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The Evolutionary Mosaic (wasTrees Down or Ground Up?)
Adding to Jaime's post... I think this specimen is only one more lesson of the
twists and turns of evolution. That there are no straight lines in Evolution.
We have now animals that are half modern bird from the waist-up or half bird
the waist down. Wings with half fused digits in birds with fully saurian tails
and fully functional clawed digits in reasonably modern-looking birds. Running
legs with wings or half-wings. And if this wasn't enough we have now even
dinosaurs with a different approach to flight that can't compare with any
modern bird. I think those long flight feathers around the legs of Microraptor
should make us question some anatomical given truths... I think those legs were
capable of (at least) some sideways spreading to let the 'fans' function. That
unless those feathers were some sort of freak display, just to make running
difficult. If we are seeing such fantastic paraphernalia, just imagine what we
might be seeing in the rest of the 'normal' or 'standard' dinosaurs if the soft
tissue was preserved in all of them .
Isn't the mosaic puzzle in turn a clear picture of evolution at work?
Following ground up reaching the tree heights or high canopy gliding from tree
to tree strategies we are seeing a 'free-for all' set of strategies in animals
not absolutely specialized to what we call now sophisticated flight 'yet'. At
least some of them.
Just as sifakas... arboreal but not flyers. Whatever adaptation that helps you
to survive stays. And also as sifakas: I think there would be NO fully formed
feathers if (I'd say all) more primitive dinosaurs were not already covered with
a precursor of feathers that served as insulatory integument. Hats off to Prum.
None of these animals were compelled to become modern birds. But some of these
animals were already getting fine tuned for extreme sophisticated flight
adaptations and an absolute dependency on those... and these were to become the
birds we know today, the rest went extinct.
The Yixian deposits may be the Burgess Shale of bird evolution.
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