User blog comment:LoveWaffle/First look at Guardians of the Galaxy's Ronan, Korath, and More!/@comment-3317214-20140216150736

Or perhaps the Chitauri are just the one race, and Thanos has more allies than just the Chitauri? Which would explain the differences in appearance between them and Sakaarans, Kree and Korath, or whatever's actually going on.