Vexillum (Protoelongata), Herrmann & Stossier & Salisbury, 2014

Herrmann, Manfred, Stossier, Günter & Salisbury, Richard, 2014, A new subgenus including three new species of the genus Vexillum (Gastropoda: Costellariidae) from the central Indo-Pacific with remarks on Vexillum (Pusia) semicostatum (ANTON, 1838), Contributions to Natural History 24, pp. 1-55 : 4-9

publication ID	https://doi.org/ 10.5169/seals-787038
DOI	https://doi.org/10.5281/zenodo.5846173
persistent identifier	https://treatment.plazi.org/id/61145817-2443-FFE3-FF2F-04CEFE728230
treatment provided by	Carolina
scientific name	Vexillum (Protoelongata)
status	subgen. nov.

Treatment

Subgenus: Protoelongata subgen. nov.

Type species: Vexillum (Protoelongata) dekkersi View in CoL sp. nov.

Recent distribution: Indo-Pacific.

Description

This new subgenus is characterized by an extremely elongated protoconch consisting of 3 to 5 small glassy whorls of nearly equal size. This elongated protoconch is found in all members of the group ( Plate 1 View Plate 1 ). The protoconch can be as long as 1.3 mm. This type of protoconch is indicative of a very long planktonic veliger stage. Indeed, species in this group seem to have a wide Indo-Pacific distribution. The very early teleoconch whorls of shells in this new subgenus have narrow, slightly convex whorls with fine axial ribs, these axial ribs become obsolete on later whorls and completely absent on the adult whorls. All known members of this new subgenus have slender, elongated shells with an acuminate spire, often shiny and polished in appearance. The apertures are narrow with lirations which are often hard to see, sometimes recessed deep within the aperture. The outer lips are thin and smooth. Frequently the protoconch is missing.

The animals of the species ( Figs 8–12 View Plate 2 View Plate 3 , 16–20 View Plate 5 View Plate 6 View Plate 7 ) in the subgenus Protoelongata subgen. nov. are black with a long siphon, which is spotted with small white or yellow dots. The eye stalks are black at the base but semitransparent and spotted with tiny white or yellow dots above the eyes. The eyes are large for a costellarid. The foot is black with streaks and spots of white or yellow along the margin. The sole of the foot is grey with a streaked yellow border.

Vexillum (Protoelongata) dekkersi sp. nov. is designated as type species of this subgenus. The radula ( Figs 13–14 View Plate 4 ) is about 400 µm long and 70 µm broad, and consists of 45 to 50 transverse rows of teeth, three teeth per row. The rachidian tooth bears three strong equal cusps on the anterior edge of its basal part, which is rather narrow with broad lateral flaps. Lateral teeth unicuspid, sickle-shaped.

The following species are transferred to this new subgenus:

Mitra corallina REEVE, 1845 = Vexillum (Protoelongata) corallinum ( REEVE, 1845) comb. nov.

Mitra xerampelina MELVILL, 1895 = Vexillum (Protoelongata) xerampelina ( MELVILL, 1895) comb. nov.

Mitra bilineata REEVE, 1845 = Vexillum (Protoelongata) bilineatum ( REEVE, 1845) comb. nov.

Mitra (Pusia) loyaltyensis HERVIER, 1897 = Vexillum (Protoelongata) loyaltyense ( HERVIER, 1897) comb. nov.

Discussion

The elongated protoconch is characteristic for the new subgenus. No other group in the Costellariidae has this type of protoconch. Most Costellariidae have a short multispiral, paucispiral or mammillate protoconch.

The animals of the new subgenus are black with small white dots, sometimes a few white streaks and a white or yellow margin at the foot. In contrast, the colouration of many Costellaria animals is a salt/pepper combination with grey and white, e.g. in the Costellaria type species Vexillum (Costellaria) semifasciatum (LAMARCK, 1811) or V. (C.) sanguisuga (LINNAEUS, 1758) . But other combinations are also present: In V. (C.) coronatum (HELBLING, 1779) and V. (C.) cookorum TURNER, GORI & SALISBURY, 2007 the animals are semitransparent with white dots and in V. (C.) costatum (GMELIN, 1791) and V. (C.) acupictum (REEVE, 1844) there are pink markings on the semitransparent animals. Other animals, such as in V. (C.) rodgersi SALISBURY & WOLff, 2005 or V. (C.) potieri DRIVAS & JAY, 1989 show greenish brown markings. V. (C.) micra PILSBRY, 1921 also has a black animal like Protoelongata animals, but the eyestalks are different. In the new subgenus, the eyestalks are semitransparent above the eye, but in V. (C.) micra another black part with a white ring is present there. The animals of some Pusia species also show salt/pepper combinations, such as in V. (P.) patriarchale (GMELIN, 1791) or V. (P.) kuiperi TURNER, 2006 , but often the colour of animals is similar to the colour of the shell, e.g. in V. (P.) rubrum (BRODERIP, 1836) , V. (P.) crocatum (LAMARCK, 1811) and V. (P.) recurvirostris (SOWERBY III, 1908) . Thus the animal colouration in Protoelongata is characteristic for this new subgenus and different from comparable subgenera.

The radula of the type species Vexillum (Protoelongata) dekkersi sp. nov. has only three cusps on the rachidian plate. Therefore, according to Cernohorsky (1970) it differs from those of Vexillum plicarium (LINNAEUS, 1758) and Vexillum (Costellaria) semifasciatum (LAMARCK, 1811) which are the type species of the genus Vexillum s. str. and the subgenus Costellaria . All pictured radulae of Vexillum s. str. and Costellaria species in Cernohorsky (1970) and Fedosov & Kantor (2010) bear at least 7, but often more than 10 cusps on the rachidian plate. The only pictured Vexillum s. str. species with three cusps in Cernohorsky (1970) is V. (V.) isaoi (KURODA & SAKURAI, 1959) , which according to Robin (2013) is accepted as V. (Tosapusia) isaoi (KURODA & SAKURAI, 1959) and therefore belongs to another subgenus.

The radula of Vexillum (Pusia) microzonias (LAMARCK, 1811) , the type species of Vexillum (Pusia) , is not known to us. Some members of that subgenus such as V. (Pusia) rubrum (BRODERIP, 1836) or V. (P.) cf. salisburyi CERNOHORSKY, 1976 also have more than 10 cusps on the rachidian plate of their radula ( Fedosov & Kantor 2010) (Fedosov & Kantor used the name V. (P.) salisburyi , but Salisbury (1984) demonstrated that this Philippine species is another undescribed taxon, therefore we use "cf." in this paper). Other Pusia members have radulae comparable to that of V. (Protoelongata) dekkersi sp. nov., for example V. (P.) patriarchalis (GMELIN, 1791) or V. (P.) cavea (REEVE, 1844) , which are also illustrated in Cernohorsky (1970). Perhaps the variation is higher in this subgenus than in other subgenera, or further investigation will lead us to more differentiations and new genera or subgenera.

Further investigation must also verify whether the radula characteristic of V. (Pr.) dekkersi sp. nov. is specific for the type-species only or for all members of this subgenus.

Etymology: The subgeneric name combines the abbreviation "proto" with the Latin word "elongatus" (elongated). We use "proto" as abbreviation of protoconch, which derives from the female Latin word "concha" (shell) and therefore use the female form Protoelongata . The name refers to the characteristic elongated protoconch, not present in other genera/subgenera of the Costellariidae .