Herpetopoma, : Pilsbry, 1890

Herbert, D. G., 2012, A revision of the Chilodontidae (Gastropoda: Vetigastropoda: Seguenzioidea) of southern Africa and the south-western Indian Ocean, African Invertebrates 53 (2), pp. 381-381 : 433-435

Herpetopoma (s.s.) serratocinctum sp. n.

Figs 26–28

Etymology: From Latin serratus (toothed like a saw) and cinctum (a belt or girdle); in reference to the strong, toothed peripheral cord.

Description:

Shell: Small, turbiniform, relatively solid; length more or less equal to diameter (L/D= 0.97–1.1); teleoconch of approx. 3.5 whorls; whorls rounded at periphery, but with a strong peripheral spiral cord; suture indented, level with subperipheral cord, but descending below this immediately prior to aperture in mature individuals; first teleoconch whorl initially sculptured with strong, widely spaced, curved, axial pliculae; pliculae becoming thinner and more close-set after one quarter whorl; 2 spiral cords arising in latter half of whorl; both axial and spiral sculpture strengthening during second whorl and a third spiral cord arising beneath adapical suture; axial pliculae prosocline, more close-set than spiral cords creating obliquely rectangular interstices; cords with rounded nodules where crossed by axial pliculae; 2 further spiral cords arise by intercalation during third whorl, end of penultimate whorl thus with 5 spiral cords of alternating strength above suture; interstices more nearly square; beads on peripheral cord, well developed, stronger, more angular and fewer in number than on other cords (approx. 25 on last adult whorl), but those in final quarter whorl smaller, less angular and more close-set. Base with 4 primary spiral cords, a weaker fifth beneath peripheral cord and a sixth mostly hidden by reflected columella; beads of basal spiral cords progressively lower and more rounded toward umbilicus. Umbilicus closed in adults, but remaining open and steep-sided in juveniles, its edge marked by the sixth basal spiral cord. Peristome markedly oblique, almost tangential; aperture subcircular to D-shaped, flattened parietally; columella pillar well developed, protruding slightly into aperture, a strong, peg-like tooth at its base and a low bulge above its mid region; interior of outer lip subterminally thickened and set with 8–10 elongate denticles which extend into aperture as in-running ridges; that nearest columella larger, a deep U-shaped notch separating it from basal columella tooth; outer portion of lip flaring and bearing additional secondary granules and wrinkles distal to primary denticles; these continue around reflected portion of columella lip; parietal region covered with glossy callus bearing superficial wrinkle-like ridges; callus not extending beyond limit of peristome; interior of aperture nacreous.

Microsculpture ( Fig. 27B, C ): Juvenile shell with vermiform spiral threads, these continue throughout shell, becoming oblique on last adult whorl (cf. Ascetostoma providentiae ); the scratch-like adult microsculpture of other species is not evident.

Protoconch ( Fig. 27A, C ): Greyish white, more or less level with first teleoconch whorl or at most weakly exsert; diameter ca 270 µm; terminal lip distinct, shallowly convex; superficial sculpture well developed, irregular and wavy, with a predominant axial alignment; no spiral component evident.

Colour: Fresh specimens translucent white with regular reddish spotting, mostly on the spiral cords and usually in more or less axially aligned rows; final portion of last adult whorl washed with pale orange-brown; some evidence of a dirty white intritacalx deposit remaining in sculptural interstices of fresh specimens.

Dimensions: Holotype (largest specimen), length 3.07 mm, diameter 2.93 mm.

Operculum, radula and external anatomy: Unknown.

Holotype ( Fig. 26A–D ): KENYA: Kilifi (3.60236°S 39.81190°E), lagoon inshore of coral reef, ca - 4 m, in sand from base of coral outcrops, 20 xii.1991, D. Herbert ( NMSA K7929 /T2640).

Paratypes: Same data as holotype ( NMSA L8270 /T2641, 15 specimens; MNHN 24650, 1 specimen; NHMUK 20110383 , 1 specimen). MOZAMBIQUE: Pemba (12.937°S 40.521°E), Praia do Uimbe, living amongst dead coral in shallow subtidal, J. Rosado, xi.2010 (J. Rosado coll’n) .

Distribution and habitat ( Fig. 28 ): Known only from the coast of central Kenya and northern Mozambique, evidently in shallow subtidal habitats associated with fringing reef systems.

Remarks: Amongst the regional fauna, H. serratocinctum most closely resembles the Mascarene H. stictum (see below), particularly in terms of size, coloration and apertural dentition. The less elevated spire, more angular sculpture and strong, saw-toothed peripheral cord of H. serratocinctum , however, are distinctive. There is also some similarity with H. fimbriatum ( Pease, 1861) ( Fig. 69C, D ), reportedly from Hawaii (but see Kay 1979), and H. corallinum Jansen, 1994 from the Great Barrier Reef, but in both these species the columella has a weaker basal tooth and lacks a low bulge above this. They also have fewer spiral cords on the penultimate whorl (four) and a flatter base giving a more trochiform profile.

Figures

Fig. 26. Herpetopoma serratocinctum sp. n.: (A–D) holotype, length 3.07 mm (NMSA K7929/T2640); (E, F) SEM of paratype with strongly serrate peripheral cord, Kilifi, Kenya, length 3.00 mm (NMSA L8270/T2641).

Fig.27.Herpetopoma serratocinctum sp.n., Kilifi,Kenya (paratype, NMSA L8270/T2641):(A) apex, bar = 250µm; (B) microsculpture at start of last adult whorl, bar = 250 µm; (C) protoconch, bar = 200 µm.

Fig. 28. Distribution of Herpetopoma serratocinctum (squares) and H. stictum (triangles). Each symbol represents one or more records.

Fig.69.Herpetopoma species examined for comparison:(A, B) Euchelus corrugatus Pease,1861, lectotype (designated Kay 1965: 58), Sandwich Islands [Hawaii], length 3.8 mm, diameter 3.7 mm (NHMUK 1962821); (C, D) Euchelus fimbriatus Pease, 1861, holotype, Sandwich Islands [Hawaii], length 3.7mm, diameter 3.6 mm (NHMUK 1962823); (E, F) Diloma verruca Gould, 1861, lectotype (designated Johnson 1964: 167), Coral Seas, China, length 3.2, diameter 2.7 mm (USNM 420).