- en.wikipedia.org CambrianThe term Cambrian for the oldest period of the Paleozoic was officially agreed in 1960, at the 21st International Geological Congress.
- pethealthoasis.pages.dev posts/cambrian-period-…The Cambrian Explosion of Life#. Before the Cambrian, life on earth consisted mainly of single-celled organisms, a handful of multicellular organisms, and algae.
- meteorologiaenred.com en/Cambrian.htmlThat is, no land pole was covered with ice. In turn, the Cambrian period is divided into three eras: Lower Cambrian, Middle Cambrian and Upper Cambrian.
- geologypage.com 2014/02/cambrian-period.htmlThe Cambrian is the first geological period of the Paleozoic Era, lasting from 541.0 ± 1.0 to 485.4 ± 1.9 million years ago (mya) and is succeeded by the Ordovician.
- ucmp.berkeley.edu cambrian/cambrian.phpA few mineralized animal fossils, including sponge spicules and probable worm tubes, are known from the Ediacaran Period immediately preceding the Cambrian.
- http://scotese.com newpage12.htmCambrian: the beginning of the Paleozoic Era. ... Animals with hard-shells appeared in great numbers for the first time during the Cambrian.
- britannica.com Fossils & Geologic TimeCambrian Period, earliest time division of the Paleozoic Era and Phanerozoic Eon, lasting from 538.8 million to 485.4 million years ago.
- newworldencyclopedia.org entry/CambrianThe Cambrian period is the first or earliest of 6 periods making up the Paleozoic era within the Phanerozoic eon, which includes the present time.
- nationalgeographic.com science/article/cambrianThe Cambrian period, part of the Paleozoic era, produced the most intense burst of evolution ever known.