After the enormous time span of the Precambrian, lasting 4000 million years, complex life suddenly burst forth in an astonishing array within a few million years. What types were there? And onto what sort of Earth did they evolve?

The span of this chapter covers 191 million years, comprising:

• 54 million years in the Cambrian 542–488 Ma

• 44 million years in the Ordovician 488–444 Ma

• 28 million years in the Silurian 444–416 Ma

• 57 million years in the Devonian 416–359 Ma.

PART OF GONDWANA

For this time, from 542–359 Ma ago, there was still no Australia as we know it. The present Australia was just a segment on the northern edge of Gondwana. The Australian segment did not lie east–west, but north–south, with western and central Australia embedded in the supercontinent, and being eroded. An open ocean lay across what is now eastern Australia.

Gondwana consisted of large onshore areas, huge chains of active volcanoes, with embayments of shallow seas and coral reefs, passing offshore into deep water. A possible modern analogy is the American landmass with the shallow Caribbean Sea and reefs, the volcanic arc of the West Indies, and the deep waters of the Atlantic.

The present landmass that is eastern Australia was not made at that time. There is a line that can be drawn from the present western side of Princess Charlotte Bay through southwestern Queensland and into far northeastern South Australia, with a sharp turn into New South Wales, southeast again to take in Broken Hill, and finally a dogleg west to Kangaroo Island in South Australia.