Plectopylis bensoni Gude, 1914

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 79-85

Plectopylis bensoni Gude, 1914

Figs 2 , 34E , 35C , 36 A–F, 37, 38A–B

Helix achatina Pfeiffer, 1845: 86 [“Südamerika”].

Helix repercussa Gould, 1856: 11 [“Tavoy and Mergui”]. Syn. nov.

Plectopylis achatina var. obesa Gude, 1898e: 115 , fig. 83a–c. Syn. nov.

Plectopylis achatina var. infrafasciata Gude, 1898f: 133 , fig. 84a–f. Syn. nov.

Plectopylis achatina var. venusta Gude, 1898f: 133 , fig. 85a–c. Syn. nov.

Plectopylis achatina var. castanea Gude, 1898f: 133–134 , fig. 86a–c. Syn. nov.

Plectopylis achatina var. breviplica Gude, 1898f: 134 , fig. 87a–c. Syn. nov.

Plectopylis achatina var. repercussoides Gude, 1899a: 333 . Syn. nov.

Plectopylis (Plectopylis) bensoni, Gude 1914b: 138–141 , figs 70–72.

Helix (Atopa) achatina – Albers 1850: 90.

Helix (Corilla) achatinum – Adams & Adams 1855: 208.

Helix achatina – Benson 1859c: 95 [“near Moulmein”]. — Pfeiffer 1868: 395.

Helix (Plectopylis) achatina – Benson 1860: 244, 245. — Hanley & Theobald 1870: 7, pl. 13, fig. 1. — Godwin-Austen 1875b: 613, pl. 74, fig. 6–6a. — Nevill 1878: 71. — Kobelt 1879: 236, pl. 71, fig. 9. — Tryon 1887: 165, pl. 35, figs 3–5, 7–8. — Tapparone Canefri 1889: 47 (= 323). — Godwin- Austen 1895: 155. pl. 7, fig. 5.

Helix repercussa – Pfeiffer 1868: 396. — Gude 1898d: 74, fig. 78a–i.

Plectopylis achatina – Stoliczka 1871: 221–222, pl. 15, figs 1–3. — Pilsbry 1894: 145, pl. 40, figs 5–8. — Gude 1898e: 114–115, figs 80–82.

Helix (Plectopylis) repercussa – Hanley & Theobald 1870: 7, pl. 13, fig. 4. — Nevill 1878: 72. — Tryon 1887: 165 (synonym achatina ).

Plectopylis (Plectopylis) achatina ( var. repercussoides , var. infrafasciata , var. castanea , var. obesa , var. venusta , var. pachystoma Theob. M.S. , var. breviplica ) – Gude 1899d: 148.

Plectopylis (Plectopylis) repercussa – Gude 1899d: 148; 1899e: 175; 1914b: 146–149, fig. 78a–i. — Johnson 1964: 139, pl. 37, fig. 3.

Plectopylis (Plectopylis) achatina – Gude 1899e: 175.

Plectopylis achatina var. obesa – Gude 1900a: 35–36, fig. 13a–c.

Plectopylis achatina var. infrafasciata – Gude 1900a: 36–37, fig. 14a–c.

Plectopylis achatina var. venusta – Gude 1900a: 37–38, fig. 15a–c.

Plectopylis bensoni var. repercussoides – Gude 1900b: 91.

Plectopylis repercussa – Gude 1900b: 91.

Plectopylis (Plectopylis) bensoni var. repercussoides – Gude 1914b: 141–142.

Plectopylis (Plectopylis) bensoni var. infrafasciata – Gude 1914b: 142–143, fig. 73a–c.

Plectopylis (Plectopylis) bensoni var. castanea – Gude 1914b: 143, fig. 74a–c.

Plectopylis (Plectopylis) bensoni var. obesa – Gude 1914b: 143–144, fig. 75a–c.

Plectopylis (Plectopylis) bensoni var. venusta – Gude 1914b: 144–145, fig. 76a–c.

Plectopylis (Plectopylis) bensoni var. breviplica – Gude 1914b: 145–146, fig. 77a–c.

Plectopylis (Plectopylis) bensoni – Zilch 1960: 595, fig. 2095.

