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Dinogeorge Digest #13



For the sake of completeness, this digest includes a few posts I've already
sent to the list. Sorry if this is thus too long.

Subj:   Re: ARTHROLOGY AND FLIGHT CONTROL
Date:   98-08-02 21:29:14 EDT
From:   Dinogeorge
To:     m_troutman@hotmail.com

In a message dated 98-08-02 19:00:51 EDT, m_troutman@hotmail.com writes:

<< The biggest fault of this hypothesis is that it would require a great
amount of flight control. >>

I'd say the biggest fault of the "wind-gust" paradigm is that it requires a
gusty climate to persist steadily, day in and day out, for several million
years while the proto-birds evolve the ability to take off using the gusts.
Come on. Where do these people come up with this rot??
Subj:  Re: OCCAM'S RAZOR & THERIZINOSAURS
Date:   98-08-02 21:29:12 EDT
From:   Dinogeorge
To:     jwoolf@erinet.com
CC:     cbrochu@fmppr.fmnh.org

In a message dated 98-08-02 18:48:34 EDT, jwoolf@erinet.com writes:

<< The _Permian_??  I just checked a couple of my references, and they say
 _archosaurs_ weren't even around for most of the Permian.  The earliest
known archosaur is either _Protorosaurus_ or _Archosaurus_, but both are from
the Late Permian.  Something doesn't make any sense here.  If birds are
descended from any kind of archosaurs, then how can they pre-date archosaurs?
>>

The common ancestor of Archosauria >must< have been Permian, because it must
predate the earliest known archosaur, namely, _Archosaurus_ from the Late
Permian of Russia. _Archosaurus_ is already quite derived relative to the
prolacertiforms, which are held to be the closest known reptiles to
Archosauria, so there must be room for other Permian archosaurs, less derived
and more prolacertiform-like than _Archosaurus_. It is from among these that
the earliest arboreal archosaurs probably arose, especially given that some
prolacertiforms are also considered tree-dwellers.
Subj:  Re: OCCAM'S RAZOR & THERIZINOSAURS
Date:   98-08-02 21:29:10 EDT
From:   Dinogeorge
To:     jwoolf@erinet.com
CC:     cbrochu@fmppr.fmnh.org

In a message dated 98-08-02 18:48:34 EDT, jwoolf@erinet.com writes:

<< So, which theropods are secondarily flightless "birds?"  All of them? >>

Yes.
Subj:  Re: BCF ANDPDW 
Date:   98-08-02 20:54:45 EDT
From:   Dinogeorge
To:     m_troutman@hotmail.com, dinosaur@usc.edu

In a message dated 98-08-02 17:27:50 EDT, m_troutman@hotmail.com writes:

<<And quit the "miracles" nonsense.  There are no "miracles" being 
supported here.  Simply exaptations.>>

Obviously I haven't gotten across why the "ground up" BADD paradigm requires
a miracle: The miracle is in the accumulation of a >suite< of characters (not
just one or two but lots) in a non-flying, large, cursorial biped that
suddenly allows it to fly. It is emphatically not the evolution of flight
itself. Did whales evolve flippers >before< they went into the water? No; it
would be a miracle if they did. Then why would anyone think that birds
evolved wings before they went into the air (became arboreal)? Yet this is
just what the "ground up" paradigm maintains.

<<Let me tell you about another "miracle": early tetrapod limbs evolved for
slow "walking" through water (_Acanthostega_); then evolved for walking
(_Ichthyostega_); then evolved for better support on land (temnospondyls,
leposondyls, lissamphibians, early amniotes, etc.); evolved a more erect
stance for faster speeds ("theraspids", cynodontids, early mammals); evolved a
more erect stance for even more efficient and faster walking (tribosphenic
mammals); elongated for faster speeds (_Hyracotherium_); and finally
lengthened to the point seen in modern _Equus_.  The same can be explained
for the flight stroke.  Climbing is similiar to the flight stroke
kinematically and uses up similiar energy; gliding is prerequisite to flight
energetically, myologically, etc; and flight is similiar to both functions
(Rayner 1985, 1991). You can use this sequence in theropod phylogeny. >>

