Reefs Recovered Faster After Mass Extinction Than First Thought (http://www.sciencedaily.com/releases/2011/09/110930102802.htm)
QuoteScienceDaily (Sep. 30, 2011) — Metazoan-dominated reefs only took 1.5 million years to recover after the largest species extinction 252 million years ago, an international research team including paleontologists from the University of Zurich has established based on fossils from the southwestern United States.
Harsh living conditions caused by major fluctuations in the carbon content and sea levels, overacidification and oxygen deficiency in the seas triggered the largest mass extinction of all time at the end of the Permian era 252 million years ago. Life on Earth was also anything but easy after the obliteration of over 90 percent of all species: Throughout the entire Early Triassic era, metazoan-dominated reefs were replaced by microbial deposits. Researchers had always assumed it took Earth as long as five million years to recover from this species collapse.
Now, however, an international team, including the paleontologist Hugo Bucher from the University of Zurich and his team of researchers, has shown that reefs already existed again in the southwest of what is now the USA 1.5 million years after the mass extinction. These were dominated by metazoan organisms such as sponges, serpulids and other living creatures, the researchers report in Nature Geoscience...
Interesting article. All 'corals' we have today did not exist before the mass extinction at the end of the Permian era. So all corals are now less than 250 million years old and these creatures established themselves in sufficient quantities to be fossilised in 1.5 million years after the extinction event. Just goes to show how quickly (in geological terms) ecological niches can be filled.