Diagnosis

A very variable species with medium-sized to very large, flat shell, shouldered body whorl due to flat dorsal side (although edge of body whorl rounded), strong main plica, which is connected to both the anterior lamella and the apertural fold, lower plica usually reaches the peristome.

Type material

The original description ( Pfeiffer 1845) was based on a single specimen from the private collection of J.E. Gray, and was said to be collected in South America (“soll aus Südamerika herstammen”). This locality was questioned later ( Pfeiffer 1848b: 406), and in the 5 th edition of the Monographiae Heliceorum Viventium, Pfeiffer (1868) designated “Farm Caves, prope Moulmein” as the locality of the species. The location of the single shell (holotype) is unknown, and it is most probably lost. Pfeiffer’s collection was destroyed during WWII ( Dance 1986). If not destroyed, there are two possibilities where the holotype could be: either in the collection of Cuming, or the shells could have remained in the collection of Gray. Both collections are deposited in the NHM ( Dance 1986). I have been unable to locate the holotype there. Since this is the type species of Plectopylis , which is the type genus of the family Plectopylidae , I found it necessary to select a neotype. The shell detailed below, collected at the type locality, is therefore designated as the neotype.

Material examined

Neotype (here designated)

MYANMAR: 1 shell, Kha Yon Caves , approx. 16°32′ N, 97°42.9′ E, 15 Oct. 2009, K. Okubo leg. ( NHMUK 20170143 , ex coll. K. Okubo).

Other types

MYANMAR: 1 shell, lectotype of P. repercussa, Burmah, Tavoy and Mergui , coll. Gould ( MCZ 169336); 3 shells, paralectotypes of P. repercussa, Burmah, Tavoy ( NHMUK 20140813); 1 shell, holotype of P. bensoni var. castanea, Moulmein , coll. Linter ( NHMUK 1922.8.29.45); 1 shell, holotype of P. bensoni var. infrafasciata, Moulmein , coll. Linter ( NHMUK 1922.8.29.43); 1 shell, holotype of P. bensoni var. obesa, Moulmein , coll. Linter ( NHMUK 1922.8.29.42); 1 shell, holotype of P. bensoni var. repercussoides, Moulmein , coll. Linter ( NHMUK 1922.8.29.46); 1 shell, holotype of P. bensoni var. venusta Moulmein , coll. Linter ( NHMUK 1922.8.29.44).

The lectotype of P. repercussa was selected by Johnson (1964). According to the original description of P. bensoni var. breviplica , the holotype is in the collection of Mr Ponsonby, but it was not found in the NHM.

