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Birds again



Hi, girls and boys! I'm sad to hear that some of us are leaving this forum (Ral
ph and Jerry, for example). Mickey said that the investigation work is a very t
ime-consuming one, and that's true. But you can learn a lot in this ship, altho
ugh you have to pass from half an hour to an hour per day at the computer
reading posts.
Dsmith came with more interesting matters about early birds. You are right abou
t the characteristics of a flying vertebrate, and _Archaeopteryx_ and its buddi
es have all of them.
-Aerodinamic wing: the primary and secondary feathers of _Archaeopteryx_ are as
simetrical, so they are made to fly, they are aerodinamic.
-They have a large brain (slightly smaller than that of extant birds) and large
 eyes.
-The more important muscles involved in the flight stroke are those that lowere
d the wing, because is in this phase when the force to go up and forward is ori
gined. So you have to have strong pectoral muscles in order to make enough forc
e to fly, and strong bones in whose insert those muscles. _Archaeopteryx_ (and
especially the Early Cretaceous birds) has an osified sternum and great coracoi
ds to perform this function. The upward movement of the wing is the movement th
at allow to make another downward movement (the recovery and the powered stroke
s, respectively). So, if you don't have strong muscles to recover the wing, you
 still can fly, although slowly, because you can'tmake the movements as fast as
you should to fly faster.
-Metabolism: you said it's necessary a high metabolism to fly. That's is true i
f you fly for long time. If you don't, you don't need it (it's like run; if you
 run fast for long distances, you need a high metabolism). But maybe the early
birds had high metabolic rates (if the feathers were developed as an insulation
structure, and then exapted to fly).
On the other side, I want to ask something to Dinogeorge. Why do you think that
_Megalancosaurus_, _Cosesaurus_ and _Longisquama_ are theropods? I can't see an
y reason to make that. I have seen _Cosesaurus_ (my boss published a paper some
years ago describing it as a prolacertiform, you know) and I don't think it is
an archosaur. Can you give us your opinion?
See you! Nino


Bernardino P. Perez-Moreno
Unidad de Paleontologia
Departamento de Biologia
Facultad de Ciencias
Universidad Autonoma de Madrid
28049 - Madrid
SPAIN