Class AVES expanded

[Ken Kinman]

Dear All,
     My post about an expanded classification of Class AVES was sent on
Friday, but appeared this morning.  Over the weekend, I was delighted to
learn that the avian Order Caenagnathiformes was named by Cracraft over 30
years ago (Cracraft, 1971, in Journal of Vertebrate Paleontology).  Of
course this was based on the misunderstanding that it was a Neornithean
(crown group bird).  There are a whole lot more forms to add to that group
now, but toothlessness such as this is extremely rare among theropods except
for Class Aves sensu lato and its probable sister group (ornithomimoids).
But the only new order in my proposed classification is Segnosauriformes.
     In any case, the whole debate about what is a bird (and even whether
birds evolved from dinosaurs) has become completely muddled by forms like
Mononykus, Rahonavis, and all these new "feathered dinosaurs".  But it is
striking that both Oviraptor (Caenagnathiformes) and Deinonychus
(Archaeopterygiformes sensu lato) have been found fossilized (in situ)
brooding their "bird" eggs (which are ornithoid in both ornamentation and
microstructure).  If they existed today, they would clearly be recognized as
primitive ground birds (feathers, nests and parental care, ornithoid eggs,
birdy bodies, birdy behavior)---granted some had teeth, but so does
Archaeopteryx.
     I am not a strict cladist, so I think birds should remain classified as
a Class Aves separate from Class Reptilia.  But all these recent fossil
discoveries (especially in China) are saying "Hey, these are birds too", and
drawing the line at Archaeopteryx is now seen to be a big mistake in need of
correction.  So I am simply initiating a debate where the new line should be
drawn (apomorphy-based, like the traditional Class Mammalia).
     I understand Feduccia's distaste for strictly cladistic
classifications, but do not share his extreme distrust of cladistic analysis
(although like any other tool, it can be abused).  Even Larry Martin is
apparently beginning to see the bird-coelurosaur relationship is real.  I
believe the evidence pretty clearly shows that birds evolved from theropod
dinosaurs (specifically the coelurosaurs), but I won't ever be saying "birds
ARE dinosaurs" which is a rather irritating mantra that has come out of
AMNH.  Their cladistic analyses, however, have shown that some coelurosaurs
are a lot more birdy than others, and that is where I am drawing the new
dinosaur(reptile)-bird boundary.  I think this is a good middle ground
approach to this debate, and as usual I will be getting criticism from both
sides.  We shall see what happens.
         ------- Cheers,   Ken


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