"Mass extinctions don’t come out of the blue..." Topic

… — and we're seeing some of the signs today.

"An incoming mass extinction isn't as hard to spot as we'd believed, new research suggests.

Paleobiologists from the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) say that the build-up to the largest mass extinction event ever recorded was a lot less inconspicuous than anyone assumed. Armed with this knowledge, they also make a worrying remark: some of the tell-tale signs are unfolding today.

Mass extinctions are like really deep economic crises, but for life — which is why such events are also referred to as ‘biotic crises'. They're rare, dramatic events, reaping life with terrifying efficiency: the ‘tamest' mass extinctions cull around 70% to 75% of all species. The largest such event we know of, the Permian-Triassic extinction event, claimed an estimated 83% of all genera and 90% to 96% of all species. Such is their effect that geologists actually use these events as separators between whole geological eras…."
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Amicalement
Armand

Giant asteroids hit the dinos out of the blue. They had no clue until the last minutes.

They should have evolved and invented observatories and telescopes if they wanted to see early on what was headed their way. :)

Dan
PS. Maybe they had a small post apocalyptic cult that prepped for it. Who knows?

The thing is Dan that Dinosaurs were getting muscled out by mammals for a few million years prior to the asteroid. The asteroid was nearly the Coup de grâce.

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But it did come out of the blue. Or, actually, out of the black.

Dan

Oh, man. I must have misheard my teachers in school. I thought they said dinosaurs died off because of a huge hemorrhoid.

Martin, to be fair this is a new theory championed by the article's author. Some things said here are contestable.

"Indeed, climates at this time were cooling. And because dinosaurs relied on the external environment to maintain their body temperatures, this would have hurt them."

That presupposes that the dinosaurs had the same poikilothermic regulation as modern reptiles. I remember Jack Horner being asked if dinosaurs were cold blooded. His answer was some were, some weren't, some were a combination, and some had thermal regulation that is still unknown to us. I think a large segment of dinosaurs had a type of thermal regulation more similar to modern avians, with proto-feathers used for heat retention. This came well before flight.

I raise an eyebrow when people say, "dinosaurs were in decline" as if all dinosaurs fit in some monoblock group. The author goes on to admit that certain types of ornithischians (bird hipped dinosaurs) were actually gaining in population. I think the evidence shows that the smaller theropods were also doing quite well. So some types of dinosaurs were in decline, some were stable and some were flourishing. That's to be expected for a period of about 80 million years, and I doubt that's unique to the Cretaceous. Possibly the large well know dinosaurs, such as T. Rex, were in decline. But wouldn't that be hard to tell? How many apex predators would there be to notice such a trend?

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Same with the mammals, which may have been around in the Triassic period. I was always told that mammals were small night-time tree shrew-like creatures that exploited the eco-niches well away from the dinosaurs domain. Turns out that's not totally true. There have been recent finds of (modestly) large mammals that hunted small and juvenile dinosaurs. Mammals are not a monoblock either.

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While it is quite possible that mammals were also in the ascendency I am not sure the author has made a great case for that. Surely, after the K-P event the ensuing "nuclear winter" would have selected for ectothermic and homeothermic individuals. One wonders after reading the article, how did reptiles, snakes and crocodiles survive to today?

Just being ornery this morning.

Oh, man. I must have misheard my teachers in school. I thought they said dinosaurs died off because of a huge hemorrhoid.

Lol.

That's what happens when you sit in the back of the class, flirt with the girls, and don't always pay attention.

Dan, love that first cartoon. Are the "antediluvians" supposed to be dinosaurs? They look like over weight cats with spikes and kyphosis of the spine. And check out the size of the duck bill!

To get back to the original topic. The biggest extinction event ever was the P-T event (Permian-Triassic) about 251 mya. There are no end of causes to this event, as a good Wiki entry shows:

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Here's a relatively new one. An archaea by the name of Methanosarcina mutated and could now metabolize acetate into methane. The resulting rapid rise in methane and CO2 killed everything off. Studies of carbon isotopes and nickel utilization (needed for the coenzymes in the metabolism) seems to bear this out.

Damned little bugs!

An abstract of the PNAS article:

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A write up in Science Daily ends with:

"While no single line of evidence can prove exactly what happened in this ancient die-off, says Rothman, who is also director of MIT's Lorenz Center, "the cumulative impact of all these things is much more powerful than any one individually." While it doesn't conclusively prove that the microbes did it, it does rule out some alternative theories, and makes a strong and consistent case, he says."

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(smile)

Amicalement
Armand

Bowman: "And check out the size of the duck bill!"

Maybe they already suspected or knew about other gharial-like jaws, like those of sarcosuchus. :)

Dan