Finding Fossils

One of the most significant finds from Murgon, confirming the Gondwanan connection was the discovery of the placental Condylarth Tingamarra porterorum. This internationally significant fossil is Australia's oldest placental land mammal. Scientists once thought that non-flying placental mammals first colonised Australia in the Late Miocene/Early Pliocene when they first appear in the fossil record. However now it seems that both placentals and marsupials lived in Australia in the early Tertiary, although only marsupials persisted.

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Palaeontologists excavating this site first remove tonnes of overburden with a backhoe. The fossil-bearing green clay is carefully excavated and put into bags to be transported to the laboratory for preparation. Larger fossils, such as large bones and turtle shells, are wrapped in plaster for the journey to the lab. In the laboratory the clay is dried in ovens and then washed through sieves to retrieve the tiny fossil bones and teeth.

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Palaeontologists excavating at a fossil quarry at Murgon. Brushes and fine tools are used to remove clay from around fossil bones such as this crocodile skull (far right). [Photos: Henk Godthelp].

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Why is Murgon Important?

The Murgon Fossil Site is located near Kingaroy in south-east Queensland. The site is significant as the only site in Australia that records a diverse vertebrate fauna dating from the early Tertiary Period (55 million years before present), approximately ten million years after the extinction of the dinosaurs. The site includes some outstanding fossil records, including the world's oldest fossil songbirds, the oldest fossil marsupial remains in Australia, a placental mammal (Condylarth), one of the world's oldest bats, the only known fossil remains of leiopelmatid frogs, and the only known fossils of salamanders in Australia.

It is this combination of age and vertebrate faunal diversity, as well as its outstanding earliest fossil records of several taxa that make the Murgon Fossil Site significant in the international context.

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At the end of the Cretaceous Period, 65 million years ago, life on earth was affected by massive extinctions. Of the dinosaurs only a single lineage, the theropods, survived as modern birds. This gave mammals an opportunity to diversify and become a more successful form of vertebrate life. After 10 million years, in the Early Eocene epoch, mammals across the world were evolving into new and fascinating forms. The Australian continent was evolving too, still joined with Antarctica and South America as the supercontinent Gondwana. From the 54.6 million-year-old clays at Murgon comes evidence of this ancient association in the form of a unique assemblage of fossil animals.

Murgon swamp 54.7 million years ago. The cavy-like Thylacotinga bartholomaii approaches the waters' edge with its young. At left is a microbiotheriid marsupial, the closest relatives of this primitive marsupial are known only from South America. On the right is the primitive Condylarth Tingamarra porterorum, an animal that changed scientific understanding of Australia's fossil mammal history. In the trees are the world's oldest known songbirds. In the background Australia's oldest fossil bandicoot drinks as the oldest known Australian fossil bat, Australonycteris clarkae, flies overhead. [Reconstruction: Anne Musser]

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Murgon Fossil time Period

Early Eocene 54.6 million years ago
Time line and position of the continents during formation of the Murgon fossil deposits.
Still connected to Antarctica and South America by a land bridge, the Australian continent (red) was moving northward. The Eocene Epoch lasted from 55 million years ago to 34 million years ago.

Fossil discovery

The unexpected discovery of this tooth was a historical find. This is a molar of Tingamarra porterorum, a primitive placental mammal. It was surprising to find placental mammals of this age in Australia. [Photo: Henk Godthelp]

Although discovered in the 1930s, it was in the 1980s when palaeontologists Henk Godthelp and Mike Archer recognised the significance of the lake sediments at Murgon in southeastern Queensland which yield Australia's oldest known Tertiary mammals. The ancient swampy environment was home to soft-shelled turtles, Australia's oldest known frogs and swamp crocodiles of the genus Kambara. Among the trees flew Australia's oldest known bat, Australonycteris clarkae, and birds that have been recognised as the world's earliest known songbirds, raising the possibility that this group of birds evolved in Australia.

The primitive, almost unrecognisable ancestors of Australia's modern mammal fauna are present such as Australia's oldest known bandicoot, a strange marsupial omnivoreThylacotinga bartholomaii, and several marsupial insectivores. Evidence of Australia's Gondwanan links with South America comes in the forms of fossils of Alamitophis sp., a madstoiid snake of the same kind as Patagonian forms and a microbiotheriid marsupial - microbiotheriids are a group of marsupials otherwise known only from South America.

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Scientific papers about Riversleigh discoveries