| Abstract: | Diatom material from South Africa and Swaziland was examined with light and scanning electron microscopy. Five new taxa are proposed: Gomphonema crocodilei, G. quasicrocodilei, G. venusta, G. latistigmata, and G. cholnokyi. Gomphonema venusta has been previously misidentified as Gomphonema clevei Fricke and G. cholnokyi as G. subclavatum (Grunow) Grunow. All of the species possess biseriate striae, areolae with external vela, a true stigma, and marginal laminae underlying the valve margin and mantle. Compared to the other members of gomphonemoid lineage, the five new species show greatest similarity to Gomphoneis mesta Passy-Tolar & Lowe, G. magna Kociolek & Stoermer, and G. rhombica (Fricke) Merino, García, Hernández-Mariné, & Fernández and to the Herculeana lineage of Gomphoneis sensu Kociolek and Stoermer. The most recent phylogenetic analysis of the genus Gomphoneis showed that the two lineages of the genus. Herculeana and Elegans, are not monophyletic. The Herculeana lineage is more closely allied to Gomphonema than to the Elegans lineage. Since the Elegans lineage contains the generitype of Gomphoneis (G. elegans (Grunow) Cheve), and the species described here are more closely related to the Herculeana lineage, we have assigned them to Gomphonema. |
