Bensonella novemdentata ( Saurin, 1953 ), 2024

Bensonella novemdentata ( Saurin, 1953) View in CoL new combination

( Fig. 4 View Fig )

Boysidia novemdentata Saurin, 1953: 115 View in CoL , 116, fig. 1, and pl. 4, fig. 4a–c. Type locality: environs du village méo de Pah Hia, à 100 kilomètres au Sud de Xieng-Khouang, chef-lieu de la province du Tran Ninh, Laos [probably refers to Ban Namthong, Longchaeng District, Xaisomboun Province, Laos]. Inkhavilay et al., 2019: 59 View Cited Treatment , fig. 26b.

Material examined. Syntype MNHN-IM-2000-33881 (1 shell; Fig. 4A View Fig ) from Pah Hia. CUMZ 14426 View Materials (1 shell; Fig. 4B View Fig ) from limestone outcrop at Ban Lao , Samtay District, Houaphanh Province, Laos (20°00′52.4″N, 104°40′57.0″E), coll. K. Inkhavilay, A. Inthavong, and C. Oulaiseng, May 2022 GoogleMaps .

Diagnosis. Shell elongate-conic, yellowish brown in colour. Cervical crest situated far from peristome. Aperture with eight teeth (i.e., parietal, infraparietal, angular, columellar, basal, and upper, inter and lower palatals), not hooked.

Description. Shell conical, yellowish brown to reddish brown with 5¼ to 6 widely convex whorls. Apex rather blunt; protoconch about 1½ whorls with wrinkles, very weak spiral ridges. Teleoconch with strong, irregular growth lines and conspicuous; suture impressed and deep. Last whorl large, rounded. Peristome thickened, slightly expanded; constriction weak; lip reddish brown. Cervical crest rather sharp, situated close to peristome. Aperture subquadrate with many apertural dentitions. Parietal lamella (p) strongly developed, rectangular. Infraparietal lamella (ip) small and blunt. Angular lamella (a) slightly higher than parietal lamella, sinuous: outer part short, low, reaching peristome; inner part strongly elevated. Palatal tubercle (pt) strongly developed with triangular shape; one upper palatal plica (upl) with strong folding; one inter- (itpl) and one lower (lpl) palatal relatively large, nearly equal in size, strong plica. Basal plica (b) small, low, tubercle-like. Columellar lamella (c) large, strong, distinct horizontally. Umbilicus narrowly perforate, about one-fifth of shell width, rounded, deep.

Distribution. This species was previously known only from the type locality ( Saurin, 1953; Inkhavilay et al., 2019) and is newly recorded from Houaphanh Province in northern Laos. The snails live on limestone karsts and can be found on the limestone wall together with Boysidia houaphanica , new species.

Remarks. The recently collected specimens are from Houaphanh Province, which is about 200 km east of the “type locality, which is stated to be ‘Pahai’”. However, the morphology of our specimens deviates slightly from that of the syntype ( Fig. 4A View Fig ) in having a more rounded whorl and deeper suture ( Fig. 4B View Fig ). Otherwise, the number and arrangement of the apertural dentitions are practically identical with the syntype.

Among the morphologically similar species recorded from Laos, Bensonella novemdentata differs from Bensonella paviei ( Bavay & Dautzenberg, 1912) and Bensonella anguloobtusa ( Inkhavilay & Panha, 2016 in Inkhavilay et al., 2016) by having a prominent cervical crest and palatal plicae forming a short tubercle and situated near the aperture. In comparison, the latter two species have very weak to no cervical crest and palatal plicae extending far inside the aperture; Bensonella anguloobtusa further possesses a subcolumellar plica without lower parietal lamella. In addition, Bensonella novemdentata can be differentiated from Bensonella paralella ( Inkhavilay & Panha, 2016) by having a subrectangular aperture and prominent interpalatal and cervical crest, while Bensonella paralella possesses an ovate-shaped aperture, and without interpalatal plica and cervical crest ( Inkhavilay et al., 2016; Páll-Gergely & White, 2022; Tongkerd et al., 2024).

The two species, Bensonella wangviangensis ( Panha & Tongkerd, 2003) and Bensonella gittenbergeri ( Maassen, 2008) , previously known from Laos, clearly differ from this species in both shell shape and apertural dentition. For comparison, Bensonella wangviangensis has a small shell (height ≤ 2 mm) with 4 whorls, without basal plica, the parietal wall at the posterior corner elevated, and an aperture elliptical with prominent posterior corner balloonshaped, formed by angular lamella and upper palatal plica. Meanwhile, Bensonella gittenbergeri has a large shell (height 4–6 mm), ovate conic shape, inconspicuous palatal tubercle, and lower palatal long, reaching expanded lip ( Panha et al., 2003; Maassen, 2008; Inkhavilay et al., 2016).

Regardless of their phylogenetic relationships, the traditional diagnostic characters set by their respective type species, Boysidia and Bensonella , share a peristome being adnate to the last whorl and lacking the free portion of the last whorl (tuba). In contrast, Boysidia has one parietal lamella (without angular lamella), while Bensonella has separate parietal and angular lamellae. Based on that criterion of generic classification, the species ‘ Boysidia novemdentata ’ is placed under the Boysidia ( Saurin, 1953; Inkhavilay et al., 2019; MolluscaBase, 2024). However, the syntype ( Fig. 4A View Fig ) has well-separated parietal and angular lamellae and peristome adnate to the preceding whorl; these are the unique characteristics of Bensonella ( Pilsbry & Vanatta, 1900; Pilsbry, 1917; Schileyko, 1998; Páll-Gergely & White, 2022). Therefore, we have transferred this species into a more appropriate genus, Bensonella .