Sheldonia monsmaripi, Herbert, 2016

Herbert, David G., 2016, New narrow-range endemic land snails from the sky islands of northern South Africa (Gastropoda: Streptaxidae and Urocyclidae), European Journal of Taxonomy 236, pp. 1-29 : 16-21

Sheldonia monsmaripi sp. nov.

urn:lsid:zoobank.org:act:2C26E39F-EB96-4864-8F82-B7ABCBDD0F1F

Figs 8–12

Etymology

From mons (L.) ‘mountain’ and Maripi in reference to Chief Maripi Mashile of the Bapedi tribe, after whom the type locality, Mariepskop, is named.

Material examined

Holotype

SOUTH AFRICA: Mpumalanga, Mariepskop Forest Reserve , 24.59563° S, 30.82600° E, 790 m, indigenous riverine forest, in leaf-litter on forest floor, J. Horn, 25 May 2006, diameter 12.2 mm, height 8.7 mm ( NMSA W4413 /T3300, body in ethanol).

Paratypes

SOUTH AFRICA: Mpumalanga, Mariepskop Forest Reserve, 24.563° S, 30.863° E, 1400 m, indigenous Afromontane forest, A.C. & W.H. van Bruggen, 29 Jan. 1966 (W3653/T3169, nine specimens, bodies in ethanol; ELM D18067/T151, one dry specimen); Mariepskop Forest Reserve, 24.56353° S, 30.86252° E, 1620 m, indigenous Afromontane forest, 3 m above ground in epiphytes of standing tree, J. Horn, stn L42, 22 May 2005 ( NMSA W3679/T3170, one specimen, body in ethanol); Mariepskop Forest Reserve, 24.56374° S, 30.86293° E, 1640 m, northern mist-belt forest, under Streptocarpus leaf on tree trunk, D. Herbert, L. Davis & M. Cole, stn 14-22, 3 Dec. 2014 ( NMSA P0276/T4073, one specimen, body in ethanol); Mariepskop Forest Reserve, Bushpig Trail, 24.56694° S, 30.86270° E, 1491 m, mistbelt forest, A. Moussalli & D. Stuart-Fox, 15 Dec. 2006 ( NMSA W5741/T3171, one specimen, body in ethanol); Mariepskop Forest Reserve, 24.56708° S, 30.85990° E, 1540 m, Afromontane forest, in Clivia cluster on live tree ca 1 m above ground, J. Horn, stn L64, 24 Nov. 2005 ( NMSA W3900/T3172, six specimens, bodies in ethanol; NHMUK 20160039, one dry specimen; RMNH.5004143, one dry specimen); Mariepskop Forest Reserve, 24.56795° S, 30.86138° E, 1520 m, Afromontane forest, in Clivia cluster on live tree, ca 1 m above ground, J. Horn, stn L64, 24 Nov. 2005 ( NMSA W3899/T3173, four specimens, bodies in ethanol); Mariepskop Forest Reserve, Picnic Trail, 24.56847° S, 30.85920° E, 1545 m, northern mist-belt forest, in leaf-litter, D. Herbert, L. Davis & M. Cole, stn 14-27, 4 Dec. 2014 ( NMSA P0228/T4072, five specimens, bodies of two in ethanol); Mariepskop Forest Reserve, 24.59563° S, 30.82600° E, 790 m, indigenous riverine forest, in leaf-litter on forest floor, J. Horn, 25 May 2006 ( NMSA W9581/T3301, one specimen, body in ethanol); God’s Window, 24.8746° S, 30.8909° E, Afromontane forest, active on understorey foliage, A. Moussalli & D. Stuart-Fox, 25 Feb. 2004 ( NMSA W3335/T3178, two specimens, bodies in ethanol); God’s Window, 24.875° S, 30.891° E, rainforest, W. Haselau, Mar. 2006, don. M. Bursey ( NMSA W4858/T3179, three specimens, bodies in ethanol).

Other material

SOUTH AFRICA: Mpumalanga, Mariepskop summit, 24.54933° S, 30.87170° E, 1920 m, rocky Afromontane fynbos, in leaf-litter, D. Herbert, L. Davis & M. Cole, stn 14-21, 3 Dec. 2014 ( NMSA P0278); Mariepskop, just below summit, 24.55649° S, 30.86662° E, 1830 m, Afromontane fynbos/ forest border, in leaf-litter beneath Clivia plants, D. Herbert, L. Davis & M. Cole, stn 14-25, 4 Dec. 2014 ( NMSA P0255).

Type locality

SOUTH AFRICA: Mpumalanga, Mariepskop Forest Reserve, 24.59563° S, 30.82600° E, 790 m.

