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Re: Ornithoms, Parrots, and others (long)



At 05:13 PM 11/11/98 -0000, John Jackson wrote:

>>I'll accept that prediction, and add in its stead that the next decade will
>likely see the following in Jurassic rocks: basal oviraptorosaurs, basal
>dromaeosaurs, basal bullatosaurs (if this remains a distinct clade within
>Maniraptoriformes: if not, both proto-troodonts and proto-ornithomimosaurs),
>and basal tyrannosaurids.
><
>
>Well, some might squeeze in post-Archae; pre-Archae is really the deal.

Sure, I'm game.  Replace "Jurassic" with "pre-Tithonian" in the above.

>Frankly, I'm surprised you're willing to go for it.  Don't you have any
>doubts?!

Sure, I have some doubts.  However, this is science we are talking about.
We make models, test them against the data, and are willing to abandon them
if new data support a different model.

>(Since you're going for the full house, you presumably can't have
>access to any special knowledge of new finds.)

I can't help knowing what I do or do not know.

>Unfortunately what is and
>isn't a basal such and such will still be debatable.

Well, of course.  Elementary evolutionary biology: taxa basal to known forms
in a group may lack some or the derived characters of the derived group.  As
such, it does make them harder to identify.  Still, my prediction is that
eventually forms belonging to each of those lineages (although very likely
outside the known members of each of these clades) will be found in
sediments older than the basal Tithonian.  Could I be wrong?  Damn straight
I could!  So what?

[With regards to the Dry Mesa maniraptoran]:

>Thanks for the ref.  If it might have been from an early bird it may have
>been quite small.

Indeed, it is about 6.5 cm long missing the distal condyles, probably less
than 9 cm long when complete.

>>>This clade will consist of creatures with feathers or feathered ancestors.
>I?m going to call its members "Pinnants", though for absurd and iniquitous
>reasons I would be prevented from publishing it "formally".
><<
>
>>Yeah, we know, everyone is out to get you, blah, blah, blah...
><
>
>Sorry - have I missed something?  Has someone ever been allowed to publish a
>paper on secondary flightlessness yet?  Never mind me - all the other 2F'ers
>are also too stupid and too ignorant EVER to be published on this topic are
>they?

Greg Paul has had these ideas published in the volume for the (3rd?)
Mesozoic Terrestrial Ecosystems Symposium, and I believe has a paper on that
subject in the volume on the Society of Avian Paleontology and Evolution
meeting (don't know when it is scheduled to come out: hopefully soon).
Perle, Chiappe, and colleagues discuss this subject with regards to
alvarezsaurids in Nature, Science, and elsewhere.  And, of course, numerous
papers have been published on the secondary flightlessness of birds.

>Incidentally, trying to suggest that someone has some kind of
>psychopathy is a despicable rhetorical ploy if it is untrue, particularly if
>the accused genuinely *is* being unfairly disadvantaged; and if it is true,
>it wouldn't seem to be a wise strategy for dealing with such people!  (And
>of course, just because you're paranoid, it doesn't mean they're not out to
>get you!)

Well, I do have to agree with the parenthetical comment, certainly!

Also, have you considered the possibility that it isn't the people but
rather the paper that has been judged and rejected?  Journal of Paleontology
was far from the first journal to which I submitted my initial theropod
phylogeny paper: it was rejected (and rightly so) because earlier
incarnations were not as rigorous as they could have been (i.e., the data,
as presented, did not support the conclusion).  Might this not be the reason
that we haven't seen more papers on the subject?

>> Of course,
>IF you had a new group to name which could clearly be distinguished as a
>distinct clade, then I'd be happy to see you publish it.  Do you? <
>
>When did defining a clade by a particular characteristic go out of fashion?

Mid-1990s.  Not to say that some don't still do this (witness
"Ceratopsomorpha" of Wolfe & Kirkland).  However, if it turns out that brow
horns derived independantly in _Zuniceratops_ than in Ceratopsidae, then
_Zuniceratops_ becomes the sole known member of Ceratopsomorpha, as it would
be the descendant of the first ceratopsian to evolve brow horns.  Same
problem I ran into with my original definition for Arctometatarsalia: see
Holtz (1996) for my efforts to repair it and the reason for doing so.

>If a member of a group has feathers it may be hard to distinguish, but it's
>still easier than guessing at its ancestry.  How can you say I don't have a
>new group to name?  It's got a name, it's got a char.  That's enough.

In the old days, sure.  How about one more item: a name, a char, and *an
analysis*?

>You'd be happy to see me publish it?!  Like heck you would!

And you gained telepathy when, exactly?

>But even if you were, there'd be a dozen others who wouldn't.

Screw 'em.  Present your evidence and your analysis, and let the chips fall
where they may.

>>(A word
>of interest: the clade defined as all descendants of the most recent common
>ancestor of _Oviraptor_ and Neornithes has not been formally (or at least
>properly) named, and almost all recent analyses show that this grouping
>(which also includes dromaeosaurids) IS pretty well supported and IS a
>distinct group from the more-inclusive Maniraptoriformes and MAY WELL be
>characterized by true feathers.  So, see, you can play the game the way
>others do, and still get your clade named!).
><
>
>Oh yes, it will be feathered alright, but it won't be *the* feathered clade;
>it will exclude enants and Archae amongst others. . . (it won't necessarily
>quite match my Uncinants either if that's of any interest) . . . 

