Ecosystem in oil shale

The Messel Pit fossil site near Darmstadt provides unique insights into a warm period 48 million years ago. Today, paleontologists not only look for new species, but also try to comprehensively describe the extinct ecosystem – from biodiversity to nutrient cycles to the climate.


There is a world-class fossil site near Darmstadt: the Messel Pit. She became famous for the discovery of prehistoric horses and the early primate Darwinius massillae, called Ida. Small mammals, bats, terrestrial crocodiles, snakes and frogs as well as the remains of countless species of insects, arthropods, birds, fish and plants complete the very long list of finds. They were discovered in oil shale that had formed at the bottom of a lake. The lake was created by a volcanic eruption around 48 million years ago, in the Eocene era. For almost 100 years, people dug for lignite and oil shale in Messel.

Today the place is strictly protected as a UNESCO World Heritage Site – and no coal is mined, only fossils. The employees of the Senckenberg Society for Natural Research and the Hessian State Museum have been digging through the slate rock for several decades. “Around 600 finds were the result of the nine-week excavation in 2023, a not unusually high amount,” reports Torsten Wappler from the Hessian State Museum in Darmstadt. The lion’s share of the excavated objects, around 80 percent, are insect and plant remains. Fish are also plentiful, although there are only a few species. After all, there are ten to twenty vertebrates that are not fish every year. In 2023 there was even another ancient horse among the finds.

The latest scientific descriptions of the fossils deal with freshwater shrimps, previously unknown species of spiders and birds, and pythons. “Very few fossils of freshwater shrimp are known worldwide,” reports Sonja Wedmann from the Messel Research Department of the Senckenberg Society. On the specimen she examined under the magnifying glass, you can not only see the animal’s external shape and limbs, but also organs such as the animal’s ovaries and chewing stomach.

Senckenberg snake specialist Krister Smith raves about a young python found in the shale in 2023. “This animal is so well preserved that you can even see the cartilage of the long trachea,” he says. Researchers had already discovered a python fossil in Messel in 2020, and original boas had already discovered it. In the Eocene, these families – which were not so closely related – shared the European habitat. “That’s amazing,” Smith marvels. Because today these snakes do not occur together anywhere. Therefore, the theory was that both families of snakes compete so strongly with each other that they cannot coexist. But the fossils contradict this. The giant snakes disappeared from Europe around 15 million years ago due to the climatic cooling in the Miocene. How they got to their current range is unknown.

Reconstruction of an ecosystem

The purely systematic research into prehistoric animals is now increasingly taking a back seat in favor of describing the biodiversity of the time, the relationships between organisms and the paleoclimate. The tropically warm Messel was teeming with animals and plants. “Because of its extraordinary species richness, Messel is a unique site in the world for the study of ecosystems in modern earth history,” says geologist Philipe Havlik, managing director of the World Heritage site. A large group of Messel researchers is currently compiling all data on species abundances from all collections. Based on newer theoretical approaches to calculating biodiversity, they want to estimate how many species lived in Messel and how many they have not yet discovered. For the groups examined so far, there are statistically clear results that a maximum of two thirds of the species that are said to have lived in the region at that time are known, says Smith. The researchers don’t expect any new fish species, but rather many insect and plant species.

The group of herbivorous arthropods was the most species-rich – and it still is today. Two reasons for the emergence of the enormous diversity are discussed: either a large variety of host plants provided many different niches for the invertebrate herbivores. Or each individual plant species offered many different habitats. Thorsten Wappler and his colleagues investigated this question and examined traces of feeding on over 10,500 fossil leaves from Messel and other sites. Depending on their diet and lifestyle, the hungry herbivores left behind different traces that can be used to determine who was nibbling on what. The data suggests that this phylum of animals was able to become so diverse because the diverse range of plant species provided them with many different ecological niches. “We can therefore use fossils to test fundamental theories about the origin of biodiversity and to draw conclusions for modern ecosystems,” states Wappler.

The Messel Pit not only tells the history of animals and plants and their relationships to one another, but it also bears witness to the climate that prevailed there 48 million years ago. The terrain was roughly where southern Italy is today on the globe, i.e. in middle latitudes. Global data indicates a tropical climate in the region. Researchers are currently analyzing what the local climate and weather in the Messel ecosystem were like as part of the VeWA project (Past warm periods as natural analogues of our ‘high CO2‘-climate future) by examining rock samples for certain marker molecules. In this way, you can document the alternation of dry and rainy seasons as well as temperature fluctuations with annual resolution. The result: In Messel it was an average of 20 degrees Celsius, 12 degrees warmer than today.

But why do we even want to know what the weather and climate changes were like in the Eocene period and how they influenced the community? Havlik is convinced: “If we do not understand how things were in the past, we will have difficulty understanding what lies ahead in the future in terms of climate change and the associated changes in biodiversity.”

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