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]
Devonian Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fish". The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environment. The ancestors of all four-limbed vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral and pelvic fins gradually evolved into legs.[10] In the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician.