Avian vs. Non-avian dinosaur survivability

[RadFox]

Are there any theories as to how avian dinosaurs were able to survive the K-Pg extinction while no known non-avian dinosaurs were able to?

[+Desertrat56]

7 minutes ago, RadFox said:

Are there any theories as to how avian dinosaurs were able to survive the K-Pg extinction while no known non-avian dinosaurs were able to?

Wait, aren't crocodiles, lizards and alligators as much dinosaurs as birds are?

[Orphalesion]

19 minutes ago, Desertrat56 said:

Wait, aren't crocodiles, lizards and alligators as much dinosaurs as birds are?

No. Corcodilia are the llast surviving members of a (relatively) closely related clade to Dinosauria (dinosaurs, birds) and Pterosauria (flying reptiles) .

Lizards are more distantly related to dinosaurs than crocodiles or pterosaurs.

Birds on the other hand are the last surviving class of Dinosaurs.

Edited July 5, 2020 by Orphalesion

[+Noteverythingisaconspiracy]

2 hours ago, RadFox said:

Are there any theories as to how avian dinosaurs were able to survive the K-Pg extinction while no known non-avian dinosaurs were able to?

Their small size meant they needed less of the scarce food supplies and their ability to fly made it easier to move into more hospitable areas. Their ability to make nests might also have provided some cover from the initial effects of the K-Pg event.

Basically they were small and adaptable. 

[Wepwawet]

What gives an indication of the severity of the event is how many birds never made it. Small size, lower food requirement and ability to migrate, as noted above, are all important factors, but as the vast majority of birds of many different lineages became extinct, luck must have played a major role.

There are some puzzles, such as why not a single pterosaur survived, and why some non avian dinosaurs that you would think could have survived, did  not. I'm thinking here of the "raptors", particularly the troodontids. Warm blooded, agile, comparatively intelligent, many of small size, their prey of smaller mammals surviving, and worldwide distribution, yet all gone.

[Carnoferox]

2 hours ago, Noteverythingisaconspiracy said:

Their small size meant they needed less of the scarce food supplies and their ability to fly made it easier to move into more hospitable areas. Their ability to make nests might also have provided some cover from the initial effects of the K-Pg event.

Basically they were small and adaptable. 

Size really doesn't seem to have been a deciding factor. There were plenty of small non-avialan dinosaurs that went extinct and plenty of small avialan dinosaurs too.

[Orphalesion]

39 minutes ago, Carnoferox said:

Size really doesn't seem to have been a deciding factor. There were plenty of small non-avialan dinosaurs that went extinct and plenty of small avialan dinosaurs too.

So what were the deciding factors? Do we know? Or was it just a matter of luck what species survived? 
 

[Carnoferox]

51 minutes ago, Orphalesion said:

So what were the deciding factors? Do we know? Or was it just a matter of luck what species survived? 
 

We really don't know. Deciding factors that have been hypothesized (smaller size, burrowing/nesting, higher metabolism, etc.) can be ruled out because non-avialan dinosaurs also met those qualifications.

[Orphalesion]

5 hours ago, Carnoferox said:

We really don't know. Deciding factors that have been hypothesized (smaller size, burrowing/nesting, higher metabolism, etc.) can be ruled out because non-avialan dinosaurs also met those qualifications.

Ah okay, I guess it makes sense that we don't have every minute detail on something that happened 65 million years ago and don't know every single factor involved.

You know I always wondered with how few species are actually preserved in the fossil record (I read somewhere it's 99.9% of species aren't preserved) whether a very small handful of non-avian dinosaur species might have survived K-Pg, but were out competed by the diversifying mammals and avian dinosaurs and died off pretty quickly, without leaving any fossils. Maybe some Micro Raptors or something living in an environment that was very unlikely to lead to fossilization or something. Or maybe there's some fossils of early Paleocene dinosaurs somewhere under the antarctic ice...

Don't worry I'm not trying to create any woo theories about non-avian dinosaurs surviving into modern day, and I'm not taking it too seriously. It's just something fun I like to think about on occasion.

Edit: Just reading about it for the first time in years. This is the first time I read about the dominance of fungi and (eventually) ferns in the post K-Pg world!

Edited July 6, 2020 by Orphalesion

[Carnoferox]

8 hours ago, Orphalesion said:

Ah okay, I guess it makes sense that we don't have every minute detail on something that happened 65 million years ago and don't know every single factor involved.

