Final answer:
Unique traits that only a specific group possesses according to the phylogenetic species definition, as well as homologous structures indicating shared evolution, serve as major indicators for species identification. The correct option is A.
Step-by-step explanation:
Characteristics commonly used to identify a species include:
- Genetic markers: These are specific sequences in the DNA that can be used to identify and differentiate species based on genetic relationships.
- Morphological traits: Physical characteristics such as shape, size, color and structure of organisms that can be observed and measured to distinguish between species.
- Behavioral patterns: The behaviors that are particular to a species and can help in differentiating between species with similar physical appearances.
- Geographical distribution: The area where a species naturally occurs can also be a factor in species identification.
Using phylogenetic species definition, if all the fossil leg bones possess a unique trait A not found in any other species, they would constitute a new species.
Additionally, similar physical features and genomes indicating shared evolution, such as homologous structures, also serve as a basis for identifying phylogenetic relationships among organisms. The correct option is A.