Impact that killed the dinosaurs?

[Brian G Turner]

BTW, I was curious enough to hurredly run some very approximate numbers for the Chicxulub impact. If the energy were distributed uniformly over the entire world, no matter where you are, land or sea, it would be like standing within one and a quarter miles of four Hiroshima bombs. That wouldn't be enough energy to put anything at risk.....

In which case all life on earth was wiped out 66 mya. Does that match observation?

 

[JimC]

Close enough - much of it was. That visualization tool assumed that all energy was retained within the atmosphere. In actuality thank god, quite a bit of it was immediately ejected back into space. It also assumed that the energy was distributed uniformly. Again thank god, it wasn't. It's still a durned good tool for visualizing the total amount of energy involved.

Another demonstration of the energy involved is that the Continental Shelf along most of the Eastern Seaboard failed, and the consequent landslide extended eastward to the mid-Atlantic Ridge. That did a number on many of the bottom dwellers in the western Atlantic.

And the forces generated were violent enough to tear the leg off one poor Dino up near the Canadian Border (even though he was quite a respectable distance from Chicxulub).

The loss of the pterosaurs is what hit me hardest. I wish they were still with us.

 

[BAYLOR]

"Recent articles on the impact theory have stated that the Chicxulub event would not have had sufficient energies to cause the global devastation postulated in the classic model,"

What is the energy range currently estimated for the impact?
How many simultaneous Tzar Bombas would that be equivalent to?
I could calculate those numbers myself - but I'm lazy.

Some dinos did survive - we call 'em birds.
As an aside, the effects of the impact were the primary reason for the demise of the pterosaurs (they were not dinos). I would expect that large and small, they were most likely gone worldwide within a month of the impact, possibly less. There were no large soaring birds before the impact, but for the obvious reasons, I would expect small birds to to make it through when pterosaurs couldn't. It took large soaring birds 5 to 10 million years to develop after the pterosaurs were gone.

BTW, this is me out in my front yard holding the left humerus of one of the larger Late Cretaceous pterosaurs. Shoulder is in my right hand, elbow in my left.
View attachment 110853

Given the the aftermath of the impact and the massive climate disruption and degradations . How did reptiles and amphibians survive ?

 

[JimC]

Same ways mammals did.
If I remember correctly, nothing that weighed much over 40 pounds survived.

 

[mosaix]

BTW, I was curious enough to hurredly run some very approximate numbers for the Chicxulub impact. If the energy were distributed uniformly over the entire world, no matter where you are, land or sea, it would be like standing within one and a quarter miles of four Hiroshima bombs. That wouldn't be enough energy to put anything at risk.....

I did this very quickly and didn't check it, so feel free to point out potential errors.

Is that a typo @JimC?

I would have thought that standing within one and a quarter miles of four Hiroshima bombs would be enough to put anything at risk. Or am I misunderstanding what you are saying?

Thanks for all the info BTW.

 

[JimC]

It was deliberate tongue in cheek.

An explosion that caused the Continental shelf to fail along the entire east coat of the Americas, generating mudslides that reached the Mid-Atlantic Ridge would have consequences. BTW, I'm not denegrating the effect of the earlier Deccan Traps either.
Also, the Western Interior Seaway was receding at the time of the impact, creating a shelf parallel to the Continental coastline. The shelf greatly attenuated the tsunami that was headed north, minimizing its effects. The attached map is from 80 Mya. The Seaway was a good bit smaller by the time of the impact.

 

[BAYLOR]

I also like the Farside's explanation for the Why the Dinos went extinct.

 

[JimC]

Me too. I like Larson.

 

[chornedsnorkack]

There were some questions about the odd survivals. Like, how did so much diversity of bees survive?
Also, a question I once asked: "How do pterosaurs breathe"?
Flighted birds rely on a heavy keel on their breast. Note that the
keelbone of a bird supports both the muscles for a downstroke and the
muscles for upstroke - the muscles for upstroke are on bird´s chest,
not on its back.

Bats are different from birds in some respects. For example, the
distribution of fingers in bat´s wing is rather different from that of
a bird wing. And IIRC, the arrangement of flight muscles is different
for a bat. The downstroke muscles are on the breast, and supported on
keelbone. But the upstroke muscles are on the back.

Note that biggest extant fruitbats are rather smaller than biggest
extant birds.

