Re: KT boundry event

uraniumcommittee@xxxxxxxxx wrote:

John Harshman wrote:
First of all, let's get this out of the way:

"The birdlike characteristics of the theropods that evolved prior to
birds did not appear all at once, and some were present before the
theropods themselves emerged-in the ear liest dinosaurs. For instance,
the immediate reptilian ancestor of dinosaurs was already bipedal and
upright in its stance (that is, it basically walked like a bird), and
it was small and carnivorous. Its hands, in common with those of early
birds, were free for grasping (although the hand still had five digits,
not the three found in all but the most basal theropods and in birds).
Also, the second finger was longest-not the third, as in other
reptiles."

Yes, that's all true. But note that it doesn't say birds evolved from
the earliest dinosaurs, except in so far as they also evolved from the
earliest chordates too. If that's what you meant, you have a very bad
way of stating it.

Scientific Amewrican Book of Dinosaurs, page 193.


uraniumcommittee@xxxxxxxxx wrote:


John Harshman wrote:


These characters are used by laymen to categorize groups.

Since when do we do taxonomy by public polling? If you want to decide
matters of science that way, then you should be a creationist.


Hardly. I know damned well what a 'bird' is and I know well what a
'dinosaur' is, and I know well they are not the same sort of thing.

You think you do. But your ideas seem to collapse under close
examination. So far you have given us no criteria that work, and the
ones you have given us are mutually contradictory.

No they don't. I can walk out on the street and demonstrate that I have
a full command of how to use the English word 'bird'.

You can use it on living species. But that seems to be all. If you
actually mean that no extinct species is a bird, you are at odds with
everyone else, including the average dude on the street. Mr. Average
Dude thinks that Archaeopteryx was a bird. And that's where the
contradictions start: you appeal to common usage but reject common usage.

No modern bird has teeth. Agreed?

Agreed, but so what?


Read my lips:

That

makes

them

different.

Different from what?

From their predecessors that may have had teeth.

What about their predecessors that didn't have teeth? And is the term
"toothed bird", commonly used in the scientific literature and popular
press, really nonsensical as required by your definition?

Not different from "dinosaurs", many of which (even
the non-bird ones) were toothless. Not different from Mesozoic birds,
many of which were toothless.


Yes. The group 'Dinosauria' includes more than the common term
'dinosaurs'.

So we're reduced to arguing the semantics of a vernacular term. Boring.

Well, I didn't start using the term 'dinosaurs' and say 'dinosaurs are
birds'. That's overly simplistic and false as such.

Nobody said dinosaurs are birds. We all said birds are dinosaurs. Do you
see the difference?

Of course. I also know it's semantically false. 'Birds' are 'birds' and
nothing else. Birds are not chimpanzees or cobras. They have ancestors
whth which they are not identical. I am not my father.

Wrong comparisons, every one. Are you a mammal? Are you an amniote? None
of what you say here is relevant. When you say that birds are birds and
nothing else, do you mean that birds aren't amniotes?

No, I mean that the term 'bird' is sufficient to do the job it is used
for: reference.

If that's what you mean, you are the least clear person in the world. So
you don't really mean that birds are birds and nothing else. They can be
vertebrates too. So why can't they be dinosaurs too? Because you say so?

Or vertebrates?
Because I think they are.

Anyone who is familair with the term 'bird' and with birds will know
that.

So you weren't serious when you said that birds are birds and nothing else.

Yes, the term as commonly used by non-scientists doesn't include birds.
But we try for a bit more technical language here on TO.

But that's not what I am complaining about.

What are you complaining about?

Using terms incorrectly. Misuse of language.

Oddly, that's what we were all complaining about you doing. Go figure.

Yes, you want to say 'birds are dinosaurs' and that's simply false.

Yet you have not been able to explain why.

Ancestors of birds originated among early dinosaurs, but that is not
the same thing as saying 'birds are dinosaurs'. They are linguistically
distinct statements.

Actually, they are cladistically identical statements, and cladistic
thinking should be encouraged. (Cladistics summed up in a sentence:
"Once a fish, always a fish.") I really don't understand why you're so
adamant on this point.

There are
advantages to cladistic thinking that you should definitely consider.
"Dinosaurs" as a group excluding birds is just an arbitrary collection
of species. If you include birds, though, it's a clade, a real
evolutionary entity. Including birds as dinosaurs can save you from
categorical mistakes like you indulged in at the start of this thread.

Birds are fish too, by the way. We're all fish. Just particularly weird
fish with a variety of bizarre adaptations to a terrestrial lifestyle.
If you think of it that way, evolutionary history becomes much more
compelling, in my opinion.

