Tullimonstrum
genus of vertebrate from the Pennsylvanian geological period
Tullimonstrum, colloquially known as the Tully Monster, is an extinct bilaterian animal that lived in shallow tropical coastal waters of muddy estuaries during the Pennsylvanian geological period, about 300 million years ago. A single species, T. gregarium, is known. Its classification has been the subject of controversy, and interpretations of the fossil likened it to molluscs, arthropods, conodonts, worms, and vertebrates. It is unknown whether Tullimonstrum was a vertebrate or an invertebrate.
| Tullimonstrum Temporal range:
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| The Tully Monster Tullimonstrum gregarium fossil (part and counterpart) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Clade: | Bilateria |
| Genus: | †Tullimonstrum Richardson, 1966 |
| Type species | |
| Tullimonstrum gregarium Richardson, 1966
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