| Popis: |
Diastoma melanioides (Reeve 1849) is the sole survivor of a long lineage of gastropods in the genus Diastoma Deshayes 1850, family Diastomatidae, and is not well known in the literature. This group was common in the Tethys Sea during the Tertiary and was most abundant during the Eocene. The living species is confined to shallow-water habitats in southern Australia. The taxonomic assignment of the group and its relationship with other cerithiaceans was based on shell characters until recently, when I examined the soft parts of the one extant species. The operculum, radula, and internal anatomy provide the additional characters necessary for a proper assignment and allow a more informed judgment about the relationships of the diastomids to other cerithiaceans. A more detailed account about the anatomy and systematics of Diastoma may be found in Houbrick (1981:589–621). |
