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Clearly there are two different ways of interpreting evidence at work
In a previous post, John Jackson discounted the birdlike features of
_Archaeopteryx_ as "flight-adaptations" that are "easily reversible in
secondarily flightless forms". Tell me, is a (not a hooked
ectopterygoid, my mistake!) triradiate palatine in _Archaeopteryx_ a
I must recommend four papers:
Whetstone, K. N. Braincase of Mesozoic birds: I. New preparation of the
"London" _Archaeopteryx_. JVP 2 (4): 439-452
Walker, A. The braincase of _Archaeopteryx_. _Archae._ Conference
Martin, L. D. 1991. Mesozoic Birds and the Origin of Birds. _Origins
of the Higher Groups of Tetrapods_. 485-539.
Elzanowski, A. and P. Wellnhofer. 1996. JVP 16 (1): 81-94
All papers emphasize the birdlike features of _Archaeopteryx_ spp..
According to Elzanowski and Wellnhofer, _Archaeopteryx_ shows three
features segregating it from theropods and linking it to birds:
triradiate palatine (a palatal arrangment where the maxillary process is
elongated to the choanal process, which is shorted to a small hook), a
possible propulsionary joint in the pterygoquadrate (Whetstone argued
that the braincase of the London _Archaeopteryx_ shows no capacity for
any sort of birdlike kinesis, but maintains the possibilty), and loss of
the coronoid. Adding to this I must add a character that Tarsitano has
emphasized frequently; non-verticalized braincase. According to
Tarsitano, most non-avian archosaurs (except proterosuchids) display a
verticalization of the braincase elements, namely the basioccipital and
basisphenoid (notice that unlike him, I keep megalancosaurs out of
Archosauria). Birds, however, show a flat braincase floor that is
supposedly a primitive condition. Though I must disagree with his
phylogeny I do agree that a flat braincase floor is an avian apomorphy,
possibly paedomorphic; the braincase bones in crocodyloforms at least do
not verticalize until the third year of development. According to the
figures in Elzanowski and Wellnhofer, _Archaeopteryx_ spp. show
non-verticalized basisphenoid and basioccipital elements.
Walker (1985; following Whetstone) emphasized the birdlike characters of
the London _Archaeopteryx_ braincase. Whetstone argued that
_Archaeopteryx_ had a posterior quadrate articulation (regarded as the
flat threshold to the posterior tympanic recess by Walker, but the
morphology suggests that it may the precursor to the posterior quadrate
articulaton or an incipent quadrate cotyle; in any case this is not
found in any theropods except for oviraptorids, though the detailed
anatomy is different) and frontal and parietal crests (also discussed
in Martin, 1991).
Let me end with a quote from the abstract of Elzanowski and Wellnhofer:
Being unrelated to locomotion, the avian features of the skull
demonstrate that _Archaeopteryx_ is a bird rather than a feathered
nonavian archosaur (p. 81).
<<Also, why do all the J manis/arctos have to be small? Actually, I
don't mind that - there *were* some things close to that group -
apprentice Archaeopterids - small, arboreal olshevskyans not quite yet
having converted fur to modern feathers - but I'm happy with that.>>
There are some Jurassic maniraptorans as you say. But at present it
might be best to just call them 'maniraptorans'.
>Might not the first feathered flier fit in well with the ancestor of
>most successful group of K theropods?
But it is too birdlike to be the ancestors of K theropods! Tell me, do
you think that the characters above are related to flight?
<<...just like the opposing theory! No-one has evidence for *any* J
precursor to Archae apart from a few unusually small teeth which could
be anything. Apart from cladistics and historical accident, there is no
evidence that the direction of relationship is _Velociraptor_ -> Archae;
and time would seem to point the arrow the other way.>>
"Could be anything"! I think that the teeth are described as
maniraptoriform in character. Padian also described some Morrison
maniraptorans or maniraptoriforms. How can _Archaeopteryx_ be a K
theropod progenitor? The fossil record is meager in many areas and
cannot be considered as the most reliable chronical of what really
happened. _Archaeopteryx_ is theropod-like in most of its features, but
as outlined above it shows features that are not related to flight and
are not found in nonavian theropods:
1) Roughly triangular skull where the premaxillary forms a point.
2) Possible mesethemoid above the dorsal margin of the antobital
3) Unserrated, triangular, crocodilian-like teeth.
4) ?Loss of contact between jugal and postorbital and squamosal and
quadratojugal (Elazanowski and Wellnhofer state the elements may be too
short to reach each other).
5) Postorbital process.
6) Small squamosal.
7) Non-verticalized braincase.
8) Derived paraoccipital process.
9) No sagittal crest.
10) Possible incipently double-condyled quadrate (not in the classic
sense; Elzanowski and Wellnhofer state that a double-condyled quadrate
cannot be ruled out in _A. bavarica_ contrary to what has been said by
11) Single sternum.
12) Differing caudal vertebral count in _Archaeopteryx_ and K
Time does not determine the phylogeny, morphology does.
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