Birds and Dinosaurs

[Badly Shaved Monkey]

Another palaeontological question...

We now accept that birds descended directly from dinosaurs, but are birds actually dinosaurs? What I mean is that, with modern animated reconstructions, it is very easy to see dinosaurs as very birdlike, but if birds are not dinosaurs what are the taxonomic features that means they are a different class?

As a side issue, I know that some of the business of trying to refute the dinosaurian origins of birds involved a debate about the digits that birds retain from the basic pentadactyl model versus the digits that dinosaurs retain. How was this particular question resolved?

 

[Soapy Sam]

Are humans actually fish?

These are labels. If they are useful to you, then use them.

(Sorry- I know this looks like obscurantism, but I truly don't mean it that way. There is nature and how humans divide it up. The map is useful, but not to be confused with the terrain.)

For me, no. Birds are birds. But think how a blackbird looks, to a worm...

 

[El_Spectre]

Another palaeontological question...

We now accept that birds descended directly from dinosaurs, but are birds actually dinosaurs? What I mean is that, with modern animated reconstructions, it is very easy to see dinosaurs as very birdlike, but if birds are not dinosaurs what are the taxonomic features that means they are a different class?

As a side issue, I know that some of the business of trying to refute the dinosaurian origins of birds involved a debate about the digits that birds retain from the basic pentadactyl model versus the digits that dinosaurs retain. How was this particular question resolved?

The question of species (or more broadly, class) gets muddled over time. To wit, humans are distantly descended from proto-fish (then amphibians, reptile-mammals, etc). So are we amphibians? It's the same kinda question.

Dawkins (in TBW) basically said definitions of species are only really meaningful at a given point in time, and I'd tend to agree.

edited to fix a misspelling of Prof. Dawkins name

 

[Eos of the Eons]

Dinosaurs were reptiles, but not all reptiles are/were dinosaurs. Birds are not even reptiles (they are Aves).

Modern birds continued to diversify through the Cenozoic. The Cenozoic bird fossil record consists largely of isolated bones (although some nearly complete skeletons have been recovered from certain localities). Suffice it to say that by the early Oligocene, 35 million years ago, most of the bird orders that we recognize today had appeared.

http://www.ucmp.berkeley.edu/diapsids/birds/birdfr.html

Birds are believed to be extant members of a group of dinosaurs called maniraptors

http://www.factmonster.com/ce6/sci/A0807642.html

 

[Eos of the Eons]

As a side issue, I know that some of the business of trying to refute the dinosaurian origins of birds involved a debate about the digits that birds retain from the basic pentadactyl model versus the digits that dinosaurs retain. How was this particular question resolved?

Digits? Can you clarify the details?

 

[drkitten]

Re: Re: Birds and Dinosaurs

The question of species (or more broadly, class) gets muddled over time. To wit, humans are distantly descended from proto-fish (then amphibians, reptile-mammals, etc). So are we amphibians? It's the same kinda question.

I think you're making this problem more difficult than it needs to be; it's only really a problem if you insist on a strictly cladistic definition of taxonomic categories.

Which is to say, I can easily define "apes" as (IIRC) Hominidae, and I can look in my handy-dandy taxonomic encyclopedia for the characteristics that all Hominidae share.

Monkeys, on the other hand, have no clear-cut taxonomic category; there's not a single family or class or order that defines monkeys. I can, however, define "monkeys" as "all the primates except for Hominidae," which in turn gives me a set of features that all monkeys have (that they share with the apes), and a set of features that make monkeys different from apes.

We're not amphibians, because amphibians are defined, broadly, as all gill-less air-breathing vertebrates that aren't amnionites (sp?) (aka repties, birds, or mammals). (See the taxonomic encyclopedia for full details.)

Unfortunately, I don't know what the taxonomic details are offhand that distinguish birds from dinosaurs....

 

[Badly Shaved Monkey]

Re: Re: Birds and Dinosaurs

The question of species (or more broadly, class) gets muddled over time. To wit, humans are distantly descended from proto-fish (then amphibians, reptile-mammals, etc). So are we amphibians? It's the same kinda question.

No, not really. We are evidently different from fish in many ways, but now it is clear that birds are descended from dinosaurs, it is not immediately obvious that birds are not just the dinosaurs that have survived to the present day.

 

[Neutiquam Erro]

Re: Re: Re: Birds and Dinosaurs

No, not really. We are evidently different from fish in many ways, but now it is clear that birds are descended from dinosaurs, it is not immediately obvious that birds are not just the dinosaurs that have survived to the present day.

Surely, any "dinosaurs" that survived to the present day would still be dinosaurs. If birds evolved from dinosaurs, wouldn't that mean that they are not dinosaurs any more?

