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Re: begging behaviour among theropods



Original Message by StephanPickering@cs.com
Sunday, 15 December 2002 20:36

> Can you define "birds" without "dinosaur"? I don't think so.

I do think so. The definition of "bird" is "I know it when I see it". It's 
also possible to define "Aves" without mentioning or implying "Dinosauria". 
For example, if it's defined as {*Archaeopteryx lithographica* + *Passer 
domesticus*} (not that I liked that definition...), then this doesn't tell us 
if *A.* or *P.* are dinosaurs, and it is applicable regardless of whether 
they are dinosaurs or not. This continues: If you define "Dinosauria" as 
{*Triceratops horridus + Passer domesticus*}, then from this alone you can't 
possibly tell if Aves is a part of Dinosauria, the other way around, or if 
they are heterodefinitional synonyms. You need a phylogeny for that, the 
definitions won't tell you.

> "Bird" is a
> vernacular word, and, however popular throughout the centuries, its
> scientific definition is inseparable from Theropoda within Dinosauria, a
> case proven well over a decade ago.

I don't think there is, or should be, a scientific definition of "bird". Yes, 
I do think the scientific definition of "Aves" should describe as closely as 
possible the contents of "I know it when I see it", but that's still a 
different quality. Redde Caesari quae sunt Caesaris... :-)

> I still delight in Tom Holtz's
> description of them being "stump-tailed swell-brained flying
> theropods"...

So do I. :-)

> and, when you say "birds", your word remains nebulous

Sure. But for many purposes, including even lots on this list, it's clear 
enough. For those where a really transparent definition is needed* there 
is... hm... we should wait for "January 1, 200n" for a fixed definition of 
Aves. What's more, there are cases where a little fog is advantageous. A book 
called "The origin of birds" would discuss everything down to the origins of 
Theropoda, along with drawn-out affairs like the origins of flight, feathers 
and many more traits that can be seen in extant birds. "The origin of 
Avebrevicauda", however, would be a paper that searched for the sistergroup 
and maybe 2nd outgroup of Avebrevicauda, as well as describing & discussing 
the latter's oldest fossils.

* There are many such cases. Here I disagree with HP Philidor. And BTW, how 
can birds be "different from dinosaurs" when they are nested among the tiny 
twigs of the dinosaur tree? It's not like they were the sistergroup to all 
other dinosaurs.