Additional material

MYANMAR: 1 shell, Birmanie, coll. Denis ( MNHN IM- 2012-2516); 7 shells, Birmanie, Moulmein, Mission L. Fea, 1885–1889 (MNHN-IM- 2012-2517); 2 shells, Birmanie, coll. Jousseaume ( MNHN- IM- 2012-2518); 8 shells, Indien, Moulmein ( NHMS 122182–122189); 1 shell, Moulmein ( NHMS 122180); 1 shell, Ost-Indien, ex coll. Dr. Holub 1896 ( NHMS 4923); 1 shell, Mergui, Fulton leg., coll. Möllendorff ( SMF 150096); 2 shells, (“ var. infrafasciata ”), Burma, coll. Bosch ex Rolle ( SMF 172061); 1 shell, Barma, coll. Möllendorff ( SMF 150094); 2 shells (“ achatina obesa ”), Burma, coll. Bosch, ex Rolle ( SMF 172060); 1 shell (“ v. castanea ”, mixed sample with P. anguina ), Burma, coll. Bosch ex Rolle ( SMF 172059); 2 shells, Indien, Moulmein, coll. Jaeckel ex Edlauer ( SMF 212737); 2 shells, Indien, Moulmein, coll. Bosch, ex Rolle ( SMF 172057); 1 shell, Moulmein, coll. Pfeiffer ex Staudinger ( SMF 102813); 3 shells, Moulmein, coll. Jetschin ex Linter 1893 ( SMF 102822); 2 shells, Moulmein, coll. Kobelt 1876, ex-exhibition coll. “alte Schau-Slg.” (photographed in Zilch 1960) ( SMF 150088); 3 shells, Birma, coll. Möllendorff ex Beddome ( SMF 150091); 3 shells (not typical form with elevated spire), Attaram-Tal, coll. Möllendorff ( SMF 150092); 2 shells, Moulmein, coll. Ehrmann ex Staudinger ( SMF 150093); 1 shell, Burma, coll. Reinhardt ( SMF 150098); 3 shells, Burma, Moulmein, coll. Möllendorff ( SMF 150090); 2 shells, Burma, Moulmein, coll. C. Boettger, 1908 ( SMF 102814); 3 shells (labelled as “ anguina ″), Burmah, Mergui ( NHMUK); 2 shells (under the name anguina ), Burmah, Moulmein, coll. A. S. Kennard, coll. Gude ( NHMUK); 1 shell, Birma, coll. Bosch, ex Rolle ( SMF 172063); 1 shell, Moulmein (ZMUC-GAS-1802); 1 shell, Moulmein, coll. Steenberg (ZMUC-GAS-1803); 1 shell, Indien, Linter leg., 1906, coll. Steenberg (ZMUC-GAS-1801); 1 shell, Moulmein, Bostre Indien, coll. Steenberg ex Dr. Stoliczka (ZMUC-GAS-1815); 4 specimens (ethanol-preserved bodies + corresponding shells), Kayin, West foot of Zwegabin Mt., Pha-an, loc. 20091014A, 16°49.676′ N, 97°40.504′ E, 31 m a.s.l., 14 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB); 1 specimen (shell + anatomically examined body), same data as for preceding ( NHMUK 20170152); 6 shells, Kayin, West foot of Zwegabin Mt., 16°49.552′ N, 97°40.603′ E, 24 m a.s.l., 14 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Ohara); 2 shells, Kayin, Pha-an, east foot of Mt. Zwegabin, loc. 20091014C, 16°48.783′ N, 97°40.395′ E, 14 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Okubo); 1 shell (protoconch examined by SEM), same data as for preceding (coll. PGB); 4 shells, same data as for preceding (coll. PGB, ex coll. K. Ohara); 1 shell, Kayin, [rubber plantation] Pha-an, opposite side of point C, 16°48.693′ N, 97°39.809′ E, 32 m a.s.l., 14 Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. J.U. Otani); 1 shell, Pha An, Bayin Nyi Cave, ca 16°58.225′ N, 97°29.614′ E, 13. Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Okubo); 1 shell, Kayin, Sadsar [Saddan] Cave, Pha-an, 16°44.414′ N, 97° 43.114′ E, 50 m a.s.l., 14. Oct. 2009, K. Ohara, K. Okubo and J.U. Otani leg. (coll. PGB, ex coll. K. Okubo).

SRI LANKA: 1 shell, Tinter [probably Linter] leg. ( HNHM 62599); 2 shells, Ceylon, coll. Kovács, Gy. ( HNHM 67067); 4 shells, Ceylon, ex coll. Oberwimmer ( NHMS 122190 – 122193); 3 shells, Ceylon(?), coll. Krüper ex Oberwimmer ( SMF 102809); 1 shell, Ceylon, Colombo, coll. Jetschin ex Oberwimmer ( SMF 102810); 2 shells, Ceylon, coll. Bosch, ex Rolle ( SMF 172058); 1 shell, Ceylon, coll. Jetschin ex Oberwimmer ( SMF 102812).

LOCALITY UNKNOWN: 2 shells ( SMF 150087); 2 shells (labelled as anguina ) ( NHMUK).

Description

SHELL. Sinistral, flat, but protoconch usually protrudes above dorsal surface; colour variable, from yellowish to blue and flesh-coloured/reddish (usual); shells usually not monochrome, but with lighter stripes of variable thickness; ventral shell surface usually much lighter than dorsal side; protoconch large, consists of 3.25–3.75 whorls, very finely, irregularly wrinkled; ca first whorl of teleoconch with reticulated sculpture; following ca 1.5 whorls rather glossy, with rough, irregular wrinkles; body whorl rounded or slightly, bluntly keeled, above and below shouldered; aperture oblique, oval; peristome strongly expanded and reflected; parietal callus strongly developed, blunt, slightly S-shaped; apertural fold usually strong, connected to parietal callus; umbilicus wide, without periumbilical keel.

