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Conodonts are enigmatic ancient animals that existed for 300 million years before going extinct shortly after the appearance of the first dinosaurs. Compared to larger and more dramatic fossils, these tiny eel-like organisms do not grab much public attention. However, despite their abundance across the world, they remain mysterious, capturing the imagination of paleontologists for more than a century.

In a in the journalÌýPaleobiology, an international team of paleontologists sought to shed light on the long-standing question of conodont food choices by analyzing the chemical composition of the tooth-like fossils of multiple species. The research was led by Dr. David Terrill, then-PhD student in the , who travelled to Germany to collaborate on developing this new approach.

Conodonts left behind tooth-like fossils found in large abundance in marine rocks. The outstanding diversity of their forms and structures, or morphology, has made them a natural evolutionary laboratory. Conodonts are found in marine rocks across the world, from China to Iran to the Arctic. They are one of the oldest lineages of vertebrates, and are even believed to be some of the earliest vertebrates.

The global abundance of their millimetre-sized teeth, rapid evolution, and their use in estimating the age of marine rocks through the duration of their existence have made them among the most useful fossils in the world. The fossils, which come in a variety of shapes, from simple 'cones’ from which they get their name (conodont = cone tooth) to broad molar-like platforms, delicate bars and blades.

Despite decades of intensive studies in academia and industry, researchers remained puzzled by the function of these teeth and how they fit into the food chain.

The team of authors from Canada, Germany, the Netherlands, and Sweden compared species within individual ecological communities extracted from rocks over 400 million years old from the island of Gotland, Sweden.

The authors adopted a method for establishing diet from the toolbox of archaeologists: they examined the relative abundance of chemical elements including strontium, barium, and calcium, all of which are impacted by diet, to determine whether different conodont species living together in the same environment would have different dietary preferences.

Large variety of dietary preferences

The researchers found distinct chemical compositions for various conodont species, indicating a variety of dietary preferences and niches. These broad food preferences are likely to have contributed to the great diversity in the shapes of conodont teeth, and may have been a key factor to the longevity of the group.

Conodonts were enormously successful ecologically, surviving multiple mass extinctions, including the world's largest at the end of the Permian Period, an event that wiped out over 95 per cent of all marine species.

As anyone who has been to a large dinner party knows, there are always a wide variety of food options available, but with limited quantities. Developing a strategy to maximize one’s intake of the most appealing dishes is paramount to going home well fed, and this principle can be extended to the ancient conodonts as well.

Adapting to consuming different foods has been among the most powerful drivers of evolution, and this study shows that conodonts may have been particularly good at finding their own dining strategies and ecological niches.