Cerithidea andamanensis, Reid, David G., 2014

Reid, David G., 2014, The genus Cerithidea Swainson, 1840 (Gastropoda: Potamididae) in the Indo-West Pacific region, Zootaxa 3775 (1), pp. 1-65 : 42

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.

Figures

FIGURE 11. Distribution of Cerithidea anticipata (squares), C. reidi (stars), C. quoyii (circles), C. andamanensis n. sp. (crosses) and C. dohrni (triangles). Solid symbols, specimens examined; open symbols, literature records: A, Houbrick (1986); B, Quoy & Gaimard (1834); C, Morlet (1889).

FIGURE 12. B – J, Cerithidea quoyii. K – P, C. andamanensis. A, Q – CC, C. dohrni. A, Specimen labelled as a syntype of Cerithium quoyii Hombron & Jacquinot, 1834, ‘ Borneo’ (MNHN 25693), but this is not accepted (see text). This shell is probably a specimen of C. dohrni. B, Uglam Hujung, Kudat, Sabah, Malaysia (NHMUK 20130247). C, Ban Na Glua, Chantaburi, Thailand (NHMUK 20130248). D – G, C. quadrata G. B. Sowerby II, 1866, syntype, Melaka, Malaysia (NHMUK 20130228; views of same specimen). H – J, Ubin I., Singapore (NHMUK 20130249; I, J views of same specimen). K – N, C. andamanensis n. sp., holotype, King I., Mergui Arch., Burma (NHMUK 1887.3.10.24; views of same specimen). O, juvenile, Ao Nam Bor, Phuket I., Thailand (NHMUK 20130250). P, Andaman Is (NHMUK 20130251). Q, Manila, Philippines (NHMUK 20130252). R, Iwahig, Palawan, Philippines (USNM 862793). S – V, no locality (NHMUK 20130253; views of same specimen). W, X, Cavite, Luzon, Philippines (USNM 232955). Y, Z, Cerithium (Cerithidea) kieneri var. dohrni Kobelt, 1890, lectotype, Philippines (SMF 228131). AA, Lapu Lapu, Mactan, Philippines (NHMUK 20130254). BB, Abatan R., Bohol, Philippines (NHMUK 20130255). CC, Abatan R., Bohol, Philippines (MNHN M 49 / BC 2153). Photography credits: A, MNHN; Y, Z, S. Hof, courtesy R. Janssen, SMF.

FIGURE 10. A – P, Cerithidea anticipata. Q – V, C. reidi. A, Cerithium kieneri Hombron & Jacquinot, 1848, holotype, Raffles Bay, Coburg Peninsula, Northern Territory, Australia (MNHN 25692). B, C, Buffalo Creek, Northern Territory, Australia (NHMUK 20130241). D, Casuarina Beach, Northern Territory, Australia (NHMUK 20130242). E – G, Kokenau, Mimika R., East Papua, Indonesia (AM C. 458258). H, I, Rowes Bay, Townsville, Queensland, Australia (NHMUK 20130243). J, Moa I., Torres Strait, Queensland, Australia (NHMUK 20130244). K – M, Moreton Bay, Queensland, Australia (NHMUK 20130245; views of same specimen). N – P, Merauke, East Papua, Indonesia (AM C. 121289; N, O views of same specimen). Q – V, Willies Creek, N of Broome, Western Australia (NHMUK 20130246; same lot as type series; T – V views of same specimen). Photography credit: A, MNHN.