1995 - 2016

UNESCO World Heritage Messel Pit Fossil Site 

Senckenberg Nature Museum Frankfurt

An ecosystem in Hesse 48 million years ago

The Messel Pit
The world-famous fossil site “Messel Pit” became a UNESCO World Heritage Site in 1995. In the past, the pit was used industrially for the extraction of crude oil (mineral oil). After the industrial use was discontinued, scientists conducted numerous digs in the area that unearthed a large number of impressive treasures. Many of the exquisitely preserved fossils of animals and plants also allow conclusions about the ecosystem in Messel 48 million years ago.
Formation of the Messel Lake
With a diameter of approximately 1.5 kilometers, the Messel Lake was not particularly large, yet it reached a considerable depth of approx. 300 meters. This shape can be traced back to the lake’s volcanic origins as a maar crater lake. When hot, rising magma from the center of the earth met cold groundwater about 48 million years ago, this led to steam explosions that catapulted hot gases, volcanic ash and rocks to the earth’s surface through a small vent. The pressure waves from the volcanic eruption destroyed the vegetation in a wide radius and formed a deep crater surrounded by a circular wall. Following the explosion, this crater slowly filled with ground water and rain, eventually forming a fresh-water lake.
The Messel Lake in the Eocene
The tropical climate conditions favored the rapid development of a vegetation cover: shrubs, vines, trees and ferns surrounded the lake and stabilized the crater’s rim with their roots. Algae and a carpet of aquatic plants gave the water a dark green to brownish color, and animals began to populate the newly formed habitat as well. In this process, the upper layers of the lake were clearly favored, since they alone offered sufficient heat and particularly oxygen for the majority of living organisms. The calm and dark bottom was untouched by currents and only housed highly specialized bacteria that do not require oxygen for their survival and feed of the sunken remains of dead animals. The high number of fossilized birds and bats, which hunted close to or above the water and later were submerged in the lake, suggests that toxic gases may have risen from the water’s surface.
48 million years ago, Messel was dominated by a tropical climate. The lake was surrounded by a dense jungle that was home to a wide variety of animals and plants. The air was warm and humid and the ground was swampy. At that time, dinosaurs had already been extinct for 18 million years. During the Eocene, the mean annual temperature was about 10 degrees higher than today. The ice of the polar caps had melted, and large parts of Europe were covered by a shallow sea. Tropical-type forests like the one in Messel were found across all of Germany.
Formation of fossils
Since the bottom of the Messel Lake was free of oxygen or currents that could move or fragment the sunken animals and plants, fossils were particularly well preserved in this environment. This is due to the fact that dead organisms can only be preserved over time if they are rapidly and completely covered by sediments. In the course of many millennia, the deposits of clay and single-celled green algae led to the formation of so-called oil shale at the lake bottom. The innumerable instructive fossil discoveries from Messel were all contained in this layer. Thus, a piece of oil shale with a thickness of a mere ten centimeters can reveal a thousand years of geological history.
Fossil discoveries
The fossil discoveries from Messel owe their worldwide renown not least to their exceptional state of preservation. Many of the approximately 51,000 specimens found to date are almost completely preserved and show the finest details. Iridescent colors on beetles, detailed structures in bird skeletons, the obvious outlines of the bodies of various animals, and even stomach contents showing the remnants of the final meal could be discovered. The excellent state of preservation allows numerous conclusions regarding the past diversity of living organisms, the environmental conditions and the evolution of the fauna and flora.
About half of the specimens recovered at Messel are plants. The examination of their exterior appearance allows conclusions as to the climatic and environmental conditions at the time when these plants grew. For example, the size and shape of the leaves can reveal information about the mean annual temperature or the amount of precipitation. And even the percentage of carbon dioxide in the air can be determined by studying the stomata on the underside of the leaves under a microscope. 
Diplocynodon darwinii
The alligator species Diplocynodon darwinii (which literally translates to “Darwin’s double dog-tooth crocodile”) is among the most numerous crocodiles from the Messel Pit. Even juveniles have been found. The occurrence of crocodiles in the Maar lake is a clear indication of the warm climate in the modern-day state of Hesse during the Eocene, about 48 million years ago.
Although no more than eight species of fishes have been discovered in the Messel Lake, they account for 90 % of all vertebrates found at the site. In particular, catfish and the species of gar pictured here with its exceptionally well preserved scale armor are among the more frequent discoveries. In its outward appearance, the latter barely differs from its modern-day relatives.
