A mystery that has lasted for decades has finally been solved – the bone turns out to be a pelvic bone from an early saurian.

Today, the 290-million-year-old Bromacker in the UNESCO Global Geopark Thuringia is one of the world's most important fossil sites and is currently being developed through an innovative, interdisciplinary and multimedia cooperation project. In 1974, while excavating the Bromacker site, Thomas Martens, a young geologist who had just graduated from the Freiberg Mining Academy, came across a find that would shape the rest of his life. Decades later, the initially inconspicuous bone find turned out to be a valuable piece of the puzzle in prehistoric research: it is the previously unknown pelvis of an early terrestrial vertebrate. This autumn marks the fiftieth anniversary of the first fossil bone found at Bromacker.

An extraordinary discovery with scientific significance

Before the first bone was discovered, the Bromacker site was mainly known for its fossilised tracks of early saurians, but no bones. Until that time, the scientific doctrine was that these Rotliegend rocks could not contain any bones besides trace fossils. Martens recalls: ‘From the outset, I was sure that what I had uncovered in the rock had to be a bone remnant. At the turn of the year 1974/75, I wrote to Prof. A. H. Müller in Freiberg about the find. He replied: ’Thank you for the information about the bone find in the ro v. Tambach. If this is true, it is very remarkable. Congratulations!' It is understandable that this evaluation by my palaeontology professor encouraged me to continue excavating at Bromacker – with great skeletal finds in the following years as part of decades of international and interdisciplinary research.’

Breakthrough with the latest 3D technologies

As part of the current BROMACKER research project, the mysterious first bone find has now been digitally examined and reconstructed using CT scanning at the Museum für Naturkunde Berlin. The fossil bone was digitally and non-destructively separated from the surrounding rock matrix and viewed in detail from all sides for the first time. ‘The first bone find fascinated me from the very beginning,’ said project manager Prof. Jörg Fröbisch from the Museum für Naturkunde Berlin. ‘With the help of modern and CT-based 3D methods, we were able to isolate the bone, visualise it from all sides and compare it with other finds. It was like a revelation and we immediately realised that this was the pelvis of an early saurian, most likely Dimetrodon, a distant relative of us mammals.’

Dimetrodon teutonis – a new detail of the early saurian

The only species of the genus Dimetrodon discovered at Bromacker so far is Dimetrodon teutonis, a prehistoric relative of today's mammals and known for its distinctive dorsal sail. So far, only an isolated upper jaw, parts of the skeleton of a dorsal sail and of extremities of this species have been found at Bromacker. The discovery of the pelvic girdle complements our previous anatomical knowledge of this species and enables, for example, movement analyses of the animals' locomotion.

A unique site in the UNESCO Global Geopark Thuringia Inselsberg – Drei Gleichen

In addition to the Museum für Naturkunde Berlin, the Friedenstein Foundation Gotha, the Friedrich Schiller University Jena and the UNESCO Global Geopark Thuringia Inselsberg – Drei Gleichen are also involved in the BROMACKER project. Sylvia Reyer-Rohde, head of the Geopark Management Office, emphasises: ‘We are fortunate to have such a unique site here in the UNESCO Global Geopark. Without the commitment of Thomas Martens, this special site would never have been discovered or researched and would not have achieved the international recognition it enjoys today. Research at Bromacker must continue. The fossil deposit is of infinite value for science and for maintaining the UNESCO designation of the geopark and thus for the region and for Thuringia.’

Looking to the future: further excavations and new discoveries

The BROMACKER project started in summer 2020 and is funded by the German Federal Ministry of Education and Research (BMBF). The project places a strong emphasis on science communication: the aim of the collaboration is to combine research and knowledge transfer using the ‘Bromacker’ fossil deposit in such a way that a window is opened to the public on the early evolution of terrestrial vertebrates. The BROMACKER project is funded until summer 2025, and a final excavation in June 2025 promises further finds and insights. At the same time, discussions are already underway about how to proceed after the project ends. The steadily increasing number of finds and new discoveries at Bromacker make it clear that the biodiversity of this prehistoric ecosystem is far from fully understood. Further funding and institutionalisation of research in this region are essential to preserve this unique site as a source of knowledge about the evolution of early terrestrial vertebrates and as a visitor attraction for all generations. The team continues to excavate additional spectacular finds to further explore and tell the story of the Bromacker and its prehistoric inhabitants.

Contact

Dr Gesine Steiner, Spokesperson

gesine.steiner@mfn.berlin