Riversleigh and Naracoorte are among the world's 10 greatest fossil sites: Riversleigh comprises the southern section of Lawn Hill National Park in north-west Queensland; and Naracoorte lies in the south-east of South Australia. The two sites are representative of the development of Australia's mammal fauna during the Cenozic era (65 million years ago to the present).
The faunal assemblages of Riversleigh's fossil fields have profoundly altered understanding about Australia's Middle Cenozoic vertebrate diversity. They span a record of mammalian evolution over 20 million years, providing the first records for many distinctive groups of living mammals, such as marsupial moles and feather-tailed possums, as well as many other unique and now extinct Australian mammals such as 'marsupial lions'.
A combination of factors have given rise to a site where an exceptional diversity of superb fossils providing an unparalleled window into Oligo-Miocene (15-25 million years ago) rainforest faunas that evolved in isolation during Australia's separation from Antarctica. These faunas present the pinnacle of marsupial evolution, predating the late Tertiary placental influx from Asia to Australia and the consequent wholesale re-ordering of faunas in the Plio-Pleistocene epoch (7-2.5 million years ago) as the environment changed from rainforest to semi-arid grassland.
A 15 million-year-old complete skull and almost complete dentition of the monotreme from Riversleigh has already provided a great deal of new information about this highly distinctive group of mammals. Before Riversleigh's fossil record began to unfold, there was only one Tertiary species known of the recently extinct marsupial thylacine (Tasmanian tiger), but different thylacines have been identified from Riversleigh's Oligo-Miocene faunas. Other ancestral marsupial forms found at Riversleigh include mole, bandicoot, marsupial 'lion', koala, wombat, kangaroo and possum. Placental mammals are represented by more than 35 bat species, and the Riversleigh fossil bat record is considered one of the richest in the world.
Naracoorte too, opens a window into a significant period of the Earth's history on a continent dominated by marsupials. The last 170,000 years have been characterized by great climatic changes and the Naracoorte fauna provide a key clue to understanding marsupial responses to these. The Naracoorte assemblage also spans the probable time of arrival of humans in Australia and thus is of additional value in helping to unravel the complex relationships between humans and their environment. Naracoorte caves are also a source of specimens of potential values in DNA analysis of extinct species not always available from studies of swamp/lake/dune recovered fossils.
The Pleistocene fossil vertebrate deposits of Victoria Fossil Cave at Naracoorte are considered to be, in terms of both volume and diversity, Australia's largest and best preserved and one of the richest deposits in the world. Tens of thousands of specimens representing 99 vertebrate species have been recovered, ranging in size from very small frogs to buffalo-sized marsupials. These include superbly preserved examples of the Australian Ice-Age megafauna as well as a host of essentially modern species such as the Tasmanian devil and thylacine, wallabies, possums, bettongs, mice, bats, snakes, parrots, turtles, lizards and frogs.
The landscape at Riversleigh, particularly near the rivers, has a large number of visible archaeological traces of Aboriginal occupation and sites of cultural significance.