Phylogenetic systematics of the viviparous halfbeak genera Dermogenys and Nomorhamphus (Teleostei: Hemiramphidae: Zenarchopterinae)

Among the 13 genera and over 100 species of halfbeaks, three genera - Dermogenys, Nomorhamphus and Hemirhamphodon - are internally fertilized and viviparous. These genera belong to a more inclusive clade, the Zenarchopterinae, that also includes Zenarchopterus, inferred to be internally fertilized and to lay fertilized eggs, and the monotypic Tondanichthys, also inferred to be internally fertilized. Whereas the Hemiramphidae are distributed worldwide, internally fertilized halfbeaks are restricted to Southeast Asia. Recent data from histological surveys of the gonads of both males and females as well as embryonic modifications associated with viviparity have been combined here with osteological characters in a phylogenetic analysis. Results indicate overwhelming support for a sister-group relationship between Hemirhamphodon and (Dermogenys+Nomorhamphus). Monophyly of the Dermogenys+Nomorhamphus clade is also well supported. These results confirm earlier suggestions that Dermogenys, as previously defined, is paraphyletic. Within the Dermogenys+Nomorhamphus clade, two monophyletic clades are supported: one comprises ten species including four new species (Dermogenys bruneiensis, Dermogenys robertsi, Dermogenys palawanensis and Dermogenys collettei) and the other comprises 13 species including three undescribed species (Nomorhamphus rossi, Nomorhamphus pinnimaculata and Nomorhamphus manifesta). Diagnoses for the species of Dermogenys and Nomorhamphus, as well as a natural classification for the included species, are presented. (C) 2001 The Linnean Society of London.