I have been under the impression that two species of Iguanodon, I. bernissartensis and I. atherfieldensis could quite possibly be male and female representatives of the same species. My evidence for this idea includes the fact that both species often turn up in the same formations and if I am not mistaken, both are represented in the Bernisaart (sp?) collection in Belgium. If this happens to be the case, it would make these two the best case for sexual dimorphism amoung the non-avian dinosauria, seeing as one of them, I don't recall which is more robust and the other more gracile. I don't think I will be taking bets on which were the males and which the females until after they sort that out for Tyrannosaurus rex, which also appears to be a good canidate for sexual dimorphism. Your thoughts, as always, are most appreciated.