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LET THE SYNAPOMORPHY WARS BEGIN! (REALLY, REALLY LONG)



Ack, not again....  Anyways, we have gone ove this time and time again, and I
find it rather, uh, repetative.  Something akin to arguing that birds evolved
from crocodiles instead of dinos or soemthing of the like.....  Yes, let's
get to it.

<<<<Dinogeorge wrote (Don't it give you a warm fuzzy to be arguming again,
George?:)>>

Arguming? Who's arguming?>>

Yes, it's giving me a warm feeling just like during the endless (though they
did eventually have an 'end') bcf threads of last winter.....

<<You miss the point, as usual. The point is that small prosauropods are
similar enough to small, primitive theropods to have once been classified as
coelurians, so one might expect that derived prosauropods, that is,
segnosaurs, could now also >mistakenly< be classified as coelurians. Please
do >not< try to tell me that cladistic analysis is infallible.>>

That is not entirely correct.  The prosauropods were classed with
Coelurosaurs because they were mixed up with Rauisuchian teeth, and given the
name paleopods.  Prosauropods are strikingly different from theropods in the
hand, the hips, the feet, the neck and especially the head.  You might have a
few elements that could be confused between the two, but not entire
skeletons.  Prosauropods and theropods would not get mixed up, and do not get
mixed up, when whole skulls and skeletons are known.

<<I happen to think that cladistic analysis yields a reasonable family tree
about 90% of the time, based solely on my own view of how many cladograms
look reasonable versus how many do not.>>

One point that I would like to make.  Is that a cladogram need not look
resonable to your (ao anyone's) subjective eyes to be correct.

<<It's those other 10%, where cladistic analysis has been misled by excessive
convergence (for example) or incorrect character interpretation, that I think
I can identify. Unlike you, I do not accept cladistic analyses as infallible
unless disproved by more cladistic analyses.>> 

Did I ever say such nonsense?  Did anyone on this list ever say such
nonsense?  You might remember my quite lengthy post concerning Weishampel and
Heinrich's analysis of basal Ornithopoda.  In my opinion, it was, uh, quite
fallible, the breaking point being detailed tooth characters.  These are
extremely important in deciphering relationships simply because, they are not
like locomotor aperati or muscle scars, or blood vessels because the way the
animal eats is dirrectly linked to their teeth, so there is not a lot of
homoplasy and convergence with teeth.  The trouble is, that many dino
paleontologists have been tricked into thinking that dino teeth are
absolutely worthless for deciphering relationships or identity because that
is what the mammal paleontologists have told them.  The truth is that this is
entirely and absolutely false.  Dinosaur teeth are extremely diagnostic to at
least the major clade level, and certainly diagnostic enough to tell if it
belongs to a theropod or prosauropod/ornithischian.  You might have some idea
where this is going, but more on that later

<<And I certainly do not give the same weight to minor, variable
characters randomly scattered throughout a dinosaur's skeletal anatomy as I
do to characters in unified postcranial character complexes such as feet,
limbs, pelvis, and vertebral column.>>

So, what about the path of cranial nerves out of the brain?  How about the
teeth?  The enlarged, pneumatic parasphenoid?

<<When cladistic analysis yields an incorrect result, which I think it does
in
the segnosaur case, then any similarities >must< be convergences. I consider
a smattering of random theropod-like characters in the skull of an obvious
non-theropod to be of little significance-->>

It is not an obvious non-theropod at all.  Unless you claim also that someone
ripped the teeth out and stuck in bullatosaur teeth, and somone pulled out
the braincase and jammed in a maniraptoriforme braincase....

<<Since the analysis must yield >some< kind of answer, we suddenly find
segnosaurs as a sister group to ornithomimids (as in Sereno 1997) or in some
other equally untenable position on the theropod family tree. Why not, for a
change, toss segnosaurs in with prosauropods and sauropods and see what
happens?>>

Uh, they will still be the sister group to ornithomimids if you threw in all
dinosaurian taxa.  The cranial nerve anatomy is clearly that of a
maniraptoriforme theropod.  No other vertebrate has their olfactory nerves in
such a condition.  To wirte that off as convergence, is saying that it is
just as likely to be convergence for dromaeosaurs and birds to have their
brains wired that way.

They are also clearly bullatosaurs for two reasons: 1) they have an enlarged,
pneumatised parasphenoid in the braincase.  Do not try to claim that this is
the basisphenoid, because it is not, check my post from last winter on the
subject. 2) the teeth are clearly those of bullatosaurs as well.  These
features are common in therizinosaur and bullatosaur teeth:
1: expanded base
2: constricted root
3: slightly recurved
4: low number of denticles
5: elongate denticles

No other dinosaur has those tooth characters, especially basal
ornithischians.  _Revueltosaurus has 10 low denticles on the the caudal and
rostral marigins of the crown, _Pekinosaurus_ has 12, _Lesothosaurus_ 6,
_Orodromeus_ 12, and _Thescelosaurus_ 8.  _Alxasaurus_ has 8 tall denticles,
which I suppose could indicate a close relationship to _Lesothosaurus_ or
_Thescelosaurus_, but the fact that the two ornithischians' teeth are
absolutely triangular and highly sculpted with triangular denticles, rather
than the typically rectangular or pentagonal denticles of therizinosaurs and
other theropods negates any close relationship.

