new information in this episode all about the Tully monster.\nIn 1955, an amateur fossil collector named Francis Tully discovered a really weird fossil. This was in one particular area of Illinois in the United States, roughly in the middle of North America. The fossil was about six inches long, or 15 cm, and Tully thought it resembled a tiny torpedo.\nHe took the fossil to the Field Museum of Natural History in Chicago in hopes that somebody could tell him what his fossil was. The paleontologists he showed it to had no idea what it was or even what it might be related to. It was described in 1966 and given the name Tullimonstrum, which means Mr. Tully\u2019s monster, which is pretty much what everyone was calling it already.\n300 million years ago, in what is now the state of Illinois, a strange animal lived in the shallow sea that covered part of the area. The land that bordered this sea was swampy, with many rivers emptying into the ocean. These river waters carried dead plant materials and mud, which settled to the bottom of the ocean. When an animal died, assuming it wasn\u2019t eaten by something else, its body sank into this soft muddy mess. The bacteria in the mud produced carbon dioxide that combined with iron that was also present in the mud, which formed a mineral called siderite that encased the dead animal. This slowed decay long enough that an impression of the body formed in the mud, and as the centuries passed and the mud became stone, the fossilized body impression was surrounded by a protective ironstone nodule. That\u2019s why we know about the soft-bodied animals from this area, even though soft-bodied animals rarely leave fossil evidence.\nSo what did this weird animal look like?\nThe Tully monster was shaped sort of like a slug or a leech, and it had a segmented body. Its eyes were on stalks that jutted out sideways, although the stalks were more of a horizontal bar that grew across the top of the head. The tail end had two vertical fins, which argues that the Tully monster was probably a good swimmer. But at the front of its body it had a long, thin, jointed proboscis that ended in claws or pincers lined with eight tiny tooth-like structures.\nIt\u2019s easy to assume that the pincers acted as jaws and therefore the proboscis was a mouth on a jointed stalk, but we really don\u2019t know. The Tully monster may have used its proboscis to probe for food in the mud at the bottom of the sea, but because the proboscis had a joint, it probably couldn\u2019t act as a sort of straw. The pincers may have grabbed tiny prey and conveyed it to a mouth that hasn\u2019t been preserved on the specimens we have.\nThe Tully monster resembles nothing else known, and is so bizarre that researchers aren\u2019t sure where to place it taxonomically. And it wasn\u2019t rare. Paleontologists have since found lots of Tully monster fossils in the Illinois fossil beds, known as the Mazon Creek formation. The Mazon Creek formation is also the source of highly detailed fossils of hundreds of other plant and animal species, including some that have never been found anywhere else.\nScientists have suggested any number of animal groups that the Tully monster might belong to. It might be a type of arthropod, a mollusk, a segmented worm\u2026or it might be a vertebrate.