 

[Badly Shaved Monkey]

Re: Re: Birds and Dinosaurs

Digits? Can you clarify the details?

ttp://www.msnbc.com/news/118914.asp?cp1=1

http://www.godandscience.org/evolution/dinobird.html

http://www.devbio.com/article.php?ch=16&id=161

All the top Google hits are this sort of stuff featuring Feduccia and none have a rebuttal to his argument.

But here is an hypothesis;

http://www.talkorigins.org/faqs/dinosaur/bird_and_frog_development.html

Should've Googled instead of starting this thread.

 

[El_Spectre]

Re: Re: Re: Birds and Dinosaurs

I think you're making this problem more difficult than it needs to be

[snip]

I'm good at that You are right, I was intentionally being hyperbolic to make the point that "we are that which we are descended from" isn't really tenable or especially useful.

I considered "are we all microbes", but that might be too far

 

[Badly Shaved Monkey]

Re: Re: Re: Re: Birds and Dinosaurs

Surely, any "dinosaurs" that survived to the present day would still be dinosaurs. If birds evolved from dinosaurs, wouldn't that mean that they are not dinosaurs any more?

I don't know, that's what I'm asking.

 

[El_Spectre]

Re: Re: Re: Re: Re: Birds and Dinosaurs

I don't know, that's what I'm asking.

It's a really fluid thing... consider the early hominids... they were progressing down the road to us, but also had ape-ish characteristics. Where's the dividing line?

For that matter, where's the transition between true reptiles and dinosaurs (it's an old debate, I know... but dinos did some really unusual things for reptiles)?

How about this: Birds are as much dinosaurs as we are tiny shrew-like mammal ?

 

[fishbob]

We now accept that birds descended directly from dinosaurs, but are birds actually dinosaurs? What I mean is that, with modern animated reconstructions, it is very easy to see dinosaurs as very birdlike, but if birds are not dinosaurs what are the taxonomic features that means they are a different class?

Classification distinctions are somewhat flexible, so it depends on your purpose. Way back when I was a paleo student, I was taught that there are 2 types of paleontologists - lumpers and splitters.

Lumpers like to throw related critters into a single bigger group.
Splitters like to pick out minute differences between related critters.

If you need to do biostratigraphic age dating on sedimentary rocks in a region, splitting is more useful. If you need to understand depositional environments, lumping can be more useful.

 

[hammegk]

Re: Re: Re: Re: Birds and Dinosaurs

I considered "are we all microbes", but that might be too far

Yeah. More likely one per baramin.

 

[Soapy Sam]

BSM - As a person who deals with animals, you are probably horrified that folk like Fishbob- who really is a geologist and I (who just pretend to be), really don't give much of a hoot about this. Only vertebrate palaeontologists and small boys really care about dinosaurs anyway. They're not much actual use.

As he says, fossils are useful for relative dating or environment reconstruction and getting kids into museums. Other than that, they're a damn nuisance that spoil perfectly good rocks.

There have been increasing rumblings for several years about this issue. I spoke to a palaeontologist about two years or so ago who felt the balance of evidence was swinging towards the "common stock" rather than "direct lineage" view then. I rather got the impression it's one of those ideas which is just quietly taking over as a new generation of palaeontologists replaces the Bakkers and Horners and their ilk - who long ago ceased to be " enfants terribles" and became establishment.

Interesting links. I had not seen those.

 

[DangerousBeliefs]

Didn't I just read something that we may have to completely rethink how dinosaurs looked because they've discovered that dinosaurs were... COVERED IN FEATHERS... not just a few species but apparently many of them.

Can you imagine being chased by a T-Rex with bright yellow feathers?

http://www.timesonline.co.uk/article/0,,2087-1764136,00.html

Some theropod (“beast-footed”) dinosaurs were preserved complete with feathery plumage. Theropod is the name given to predatory creatures that walked upright on two legs, balanced by a long tail.

 

[Badly Shaved Monkey]

Didn't I just read something that we may have to completely rethink how dinosaurs looked because they've discovered that dinosaurs were... COVERED IN FEATHERS... not just a few species but apparently many of them.

That's kinda my point. Being feathery was one of the defining features of being a bird not a dinosaur. The question of my OP turns on whether there is much left that still distinguishes birds from dinosaurs at the taxonomic Class level.

 

[fishbob]

That's kinda my point. Being feathery was one of the defining features of being a bird not a dinosaur. The question of my OP turns on whether there is much left that still distinguishes birds from dinosaurs at the taxonomic Class level.

Those big honking teeth are not features that birds are known for, and dinos did not have much in the way of beaks. There are similarities, but there are pretty obvious differences too.

 

[mummymonkey]

Yes that whole teeth/beak thing springs to mind. The tail is reduced to a parson's nose on birds also. I'm sure there are other differences that keep taxonomists gainfully employed.

 

[Badly Shaved Monkey]

Hence the phrase 'as rare as hen's teeth'.

It's all right, I'll shut the door behind me.