Riversleigh World Heritage Area is Australia's most famous
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
location, recognised for the series of well preserved fossils deposited from the
Late Oligocene
The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/ Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...
to more recent geological periods. The fossiliferous limestone system is located near the
Gregory River in the north-west of
Queensland
)
, nickname = Sunshine State
, image_map = Queensland in Australia.svg
, map_caption = Location of Queensland in Australia
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, establishe ...
, an environment that was once a very wet rainforest that became more arid as the Gondwanan land masses separated and the Australian continent moved north. The approximately area has fossil remains of ancient mammals, birds, and reptiles of the
Oligocene and
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
ages, many of which were discovered and are only known from the Riversleigh area; the species that have occurred there are known as the
Riversleigh fauna Riversleigh fauna is the collective term for any species of animal identified in fossil sites located in the Riversleigh World Heritage Area.
Faunal zones
The presence of the Riversleigh in the Oligo-Miocene has been exceptionally well preserved ...
.
The fossils at Riversleigh are unusual because they are found in soft freshwater
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
which has not been compacted.
This means the animal remains retain their three-dimensional structure, rather than being partially crushed like in most fossil sites. The area is located within the catchment of the
Gregory River.
Many of the fossil sites were crevices and
limestone caves created by the action of large amounts of water on the
karst formation, creating
pitfall trap
A pitfall trap is a trapping pit for small animals, such as insects, amphibians and reptiles. Pitfall traps are a sampling technique, mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to esca ...
s and feeding spots for predators which periodically and perhaps suddenly became covered and preserved; these conditions are responsible for the large assemblages of fossilised bats whose
guano helped to conserve the remains of themselves and others.
Fossils were first noted to exist in the area in 1901.
An initial exploration survey was conducted in 1963. Since 1976, the area has been the subject of systemic exploration.
The site was co-listed with the
Naracoorte Caves National Park
Naracoorte Caves National Park is a national park near Naracoorte in the Limestone Coast tourism region in the south-east of South Australia ( Australia). It was officially recognised in 1994 for its extensive fossil record when the site was in ...
in
South Australia
South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
as a
World Heritage
A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for ...
site in 1994, and by itself, it is an extension of the
Boodjamulla National Park
Boodjamulla National Park, formerly known as Lawn Hill National Park, is a national park in the Shire of Burke, Queensland, Australia. The Riversleigh World Heritage Area is a World Heritage Site within the park.
The park lies on the traditiona ...
.
Description
Fossils at Riversleigh are found in limestone by lime-rich freshwater pools, and in caves, when the
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
was evolving from rich
rainforest to semiarid
grassland
A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
community. Some of the fossils at Riversleigh are 25 million years old.
High concentrations of
calcium carbonate have meant the fossils are extremely well preserved.
The fossil collection reveals mammalian evolution across more than 20 million years.
Fossils have been found in more than 200 individual locations.
The fossil record here is significant because it provides evidence on evolution and the distribution of species across
Gondwana.
The presence of Riversleigh fauna in the Oligo-Miocene has been classified by four "faunal zones", and used to denote the presence of fossil taxa in these time periods.
These may be summarised as
* Faunal Zone A (FZA):
Late or Upper Oligocene, 28.4 to 23.03 million years ago
* Faunal Zone B (FZB):
Early or Lower Miocene, 23.03 to 15.97 Ma
* Faunal Zone C (FZC):
Middle Miocene, 15.97 to 11.608 Ma
* Faunal Zone D (FZD):
Late or Upper Miocene, 11.608 to 5.332 Ma
Thirty-five fossil
bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
species have been identified at the site, which is the richest in the world.
Cave deposits have been particularly rich in bat species.
The skull and nearly complete dentition of a 15-million-year-old
monotreme, ''
Obdurodon dicksoni
''Obdurodon'' is a genus of extinct platypus-like Australian monotreme which lived from the Late Oligocene to the Late Miocene. Three species have been described in the genus, the type species ''Obdurodon insignis'', plus ''Obdurodon dicksoni'' ...
'', provide a window into the evolution of this characteristically Australian group. Fossil ancestors of the recently extinct
thylacine
The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct carnivorous marsupial that was native to the Australian mainland and the islands of Tasmania and New Guinea. The last known live animal was captured in 1930 in Tasma ...
