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Pikaia & Amphioxus
Darwins Theory ...
R. C. Sprigg
Simon Conway Morris
The 5 Mass Extinctions
The Sixth Extinction
Late Devonian Extinction
When did the mass extinction occur?
408-360 million years ago
Why did the mass extinction occur?
The cause is unknown. But scientists have speculated two theories:
: glaciation in Gondwana (when South America, Africa, Antartica, India, Arabia, Australia was still one continent) was specualted to be a possible cause of this mass extinction. Evidence suggests that the extinction had a greater impact on the warm-water marine lives than the cool-water marine lives. This leads to many paleontologists hypothesising the causation of the extinction to be global cooling, glaciation over the south-pole region. This is a similar cause to the Ordovician mass extinction's.
Samples of glacial deposit was found in South America which at the time was still part of Gondwana (in the south-pole region).
What was the evolutionary significance of this mass extinction?
The late Devonian Extinction killed 22 percent of marine families and 57 percent of marine genera. The extinction had the severest impact on the warm-water marine community, majorly the reef-builders. Although most reef-builder species did not go extinct, yet they remain rare until they evolve into the scleractinian corals (the modern corals that we see today) in the mesozoic period (248-65 million years ago). Other affected species include the jawless fish, Brachiopods (clam-like invertebrates), Conodonts (minute, tooth-shaped swimming invertebrates), and placoderms (armored-jawed fish).
Fossil of a devonian reef-builder Devonian reefs
Which organisms that remain today survived this mass extinction? Which one? Why? Have they evolved any further?
Mentioned above, the major reef-builders: the stromatoporoids, the rugose and the tabulate corals survived the mass extinction, but remained as uncommon species until they evolved into the modern corals in the mesozoic period after around 150 million years.
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