What is Cambrian?
[[File:Marrella (fossil).png|thumb| 220px| This ''[[Marrella]]'' specimen shows how clear and detailed the [[fossil]]s are from the [[Burgess Shale]] [[lagerstätte]].]] [[File:DickinsoniaCostata.jpg|220px|thumb|right|''[[Dickinsonia]]'', an [[Ediacaran]] animal with a quilted appearance.]] [[File:Olenoides serratus oblique with antennas.jpg|thumb|220px| A fossilized [[trilobite]]. This specimen of ''Olenoides serratus'', from the [[Burgess shale]], preserves 'soft parts'&nbsp;– the antennae and legs. ]] The '''Cambrian''' is the first geological period of the [[Palaeozoic]] [[era]] and the [[Phanerozoic]] [[eon]]. It lasted from 541 million years ago to 485.4 million years ago.<ref>[http://www.stratigraphy.org/ICSchart/ChronostratChart2013-01.pdf International Commission on Stratigraphy]</ref> Before it came the [[Ediacaran]], and after it the [[Ordovician]]. Biologists have learnt quite a lot about the soft parts of Cambrian animals. This is because [[Lagerstatten|places]] have been found where soft parts of organisms are preserved as well as their more resistant shells. This means our understanding of the Cambrian [[biota]] is better than that of some later periods. Life on Earth changed greatly during the Cambrian period. Before the Cambrian, life was mostly small and simple. Complex organisms ([[metazoa]]) [[evolved]] during the [[Proterozoic]] era. But during the Cambrian period, some organisms used [[carbonate]] [[mineral]]s for [[shell]]s, so they had hard parts which could become fossils. There were many different kinds of life during the Cambrian period. This increase in the diversity of lifeforms was relatively rapid, and is called the [[Cambrian explosion]]. This [[adaptive radiation]] produced the first members of the main groups of animals, called [[phyla]]. Almost all of this new life was in the oceans. There was little life on land except a layer of [[microbe]]s. There were shallow seas near several continents, because a [[supercontinent]] called [[Pannotia]] had broken into smaller pieces. The