Identification

Characterised by a combination of shell and anatomical characters, notably the glossy, globose, uniformly yellowish-brown shell, smooth protoconch and non-rimate columella lip; distal genitalia with an atrial diverticulum, a gametolytic duct of moderate length, and a curved epiphallic caecum situated much closer to penial retractor than to insertion of vas deferens.

Description

SHELL ( Fig. 9 ). Globose-lenticular to subglobose; diameter generally less than 13.0 mm, but specimens from high altitude fynbos habitat reaching 18.0 mm; H:D 0.68–0.75; periphery close to mid-whorl, evenly rounded; suture shallowly but distinctly indented, inserting above periphery; very thin and delicate. Protoconch diameter 1.7–1.8 mm, junction with teleoconch indistinct; sculpture virtually smooth, with only traces of the finest microscopic scratch-like spiral lines. Teleoconch of up to 2.25 whorls; whorls expanding moderately rapidly; spiral sculpture virtually obsolete, some extremely fine traces of closeset, wavy, spiral lines, even weaker on base; teleoconch otherwise only with weak, uneven growth-lines, strongest below suture. Umbilicus absent, edge of columella lip whitish, reflected and somewhat raised, spiralling into axis of coiling rather than fusing with parietal region; aperture sub-circular. Translucent, more or less uniformly yellowish-brown to pale olive-brown, some specimens with slightly darker olive-brown axial bands in the last half-whorl; apical and basal surfaces both glossy.

EXTERNAL FEATURES ( Fig. 10 ). Head and neck brownish to grey dorsally, not conspicuously spotted (cf. S. wolkbergensis sp. nov.), paler ventrally; tentacles darker grey with conspicuous dark retractor muscles passing down neck; posterior of foot and caudal appendage more uniformly darker grey dorsally, paler ventrally; some specimens with minute orange-brown pigment granules scattered throughout the skin, but particularly in the dorsal neck region; pulmonary region strongly pigmented. Body lobes of mantle edge grey; right and left shell lobes elongate-trigonal in preserved material. Mantle edge bordered with an irregular cream band, behind which the pulmonary lining is boldly and variably marked with irregular black and cream spots, blotches and bands, often more black than cream; black band overlying primary ureter, less conspicuous and often more irregular than in S. wolkbergensis sp. nov., and sometimes without a well-defined line of cream pigment to its right. Spire viscera dark grey-black with irregularly branching and anastomosing aggregations of cream pigmentation. A single living individual collected in the montane fynbos on top of Mariepskop was of a strikingly different coloration ( Fig. 10 C–D), the head-foot and optic tentacles being predominantly pale brick-red, and the pulmonary lining and viscera rather less densely pigmented.

RADULA ( Fig. 11 ). Formula R+12+(1–2)+(50–60); rachidian tricuspid, laterals essentially bicuspid with a mesocone and strong basal ectocone, but also with a minute endocone on side of mesocone; laterals followed by 1–2 intermediary teeth and then a long series of marginals; marginals curved and terminally bicuspid, tips of cusps bluntly rounded; outer marginals often with a third cusp on concave outer edge.

DISTAL GENITALIA ( Fig. 12 ). Penis rather slender, cylindrical but narrowing slightly toward apex, enclosed in a thin sheath, mid-region may be bent or coiled inside sheath in contracted state; retractor muscle attached to penis apex. Lumen of basal portion of penis with longitudinal folds, two of which are somewhat larger; folds more slender in apical portion; no evidence of a penial verge. Epiphallus short, relatively narrow near its junction with penis, but broader toward insertion of vas deferens; a well-developed, rather bulbous caecum arising one quarter to one third its length from penis. Flagellum divided into a short basal portion with transverse internal diverticulae (F1), and a longer, more slender, loosely coiled, apical portion with a simple tube-like internal core (F2). Junction of epiphallus and flagellum, at insertion of vas deferens, with opaque white contents; vas deferens simple and slender, tracking course of penis and vagina in life. Genital atrium simple, but with a large, elongate, thick-walled diverticulum arising adjacent to vagina and extending diagonally backward beneath penis and oesophagus to opposite side of body cavity; diverticulum connected to pedal floor by fine muscle fibres; lumen of diverticulum with two longitudinal ridges, between which are numerous fine, close-set transverse folds; ridges themselves also pleated with close-set, wavy, transverse folds. Vagina short; gametolytic sac elongate-reniform to obovate, thin-walled; its duct of similar length; base of free oviduct somewhat swollen, off-white; spermoviduct divided into distinct prostatic and oviductal portions. Spermatophore elbowed ( Fig. 12D ), with a large sinuous capsule and slender tail; early part of tail with several branched spines, the last of which is largest; tips of branches bifid; later part very thin, smooth and variously coiled.

