User blog comment:Kogath/Monster Hunter: World Discussion/@comment-25083735-20191105005322/@comment-25933225-20191107101222

When talking about relation between different species, you shouldn't consider stuff like "they're semi-aquatic", that might lead you to wrong assumptions (as an example, you might say that muraine and sea snakes are related, because both live in salted waters and they have similar moves). Same, don't take in consideration their element, Ice and Fire Agnaktor are very close, but they've got litterally opposite elements.

For the rest, you're not wrong, yes, Miralis and Magdaros both got six limbs. Tho, the fact that both of them have "modificated limbs" maybe isn't that relevant, because we can clearly see that Miralis is more related to Fatalis than Magdaros, and the Fatalis have "normal" wings. If we were to talk about evolution in the MH universe (let's forget that evolution might not be relevant for every monster in the MH universe, because some of them are unic monsters like the Fatalis), the Fatalis and Miralis had a common ancestor with "normal wings", and in the case of Miralis, they just developped differently, leading to these limbs, useless to fly, but able to create small meteors. As the Zorah Magdaros as six limbs, it's clearly also a member of the "true" elder dragon family. I assume that the fifth and sixth limbs are something that appeared slowly during evolution, and later gave the current elder dragon family. So, the first members of this family must have had very primitive fith and sixth limbs, and Zorah might have kept those "primitive" limbs. Or, maybe, its ancestors had "normal wings", but they ended up like the ones we know with Zorah. So, yes, both Miralis and Magdaros have modificated limbs, but not the same way.

As a conclusion, I'd say that they are related, as both are members of the true elder dragon family, but they're not necessarilly that related. They might be as close to each other as chickens are to crocodiles, for all we know. We can make many theories about the evolution of the elder dragon family : there are no six-limbed vertebrates in our world, so it's up to our imagination.

Btw... Thanks for saying that Zorah had six limbs, I never noticed this, now I can really consider it as a member of the elder dragon family XD.