An international team of palaeontologists has returned from a month-long expedition to East Greenland, where it collected fossils of the so-called ‘four-legged fish’ - the first vertebrates that left the water, almost 400 million years ago. Dr Grzegorz Niedźwiedzki from the PGI-NRI was the leader and organiser of this expedition.

The team conducted excavations at two sites on Ymer Island, where new layers with the remains of early quadrupeds had already been discovered in 2016.

‘These discoveries will revolutionise our understanding of the early evolution of terrestrial vertebrates’, states Grzegorz Niedźwiedzki.

The aim of the expedition was to study an important but almost unknown time interval in the history of terrestrial vertebrates – the transition between the Devonian and Carboniferous periods, which coincided with a major mass extinction. It has been known for long that terrestrial vertebrates (also known as quadrupeds, in other words animals with legs instead of even fins) evolved from fish during the Devonian period, which lasted from 419 to 359 million years ago. The first fossils of Devonian quadrupeds were discovered in Greenland by a Swedish-Danish expedition led by scientists from the Swedish Museum of Natural History in Stockholm in the 1930s. The Devonian quadrupeds discovered became known as ‘four-legged fish’ because they retained some of the features of their fish ancestors, such as the tail fin. The first specimen discovered was named Ichthyostega.

1st work post of the international research team

This time, in addition to numerous bones, including fragmentary skeletons, the international team also discovered coprolites (fossilised faeces), tracks and imprints of quadruped bodies. In addition, fossils of forkbeards and fern-like plants, scorpion carapaces and palaeoenvironmental data collected from the layers with bones will provide a better understanding of the subtropical environment in which the ‘four-legged fish’ were living.

Thirty boxes, with more than 700 kg of fossils in them, are already on their way to Uppsala. Paleontologists have several years ahead of them to study this material, largely on the basis of synchrotron microtomography (three-dimensional X-ray imaging), which will be carried out at the European Synchrotron Radiation Facility (ESRF) in France.

‘We can say that by using X-rays we will open another door into this still mysterious Devonian world’, explains Grzegorz Niedźwiedzki.

2nd work post of the international research team

The expedition has been funded by the European Research Council (ERC Advanced Grant ERC-2020-ADG 10101963 ‘Tetrapod Origin’). The participants were Grzegorz Niedźwiedzki (Uppsala University and the Polish Geological Institute-National Research Institute), Henning Blom, Daniel Snitting, Martin Qvarnström (all from Uppsala University), Tomasz Sulej (Polish Academy of Sciences), John Marshall (University of Southampton, UK) and Christopher Berry (Cardiff University, UK).

Text and photos: Grzegorz Niedźwiedzki