Great Ordovician Biodiversification Event

[9] Possible causes include an increase in marine oxygen content,[10] changes in palaeogeography or tectonic activity,[11] a modified nutrient supply,[12] or global cooling.

[23] The volcanic activity that created the Flat Landing Brook Formation in New Brunswick, Canada may have caused rapid climatic cooling and biodiversification.

[10] Furthermore, Ordovician biodiversification pulses were closely linked to terminations of positive carbon isotope excursions, which are characteristic of anoxia, suggesting that diversification occurred in concert with increasing oxygen content.

[25] After the Steptoean positive carbon isotope excursion about 500 million years ago, the extinction in the ocean would have opened up new niches for photosynthetic plankton, who would absorb CO2 from the atmosphere and release large amount of oxygen.

[27] Another alternative is that the breakup of an asteroid led to the Earth being consistently pummelled by meteorites,[3] although the proposed Ordovician meteor event happened at 467.5±0.28 million years ago.

[28][29] Another effect of a collision between two asteroids, possibly beyond the orbit of Mars, is a reduction in sunlight reaching the Earth's surface due to the vast dust clouds created.

[12] As with the Cambrian Explosion, it is likely that environmental changes drove the diversification of plankton, which permitted an increase in diversity and abundance of plankton-feeding lifeforms, including suspension feeders on the sea floor, and nektonic organisms in the water column.

[3] The GOBE is considered to be one of the most potent speciation events of the Phanerozoic era, increasing global diversity severalfold and leading to the establishment of the Palaeozoic evolutionary fauna.

[39] The planktonic realm was invaded as never before, with several invertebrate lineages colonising the open waters and initiating new food chains at the end of the Cambrian into the early Ordovician.

[1] Recent work has suggested that the Cambrian Explosion and GOBE, rather than being two distinct events, represented one continual evolutionary radiation of marine life occurring over the entire Early Palaeozoic.

[46] Analysis of the Guole Konservat-Lagerstätte and other sites in South China suggests the Furongian Gap did not exist, instead portraying this interval as one of rapid biotic turnovers.

Possible line of meteors (on the modern globe) associated with the Middle Ordovician meteor event 467.5±0.28 million years ago. Although this is suggestive of a single large meteorite shower, the exact alignment of continental plates 470 million years ago is unknown and the exact timing of meteors is also unknown.
Atrypid brachiopods ( Zygospira modesta ) preserved in their original positions on a trepostome bryozoan ; Cincinnatian (Upper Ordovician) of southeastern Indiana.
Reconstruction of the Fezouata Biota, featuring roughly 50 different species. The largest animal, Aegirocassis benmoulai (just over 2 metres in length), is depicted in a pair swimming just above the seafloor. [ 43 ] This giant radiodont is one of the earliest "giant" filter feeders, with frontal appendages bearing baleen -like spines. These adaptations were likely influenced by the proliferation of plankton in the early Ordovician.