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Scientists Say The Asteroid That Killed The Dinosaurs Almost Wiped Us Out Too (theweek.com)
HughPickens.com writes: Conventional wisdom states that mammalian diversity emerged from the ashes of the Cretaceous/Tertiary mass extinction event, ultimately giving rise to our own humble species. But Joshua A. Krisch writes at This Week that the asteroid that decimated the dinosaurs also wiped out roughly 93 percent of all mammalian species. "Because mammals did so well after the extinction, we have tended to assume that it didn't hit them as hard," says Nick Longrich. "However our analysis shows that the mammals were hit harder than most groups of animals, such as lizards, turtles, crocodilians, but they proved to be far more adaptable in the aftermath." Mammals survived, multiplied, and ultimately gave rise to human beings.
So what was the great secret that our possum-like ancestors knew that dinosaurs did not? One answer is that early mammals were small enough to survive on insects and dying plants, while large dinosaurs and reptiles required a vast diet of leafy greens and healthy prey that simply weren't available in the lean years, post-impact. So brontosauruses starved to death while prehistoric possums filled their far smaller and less discerning bellies. "Even if large herbivorous dinosaurs had managed to survive the initial meteor strike, they would have had nothing to eat," says Russ Graham, "because most of the earth's above-ground plant material had been destroyed." Other studies have suggested that mammals survived by burrowing underground or living near the water, where they would have been somewhat shielded from the intense heatwaves, post-impact. Studies also suggest that mammals may have been better spread-out around the globe, and so had the freedom to recover independently and evolve with greater diversity. "After this extinction event, there was an explosion of diversity, and it was driven by having different evolutionary experiments going on simultaneously in different locations," Longrich says. "This may have helped drive the recovery. With so many different species evolving in different directions in different parts of the world, evolution was more likely to stumble across new evolutionary paths."
Today's birds are what remains of dinosaurs, at lest the ones with wings that could get to safer ground, or air. The big dinos bit the dust. We came from very nimble and intelligent creatures that grew up and got even smarter, while removing the competition for food. Yeah, we kind of knew this.
At least half of the American voters do! Why are you insulting them?!
Another (main) meaning of "decimate" is "kill, destroy, or remove a large percentage or part of". Who knows exactly how much time it took to eliminate the last dinosaur after the asteroid impact?
Slashdot, fix the reply notifications... You won't get away with it...
I'm not ridiculing individuals, I'm ridiculing patently absurd ideas. Ridiculous ideas deserve to be ridiculed. People should feel an intellectual shame in believing in goblins, fairies and gods.
Please take your argument to Oxford...
Although I suspect you won't get very far with it there.
Il n'y a pas de Planet B.
On the other hand, the Komodo dragon is not very closely related to the dinosaurs. It belongs with snakes, many small lizards and the ancient mosasaurs (mostly marine species) to their own group, the Squamata (scaled reptiles). It is the sister group to the archosaurs, also appearing 250 million years ago.
The whole story is quite complicated and fascinating. The KT-boundary basicly wiped out every animal that was larger than around two feet on land and three feet in the water. This was true for most of the mammals, most of the birds, all of the winged lizards, all marine lizards etc.pp.. And it took some million years for the remaining groups to recover. Birds for instance survived only on an island around Patagonia, all other ancient birds like the Hesperornithes died out.
>I would be quite interested in finding out if there are any fossil remains of mammals and how they fit into the ecosystem with dinosaurs before the big one hit
There are, plenty. The oldest mammal fossils are between 150 and 200 millions years old. Mammals and Dinosaurs coexisted for a very long time. We identify early mammals by their teeth. Mammals alone have precisely interlocking teeth. This came at a price. Sharks and crocodiles can replace lost teeth indefinitely - but when you have precisely interlocking teeth every tooth is a snowflake, and so you can't just sausage-factory out infinite replacements. Mammals therefore only have two sets of teeth - one smaller set that sees them through childhood and a larger set through adulthood. All our dental issues and root cannals began with that.
But it has a catch - to make the first set last through childhood, it had to be bigger than what can fit infancy - so for the first part of their lives mammal babies have no teeth at all. So they needed a new food source for babies. Thus was evolved: milk.
So the teeth are a key clue to whether or not a creature was milk-producing, and it's how we differentiate early mammals from their reptilian contemporaries and close ancestors. The reason the date-span is so long (150-200 million) is that the oldest likely mammal fossil we have is 200-million years old, but many paleontologists believe it should be considered a reptile ancestor of mammals and not a true mammal yet. By 150-milliion years ago though, there were plenty of mammals and they were definitely mammals. These first definite mammals were morganucodontids which were tiny creatures that looked rather like shrews. They probably at seeds and the occasional dinosaur egg and were likely eaten by the smaller predatory dinosaurs in turn. They were however, brainy little guys. Their skull cavity for body mass ratio was far higher than any known dinosaur. They were our ancestors - and the mammalian trait of intelligence was already established.
By the time of the K/T event they had diversified significantly into a number of species. What the study now actually says is that most of those species did not survive K/T - only a small number here and there made it through. And then, as plantlife recovered, there were these massive ecosystem niches ready to be taken advantage off - and no big creatures in the way, and those mammals were perfectly poised to take advantage. You often find the greatest diversity right after mass extinctions. With so many creatures gone, for a while almost any body plan can offer a workable survival advantage - and then as they start to compet with each other, it narrows down again into the winning categories.
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>What about creatures like crocodiles, alligators, and the Komodo dragon which all could pass for dinosaurs?
Could pass for - but aren't. They are different families in the reptile kingdom entirely. Many of whom predated the dinosaurs. Even when dinosaurs were around they were not the *only* large reptilian family - they were in fact just one of four (that we know off). They were, however, the largest LANDLIVING reptiles at the time. The number two spot goes to the Pterosaurs, even though most people only know Pterodactyl who wasn't even the most impressive of that family, and which are constantly filed in with dinosaurs (in every dino movie for one) even though they were not dinosaurs (and very, very distant relatives). There were hardly any aquatic dinosaurs - the oceans then belonged to the Mosasaurs and Icthyosaurs -two families that were both just as diverse as dinosaurs. The ichthyosaurs were essentially reptilian dolphins and whales but they eventually went extinct after being outcompeted by the plesiosaurs - the third major aquatic reptile family.
And all this is still just the highlights package - I mean in the late triassic there were already turtles in the oceans - among them two whale-sized giants that could swallow a modern leatherback without chewing. Imagine a two-tonne turtle. And their descendents are also still with us.
Horse-shoe crabs are the last surviving member of a family that ruled the the oceans some 350-million years ago - long before any of these reptiles. The rise of the reptile predators probably helped along the extinction of every single species in that family - but the horse-shoes survived (and are not crabs), then outlived the great reptiles and continued right into present day - where they now hold the record as the animal that has directly saved more human lives than any other.
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