A new study of the striped cardinalfishes from the Indo Pacific should solve some of the identification problems rife in this genus.
Thomas Fraser of Florida's Mote Marine Laboratory has just completed a study of the striped cardinals in the Apogon fasciatus group and has just published his findings in the journal Zootaxa.
Fraser looked at the nine species of striped cardinals in the group, which includes A. fasciatus; A. quadrifasciatus; A. monogramma; A. septemstriatus; A. evanidus; A. elizabethae; A. quinquestriatus; A. kiensis; A. bryx and a new species called Apogon pleuron, and looked at their taxonomic characters in depth.
He managed to produce a detailed picture of the taxonomy of the group and also produced a new dichotomous key for the genus to aid in the identification of these fishes.
The new species Fraser described in the paper, A. pleuron, which is known from New Guinea, the Philippines and India to China, has a dark middle stripe in which the lower edge forms narrow vertical bars, as well as melanophores on the roof of the mouth.
For more details see the paper: Fraser, TH (2005) - A review of the species in the Apogon fasciatus group with a description of a new species of cardinal fish from the Indo-West Pacific (Perciformes: Apogonidae). Zootaxa 924: 1-30.