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Re: Protoceratops Gender

do we actually KNOW which one is which? (i.e. Could the small-bump-and-large-wide-frill specimens actually be the females?) Has anyone looked into chevrons at the base of the tail, or anything like that, to try to determine the gender, like people were doing for _Tyrannosaurus_?<
Part of the problem is that determining the presence of sexual dimorphism is devilishly tricky in the fossil record, and only a few dinosaurs meet the criteria in the first place (_Coelophysis_, _Allosaurus_, among theropods). But, even with a less than perfect sample size, you can still begin to make conclusions, provided you have at least a partial growth series. The question then becomes, to me, how many catalogued and described specimens of _Protoceratops_ are there?
And if sexual dimorphism is present, you would need a way to determine which morph corresponded to which sex (as you noted in the original e-mail). I'm not too familiar with ceratopsid paleobiology, but it would stand to reason that the larger frill would correspond to the male, for simple reasons of display. However, this may not be the case, and the bad part is that there really is no good way at all to tell which sex is which in the fossil record, except in very unusual circumstances (i.e. an icthyosaur giving birth). Some have suggested using chevrons, but there has turned out to be no real correlation there. Some have suggested using relative robustness, but this is equivocal, because robustness varries among genders, depending on the taxon. For dinosaurs, some have suggested that the pelvic opening that is wider was the female, because it would accomodate an egg. But, there is nothing saying that the large opening couldn't have been used to support the male sex organs. Unless you have an egg (which we don't have for most dinosaurs), this claim cannot be substantiated.
Conclusion (IMNSHO): You can determine if sexual dimorphism is present in the fossil record, but not which morph corresponds to which sex.

Student of Geology
Northern Arizona University
Biological Science Tech
Manti-La Sal National Forest
AIM: TarryAGoat
"A _Coelophysis_ with feathers?"

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