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Re: Ancestors and descendants (story for Nick)



Ken Kinman wrote:

<Well, I assume you are talking about a derived modern
bird. Although there would be some shared features
between the deinonychus and the bird, I think I would
be even more struck by the large number of differences
between the bird and all the saurischians.>

  Descent through modification.

<Look at this thing, It's arms have turned into wings,
it's lost its front claws and teeth.>

  Phylogenetically, cladisitically (even from Martin
and Zhao and the rest), and even intuitively in such
analyses published calling themselves that (Feduccia,
1996, 1999 comes to mind) teeth were a plastic feature
in early avian evolution. Several groups independantly
lost teeth, including confuciusornithids,
enantiornithines, and neorinithines.

<For Heaven's sake, there's hardly any tail
left---just a stubby little pygostyle.>

  *Nomingia* has _24 caudals, the last four of which
are fused. *Caudipteryx* is that shy of having a true
pygostyle, and guess what ... *Archaeopteryx* has a
tail consisting of greater than 24 caudals lacking any
sort of fusion or close appression (as in Caudi).

<It has a laterally facing shoulder joint>

  As do *Sinornithosaurus*, at least to some degree,
and *Unenlagia* (at least to some degree).

<and the feathers are asymmetric,>

  Irrelevant -- this does not preclude flight. Does
asymmetry suddenly mean birds _sensu stricto_ are now
not entrenched within groups of dinos bearing
symmetrical vanes?

<I bet this beastie can fly. And it's a good thing, or
those two theropods would make a quick meal of this 
defenseless little thing.>

  Is this Archie, or a modern bird, encountering
"those two theropods"?

<And look it's got a fully opposable hallux so it can
perch itself in a tree once it gets away.>

  Yeah, and this is also about as plastic as it gets
since terrestrial birds also bear reversed halluces
(plesiomorphy). If Caudi is a dino, and its reversed
hallux is indeed what Zhou and Wang (2000) think it
is, then there's a stinker of a revision to do in
popular origins of birds.

<You ever seen anything with a palate like that?>

  Like what? Have you seen the palate of *Naja*?
Compare it to *Boa* and *Pachyrachis*, then compare
those to *Mosasaurus*, and tell me whose closer to
whom, and which "Order" these respective forms fall
into. Snakes bear a highly modified palate that does
wonders to their feeding methods ... the palate of
lizards and mosasaurs (sensu stricto) is so different
that this could be a feature of classificatory
separation of rank in Linnean terms. Indeed, Serpentes
and Lacertilia were considered separate within
Reptilia, by all intents and purposes in the mein we
are discussing this in, without a common origin until
Lepidosauria was coined. We now know that Serpentes is
nested within Lactertilia, since many lactertans are
basal in morphology to snakes (inluding varanoids). So
tell me, why does the morphology of a palate mean
anything?

<Oh yes, and look at all these flight adaptations,
deep thorax with a strut-shaped coracoid, a triosseal
canal with the tendon of the supracoracoideus muscle
(great for wing rotation).>

  *Bambiraptor* (Burnham et al., 2000), *Velociraptor*
(Norell and Makovicky, 1999), and possibly also
*Sinornithosaurus* (Xu et al., 1999) have derived
concave dorsal margins of the coracoids that are, if
not analogous, then homologous to the avian triosseal
canal.

<See the elastic furcula, deep sternal keel, and look
at those pectoral muscles----this is a very strong
flier (those pterodactyls will be so jealous).>

  And all the above features, with the exclusion of
the furcula and triosseal canal, are present in
pterosaurs, so there really isn't much to be jealous
about. Pterosaurs ruled the airwaves in the Mesozoic.
Small pterosaurs may have been outcompeted by the
birds in the Cretaceous, but only teratornithids have
approached the size of some Cretaceous pterosaurs.
Flying adaptations and ability in some pterosaurs was
truly incredible, and there were probably far more
adaptations in the flight structure than birds, static
in their brachial morphology as it seems they were (do
chime in, Matt) that comparing the two is a futile as
suggesting that birds who leapt on their prey to drive
the development of wings was analogous to jaguars and
tapirs [this is a point I wish to return to, list].

<Not only strong flight, but controlled as well---see
the alular feathers>

  Gosh, *Archaeopteryx*, Confuciusornithidae,
*Liaoxiornis*, and *Liaoningornis* seem not to have
possessed this little treat for dismissing stall... I
wonder, does the alula have anything to do with Aves
as a whole?

<and the rectriceal fan.>

  And just gosh darn again, Confuciusornithidae had
_two_ retrices, and these only in the purported males.

<With all these derived features, we can hardly call
this a dinosaur even if it does share some features
with them. This bird beastie has been doing some
serious evolving.>

  Didn't Scott Hartman mention Darwinism was a step
above Linnean taxonomy? And wasn't that because it
recognized the number of differences meant
diddly-squat when recognizing the only means to
consider relationship is the similarities two forms
possess?

<This thing is almost as weird as that hairy mammal
thing we found last week---you know, the one with the
three shrunken jaw bones shoved up into it ears, and
you decided to call it a rodent.>

  I'll tell you a mammal that was considered so wierd
it wasn't even recognized as a mammal at one point --
the bat.

<I thought turtles and tuataras were pretty weird, but
this bird beastie clearly belongs in a class by itself
(just like that mammal).>

  Let me ask two last questions, Ken: Do you consider
the separatation of a form nested within another taxon
as constructive to understanding the descent of forms,
while still recognizing they are nested? If one can
consider the rhynchosaurs with their bizzare skulls,
tooth banks, edentulous premaxillae and bona fide
beaks as having a series of features that go far above
all other archosauriforms, then would you separate
Rhynchosauria from Archosauriformes et al.?

  A third: Why?

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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