Indeed; you've encapsulated BCF as well as anyone. As I said earlier, just
good old evolution, proceeding one character at a time, over millions of
years. But--in the "ground up" paradigm, there is no climbing, no gliding, no
nothing before archaeopterygid flight. Big theropods six feet long or bigger
simply ran around flapping their arms, and suddenly, like Peter Pan, they
became small and could fly. This is the miracle.
Subj:  Re: OCCAM'S RAZOR & THERIZINOSAURS
Date:   98-08-02 20:54:41 EDT
From:   Dinogeorge
To:     cbrochu@fmppr.fmnh.org, dinosaur@usc.edu
CC:     Dinogeorge

In a message dated 98-08-02 16:57:37 EDT, cbrochu@fmppr.fmnh.org writes:

<< Actually, it has more to do with the fact that it requires a whole slew of
 reversals.  I seem to recall a recent post of yours arguing that we should
 prefer convergence over reversal every time, and yet strict interpretation
 of BCF requires multiple reversals to a nonflying condition.  And the
 number of required reversals is immense - this, by itself, renders it
 nonparsimonious. >>

The morphospace consisting of only the characters "flying" and "nonflying" is
one-dimensional (indeed, it has only two points). As I noted in that post, in
such a simple one-dimensional morphospace, reversals may happen frequently;
given enough time, they're inevitable, since the only possible change from
"flying" is to "nonflying," and vice versa. Indeed, today we have >dozens< of
living examples of secondarily flightless birds, which shows just how easily
this particular change happens. Depending on your definition of "flying," the
opposite change from "nonflying" to "flying" might be much more difficult to
accomplish than the change from "flying" to "nonflying." Most vertebrate
lineages remained at the "nonflying" state throughout their evolutionary
history, but, every so often, a lineage did accomplish that more difficult
change to "flying."

But this simple picture is by no means a true description of what happens in
secondary flightlessness. When you start looking at these so-called
"reversals" in detail, examining many more characters than just "flying" and
"nonflying," you see that these turn out not to be reversals at all: Each
lineage loses its flying ability in a different way. No two such "reversals"
are exactly alike, and of course, in no instance do these "reversals" return
the animals to the original states of all the relevant characters, for
example to bring back the small, arboreal, sprawling, quadrupedal
ur-archosaur. In fact, these so-called "reversals" are actually
>convergences<; flightless birds always converge on the morphology of a
large, cursorial biped. Each loses/acquires a different suite of characters
from the others, which makes for quite a free-for-all when attempting to
analyze their relationships. This is why the known theropod lineages have
been so maddeningly intractable to phylogenetic analysis.

Morphological convergence is much easier to accomplish than a reversal,
because in convergence all you need do is come within the ballpark of a
particular morphology, not exactly retrace your steps in morphospace.
Secondary flightlessness is not a reversal but simply a derived state like
any other.

Finally, BCF suggests that >most< Mesozoic avian lineages did >not< leave
flightless descendants. There must have been a profusion of avian species,
much as there is a profusion of avian species today. Just as there are dozens
of Galapagos finches and hundreds worldwide, so must there have been dozens
or scores of archaeopterygids in the Jurassic, exhibiting all kinds of
variation among themselves, occupying all kinds of aerial niches. (Indeed, it
has been argued that just the seven Solnhofen archaeopterygid specimens fall
into three or four species, even two or three genera.) One or two of these
species may have adopted secondarily flightlessness and gave rise to the
dromaeosaurids (for example), but most probably remained small and
lightweight and continued to fly around in the trees. The so-called
"reversal" to flightlessness may not have been a very frequent occurrence at
any time, but because some of the descendants of these flightless lineages
became gigantic and ranged across significant spans of territory, their
remains have turned up with some frequency in the fossil record, skewing our
conceptions of these events.
Subj:  Re: OCCAM'S RAZOR & THERIZINOSAURS
Date:   98-08-02 16:51:02 EDT
From:   Dinogeorge
To:     cbrochu@fmppr.fmnh.org, dinosaur@usc.edu

