living Fossils

For most history, Tasmania was part of Gondwana and life was continuous with that of adjacent regions. Australia became isolated 33.5 million years ago, and Tasmania when Bass Strait formed about 20 million years ago. Much of Tasmania's alpine vegetation is a fossil flora, once contiguous with that of Antarctica, now extinct. Tasmania then became home to several 'living fossils'. The Creeping or Strawberry Pine (Microcachrys tetragona), endemic to Tasmania, was once widespread and common through Australasia and Gondwana. It probably changed little since the Early Jurassic, some 190 million years ago and thus ranks as an outstanding example. Neotrigonia (Brooch shell) survives as two species around Tasmania, and these and a few others occur only around Australia. They are found occasionally on sandy beaches but thrive at 3060 metre depth. They are remnants of important bivalves, globally very diverse and abundant throughout the Mesozoic and thought to disappear simultaneously with dinosaurs. Its ancestor Eotrigonia occurs as a fossil in Miocene (22 million years) sediments at Fossil Bluff, Wynyard.

Anaspides (Mountain Shrimp) is an arthropod up to 4050 mm long, living in mountain lakes. It is a large, distinct member of the Syncarida, freshwater arthropods found in South America, New Zealand, other parts of eastern Australia, but the only family that can be regarded as living fossils occurs in Tasmania, a residue of Gondwana biology. Syncarids were marine during their early history but by 220 million years, fossils in lake sediments from New South Wales were virtually identical to modern Anaspides tasmaniae.

Further reading: N Eldredge & S Stanley, Living fossils, New York, 1984.

Patrick Quilty