Alcoota

The Alcoota Fossil Beds are an important paleontological site located on Alcoota Station in Central Australia, 200 km north-east of Alice Springs. It is notable for the occurrence of well-preserved, rare, Miocene vertebrate fossils, which provide evidence of the evolution of the Northern Territory’s fauna and climate. The Alcoota Fossil Beds are also significant as a research and teaching site for palaeontology students.

The Alcoota deposit is a series of intermittently interconnected lakes within a large basin. Evidence suggests that the concentration of fossils is due to a phenomenon called ‘waterhole-tethering’: During dry periods, animals concentrated in the intermediate area of the continually shrinking spring-fed lake, resulting in the death of many animals. The Alcoota and Bullock Creek fossil faunas provide evidence that aridification was in progress in northern Australia during the mid Miocene geological time period.

History

The Alcoota Fossil Beds are one of only three known vertebrate fossil sites in the Northern Territory, along with Bullock Creek and the Kangaroo Well site. Although locals had known about the existence of fossils at Alcoota for a long time, it was not until 1962 that the first serious studies were conducted. Further excavations were conducted sporadically until 1984, when the Museum and Art Gallery of the Northern Territory commenced an annual excavation program. In 1988 a permanent field station was erected on site and the valuable Alcoota Beds were fenced in order to provide them with some protection.

The Alcoota fauna is about 8 million years old and has a rich concentration of vertebrate fossils. This makes it especially interesting as it lies between the older faunas of Kutjamarpu (Southern Australia) and Bullock Creek (Northern Territory) and the younger deposits of Riversleigh (Queensland) and Beaumaris (Victoria). Because of its intermediate age, remote ancestors of the well-studied Australian megafauna as well as of some existing forms can be recognised.

Fossils

The fossil deposit consists of a series of bone-bearing lenses on a single horizon. The individual lenses are about one metre across and extend for 170 m. Bones and teeth are so abundant and often tightly packed that it can be difficult to excavate one fossil without breaking the one below it. The fossils indicate the existence of a complex community of marsupials, birds and crocodiles, including the greatest variety of species of Diprotodontidae that has ever been described.

The species found include one of the largest birds that ever lived, Stirton's thunderbird (Dromornis stirtoni), the giant birds Ilbandornis lawsoni and Ilbandornis woodburnei, the wolf-sized powerful thylacine (Thylacinus potens) and the large leopard-sized Alcoota marsupial lion (Wakaleo alcootaensis). Also found at Alcoota are fossils of herds of the wombat-like diprotodontoids Kolopsis torus and Plaisiodon centralis, the trunked Palorchestes painei, Pyramio alcootense as well as other kangaroos, crocodiles, bandicoots, possums and small birds.

See also

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