The arrangement of fingers in the wing of a pterosaur is again
different from a wing of bird or bat. But what is the pectoral girdle
of a pterosaur like? And where are the flight muscles supposed to have
gone?
Bats do not have avian respiratory system. How do pterosaurs breathe?

 

[BAYLOR]

And here is a Quetz torso. Only 4 vertebrae are unfused. Pterosaur ribcages don't expand like the mammalian ribcage. Instead, flexing the unfused vertebrae in the spine down and up moves the diaphragm fore and aft, deflating and inflating the tiny lungs inside the fixed ribcage. Pterosaurs are more pneumatic than birds, but span for span, their necks tend to be longer, increasing dead air volume, and their lungs smaller, decreasing pumping capacity. Consequently, they are flap-gliders, mostly soaring with occasional intermittant short duration flapping.
View attachment 110939

There were indications that even bofore the astroid that Dinosaurs were in decline in terms species . If not for the asteroid , would these flying reptiles have survived have been able to compe with directly with Birds ?

And also if not for the asteroid, how much longer would Dinosaurs have likely continued to exist on Earth ?

 

[chornedsnorkack]

There were indications that even bofore the astroid that Dinosaurs were in decline in terms species . If not for the asteroid , would these flying reptiles have survived have been able to compe with directly with Birds ?

Pterosaurs did coexist with birds. There was an appreciable diversity of enantiornithes, who did not survive. Plus the ancestors of true birds.
Birds with limited flapping ability are very much around now. Hens and turkeys rely in flight - fly to roost, to cross obstacles, short spurts away from dangers - but cannot fly long times. Their relatives quail do fly sustained.
How much did pterosaurs act and feed on ground?

 

[JimC]

"If not for the asteroid , would these flying reptiles have survived have been able to compe with directly with Birds ?"

It's the other way round. Birds could not compete with them. That's why large soaring birds didn't arrive till after they were gone. Another advantage was that they could fly immediately upon hatching. Birds can't.
Pterosaurs died out for two reasons - limited fat stores and an inability to flap continuously due to limited lung capacity and a high percentage of dead air volume. Most were piscavores, and they couldn't withstand a few weeks of weather that was unsuitable for soaring flight. If not for the impact, they would probably still be here.

Dinosaurs still exist on Earth. Birds are maniraptoran theropods.

 

[chornedsnorkack]

"If not for the asteroid , would these flying reptiles have survived have been able to compe with directly with Birds ?"

It's the other way round. Birds could not compete with them. That's why large soaring birds didn't arrive till after they were gone. Another advantage was that they could fly immediately upon hatching. Birds can't.

Most extant birds don´t. But even extant birds have an exception: scrubfowl, who take off on hatching. And it seems that enanthiornithes were also superprecocial.

 

[JimC]

One thing to remember about pterosaurs is that at the time of their demise they were biomechanically far more sophisticated than birds - they had a huge evolutionary headstart. They were actually more sophisticated than modern birds - but they were overspecialized - a trap that birds sidestepped.

 

[chornedsnorkack]

One thing to remember about pterosaurs is that at the time of their demise they were biomechanically far more sophisticated than birds - they had a huge evolutionary headstart. They were actually more sophisticated than modern birds - but they were overspecialized - a trap that birds sidestepped.

Most birds also died. Like, all the enanthiornithes.
What were flaplings like? How do you spot a flapling? That is, how do you distinguish the fledged young of a large pterosaur species from an adult of a small species? And once you do identify a pterosaur as a flapling, how do you match the juvenile to its parents?

 

[JimC]

When referring to pterosaurs, what do you mean by 'fledged'??

"young of a large pterosaur species from an adult of a small species?"

Generally, by appearance. Bone morphology.

 

[BAYLOR]

In the movies , they mistakenly put together Dinosaurs from different eras. For example In Fantasia you see a T Rex battling a Stegosaurus . That never happened because Stegosaurus died out 80 million years before T Rex arrived on the scene.

 

[CupofJoe]

In the movies , they mistakenly put together Dinosaurs from different eras. For example In Fantasia you see a T Rex battling a Stegosaurus . That never happened because Stegosaurus died out 80 million years before T Rex arrived on the scene.

At least in the 1930s King Kong the T Rex is fighting a Triceratops!

 

[Matteo]

It's Adric I feel sorry for...



...well, maybe not.

 

[BAYLOR]

It's Adric I feel sorry for...



...well, maybe not.

Well, if it weren't for Adriac , we all wouldn't be here now.