- CavemanBCE
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- Honorable Member
Assuming that they aren't just graphical, aesthetic, non-canonical differences (which is the likely choice), they might not be members of a different species or even subspecies. There's not a whole lot of difference between the Kig-Yar of Halo 2 and the ones in Halo 3/Reach. There's a bit of physiological difference between the so-called human "races", but there is nowhere near enough genetic difference between a black man and a white man to constitute "race" or "subspecies". This may be the case with the different Kig-Yar.
Skirmishers, however, may be a different story, simply because they are identified as different by Bungie.