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Some searching turns up “Return to Lost City”. I don’t think that’s it, as I seem to recall the people involved didn’t actually know that dinosaurs were alive, and the style of the Dinotopia books—many of which I’ve read—is different from what I remember. On the other hand, my memory is fuzzy enough that I could be imagining that stuff, so thank you very much for the answer. I’ll take a look at it.
Meanwhile, I’m open to any other suggestions!

Book published before 2000 (read it before then, not sure how much before or how old it was). The hero (I think) was going off to college or something like that, and around the beginning of the book he was discussing it with his girlfriend, who didn’t want him to go. The next thing I remember about it is that they were in some forest with a tribe (maybe multiple tribes) of intelligent dinosaurs (perhaps Troodons) where there was at least one instance of a ritual with the girl’s hand or wrist being slit slightly to let blood drip onto something.