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Re: Status of _Caudipteryx_



Eric Lurio (ELurio@aol.com) wrote:

<Well, it isn't EXACTLY "flightless, full-stop,"(it can glide, which is
sort of flying) but that's not the point at all. Caudipteryx and some
of it's contemporaries may NOT be "secondarily" flightless, but be the
evolutionary equivilent of the colugo as compared to the fruit bat. The
critters of the time we're talking about were more diverse than we
currently know about.>

  Yes, and here we have a case of a gliding animal and true flying
animals. They have one thing in common in their flight apparatus:
patagiata. This does not infer flight, or a trend towards flight; it
suggests it, though. However, there are several different scenarios
these two groups can take, and one of them is that their patagiata
developed separately: One finds two different gliding groups of
sciuroids (sciurids and anomolurids) and a different sciuromorph group
that can glide (dipodids), plus another rodent group, eomyids, that
have produces patagiata-bearing forms, each attaching their patagia to
different portions of the body, some with accessory cartilaginous wrist
or elbow structures, others directly to the wrist. Colugos, unlike
bats, attach integument to the wrist, not throughout the fingers. Not
to say that the relationship as has been implied is correct, but the
structure for flight in birds and bats includes the manus. In non-avian
maniraptorans, it includes the manus, but in colugos and gliding
rodents and sugar gliders (marsupials) it does not.

<Think of these things like hipperions. The evolution of the horse was
indeed linnear from Hyracatherium to Equus, however there were lots and
lots of side branches like hyperions which didn't make it to the
present day.>

  I'd like to see your evidence for the lineality of equoid evolution.
Several different branches developed unidactyly (or at least walking on
all four feet on one toe). Facial morphology, tooth morphology, and
limb morphology has also converged in the lineages of archaeotheres,
paleotheres, and equines, and their common ansectors.

<You've got two closely related branches, one learned to fly and one
still glides, the latter is "primitively" flightless.>

  This is assuming bats went through a gliding phase in their
evolution. The most basal bat known has advanced arms indicating a
brachial- and phalangeal-supported skin.

<A cat>....

  Cats? There are miacids, basal carnivorans, which have a body plan
similar to the basal archontans, fereans (carnivores and creodonts) and
ungulates (condylarthrans, whales, elephants, other "standard"
ungulates) all share some basic body mechanics that would not,
evolutionarily speaking, _prevent_ the design from easily developing a
flighted or gliding form. 

<So we've got lots of birds and 'bird-oids' in China and whether they
are primarily or secondarily flightless is currently unknown.>

  What we know is that they are for the most part flightless. That's
it. Placing this in an evolutionary scenario is useless because the
puzzle is not complete enough besides known animals to make more of a
conclusion as to their possible relationships. Mechanics in the limbs
show that these animals were not capable of flight. Some propose they
were secpondary flightless, and that an ancestor was flighted, such as
*Archaeopteryx* [in some scenarios] or that they never had a flighted
ancestor, which makes them _nothing_ flightless, just flightless. They
cannot glide, they cannot do whatnot in the air except as Hartman has
proposed in that they could have used the tails and arms with feather
spreads to control maneuverability.

  As for the definition of flight and gliding, this has been discussed
extensively on this list, one can easily use the "origin of flight" as
search criteria.


=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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