Why dinosaurs probably evolved to birds?

[Paramecium8]

Dinosaurs probably had feathers and the ones that survived evolved to the actual birds? Why they evolved to smaller animals?

[Phi for All]

Many reasons. Big animals need a LOT of food. Less resources mean a population will often decrease in physical size. The smaller ones that needed less food also had the better chances of gliding using their feathers, which guaranteed that gliding would become more successful in successive generations, and eventually lead to actual flight.

[overtone]

There were small bird-like dinos around long before the main extinction event - https://en.wikipedia.org/wiki/File:Anchiornis_BW.jpg( note the size. The feathers and colors are not guessed, but from evidence).

 

The mass extinction event survival of small, mobile, widely dispersed, well-insulated, and quickly reproducing animals, although not known in detail, is not generally thought to have been completely mysterious - presumably the birdlike dinos survived for much the same reason the shrew-like mammals did.

 

Side note: it's possible - even likely - that wingflap advantages in running and climbing drove the evolution of flight capability in dinos, and gliding specialization was a dead end.

Edited June 17, 2015 by overtone

[Moontanman]

Birds are to dinosaurs as bats are to mammals, dinosaurs didn't evolve into birds any more than mammals have evolved into bats. It's just that avian dinosaurs survived the KT event and the large ground dwellers did not...

[Paramecium8]

Mammals are dinosaurs species that "evolved" too?

[Robittybob1]

Mammals are dinosaurs species that "evolved" too?

Good point. Have dinosaurs and mammals got a common ancestor?

[pzkpfw]

Good point. Have dinosaurs and mammals got a common ancestor?

https://en.wikipedia.org/wiki/Evolution_of_mammals

 

https://en.wikipedia.org/wiki/Tetrapod

Edited June 22, 2015 by pzkpfw

[delboy]

Mammals are dinosaurs species that "evolved" too?

 

 

Good point. Have dinosaurs and mammals got a common ancestor?

 

Everything has a common ancestor if you go back far enough. But mammals did not evolve from dinosaurs or even true reptiles. Mammals evolved within a group which branched off before all the reptilian features had evolved - the synapsids, often called 'mammal like reptiles'. They had many reptilian features but there were some they lacked.

[Moontanman]

 

 

 

Everything has a common ancestor if you go back far enough. But mammals did not evolve from dinosaurs or even true reptiles. Mammals evolved within a group which branched off before all the reptilian features had evolved - the synapsids, often called 'mammal like reptiles'. They had many reptilian features but there were some they lacked.

 

 

I gave you a pos rep for that but I really think you took it a little too far, dinosaurs evolved from reptiles for sure but ultimately so did mammals, it's really not proper to say that mammals and dinosaurs split off before reptiles became well... reptiles, there were a great many more different types of reptiles than we see today, turtles are anapsids and using your logic not true reptiles. Reptiles is really not a useful term to use in this context, about like the term "fish" it's far more proper to use more accurate terms.

 

I know, I'm being pedantic but so much real inaccuracy exists in phylogenetics and to be fair much of it is propagated due to science being dumbed down for "laymen" I've been mislead by this on several occasions and I may still not have it right but if we followed mammals back in time their ancestors and the ancestors of dinosaurs would have both been identified as reptiles, probably lizards but they wouldn't have been lepidosaurs because they didn't evolve until after both dinosaurs and mammals had evolved.

 

At the earliest era we had diapsids, anapsids, and synapsids and other groups that did not fit into any of these three categories. All of them would have been identified as reptiles today Like for instance dimetrodon which was a synapsid which are what we mammals are..

[delboy]

 

 

I gave you a pos rep for that but I really think you took it a little too far, dinosaurs evolved from reptiles for sure but ultimately so did mammals, it's really not proper to say that mammals and dinosaurs split off before reptiles became well... reptiles, there were a great many more different types of reptiles than we see today, turtles are anapsids and using your logic not true reptiles. Reptiles is really not a useful term to use in this context, about like the term "fish" it's far more proper to use more accurate terms.

 

I know, I'm being pedantic but so much real inaccuracy exists in phylogenetics and to be fair much of it is propagated due to science being dumbed down for "laymen" I've been mislead by this on several occasions and I may still not have it right but if we followed mammals back in time their ancestors and the ancestors of dinosaurs would have both been identified as reptiles, probably lizards but they wouldn't have been lepidosaurs because they didn't evolve until after both dinosaurs and mammals had evolved.

 

At the earliest era we had diapsids, anapsids, and synapsids and other groups that did not fit into any of these three categories. All of them would have been identified as reptiles today Like for instance dimetrodon which was a synapsid which are what we mammals are..

 

It kind of illustrates the point that all classification is slightly arbitrary. I was using the accepted classification that separates synapsids as non-reptiles (though my uninformed gut feeling is that they could easily be included). My understanding is that reptiles (to include anapsids and diapsids) are a good clade (if you include birds), unlike 'fish'. And dinosaurs evolved within that clade and mammals did not.

 

The main difference I have heard is that synapsids have alpha keratin in the skin and anapsids/diapsids/birds all have beta keratin.

