Current research
With 72 (and increasing) researchers from 28 institutions and 9 countries (France, Germany, Czech Republic, England, U.S.A., Canada, Argentina, New Zealand & Australia cooperating in the analysis of the diversity and significance of the Riversleigh and Murgon resources, the international as well as national significance of the fossil records of more than 83 families of distinctive Australian creatures represented in these deposits is becoming clear.
Murgon Project
Each year, the Tingamarra Local Fauna (LF) from the Murgon deposit has grown with addition of new mammals, birds, amphibians and reptiles. Murgon material has been the subject of two research theses supervised by Archer and many publications with more in preparation. International cooperative research projects involving Murgon are steadily increasing with a focus on colleagues from France, Argentina and Czech Republic.
About half of the Murgon taxa discovered have turned up within the last two years of investigation demonstrating that we are still very much on the steep side of the learning curve about the Tingamarra LF. For the last three years, one to two field trips per year have been conducted, depending on resources, and more than 8 tonnes of vertebrate-rich clays processed per year. At the current rate, about 60 scientifically assessable specimens, including complete (crocodile) and partial (mammal) skulls of some taxa, are produced each year, a success rate higher than we achieved processing the mammal-rich, late Oligocene clays in South Australia that produced the relatively derived Ditjimanka LF of central Australia.
1. Main points of general significance that have developed from Murgon research
- Although illite from the deposit was dated (K/Ar) by AMDEL as >54.6 +/- 0.5 mybp, controversy focuses on this date; accumulating palaeontologica
l evidence, however, supports the original interpretation. - This is the only marsupial-beari
ng deposit from the Australian portion of Gondwana older than 24 Ma. - Considering the date of final severance of Australia from Antarctica (about 35 Ma ago, depending on authority), the Murgon deposit predates isolation of Australia and, as such, is of paramount importance in providing the only opportunity to document the nature of Australia's (and possibly eastern Gondwana's) ‘pre-spli
t' Cainozoic biota. - Murgon also provides the only view of Australia's mammal fauna shortly after the start of the 'Age of Mammals' (65 mya) when mammals elsewhere underwent major adaptive radiations.
2. Significant Murgon discoveries
- Discovery of Australia's oldest frogs.
- Discovery of urodeles (salamanders), the first demonstration that this cosmopolitan group existed in Australia.
- Discovery of Australia's oldest madtsoiid snakes; these are referred to Alamitophis and Patagoniophis, genera previously only known from the Cretaceous of Argentina.
- Discovery of trionychid turtles with affinities to American rather than (as expected) Eurasian forms.
- Discovery of the oldest known mekosuchine crocodiles (Kambarra).
- Discovery of the world's oldest songbirds (passerines) by 20 million years.
- Discovery of graculavids with affinities to Cretaceous & Paleocene bird taxa.
- Discovery of the oldest bat in the Southern Hemisphere (Archaeonycteris) and among the oldest in the world;
- Discovery of a probable placental condylarth (Tingamarra) which challenges understanding about the origins of the balance of mammals now distinguishing Australia. We have now found a second, larger form that is very similar.
- Discovery of a very enigmatic marsupial (Thylacotinga) with affinities to Peruvian and Argentinian Paleocene and early Eocene taxa.
- Discovery of a new species of Chulpasia, a genus otherwise only known from the late Paleocene of Peru-the first genus of land mammals known to span the Southern Hemisphere.
- Discovery of Australia's first undoubted microbiotheriid
s such as a taxon close to the Paleocene Mirandatherium from Argentina; this discovery corroborates anatomical and biochemical studies that suggest microbiotheriid s are the sister-group of all or part of the Australian marsupial radiation. - Discovery (Djarthia) of the oldest australidelphia
n, marsupials unique to Australia and South America. - Discovery of a caroloameghinii
d-like marsupial that resembles early Eocene Argentinian taxa. - Discovery of an apparent perameloid marsupial which would be the oldest known bandicoot.
Riversleigh Project
With discovery in 1983 of two vast regions of highly fossiliferous middle to late Tertiary sediments, annual expeditions have provided research materials documenting the deep history and diversity for almost all families of living and as many again of extinct Australian mammals and other vertebrate groups. Each year's field research has resulted in discovery of new deposits, new taxa and sometimes new time frames. Field and laboratory research has accelerated over the last three years. Riversleigh's fossil fields have now been: 1, excised from Riversleigh Station; 2, added to Lawn Hill National Park; 3, gazetted on the National Estate of Australia; and 4, successfully nominated by the Australian Government for inscription on the World Heritage list as ‘Australi
1. Points of general significance about the research at Riversleigh supervised and or initiated by Archer
- Riversleigh's Cainozoic fossil deposits span the late Oligocene to Holocene, with gaps of uncertain duration.