In a message dated 98-08-02 15:06:12 EDT, cbrochu@fmppr.fmnh.org writes:

<< Actually, this is precisely the thing that makes BCF an "umbrella
 hypothesis."  Given the weight of *all available evidence*, BCF is not the
 simplest explanation; but given a few transformations that might seem
 problematic in isolation, BCF seems outwardly to fare better. >>

I've read with comprehension every evolutionary hypothesis that relates
dinosaurs and birds. BCF is the simplest and most straightforward. It has no
problematic transformations at all. Some may have problems with BCF, but
that's not because BCF is intrinsically problematic.

Remember, the sequence of animals that leads from the common ancestor of
archosaurs to birds lies along the >spine< of the Hennigian comb, >not< along
the tips of the comb's teeth.
Subj:  Re: OCCAM'S RAZOR & THERIZINOSAURS
Date:   98-08-02 14:43:07 EDT
From:   Dinogeorge
To:     cbrochu@fmppr.fmnh.org, dinosaur@usc.edu
CC:     Dinogeorge

In a message dated 98-08-02 13:59:30 EDT, cbrochu@fmppr.fmnh.org writes:

<< At present, the phylogenetic pattern recovered by multiple independent
 analyses over the past decade does not support secondary flightlessness.
 Secondary flightlessness is an additional assumption placed on the pattern
 a posteriori.  Is it a bad assumption?  Not necessarily - but it is
 secondary, and hence not parsimonious. >>

Actually, secondary flightlessness is the simplest and most parsimonous way
to describe the relationship between birds and theropod dinosaurs. In BCF,
the wing does not go through a state in which it is a short forelimb before
it once again becomes a long forelimb (as in primitive archosaurs); it starts
out as a long, grasping forelimb in quadrupedal tree-climbing archosaurs and
it remains a long forelimb in dino-birds and birds. The short forelimbs of
theropods are >derived< proto-wings, just as the short forelimbs of extant
flightless birds are derived neo-wings. In BCF, birds do not go through a
state in which they become large, heavy, ground-dwelling cursorial bipeds
before once more becoming small; they start out as small, lightweight,
arboreal forms (probably as far back as the Permian) and remain so. The
large, unflightworthy size and bipedal cursorial lifestyle of theropods are
derived relative to the common ancestor of birds and theropods.

And so on with features of the feet, tail, and skeleton. There are no
miracles in BCF, no magic moments when flightless, ground-dwelling theropods
suddenly find themselves with exactly the right mix of features they need for
flight where before there was none. Just good old plodding evolution, acting
incrementally over tens of millions of years on dozens or hundreds of
different arboreal dino-bird lineages until finally recognizable avians
appear. This is the whole point of BCF.
Subj:  Re: CNN:"world's largest group of dino footprints" in Bolivia
Date:   98-08-01 23:15:08 EDT
From:   Dinogeorge
To:     Bettyc@flyinggoat.com, dinosaur@usc.edu

In a message dated 98-08-01 22:53:04 EDT, Bettyc@flyinggoat.com writes:

<< "The site covers an area of 269,100 square feet (25,000 sq meters),
 Meyer said, emphasising that nowhere else on earth is there an area that
 large with dinosaur        footprints." >>

The news item also says, "The large size of the area has meant several
different species have been identified including tyrannosaurus, and other
giant dinosaurs up to 82 feet (25 meters) high. "

82 feet high?? Sorry--I don't Bolivia.
Subj:  Re: THERIZINOSAURS FROM THE EARLY JURASSIC
Date:   98-07-31 19:46:13 EDT
From:   Dinogeorge
To:     Tetanurae, jjackson@interalpha.co.uk
To:     th81@umail.umd.edu, m_troutman@hotmail.com
To:     znc14@ttacs.ttu.edu

