Final answer:
Prosimians are primitive primates, but the term 'prosimian' is not a good taxonomic category as it does not reflect the true evolutionary relationships among primates, evidenced by the reclassification of tarsiers.
Step-by-step explanation:
Prosimians are a group of primates that include the bush babies of Africa, lemurs of Madagascar, and lorises, pottos, and tarsiers of Southeast Asia. They are generally small, nocturnal, and have relatively smaller brains compared to other primates. However, the term 'prosimian' is considered not to be a good taxonomic category because it does not accurately represent the evolutionary relationships within the primates. Specifically, tarsiers share more features with the anthropoids (monkeys, apes, and humans) than with other so-called prosimians, such as lemurs and lorises, making the classification misleading.
The division of Order Primates into Strepsirrhini ('wet-nosed' primates) and Haplorhini ('dry-nosed' primates) is more accurate because it aligns with the primate lineage based on genetic and evolutionary studies. The tarsier, which has mixed features of both prosimians and anthropoids, exemplifies the inadequacy of the 'prosimian' category because they have been reclassified under Haplorhini, not with the lemurs and lorises under Strepsirrhini.
Taxonomy has evolved from being based on physical traits to integrating genetic and evolutionary data, making it important to use categories that reflect ancestry and species relationships. Thus, prosimians do not form a good taxonomic group since they do not represent a monophyletic lineage – that is, they do not include all descendants of a common ancestor.