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Australian World Heritage Fossil Sites Celebrate 20 Years

By John Long

The renowned fossil sites at Riversleigh and Naracoorte celebrate a milestone this month.

This month celebrates the 20th anniversary of the proclamation of Australia’s joint nomination of the World Heritage Fossil Mammal Sites at Riversleigh in Queensland and Naracoorte in South Australia. The nomination came jointly as both sites together provide a deep time perspective on how Australia’s unique modern mammal fauna came into existence.

While some Riversleigh mammals are vaguely recognisable, like some of the early kangaroos, possums and koalas, others represent bizarre evolutionary experiments, like the Yalkiparodon. Riversleigh sites include a wider range of ancient fauna and flora, including perfectly preserved invertebrates such as

16 million-year-old ostracods with sperm preserved (Fossil Files, July 2014). Riversleigh provides a stunning window into our past, showing that the diversity of Australia’s mammals faunas was much higher around 20 million years ago than it is today.

Riversleigh’s main story is all about the early beginnings of Australia’s mammal faunas from 25–12 million years ago in particular. From such trends and evolutionary patterns we can make profound inferences about the nature of today’s faunas and where they are heading.

I asked Prof Michael Archer, who has been long involved with the site’s discovery and research, why the site is so important. He said:

Since beginning our research program at Riversleigh in 1976, and seeing it listed as part of a World Heritage property along with Naracoorte Caves in 1994, understanding about the Riversleigh record in a global as well as national context has grown enormously. There are more than 100 researchers in 25 institutions and 11 countries who have been part of the overall research program. With over 250 faunal assemblages known (many now radiometrically dated), hundreds of new species, genera, families and even an order of mammals evolving over the last 24 million years, we are rapidly developing a solid foundation for continental biocorrelation of mid to late Cenozoic vertebrate assemblages across Australia. Because more fossil deposits and new taxa are being found each year, some well beyond the current World Heritage boundaries, significant discoveries at Riversleigh will undoubtedly continue for many decades if not centuries to come.”

Sir David Attenborough has said that “Riversleigh is one of the four most important fossil deposits in the world”.

The Naracoorte fossil caves provides a series of detailed snapshot of Australian fauna evolving over the past half a million years through a series of very well-dated sites. These demonstrate how the modern fauna survived through the last glacial cycles.

The high diversity and abundance of very well-preserved fossil bones is Naracoorte’s strong point. It’s like the Australian equivalent of the La Brea tar pits, where millions of bones have already been recovered and conserved. Such large volumes of quantitative data are very important for determining the abundances of certain species through time, as well as gauging their resilience to changing environmental extremes.

Prof Rod Wells and colleague Grant Gartrell discovered the fossil-rich cave in 1969. At the time, Rod said:

I swept the acetylene lamp around and there were all these funny saw toothed patterns that looked like bits of cave decoration that had fallen from the ceiling. I then realized that I was actually looking at the tooth rows of skulls. It’s a paleontologist’s dream to find a site as rich as that. We now know that the deposits of the caves at Naracoorte extend back an almost continuous record for 500,000 years. That was before even Homo sapiens were around let alone before humans entered Australia.

Australia has several other highly significant fossil sites that tick every box for a future World Heritage site, yet for various reasons they haven’t yet garnered the necessary state support for their nominations. Ediacara in the Flinders Ranges of South Australia is home to the oldest well-preserved assemblage of multicellular animals on the planet. Gogo, in the north of Western Australia, has the world’s best-preserved diverse assemblage of early fishes, and it also tells the story of how complex sexual reproduction first began.

Perhaps getting these and several other significant Australian fossil sites on the World Heritage List is something we can aim for in the next 20 years.

John Long is Strategic Professor in Palaeontology at Flinders University.