Kawamura, S., Takenaka, N., Hiramatsu, C., Hirai, M. and Takenaka, O. (2002). Y-chromosomal red-green opsin genes of nocturnal New World monkey. FEBS Letters, 530 (1-3):70-72.

Chromosomal locations of red-green opsin genes in the northern (A) and southern (B) species of owl monkeys. It had been a norm that mammalian red-green opsin genes are located on the X chromosome. We found that owl monkeys, the only nocturnal animal among simians (humans, apes, Old World monkeys and New World monkeys), have additional copies on the Y chromosome.