Final answer:
The phylogenetic species concept is based on shared possession of a unique characteristic to determine the smallest monophyletic group.
Step-by-step explanation:
The species concept based on analysis of character states that indicate the smallest monophyletic group is the phylogenetic species concept. This concept states that a species can be determined by shared possession of one unique characteristic. For example, if a group of fossil leg bones all possess a trait that is not found in any other identified species, then those bones would belong to a new species. This concept helps address the challenges of identifying species over time and determining interspecific and intraspecific variation.