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neoflightless dinosaurs



Checked out the interesting paper on Incisivosaurus (you know, there are vast 
numbers of new dinosaurs that I hardly know the names for). The (in this case 
largely cranial) cladistic argument that basal oviraptorosaurs are evidence 
that they are not post-urvogels is not compelling because it fails to take 
into account the large number of dervied flight features found in ovi's 
postcrania (incl big furculas, large reflexed coracoids, folding arms) of 
which some more derived than those of Archaeopteryx (larger sterna, ossified 
sternal ribs and uncinates, extremely abbreviated tails in some cases). 
Caudipteryx (with its small, symmetrical hand feathers) especially is in no 
regard anatomically indicative of being a protoflier and has all the 
attributes expected in a neoflightless bird. It's not been shown that the 
skull of Incisivosaurus is over all less avian than that of Archaeopteryx, in 
fact it seems more so in some palatal features. It is possible that 
oviraptorosaurs are closer to modern birds, and that derived exampls evolved 
additional avian features in parallel with birds. Or, incisivosaurs may have 
experienced extensive reversals in association with herbivory. Consider that 
the temporal region of Confuciusornis is much more primitive than that of 
Archaeopteryx. This is the sort of flight loss reversal thing that cladistics 
is inherently hard pressed to handle. In fact, there is growing evidence that 
some short tailed flying birds from the Jehol have strong oviraptor like 
features, which may eventually show that the dinosaurs are descended from 
birds more highly derived than even I suggested in DA. The jury is still way 
out on this one. And phylogenetic work in this area must take into account 
the development of the possible flight apparatus - which is not a problem 
with most phylogenetics.  

The jury is not still out, despite discussion on the list, on whether basal 
dromaeosaurs were good fliers. I've finished restoring the type Cryptovolans 
(which might be Microraptor but it's real hard to tell because the latter's 
type is inadequate although its tail is much shorter) in the same flight mode 
I used in fig 7.4 in DA (ask to see it at SVP). The wing area and wing span 
to mass ratios are about the same as in Archaeopteryx, and in the middle of 
the range for modern flying birds. No gliders have such well developed 
airfoils, nor do birds that have limited flight abilities. The wing feathers 
are strongly asymmetric, which establishes a full aerodynamic function, 
including the ability to generate thrust as well as lift. The strongly 
retroverted coracoid and well developed feather supporting finger flanges are 
advanced flight features. Because the fully ossified sternum is six times 
larger relative to mass than in Archaeopteryx the flight muscles should have 
been larger, and the ossified sternal ribs show that the system for anchoring 
these muscles was much stronger. So Cryptovolans could definitely fly better 
than Archaeopteryx, and probably approached Confusiusornis in this regard.  
Since some birds fly well with surpisingly modest flight muscles (see DA for 
details) Crypto must have done the same in view of the well developed 
adaptations listed above. 

Dromaeosaur anatomy is in no way compatible with them having been protofliers 
via-a-vis Archaeopteryx, they were well beyond the urvogel in terms of 
flight. They were even further beyond the Dail or other terrestrial flight 
origin theories. So the conventional hypothesis is deceased. There are two 
alternatives. Dromaeosaurs split off before the Archy-bird clade and 
developed advanced flight independently. Or, Archaeopteryx split off before 
the dromy-bird clade and the sickle-claws inherited advanced flight from 
basal birds. Both are definitely plausible. However, the cladistic evidence 
that Archy was more avian than dromy is actually weak and badly contaminated 
by  problems of neoflightless reversal, and there is abundant character data 
that dromys are more avian anyway. So the hypothesis that dromys are 
post-urvogels is much superior at this time. Hopefully more fossils will make 
the matter clearer. 

G Paul