Dinosaurs fell victim to perfect storm of events, study show

[cronus]

http://www.eurekalert.org/pub_releases/ ... 072414.php

Dinosaurs fell victim to perfect storm of events, study shows

Dinosaurs might have survived the asteroid strike that wiped them out if it had taken place slightly earlier or later in history, scientists say.

A fresh study using up-to-date fossil records and improved analytical tools has helped palaeontologists to build a new narrative of the prehistoric creatures' demise, some 66 million years ago.

They found that in the few million years before a 10km-wide asteroid struck what is now Mexico, Earth was experiencing environmental upheaval. This included extensive volcanic activity, changing sea levels and varying temperatures.

At this time, the dinosaurs' food chain was weakened by a lack of diversity among the large plant-eating dinosaurs on which others preyed. This was probably because of changes in the climate and environment.

This created a perfect storm in which dinosaurs were vulnerable and unlikely to survive the aftermath of the asteroid strike.

The impact would have caused tsunamis, earthquakes, wildfires, sudden temperature swings and other environmental changes. As food chains collapsed, this would have wiped out the dinosaur kingdom one species after another. The only dinosaurs to survive were those who could fly, which evolved to become the birds of today.

Researchers suggest that if the asteroid had struck a few million years earlier, when the range of dinosaur species was more diverse and food chains were more robust, or later, when new species had time to evolve, then they very likely would have survived.

(continued)

[klr]

I kinda figured this would be your kind of thread.

[cronus]

I kinda figured this would be your kind of thread.

[Blind groper]

I read that report also. My skepticism kicked in. Geological dating is not terribly precise, and there is a large error factor. All that is needed is for that error to be such that the volcanoes and so on happened after the asteroid, not before, and the picture changes dramatically.

There is a school of thought among geologists who believe that meteor or asteroid impacts can cause the subsequent volcanoes and earthquakes etc.

So, if that dating is wrong, by a small amount, we get a picture of an asteroid impact followed by earthquakes and volcanoes. The asteroid may not have killed all the dinosaurs at the time of impact, but the after effects of the asteroid do.

[cronus]

With the decline already in progress maybe the meteoroid is a red herring and a virus spread by the rapidly co-evolving smaller mammals is what done it for the big guys of the time?

[Blind groper]

To Scumple

That is unlikely. Normally a mammalian virus has little effect on reptiles. Such a virus is more likely to kill off the mammals leaving the reptiles untouched. It is also unlikely that any single virus could kill off so many different taxonomic groups.

[theropod]

With the decline already in progress maybe the meteoroid is a red herring and a virus spread by the rapidly co-evolving smaller mammals is what done it for the big guys of the time?

The trouble with this is that marine reptiles, ammonites and other sea faring species also bite the dust around the same time. Also there were large land masses isolated from one another that would have limited any such outbreak. Granted, there were pterosaurs that might have been able to carry such a virus, or other pathogen, from one location to another, but the chances of a cephalopod contracting an illness that would also effect a reptile are vanishingly small.

RS

[mistermack]

With the decline already in progress maybe the meteoroid is a red herring and a virus spread by the rapidly co-evolving smaller mammals is what done it for the big guys of the time?

The trouble with this is that marine reptiles, ammonites and other sea faring species also bite the dust around the same time. Also there were large land masses isolated from one another that would have limited any such outbreak. Granted, there were pterosaurs that might have been able to carry such a virus, or other pathogen, from one location to another, but the chances of a cephalopod contracting an illness that would also effect a reptile are vanishingly small.

RS

What I can't work out, is how the crocodiles survived. Admittedly, they're not as big as some of the dinosaurs, but apart from that, what was the magic ingredient that they had, that saved them from extinction?
Maybe, like turtles, it was the fact that they buried their eggs?
I don't know much about dinosaur habits, although I seem to remember fossil nests being found, showing that at least some were ground-laying, like the ostrich.

Maybe buried eggs can survive a cold snap better.

[theropod]

With the decline already in progress maybe the meteoroid is a red herring and a virus spread by the rapidly co-evolving smaller mammals is what done it for the big guys of the time?

The trouble with this is that marine reptiles, ammonites and other sea faring species also bite the dust around the same time. Also there were large land masses isolated from one another that would have limited any such outbreak. Granted, there were pterosaurs that might have been able to carry such a virus, or other pathogen, from one location to another, but the chances of a cephalopod contracting an illness that would also effect a reptile are vanishingly small.

RS

What I can't work out, is how the crocodiles survived. Admittedly, they're not as big as some of the dinosaurs, but apart from that, what was the magic ingredient that they had, that saved them from extinction?
Maybe, like turtles, it was the fact that they buried their eggs?
I don't know much about dinosaur habits, although I seem to remember fossil nests being found, showing that at least some were ground-laying, like the ostrich.

Maybe buried eggs can survive a cold snap better.

Yes, it seems most non-avian dinosaurs did lay their eggs directly on the ground. The likelihood of any arboreal nests being preserved and found approaches zero, so that evidence, had it ever been, might be forever lost to us. Birds were already present in the biosphere well before the end Cretaceous, and some of them surely nested in trees.

Not all lineages of the crocodyliforms survived either. Body mass seems to have been a contributing factor, and I suspect that was a result of food availability. A smaller critter needs less food to survive. Considering how long the bolide induced winter may have lasted (perhaps several years) the buried eggs would have still faced extraordinary hardship upon hatching. Also the ability to enter a state of tupor, something hummingbirds do on a daily basis, and wait out cold weather may have contributed to some of them surviving.

Still, we are faced with the problem of why segments of the marine ecosystem, down to the tiny flagellates, saw a mass extinction as well. Buried eggs doesn't account for this.

I suspect this question will attract such questions for a very long time, and we may never have a truly robust set of answers, but it is one of the great quests in paleontology.

RS

[mistermack]

Crocodiles and turtles bury their eggs. Birds are warm blooded and have feathers, and they sit on the eggs and incubate them.
But there again, some dinosaurs are supposed to have been warm blooded and feathered too.

Turtles survived, but other marine reptiles didn't. Some big marine carnivores did, the white shark, but the mega-shark didn't.
They might be able to work it out, if they get better information about exactly what the climate was like, as opposed to the vague clues we've got now.

That might be possible one day. If you accurately knew the climate, you might have a good idea what was happening.

[Blind groper]

My personal theory as to why crocodiles survived is that they can go a long time without food. Six months has been demonstrated.

It appears that many, if not all, dinosaurs, were warm blooded. This means a need for lots of food to fuel their bodies. When things get bad, and food is scarce, they die.

The great asteroid impact would have darkened the world for a long time, meaning that green plants die off. Insects will survive, as will those who eat insects, since they eat the rotting plant detritus. Plant seeds will also survive (those that don't get eaten anyway) and will germinate when sunlight appears again. Large harbivores, though, will die off when the trees die, and their predators will also die. Crocodiles will survive on very little food, until good times return.

[JimC]

My personal theory as to why crocodiles survived is that they can go a long time without food. Six months has been demonstrated.

It appears that many, if not all, dinosaurs, were warm blooded. This means a need for lots of food to fuel their bodies. When things get bad, and food is scarce, they die.

The great asteroid impact would have darkened the world for a long time, meaning that green plants die off. Insects will survive, as will those who eat insects, since they eat the rotting plant detritus. Plant seeds will also survive (those that don't get eaten anyway) and will germinate when sunlight appears again. Large harbivores, though, will die off when the trees die, and their predators will also die. Crocodiles will survive on very little food, until good times return.

And also, they are excellent scavengers; lots of dead bodies would be around...