At some point, all such distinction arbitrary. Many find it useful to
distinguish birds from dinosuars. Distinction into classes based on
appearance is a useful feature of language, so that when I say the word
'Esquimaux' people don't think I am talking about Watusi. They picture
in their mind the dwellers of arctic regions, rather than of tropical
ones.

Same thing applies to 'polar bear' and 'tiger'.

All of which is irrelevant. Nobody says that eskimos are watusi, or that
polar bears are tigers. These are examples of disjunct groups. Birds and
dinosaurs are examples of nested groups.

Birds are current animals. Dinos are not. Some dinos were ancestors of
birds. Then birds evolved from those. That makes them different.

You seem incapable of doing anything to support your views other than
repeating them.

I'm trying to educate you about how to use English. I am not doing
science.

That much is clear. Nor, apparently, are you doing English. Your
definition is your own personal one. Nobody else uses it.

That's not what we call support around here. Not even if
you repeated them in all caps.

You seem not to understand the concept of 'anachronism'.

No, you don't. You aren't thinking clearly on this for some reason.

You have not been able to defend your
idea that birds are current animals (which would seem to deny that there
can be such a thing as an extinct bird).

No, it does not exclude that.

Then what's all that about anachronism? You understand that whatever
defining characters you pick, the difference between "bird" and
"non-bird" is an arbitrary division of a continuum, right? Evolutionary
transformations are gradual. Your division seems more arbitrary than
most, especially since we can't actually tell what it is so far. Your
ideas of "toothless" and "post K/T" are mutually contradictory, for example.

As for your second sentence,
nobody is daying that dinosaurs are birds, just that birds are
dinosaurs.

But that's simply false, even though Aves are part of the Dinosauria.
'Birds' are not 'Aves' and 'dinosaurs' are not 'Dinosauria'. NOW do you
understand?

I understand the difference. But why is is simply false that birds are
dinosaurs? "Simply false" seems to imply some objective standard of
difference, as if you don't understand the arbitrary nature of this
division.

Yes, some dinosaurs were ancestors of birds, just as some
mammals were ancestors of humans. You will note that you are still a
mammal nevertheless; and your parrot is still a dinosaur for the same
reasons. Are you different from a mammal?

See above.

Nothing above. You appeal to the colloquial, but you deny the colloquial
meaning of "bird", which includes Archaeopteryx. Nor do you explain why
it's not a good idea to include birds within dinosaurs.

What good does it do to say
that birds are not dinosaurs? In fact, it leads to false conclusions
about anatomy, behavior, and many other features.

It certainly does not.

Back that up with anything? It has led people in the past to claim that
dinosaurs couldn't have had feathers, for example, since feathers are
unique to birds. But of course feathers are widespread in theropods.

Agreed, and perfectly irrelevant.

It's an example of someone being led to a false conclusion about anatomy
because they said that birds aren't dinosaurs. Why irrelevant?

It is silly and pointless to reduce the number of distinctions.

It's not a case of reducing the number of distinctions, it's pointing
out that "birds are not dinosaurs" is an arbitrary distinction.

It's not any more arbitrary than the modern meaning of 'fish'. In the
past, 'fish'. could mean any water-dwelling creature.

But since the term "fish" is a colloquial term, it's hardly expected
to be precise. On the other hand, you've yet to tell me at what point
birds ceased being dinosaurs, and what you base that claim on.

'Dinosaurs' is likewise a colloquial term that is far from synonymous
with 'Dinosauria'.

'Dinosaurs'
'Birds'
'Fish'
'Snails'
'Slugs'
'Trilobites'
'Crabs'
'Insects'

Some of these groups are extinct, but all are colloquial terms.

Some of them correspond to actual clades, like birds, trilobites, slugs,
and insects. Others can easily be made into clades by including their
excluded subgroups: birds within dinosaurs, tetrapods within fish, slugs
within snails. Crabs are polyphyletic if you count everything with
"crab" in its name; can't do anything for you there.

Colloquial terms are not a good thing to use in discussions of science.
"Dinosaur" excluding birds defines a group with no real existence.

It includes Aptosaurus and T-Rex, Triceratops, etc. That's what people
think of when you use the word 'dinosaur'. For most purposes, that's
just fine.

If you're going by that scale, it also includes Dimetrodon and
Plesiosaurus. Why would you want to do that? Why accept the definitions
of a public that doesn't know and doesn't care much about the subject
over the definitions used by scientists? And why tell people here that
they are wrong when they use those definitions?

