BIRDY _ARCHAEOPTERYX_

["Matthew Troutman" <m_troutman@hotmail.com>]

Clearly there are two different ways of interpreting evidence at work 
here...

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 
flight adaptation?  

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 
Proceedings.  123-134.

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 
the
>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 
cavity.
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 
numerous people).
11)  Single sternum.
12)  Differing caudal vertebral count in _Archaeopteryx_ and K 
theropods.  

Time does not determine the phylogeny, morphology does.

Matt Troutman

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