Tropidophora secunda Fischer-Piette & Bedoucha, 1965

Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, African Invertebrates 54 (1), pp. 1-48 : 10-12

Tropidophora secunda Fischer-Piette & Bedoucha, 1965

Figs 7 , 8 , 25C

Cyclostoma reticulatum: Reeve 1861 : pl. 9, fig. 48a, b [non Adams & Reeve 1850 in 1848–1850: 57, pl. 14, fig. 8].

Tropidophora reticulata: Fischer-Piette 1949: 36 .

Tropidophora secunda: Fischer-Piette & Bedoucha 1965: 76 . Type loc.: Madagascar.

Tropidophora (Ligatella) secunda: Fischer-Piette et al. 1993: 129 , fig. 82.

Morphological notes:

External features ( Fig. 25C ): Head-foot more or less uniformly grey; tentacles and forehead slightly darker, paler toward mantle cavity; tip of snout conspicuously indented in mid-line; skin texture very finely granular.

Operculum: Oligospiral; exterior portion a calcareous disc, attached to an inner and slightly larger corneous layer; external surface very shallowly concave, lacking a distinct convex spiral ridge (cf. T. humbug above), but with a diffuse, dark purple-brown spiral band more or less at mid-whorl, most noticeable on last whorl; edge of disc concave, with relatively weakly developed transverse partitions (adjacent to inner surface), except along smooth growing margin.

Radula ( Fig. 8 ): Formula 1+2+1+2+1; length 7.3 mm, ca 42 rows/mm; dentition fine. Rachidian with five distinct cusps, a minute additional pair sometimes discernable; central cusp largest and rounded, the outer pair small and curving inward. Inner laterals with four cusps, the inner cusp small and often obscured by the much larger second cusp; outer lateral with five or six cusps, the central three or four usually larger. Marginal teeth broad, the edge comprising three regions; an inner coarsely dentate element with ca 9 denticles; a more finely denticulate central region, and a smooth outer portion. Such a radula conforms to the pattern seen in Tropidophora (Ligatella) Martens, 1880 (Fischer-Piette et al. 1969).

Locality data: Tsingy Beanka : st’ns 03/06, 11/06, 12/06, 13/06, 14/06, 15/06, 17/06, 18/06, 02/09, 11/09, R01/10, 03/10, 09/10. Kelifely Plateau: st’ns 04/05, 10/05. Anjajavy (Narinda north): st’ns 33/03, 36/03. 37/03, 38/03, 39/03, 40/03, 13/04 [abundant in this area]. Mtn d’Ambre/Ankarana: st’ns 12b/94, 01/01, 09/01 [uncommon].

Distribution: Central western to north-eastern Madagascar; from the southern Bemaraha region (Fischer-Piette et al. 1993) through Tsingy Beanka , the Kelifely Plateau and Anjajavy area, to Mtn d’Ambre and Ankarana in Antsiranana Province. Curiously, we have not found this species in our own surveys in the Tsingy de Bemaraha, nor at Antsingimavo, and whereas it is common in the southern Tsingy Beanka , it is rare in the central portion. Evidently although relatively widespread, the species has a somewhat patchy distribution within its range.

Habitat: Dry deciduous, evergreen and riverine forest in limestone areas; in leaf-litter and sheltering microhabitats amongst rocks.

Remarks: A characteristic species on account of its bold colour pattern. T. reticulata (Adams & Reeve, 1850) , with which it was at one time confused, has a similar coloration, but is smaller (max. diameter approx. 16 mm, compared to> 18.5 mm in T. secunda ), has a more elevated shell and a narrower umbilicus (Fischer-Piette 1949) ( Fig. 26G–I , syntype, NHMUK). The white markings of T. secunda are not part of the shell fabric, but are a superficial chalky deposit which can be easily scraped off. Although previously reported from few localities, the range of T. secunda is evidently relatively large and it is not uncommon in undisturbed dry forest habitat. In contrast, the range of T. reticulata has yet to be established more precisely than ‘Madagascar’. Most specimens from Tsingy Beanka have a lower spire than the holotype (compare Figs 7A and 7F ); however, shells of intermediate height are present both in the Tsingy Beanka and Kelifely Plateau ( Fig. 5D, E ).

