keith63, no one here is denying that free oxygen existed in the early atmosphere, we are simply saying there was very little of it. The earliest fossils (cyanobacteria) date back to approx. 3.5 billion years (though this is still controversial!), so oxygen was most likely being produced. However, it appears that the oxygen was most likely being taken up almost immediately by the Fe-rich oceans, or the bacteria themselves, resulting in the banded iron formations quetzal mentioned. The atmosphere itself does not show any appreciable amounts of O2 until after the Archean.
Your idea of a transitional fossil is completely misguided, unfortunately. What you are describing is a deformed mutant that would not be able to reproduce. You are thinking in terms of a freak of nature. The fossil of a mammal that can't quite live in the ocean nor on land would never exist long enough to reproduce. It would die immediately.
What you do see are mammals that live in the ocean but are air-breathing. The can exist in both worlds. You see turtles that live in water and others than live on land. Given time those turtles will go their own separate ways and possibly become unrecognizable as turtles some day. That doesn't mean all the other turtles also have to change. Just the ones who are pressured to do so by their environment.
The process of fossilization is difficult enough and now you expect us to find freaks of nature? Organisms that have a one in a million chance of ever being produced in the first place? You need to learn more about the true nature and form of transitional fossils.
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As far as Archaeopteryx is concerned I have read and provided the citation showing it is just a bird.
What about the non-bird-like traits that it exhibits? Where's the beak? It has ventral ribs that are present in reptiles but not birds? You showed why it's a bird, but it also has characteristics not found in birds but in reptiles. Sure sounds a lot like a transitional organism.
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