Mike Archer
Mike Archer

Professor Mike Archer AM: Research

Synopsis of recent palaeontological research

Over 100 researchers from 28 institutions and 11 countries (France, Germany, Czechoslovakia, England, U.S.A., China, Canada, Argentina, New Zealand & Australia) are collaborating in the analysis of Riversleigh, Murgon and New Zealand resources which includes the fossil records of more than 83 families of Australian animals and plants. A further and different list of collaborators are involved in the work on the Miocene amber project.

Considering outcomes from two of the largest projects—Riversleigh and Murgon, the following list of discoveries is representative.

Murgon Project

Each year, the Tingamarra Local Fauna (LF) from the Murgon deposit in southeastern Queensland has grown with addition of new mammals, birds, amphibians and reptiles. Tingamarra material has been the subject of three PhD theses and many publications with more in preparation. International research projects on Murgon materials involve colleagues from France, Argentina, England and Czechoslovakia. Normally at least one expedition a year is organised from UNSW. At the current rate, about 50 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.

Main points of general significance that have developed from Murgon research

  1. Although illite from the deposit was dated (K/Ar) by AMDEL as >54.6 +/- 0.5 mybp, controversy focuses on this date; accumulating palaeontological evidence, however, supports the original interpretation.
  2. This is the only marsupial-bearing deposit from the Australian portion of Gondwana older than 24 Ma.
  3. 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-split’ Cainozoic biota.
  4. 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.

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. Since 2008, radiometric dating has enabled construction of a national framework for biocorrelation of Australian mid to late Cenozoic vertebrate fossil deposits. 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 ‘Australian Fossil Mammals: Riversleigh and Naracoorte’ (Australia’s only World Heritage fossil property). Many PhD and Honours theses, and hundreds of papers have been produced based on the fossils, rocks and palaeoecology of Riversleigh.

Main points of general significance arising from research at Riversleigh

  1. Riversleigh’s Cainozoic fossil deposits span the late Oligocene to Holocene, with gaps of uncertain duration.
  2. This record includes one of (if not the) longest for rainforest communities anywhere in Meganesia.
  3. It includes palaeocommunities 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.
  4. 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).
  5. 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.
  6. 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/icehouse shifts.
  7. Riversleigh's record spans the late Miocene decline in closed forests, their replacement by open forests and (by Pliocene/Pleistocene time) development of grasslands.
  8. 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.
  9. Riversleigh has produced the first fossil records for many genera, families and even orders (e.g., marsupial moles) with still-living species.
  10. 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).
  11. 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.
  12. Preliminary ecological analyses demonstrate that even Riversleigh’s most diverse communities appear to represent single (not mixed) communities.
  13. 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). 
  14. 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.

Other palaeontological research programs

In addition to Riversleigh and Murgon, our 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; d, Plio-Pleistocene deposits in the Leichhardt River region, northern Queensland.