Re: Archaeopteryx not the first bird, is the earliest known (powered) flying dinosaur

[GSP1954@aol.com]

Tim W offered a hypothesis for explaining how the well developed arms and 
wings of Jehol dromaeosaurs may have evolved for enhanced predation rather than 
flight more advanced than Archaeopteryx. This concept is a nonstarter. I forgot 
to mention that a character present in the dromaeosaurs is stiffening of the 
central digit associated with the flattening of the same finger (the central 
finger of Archaeopteryx remained more flexible, although probably less than the 
theropod norm). The reduction or loss of flexation of the main finger is of 
course adaptative if the arm is being enhanced as wing, but not at all for 
predation. The basic idea that such extremely powerful arms were for predation 
is 
contradicted by the fact that as soon as larger dromaeosaurs lost flight they 
reduced the arms to more normal dimensions. The wings of sinornithosaurs were 
certainly inferior to those of flightless dromaeosaurs as hunting organs. The 
hypothesis that sinornithosaur arms evolved their flight features for enhanced 
predation is so inferior that it is not viable. It is also irrelevant. Even 
if sinornithosaur arms really were adapted for predation, this would still 
leave the very powerful, fully winged arms superior as flying organs than those 
of 
Archaeopteryx! And inferior in terms of finger flexibility. 

As I explained in DA the flight adaptations found in the bird-like theropods 
are generally difficult to explain in a nonflight context, and entirely 
explainable as flight features. Small, long armed theropods were already 
pre-adapted 
to becoming fliers, it is very plausible that the dinosaurian flight 
adaptations evolved entirely in the context of flight. The latter hypothesis is 
superior, but not yet verified by Jurassic fossils. What I object to is the 
automatic tendency to presume that the flight features began to develop before 
the 
beginning stages of flight. I have doubts about the Mayr et al cladogram 
showing 
oviraptorosaurs and therizinosaurs with flight adaptations being more basal 
than Archaeopteryx that lacks a short tail, large sternal plates, ossified 
sternal ribs and uncinates. However, if those dinosaurs are more basal than 
Arch, 
then it remains probable that oviraptorosaurs and therizinosaurs descended from 
fliers. Archaeopteryx does have fully developed wing feathers, and those may 
go way back into avepectorans, sometime earlier in the Jurassic. So far a 
fossil showing a theropod that could not fly in some manner or other, and 
clearly 
did not have flying ancestors, that has flight preadaptations has not shown 
up. Unless one is discovered the preadaption hypothesis remains speculative, 
and 
inferior, albeit not to the same degree as the hypothesis that sinornithosaur 
arms were adpted more for predation than flight. 

Mickey M did a useful task in tallying up the cladistic scoring of characters 
that I've cited in the past. The use of these characters is more extensive 
than I thought, but as MM shows important gaps remain in the scoring, and a few 
of the characters are being missed. It is important, for instance, since we 
now have complete wings for a number of taxa to score the length of the longest 
outer primary to the length of the hand, a feature that is more derived in 
sinornithosaurs than in Archaeopteryx. In the latter metacarpal III is barely 
curved, in the flying dromaeosaurs it is markedly more curved. 

G Paul