Fischer-Piette and Bedoucha (1965) selected as the ‘type’ for this species the specimen illustrated as Cyclostoma reticulatum by Reeve (1861: pl. 9, fig. 48a, b, ‘Mus. Cuming’), which they stated was present in the ‘British Museum’ [NHMUK]. Fischer-Piette (1949) had earlier examined this specimen, citing its diameter as 22 mm. No specimen identified as the holotype of Tropidophora secunda was present in the NHMUK, but a specimen labelled Cyclostoma reticulatum is present in the Cuming collection (Ablett pers. comm. Nov. 2011). This is 22 mm in diameter and closely resembles the figure given by Reeve (1861), though the colour pattern is not a perfect match. It seems very probable that this is the specimen referred to by Fischer-Piette and Bedoucha (1965), and we consider it to be the holotype of Tropidophora secunda (NHMUK 20110470, Fig. 7F–H ). It is not clear why Fischer-Piette, after having examined the Cuming specimen illustrated by Reeve (1861) and designated it to be the type, subsequently stated for T. secunda ‘localisation du type:?’ (Fischer-Piette et al. 1993).

Figures

Fig. 7. Tropidophora secunda Fischer-Piette & Bedoucha, 1965: (A–C) Tsingy Beanka, st’n 03/06, max. diameter 21.5 mm, NMSA L7040;(D) Tsingy Beanka, st’n 03/06, subadult, max.diameter 20.0 mm, NMSA L7040;(E) Kelifely Plateau, max.diameter 18.8 mm,NMSA L6798; (F–H) holotype (faded), ‘Madagascar’, Cuming collection, max. diameter 22.0 mm, NHMUK 20110470.

Fig. 8. Tropidophora secunda Fischer-Piette & Bedoucha, 1965, radula, NMSA L7040: (A) entire width of radula, scale bar = 200 μm; (B) rachidian and inner lateral teeth, scale bar = 50 μm; (C) outer lateral and marginal teeth, scale bar = 50 μm.

Fig. 25. Living animals from Tsingy Beanka: (A) Acroptychia bathiei Fischer-Piette & Bedoucha, 1965, st’n 13/06, shell diameter 23.2 mm, NMSA L7315; (B) Tropidophora humbug sp. n., st’n 12/06, shell diameter 28.3 mm, paratype,NMSA L7204/T2984; (C) Tropidophora secunda Fischer-Piette & Bedoucha, 1965, st’n 03/06, shell diameter approx.19.0 mm; (D) Clavator griffithsjonesi Emberton, 1999, st’n 12/06, shell height 94.8 mm, NMSA L7192; (E) Ampelita milloti Fischer-Piette,1952,st’n 07/09, shell diameter 19.2 mm, NMSA L8502; (F) Ampelita namerokoensis Fischer-Piette, 1952, st’n 12/06, shell diameter 20.3 mm, NMSA L8442; (G) Kalidos griffithshauchleri Emberton, 2002, st’n 12/06, shell diameter approx. 60 mm; (H) Kalidos maryannae sp. n., st’n 12/06, shell diameter 22.5 mm, paratype, NMSA L7193/T2944.

Fig.26.Speciesillustrated for comparative purposes:(A–C) Tropidophora moulinsii, holotype of Cyclostoma moulinsii Grateloup, 1840, ‘Madagascar’, max. diameter 33.1 mm, NHMUK 1907.11.22.12; (D–F) Tropidophora thesauri Fischer-Piette, 1949, Orangea, Diego Suarez [= Antsiranana] district, max. diameter 38.0 mm, NMSA L8438; (G–I) Tropidophora reticulata, one of three syntypes of Cyclostoma reticulatum (Adams & Reeve, 1850), ‘Madagascar’, max.diameter 15.1 mm, NHMUK 1874.12.11.231; (J–L) Kalidos hova, syntype of Nanina hova Odhner, 1919, Catsèpe, Madagascar, max. diameter 24.4 mm (SMNH).

Fig.5. Tropidophora humbug sp.n.: (A–C) holotype,Tsingy Beanka,max.diameter 31.5mm,height 16.3 mm, AMS C.474165; (D–F) paratype, heavily banded specimen, Tsingy de Bemaraha, max. diameter 30.4 mm, height 14.1 mm, NMSA L8444/T2658; (G) operculum of holotype, external surface, max. diameter 11.0 mm, AMS C.474165.