, ''Thylacinus cynocephalus'', have also been identified among Riversleigh's fauna. In 1993, skulls of the koala-like ''
Nimbadon
''Nimbadon'' is an extinct genus of diprotodont marsupial, that lived from the Late Oligocene to the Miocene epoches. Many fossils have been found in the Riversleigh World Heritage property in north-western Queensland. Unlike most members of ...
'' were unearthed in a previously unknown cave in the region.
Researchers estimate that this
marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...
first appeared about 15 million years ago and died out about 12 million years ago, perhaps from climate change-induced losses in habitat. A well-preserved skull of the ancient ''
Nimbacinus dicksoni'', an extinct relative of the thylacine, has been used to determine the hunting behavior of the species.
Other fossils have provided evidence of how the
koala
The koala or, inaccurately, koala bear (''Phascolarctos cinereus''), is an arboreal herbivorous marsupial native to Australia. It is the only extant representative of the family Phascolarctidae and its closest living relatives are the w ...
has evolved in response to Australia's change from predominant rainforest vegetation to drier
eucalypt
Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera (of the tribe Eucalypteae) found across Australasia:
''Eucalyptus'', ''Corymbia'', ''Angophora'', '' Stockwellia'', ''Allosyn ...
forests.
The fossil bird fauna at Riversleigh includes an artamid ''
Kurrartapu johnnguyeni'', a fossil sittella, and representatives of various other families of modern birds. Some fossil insects and plants have also been discovered.
The fossil species identified at the sites are collectively known as the
Riversleigh fauna Riversleigh fauna is the collective term for any species of animal identified in fossil sites located in the Riversleigh World Heritage Area.
Faunal zones
The presence of the Riversleigh in the Oligo-Miocene has been exceptionally well preserved ...
.
Research
Scientific studies are mostly conducted by a group of
palaeontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
s from the
University of New South Wales
The University of New South Wales (UNSW), also known as UNSW Sydney, is a public research university based in Sydney, New South Wales, Australia. It is one of the founding members of Group of Eight, a coalition of Australian research-intensiv ...
.
Mike Archer is a paleontologist who has been working at Riversleigh since 1983. He and his co-workers discovered that diluted
acetic acid was the most effective method of extracting fossils.
Karen Black
Karen Blanche Black (née Ziegler; July 1, 1939 – August 8, 2013) was an American actress, screenwriter, singer, and songwriter. She rose to prominence for her work in various studio and independent films in the 1970s, frequently portrayi ...
, a palaeontologist from
UNSW, discovered a new species of extinct koala, at Riversleigh, which was then named after Dick Smith.
See also
*
List of fossil sites
This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of t ...
*
Agate Fossil Beds National Monument
Agate Fossil Beds National Monument is a U.S. National Monument near Harrison, Nebraska. The main features of the monument are a valley of the Niobrara River and the fossils found on Carnegie Hill and University Hill.
The area largely consists of ...
*
Santa Rosa local fauna
*
Messel pit
The Messel pit (german: Grube Messel) is a disused quarry near the village of Messel (Landkreis Darmstadt-Dieburg, Hesse) about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of well-preserved ...
*
Laguna del Hunco Formation
*
Posidonia Shale
The Posidonia Shale (german: Posidonienschiefer, also called Schistes Bitumineux in Luxembourg) geologically known as the Sachrang Formation, is an Early Jurassic (Toarcian) geological formation of southwestern and northeast Germany, northern Swit ...
References
Further reading
* Archer, M. et al. 1991. ''Riversleigh: the Story of Australia's Inland Rainforests'', (Sydney: Reed Books)
External links
World heritage listing for RiversleighUNESCO site with information on Riversleigh, AustraliaInformation about fossils from Riversleigh, Australian MuseumThe Riversleigh Society supports scientific research at Riversleigh
{{Authority control
Oligocene paleontological sites
Miocene paleontological sites
Lagerstätten
North West Queensland
Australian National Heritage List
World Heritage Sites in Queensland
Protected areas of Queensland
Fossil parks in Australia
Fossil trackways
Cenozoic paleontological sites of Australia