Pearsonia tembatensis, Marzuki & Clements, 2013

Marzuki, Mohammad Effendi bin & Clements, Gopalasamy Reuben, 2013, A New Species Of Cyclophorid Snail (Mollusca: Prosobranchia) From Terengganu, Peninsular Malaysia, Raffles Bulletin of Zoology 61 (1), pp. 21-24 : 22-23

Pearsonia tembatensis , new species

( Figs. 1 , 2 )

Material examined. — Holotype – 1 ex. SH. 8.6 mm × SW. 23.8 mm ( ZRC. MOL.3074), on leaf litter near waterfall, Tembat Forest Reserve (5°03'55.9"N, 102°31'31.9"E), Terengganu, Peninsular Malaysia, coll. M. E. Marzuki & R. Clements, May 2011.

Paratype — 1 ex. SH. 11.8 mm x SW. 27.0 mm ( ME2011 /0186), on leaf litter, Tembat Forest Reserve (5°03'55.9"N, 102°31'31.9"E), Terengganu, Peninsular Malaysia, coll. M. E. Marzuki & R. Clements, May 2011 .

Diagnosis. — Shell medium-sized, widely umbilicated, dextral, rather thick. Colour brown, translucent, shiny, crossed by narrow peripheral band. Whorls five, slowly increasing; periphery rounded. Radial sculpture ornamented with fine, irregularly growth lines below suture and around umbilicus; spiral sculpture absent. Apex smooth, more or less rounded with inconspicuous growth lines. Wrinkled, irregular diffuse blotches appear after 3½ whorl, becoming inconspicuous after 4½ whorls. Spire flatly discoid, very low, slightly raised above body whorl, ornamented with faint, pale brown stripe at 4½ whorl. Suture deeply impressed; sutural tube short, opening slightly backwards behind peristome, about 2 mm in length. Aperture circular, oblique, white with double peristome; inner thickened while outer peristome reflected and expanded at suture forming an open descending wing identical to Pterocyclos . Operculum corneous, roundly convex, multispiral, ciliated on raised edge, smooth at centre. Animal grey, spotted, foot light brown.

Etymology. — This new species is named after its type locality, Tembat Forest Reserve, Terengganu. We chose this name to highlight the biological importance of this forest reserve, portions of which are currently being cleared for a dam.

Remarks. — Based on our comparisons with a fairly complete collation of cyclophorid literature (i.e., Morlet, 1892; Kobelt, 1902, 1908; Gude, 1921; Yen, 1939), we assigned our new species to the genus Pearsonia based on a general agreement with the original shell description in German (translated by F. Köhler) by Kobelt (1902): “Shell discoid, with thick, sometimes hairy periostracum. Aperture circular with thin small tubular pore behind the lip opening backwards. Operculum, non-calcareous, multispiral, outside convex, inside flat. Outer whorls flaring.”

Pearsonia (and our new species) can be differentiated from Pterocyclos (Benson, 1832) and Crossopoma ( Martens, 1891) by the presence of a sutural tube just behind the aperture ( Kobelt, 1902; Gude, 1921). Pearsonia is clearly distinct from Cyclotus ( Swainson, 1840) , which does not have a sutural tube. Although both Pearsonia and Opisthophorus (Benson, 1851) possess a sutural tube, the tube of the latter genus is significantly longer, and turns either upwards or downwards as it decreases in length. Unlike Pearsonia ( Godwin-Austen, 1889; Stoliczka, 1872), the edges of the operculum in Cyclotus and Opisthophorus are not raised.

There is no other representative of Pearsonia from Malaysia for comparison. Among Malaysian cyclophorids, P. tembatensis new species, has the closest affinity with Cyclotus umbraticus Benthem-Jutting, 1949 from Larut hill [Pahang], but again, the latter species does not have a sutural tube and its shell sculpture has a zigzag-like pattern.

Within Pearsonia , P. tembatensis is closely related to P. putaoensis ( Godwin-Austen, 1915) and P. minimum ( Godwin-Austen, 1915) from the Indian region. However, the shells of the latter two species are significantly smaller and their shell sculpture comprises fine transverse striae on the epidermis. Furthermore, the outer peristome of P. minimum is very simple and only slightly reflected. We hope that future phylogenetic studies incorporating molecular, conchological and anatomical data on cyclophorids will include this new species in order to validate our hypothesis.

Based on the geographical distribution of Pearsonia , it is highly likely that our new species belongs to this genus. To date, there are 22 species in the genus Pearsonia found mostly within the Indo-Malayan region. This new species represents the southernmost extent of Pearsonia ’s distribution in Indo-Malaya ( Fig. 3 ).

Figures

Fig. 1. Shell of Pearsonia tembatensis, new species, Terengganu, Peninsular Malaysia. Holotype (ZRC.MOL.3074): a, ventral view; b, dorsal view; c, aperture view; d, side view; e, interior view of operculum; f, side view of operculum; and g, exterior view of operculum. Arrow indicates position of sutural tube.

Fig. 2.Animal of Pearsonia tembatensis, new species, Terengganu, Peninsular Malaysia. The body is grey and spotted and the foot is lightish brown. (Photograph by: Tan Siong Kiat).

Fig. 3. Distribution of worldwide Pearsonia spp. based on approximate location of type localities: 1, Pearsonia travancorica (Blanford, 1880); 2, P. fairbanki (Blanford, 1869); 3, P. beddomei Blanford, 1866; 4, P. hispida (Pearson, 1833); 5, P. assamensis Fulton, 1900; 6, P. nagaensis (Godwin-Austen & Beddome, 1894); 7, P. mastersi (Hanley & Theobald, 1870); 8, P. simplex (Nevill, 1878); 9, P. nevilli (Godwin-Austen, 1876); 10, P. plana (Godwin-Austen, 1915); 11, P. luyorensis Godwin-Austen, 1915; 12, P. oakesi (Godwin-Austen, 1915); 13, P. minima (Godwin-Austen, 1915); 14, P. kempi Godwin-Austen, 1915; 15, P. putaoensis (Godwin-Austen, 1915); 16, P. andersoni Blanford, 1869; 17, P. bhamoensis Theobald, 1876; 18, P. bitubifera Theobald, 1876; 19, P. avana; 20, P. massiei (Morlet, 1892); 21, P. gredleri Yen, 1939; and 22, P. tembatensis Marzuki & Clements, 2013.