[Moontanman]

 

It kind of illustrates the point that all classification is slightly arbitrary. I was using the accepted classification that separates synapsids as non-reptiles (though my uninformed gut feeling is that they could easily be included). My understanding is that reptiles (to include anapsids and diapsids) are a good clade (if you include birds), unlike 'fish'. And dinosaurs evolved within that clade and mammals did not.

 

The main difference I have heard is that synapsids have alpha keratin in the skin and anapsids/diapsids/birds all have beta keratin.

 

 

Can you provide a citation for that last?

[delboy]

 

 

Can you provide a citation for that last?

 

You've got me wondering now. I had thought I'd read it in Dawkins' Ancestor's Tale but I've looked in the likely bits and couldn't find it. So I Googled and it came up with a thread I started here! I said I'd just found a reference to it but I've now forgotten where that was!! Very annoying, it's bugging me now!

[Moontanman]

 

You've got me wondering now. I had thought I'd read it in Dawkins' Ancestor's Tale but I've looked in the likely bits and couldn't find it. So I Googled and it came up with a thread I started here! I said I'd just found a reference to it but I've now forgotten where that was!! Very annoying, it's bugging me now!

 

 

You may still be correct but i know I have never heard that...

[delboy]

 

 

You may still be correct but i know I have never heard that...

 

I'm sure it would have been a reliable reference.

There is a brief mention here https://en.wikipedia.org/?title=Keratin

[pavelcherepan]

 

It kind of illustrates the point that all classification is slightly arbitrary. I was using the accepted classification that separates synapsids as non-reptiles (though my uninformed gut feeling is that they could easily be included). My understanding is that reptiles (to include anapsids and diapsids) are a good clade (if you include birds), unlike 'fish'. And dinosaurs evolved within that clade and mammals did not.

 

The main difference I have heard is that synapsids have alpha keratin in the skin and anapsids/diapsids/birds all have beta keratin.

I thought that the main difference was in the jaw bones arrangement. I can't remember anything about keratin from paleontology classes. Of course, you might be right but jaw bones are a better tool for classification anyway, simply because they preserve better.

[Moontanman]

 

I'm sure it would have been a reliable reference.

There is a brief mention here https://en.wikipedia.org/?title=Keratin

 

 

My main beef in this is the implied assumption that everything alive at the time fit into neat categories and that there were three of them or two or 22, we really don't know and the mammal like reptiles are generally identified as dinosaurs and they were a very diverse group and the mammals we see today are the result of a tiny offshoot. Reptile is not a useful term any more than fish is a useful term. Don't take me too seriously, I used to think the number of animals was small and easy to separate out of the herd as well. It has become somewhat more interesting now that I know (think I know) that the ecology was far more diverse and included animals we really can't classify accurately. Amphibian is yet another term that we look at modern examples for guidance and get a totally wrong idea, mooeypoo taught me that!

[delboy]

I thought that the main difference was in the jaw bones arrangement. I can't remember anything about keratin from paleontology classes. Of course, you might be right but jaw bones are a better tool for classification anyway, simply because they preserve better.

 

I think that the keratin difference is useful to infer the early split of synapsids from the reptilian line, before beta keratin had evolved. And it seems it's a difference that has remained over a long time. The jaw bone changes are a beautiful example of evolution. Synapsids started with a reptilian arrangement and over time two bones migrated into the ear to create the mammalian arrangement (in the mammalian offshoot anyway).

Fossils certainly preserve well, but I'm sure chemicals are equally useful (in a different way) when you have extant species - maybe even more useful??

 

 

My main beef in this is the implied assumption that everything alive at the time fit into neat categories and that there were three of them or two or 22, we really don't know and the mammal like reptiles are generally identified as dinosaurs and they were a very diverse group and the mammals we see today are the result of a tiny offshoot. Reptile is not a useful term any more than fish is a useful term. Don't take me too seriously, I used to think the number of animals was small and easy to separate out of the herd as well. It has become somewhat more interesting now that I know (think I know) that the ecology was far more diverse and included animals we really can't classify accurately. Amphibian is yet another term that we look at modern examples for guidance and get a totally wrong idea, mooeypoo taught me that!

 

I don't think I implied any of the things you say.

I think I agree with everything you say (assuming you mean that mammal like reptiles are falsely identified as dinosaurs). Your beef is with the strawman.

[pavelcherepan]

My main beef in this is the implied assumption that everything alive at the time fit into neat categories and that there were three of them or two or 22, we really don't know and the mammal like reptiles are generally identified as dinosaurs

 

I'm a bit confused about this one. What do you mean by "generally identified as dinosaurs"?

 

 

I think that the keratin difference is useful to infer the early split of synapsids from the reptilian line, before beta keratin had evolved. And it seems it's a difference that has remained over a long time. The jaw bone changes are a beautiful example of evolution. Synapsids started with a reptilian arrangement and over time two bones migrated into the ear to create the mammalian arrangement (in the mammalian offshoot anyway).

Fossils certainly preserve well, but I'm sure chemicals are equally useful (in a different way) when you have extant species - maybe even more useful??