Prehistoric horses
Some of the most famous discoveries from the Messel Pit are the fossil remains of prehistoric horses. More than 60 skeletons of stallions, foals and mares have been found, with some of the mares even being pregnant. The discovery of fetuses in the mares’ wombs is of particular interest, since it opens a window into the evolution of the reproductive system in mammals. The oldest and best preserved utero-placenta shows that the reproductive apparatus of the prehistoric mare does not differ from that of modern-day female horses, despite about 50 million years of evolution. Its development had already reached the present state at that time. The prehistoric horses only grew to a height of 35 to 60 centimeters (at the shoulder) and weighed no more than 5 to 6.6 kilograms. The shape of their teeth and the stomach contents that were found indicate a diet of leaves and fruits.
Hedgehog relative
The terrestrial insect eaters often used different strategies to access their food. While some of them ate fruit and scraped the ground in search of insects, the hedgehog relative Macrocranion tupaiodon was an omnivore with a predilection for fish. It frequently approached the lake shore to search for dead fishes. This is suggested by its unspecialized teeth as well as preserved stomach contents. The animal, which reached a length of 30 centimeters, had elongated ears and equally long tactile hairs on its snout, which indicate a well-developed sense of touch, smell and hearing. In addition, the short forelegs and relatively long hind legs reveal it as an agile and swift denizen of the forest floor.
Jewel beetle
In total, several hundred species of insects are known from the Messel Pit. Among the most common finds are beetles (approx. 60 % of all discoveries). Even after 48 million years, the iridescent structural colors of this beetle are clearly recognizable. Today, the living relatives of this jewel beetle are restricted to Central and South America.
Prosimians turned to the foliage cover of dense forests to seek protection from predators and occasional flooding. Europolemur kelleri, which was about as big as a domestic cat, used all four of its extremities to climb and jump among the trees. Other species of prosimians found at Messel only reached half that size. Contrary to the prehistoric horses, nothing is known about the prosimians’ reproductive biology; however, it can be assumed that they produced one to two offspring a year, similar to the modern-day lemurs.
Fossil boa
This snake with a length of one meter stands out even among the most exquisitely preserved objects from the Messel Pit. It is the young of an extinct species of boa, and even some of its scales have been preserved. Shortly before its death, it devoured a lizard of the basilisk tribe (Geiseltaliellus maarius), which, in turn, had recently eaten an insect. All three are visible – can you find them?
Fossil Boa
This snake with a length of one meter stands out even among the most exquisitely preserved objects from the Messel Pit. It is the young of an extinct species of boa, and even some of its scales have been preserved. Shortly before its death, it devoured a lizard of the basilisk tribe (Geiseltaliellus maarius), which, in turn, had recently eaten an insect. All three are visible – can you find them?
Ornate-headed lizard
The ornate-headed lizard owes its name to its outward appearance. It has an extremely slender body with a particularly long prehensile tail and a massive, ornate head. In conjunction with its curved claws, these characteristics hint at an arboreal lifestyle. However, the lizard does not appear to have been a swift hunter but rather a large plant eater, which presumably also fed on insects from time to time. To date, only six specimens have been found.
Messel swift
About half of the terrestrial vertebrates found at Messel are birds. Among them is the swift, a member of a highly specialized avian order that shows an extreme adaptation to life in the air. This is reflected, in particular, by the design of its wings, as shown in this fossilized animal, which can be compared to the modern-day Common Swift. It is characterized by the extremely long primaries, which serve as a means of propulsion in birds. The outstanding trait of this particular fossil is the excellent preservation of the feathers, made obvious during preparation, which allows additional scientific conclusions regarding the Messel swift.
Prehistoric bat
This specimen has become downright famous. Like one of the prehistoric horses, it already served as the subject of a postage stamp, and in 1993, it was even taken into space as a mascot aboard the space shuttle Columbia. It is Palaeochiropteryx tupaiodon, by far the most common species of bat from the Messel Pit. The smallest among the bats found at Messel, it reached a wingspan of 25 to 30 centimeters.
Queen ant
This extinct species of ant is the largest known ant and also counts among the largest hymenopterans in general. The queens reached a wing span of up to 16 centimeters. Only winged animals are known to date; a worker ant has yet to be discovered. The presence of a reduced sting apparatus suggests that these ants used chemical substances to defend themselves against enemies.
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Senckenberg Gesellschaft für Naturforschung

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