Altaria is based on a legendary Chinese bird with Dragon traits. Its typing makes sense.
Actually it isn't. It's...reaching, as to why it's Dragon.
It and Swablu are based on The Blue Bird of Happiness, an opera focused on two characters called Tyltyl and Myltyl, tasked with finding the titular bird.
Tyltyl takes his name from Tyl, the brightest star in the constellation Draco (The Dragon). It's clearer in Japan where it's name is Tyltalis.
The english name unfortunately crossed wires a bit and while makes more immediate sense and kept the star reference (Alto + aria, as well as a play on Altair, brightest star in Aquila (The Eagle)), it loses the slight hints as to why Altaria's a Dragon.
It's doubtful it's based on the dragonbird considering said creature is aquatic (at least as a dragon) as I recall, and Altaria has no watery attacks outside Rain Dance which is more based on the cloud nature of it.
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