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Re: Re: propaganda of the majority (very long)
>Here's a collection of snippets from our previous discussions on
>the dino-bird hypothesis. P.S. Thanks alot for your great comments.
>--- The wrist debate ---
>If you've seen Jurassic Park, you may remember the scene where they uncover
>a velociraptor skeleton and the ensuing quote: "look at that half-moon
>shaped bone in the wrist, no wonder these guys learned how to fly" (modern
>birds posess a similar half-moon bone in their wrists). Larry Martin would
>dispute that analysis on two counts, anatomy and functionality.
>- anatomy -
>According to John Ostrom, the half-moon bone in the wrist of deinonychus
>evolved from a certain bone(ulnare?) in more primitive diapsids.
Let me clear up this point. Identification of the homology of theropod
carpals to the basic amniote pattern is difficult (if not impossible) due to
the transformations of the theropod wrists even in primitive forms
(Herrerasaurus), and most especially in Maniraptora. The identification of
this bone as the ulnare or third distal carpal or whatever is very tenuous,
especially as theropods have lost/fused many of the carpals. Regardless of
which exact bone (its a guess both for fossil theropods and for birds),
maniraptorans (including birds) have a single carpal block which is the sole
proximal contact of metacarpals I and II and has a grooved, pulley-like
structure on its proximal side.
>Cladists tend to believe that this feature was passed on to birds from
>their theropod ancestor and persists in the wrists of all flying birds
>today. Larry Martin thinks that in birds, the half-moon bone evolved from
>a different bone(third distal carpal?). If Martin is right, it means
>that the half-moon bone is a convergent feature and implies separate
>lines of evolution.
Note that both Martin and Ostrom can be wrong here. There are two questions
to be answered:
1) Are the semilunate carpal blocks in theropods and birds homologous?
2) To what bones in the primitive amniote wrist are the semilunate carpal
blocks of birds and dinosaurs analogous?
The wrist morphology of Archaeopteryx is almost identical to
maniraptoran coelurosaurs, regardless of the condition in modern birds.
In any cladistic analysis these structures should be coded as the same
feature, and the distribution of this character determined after the
analysis used to determine homology or convergence.
>- functionality -
>Ostrom described the rotation of the wrist in deinonychus as an _inward_
>turning which would allow them to grab food and then put it in their mouth.
>Martin says that that would be of no use to a bird. Birds rotate their
>wrists _downward_ to tuck in their flight feathers and prevent them from
>dragging on the ground, a motion of no use to any theropod. Since both
>types of movements involve a rotation, half-moon shaped bones evolved to
>facilitate a swivel in the joint, but these bones evolved separately and
>for different purposes. They only _look_ alike, they do not represent an
>inherited character from dinos to birds.
Both are wrong on this point. Firstly, Martin's argument is vacuous - just
because a structure can be used in one direction during evolution does not
mean it cannot be modified. After all, our arms move in different
rotational directions than do those of more primitive mammals, but we
clearly evolved within Mammalia.
Secondly, as may workers have shown over the past few decades, the structure
of the forelimb of maniraptorans IS desgined for _downward_ motion. The
paw-like motion in which Martin, Ostrom, etc., believe maniraptoran wrists
work does not seem to fit the evidence. Instead, as D. Russell recently
alluded to, the hands of maniraptorans were probably used more like praying
mantises, rather than mammals. The claws were probably pointing inwards,
and the hands folded against the body when at rest, extended out to seize
>--- Arboreal(trees-down) vs Cursorial(ground-up) Origin of Flight ---
>Martin believes that the proto-bird ancestor was a small tree-dwelling
>reptile. Feather evolution involved the elongation of scales which would
>have increased mobility in tree-tree or tree-ground movements. Gliding
>would result in selection pressure for flight feathers(like Archaeopteryx),
>and eventually lead to fully powered flight.
