This is my first test post on the site. :3 🤯

For more than half a century, the Tully monster (Tullimonstrum gregarium), an enigmatic animal that lived about 300 million years ago, has confounded paleontologists, with its strange anatomy making it difficult to classify. Recently, a group of researchers proposed a hypothesis that Tullimonstrum was a vertebrate similar to cyclostomes (jawless fish like lamprey and hagfish). If it was, then the Tully monster would potentially fill a gap in the evolutionary history of early vertebrates. Studies so far have both supported and rejected this hypothesis. Now, using 3D imaging technology, a team in Japan believes it has found the answer after uncovering detailed characteristics of the Tully monster which strongly suggest that it was not a vertebrate. However, its exact classification and what type of invertebrate it was is still to be decided.

Science Daily

Reconstruction of the Tully Monster from The Field Museum in Chicago:
Tullymonstrum