Okay, now we can start discussing these things nice and systematically.  In
your opinion (analysis would be preferred, but I'll have to settle for
opinion), which of the following groupings most accurate reflects the
phylogeny in question:

(Oviraptor (Dromaeosaurs (Archie Neornithes)))
(Archie (Dromaeosaurs (Oviraptor Neornithes)))
((Archie Dromaeosaurs) (Oviraptor Neornithes)))
or some other possibility?

(Assuming here that Enantironithes are closer to Neornithes than they are to
oviraptorosaurs, dromaeosaurids, or _Archaeopteryx_).

>so it
>wouldn't surprise me if they *did* give it some feather related name!  I
>wouldn't be beyond enjoying seeing a clade named by me becoming established,
>few would, but there's no need to suggest that's what I'm all about.  My
>most important objective is correcting the unfair coverage of theories. And
>the whole point is, I and other 2F'ers are *not allowed to play the game* -
>just like at a restricted tennis club.  And I don't give a fig for any of
>those recent analyses if they involve esoteric cladistic operations.

As Henry Gee has recently pointed out on paleonet, cladistics has moved
systematics and evolutionary scenarios from the realm of after-dinner
discussion and into the realm of science.

Or, to use your own metaphor, you are not allowed to play the game, and you
don't give a fig about playing the game.  Do you see any logical problem here?

Furthermore, don't forget: Perle, Chiappe, and company ARE "2F'ers", at
least for alvarezsaurids, and their only convining evidence to that end is
found by playing the game.

>>Ah, good old fashioned "why" questions.  Come, come, please remember that
>the proper answer to "why" questions in evolutionary biology is "why not?".
><
>
>"Why not" would be an unnecessarily fatuous reply.  "Why" is simply
>shorthand for "What particular *overall* benefits, and under what
>circumstances, would lead to something evolving as opposed to it not
>evolving?".

These are two very different questions.

The answer to the latter is: Under what circumstances?  Under the
circumstances where among the variation in the ancestral population there
existed a form with a precursor version of the later form of this
adaptation; where this precursor form gave some slight advantage to the
possessor; where this precursor form was an inhertible trait; and where the
individuals who possessed this trait had a better than average chance of
surviving into the next generation than other members of the population.
Repeat over time.  (Darwin, 1859).

What particular overall benefits?  These are suggested below.

>>"What" questions, though, can at least be approached.  And "what advantage
>would a dromaeosaurid forelimb give over a more basal tetanurine forelimb?"
>How about: reach, while at the same time the ability to fold it against the
>body while not in use; speed of deployment; range of motion, particularly at
>the shoulder blade; and possibly for climbing.
><
>
>No.  This is not the question.  We know it would confer all those benefits.
>We are interested in why the benefits of the mutation outweighed the
>disadvantages enough to have evolved in these creatures and not others.

We might be interested in this question, but is it an answerable one?  How
do we test this?  It is difficult enough to do so in living taxa (where at
least we can observe differential sorting); it is nigh impossible for
extinct ones.

One thing we all have to realize: some questions which might interest us
(which tasted better: _Centrosaurus_ or _Styracosaurus_?) may be impossible
to answer.  That's life.

>>>The arms are very powerful ? too powerful for just holding the prey back.
><<
>
>>Too powerful?  In what way?  Add power to the system, and you can start
>incorporating additional items in the menu.
><
>
>And you can start starving to death in famines before anyone else if the
>benefits of carrying all that extra mass around don't match the cost.

And your evidence that the arms of dromaeosaurs are overmuscled is what?
Where are the morphometric data to back it up?  A hypothesis is fine, but
without data to back it up, it remains untested speculation.

>>Ooh, danger territory here.  Comparing primate and dinosaur forelimb and
>musculature can be VERY tricky: we are built in very different ways.  Yes,
>dromaeosaurs have much bigger deltapectoral crests than humans, no question.
>And exactly which groups of mammals HAVE big deltapectoral crests?
>Furthermore, our forelimbs have much greater rotational ability at more
>joints than a theropod forelimb.  We are both specialized in very different
>ways (but potentially for very similar reasons: among them, grasping and/or
>arboreal ancestry).
><
>
>Tricky - maybe.  You don't appear to trust either your or my educated
>intuition as to whether humans or droms have stronger arms.  I at least
>trust mine.  And before you say "No room for intuition anywhere in science",
>remember, I've done more thinking about thinking than you've done
>palaeontology.

Again, your telepathy kicks into high gear.  It must be great to know what
goes on in other people's minds, much less to have gathered the quantitative
data to make comaprative studies. ;-)

>But you don't need to know much biology or physics to know
>that all other things being equal, anchor points at the ends of muscles give
>a good idea of how big the muscles are.  And if "other things aren't equal"
>as you will no doubt immediately reply, they would have to be very much
>unequal, and in the wrong direction to outweigh the scale of difference we
>have here.

Without going on for too much (too late, I know), there are a couple of
different approaches to this question, if you want it to remain in the realm
of science.  One is the mechanical strength of the limb bones themselves:
that would be the easiest of all to do.  More difficult, however, is
determining relative muscle strength.  One of the big problems in this
particular case: the arrangement of muscles, even the particular muscles
used, are very different in mammals and in sauropsids.  You have a very
different arrangements of the particular angles and strengths to move the
lever system that is the arm.  Some other parts of the body might be a lot
easier to model, but relative muscle strength for climbing in the forelimb
of a dromaeosaurid and a hominid of the same body size is a pretty tough one.

>On the phrase "killing blow", I will make an apology - principally for
>putting you to the trouble of scanning those papers unnecessarily.

Actually, I had that particular volume out because I had recently made an
overhead of a figure in there: it wasn't too much trouble to find it.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661