 

Is there any evidence of fossil preservation of different types of keratin? Or is the assumption based on genetical dating?

[Moontanman]

 

I'm a bit confused about this one. What do you mean by "generally identified as dinosaurs"?

 

 

Is there any evidence of fossil preservation of different types of keratin? Or is the assumption based on genetical dating?

 

 

Dinosaurs are a specific group of animals, creatures like dimetrodon https://en.wikipedia.org/wiki/Dimetrodonand quite a few others often asserted to be dinosaurs were not..

[delboy]

 

Is there any evidence of fossil preservation of different types of keratin? Or is the assumption based on genetical dating?

 

I doubt fossil evidence. I assume it's known that alpa keratin is the more primitive form (if amphibians have alpha keratin this would prove it). So synapsids must have branched off before beta keratin (which all extant reptiles/birds have) evolved. So if amphibians and mammals both have alpha keratin then all synapsids must have had too.

[pavelcherepan]

Dinosaurs are a specific group of animals, creatures like dimetrodon https://en.wikipedia.org/wiki/Dimetrodonand quite a few others often asserted to be dinosaurs were not..

 

I don't think there ever was much confusion regarding Dimetrodon in particular within the scientific community simply because it's a Permian creature and dinosaurs as a distinct group didn't appear until early-mid Triassic. It's only in popular media it could've been dubbed as a dinosaur simply because it sort of looks like one. Also some confusion arises from the fact that many Permian synapsids have the -saurus suffix in their names.

 

 

I doubt fossil evidence. I assume it's known that alpa keratin is the more primitive form (if amphibians have alpha keratin this would prove it). So synapsids must have branched off before beta keratin (which all extant reptiles/birds have) evolved. So if amphibians and mammals both have alpha keratin then all synapsids must have had too.

 

But if reptiles have evolved from amphibians wouldn't that mean that early reptiles would have had alpha-keratin too (before beta-keratin had evolved)?

[Moontanman]

 

I don't think there ever was much confusion regarding Dimetrodon in particular within the scientific community simply because it's a Permian creature and dinosaurs as a distinct group didn't appear until early-mid Triassic. It's only in popular media it could've been dubbed as a dinosaur simply because it sort of looks like one. Also some confusion arises from the fact that many Permian synapsids have the -saurus suffix in their names.

 

 

But if reptiles have evolved from amphibians wouldn't that mean that early reptiles would have had alpha-keratin too (before beta-keratin had evolved)?

 

 

It was in layman terms i was talking about although i do have some old science books that blurred the lines more than a bit..

[delboy]

 

But if reptiles have evolved from amphibians wouldn't that mean that early reptiles would have had alpha-keratin too (before beta-keratin had evolved)?

 

Over the millions of years that reptiles evolved from amphibians the various reptilian features must have evolved at different times. There were probably a whole load of species that would have been difficult to put in one box or another. Beta keratin was probably one of the last features to evolve and synapsids branched off just before then. As Moontanman says, there would have been lots of different species with a whole mix of features. Plus it's about the arbitrary nature of classification. Evolution is gradual and various features evolve at different times. Classification likes to put things in sharply defined boxes, which just doesn't fit with how evolution works. I guess it has been deemed that to be a reptile it must have beta keratin. To my mind you would only have to be slightly less strict about it to include those with alpha keratin (plus any other minor differences synapsids have) - in which case synapsids would be reptiles, no great stretch of the imagination. In which case strict cladists would also need to call mammals reptiles too.

 

Also, as far as I know reptiles didn't strictly evolve from amphibians! I think it was a group that wouldn't quite fully identify with modern amphibians.

[delboy]

 

It kind of illustrates the point that all classification is slightly arbitrary. I was using the accepted classification that separates synapsids as non-reptiles (though my uninformed gut feeling is that they could easily be included). My understanding is that reptiles (to include anapsids and diapsids) are a good clade (if you include birds), unlike 'fish'. And dinosaurs evolved within that clade and mammals did not.

 

The main difference I have heard is that synapsids have alpha keratin in the skin and anapsids/diapsids/birds all have beta keratin.

 

 

 

 

Can you provide a citation for that last?

 

 

 

You've got me wondering now. I had thought I'd read it in Dawkins' Ancestor's Tale but I've looked in the likely bits and couldn't find it. So I Googled and it came up with a thread I started here! I said I'd just found a reference to it but I've now forgotten where that was!! Very annoying, it's bugging me now!

 

Was going through some old papers and found my reference!

 

https://www.researchgate.net/publication/227265191_How_to_Read_a_Phylogenetic_Tree p509

 

My mind can rest now!

[DrmDoc]

 

 

 

 

 

Was going through some old papers and found my reference!

 

https://www.researchgate.net/publication/227265191_How_to_Read_a_Phylogenetic_Tree p509

 

My mind can rest now!

 

Could you quote the related passage from your reference? From my understanding, alpha-keratin is indeed a mammalian distinction but not one we are currently able to determine relative to ancestral reptiles from the fossil record. Is it, perhaps, a hypothesized distinction considered probable based on separate, more solid anatomical links to mammals from the fossil record of ancestral synapsids; e.g., jawbone?