@serpentarius1194

2 months ago

Something I'm surprised this video didn't touch on is that we do have other animals we've been able to reasonably extrapolate the sex of! Specifically pterosaurs, which aren't dinosaurs themselves but their closest relatives. Pteranodon is famous for having two different size morphs, the larger of which has a big sweeping crest whilst the smaller one has basically a nub. Considering they had been found together, and all other characteristics of their skeletons pointed to them being the same species, we already had some decent evidence of sexual dimorphism. This is further reinforced by immature specimens of both the large AND small morphs being present, indicating that the small morph itself wasn't just an immature version of the larger morph. Figuring out which is male and which is female specifically is still far from an exact science because of how much dimorphism can vary between species as touched on in this video, but it's fairly universally assumed that the large morph is the male, while the small one is the female. While females can be larger in dimorphic species, males being the larger one is more common among tetrapods, particularly so for males with a display structure just like in Pteranodon. Animals in which females are larger rarely also have display features, and vice versa. Additionally the smaller females seem to outnumber the larger males, which is also consistent with most modern day animals. While there are cases in which females take on multiple males (polyandry) it is much, much rarer than males taking multiple females (polygyny). Males can mate frequently and easily thus have little need to be as selective when choosing a mate, while females need to be more choosy about who they mate with due to the time and resources they have to put into reproduction, so in the majority of animals there's pressure to evolve a polygynous system rather than polyandrous. Again, this isn't universal, but it is by far the more common method of mate selection. Additionally, the smaller females seemed to have wider-set pelvic bones, likely to pass eggs more easily. It isn't reliable as the sole way to sex a skeleton because many species don't seem to have wider hips when you'd think it advantageous, plus it can vary a lot between individuals within a species (including us, hence why archaeologists try to use cultural signifiers such as what a person was buried with to determine sex rather than features of their skeleton). But with everything else in mind it's a pretty safe assumption that Pteranodon's have sexual dimorphism in which males are larger with big crests, while females are smaller with tiny crests.

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