The southern muriqui (Brachyteles arachnoides) is a large New World primate that inhabits the Atlantic coastal region of southeastern Brazil, possessing one of the largest body sizes among New World monkeys and a long tail. It feeds primarily on fruit but also consumes leaves and bark, and moves through the canopy skillfully using its limbs and tail. It forms multi-male multi-female groups of 15–45 individuals with a generally male-biased social structure and is characterized by peaceful behavior that helps avoid conflict. Reproduction is seasonal, and its conservation status is listed as Critically Endangered (CR).