Re: Ornithoms, Parrots, and others

["John V Jackson" <jjackson@interalpha.co.uk>]

I think I've solved my exploding punctuation problem now!

--Original Message--From: Thomas R. Holtz, Jr. <th81@umail.umd.edu>Date: 10
November 1998 15:33


At 11:02 PM 11/9/98 -0000, John Jackson wrote:

>>It is through these differences that I believe a useful probabilistic test
of some kind might be made. Something ?very maniraptoran? did exist - it had
to, to give rise to Archae. However I predict that none of the types found
in the K will be found pre Archae.
<<

>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.
Frankly, I'm surprised you're willing to go for it.  Don't you have any
doubts?!  (Since you're going for the full house, you presumably can't have
access to any special knowledge of new finds.)  Unfortunately what is and
isn't a basal such and such will still be debatable.

>>Archae?s close ancestors will have been spinning off larger, non-arboreal
forms presumably, in the way George has described, and some of these will be
found. Perhaps the specimen Tom describes as maniraptoran was one of these
(though notice, it has not been possible to say for certain exactly which
type it belonged to ? ?probably troodont hips/legs? I believe).
<<

>I have yet to receive my copy of the Morrison Symposium volumes, in which
Padian has an update, but when Jensen & Padian described the fossil (a right
femur), they could not distinguish whether it was from an early bird or a
deinonychosaur, and so considered it simply as maniraptoran.  (Jensen, J. &
Padian, K. 1989. Small pterosaurs and dinosaurs from the Uncompahgre fauna
(Brushy Basin Member, Morrison Formation: ?Tithonian), Late Jurassic,
western Colorado.  J. Paleontology 63: 364-373).
<

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


>>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?  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!)

> 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?
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.

You'd be happy to see me publish it?!  Like heck you would!  But even if you
were, there'd be a dozen others who wouldn't.

>(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) . . . 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.


>>Tom said:
>
>>A ) Hooking and pulling is EXACTLY the type of "killing blow" proposed for
>the maniraptoriform hand by Gauthier & Padian: please read the paper. It
>has nothing to do with bear-like power slaps: it is simply a method to
>rapidly acquire the prey so that other parts (jaws, foot claws, etc.) can
>dispatch the prey.
>
>Why did eg _Deinonychus_ need relatively much longer and more powerful arms
>for catching its prey than say _Allosaurus_? And why did it need its
>shoulder joints so much nearer the backbone?
>>

>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?".


>"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.

>>(And why the backward pointing pubis and the stiff tail?)
<<

>Reorganization of the hindlimb musculature from a tail-driven to a
knee-driven system? Increased use of the tail as a dynamic stabilizer?
<

Again, comparitive, second-order justifications are what we want.

>>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.


>>Not just powerful enough to climb up onto the prey, in fact, if you
compare
the muscle attachment flanges on the humerus for _D_ with a human, who may
be able to pull himself up by his arms alone, there is an enormous extra
capacity.
<<


>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.  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.



On the phrase "killing blow", I will make an apology - principally for
putting you to the trouble of scanning those papers unnecessarily.  Although
I can't imagine making up that phrase - maybe I picked it up from somewhere
else - I don't know where it came from, maybe from our earlier emails on the
subject.  Anyway, I haven't found it used by them.

>As we have talked about (here and elsewhere), you seem to misunderstand
their hypothesis.  It is not a bear- or lion-like power slap that is being
invoked, but simply a rapid and extended predatory grasp.
<

Fair enough, at least that's one mistake they didn't make!


>Hope this helps.
<

Yes, it was useful, espec the refs.

JJ


Finally . . . some good advaice from the 1950's:

"Don't kill your wife with WORK!  Let Electricity do it!"