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Re: polarity of bipedality in dinosaurs (real long--TOO long)



At 12:01 AM 9/24/96 -0400, George Olshevsky wrote:
[I respond to the Olshevsky posting with "{*" to further confuse the issue...]

[Alright, both of you... start summarizing text.  If I were going to
 be hard-nosed about quoting I'd have spiked this message for
 including too much previous material.  I am removing some of it. -- MR ]

>)) Heck, you're right there at Texas Tech. You can go right to the
>)) collections and handle the type material of _Postosuchus_ without
>)) even having to drive to a different city!

{*        And examine I will as soon as I can get up the nerve to ask Dr.
{* Chatterjee to let me play with his most expensive toys.

>)) Fly _Longisquama_ did not; but >glide< it probably could. Every paper
>)) on this creature suggests that it was a glider of some kind. 

{*        I meant fly like an eagle...

>        So certain are you that Protoavis is a chimera?
>)) As I just said, you're there at Texas Tech. Why not drop in on Sankar
>)) and ask to see the specimens? 

{*        Once again, when I get up the courage to go walking on thin ice, I
{* certainly will.  I am fully aware that Protoavis fits well into your
{* theory, I'm just shocked to hear that sort of gaurded statement from you. 

> The major point I keep trying to make is that BCF is a single,
> unified theory that >explains< the existence in dinosaurs,
> particularly theropods,
       The one thing I have seen consitantly throughout the best, longest
lasting, most robust theories is that they don't explain everything at once.

>)) And you are incredibly off base here! The best, longest-lasting, most
>)) robust theories are PRECISELY those that explain many seemingly discon-
>)) nected observations within one framework.

{*        Don't patronize me, George.  I said they don't explain everything
{* at once.  Your theory, admittedly at a smaller scale, takes it all in, and
{* spits out an affirmative response to every new piece of evidence.  Why?
{* Because weaknesses in the fossil record are it's strengths, and it's main
{* action takes place behind the scenes in a place from whence no fossils will
{* come.  While it is couched in modern evolutionary terms, it's about as
{* proveable as Hoyle's Panspermia (is that the right word?) Genes from Space
{* theory.

>)) To name a few: Newtonian mechanics and the Newtonian theory of
>)) gravitation, which ascribed one cause to the motions of all massive
>)) objects from apples to planets

{*        But could not explain the effect of gravitation on light.

>)) Darwinian evolution, which ascribed the manifold diversity of
>)) life on earth to the single phenomenon of natural selection;

{*        Did not seek to explain everything about natural selection, nor
{* the actual mechanisms by which natural selection operated on the phenotype.

>))Maxwell's equations of electromagnetism, which unified all
>)) electrical and magnetic phenomena into a single theory;

{*        But missed the weak force.

>))the atomic theory of matter, which describes the macroscopic
>)) properties of matter solely in terms of the interactions among atoms;

{*        And believed that each atom was an undividable things until
{* whomever it was (don't anyone bother telling me, I've taken Chem enough
{* times) zapped Gold foil with alpha particles. [Rutherford.
   Couldn't resist. -- MR ]

>)) continental drift, which describes the earth's geology solely in terms of
>)) the unifying concept of moving continents;

{*        Can't recall, but I believe that this didn't include the mechanism
{* of plate techtonics, which was seperate.

>)) the kinetic theory of gases; Einstein's theory of relativity

{*       Does not explain why I can type faster than the speed of light to
{* respond to one of your posts.

>)) ; quantum theory; the standard model of particle physics; the Big
>)) Bang theory of the origin of the universe;

{*        Needs to be amended once they decide what the universe will do in
{* the "end".

>)) Kepler's laws of planetary motion

{*        Generalisations, If I'm not mistaken, of physics.

