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On 11-4-2010 13:08, clipka wrote:
> Am 11.04.2010 11:54, schrieb andrel:
>
>>> I don't think you can call them dinosaur eggs even technically. They
>>> are bird eggs, not dinosaur eggs. Even if birds are descendants if
>>> dinosaurs that doesn't mean birds *are* dinosaurs.
>>
>> Actually that is exactly what descending means here. Birds are a
>> subgroup of dinosaurs. It works the same as you and me being an ape, a
>> monkey, a mammal etc. Although I admit that there are many people that
>
> Put that way, all the meat you may be eating - whether it be ham, pork
> or even chicken - is actually... fish!
Not really. The name of the group that includes now-living fish as well
as reptiles, dinosaurs, reptiles etc. is vertrebrates. Fish is a strange
mix of all sorts of vertebrates that have two things in common. 1) they
live in water (or at least ...) 2) they have a common ancestor with us
earlier than the first vertebrate that got out of the water and became
the common ancestor of the tetrapods.
If there were still dinosaurs living other than birds we might have a
collective word that analogously describes dinosaurs except birds. As it
happens we don't have such a word because when we realized that birds
descent from other dinosaurs and we might need a word for the others we
knew what the family relation was.
But your remark was much funnier.
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On 04/11/2010 12:54 PM, andrel wrote:
> It works the same as you and me being an ape, a monkey, a mammal etc.
I don't think "it works the same". You are freely mixing up different
terms of biological classifications, namely a superfamily (apes), a
vernacular term which usually refers to a family ("old world monkey", a
family, or "new world monkey", which refers to a whole group of
families, the Platyrrhini) and a class (mammals).
In this classification humans and apes belong to the order of primates
(which is a higher taxonomic rank than superfamily). Thus according to
this classification humans and apes are primates, but that doesn't mean
that humans are apes (because they belong to different suborders).
Bird is a class which belongs to the subphylum vertebrata. Theropod is
a suborder which belongs to the class reptilia, which belongs to the
subphylum vertebrata.
In other words, according to this taxonomic classification, birds and
dinosaurs are both vertebrates, but that's where their relationship
ends, as birds belong to the class of aves while dinosaurs belong to the
class of reptiles.
This doesn't mean that birds did not evolve from theropods. It means
that birds are not dinosaurs because they do not belong even to the same
taxonomic class (aves vs. reptiles).
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On 04/11/2010 11:29 PM, Warp wrote:
> This doesn't mean that birds did not evolve from theropods. It means
> that birds are not dinosaurs because they do not belong even to the same
> taxonomic class (aves vs. reptiles).
Let me put that in another way. If birds were dinosaurs, then you
should be able to say:
"Birds are dinosaurs, and dinosaurs are reptiles, hence birds are
reptiles."
If birds were - indeed - dinosaurs, that *would* make them reptiles
because dinosaurs are classified as reptiles. However, birds are *not*
classified as reptiles. Hence birds are *not* dinosaurs.
Just because birds *evolved* from dinosaurs doesn't change that.
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Warp wrote:
> "Birds are dinosaurs, and dinosaurs are reptiles, hence birds are
> reptiles."
As far as I understand it, this statement is true by cladistic
definition, but the traditional terms reptiles and dinosaurs are
paraphyletic as they explicitely exclude the Aves. So, the only
reason we don't say this is because people originally thought
birds were descended from something else.
But there seems to be more dispute and more need to make the
distinction for dinosaurs according to Google hit counts:
"non-avian dinosaurs" -> 670.000
"non-avian reptiles" -> 23.000
I always learn something new here ;)
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On 11-4-2010 22:36, Warp wrote:
> On 04/11/2010 11:29 PM, Warp wrote:
>> This doesn't mean that birds did not evolve from theropods. It means
>> that birds are not dinosaurs because they do not belong even to the same
>> taxonomic class (aves vs. reptiles).
>
> Let me put that in another way. If birds were dinosaurs, then you
> should be able to say:
>
> "Birds are dinosaurs, and dinosaurs are reptiles, hence birds are
> reptiles."
See christian for a part of the answer. Though I disagree with him
agreeing with this logical fallacy. The correct version is
"Birds are dinosaurs, and dinosaurs (except birds) are reptiles, hence
(sorry no hence)."
> If birds were - indeed - dinosaurs, that *would* make them reptiles
> because dinosaurs are classified as reptiles. However, birds are *not*
> classified as reptiles. Hence birds are *not* dinosaurs.
