(11-20-2014, 04:32 PM)Mae Wrote: There are snakes and sharks that give live birth instead of laying eggs. And if I'm reading correctly, the only difference between their method and most mammals is how the unborn are nourished: in most mammals, there's the placental connection where the mother provides nourishment, whereas with the sharks and snakes the young are self contained for nourishment (basically a yolk). Fertilization and gas exchange is nearly identical for both the sharks/snakes and mammals... and, again, the live birth.
... And then, just to be fair to the overall argument, I suppose... we have the platypus. Lays eggs in nests, but still a mammal. And then we have the echidna, which also lays eggs, but carries the egg in a pouch until it hatches and develops a while before emerging, and females don't have nipples but is still a mammal...
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Hrm. Okay, maybe XIV races are mammals that evolved from the echidna?
You know, this is a good point, and it's interesting to note that apparently sharks have three ways of reproducing! But we're separate from them and snakes because of the presence of hair/fur. The hard and fast definition is pretty clear cut where our characters would fall, based on the limited information we have on reproduction and assumptions that can be made based on the seeming presence of mammary glands.
Mammal: any vertebrate of the class Mammalia, having the body more or less covered with hair, nourishing the young with milk from the mammary glands, and, with the exception of the egg-laying monotremes, giving birth to live young.
Of course, that's a really, really basic definition and I'm pretty sure it doesn't take into account any animals that happen to be defined as "mammals" yet don't follow those hard and fast rules. Dolphins have some hair around the tip of their "beak" before birth (and I think sometimes shortly after?), but don't have any in their adult life. Interestingly enough, whales apparently do have hair though; or at the very least they have hair follicles.
So assuming our characters aren't some sort of deviation from the natural order (hello platypus!), we can infer that they WOULD be mammals because of the presence of hair, mammary glands, internal spine (we're definitely not bugs or something), and quest text that implies we have live birth as compared to egg laying. But at the same time, there's technically nothing that explicitly states that Eorzean biology is the same as Earth biology.