{*        ("You're one breath away, George; Newton, Einstein, Surak...")
{*       The theories you mentioned above did not come into being as full
{* fledged theories, answering all quesitons in a neat little package.  I have
{* noted where each of them (with a few exceptions which I admit to being
{* too tired to tackle) have grown beyond their origional scope.
{*        That long paragraph on a relatively minor point seems to blow this
{* entire question way out of important.  BCF is an interesting theory, but
{* it is certainly not as important as any of those mentioned above, and
{* seems to have fewer loose ends than some of them.

>))There >must< have been a tremendous amount of evolutionary
>)) experimentation going on among the dino-birds as they became ever
>)) more perfectly adapted to living in trees, gliding, and flying.

{*      And that group was the dinosaurs.

>)) did they lose the outer two or three digits? The BCF answer is that the
>)) hand started to evolve into a wing and lost its outer digits before the
>)) three-fingered theropods descended from the trees.

{* WHY?  Bats have five fingers on the wing, Pterodactyls have, I
{* believe, four, flying squirrels have whatever squirrels have.  It's a
{* chicken and the egg thing, really.  I can see no reason for reducing
{* the number of fingers which can't be turned back on itself.

>>Bipedality and forelimb reduction in theropods
>        See Tom Holtz's recent post on "forelimb" reduction.  Personally, I
>can't see why a bird would want *smaller* forelimbs, anyway.

>)) Whether the bird "wants" smaller forelimbs is not the issue. Whenever

{*      Yawn...  Yes, yes, yes, we've all taken Bio 202...

>)) of avian wings. This pattern extends naturally and automatically
>)) to the earliest ground-dwelling, flightless birds, namely, the
>)) theropods. Only in theropods, the wings still had claws and still
>)) had a grasping function--and these anatomical characters and
>)) functions exapted naturally into a highly predatory lifestyle.

{*  Which then doesn't explain _why_they_were_reduced...

>bipedality, how many flying tetrapod forms are bipedal?  1+1/2 (I count
>pterosaurs as 1/2).  That's half of the total, not counting the numerous
>quadrapedal gliders.  How many bipedal tetrapods are flying?  1+1/2.  If my
>calculations are close, and I don't count the aussie frilled-lizard, that's
>about 1/3rd of the total (kangaroo-forms and primates and a half a
>pterodatcyl are the others).  You haven't yet proved this point.

>)) There are some 9000 species of flying bipeds alive today. If you're not
>)) talking about these, I don't know what you're talking about.

{*      I was counting Seperate Evolutionary Events Which Resulted In Flying
{* Tetrapods.    Birds count as one.  Got any others?

>)) I wish someone had called it "Cope's Suggestion" rather than "Cope's Rule."

{*  Then perhaps it isn't such good evidence...

>)) Rule." Of course I know about dwarfism, and there was even a time when I
>)) imagined that theropods somehow underwent an extensive period of dwarf
>)) evolution on their way to becoming birds. But I could not imagine twenty
>)) million years of unmitigated island endemism or any other factors that

{*  Evolution often challenges even the most robust imagination to stretch far
{*  beyond it's well worn rows.  "There are more things in heaven and earth..."

>)) dino-bird descendants. It also gave the dino-birds more time in which to
>)) evolve feathers, flight, etc., all difficult evolutionary steps.

{*  Given enough selection pressure, it won't take much time...

>)) Hollow bones are a hallmark of many (though, of course, not all) tree-
>)) dwelling and other acronomic vertebrates, from frogs (as Larry Martin
>)) pointed out to me once) to birds. Hollow bones lighten a skeleton and help
>)) the buoyancy of air to mitigate the effects of a fall. They are a natural
[...]

{*     Ok, this is interesting.  Still only puts forth the possibility of an
{* arboreal stage.  Besides, why did some smaller dinos keep the hollow bones?
{* Obviously, at least some dinosaurs reversed this feature...

>)) In BCF, the stiffened tail of theropods is exapted from its original
>)) use as an airfoil to help the falling arboreal archosaur to stabilize
>)) itself during the fall and to direct itself to a safer landing place.
>)) Later dino-birds used the tail as a true airfoil for stability during
>)) long, unpowered glides.

