Aug. 25, 2009 Today, anyone who looks into the Messel Pit, about 20 kilometres southeast of Frankfurt, Germany, will see scattered groups of trees, bushes and grasses. Underlying the vegetation, however, are richly fossiliferous shales. Some astonishingly well-preserved fossil finds were recently recovered by scientists from these deposits, laid down in the former volcanic lake, and add exotic colour and diversity to the Eocene “Messel world” of 47 million years ago. Some representative finds of animals discovered in 2007 and 2008 were recently exhibited.
Not only the world-famous primeval horse browsed at the shores of the lake in the warm, wet climate prevailing at that time (average annual temperature, 25°C). Around Lake Messel, which emerged in a volcanic crater and was surrounded back then by dense primeval forest, lived early ungulates and rodents; the ancestors of today’s birds flew over the cloudy water; insects buzzed through the air; and cold-blooded reptiles basked lazily in the sun. 47 million years ago, Messel was located at the present latitude of Siciliy.
In the annual digs that the Senckenberg Research Institute carries out in the Messel Pit, an average of 3,000 fossil remains are recovered from the shale in this UNESCO World Natural Heritage Site. Some particularly well-preserved fossils discovered in 2007 and 2008 were recently exhibited.
Bulldog of the lizard world
A reptile find about 80 centimetres long has been identified as an early representative of the beaded lizards and Gila monsters (Helodermatidae). This family, known to have existed since the Cretaceous, is found today in the southwest of the USA and Central America. These lizards are renowned not only for a curious combination of strength, tenacity and deliberateness but also for being venomous. Although it is primitive in many ways, the skeleton found in Messel already shows incipient canals in its teeth which lead us to believe that this species was already producing venom.
“The warm climate of the Eocene may have allowed this lineage to migrate along high-latitude routes to Europe. From studies of the limbs and chemical analyses of the bones, we hope to learn more about evolutionary rates and the biology of primitive members of this unique group,” explains Dr. Krister Smith. This young reptile expert from the USA developed a special interest in the pink-spotted descendants of these primeval-looking animals whilst still a schoolboy.
Beautiful beetles, weaver ants, leafcutter bees
A metallically gleaming jewel beetle belonging to the family Buprestidae and the genus Psiloptera still shows off its beautiful coloration, even after 47 million years. “The exquisite coloration is created by refraction at different layers of the chitin carapace,” explains Dr. Sonja Wedmann. The living representatives of the genus can now only be found in the Tropics.
The insect finds of the last two years also include a queen weaver ant that fell into the former Messel Lake during her nuptial flight and drowned there. The living representatives of the Oecophylla genus occur today in the Tropics of Africa and Southeast Asia. Their nests are made of leaves which the female workers weave together with silk from their larvae. “Since we have not yet found any nests in Messel, it has not yet been possible to ascertain whether the weaver ants that lived 47 million years ago could already do that,” says Dr. Sonja Wedmann.
The special fossil evidence of insects includes the discovery of a completely preserved leaf-cutting bee. However, morphological features show that the species found in Messel is not a true member of the leaf-cutter group. In contrast to “real” leafcutter bees, Friccomelissa schopowi apparently built its nest without using plant discs.
Rodent in a fur coat, archaic stars, clambering ungulates
The new find of a Masillamys has been recovered nearly whole and allows identification of the fossilised remains of its stomach contents. The extremely well-preserved outlines of the body reveal a shadow on the skin that leads us to the conclusion that this ancient rodent had a thick, short-haired coat of fur. “The key feature, the single pair of morphologically specialised chisel-shaped incisors, allow the ‘real’ rodent to be instantly recognised,” explains scientist Dr. Thomas Lehmann, who is working on this animal. This individual, which was discovered just before the end of the digging season in September 2007, shows the short legs typical of the genus that lead one to assume that the rodent once lived on the floor of the primeval forest surrounding Messel.
As has happened before, the new find of a Leptictidium auderiense in September 2008 created a certain amount of excitement. Thanks to the BBC documentary “Walking with Beasts,” this archaic mammal became a star among the Messel fossils. Last year’s new find is the first juvenile animal of this genus, which died out at the end of the Eocene. In contrast to its still-primitive teeth, Leptictidium had a highly specialised locomotor system. Its extraordinarily long tail with 40 vertebrae, long back legs and reduced front ones point to a bipedal gait. “However, since features of the lumbar vertebrae might also indicate a hopping gait, we are looking forward to new findings from the fossil discovered in 2008,” explains Thomas Lehmann; he hopes that a new imaging technique will reveal details that cannot yet be discerned.
The new finds also include a Kopidodon macrognathus. Distinct shadows show the long tail to have been bushy, which is typical of the species. The marked bony crest on its skull and the developing permanent tooth in the area of the right canine of the upper jaw indicate that it is an infant male. Although the long canines suggest a predator, the molars indicate that this was a plant-eating ungulate. “We do not yet know enough about the animal’s lifestyle. Some features of the locomotor system, such as the very versatile shoulder, elbow and hip joints as well as the gripping ability of the front limbs indicate a tree-dwelling fruit-eater,” explains Thomas Lehmann. It is an open question whether this species lived in trees or simply moved among the branches. This mammal expert is awaiting further findings from the well-preserved stomach contents of the new find. He remarks that seeds, which are quite often found in the Messel shales, might even put them on the track of the Kopidodon’s favourite fruit.
The missing pieces of the jigsaw are falling into place
Among the total of 6,773 finds that were recovered from the digs in the Messel Pit in 2007 and 2008, there were 1,929 fossilised remains of vertebrates, 1,403 insects and 3,441 plant remains. The information contained in the finds provide the scientists of the Senckenberg Research Institute data on the occurrence of individual species, their bodily structures and lifestyles, and the evolutionary history of animal groups. In addition, the research results help to reconstruct the Eocene environment and give clues to the relationship between climate and biodiversity.
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The above story is based on materials provided by Senckenberg Research Institute and Natural History Museum, via AlphaGalileo.
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