A new research confirms that the Tully monster was a vertebrate

Fossils of Tullimonstrum gregarium, the Tully monster
Fossils of Tullimonstrum gregarium, the Tully monster

An article published in the journal “Nature” describes a research that confirms that the ancient animal commonly known as “Tully monster” (photo ©Ghedoghedo) was a vertebrate. Decades after the discovery of the first fossil of Tullimonstrum gregarium – this is its scientific name – and a number of hypotheses about its classification, this study is the second in a few weeks published in “Nature” to reach the same conclusions.

A team led by Dr. Victoria McCoy examined fossils of Tullimonstrum gregarium and in the article published in March 2016 they concluded that because of its anatomical features it was a vertebrate related to lampreys. Another team of paleontologists focused on the eyes of this animal that lived just over 300 million years ago in today’s Illinois, USA.

Using an electron microscope, the scientists discovered that some body structures of the Tully monster were formed by hundreds of thousands of dark granules. Each of these granules had a size 50 times less than the thickness of a human hair. That was the beginning of a series of in-depth analyzes that allowed to understand this animal’s nature.

The granules were examined using a technique called Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). It turned out that they have a shape and a chemical composition which proved to be identical to that found in the organelles of cells called melanosomes, which have the purpose to synthesize and accumulate melanin.

Almost all animals produce melanin, which in humans determines the color of skin and hair. In many animals, melanin prevents light from bouncing inside their eyeballs allowing the formation of a clear image. The identification of the fossil melanosomes containing melanin allowed to prove that Tullimonstrum gregarium had eyes on stalks.

The exam of the Tully monster’s eyes revealed two distinct shapes of melanosomes: some look like “sausages” while others have the shape of “meatballs”. It’s a deciding factor because only vertebrates have melanosomes in two different shapes. The melanin in the Tullimonstrum gregarium’s eyes is the oldest fossil pigment discovered so far.

As in the other research on the Tully monster, the answers came thanks to new technologies more and more used also in the field of paleontology. There are still many questions about this strange animal but after decades of puzzlement there are at least some reasonable certainties.

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