when did the late devonian mass extinction occur
Late Devonian extinction Although it is clear a massive loss of biodiversity occurred in the Later Devonian, the extent of time during which these events took place is uncertain, with estimates ranging from 500,000 to 25 million years, extending from the mid-Givetian to the end-Famennian.[5][citation needed] Nor is it clear whether it concerned two sharp mass extinctions or a series of smaller extinctions, though the latest research suggests multiple causes and a series of distinct extinction pulses through an interval of some three million years.[6] Some consider the extinction to be as many as seven distinct events, spread over about 25 million years, with notable extinctions at the ends of the Givetian, Frasnian, and Famennian stages.[7]
Evolutionary history of plants Evidence for the appearance of the first land plants occurs in the Ordovician, around 450 million years ago, in the form of fossil spores.[7] Land plants began to diversify in the Late Silurian, from around 430 million years ago, and the results of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage from the Rhynie chert. This chert, formed in volcanic hot springs, preserved several species of early plants in cellular detail by petrification.[8]