Re: Strange thoughts on PN - was Re: BAD vs. BADD

[Martin Baeker <martin.baeker@tu-bs.de>]

> > But isn't it strange that, despite this list being frequented mostly
> > by stronge believers in PN + cladistics, it is still called the
> > "dinosaur mailing list", not the "non-avian dinosaur mailing list"?
> 
> Just last week we discussed neoavian phylogeny.

Sure, but we don't usually talk about sparrows, falcons, ducks etc.,
at least not for about 90% of our time, as we should according to the
number of species. (O.k., bad argument, we almost never talk about
ornithischians as well - this list is really the
extinct-theropod-list ;-))

> > And doesn't "The complete dinosaur"-book exclude birds almost
> > completely (so, according to PN, it excludes about 80-90% of
> > all dinosaurs and still calls itself "complete")
> 
> That was in 1997...

But even if the 2nd edition will discuss birds (as we learned from HP
Holtz' mail -- 2nd edition? When? Where? <drool>), will it cover living
birds to any extent? I doubt it.


> > And isn't it strange that it seems none of the PN-adherents here has
> > a problem with the notion "non-avian dinosaur", but can argue against
> > how arbitrary it would be to separate dinosaurs from birds?
> 
> "Non-avian dinosaur" is no different from "non-neornithean dinosaur" or
> "non-maniraptoran dinosaur".

Yes, so what? 

Everybody here agrees that group A=(Megalos.+Iguanodon) is useful, as
is B=(Passer+Archaeopteryx) - where () denotes MRCA - despite the fact
that these are also quite arbitrary - there will be a critter looking
*almost* like the first member of A that is not a member of it (like
Lagosuchus), but still, the concepts are useful, albeit arbitrary.

Why is then A\B (A without-B) such a big no-no? From the frequency we
hear "non-avian dinosaur", this gouping is *useful* for many purposes,
except, of course, when discussing phylogeny, so, what is *useful* may
get a name, at least a vernacular name.


> > Thought experiment: [...]
> 
> That's about species concepts, not about phylogenetic nomenclature ( = how to
> name clades).

Doesn't really matter - the thought experiment was meant more as an
analogy. So, if archaeopteryx had been wiped out and no birds had ever
evolved, what we now call non-avian dinosaurs (B/A, see above) would
be considered a useful and allowed group, but because archie did
survive, it is not? Although I do understand the logic behind it (I
hope), I still find it strange.

Don't get me wrong, I'm all for cladistics when it comes to revealing
phylogenetics. 

But if there are morphologically rather homogeneous groups (like
"families") that are rather distinct from others, I think they may
deserve a name. 

Who knows, 100 years from now, we may be able to quantify
morphological differences in some way, and then we can define
Hominidae as everything that does not differ by more than 20
Morphological Units from homo sapiens, and dinosaurs as anything that
does not differ more than 100 MU from Iguanodon, and, thus, somewhere
in theropoda, there would be a boundary line and everything above it
would not be a dinosaur anymore. Sure, that's also arbitrary
(boundaries would shift if we switched 100 to 105), but all groupings
are.  

Cheers,

Martin

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