The Densorin were a sapient species of which existed roughly around 47,814 BC, during the Prothean cycle. Eventually being absorbed by the true Prothean race, they were forced to call themselves Protheans, as well. They were notable for having gone to war with the Oravores, though presumably this war had come to a close before the Reapers invaded. Fearing their own lives, the Densorin attempted to pacify the great machines by sacrificing their own young to them—however, this simply allowed the Reapers to eliminate their species more quickly.
It seems that their species was forgotten by the races that existed during the 2100s, and the only known time they were mentioned during this modern era was by Javik, the last remaining true Prothean.