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Where are the feathers?
The problem of whether particular dinosaurs are secondarily flightless
reminds me of when I taught comparative anatomy. We used Holmes as a lab
text. One of his evolutionary principles was that "complex evolutionary
trends are never exactly reversed." This is true as far as it goes, but it
doesn't alter the fact that reversals of one sort or another are in fact
common. There is also the fact that parallelism/convergence seems to be
commonplace, and together these facts can wreak havoc on cladistic
analyses, more so the more incomplete the fossil record is. This is why it
has long struck me as ironic that some paleontologists dismissed
discussions about dinosaur ecology and behavior as "mere speculation,"
preferring the more "concrete" field of dinosaur evolution.
Like you, Greg, I too am scratching my head about where the late Jurassic
birds are. More specifically, where are the feathers of dinos/birds (or
whatever we choose to call them)? Why this big explosion of feathers and
birds in the early Cretaceous? Is it because flighted forms and their
feathers get into many more habitats than non-flighted ones, leading to a
much higher probability of fossilization?