>The "trees-down" scenario for flight origin has been hotly contested by the
>cladists, who favor a cursorial or "ground-up" theory of flight origins.
A quick note, Ostrom is no cladist, nor was Nopsca (one of the original
"ground-uppers". Also, don't conflate the two arguments. There is a debate
about the phylogenetic position of birds, and there is a debate about the
locomotory habits of the first birds and their ancestors. Both involve
different methods of analysis, although I admit most of the debators are
polarized into either a theropod-ground up or a nontheropod-tree down camp.
>Padian's scenario involves a small warm-blooded theropod already covered
>in feathers for insulation. Longer feathers evolve to assist in the capture
>of insects that this hypothetical creature pursued while running.
Actually, it was Ostrom who proposed the "insect net" theory, and he has
never strongly endorsed it. He just wanted to get yet another idea out
there for people to consider.
>Larry Martin doesn't like the cursorial theory. He says "It's hard to see
>what advantage you get from flying or gliding when your running because
>either activity will result in at least an initial loss of airspeed, which
>means if your pursued, you're more likely to be caught; and if your pursuing
>something, you're more likely not to catch it". He adds that ground-up
>flight would be too energetically expensive.
>When presented with these arguements, Padian responded "That would be true
>if we demanded that animals evolve all-out sustained flight all at once.
>If you have animals that run along the ground leaping and flapping and then
>getting back down to the ground and leaping and flapping, _that_ eliminates
>that difficulty because you get the question of evolutionary improvement
These comments miss the main argument of the cursorial hypothesis: the fact
the birds alone among flying/gliding vertebrates have forelimbs highly
transformed for flight, but hindlimbs still wholly adapted for terrestrial
locomotion. Bats, pterosaurs, flying lizards, flying frogs, flying
"lemurs", etc., all have wing/patagia on their hindlimbs, whereas birds
(including Archaeopteryx) have fully erect legs.
>- Was Archaeopteryx arboreal? -
>One thing nobody disputes is that Archaeopteryx could fly, due to the
>asymmetry of the vanes on either side of the feather shaft. This results
>in an airfoil contour which produces lift. When birds become flightless
>(e.g. Kiwi) they lose this feature. It's not something the evolutionary
>process will endow you with if you don't fly or glide. How well Archie
>could fly is another question. It lacked the large breastbone/coracoid
>feature found in modern birds and may have had trouble taking off from
Actually, the newest specimen of ARchaeopteryx does have a very good
>Archie also has wingclaws, similar to one modern bird, the hoatzin chick.
>Since the hoatzin uses it's wingclaws to climb around in the trees, it's
>reasonable to assume that Archie did the same.
Of course, the manual claws of Archaeopteryx are also identical to
dromaeosaurid, troodontid, elmisaurid, etc. theropods, which were probably
not arboreal (except perhaps as juveniles).
> This is not the only
>character of Archie that could be considered arboreal. Based on his
>(first ever) reconstruction of an Archie skeleton from actual cast bones,
>Martin has also concluded that it had a somewhat upright posture, more
>similar to a primate than a dinosaur. This would serve to keep the center
>of gravity close to a tree trunk while climbing. Alan Feduccia has recently
>published a study in which he concludes that the foot claws of Archie most
>resemble those of a perching bird.
Martin's reconstruction, although interesting, has its flaws. The most
serious is the problem that no one knowns that the joint surfaces between
the bones in Archie's skeleton looks like, as no one has prepared out all
the indivdual bones. Thus, since no one knows the exact articulation
between the bones, it is easy enough to reconstruct joints to fit either
scheme. Even if it did look like a primate, that would not disqualify
Archie as being a dinosaur-descendant - after all, primates don't look much
like the ancestral mammals anymore.
Feduccia's paper was very interesting. However, he did not include any
dinosaurs or other non-avains in his study. To see the results of what does
happen when you add other claws into the analysis, wuo'll have to wait until
this year's Society of Vert Paleo meeting...
