Camadas de Guimarota

Guimarota is a disused coal mine near Leiria in Portugal. Some years after the cessation of mining pit in 1961 gained worldwide fame as the largest and most significant fossil site for early mammals and other vertebrates from the time of the Upper Jurassic ( about 150 million years ago ).

History of excavations

The first discoveries were made by the Berlin paleontologist Walter Georg Kühne in 1959 on the heap of the pit. At that time, the pit in which two seams were mined underground, still active. First excavations were made ​​in 1960 and 1961 by members of the Free University of Berlin with the support of the miners further discoveries in the mined coal. After closure of the mine, the excavations concentrated on material from the dumps until they Collections were set in 1968. This first period of excavation proved to be extremely successful, a total of 74 pine and more than 1300 individual teeth were found from Jurassic mammals, which Guimarota was the most important reference Mesozoic mammals even then.

In 1972 began in Guimarota one of the largest and most successful companies in the history of paleontology. Under the leadership of Bernard cancer, a former assistant Bold and his colleagues Siegfried Henkel, two paleontologists from the Free University of Berlin, the underground operations of the mine was resumed for purely scientific purposes. By 1982, as the coal mine was operated with the local miners under the leadership of the Free University of Berlin, where large amounts of fossil vertebrates and other fossils came to light. This company was financed by the German Research Foundation (DFG).

During the excavations coal was crushed days and then cleaved at the surface of local helpers in small pieces and examined for fossils. Discovered Fossil remains have been marked and the lump of coal wrapped in plastic bags, to be later prepared in the laboratories in Berlin. The remaining carbon was chemically treated and washed through sieves ( elutriated ) to win even very small fossil remains. Through this method, tens of thousands of remains were recovered by vertebrates in Guimarota that provide a unique insight into a Jurassic ecosystem.

In 1982, the excavations were stopped because the maintenance of the mine was no longer financially viable. Since then, the pit is filled up with water and no longer accessible.

The finds

Although Guimarota mainly attracted attention worldwide by the mammalian remains, residues found there almost all vertebrate groups of terrestrial ecosystem from the Jurassic period. Fish are occupied by both sharks and bony fish. In the amphibians are mainly Albanerpetontiden ago, a group of small, salamander -like animals with grave forming lifestyle that is now extinct until the Miocene. Turtles are occupied only by very fragmentary material, indicating at least three different ways.

Very diverse is the lizard fauna. In Guimarota especially early representatives of Scincomorpha and Anguimorpha come off what belongs in both cases, with the oldest evidence of these groups. Crocodiles are among the most common findings in Guimarota. Particularly common are small, amphibious crocodiles, such as the genus Goniopholis. However there are also found remains of giant sea crocodile Machimosaurus and a small, terrestrial crocodile, Lisboasaurus.

Very rich in species is also the dinosaur fauna. It is striking that virtually all stem remains of small animals, presumably with the ecosystem and the conditions of preservation ( taphonomy ) related. It is also unusual that the vast majority of the remains of carnivorous dinosaurs ( theropods ) comes from, including one of the first tyrannosaur, Aviatyrannis. Sauropods are only teeth, probably the one Brachiosauriden represented, and ornithopods are represented by the small, basal Euornithopoden Phyllodon and at least an indefinite Iguanodontier. Individual teeth also suggests that the Archaeopteryx occurred in Guimarota, thus would be the first evidence of this animal outside the Solnhofen limestone.

Of particular scientific interest is the mammalian fauna of Guimarota. A primitive mammal is similar to the Docodonte Haldanodon, a small grave -producing animal, is probably one of today's mole. There are numerous fossils have been discovered by Multituberkulaten, a total of 18 species have been described. Multituberkulaten are a primitive group of mammals, which occupied the ecological status of rodents in the Mesozoic and became extinct only with the spread of real rodents. Of particular interest are the Eupantotheren, which were the most advanced mammals of their time and already the origin of modern mammals ( Theria: marsupials and placental mammals ) are close to. Two groups of Eupantotheren occur in Guimarota that Dryolestiden and Peramuriden. To the latter part of the first nearly complete skeleton Jurassic mammal that has been found. This skeleton was described in 1991 by Bernard cancer than Henkelotherium.

Habitat

Based on the fossils and sedimentology of Guimarota can reconstruct the habitat. Thus, it is evidently a coastal swamp, which was periodically flooded by the sea, so can the marine faunal elements, such as sharks, explain.