Species 571 was the Borg designation for a race of the Delta Quadrant who worshiped a god named Brothara. They were a humanoid species distinguished by a bifurcating (cartilaginous) ridge running vertically down the forehead stopping at the upper lip. Their bifurcating ridge was physically similar, but not identical to Dala's species, whose ridge ended at the brow line.
In their religion, it was considered "against the will of Brothara" to desecrate a dead body. P'Chan also noted that his "people don't believe in holding grudges."
Members of this species came into contact and were assimilated by the Borg sometime before 2368, when a Borg sphere crashed on Planet 1865-Alpha, severing the three surviving Borg drones from the Collective. Among the drones were P'Chan and Lansor, both of whom managed to escape the Collective permanently some time before 2376. (VOY: "Survival Instinct")