The
Cambrian ( or ) is the first
geological period of the
Paleozoic Era, lasting from to million years ago (mya) and is succeeded by the
Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established (as “Cambrian series”) by
Adam Sedgwick, who named it after
Cambria, the
Latinised form of
Cymru, the
Welsh name for
Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of
lagerstätte sedimentary deposits. These are sites of exceptional preservation, where "soft" parts of organisms are preserved as well as their more resistant shells. This means that our understanding of the Cambrian biology surpasses that of some later periods.