Lastly, both therizinosaurs and ornithomimids have highly derivedlower jaws
that are extremely similar, they share the condition of a downwardly
deflected dentary, and the complex of bones on the lingual surface of the
mandibular fenstra.

Thus therizinosaurs are the sister group to ornithomimids, and are
ornithomimosaurs by definition {Ornithomimus > Troodon | Tyrannosaurus}.

<<>I've read that paper several times and I have yet to find >any< feature of
the >skull of _Erlikosaurus_ that bars a prosauropod ancestry for
segnosaurs,>>

The enlarged paraspenoid is present only in ornithomimosaurs and Troodontids.
 The teeth are clearly those of a bullatosaur, and the cranial nerve anatomy
is only seen in maniraptoriforme theropods.

<<Of course it's relevant. When the cladistic analysis goes haywire, it's
time
to look around for other plausible groups. I consider most of the known
prosauropods to form a sister group to segnosaurs plus ornithischians within
the larger clade of herbivorous dinosaurs.>>

But there is no indication that the analysis went haywire at all.  To me it
is much more plausible to have therizinosaurs derive from a bullatosaur
ancestor sometime in the early cretaceous, gain a few vaguely prosauropod
characteristics (the feet), and then show up in the late cretaceous, then for
them to have been derived from prosauropods, disappear for more than 120
million years, then show up with theropod characteristics all over the place
in their heads, their hands, their teeth, their hips, their legs......

<<The (usual) missed point here is that the semilunate carpal is a touted
apomorphy of the theropod group that supposedly includes segnosaurs.
(And--why should prosauropods have a semilunate carpal block??) _Alxasaurus_
is an early segnosaur that does >not< have the semilunate carpal block.>>

_Alxasaurus_ does have a semi-lunate carpal block.  You and I have both seen
it George, it does exist, it is there.  It is also in _Therizinosaurus_, and
has been known to exist in _Th_ for at least 20 years.

<<Therefore the semilunate carpal block developed independently in segnosaurs
and theropods, unless it just happened to be reversed in _Alxasaurus_. Which
alternative is likelier, considering that the carpus of _Alxasaurus_ bears
little other resemblance to theropod carpi with semilunate blocks?>>

Again, _A_'s hand is clearly that of a theropod.  There is an extremely short
MCI 1, and three digits.  Again, I find it confusing that you claim the only
possible explanation for theropods losing their digits 3 and 4 is because
they were in need of a more slender hand for gliding and climbing in the
trees, yet there are any number of reasons that they could have been lost in
therizinosaurs.....

<<So I assert that the semilunate carpus does not exist in Segnosauria, and
instead
there is a convergent fusion of some carpal elements in the later, more
derived forms.>>

It is a semi-lunate carpal in the typical theropodan fashion that allows for
some degree of arm folding, wrist bending ability.

<<You must be kidding, right? Here the shoe >has< to be on the other foot, so
to speak: It's up to the theropod people to show how the highly derived
theropod foot reversed into the prosauropod-like segnosaur foot. Just saying
it's a "reversal" is not nearly enough; to a cladist, anything that doesn't
fit a pet phylogeny is a "reversal." I don't have to worry about this
problem, since in my phylogeny segnosaurs simply acquired their
prosauropod-like feet from their ancestral prosauropods.>>

Yes, exactly, but then they convergently (and conveniently) rewired their
brains and remodeled their teeth...

<<So open yours already and stop simply spouting old-hat cladistic dogma.>>

No one is spouting dogma.  Therizinosaurs are not prosauropods, plane and
simple.  I am really getting quite tired of this and find myslef still
arguing away about how the parasphenoid isn't really a parasphenoid because
it is labelled basispenoid in the diagrams, but clearly in the text, it says
that every braincase element was fused and they know for sure that one of
them had to be the basisphenoid, so that is what they labelled the whole
braincase.  It is quite obvious that the parasphenoid is the large bulbous
thing in the diagram because it has the cultriforme process sticking off of
it, thus indicating that teh suture with the basisphenoid (and other elements
in the brain) have been obliterated.  This is what I am tried of, rehashing
the same old thing over and over and over again.  I will not become a martyr
to arguing ad nausium.

Peter Buchholz
Tetanurae@aol.com

"It's not the heat that gets to me; it's the humidity!"