Science and archaeology may have come a long way, but many things about the Earth have remained a mystery in the 21st century. One of these mysteries is a strange-looking fossil known simply as the Tully monster.
The mystery of an unclassifiable fossil that was unearthed by amateur archaeologist Francis Tully in 1955 has remained unsolved - until now.
According to The Atlantic, a team of scientists at Yale University led by graduate student Victoria McCoy have uncovered the mystery to the strange-looking fossil, concluding that it is closely related to the modern lamprey (pictured below).
McCoy, whose favourite fossil while growing up had been the Tully Monster, had been fascinated by the mysterious creature, which is believed to have roamed the sea over 300 million years ago. As a result, she took on the project to solve the mystert of this tiny, unassignable creature (it measured about 10cm, according to a report by Ars Technica).
As an unsolved mystery, the Tully Monster nickname eventually became the fossil's Latin name: Tullimonstrum gregarium.
McCoy revealed that two critical discoveries led to their new conclusion. Firstly, most of the Tully Monster fossils had notochords, or flexible vertebrae - similar to humans.
Secondly, McCoy found that the Tully monster had "flaps on their sides that would have housed gills". This was initially hard to corroborate as "dead Tully Monsters typically landed on their fronts or backs - a position that obscured their gills as they turned to stone".
However, the team confirmed its findings after they found a few fossils that had been preserved in a way that allowed the gills to be visible.
The position of its eyes were found to be much like the hammerhead shark. This probably allowed the monster to see what it was eating with its mouth, which was a flexible, spade-like claw that extended out from its main body.
According to YaleNews, some key questions about Tully Monsters remain unanswered despite McCoy's research.
No one knows when the animal first appeared on Earth or when it went extinct, the university's public affairs department said on its website.
While ground-breaking, such discoveries makes us wonder what the Earth used to be like millions of years ago.