10 December 2015

10. Riversleigh

Nimbacinus dicksoni, a dasyuromorph from the Oligo-Miocene of Riversleigh
Queensland Museum/University of New South Wales
Location: Queensland, Australia
Formation: Numerous
Age: Oligocene-Holocene (25-0 Ma)

Most of the sites included in the Lagerstättenadventskalendar thus far have been from the Northern Hemisphere, in large part because sites in Europe and North America are numerous and have been extensively studied for long periods of time.  However, global climate change, by definition, affects the entire globe and there are sites on the southern continents that document how organisms and ecosystems there were influenced by changing climate.  Perhaps the most significant of these, Australia's Riversleigh is not one site but a series of several in the northwest corner of Queensland.  Riversleigh is remarkable not only because of its location but because it records a history of environmental change encompassing everything from the Oligocene to the present day.  From a preservational standpoint, the most impressive of Riversleigh's fossils are the three-dimensionally preserved arthropods from the Miocene Upper Site, but the most abundant and best-studied of Riversleigh's fossils are its vertebrates.  These include such stars of the Australian fauna as giant dromornithid birds, crocodiles, egg-laying monotreme mammals, and, of course, marsupials.  Everything from (relatively) familiar animals such as koalas and rhino-sized diprotodonts to obscure creatures such as "thingodonts" and tapir- (or possibly sloth-) like palorchestids has been found at Riversleigh.  Of particular interest to me, Riversleigh fossils account for much of what we know about the evolution of the three major groups of Australian carnivorous marsupials: dasyuromorphs (the group that includes Tasmanian devils and most other modern Australian predators), thylacoleonids (the marsupial lions), and propleopines (carnivorous kangaroos!).  Taken as a whole, these fossils and the rocks in which they are preserved tell a long-term story of environmental change from dense rainforest in the Oligocene and Early Miocene to cooler forests in the later Miocene to drier, more open woodland in the Pliocene to the shrubland that characterizes the region today.  No series of sites has provided as much insight into the evolution of Australia's unique fauna and ecosystems as has Riversleigh, and there are few localities anywhere that so clearly tell the story of climatic cooling and drying that characterizes the post-Eocene world.

Visit: The Riversleigh sites have been inscribed as a World Heritage Site and are preserved in Boodjamulla National Park in Queensland.
Fossils: The Queensland Museum in Brisbane is the official repository for Riversleigh fossils, but relatively few are on display there.  This is in large part due to much of the material still being the subject of active research at several institutions across Australia.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is!  It's written by Mike Archer, the leading authority on Riversleigh, and his colleagues at the University of New South Wales and, besides being full of gorgeous reconstructions and photos, is an excellent read.

This post is part of my 2015 Paleontology Advent Calendar, a series of vignettes on lagerstätten - sites of exceptional fossil preservation - that document changes in climate and environments through the Cenozoic.  You can see the other posts here.

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