PHANEROZOIC EON (541-0 Ma)
From Greek phanerós (visible) and zõon (animal).

PALEOZOIC ERA (541-251,902 Ma)
From Greek palaiós (old) and zõon (animal).

CAMBRIAN PERIOD (541-485,4 Ma)
From Cambrian, the Latin name of Wales.

Main events: appearance of the skeleton and development of the eyes.

Lifeforms: "Cambrian Explosion" is when most of today's current phyla appeared and diversified and there was a spectacular development of the eyes. In the oceans, there were a lot of multicellular organisms, many of them with skeleton or shell. The first mollusks, arthropods, brachiopods, echinoderms, foraminifera, graptolites, bryozoans, chordates and fish appeared. On the continents, there were only small microbial colonies.

Paleoenvironment: there were various continental masses and two large oceans. On the margins of various continents, shallow and relatively warm seas, without polar ice caps. The area of the present Pyrenees was in a platform marine environment or deeper.there were various continental masses and two large oceans. On the margins of various continents, shallow and relatively warm seas, without polar ice caps. The area of the present Pyrenees was in a platform marine environment or deeper.

Cobblestones: La Seu grey slate.