Ugliest monkey in the world - Uakari

The bald uakari (Cacajao calvus) or bald-headed uakari is a small New World monkey characterized by a very short tail; bright, crimson face; a bald head; and long coat. The bald uakari is restricted to várzea forests and other wooded habitats near water in the western Amazon of Brazil and Peru.

Its scarlet red face is due to the lack of skin pigments and plentiful capillaries that run under its facial tissue.