Australia: The Land Where Time Began

A biography of the Australian continent 

Emu Bay Shale                 see Emu Bay Fossils

Emu Bay, Kangaroo Island, South Australia

Lower Cambrian Shale               

The Lower Cambrian Emu Bay shale has been known for some time for well preserved specimens of the trilobites Redlichia takooensis & Hsuepsis bilobata. It differs from other Burgess-Shale-type biotas in that it is believed to result from relatively shallow water deposition, as opposed to the deeper water deposition of the other biotas of this type.  The most notable difference between the Emu Bay assemblage and the other examples of this biota is the extensive mineralisation of labile soft tissue. Emu Bay remains are notable as the oldest known phosphatised muscle tissue and the first so far reported from the Cambrian. This mineralisation is rarely found  in other Burgess-Shale type deposits. 

It is also the only known Australian site of a Burgess-Shale-type biota. The Emu Bay fauna differs from the other known Burges Shale-type faunas, the older upper Atdabanian Chengjiang Fauna of China, and the younger Middle Cambrian Burgess Shale.

The type section of the Emu Bay Shale outcrops on the east side of Emu Bay. The assemblage is comprised of a number of organisms, among them Hsuaspis, Redlichia, hyolithids, brachiopods, and the scleritome-bearing Chancelloria.

The Big Gully deposit contains soft-bodied fossils in addition to the trilobites, including the giant predator Anomalocaris, Isoxys, Tuzoia,  Palaeoscolex (presumed to be a worm), the problematic Myoscolex, and a number of rarer forms. A few specimens of Redlichia have been found to have antennae.

The Emu Bay deposit was previously believed to be of late Early Cambrian age, but this date has been re-assessed as a result of the realisation that it is probably equivalent to the Early Cambrian Tsanglangpuian in the China. Contemporary South Australian faunas have been correlated with the Botomian of Siberia.

The Fauna

A new species of Anomalocaris, A.briggsi,  is endemic in the Emu Bay deposit

Links

1. The Emu Bay Fauna - Catalyst
2. Fossils reveal rapid evolution in ancient eyes
3. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia
4. Emu Bay - Google Maps

Sources & Further reading

1. Mikhail A. Fedonkin, James G. Gehling, Kathleen Grey, Guy M. Narbonne, Patricia Vickers-Rich, The Rise of Animals, Evolution and Diversification of the Kingdom Animalia, Johns Hopkins University Press, Baltimore, 20