>- So why would do many cladists refuse to accept the notion of an arboreal
> origin of flight? -
Not all of them do. Rick Vasquez, a fellow Yalie and avian anatomist, has
gotten into arguements with Ostrom over Rick's belief in an arobreal
origin. Nevertheless, he is a cladist (in that he uses cladistics for
>Here's a quote from Padian: "Climbing trees does not seem to be something
>they (i.e. theropods) did very well...When you look at the anatomy of Archie
>and the creatures to which it is closely related, you find that there isn't
>a single arboreal character in the skeletons...There is no evidence that
>birds really spent much time in the trees at all before the Tertiary
>sometime, after the age of dinos".
Greg Paul, of course, believes that many small theropoods could have been
arboreal, and I think he may be correct in this opinion.
>[comment - Padian may have been so seduced by his cladistic models that he
>ignores important evidence and misses this one by about 100 million years.
>While he's essentially correct that theropods were built for a running,
>terrestrial lifestyle, he seems to totally ignore arboreal characters
>of Archie, and his imposing his expectation of a running theropod as a
No comment-Kevin can speak for himself on this one.
[sever paragraphs deleted - concern Feduccia's analysis addressed above]
>With respect to the dinosaurian origin of birds, Feduccia says:
>"If Archaeopteryx lived in trees, it means that it evolved not from
>dinosaurs as most paleontologists currently believe, but from some
>tree-dwelling reptile, since dinosaurs lived on land and not in trees".
It's good to know that Alan knows the whole of dinosaurian diversity, since
those of us who work on them still find strange new morphotypes every few
>Stan Friesen wrote:
>>I don't know, since those results you mentioned are all very recent
>>are you sure the non-arobreal theory still has many adherents?
>They haven't thrown in the towel yet, although Ostrom is softening
>up a bit. He says "I think Alan has put together a very solidly based
>study. I'm not set in concrete." (from Science News, Feb 6, 1993)
>I can't find a reference at the moment but I recall either Padian or
>Gauthier coming out swinging against Feduccia's paper last year.
They're not. As I said, wait for SVP...
>I totally agree with this. The main point I've been driving at with
>this whole thread is that you can't ignore evidence because it conflicts
>with your preconceived ideas. I didn't mean to suggest that cladism
>is to blame, actually I think cladistic studies are useful. It's what
>you do with the information that counts. The "cladists" in this example
>thought they could use their model to infer something beyond it's
>scope. They ended up endorsing a cursorial origin of flight, something
>that required that they ignore hoatzin-like wingclaws, upright posture,
>flight feathers, and now perching-type footclaws in Archie. They also
>concocted some _very_ implausible scenarios for getting a running animal
>to evolve flight feathers. Padian's position is not due to cladism, but
>rather the over-reaching conclusions he draws from his cladistic model
>and his disregard for contradictory evidence.
You might add that some proponents of the nondinosaurian origin hypothesis
reject cladistic methodlogy since they continually support the therood
>Stan Friesen wrote:
>>And, until Feduccia published his study there was little evidence
>>that the footclaws were perching-type claws. These things are not
>>as easily determined as it might seem to the outsider. I had to
>>read Feduccia's article before I could evaluate the evidence,
>>and despite Padian's opposition, I found his evidence quite strong.
>>Again, just because Martin and Feduccia's gut feeling has now been
>>largely vindicated does not make the non-arboreal idea retroactively
>>unreasonable. It is unreasonable *now*, but it was not so before.
>Hmmm...Tell me Stan....Did you....ahem...buy into the cursorial theory...
>..for maybe just a little while at some point?
Hmmm...You might tell me...Do you...ahem...cling onto any study that
supports the arboreal hypothesis, even if it is inadequate? :-)
>If one were to consider the possibility that Archie wingclaws were
>vestigial, the fact that Pterosaurs were known flyer/gliders with
>wingclaws should have sounded an alarm bell. Besides, Archie wingclaws
>seem far too articulated to be merely a vestigial trait. They were are
>highly curved and the fossils show that they had extremely sharp
>points. The toe claws are less curved, but were also sharply pointed,
>ideal for climbing up tree trunks.