- This record includes one of (if not the) longest for rainforest communities anywhere in Meganesia.
- It includes palaeocommuniti
es that appear to be ancestral to the modern World Heritage Wet Tropics property in northeastern Queensland, extending understanding about the origins of this unique modern resource back to at least 24 Ma. - Discovery here of the oldest representatives of generic-level groups that characterise modern rainforests (e.g., lyrebirds, logrunners, musky rat-kangaroos, cuscuses, woolly ringtail possums and striped possums).
- Because most of the richest Tertiary assemblages from Riversleigh are dominated by forest creatures, they complement those from other areas of the continent mostly dominated by aquatic creatures.
- Riversleigh's record spans the critical 15-14 million year period when global climates shifted from greenhouse to icehouse conditions enabling increased understanding about changes that may accompany a modern greenhouse shift. Because comparable changes on other continents were normally accompanied by faunal interchanges, changes in isolated Australia may now provide the only opportunity to understand inherent community responses to greenhouse/iceh
ouse shifts. - Riversleigh's record spans the late Miocene decline in closed forests, their replacement by open forests and (by Pliocene/Pleist
ocene time) development of grasslands. - The Riversleigh record includes the most diverse Tertiary assemblages known from Australia, combining archaic forms previously known from central Australia with progenitors for, or plesiomorphic relatives of, most living groups.
- Riversleigh has produced the first fossil records for many genera, families and even orders (e.g., marsupial moles) with still-living species.
- Riversleigh research has more than trebled previous knowledge about the diversity of Australia's terrestrial Tertiary mammals with over 250 new species, new genera, families and orders; comparable increases in knowledge have also occurred here for other groups of Australian vertebrates such as frogs, turtles, snakes and birds (particularly forest birds).
- Because most of the fossil deposits at Riversleigh are in situ freshwater lacustrine limestones, preservation is often almost perfect enabling detailed anatomical as well as systematic studies.
- Preliminary ecological analyses demonstrate that even Riversleigh's most diverse communities appear to represent single (not mixed) communities.
- Several Riversleigh taxa have suggested rainforest ancestry for groups that today have mainly or exclusively dry country representation (e.g., emus, phascolarctids, notoryctids and pygopodids).
- The only Pliocene site in Australia dominated by small terrestrial mammals and the only one rich with diverse bat and rodent assemblages (the latter possibly the oldest known in Australia) is Rackham's Roost Site at Riversleigh.
2. Significant Riversleigh discoveries
- Discovery of the first fossil plants (with insects) at Riversleigh (Dunsinane Site).
- Discovery of often spectacularly preserved fossil insects (e.g. butterflies, beetles etc.), millipedes & isopods from Miocene sites, many of which exhibit fossilised muscles, eyes, bacteria and even fungi.
- Discovery of many Miocene lungfish that overlap with taxa known from central Australia.
- Discovery of many new kinds of turtles including one of Australia's most plesiomorphic meiolaniids, Australia's only fossil Pseudemydura, many of its oldest (late Oligocene and Miocene) chelids etc.
- Discovery of a new giant Pleistocene chelid (Elseya lavarackorum) which was described first as a fossil and later found alive.
- Discovery of a plethora of very strange mekosuchine crocodiles (one of which may have been 10m in length) including some that appear to have been terrestrial and possibly even arboreal, and some of Australia's oldest crocodylines.
- Discovery of Australia's only fossil pygopodid lizards.
- Discovery of Australia's oldest agamid lizards.
- Discovery of a plethora of archaic madtsoiid snakes.
- Discovery of Australia's oldest-known elapid, typhlopid (only fossils known) and pythonid snakes.
- Discovery of many new kinds of birds (Riversleigh providing the first significant information about the history of Australia's non-aquatic, forest birds) including, of particular importance, Australia's oldest parrots, only fossil budgerigar, only fossil lyrebirds, oldest known kingfisher, only fossil logrunners, only fossil swiftlets, most complete material of Emuarius (an ancestral emu), a crane with African affinities, a swivel-legged raptor unique to Australia and many other birds presently under study.
- Discovery of a giant toothed platypus, Obdurodon dicksoni, represented by the most complete skull of a fossil monotreme known.
- Discovery of a weird new Order of mammals unique to Riversleigh, the yalkiparidontia
ns. - Discovery of many other strange groups of presumably Gondwanan mammals such as the Yingabalanarida
e. - Discovery of more than seven new kinds of thylacines ranging from rat- to dog-size carnivores, including an archaic species of Thylacinus.
