An article published in the journal “Nature” describes a study that provides a solution to the mystery represented by the animal commonly known as “Tully” monster” (photo ©Ghedoghedo). Its scientific name is Tullimonstrum gregarium and it’s a creature that lived just over 300 million years ago in today’s Illinois, USA. For decades no one could figure out what kind of animal it was but according to a team from Yale University led by Dr. Victoria McCoy of the University of Leicester it was a vertebrate related to modern lampreys.

The Tully monster was discovered in 1958 and both its scientific name and its nickname were given after Francis Tully, an amateur fossil hunter who discovered its first specimen in the pits of a coal mine. Since then in that area of Illinois thousands of Tully monsters were found making it famous, so much that the strange creature became a symbol of that state.

The problem from the beginning was that the Tully monster’s strange look baffled paleontologists, who failed to interpret its relation with other known species. In the Paleozoic era in which it this species lived there were organisms very different from today’s ones, so much as that sometimes they even formed separate phyla today extinct.

In some cases, the difficulty is the shortage of fossils, sometimes incomplete. In the Tully monster’s case it was just the animal’s look that made it its classification difficult so that over time a number of hypotheses were proposed but none supported by convincing evidence. Tullimonstrum gregarium could reach a length of about 30 cm (one foot), it had a tubular shape and teeth at the end of a sort of trunk and eyes on both sides of a kind of long and rigid bar above the central part of its body.

Dr. Victoria McCoy’s team used modern technologies that were unthinkable until not many years ago who that recently started being used in the field of paleontology as well. For example, a synchrotron elemental mapping technique was used: it exploits an X-ray beam to produce a map of an object’s chemical composition to examine it in a non-destructive way.

Techniques of this type allowed to examine much more in-depth the 2000 Tully monsters in the Field Museum of Natural History’s collection. The result is that the researchers discovered various morphological features of these animals that couldn’t be seen before. In particular, they managed to examine and map the inside of their bodies.

These analyzes identified gills and a rudimentary spinal cord. Those are some of the anatomical elements that convinced the researchers that the Tully monster was a vertebrate related to modern lampreys. It was very different from its modern relatives and it’s difficult to understand how it lived although its eyes and teeth suggest that it was a predator.

There are many fossils of Tullimonstrum gregarium but limited to a short period so we don’t know when it appeared nor when it got extinct. There are still many questions about the Tully monster but this research provided at least some answers concerning its nature and its relation with modern animals.