Re: KT boundry event


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.

No modern bird has teeth. Agreed?

Agreed, but so what?

Read my lips:

That

makes

them

different.



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.

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.


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.

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.

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.

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 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.



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

.

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