In a message dated 98-07-31 18:55:10 EDT, Tetanurae writes:

<< Anyway, it is of course possible that this jaw isn't even from a
therizinosaur.  It could belong to a prosauropod or even something like a
heterodontosaur or a stegosaur.  I will need to read the paper (whenever it
shows up...). >>

Certainly not a heterodontosaur or a stegosaur, just possible that it's a
small or juvenile prosauropod of some kind. But it is so clearly a segnosaur
(wait till you see the pictures) that those other possibilities simply fade
into the background. Zhao Xijin really has found something here.
Subj:  Re: THERIZINOSAURS AND LOGIC
Date:   98-07-30 20:05:10 EDT
From:   Dinogeorge
To:     znc14@TTACS.TTU.EDU
CC:     m_troutman@hotmail.com, Tetanurae

In a message dated 98-07-30 17:31:07 EDT, znc14@TTACS.TTU.EDU writes:

<< However, if you have a large number of cladograms which show
 reversals, it seems likely that reversals do occur. >>

It could also mean that a large number of cladograms are wrong. My argument
against the facile acceptance of reversals stems from first principles; a
true reversal is a derived state of a derived state in which the second
derived state is the same as the primitive state. Given the large morphospace
of all possible character states, what is the likelihood that the second
derived state will find exactly the same morphology as the primitive state?
If a feature is >truly< bistate, this chance might be as high as 50%,
assuming that a change occurs at all. But at 50% even a short series of
bistate characters has a low probability of becoming completely reversed,
since the probabilities multiply. Most characters exhibit a continuum of
states, and the probability of a serial reversal of such characters is
astronomically small.

With DNA base pairs, you have one chance in four that a particular base pair
will reverse (change back) after changing, and since the number of
opportunities to change grows with time, reversals are inevitable. These are
not the kinds of reversals I'm talking about, of course.

If your space has only one dimension, the probability that you will return to
your starting point via a random walk is 1--inevitable. But--

If your space has more than three dimensions, the probability that you will
return to your starting point via a random walk is zero (this is from an
article by Dan Asimov--Isaac's nephew and an old college acquaintance of
mine--in _The Sciences_ a few years back). How many dimensions does a
morphospace have?

(By the way, I'd have to dig out the article to see what the probabilities
for two and three dimensions are; I think for two it might still be 1, but
for three it's something odd, like about 31%.)
Subj:  Re: ERLIKOSAURUS' BRAIN
Date:   98-07-30 20:05:01 EDT
From:   Dinogeorge
To:     Tetanurae, znc14@ttacs.ttu.edu

In a message dated 98-07-30 18:51:58 EDT, Tetanurae writes:

<< The internal parasphenoid sinuses would have easily been able to travel
from the parasphenoid across to the basisphenoid section of the fused
braincase. >>

The parasphenoid swelling in ornithomimids is located at the front of the
braincase below the cultriform process; you can see it through the orbits in
lateral view. The basisphenoid swelling in _Erlikosaurus_ is located at the
back of the braincase below the basioccipital process. You're saying that the
parasphenoid swelling moved from the front of the braincase to the back (or
vice versa), simultaneously >removing itself< from its point of origin?
(Remember, there is no parasphenoid swelling in _Erlikosaurus_, no
basisphenoid swelling in ornithomimids.) Puh-leeze! We're still talking about
sinuses evolving in bone here, not migrating amoebas. It seems as if some
cladists will say >anything< to avoid admitting that their cladograms just
might be wrong.

If living tissue were indeed this evolutionarily plastic, then you might as
well forget about doing any meaningful morphological cladistic analyses.
Every phylogenetic hypothesis can be negated by sufficient
plasticity--particularly with the minor characters that I've seen in some
character matrices. Three supraorbitals in stegosaurs and ankylosaurs? No
problem. There were once five, four became lost, then three returned
("reversals"), then the frontal was lost but was replaced by the fourth
supraorbital...