On the classification of Corallimorphus (Anthozoa: Corallimorpharia): the ratio of discal and marginal tentacles

Since the study of the genus Corallimorphus was started, the main taxonomic character used to separate species has been the ratio of the number of marginal tentacles to that of the discal ones. Polyps with a marginal:discal (m:d) tentacle ratio of 2:1 and 4:1 collected by the “Challenger” expedition were described as two distinct species, Corallimorphus rigidus and Corallimorphus profundus respectively (Moseley, 1877a, 1877b; Hertwig, 1882, 1888). This feature remained important in the taxonomy of the genus. For example, Fautin et al. (2002) subdivided the genus Corallimorphus into two groups of species: Corallimorphus rigidus, C. ingens, C. atlanticus, C. denhartogi (ratio of marginal: discal tentacles 2:1) were referred to the «rigidus» group. C. profundus and C. pilatus (ratio of marginal: discal tentacles comes to 4:1) to the «profundus» group. Here we discuss whether this character is of a high taxonomic value or not.