Answer:
Stub for a thumb or no thumb, overall size, shape of fingernails and shape of nostril.
Explanation:
Old world monkeys had no stub for a thumb or had no thumb while the New world monkeys posses this feature.
The overall size of the Old world monkeys was greater than those of New world monkeys.
Old world monkeys had flat fingernails but sharp fingernails have been found in New world monkeys.
Nostrils in the Old world monkeys are narrow and pointed downward but in the New world monkeys the nostrils are round in shape.