- Discovery of the first-known Tertiary skeleton of an extinct thylacinid.
- Discovery of many new kinds of dasyurid-like carnivores as well as highly derived forms from the late Miocene Encore Site and from the Pliocene Rackham's Roost Site.
- Discovery of an enormous range of perameloid bandicoots, most represented by complete skulls, ranging from mouse- to cat-size, all belonging to the extinct family Yaralidae.
- Discovery of Australia's only fossil notoryctids (marsupial moles).
- Discovery of the most diverse sequences and most plesiomorphic Tertiary marsupial lions, including a complete skull referable to Priscileo, as well as a potential common ancestor for Wakaleo and Thylacoleo.
- Discovery of a series of fascinating new vombatoids (wombats) representing 3 different families that document evolutionary transition from low-, complex-crowned and rooted forms to (in Encore Site) hypselodont forms.
- Discovery of a wide range of diprotodontids including the most plesiomorphic zygomaturines and diprotodontines known.
- Discovery of a spectacular ontogenetic growth series (more than 24 well-preserved skulls) of a sheep-sized, plesiomorphic zygomaturine, Nimbadon lavarackorum.
- Discovery of many kinds of palorchestids including species of the otherwise southern Australian genus Ngapakaldia and, from Encore Site, a form seemingly ancestral to Palorchestes painei from Alcoota.
- Discovery of many kinds of new early to early late Miocene koalas including the most plesiomorphic genus known and, in Encore Site, antecedents of Phascolarctos.
- Discovery of several different kinds of wynyardiids, including complete skulls of Namilamadeta.
- Discovery of ilariids including the juvenile and adult dentitions of Kuterintja gnama, a taxon also known from the Mammalon Hill LF of central Australia.
- Discovery of Australia's only extinct acrobatid possums.
- Discovery of Australia's only fossil striped possums, Dactylopsila.
- Discovery of a large sample of Australia's oldest and most plesiomorphic Burramys and the oldest known representative of the Cercartetus pygmy-possums.
- Discovery of many new Tertiary petaurid possums.
- Discovery of at least 18 Tertiary ringtail possum species (some known from whole skulls), including representatives of all previously known Oligo-Miocene genera as well as many unique to Riversleigh and the first Tertiary record of modern lineages (Pseudochirops).
- Discovery of new and archaic miralinid possums, the first outside of central Australia.
- Discovery of Australia's oldest phalangerids and new taxa under study.
- Discovery of representatives of three distinct lineages of ektopodontid possums, none of which have previously had a fossil record from the northern half of the continent.
- Discovery of in excess of 40 different kinds of kangaroos, many of them represented by complete skulls and in some cases partially articulated skeletons, including hypsiprymnodont
ids, propleopines, balungamayines, potoroines, balbarines, a tusked kangaroo, etcetera. Taken together, Riversleigh's Tertiary kangaroo suites are the most diverse and best preserved on the continent. - Discovery of a kangaroo that has a tooth it used for two entirely different purposes at two different stages in its life.
- Discovery of an articulated skeleton of the most archaic kangaroo yet known.
- Discovery of new pilkipildrid possums, a group distantly related to petaurids.
- Discovery of at least 12 new early Pliocene muroid rodents, Australia's most archaic, including one that belongs to the Dendromurinae which has living representatives only in Africa.
- Discovery of at least 20 species of hipposiderid bats including representatives of otherwise uniquely Eurasian genera, the only known ancestors for unique modern Australian hipposiderids and several new, extraordinarily distinctive genera.
- Discovery of at least 8 species of carnivorous megadermatid bats including representatives of the Asian genus Megaderma, others that resemble Eurasian taxa, ancestral species of Macroderma, and the oldest fossil record of the still-living species.
- Discovery of species of molossid bats including some of the most plesiomorphic known in the world.
- Discovery of vespertilionid bats including species closely related to European kinds and the oldest known representatives of modern Australian lineages.
- Discovery of the first known mystacinid bats from Australia (present also in the Bullock Ck LF of the NT), taxa that solve the mystery of the origins of these previously uniquely New Zealand bats.
- Discovery of a family of bats with strong affinities to the South American noctilionoids, a group whose origins were otherwise unknown.
Other research programs
In addition to Riversleigh and Murgon, research programs and expeditions are annually conducted to: a, Miocene deposits in the South Island of New Zealand (where the first evidence for terrestrial mammals have been found; ARC Discovery Grant); b, possible Miocene fossil-rich amber deposits in northeastern Queensland (the first amber discovered in Australia; ARC Discovery Grant); c, early Cretaceous deposits from Lightning Ridge which contain Australia's first-known Mesozoic mammals; and d, Plio-Pleistocen