{*        But see Larry Martin saying that Archy's stiff tail made it LESS
{* maneuverable...  "BADD" has an equally or more parsimonious conclusion.

>)) In BCF, the giant claws of theropods were exapted for a predatory
>)) lifestyle from their humble origin as grasping organs for clinging
>)) to trees: another solution to the falling problem. As Feduccia has
>)) pointed out (no pun in- tended), oversize, sharply pointed, highly
>)) curved claws characterize many tree-dwelling birds. Such claws are
>)) observed in _Megalancosaurus_ and other drepanosaurids, and are a
>)) prime reason for assuming arboreality in these forms.

{*  Sorry, I agree that big claws make for fn tree-climbing, but there just
{* isn't anything here that is "ad hoc" or inadequitely explained in "BADD".

>)) _Lesothosaurus_ was an ornithischian not closely related to the theropod

{*      Really?

>)) In BCF, the maniraptoran forelimb evolved as an improvement to a forelimb
>)) already functioning as a primitive wing. The maniraptoran forelimb is
>)) anatomically restricted in its ability to grasp and move--a sacrifice
>)) evolutionarily selected for because it made the forelimb easier to flap--
>)) a method of making the forelimb musculature more efficient for flying.
>)) This forelimb and its "power stroke," or primitive wingbeat, were exapted
>)) into a kind of killing stroke for predation in the flightless maniraptoran
>)) theropods.

{*        Chicken or the egg, chicken or the egg...  Your still trying to
{* push a decent phylogeny up hill.  I don't think that this is impossible,
{* it just isn't as simple an explanation as the current one we have.

>>Retroverted hallux of most theropods
>        Most?  I was not aware that it was in most.  I was aware that this
>occurred in dromaeosaurids and not in troodontids, indet. in ornithomimids,
>?in Oviraporoids, not in therizinosauroids, I haven't heard of it outside of
>the coelurosaurs, but you're welcome to enlighten me.

>)) In the foot of theropods at or above the ceratosaurian grade, the hallux
>)) articulates into a groove low down on the back of the second metatarsal.

{* Except for the groups I mentioned above, all of which seem to
{* cluster in the advanced "dinobird" zone.  The only coelurosaurs I can
{* name off the bat for which this isn't true are, guess who,
{* Archaeopteryx and the Dromaeosaurs.  Someone do pipe up if this is
{* wrong...

>)) I call this position "retroverted." In BADD theory, the first metatarsal
>)) is considered to have migrated to the back of the foot, lost its proximal
>)) end, and become reduced in size all for the vague reason that it was not
>)) needed in theropod locomotion. If it was not needed, or if it hampered
>)) theropod locomotion, why did it not >just shrink away<, as it did in
>)) ornithischians, and as the fifth metatarsal did in almost all dinosaurs?

{*      When selection pressure was sufficient, as in the ornithomimids, you
{* bet your BCF it did!

>)) In BCF, the hallux became retroverted as an adaptation to perching, as the
>)) evolving wings started to lose their grasping and climbing function. When
>)) the ground-dwelling form evolved, the retroverted hallux became vestigial,
>)) since it was a hindrance to habitual bipedal locomotion. Its variable
>)) fate in various theropod lineages supports the notion that the hallux
>)) vestigialized separately in each lineage. Simple and natural solution to a
>)) rather vexing problem for BADD theory.

{*      Not vexing at all, really.  I suppose next you'll argue that dogs have
{* dewclaws so that they too can pesh in trees?

>)) Yeah? Which thecodonts? The earliest known furcula (not counting the[...]

{*       I seem to recall somebody like Huxley saying Ornithosuchus has a
{* ?furcula.  Maybe it's in _PDW_

>>Scarcity of pre-_Archaeopteryx_ "birds,"
>        It's more parsimonious to presume there weren't any.
>)) I see! You're a >creationist<! You just wrote "there weren't any"

{*      Now, this is a family list, there's no need to go name-calling...
{*      For the dilligent third grader: I got caught in George's trap.

