Undermining long-held paradigms

I don't understand the problem. Previously, all the known fossils of Mesozoic mammals were small herbivorous or scavenging mammals, so the reasonable assumption was that mammals were a small part of the ecosystem. Now fossils have been discovered that indicated otherwise. So now we have a better picture of what the Mesozoic looked like. What is the problem?

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"The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one." -- George Bernard Shaw

Percy has already written a decent reply to this question, but I will simply repeat my question:So what? For decades, all the known fossils of Mesozoic mammals were very small so the reasonable (but tentative!) conclusion is that perhaps all the mammals that existed during the Mesozoic were small.Now fossils have been discovered of larger mammals. So now we know that the Mesozoic ecology of mammals is more complex than was thought previously. Just like in any other field of science, new discoveries shed new light, and science marches on.

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"The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one." -- George Bernard Shaw