Mystery surrounds the bizarre 'Tully Monster'

An unusual ancient animal called a Tully monster had been classified as a type of fish after decades of uncertainty.

However, new research led by paleobiologists at the University of Pennsylvania has found that the two previous studies which concluded the vertebrate structure "face significant challenges from biological, functional and taphonomic perspectives."

Lauren Sallan, one of the authors of the recent paper, said in a news release, "This animal doesn't fit easy classification because it's so weird. 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."

Last year, that is what other scientists had determined based on an examination of more than a thousand of the species' fossils; in fact, they identified it as a vertebrate with a spinal cord-like structure and ultimately linked it to a lamprey fish.

But the new study points out that previous evidence involving the eyes and ears may not necessarily mean the Tully monster is a vertebrate after all.

Although the team has not proposed an alternate classification, they argue that the creature should no longer be considered a vertebrate which could cause confusion within evolutionary timelines.