>)) pre-_Archaeopteryx_ birds. So _Archaeopteryx_ had no precursors and
>)) therefore arose by special creation. Or did I read you incorrectly? If

{*      As you may have guessed, I presumed you were referring to the
{* putative scarcity of Jurrassic birds.  I just assumed you had a point here
{* and weren't going on some Victorian hunt for missing links.

>)) you're a creationist, it puts a whole new slant on your postings! Tell

{*      I shan't dignify this...

>)) BCF explains the existence of Cretaceous birdlike dinosaurs as relics
>)) of their Triassic and Jurassic origins. So does BADD. But what hurts
>)) BADD is that _Archaeopteryx_ is one of the oldest maniraptorans. If BADD
>)) were correct, we should see lots of _Velociraptor_-like theropods in the
>)) Jurassic, but we don't. Instead, we get _Ornitholestes_ and such.]

{*        Do you see the Jurassic?  I don't.  Some people in China and the
{* Morrison do, but they're dealing with environments different both from
{* where Velociraptor and Archaeopteryx were found.  Lack of evidence never
{* hurts a theory quite so much as reliance on lack of evidence for another
{* theory.

>)) Birdlike but much farther down the family tree than _Velociraptor_ and
>)) _Deinonychus_.

{*  You KNOW where to put Ornitholestes?  Do tell...
        
>)) Paleocene. Likewise, the dromaeosaurid lineage diverged sometime way back
>)) in the Jurassic and became expressed as large, ostrich-size forms only in
>)) the Cretaceous. We'll find dromaeosaur-like forms in the Jurassic, but

{*      This would be no more evidence for BCf than BADD.
{*      "Size matters not. Judge me by my size, do you?"
        
>)) Which fifteen or so are these? I want names! Fifteen or so small, Late
>)) Jurassic theropods, about 50 cm long from snout to tail-tip. Go for it!

{*        I didn't say Jurassic, myself...  and I can't name some, that's for
{*        their authors to do...

{*        Sinornithoides
{*        Saurornithoides Jr.
{*        Saurornitholestes (new specimens)
{*        Confusciornis
{*        Sinornis
{*        Ibersomornis (?)
{*        Verona
{*        the other Madagascar bird
{*        something I'm probably not supposed to talk about (sorry)
{*        something else I'm not supposed to talk about (may be in above)
{*        Another darned troodontid (can't remember which)
{*        Protoavis (?)
{*  I give up, no one wants to read this anyway.  Twelve, happy?
{*  BTW  please don't line-item these to the list, I'd be happy to read it
{*  myself, but I doubt anyone else will want to sit through them again.
        
>)) John Ostrom published a description of _Compsognathus_ in which he found
>)) no trace of flight or contour feathers, despite the fact that the speci-
>)) men came from the same lithographic limestone that _Archaeopteryx_ is
>)) found in, which preserves feather impressions very well, particularly
>)) in nearly complete specimens. If dinosaurs like _Compsognathus_ were
>)) ancestral or closely related to birds, one would expect to find traces
>)) of those dermal structures that evolved into feathers. BUT--if

{*      See Paul, _PDW_ on contour feathers, which, if I recall correctly, are
{*      not preserved on Archy either.

>)) _Compsognathus_ had secondarily lost its feathers, this could explain
>)) Ostrom's inability to find them. To paraphrase Sherlock Holmes, sometimes
>)) we have to explain why the dog >doesn't< bark.

{*        But doesn't prove your point.

>)) Right. The flightless, ground-dwelling dino-birds ARE the dinosaurs.
>)) Modern birds are the crown group of the dino-bird clade.

{*  No, I hate to say it, but by priority, Dinosauria has the big clade, and
{*Aves the smaller one.  Thus, my statement holds:
{*        THAT WHICH MAKETH THE DINOSAUR IS A DINOSAUR

        Wagner
+--------------------------------------------------------------------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
| znc14@ttacs1.ttu.edu                   Then they're no friends of mine." |
|       Web Page:  http://faraday.clas.virginia.edu/~jrw6f                 |
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