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Re: New(ish) paper II



Tim Williams wrote-

> _Microraptor_ is
> called a troodontid.

Must have listened to Jean-Pierre D'Amour. ;-)
Actually, I think they just worded their paragraph confusingly and were
referring to Sinovenator-
"Another recent find in northern China (Xu et al., 2002), of a small,
feathered dinosaur apparently contemporary with Archaeopteryx, may shed
light on proto-bird ancestry. Belonging to the dinosaur family Troodontidae,
this early Chinese species, Sinovenator changii, and other troodontids share
some distinctive characters, but this little feathered reptile had a small
size, long hind limbs, and an avian coracoid and furcula."
Now I admit, it is odd for ABSRDists to understand phylogenetic bracketing
and parsimony when ascribing birdlike characters to dinosaurs, so saying
Sinovenator was feathered and had a furcula when neither are preserved does
come as quite a surprise.  Regardless, I believe that's what they're doing.

> "_Longisquama_ possessed feather-like epidermal extensions of several
kinds.
> These included some on the postaxial forelimbs that closely resemble
flight
> feathers. The feathers seem homologous with bird feathers, which is
perhaps
> not true (Alan Feduccia, pers. comm.; also see [Zhang and Zhou (2000]) of
> so-called feathers of the small dinosaurs (their filaments may not be
> derived from scales as are true feathers). The feather-like structures of
> _Longisquama_ suggest that birds may not be descended from the
hypothesized
> small theropod dinosaurs after all, but from an archosaurian glider that
> perhaps gave rise later to some feathered forms with bipedal locomotion."

I've never seen so many false statements in one paragraph.  The only correct
thing they say is that non-avian dinosaur feathers aren't derived from
scales.

And more fun from the paper-

"A feathered, four-winged ''dromaeosaur'' from Jurassic beds in Liaoning
Province in northeast China was
recently discovered and given the name Microraptor gui (Xu et al., 2003)."
Do ABSRDists just like pretending the Yixian is Jurassic?

"The pelvic connections to the hind limbs [in Microraptor gui] seem
irreversibly adapted to a gliding niche, and not conducive to running or to
flapping flight."
Oh good!  Someone's finally studied the femoral head and acetabulum to
determine their range of motion. ;-)

"However, M. gui is not ancestral to Archaeopteryx, although remarkably
similar, and our depicted ''ancestor'' would be somewhat intermediate, have
more down feathers, fewer specialized flight feathers, shorter wings, and a
quadrupedal or bipedal stance, and we could not predict whether the teeth
would resemble those of dromaeosaurs or Archaeopteryx."
At last, the tripedal putative 'protobirds' can be discounted as avian
ancestors.

"M. gui could never have evolved flapping flight."
"The elongate hind limbs of M. gui might have lost their fringes of
feathers, but could never revert to a bipedal stance."
The "Czerkas Rule of Evolutionary Constraint" makes a couple appearances.
And look- more functional information for Microraptor gui.  Apparently it
couldn't stand bipedally, who would have thought?

"Since there are no known fossils directly ancestral to birds, although
Microraptor seems closely related, one
may presume in the true phylogeny of Archaeopteryx that proto-bird ancestors
lived in habitats unfavorable
for preservation."
Aha!  So that's why we find no direct ancestors in the fossil record- they
all lived in habitats unfavorable for preservation.  Every time a speciation
event would be near, the population would retreat to the mountains until
they developed autapomorphies.

"This quadrupedal and gliding reptile (Longisquama insignis) suggests that
an archosaur line led to both coelurosaurian dinosaurs and birds, and had
appeared by the Late Triassic."
Now I see....
Their phylogenetic hypothesis seems very confused, reminding one of Feduccia
(2002).  I _think_ Long et al. are MANIACs.  They state birds evolved from
Longisquama relatives, but also that Eumaniraptora including dromaeosaurs,
troodontids and birds is a strong hypothesis.  Coelurosaurs are the sister
clade of birds, much as in Czerkas' work.  Who knows where other dinosaurs
go, of course.  Then again, sometimes Microraptor gui is referred to as a
dromaeosaur only in quotes.  And they talk about feathered dinosaurs,
without saying they are actually or may be birds instead.  Confusing...

Mickey Mortimer