Four opened shells were examined. Lambda-complex complete; upper branch does not extend beyond left leg; right leg long or very long; main plica connected to lambda-complex, continuous with apertural fold; lower plica starts below lambda-complex and runs until peristome, or in some populations stops in the middle. Palatal plicae six; first relatively short, situated close to suture; second strongly elongated anteriorly, with a dichotomous posterior end; third shorter, its posterior end descends in direction of lower suture; fourth and fifth form a vertical plate, with one or two additional denticles on posterior side, near its lower end; sixth short, curved.

MEASUREMENTS (in mm). D = 17.7–31.3, H = 7–9.1 (smallest and largest specimens found in the NHM); D = 26.2–28.8, H = 8.6–9.1 ( repercussa , NHMUK paralectotypes); D = 23.8, H = 8.1 (holotype of achatina var. castanea ); D = 17.7, H = 7 (holotype of achatina var. venusta ); D = 27.3, H = 8.8 (holotype of achatina var. repercussoides ); D = 21.8, H = 8.6 (holotype of achatina var. infrafasciata ); D = 19.3, H = 7.5 (holotype of achatina var. obesa ). Stoliczka (1871) mentioned that the largest shell was 35 mm in width.

CHARACTERS OF THE GENITAL STRUCTURE. Two specimens were anatomically examined (NHMUK 20170152).

Left ommatophoral retractor crosses penis and vagina; atrium very short; penis with a longer, cylindrical proximal, and a shorter, also cylindrical but slightly thicker distal portion; penis internally with approx. 10 longitudinal, serrate folds without calcareous granules; epiphallus slightly shorter than distal part of penis; internally with 4–5 strong, longitudinal folds; distal part of penis and epiphallus bound together with weak muscle fibres; a short, blunt penial caecum discernible; retractor muscle slender, flat, and inserts on penial caecum; vas deferens slender, even near its insertion to pedunculus; it is bound to distal part of penis and vagina by weak membrane; vagina approximately as long as penis, flattened at its curving point (this is the point where vaginal bulb is developed in some specimens), otherwise rather cylindrical; uterus with three large, elongated embryos in one specimen; diverticulum triangular, robust, short, bursa copulatrix with very long, slender stalk, bursa elongate oval; a long, club-like, easily weathering spermatophore was found in bursa; slender end of spermatophore curly; whole surface of spermatophore finely wrinkled; spermatophore internally not structured.

RADULA. Centrals with small, triangular cusps; endocones of laterals wide ovoid with pointed tips; ectocones of first laterals much larger than centrals; ectocones of marginals undivided, endocones of marginals mostly undivided or divided by shallow incision. See also under radula of Plectopylis cyclaspis .

Differential diagnosis

See under P. anguina , P. cairnsi and P. linterae .

Distribution

The species has been reported from several southern localities in Myanmar. Georeferenced sites are known from the limestone hills of the Kayin and Mon States. Although many historical samples are recorded as from from Sri Lanka or Ceylon, these probably all represent erroneous localities on the labels (see also Fig. 12 ), because no plectopylid has been found in Sri Lanka recently (D. Raheem, pers. comm., 2017 January), and this distribution type is highly unlikely from a biogeographical point of view.

Remarks

Plectopylis achatina was described by L. Pfeiffer (1845) as “ Helix achatina Gray ”. However, Gray never described this taxon, so the author should be considered as Pfeiffer. For a long time this species was called Plectopylis achatina Pfeiffer, 1845 . That name, however, was already occupied by Helix achatina Gmelin, 1791 (see Gmelin 1791). Therefore, Gude proposed the replacement name Plectopylis bensoni .

The only remarkable difference between Plectopylis repercussa and P. bensoni is the strongly elongated upper branch of the lambda-complex in P. repercussa , which differs from the shorter upper branch of P. bensoni . This, however, does not allow the distinction of the two species, which otherwise do not differ in general shell shape. Moreover, P. bensoni var. repercussoides is described as an “intermediate between typical P. bensoni and P. repercussa ” ( Gude 1914b) . I therefore treat P. repercussa as a synonym of P. bensoni .

