Final answer:
Prosimians are one of the two main groups of primates, characterized by nocturnal habits, smaller sizes, and smaller brains compared to anthropoids. They have larger olfactory centers in the brain and belong to the Strepsirrhini group, capable of synthesizing vitamin C. Physical traits like five fingers, various teeth, and opposable thumbs are common to all primates but vary between groups.
Step-by-step explanation:
The Order Primates is categorized into two groups: prosimians and anthropoids. Prosimians, which form one of the basic groups within primates, possess several distinguishing features that set them apart from other primates, such as anthropoids, which include monkeys and apes. Some of the notable characteristics of prosimians include their generally nocturnal lifestyle, smaller size, and relatively smaller brains when compared to anthropoids.
Prosimians include various species like the bush babies and pottos of Africa, the lemurs of Madagascar, and the lorises of Southeast Asia. These primates exhibit a larger emphasis on olfactory senses, indicative of their nocturnal behavior, with larger olfactory centers in the brain. Another interesting distinction is that prosimians are part of the Strepsirrhini (wet-nosed primates) and can synthesize vitamin C, unlike the Haplorhini (dry-nosed primates, which include humans) that must obtain vitamin C from their diet.
Finally, physical traits such as the presence of five fingers on each hand, a variety of tooth types, particular eye orbit characteristics, and an opposable thumb also define primates, including prosimians. However, the degree to which these features are developed can vary between prosimians and anthropoids.