'Tully monster' mystery is far from solved: experts

A bizarre prehistoric marine creature - popularly referred to as the 'Tully monster' - can not be classified as a verterbrate, contrary to the claims of some experts, a new study has found.
Last year, two groups of scientists claimed that the ancient animal - that had long defied classification - was in fact a vertebrate. Specifically, it seemed to be a type of fish called a lamprey.
However, according paleobiologists who undertook more analysis, this classification is wrong.
"This animal doesn't fit easy classification because it's so weird," said Lauren Sallan, an assistant professor at University of Pennsylvania in the US.

"It has these eyes that are on stalks and it has this pincer at the end of a long proboscis and there's even disagreement about which way is up. But the last thing that the Tully monster could be is a fish," said Sallan.
The mystery of the Tully monster, known to scientists as Tullimonstrum gregarium, remains.

"It's important to incorporate all lines of evidence when considering enigmatic fossils: anatomical, preservational and comparative," said Sam Giles, a junior research fellow at the University of Oxford.
"Applying that standard to the Tully monster argues strongly against a vertebrate identity," said Giles.

The Tully monster has been known since the 1950s, when the first fossils were found in Mazon Creek in Illinois.
Initially it was identified as a worm, Sallan said.
"There is a well-constructed argument that it is some kind of mollusc, like a sea cucumber. There is another very strong argument that it's some kind of arthropod, similar to a lobster," he said.
That is why it took the scientific community by surprise when in 2016 two studies came out in close succession both claiming they had firm evidence that the Tully monster was in fact a vertebrate, researchers said.