You know I always wondered with how few species are actually preserved in the fossil record (I read somewhere it's 99.9% of species aren't preserved) whether a very small handful of non-avian dinosaur species might have survived K-Pg, but were out competed by the diversifying mammals and avian dinosaurs and died off pretty quickly, without leaving any fossils. Maybe some Micro Raptors or something living in an environment that was very unlikely to lead to fossilization or something. Or maybe there's some fossils of early Paleocene dinosaurs somewhere under the antarctic ice...

Don't worry I'm not trying to create any woo theories about non-avian dinosaurs surviving into modern day, and I'm not taking it too seriously. It's just something fun I like to think about on occasion.

Edit: Just reading about it for the first time in years. This is the first time I read about the dominance of fungi and (eventually) ferns in the post K-Pg world!

There's a high likelihood that some dinosaurs survived into the first few thousand years of the Paleocene, we just haven't found any concrete examples yet. There have been a few claims of Paleocene dinosaurs in the past but they turned out to have been eroded out of older sediments.

[Wepwawet]

12 hours ago, Orphalesion said:

Ah okay, I guess it makes sense that we don't have every minute detail on something that happened 65 million years ago and don't know every single factor involved.

You know I always wondered with how few species are actually preserved in the fossil record (I read somewhere it's 99.9% of species aren't preserved) whether a very small handful of non-avian dinosaur species might have survived K-Pg, but were out competed by the diversifying mammals and avian dinosaurs and died off pretty quickly, without leaving any fossils. Maybe some Micro Raptors or something living in an environment that was very unlikely to lead to fossilization or something. Or maybe there's some fossils of early Paleocene dinosaurs somewhere under the antarctic ice...

Don't worry I'm not trying to create any woo theories about non-avian dinosaurs surviving into modern day, and I'm not taking it too seriously. It's just something fun I like to think about on occasion.

Edit: Just reading about it for the first time in years. This is the first time I read about the dominance of fungi and (eventually) ferns in the post K-Pg world!

That mammals were able to start the evolutionary process to fill the gaps, shows that non avian dinosuars did not survive. If they had, theropods specifically, they would have supressed the explosion of mammals. We have an example of this, to an extent, with the rise of the "terror birds" in South America were they were the dominant animal and at the top of the food chain. Even when the Panama land bridge formed and mammal carnivores moved south, and some "terror birds" moved north of course, it seems that it wasn't necessarily the big cats that did for them, but ecological and environmental changes.

It was just luck for the "terror birds" that no serious mammal carnivores evolved in South America while the non terrifying ancestors began their evolution to become terrifying. There was some convergent evolution of birds outside of South America, but they never became dominant because felines emerged in Asia and had no barriers to moving west. I think if just one species of "raptor" had survived, then just like their bird cousins they would have rapidly diversified and spread, and we would still be little burrowing critters.

[Orphalesion]

17 hours ago, Wepwawet said:

That mammals were able to start the evolutionary process to fill the gaps, shows that non avian dinosuars did not survive. If they had, theropods specifically, they would have supressed the explosion of mammals. We have an example of this, to an extent, with the rise of the "terror birds" in South America were they were the dominant animal and at the top of the food chain. Even when the Panama land bridge formed and mammal carnivores moved south, and some "terror birds" moved north of course, it seems that it wasn't necessarily the big cats that did for them, but ecological and environmental changes.

It was just luck for the "terror birds" that no serious mammal carnivores evolved in South America while the non terrifying ancestors began their evolution to become terrifying. There was some convergent evolution of birds outside of South America, but they never became dominant because felines emerged in Asia and had no barriers to moving west. I think if just one species of "raptor" had survived, then just like their bird cousins they would have rapidly diversified and spread, and we would still be little burrowing critters.

I wasn't really thinking about populations that were healthy enough to to branch out again, I was thinking of some stragglers that, like Carnoferox said, survived for a few thousand years, slowly dwindling into extinction.

[Wepwawet]

47 minutes ago, Orphalesion said:

I wasn't really thinking about populations that were healthy enough to to branch out again, I was thinking of some stragglers that, like Carnoferox said, survived for a few thousand years, slowly dwindling into extinction.

Yes, there's the hadrosaur fossils that seem to come from after the extinction, but will be secondry burials. I do in fact think that there were some survivals of small non avian dinosaurs as I don't see the event as being a sudden switching off around the globe, which is often the way it is presented. Maybe some groups hung on for a few thousand years, to short a time span to clearly see if their fossils are below or above the irridium layer. It's possible that in some places they survived a few hundred thousand years, even a million, and are waiting to be discovered, perhaps on isolated islands until in the course of time the islands dissapeared or changed to much to support them.