Why couldn't the Dinosaurs survive the K-T extinction?

[Archbob]

So it kind of makes me wonder. I know that smaller animals are better suited to survived stuff like this but dinosaurs came in all shapes and sizes. Why couldn't one of the smaller species have survived the K-T extinction like they survived the Triassic-Jurassic transition?

 

[warpus]

They did, and then evolved into birds, crocodiles, etc.

 

[Mowque]

Also, many other varieties were hard hit by climate change and whatnot.

 

[Miles Teg]

They did, and then evolved into birds, crocodiles, etc.

Those events occurred significantly before the K-T extinction. Actually, dinosaurs never evolved into crocodiles. Those are a separate, related lineage.

To answer the question, the probable reason is that a comet kicked up a huge cloud of dust, blocked light and lowered the temperature, and the dinosaurs starved.

 

[Masada]

The dinosaurs didn't pay for life insurance

 

[Berzerker]

dinos were warm blooded, need food often - lizards can go a long time between meals. Crocs are lizards, not dinos, but birds could find food easier. Sharks have been around far longer than the dinos but they survived the extinction event because the seas are more stable for major predators and sharks are damn near perfect eating machines.

 

[AngryZealot]

Birds are dinosaurs just like humans are mammals.

 

[RalofTyr]

dinos were warm blooded, need food often - lizards can go a long time between meals. Crocs are lizards, not dinos, but birds could find food easier. Sharks have been around far longer than the dinos but they survived the extinction event because the seas are more stable for major predators and sharks are damn near perfect eating machines.

So were mammals; warm blooded that is.

It was actually smaller sharks that survived and evolved into larger ones.

Dinosaurs had a long time to get specialized to their environment, probably, too specialized and when change occurred, they were unable to deal with it.

I'm sure many small dinosaurs did survive. No, they didn't evolve into birds. Birds were already around by that time of the K-T impact. They just couldn't compete with the mammals who were specialized in scavenging and operating in darkness.

It is my theory that dinosaurs did survive in Antarctica for up until 15 million years ago, when Antarctica froze. If a Dinosaur could survive the long nights in Antarctica, they could survive the K-T Impact.

 

[Winner]

BTW, many species of dinosaurs were already getting extincts by the end of Cretaceous period, especially the big ones. When the asteroid hit, it was the last straw.

As for the smaller species - as far as I know:

- they were better suited for a warm environment, so the "asteroid winter" which followed the impact killed them en masse
- they were too specialized and inter-dependent with other dinosaur species. As the ecosystem was disrupted, the whole species pyramid collapsed.
- I read somewhere that dinosaurs were adapted to much higher O2 in the atmosphere. As much of it was burned in global firestorms which followed the impact, they suffocated.

It was a combination of factors which was devastating to the dominant life forms (dinosaurs), but less destructive to some formerly suppressed lifeforms like mammals or birds (who evolved from the dinosaurs during Jura). In the post-impact world in which they had no advantage over these lifeforms, they were quickly outcompeted and died off.

 

[Miles Teg]

Crocs are lizards, not dinos,.

This is a surprisingly common idea, and it really needs to be squashed. Crocodiles, like Dinosaurs, are Archosaurs. These are a type of reptile, quite distinct from the other types. They became big after the massive Permian-Triassic extinction event, and dinosaurs were just one of many types. They only really took off after the Triassic-Jurassic extinction event wiped away most non Dinosaurian Archosaurs. Crocodilians were a prominent survivor however.

Ironically, the main distinguishing feature of an Archosaur is it's erect hip joints, similar to mammals, but crocodiles have gone back to the sprawling hips of lizards. They're still obvious archosaurs however, due to dozens of more minor factors.

 

[Perfection]

So it kind of makes me wonder. I know that smaller animals are better suited to survived stuff like this but dinosaurs came in all shapes and sizes. Why couldn't one of the smaller species have survived the K-T extinction like they survived the Triassic-Jurassic transition?

Perfection's guess he's pulling out of his ass:

Maybe the small dinosaurs didn't survive because they were already dead (ie, at the time of KT birds, mammals, and other reptiles [snakes, lizards] had already out competed dinosaurs).

 

[Archbob]

- I read somewhere that dinosaurs were adapted to much higher O2 in the atmosphere. As much of it was burned in global firestorms which followed the impact, they suffocated.

No, I believe it was the P-T extinction and not the K-T extinction where oxygen dropped.

 

[Berzerker]

This is a surprisingly common idea, and it really needs to be squashed. Crocodiles, like Dinosaurs, are Archosaurs. These are a type of reptile, quite distinct from the other types. They became big after the massive Permian-Triassic extinction event, and dinosaurs were just one of many types. They only really took off after the Triassic-Jurassic extinction event wiped away most non Dinosaurian Archosaurs. Crocodilians were a prominent survivor however.

Ironically, the main distinguishing feature of an Archosaur is it's erect hip joints, similar to mammals, but crocodiles have gone back to the sprawling hips of lizards. They're still obvious archosaurs however, due to dozens of more minor factors.

well you sure squashed that common idea, crocs are fallen archosaurs

 

[Miles Teg]

The word "fallen" is pretty inapplicable to biology. Despite what Hollywood or some creationist or whoever might think, evolution doesn't involve "levels" or anything like that. The crocodile's sprawling posture is well adapted to it's semi-aquatic lifestyle. The crocodile's ancestor's were somewhat different, being fast terrestrial predators, they looked more like this. Still, crocodiles stand more erect than the vast majority of lizards.

 

[Berzerker]

Jesus, it was a play on words

 

[Miles Teg]

Err, yes, yes it was.

And my blindness for puns got us both a pun and a biology lesson, so it's double the fun.

 

[Danielos]

I think God become pissed of the dinosaurs for pooing everywhere in his Garden of Eden, making it a filthy, sinful place. When one Tyrannosaurus Rex attacked and ate an arch angel it was the last straw and he decided to wipe them out!

 

[Loki130]

it's worth noting there was a series of major eruptions in India at the same time, if it helps anyone's theory.

here's mine: the mammals were expert scavengers, and could live on any little scrap of food was left around in a way the specialized hunters couldn't. Also, mammals and birds are fast breeders-they passed through generations faster than dinosaurs, so they could adapt faster. The dinosaur reproductive process was more susceptable to poisonous gases, and the eggs were vulnerable to the scavenging mammals. the crocs survived because they were warm blooded, and needed less food.

 

[Agent327]

They did, and then evolved into birds, crocodiles, etc.

Dinosaurs did not evolve into crocodiles as crocodiles are reptiles and are around at least since the Cretaceous. Birds did evolve from dinosaurs, answering the OT question.

 

[tycoonist]

here's mine: the mammals were expert scavengers, and could live on any little scrap of food was left around in a way the specialized hunters couldn't. Also, mammals and birds are fast breeders-they passed through generations faster than dinosaurs, so they could adapt faster. The dinosaur reproductive process was more susceptable to poisonous gases, and the eggs were vulnerable to the scavenging mammals. the crocs survived because they were warm blooded, and needed less food.

i think there is a lot of truth in this argument. one of the key factors, if not the key factor which enabled the success of mammals was there reproductive system. the longer gestation period in a protected environment meant that when offspring was born, they were able to withstand harsher conditions. it should also be noted that mammals had been living in this way for thousands of years by this stage: primarily underground, scavenging for whatever they could find. large dinosaurs were far more likely to be effected by the prolonged exposure to the harsh climate.