The third pattern, found in B. melanurus, has the caudal fin completely dark. The coloration pattern is useful for separating species, but apparently does not allow inferences about phylogenetic relationships to be safely made, since this character is widespread in this family.
A distinctive third pattern, present in B. melanurus, features an all-black caudal fin. This pattern serves to differentiate between species; however, it does not offer a secure foundation for inferring phylogenetic connections, since this trait is common throughout this genus.