Final answer:
Old World Monkeys have small front teeth and large molars, along with other unique dental characteristics. Their dental features are likely influenced by their diet and evolutionary adaptations to an upright posture and increased brain size.
Step-by-step explanation:
One unique feature of teeth in Old World Monkeys is that they have small front teeth (incisors and canines) and relatively large molars compared to other primate species. This dental characteristic is likely related to their diet, which includes a variety of tough plant materials and harder food items such as nuts. Additionally, Old World Monkeys have a fully upright posture, shortened arms relative to legs, increased dexterity of their hands, an increase in brain size (especially in the frontal lobes), and a decrease in bone mass of the skull and face.