Museum of Natural History Berlin
New early saurian species from the 290-million-year-old Bromacker fossil site (Lower Permian) sheds light on the evolution of herbivores and early terrestrial vertebrate ecosystems. A study conducted by researchers from the Museum für Naturkunde Berlin (MfN) and the Humboldt-Universität zu Berlin (HU) reveals a new species of an early saurian from the Bromacker fossil site in Thuringia. First author and doctoral student Jasper Ponstein and his colleagues analysed fossil skulls and lower jaws of the early herbivorous dinosaur group Diadectomorpha. A third species within this group was thus identified at Bromacker, which in turn was categorised as a new second species within the genus Diadectes. This adds to the already species-rich fauna of this herbivore-dominated ecosystem from the Lower Permian. The results were published this week in the journal Royal Society Open Science.
The Bromacker fossil site in the UNESCO Global Geopark Thuringia Inselsberg - Drei Gleichen, represents a unique fossil ecosystem in this form, which harbours a species-rich, early terrestrial vertebrate fauna. Since 2020, it has been the subject of an ongoing research project funded by the Federal Ministry of Education and Research(BMBF ) in collaboration between the Museum für Naturkunde Berlin, the Friedenstein Foundation Gotha (where the fossils are housed), the Friedrich Schiller University Jena and the Geopark. "The BROMACKER project is a prime example of an innovative and interdisciplinary research and science communication programme that builds on several decades of international cooperation," says project manager Prof. Jörg Fröbisch.
Since the 1990s, palaeontologists have described fossil specimens of Diadectes from the Bromacker and assigned them to a single species: Diadectes absitus. Diadectes belongs to the Diadectidae, a group of heavily built tetrapods with massive jaws and molar-like teeth that could crush plant material. The Diadectomorpha include the earliest known herbivorous land vertebrates, which evolved 305 million years ago in North America during the Late Carboniferous. During the Late Carboniferous and much of the Early Permian, herbivores remained a rare component of their respective ecosystems.
The 290-million-year-old Bromacker fossil site is famous for preserving the earliest ecosystem in which herbivorous vertebrates occur in large numbers, documenting the origin of the modern food pyramid of modern terrestrial ecosystems. The herbivore finds at Bromacker include numerous and excellently preserved skeletons of diadectomorphs such as Diadectes absitus and Orobates pabsti, the pot-bellied caseid Martensius bromackerensis and the small, agile, lizard-like bolosaurid Eudibamus cursoris.
The team used traditional palaeontological techniques in combination with computer tomography (CT). The researchers analysed various skulls of diadectomorphs, including Orobates and Diadectes from the Bromacker, in the CT laboratory of the Berlin Natural History Museum. "These skulls are preserved in such a way that the jaws are firmly attached to the skull. Important features related to feeding, such as the row of teeth and the shape of the jaw joint, are hidden by the skull," says Jasper Ponstein. "Using the CT scans, we were able to reconstruct these areas and compare the different specimens and species with each other."
The CT scans show that the Bromacker diadectomorphs have a sinuous row of teeth in the lower jaw, two rows of cone-shaped teeth in the palate and a long, shovel-like projection on the temporomandibular joint. The teeth of the lower jaw are widely spaced to enlarge the chewing surface. This shovel-like projection of the temporomandibular joint contributes to the structural support of the jaw during chewing. These adaptations enabled the diadectomorphs to chew vegetation more effectively. In addition, the CT scans show some replacement teeth in the palate, suggesting that the diadectomorphs occasionally replaced their palatal teeth as well.
The new observations on the skull anatomy of Diadectes lead Ponstein and colleagues to conclude that there are enough differences between the skulls to name a new species: Diadectes dreigleichenensis. "We named the species after the UNESCO Global Geopark Thuringia Inselsberg - Drei Gleichen, which is also home to the world-famous Bromacker fossil site. The species name is derived from "Drei Gleichen", in reference to the seemingly similar-looking three diadectids from the Bromacker, which look like three iconic medieval castles, each located on a hilltop between Gotha and Erfurt and within the geopark," says Ponstein.
The fourth summer excavation as part of the ongoing BROMACKER project will take place from 15 July to 9 August 2024. Interested parties can look over the shoulders of the scientists during guided tours in German and English at the excavation site or become researchers themselves at events for children in the BROMACKER lab at Friedenstein Castle in Gotha.
Further information on the programme and registration
Publication: Ponstein, J., MacDougall, M.J., and Fröbisch, J. 2024. A comprehensive phylogeny and revised taxonomy of Diadectomorpha with a discussion on the origin of tetrapod herbivory. Royal Society Open Science.