On Living Japanese Turridae (1)

Abstract

This paper deals with a revision of Japanese species of some Turridae such as Gemmula, Turris, and allies, with special reference to the phylogeny of this group. The taxa, the Tribe Turrini in this paper, is the subfamily Turrinae from the reports of POWELL, 1942 and 1964, because his Turrinae, Turriculinae, Cochlespirinae, Clavatulinae, Clavinae, etc. are generally very close compared with Cytharinae and Daphnellinae in the shell features and lingular characters. Turrini is to be divided into three subdivisions with representative genera Kuroshioturris, Gemmula and Turris. Kuroshioturris- and Turris-groups consist of only a single genus from Japanese seas, while Gemmula-group contains Lophioturris, Lophiotoma and Xenoturris. Kuroshioturris and Turris have smooth, paucispiral protoconch, while Gemmula-group has a multispiral (or paucispiral) protoconch with axial riblets on the last turn (or turns). The peripheral keel of Kuroshioturris- and Gemmula-groups is developed on the middle part of the whorl. Turris-group differs from these two, and suprasutural keel of the younger whorls develops to the peripheral on the later whorls, though the peripheral keel of few forms of this group does not well develop and spiral cords are subequal. The earliest part of the teleoconch of Kuroshioturris-group lacks subsutural and suprasutural keels, but, at least, subsutural keel is to be seen in other groups. In the Turris-group three (rarely four) spiral cords are subequal on the younger whorls, and the forms without strong peripheral keel have four subequal spirals on the adult whorls. The radula of the genera Turris and Gemmula are subequal and consists of marginals only, while that of Kuroshioturris is unknown. A new genus Protogemmula is proposed in this paper in order to discuss phylogeny. Protogemmula has small shell with four smooth whorls and a row of granule on the middle part of a whorl instead of peripheral keel. Its type-species is "Gemmula" cretacea SOHD, which is the oldest form of Turrini. Kuroshioturris must be a series of Cretaceous Protogemmula and Campylacrum, Paleogene Eopleurotoma, and living Lucerapex. These genera have smooth protoconch and similar sculpture. Many species of Gemmula group have been reported from Paleogene, but few of them agree with Ptychosyrinx in its features. Ptychosyrinx has short canal, three rowed radula, and multispiral protoconch containing two or more axially ribbed whorls. It is not impossible that Paleogene forms of Gemmula group (Ptychosyrinx) had derived from series of Protogemmula to Kuroshioturris, though a careful revision should be necessary to make sure. Turris-group must have branched from Gemmula group because of the similar characters but for peripheral keel and protoconch.