Guimarota

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Guimarota is a disused coal mine near Leiria in Portugal. A few years after mining ceased in 1961, the mine gained worldwide fame as the largest and most important fossil deposit for early mammals and other vertebrates from the Upper Jurassic period (about 150 million years ago). In 1982 the excavations had to be stopped.

History of the excavations

The first finds were made by the Berlin paleontologist Walter Georg Kühne in 1959 on the mine dump . At that time the pit in which two seams were mined underground was still active. The first excavation campaigns were made in 1960 and 1961 by employees of the Free University of Berlin with the support of the miners. After the pit was closed, the excavation activities concentrated on material from the dumps until this collection was stopped in 1968. This first excavation period proved to be extremely successful, a total of 74 jaws and more than 1,300 individual teeth of Jurassic mammals were found, making Guimarota the most important finding site of Mesozoic mammals even then .

In 1972 one of the largest and most successful enterprises in the history of paleontology began in Guimarota. Under the direction of Bernard Krebs , a former assistant of Kühne, and his colleague Siegfried Henkel , two paleontologists from the Free University of Berlin, underground operations at the mine were resumed for purely scientific purposes. Until 1982 the coal mine was operated with the local miners under the direction of the Free University of Berlin, whereby 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 broken underground and then split into small pieces on the surface by local helpers and examined for fossils. Detected fossil remains were marked and the coal lumps were shrink-wrapped in plastic bags to be later prepared in the laboratories in Berlin . The remaining coal was chemically processed and washed ( slurried ) through sieves in order to extract even very small fossil remains. Using this method, tens of thousands of vertebrate remains were recovered in Guimarota, giving a unique insight into a Jurassic ecosystem .

In 1982 the excavations were stopped because the maintenance of the mine could no longer be financed. Since then, the pit has been filled with water and is no longer accessible.

The finds

Although Guimarota received worldwide attention mainly through the mammal finds, remains of almost all vertebrate groups of a terrestrial ecosystem from the Jurassic period were found there . Fish are occupied by both sharks and bony fish . Among the amphibians there are mainly Albanerpetontiden , a group of small, salamander- like animals with a burrowing way of life that only became extinct in the Miocene . There is only very fragmentary evidence of turtles , suggesting at least three different species.

Live reconstruction of Goniopholis

Very divers is the lizards - fauna . In Guimarota there are early representatives of the Scincomorpha and the Anguimorpha , which in both cases is one of the oldest records of these groups. Crocodiles are among the most common finds in Guimarota. Small, amphibious crocodiles, such as the genus Goniopholis, are particularly common . In addition, however, there were also remains of the giant sea ​​crocodile Machimosaurus and a small, terrestrial crocodile, Lisboasaurus .

The dinosaur fauna is also very rich in species . It is noticeable that practically all remains come from small animals, which is probably related to the ecosystem and the conservation conditions ( taphonomy ). Also unusual is that the vast majority of remains come from carnivorous dinosaurs ( theropods ), including one of the earliest tyrannosaurs , Aviatyrannis . Sauropods are only represented by teeth, presumably those of a brachiosaurid , and ornithopods are represented by the small, basal euornithopod phyllodon and at least one indeterminate iguanodon animal. Individual teeth also suggest that the primeval bird Archeopteryx also occurred in Guimarota, which would be the first evidence of this animal outside of the Solnhofen limestone .

Replica of the almost complete Henkelotherium fossil in the site

The mammalian fauna of Guimarota is of particular scientific importance. A primitive mammal is the Docodonte Haldanodon , a small, burrowing animal, presumably similar to a modern mole . Numerous fossils of multituberculates have been discovered, a total of 18 species have been described . Multituberculates are a primeval group of mammals that assumed the ecological status of rodents in the Mesozoic era and only became extinct with the spread of real rodents. Of particular interest are the Eupantotheres , who were the most advanced mammals of their time and are already close to the origin of modern mammals ( Theria : marsupials and placentas ). Two groups of the Eupantotheren occur in Guimarota, the Dryolestiden and the Peramuriden . The latter includes the first almost complete skeleton of a Jurassic mammal to be found. This skeleton was described by Bernard Krebs in 1991 as the Henkelotherium .

habitat

Based on the fossil finds and the sedimentology of Guimarota, the habitat can be reconstructed. Accordingly, it is apparently a coastal swamp that was periodically inundated by the sea, which explains the marine fauna elements, such as the sharks.

literature

Individual evidence

  1. ↑ a b Thomas Martin: Professor Bernard Krebs passed away ( Memento of November 7, 2005 in the Internet Archive ), Paläontologie aktuell, issue 44, July 2001, page 2.

Web links

Coordinates: 39 ° 42 ′ 0 ″  N , 8 ° 48 ′ 0 ″  W.