IT TAKES an age for events to happen in geology – and that includes naming new geological time periods. Around 580 million years after the first multicellular animals appeared in the fossil record, they have finally been assigned their own period, called the Ediacaran. It is the first new period designated for 120 years, and joins the Permian, Jurassic and Triassic among others.
Named after the hills in South Australia where geologist Reg Sprigg discovered an abundance of these marine fossils in 1946, the Ediacaran period was formally announced on 13 May following a meeting of the International Commission on Stratigraphy.
Previously, and unofficially, also known as the Vendian, the Ediacaran stretches from 600 million to 540 million years ago – shortly after its distinctive animals abruptly vanished. They were soft-bodied species, some with quilted bodies, a bit like inflatable air beds. After the Ediacaran came the Cambrian, with its own forms of animal life.
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Ediacaran animal fossils have been discovered all over the world, in Namibia, England, Russia and Newfoundland, as well as Australia. But the layered rocks of the Ediacara Hills have been designated the site of the reference examples for defining the start of the period, which is also the first to be based on rocks in the southern hemisphere.