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Re: Archaeopteryx not the first bird, is the earliest known (powered) flying dinosaur
Greg Paul (GSP1954@aol.com) wrote:
<The basic contention that small theropods must have had a lot of
preadaptations on hand before becoming fliers is fundamentally absurd.
Something similar to Ornitholestes already has the basic skeletal features
needed to become an incipient glider.>
Unfortunately, most analyses seem to place *Ornitholestes* either basal to
Maniraptora, basal to Maniraptoriformes, or basal to Tyrannoraptora as a basal
coelurosaur. The primitive nature of the skeleton and alliance to animals like
*Tanycolagreus* and *Coelurus* which exhibit rather unmaniraptoran features
(and some which may be tyrannosauroid! well, my hypothesis anyway) as well as
features that ally them to compsognathids in the pelvis, suggest that using
*Ornitholestes* as an ideal bauplan for bird origins may be unwise.
<Nor has anyone explained why Archaeopteryx has expanded muscle attachments
areas on its arms just to glide. Where is the expansion of muscle attachments
of the limbs of any gliding animal? They just stretch out the legs and hold
them there for the brief time needed to make a glide. It is obvious that
expansion of muscle attachments on a forewing will one way or another allow and
improve the power of a flight stroke.>
Bats actually manage to do just fine with small muscle attachments, limited
cristae and laminae for muscular attachments to the humerus, the lack of a
struct-like coracoid, or even an expanded sternum with osseous keel, as seein
in pterosaurs and birds. Bats, showing less skeletal features than even
tinamous indicating flight tell us either 1) bats can't fly or 2) we are
confusing what features are indicative of flight. Similarly, *Archaeopteryx*
has a more derived shoulder and arm than does even *Microraptor* or any other
inferred prebird, and a larger deltopectoral crest. The presence of a large,
relative flat distal end of the coracoid with distinct margin for the sternum
shows us that unlike the rounded margin in "coelurids" and other
non-maniraptorans, that it was attached firmly to a sternum, regardless of the
sternum's presence or not (and in this case, the or not is lack of preservation
if the shape of the coracoid is indeed related to the sternum's shape, as it
appears to be in birds).
<I truly do not even begin to understand the arguments to the contrary. They
seem part of a continuing effort to some, based on a historical heritage that
saw dinosaurs as having nothing to do with birds, to keep theropods that were
not full birds as nonfliers or mere gliders, as though nonavian dinosaurs were
for some reason not allowed to be true fliers. Very odd.>
Except that all the arguments made that are not those espoused in PDW or DotA
are based on phylogenies that argue that birds are derived maniraptoran
theropods and are further illustrated in exaptation towards flight around the
rise of birds. The data for this has been discarded in DotA and from GSP here
as preposterous, based on such assumptions of what an "ideal" pre-bird should
look like, and arguing for a Archie-first, dromaeosaurs-derived-from-birds like
argument with deliberate evolution twards flight design. Studies arguing for
exaptation and development of predatory- or non-flight-respiratory-based models
that led to features bird ancestors used to developed flight (completely
without forethought, I might add), have been dismissed based on the old
argument from incredulity.
<There was no need for sinornithosaurs to deploy the nonflapping leg wings when
power flying. As I discussed in Prehistoric Times a few years ago, they could
have been used to increase the range of periodic nonpowered glides, for
soaring, and has extra flight controls, especially flight brakes, among aerial
hunt ers that lacked the more sophisticated flight apparatus of real raptors.>
Is this a real serious proposal that microraptors were soaring animals?
Soaring as a specialization arising from powered flapping? Note that NGMC 91,
unlike *Microraptor*, lacks tarsal feathers based on preservation of scales
around the tarsus, and probably preserved only thigh and shank-based feathers.
I have a potential model for how the leg feathers worked, but it will be some
time before this comes out in any coherent form in a publication, but this
model does not require in any way for a flapping origin for these animals, and
can exist without any earlier loss of flight for any dromaeosaur. It is also
possible it did arise that way, but the data does not exclude any possibility,
and this is also true, despite objections, for most of the arm-based
"flight-related features" that are espoused in GSP's DotA, which tend to lack
explanatory data and corroboration on their use as flight-based features not
expected from exaptation, such as finding them in non-flying animals that do
not show flying descendant relatives.
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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