Ordovician [ˈɔːdəvɪʃɪən] (1 janv. 434248009 av. J.-C. – 1 janv. 41024800 av. J.-C.)

Description:

First coral reefs. Primitive fish evolve. The Ordovician Period ushered in significant changes in plate tectonics, climate, and biological systems. As a result, continents were flooded to an unprecedented level, with North America almost entirely underwater at times. The Ordovician Period was also characterized by the intense diversification (an increase in the number of species) of marine animal life.