A good example why paraphyletic groups are not a good idea. It leads to
logical inconsistencies like this.
> Just because birds *evolved* from dinosaurs doesn't change that.
No, but changing definitions of what a dinosaur is might. Actually, I
think the debate will go on for some time because the classification of
birds as something special is too logical for many people and the images
of dinosaurs with scaly hides are too widespread. Probably there will be
(and probably there already are) two 'definitions' of dinosaur. One
paraphyletic version in common use that won't include the birds and a
taxonomical that does, with the taxonomical slowly becoming more common
when also the children books incorporate it.
Twenty years ago you would have been correct, today a case could be made
for both opinions (though I think mine has the much stronger case).
Whether in another 20 years many people will still defend birds as being
a distinct class next to the reptiles and mammals I would doubt. Frankly
I think that by then even you have changed your opinion.
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On 04/12/2010 12:57 AM, Christian Froeschlin wrote:
> "non-avian dinosaurs" -> 670.000
I'm not exactly sure what you wanted to achieve with that search.
Birds evolved from theropods, which is a suborder of dinosaurs. Not all
dinosaurs were theropods, hence there are many "non-avian dinosaurs".
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> On 04/11/2010 11:29 PM, Warp wrote:
>> This doesn't mean that birds did not evolve from theropods. It means
>> that birds are not dinosaurs because they do not belong even to the same
>> taxonomic class (aves vs. reptiles).
>
> Let me put that in another way. If birds were dinosaurs, then you
> should be able to say:
>
> "Birds are dinosaurs, and dinosaurs are reptiles, hence birds are
> reptiles."
>
> If birds were - indeed - dinosaurs, that *would* make them reptiles
> because dinosaurs are classified as reptiles. However, birds are *not*
> classified as reptiles. Hence birds are *not* dinosaurs.
>
> Just because birds *evolved* from dinosaurs doesn't change that.
Dinosaurs are NOT reptiles!
There where reptiles during the dinosaurs era, and there where dinosaurs.
Peoples beleived that dinosaurs where reptiles initialy, but it was
proven that it's not the case.
We now know that dinosaurs where much closer to contemporary birds than
they ever where to reptiles.
They where very probably warm blooded, endotherm, or semi-endotherm,
while all reptiles are cold-blooded, or exotherm.
Also, the bone structure is very different than that of reptiles.
Alain
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"Alain" <aze### [at] qwerty org> schreef in bericht
news:4bc32318$1@news.povray.org...
> Dinosaurs are NOT reptiles!
> There where reptiles during the dinosaurs era, and there where dinosaurs.
>
> Peoples beleived that dinosaurs where reptiles initialy, but it was proven
> that it's not the case.
> We now know that dinosaurs where much closer to contemporary birds than
> they ever where to reptiles.
>
> They where very probably warm blooded, endotherm, or semi-endotherm, while
> all reptiles are cold-blooded, or exotherm.
>
> Also, the bone structure is very different than that of reptiles.
>
>
Some news from Berkeley. Not the latest, arguably, but still news... :-)
http://www.ucmp.berkeley.edu/diapsids/avians.html
Thomas
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On 04/12/2010 04:41 PM, Alain wrote:
> Also, the bone structure is very different than that of reptiles.
Dinosaurs are classified under the reptile subclass of diapsids
precisely because of the features of the skulls. Other diapsids include
crocodiles, lizards, snakes, etc.
The distinguishing feature of diapsids is that they have two holes in
each side of the skull, which birds don't have, and in fact, they have
quite a restructured skull compared to dinosaurs (although by modern
classification birds are still classified as diapsids because they have
evolved from ancient diapsids).
I'd say that claiming that "dinosaurs were closer to modern birds than
to reptiles" is quite a stretch (especially since there were types of
dinosaurs other than theropods; for example, compare the skeleton of a
stegosaur and see how much it looks like a modern bird).
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Warp wrote:
> I'm not exactly sure what you wanted to achieve with that search.
> Birds evolved from theropods, which is a suborder of dinosaurs. Not all
> dinosaurs were theropods, hence there are many "non-avian dinosaurs".
A non-avian dinosaur is a dinosaur which is not a bird.
Using that word combination only makes sense when the author
feels using the term dinosaur alone might include birds. So,
it is a measure of how many people think this.
In contrast, "non-avian monkey" gives no results ;)
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