Scientists (good ones) don't use such imprecise terms as 'birds' or
'dinosaurs' and you know it. Those are colloquial terms.

Actually, scientists do use these terms.

They should stop doing that.

Why? Because you said so?

Maybe all the scientists who
use them aren't good ones. But if you're doing the grading, I'll reserve
judgment. I'm a scientist, and I use both terms. Does that mean I'm not
a good scientist? Sure, if you want precision, it's best to use a formal
taxonomic term. But usually the referent is clear from context.

I have already answered this, above.

You seem to be saying that there are no good scientists. Because I can't
think of anyone who doesn't use the term "bird" in scientific papers
when there is occasion to.

Birds
are NOT dinosaurs; they are birds. Dinos are all extinct.

Birds are *indeed* dinosaurs, just as primates are mammals.

'Dinsosaurs' are all extinct.

That's an arbitrary claim.



'Birds' (i'e., modern birds) are
descended from a larger class of ancient birds, most of which died out
in the Cretaceous. All modern birds, even flightless ones, are desended

from flying Cretaceous birds.

By the way, there is little evidence to suggest that most birds died out
in the Cretaceous (which I take to mean that the end-Cretaceous
extinction took a major toll on birds).

Not according to what I am reading.

The SA book, I suppose. What does it say? Who wrote it?

The stupid thing does not have an index! I read more than 200 pages so
far, so I cannot pinpoint where it is.

Sounds like something by Alan Feduccia. Did that help? Feduccia,
unfortunately, is given to making pronouncements without first bothering
to present evidence. You would like him.

The enantiornithines became
extinct, all toothed birds became extinct, and some neornithines
survived. But we have no clear idea how many species of each there were
at the time. It might be that only a few species became extinct, or
several thousand. No way to tell.



I agree completely.



Birds originated among the earliest
dinosaurs, all of which were bipedal.

That's a very unique assertion. Can you back it up with evidence?

See the SA book. I'm reading it right now.

For those of us who aren't reading it right now, you will have to say
what you mean. Birds, according to most modern accounts, are
maniraptorans, probably most closely related to dromaeosaurs, and these
are many nodes removed from the earliest dinosaurs. The fossil record
being what it is, we don't know just when birds first evolved. But a
good guess would be sometime in the Late Jurassic, around 70 million
years after the first dinosaurs.

That's what one article in the book says too. The problem is the
paucity in the fossil record.

So why did you say that birds originated among the earliest dinosaurs?

Got a better idea? The evidence is overwhelming.

You are ever so confused. The evidence is overwhelming that birds
originated among some of the later dinosaurs, around 70 million years or
so after the origin of dinosaurs, and after a vast amount of evolution
within dinosaurs. Birds are well nested within the tree of theropods.
You have to go through a dozen or more nodes in the tree of dinosaurs
before you get to any birds, by anyone's definition. What are you
talking about? Try quoting from your book, and give the author's name.
Either you are garbling this seriously, or the author is way outside the
scientific mainstream.

See the beginning of this post, page 193 of the SA book.

As I suspected, you have badly garbled what the author was saying. In
fact he's saying that "birdiness" evolved gradually, and that the
features that now serve to render living birds easily recognizable
evolved bit by bit starting with the earliest dinosaurs. Living birds
are easy to diagnose. But once you get into fossils this ability
disappears. As we would expect from evolution. Where in the lineage of
dinosaurs you want to attach the word "bird" is an arbitrary decision.

Now, there is a bit of argument about what you want to call a bird, and
over just when flight first evolved in theropods.

Let's use the term 'avians' or 'proto-avians'. Use of the term 'bird'
is imprecise and anachronistic.

Again with the anachronistic. If you want to do this in a rational way,
then what you want to do is restrict the term "bird" to the avian crown
group, which some call Neornithes and others just Aves. That's the
common ancestor of all living birds and all its descendants. Mind you,
that common ancestor lived at some unknown time in (almost certainly)
the Cretaceous, and there are plenty of Cretaceous "birds" by this
definition. But if you wanted to have your usage be meaningful, that's
what you would do.

However, you would then have seriously departed from the common usage of
the term, which was your only expressed justification. Common usage
includes all manner of non-neornithines, from Ichthyornis down through
Archaeopteryx. You would have to give a good reason for this redefinition.

Greg Paul puts the
evolution of flight much farther down the tree than most people do, but
still not among early dinosaurs. But of course you wouldn't call any of
those birds anyway, so it's unclear what you mean.


Doesn't that contradict what I just said? What does your book actually say?

See above.

I did.

.

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