One sample (“Attaram-Tal”, coll. Möllendorff, SMF 150092) had three shells with a somewhat elevated spire and a slightly keeled body whorl (similar to that of Plectopylis anguina ). This sample might be a locally isolated form with peculiar shell characters.

Figures

Fig. 2. A. Nomenclature of the genital system of the Plectopylinae (Plectopylis bensoni Gude, 1914: 20091014A, OP7). B. Central and first lateral teeth. C. Marginal teeth. Abbreviations: A = atrium; AG = albumen gland; B = bursa of the bursa copulatrix; BS = stalk of the bursa copulatrix; C = central tooth; D = diverticulum; E = epiphallus; EcL = ectocone of a lateral tooth; EcM = ectocone of a marginal tooth; EnL = endocone of a lateral tooth; EnM = endocone of a marginal tooth divided slightly in the middle; P = penis; PC = penial caecum; RM = retractor muscle of the penis; SO = spermoviduct; T = talon; V = vagina; VB = vaginal bulb; VD = vas deferens. Scale bar: A = 2 mm; B–C not to scale.

Fig. 34. Shells of species of Plectopylis Benson, 1860. A. P. anguina (Gould, 1847), paralectotype (NHMUK 20140812). B. P. cairnsi Gude, 1898, holotype (NHMUK 1922.8.29.47). C. P. cairnsi (UF 76761). D. P. bensoni Gude, 1914, paralectotype of Helix repercussa Gould, 1856 (NHMUK 20140813). E. Neotype of P. bensoni (NHMUK 20170143). Scale bar = 10 mm. Photos: T. Deli (C), B. Páll-Gergely (E) and H. Taylor (A–B, D).

Fig. 35. Parietal (A–E, G, I–L, N) and palatal (F, H, M, O) plication of species of Plectopylis Benson, 1860. A. P. anguina Gould, 1847, paralectotype (NHMUK 20140812). B. P. repercussa Gould, 1856, lectotype (MCZ 169336). C. P. bensoni var. repercussoides Gude, 1899, holotype (NHMUK 1922.8.29.46). D. P. cairnsi Gude, 1898, holotype (NHMUK 1922.8.29.47). E–F. P. cairnsi (UF 76761). G–H. P. crassilabris sp. nov., paratype (UF 448577). I. P. cyclaspis Benson, 1859 (NHMUK 1906.02.02.148). J. P. karenorum (W. Blanford, 1865) from “Pegu”, Myanmar (NHMUK). K. P. linterae var. fusca Gude, 1898 (NHMUK 1888.12.04.1541–3). L–M. P. malayana sp. nov., paratypes from the type locality (coll PGB). N–O. P. thompsoni sp. nov., paratype (UF 448578). Arrows below the letters indicate the direction of the aperture. Not to scale.

Fig. 36. Shells of Plectopylis bensoni Gude, 1914. A. Holotype of var. obesa Gude, 1898 (NHMUK 1922.8.29.42). B. Holotype of var. infrafasciata Gude, 1898 (NHMUK 1922.8.29.43). C. Holotype of var. venusta Gude, 1898 (NHMUK 1922.8.29.44). D. Holotype of var. castanea Gude, 1898 (NHMUK 1922.8.29.45). E. Holotype of var. repercussoides Gude, 1899 (NHMUK 1922.8.29.46). F. Protoconch of Plectopylis bensoni, loc. 20091014C (coll. PGB). Scale bars: A–E (upper scale) = 10 mm; F (lower scale) = 2 mm. Images: H. Taylor (A–E) and B. Páll-Gergely (F).

Fig. 12. Distribution of plectopylid species in Thailand, Laos and Myanmar. Legends: circle = Chersaecia shanensis (Stoliczka, 1873); filled square = Chersaecia reversalis sp. nov.; empty square = Chersaecia dextrorsa (Benson, 1860); empty rhomb = Hunyadiscus tigrina sp. nov.; filled rhomb = Hunyadiscus saurini Páll-Gergely, 2016; triangle, top up = Plectopylis crassilabris sp. nov.; triangle, top down = Naggsia laomontana (L. Pfeiffer, 1862); empty triangle, top down = Plectopylis bensoni Gude, 1914.