Cerithidea andamanensis Reid, 2014, new species
Creators: name: Reid, David G.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Potamididae
Cerithidea
Cerithidea andamanensis

description: Cerithidea andamanensis new species
(Figures 11, 12 K–P)
Potamides (Cerithidea) quadratus —von Martens, 1887: 169 (not Sowerby, 1866 = C. quoyii).
Cerithidea n. sp. B Reid et al., 2013: fig. 2 (map).
Types. Holotype NHMUK 1887.3.10.24 (Fig. 12 K–N) and 4 dry paratypes NHMUK 1887.3.10.25–28, King I. [Kadan Kyun], Mergui [Myeik] Archipelago, Burma.
Etymology: from the known distribution in the Andaman Sea.
Taxonomic history. This species has only recently been recognized, its existence having been noted in the biogeographic study of Reid et al. (2013). The identification by von Martens’ (1887) is based on the same material from Mergui (collected by J. Anderson) which now forms the type collection.
Diagnosis. Shell: spire straight, whorls rounded, periphery weakly angled; aperture flared, anterior canal and apertural projection well developed; 16–22 axial ribs on penultimate whorl, 7–10 after ventrolateral varix; ventrolateral varix an enlarged rib at 240–250°; 5–6 spiral ridges on spire, 4–5 ridges above periphery on last whorl, spiral ridges form nodules where they cross axial ribs but are weak in between; brown with darker spiral cords. Andaman Sea.
Material examined. 11 lots.
Shell (Fig. 12 K–P): H = 26–39.2 mm. Shape elongated conical (H/B = 2.29–2.47, SH = 3.00–3.43); decollate, 9 whorls remaining; spire whorls rounded, suture distinct; spire profile straight; periphery weakly angled; thickness moderate. Adult lip flared, thickened; apertural margin planar in side view; strong anterior projection adjacent to deep notch of anterior canal. Sculpture on spire of straight to slightly curved (opisthocyrt) rounded axial ribs, interspaces 1–2 times width of ribs, 16–22 ribs on penultimate whorl, 7–10 ribs after ventrolateral varix (i.e. only slightly more distant than on spire), remaining strong throughout final whorl, only faint axial wrinkles on base; spire whorls with 5–6 spiral ridges, forming small nodules where they cross axial ribs but weakly developed in spaces between axial ribs, spiral interspaces 1–1.5 times width of ridges, no interpolated threads, 4–5 spiral ridges above periphery on last whorl; overall effect is of nodulose axial ribs; base with 12–14 spiral ridges, outermost is peripheral cord of same size as primary ridges above. Ventrolateral varix a strongly enlarged rib at 240–250°, forming an anteriorly projecting boss at periphery. Surface with fine spiral microstriae on periostracum, strongest on spiral ridges. Colour: brown, spiral ridges darker brown, shoulder ridge sometimes pale; aperture pale brown, spiral lines showing through.
Animal: unknown.
Range (Fig. 11): W Thailand, Andaman Is, NW Malaysia, NE Sumatra. Records: India: Andaman Is (NHMUK 1907.8.30.267). Burma: King I. [Kadan Kyun], Mergui [Myeik] Arch. (NHMUK 1887.3.10.24; ZMB). Thailand: Ranong (USNM 777649); Ao Nam-Bor, Phuket I. (NHMUK 20130250); Kantang, Trang Prov. (RMNH). Malaysia: Langkawi, Kedah (T. Goulding & B. Dayrat). Indonesia: Pantai Cermin, Deli, Sumatra (RMNH 175798).
Habitat and ecology. At Phuket I., Thailand, a specimen was collected in the landward fringe of a marine mangrove forest.
Remarks. No molecular data are available. However, the shell characters of the available specimens differ in a consistent way from the two other members of the C. quoyii group and these differences are even more pronounced than those that distinguish the other two from each other (Table 1). The distributional range of the new species approaches closely to that of C. quoyii in the Strait of Malacca (Fig. 11). In western Malaysia the southernmost record of the new species is from Langkawi, while C. quoyii has been recorded from Kelang, 420 km to the south. One sample from northeastern Sumatra (RMNH 175798) contains four typical C. quoyii and one of the form described here, indicating that they remain distinct where their ranges meet. It is therefore predicted that these shells represent a genetically distinct species. The most significant characters are the rounded whorls, 5–6 weak spiral ridges on the spire whorls and the strong, numerous axial ribs continuing after the ventrolateral varix. The Andaman Sea is an area of lower nutrient status and clear water, implying that this species is more ‘oceanic’ in its habitat range than C. quoyii, which is found in turbid conditions on the nutrient-rich continental shores of Southeast Asia.
The shell is similar to that of some forms of the variable C. anticipata from Australia (Fig. 10A–P), but the periphery is more angular and the peristome consequently slightly quadrate, rather than round. The ranges of these two taxa are widely disjunct.
description: Published as part of Reid, David G., 2014, The genus Cerithidea Swainson, 1840 (Gastropoda: Potamididae) in the Indo-West Pacific region, pp. 1-65 in Zootaxa 3775 (1) on page 42, DOI: 10.11646/zootaxa.3775.1.1, http://zenodo.org/record/285731