LIFE × EVOLUTION

The Ordovician Biodiversification

~485 to 443 million years ago

Phanerozoic · Paleozoic · Ordovician

The Ordovician biodiversification is the interval, between 485 and 443 million years ago, in which the number of marine families, groups of related species, multiplied several times over.

The Great Ordovician Biodiversification Event, commonly abbreviated GOBE, is the interval of the Ordovician period in which marine families became several times more numerous. The body plans, the basic layouts of animal bodies, were established in the Cambrian, the period before. In the Ordovician, animals built on these plans populated the sea. Animals replaced microbes as the builders of reefs. The plankton, the organisms that drift in open water, acquired predators of its own and became an ecosystem in itself. Life, which had been spread across the seafloor, came to occupy the pelagic realm, the volume of open water above the seafloor.

Why it matters

The present-day ocean, with its plankton, its pelagic realm and its animal reefs, dates from the Ordovician and not from the Cambrian. The diversification extends across the whole duration of the Ordovician, group by group and region by region. This is why specialists are divided on whether a single name, that of one event, suits it.

Dating & uncertainty

Whether the Ordovician biodiversification is one event or several remains open. Diversity rises at different moments in different groups and different regions. Some specialists hold that the single global event is an artefact, an appearance created by the method: the pooling into one count of databases that were sampled unevenly.

Earth history as one day

21:26:102 h 34 min before midnight

if Earth’s 4.54 billion years were compressed into a single day