The muriquis, also known as woolly spider monkeys, are the monkeys of the genus Brachyteles. They are closely related to both the spider monkeys and the woolly monkeys. The two species are the southern (B. arachnoides) and northern muriqui (B. hypoxanthus) muriquis. They are the two largest species of New World monkeys, and the northern species is one of the most endangered of all the world's monkeys.