#GOLDEN EGG SECOND EXTINCTION SERIES#

One recent study concluded that the trigger for the Hangenberg event was ultraviolet radiation, penetrating the atmosphere through a break in the ozone layer. An asteroid also struck Earth during this period, leaving behind the 40-mile-wide Siljan crater. Nothing has been found yet to compare with the monstrous eruptions of the later Permian extinction, but some evidence does suggest that volcanism in a large igneous province called the Viluy Traps may have played a role, including, perhaps, via mercury poisoning. “There’s been a lot of searching for a plausible candidate,” Algeo says. Volcanic activity is a perennial suspect in extinction investigations, and scientists have duly scoured the rock record for traces of it in the Devonian extinction. It’s more difficult to say why the oceans suddenly became unbreathable for them. Along with the armored fish, reef-builders like corals and sponges died en masse, as did trilobites, nautilus-like goniatites and many more creatures. It’s likely, then, that one of the major kill mechanisms throughout the Devonian period was asphyxiation. Some of the best evidence is found in the layers of black shale - which form under anoxic conditions - that date to the time. Two, however, stand out: the Kellwasser and Hangenberg events, which occurred in the middle of and at the end of the Devonian period, respectively.Ĭlear-cut answers are rare in the realm of extinction, but researchers broadly agree that both events were accompanied by widespread ocean anoxia, or low oxygen levels. Over the course of millions of years, as many as 10 distinct events raised the loss of biodiversity above the normal background rate, or baseline. In terms of its time scale, “the Devonian extinction is quite different from the others,” says University of Cincinnati geologist Thomas Algeo. This opened ecological niches to a new cast of organisms - no less than, in Coates’ words, “the signature of modern vertebrate life on the planet.” Gasping for Air Annihilation crept in, and slowly swept away the dominant Devonian species.

#GOLDEN EGG SECOND EXTINCTION SERIES#

“A series of crises piled up to affect life on Earth,” says Michael Coates, a biologist at the University of Chicago. (Credit: AuntSpray/Shutterstock)īut for all their might, Dunkleosteus and its kin wouldn’t survive the age that bears their name. The most famous of these mean-mugging beasts, Dunkleosteus, may have grown as long as 30 feet, probably winning it the distinction of largest animal - until the dinosaurs.Īn illustration of the enormous extinct prehistoric fish Dunkleosteus swimming in search of food within a Devonian Sea. At the top of the food chain sat the placoderms, a race of heavily-armored and sometimes massive fish. (Vertebrates hadn’t yet made the leap onto land.) The prehistoric waters teemed not with the likes of tuna, sardines and salmon, but with their bizarre, long-dead predecessors. The extinction began roughly 380 million years ago, midway through the segment of geologic time known as the Devonian period, or the age of fish. Even that paradoxical title seems fitting: The Devonian extinction ravaged Earth on and off for 25 million years, and although it ultimately killed three-quarters of all species, it also cleared the way for a new balance of animal life that endures to this day. If the other great die-offs are short stories of death and destruction, this one is an epic akin to War and Peace. The Devonian, the second of the so-called 'Big Five,” defies this notion. We think of mass extinctions as brief moments of havoc - profoundly devastating but over within a geologic instant.

Golden egg second extinction