Preserved marine plankton samples and one fossil sample were analyzed to investigate the morphology of species of the diatom genus Asteromphalus Ehrenberg by light and electron microscopy. In addition, permanent slides from various collections of four museums were observed.
Seventeen species of Asteromphalus have been studied. The morphology and possible function of structures unique to Asteromphalus such as the hyaline rays, tympanum and valve margin indentation are discussed and the major characters of the genus are defined. One new species is described and an amended diagnosis for the genus is given together with a proposal for the classification of Asteromphalus: the genus is divided into two subgenera, Asteromphalus and Liriogramma nov. stat., and further split into seven sections. Phylogenetic relationships with other genera and some aspects of biogeography of several species are also discussed.
All taxa described are illustrated by light and electron micrographs and each description is accompanied by references for identification.