Vexillum, RODING

GENUS VEXILLUM RODING View in CoL €, 1798

FIGURE 25 View Figure 25

Type species: Vexillum plicatum Roding, 1798 (= Voluta plicarium Linnaeus, 1758 ) (SD, Woodring, 1928) ( Fig. 25A View Figure 25 ).

Synonyms

Arenimitra Iredale, 1929 ; type species Mitra arenosa Lamarck, 1811 (= Voluta exasperata Gmelin, 1791 ) (OD) ( Fig. 25G View Figure 25 );

Callithea Swainson, 1840 [invalid: junior homonym of Callithea Feisthamel, 1835 ( Lepidoptera View in CoL ); Pulchritima Iredale, 1929 View in CoL is a replacement name]; type species Mitra sanguisuga Linnaeus, 1758 (SD: Herrmannsen, 1846: 155);

Costellaria Swainson, 1840 View in CoL ; type species Mitra rigida Swainson, 1821 (= Mitra semifasciata Lamarck, 1811 ) (M) ( Fig. 25E View Figure 25 );

Mitropifex Iredale, 1929 ; type species Mitropifex quasillus Iredale, 1929 (= Mitra obeliscus Reeve, 1844 ) (M);

Pulchritima Iredale, 1929 ; type species Mitra sanguisuga Linnaeus, 1758 (by typification of replaced name);

Tiara Swainson, 1831 View in CoL ; type species Mitra corrugata Lamarck, 1811 (= Voluta rugosa Gmelin, 1791 ) (SD: Gray, 1847: 142);

Turricula View in CoL H. & A. Adams, 1853; (invalid: junior homonym of Turricula Schumacher, 1817 View in CoL ); type species Voluta vulpecula Linnaeus, 1758 (SD: Cossmann, 1899: 162);

Vulpecula Blainville, 1824 ; type species Voluta vulpecula Linnaeus, 1758 (T);

Zierliana Gray, 1847 View in CoL ; type species Voluta ziervogelii Gmelin, 1791 (OD) ( Fig. 25H View Figure 25 ).

Diagnosis

Shell small to medium-sized, fusiform or broadly fusiform to turriform, ovate or biconical; spire very tall to low. Protoconch tall, conical, whitish or brown, translucent, with three or more evenly convex glossy whorls. Teleoconch whorls evenly convex to subcylindrical or with flattened outline, typically distinctly shouldered. Sculpture dominated by axial elements, represented by ribs of varying strength, sharp or rounded, usually slightly undulating. Spiral sculpture variable, absent in some species, in others represented by fine, evenly spaced grooves, pronounced between axial ribs, or throughout shell surface, overriding axial ribs. Siphonal canal short to very long, straight and tapering or recurved at its tip, notched at its end. Aperture elongate, narrow; outer aperture lip lirate within, sometimes with strong denticles formed by lirae at outer lip’s edge. Inner aperture lip with three or four distinct, sometimes very strong columellar folds, uppermost fold strongest. Radula with wide bow-shaped rachidian, typically bearing multiple pointed cusps and unicuspidate sickle-shaped or subtriangular laterals. Accessory salivary gland usually present, very small. Bulky gland of Leiblein strongly reduced, whitish, non-glandular, situated at distal part of long and strongly convoluted secondary glandular structure. Seminal groove closed along its entire length.

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Distribution and habitat

Common throughout the Indo-Pacific from Madagascar to French Polynesia. From intertidal to bathyal depths, on sand, mud, coral rubble, or reefs.

Remarks

The remarkable diversity of shell sizes, shapes, and sculpture patterns in Vexillum make the circumscription of the genus a not trivial task. The slender, narrowly fusiform shell of Vexillum radius ( Fig. 25H View Figure 25 ) has little in common with the robust and heavily sculptured Vexillum cancellarioides ( Fig. 25O View Figure 25 ), or the species traditionally included in Zierliana ( Fig. 25P, Q View Figure 25 ), with their peculiar dentition of aperture. This diversity of shell forms, however, reflects the diversity of ecological conditions where species of Vexillum live. Whereas typical Vexillum species can be encountered in numbers on sand or mudy bottoms, a broad and robust ‘ Pusia -like’ shell is commonly observed in species that inhabit rocky shores and intertidal pockets in the reef. The heavily armoured aperture of the species traditionally placed in Zierliana most likely evolved in response to intense predation pressure. A similar aperture characterizes Atlantilux puella , which is unrelated to the Zierliana lineage, and also inhabits intertidal rocky flats. We also presume that the distinct siphonal notch, shared by the vast majority of Vexillum species, appeared as an adaptation to burrowing in sediment, as in many other neogastropod sand dwellers, among them mitrids, olivids, terebrids, etc. On the contrary, the radula of numerous Vexillum species remains strikingly conservative, and the variations in foregut anatomy are also rather moderate, compared with the extensive conchological disparity; the function of apomorphic costellariid foregut structures is discussed below.