Note that there are things which an animal might want to grab onto other
than trees (i.e., why do dromaeosaurids, et al., have manual claws identical
>[relevant facts] - Birds that live on the ground and run on two legs
>have _no_ wingclaws and have _very_ worn toeclaws. All of the toeclaws
>on Archie fossils are very sharp.
And only one species out of thousands of extant birds has wingclaws. I do
grant that the toeclaws are interesting.
>The most accurate skeletal reconstruction ever done by a scientist
>was done by Larry Martin. He discovered that Archie seems to have had
>a primate-like, upright posture. It should be noted that this came as
>a surprise to him at the time, as all restorations he had published
>prior to this study used the more traditional theropod-like posture.
>The upright posture is an arboreal character in Archie just like it
>is in tree-dwelling primates.
See comments above concerning this restoration.
>* Flight Feathers
>This is the _best_ evidence for arboreal lifestyle, as there is simply
>no other plausible explanation for the origin flight in birds. When
>the first wing membrane of a Pterosaur was found, it was immediately
>cited as an arboreal character and remains so to this day. Nobody has
>ever suggested that pterosaurs evolved flight by running and flapping
>along the ground.
Don't you ever READ Padian's stuff, or do you just automatically gainsay
him? Switch "Kevin Padian" for "Nobody" in the above sentence, and it reads
>The same arguement applies to Archie with respect to flight feathers.
>The arboreal arguement can be traced to G. Heilmann(1926) and was actually
>considered the "conventional" theory until Ostrom (1970's). I believe that
>the misinterpretation of cladistic analysis by Padain et al was the primary
>cause of the mass-hallucination that was the cursorial theory. Although
>they cornered the market on _quantity_ of evidence, they were somewhat
>lackluster on _quality_ of evidence. All of these cladists have contributed
>greatly to our knowledge of natural history, I don't mean to demean them
>in any way. I do predict that the cursorial theory will be to them in
>posterity what the cosmological constant is to Einstein.
>* And now we have the latest Feduccia study...
And more to come...
>Mickey Rowe wrote:
>>Yes, in fact (and I'm saying these things only to see if Stan will
>>shoot them down :-) couldn't it be possible that a) the semi-lunate
>>bone in the wrist of _Deinonychus_ would allow it more mobility in the
>>hand in order to allow it to grab onto branches at odd angles and b)
>>the "terrible claw" on the toe of _Deinonycchus_ and other theropods
>>could have been used to grab onto tree trunks like the spikes in a
>>telephone repairman's boots? How difficult would it be to reconcile
>>such a scenario with the orientation of the back-bone and tail as the
>>animal(s) attempted to climb?
>I think that's a great idea, especially the repair man's boots analogy.
>A good friend of mine works for the power company and I have tried
>those boots. While talking to John Fischner in front of his full-
>sized velociraptor sculpture in Tucson, we concluded that a raptor
>could have gone right up a tree and probably get up as fast as just
>about anything. The problem would arise when trying to maneuver in
>the branches with a broomstick sticking out the butt :-)
>(ossified tendons- stiff tail)
Actually, Phil Currie is working on sme of these ideas. An important point
with the last comment - Archie's tail is similary rigid, best seen in the
newest specimen. If the rigid tail of dromaeosaurids is reason to reject
their arboreality, than it should reject it for Archie.
By the way, I'm not wholly converted one way or the other to
cursoriality/arboreality. Nevertheless, I've had to seek to undo disservice
done to the cursorial arguments by rigidly-arboreal theorists. Hope these
comments are useful, and I appologize for their length.
Thomas R. HOLTZ
Vertebrate Paleontologist, Dept. of Geology