Prehistoric peepers provide vital clue in solving ancient Tully Monster mystery

A 300 million year-old fossil mystery has been solved by a team from the Department of Geology, which has identified that the ancient ‘Tully Monster’ was a vertebrate - due to the unique characteristics of its eyes.

Tullimonstrum gregarium or as it is more commonly known the ‘Tully Monster’, found only in coal quarries in Illinois, Northern America, is known to many Americans because its alien-like image can be seen on the sides of large U-haul™ trailers which ply the freeways.

Thomas Clements, a PhD student and lead author on the paper, explained: “When a fossil has anatomy this bizarre it’s difficult to know where to start, so we decided to look at the most striking feature - the stalked structures with dark blobs.”

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Thomas Clements and Professor Sarah Gabbott searching for the 'Tully Monster’ in Illinois, USA
In a new study published in Nature, the palaeontologists used Scanning Electron Microscopy to discover that the dark ‘blobs’ were actually made up of hundreds of thousands of microscopic dark granules, each 50 times smaller than the width of a human hair. The chemical composition of these granules was determined by using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and is identical to organelles found in cells called melanosomes; these being responsible for creating and storing the pigment melanin

Thomas added: “Nearly all animals can produce the pigment melanin. It’s what gives humans the range of skin and hair colours we see today. Melanin is also found in the eyes of many animal groups where it stops light from bouncing around inside the eyeball and allows the formation of a clear visual image.”

Identifying fossil melanosomes containing melanin and a lens is the first time it has been conclusively proved that Tullimonstrum had eyes on stalks. When the team looked closer at the melanosomes they made another exciting discovery.

Professor Sarah Gabbott from the Department of Geology added: “There were two distinct shapes of melanosomes in Tullimonstrum’s eyes: some look like microscopic ‘sausages’ and others like microscopic ‘meatballs’. This evidence was crucial because only vertebrates have two different shapes of melanosome, meaning that unlike previous researchers that thought that Tullimonstrum was an invertebrate (animal without a backbone), this is the first unequivocal evidence that Tullimonstrum is a member of the same group of animals as us, the vertebrates.”

Thomas Clements has been telling Nathan Ifill about the discovery.

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