Distribution ( Fig. 8 )

A narrow-range endemic, known only from the edge of the Drakensberg Escarpment in northern Mpumalanga, South Africa; at altitudes between 790 and 1920 m above sea level.

Habitat

Northern mist-belt forest ( Mucina & Rutherford 2006); in leaf-litter, but more commonly among epiphytic plants growing on trees.

Remarks

Most of the available material was collected in forest habitat and such specimens are to be considered typical. Additional specimens of a larger size (diameter up to 18 mm) ( Fig. 9F ) and with markedly different, orange-red, body pigmentation ( Fig. 10 C–D) have been collected in the Afromontane fynbos vegetation of the summit region of Mariepskop. However, although seemingly distinct on the basis of size and body colour, these specimens are otherwise indistinguishable from the forest form and have the same unusual, large atrial diverticulum. Pending evidence to the contrary, I consider these specimens to be an ecomorph of S. monsmaripi sp. nov. associated with the colder summit habitat of Mariepskop. Nevertheless, I have included in the type material only specimens from forest habitat.

Sheldonia monsmaripi sp. nov. is perhaps related to S. wolkbergensis sp. nov. from the neighbouring Wolkberg massif. The superficial features of the living animals are extremely similar and both possess an atrial diverticulum, an unusual feature in southern African Sheldonia species. There are, however, consistent differences in the form of the columella lip (non-rimate in S. monsmaripi sp. nov. and rimate in S. wolkbergensis sp. nov.); in the length of the gametolytic duct (very short in S. wolkbergensis sp. nov.); in the position of the epiphallic caecum relative to the penial retractor and the insertion of the vas deferens (close to penial retractor in S. monsmaripi sp. nov. and closer to vas deferens in S. wolkbergensis sp. nov.) and in the position of the atrial diverticulum (beneath oesophagus in S. monsmaripi sp. nov. and beneath buccal mass in S. wolkbergensis sp. nov.). In addition, S. wolkbergensis sp. nov. is smaller than S. monsmaripi sp. nov. and possesses a penial verge.

The non-rimate columella lip of S. monsmaripi sp. nov. is similar to that seen in some species of Sheldonia s.s., as well as ‘ Sheldonia ’ leucospira (Pfeiffer, 1847) and two additional undescribed species of Sheldonia s.l. from E Cape (Herbert unpubl. obs.), but none of these species possesses an atrial diverticulum. The presence of an atrial diverticulum has not previously been observed in shelled urocyclids from southern African. Van Mol (1970) reported such a structure in several Central and West African urocyclid genera, noting that its occurrence was sporadic and not fixed within members of the same genus. It may be present in one species, but absent in another, seemingly closely related species. The phylogenetic significance of its presence in both S. monsmaripi sp. nov. and S. wolkbergensis sp. nov. is thus difficult to evaluate, the more so since the internal structure of the organ differs in the two species. Given that they also differ with respect to several other features of distal reproductive tract morphology, the possession of an atrial diverticulum may be convergent.

Figures

Fig. 8. Map showing the distribution of new urocyclid species in relation to centres of plant endemism (Van Wyk & Smith 2001). Green circles = Ptilototheca soutpansbergensis gen. et sp. nov.; blue triangles = Sheldonia wolkbergensis sp. nov.; maroon squares = Sheldonia monsmaripi sp. nov.; pale blue = Soutpansberg Centre; pale orange = Wolkberg Centre (Serala Subcentre); pale green = Wolkberg Centre (Blyde Subcentre). Contours at 1000 and 2000 m.

Fig. 9. Sheldonia monsmaripi sp. nov. A–D. Holotype, diameter 12.2 mm (NMSA W4413/T3300). E. Paratype, diameter 12.0 mm (NMSA W3900/T3172). F. Large specimen from fynbos on Mariepskop summit, diameter 16.4 mm (NMSA P0278).

Fig. 10. Sheldonia monsmaripi sp. nov., living animals. A–B. Mariepskop Forest Reserve, mist-belt forest, shell diameter 11.6 mm (paratype, NMSA P0276/T4073). C–D. Mariepskop Forest Reserve, summit fynbos, shell diameter 16.3 mm (NMSA P0278).

Fig. 11. Sheldonia monsmaripi sp. nov., radula, holotype (NMSA W4413/T3300). A. Rachidian and lateral teeth. B. Rachidian and innermost lateral teeth. C. Inner left marginal teeth. D. Outer left marginal teeth. Scale bars: A = 100 µm; B–D = 50 µm.

Fig. 12. Sheldonia monsmaripi sp. nov., genitalia, paratype (NMSA W3653/T3169). A. Entire genital system. B. Flagellum and distal epiphallus. C. Internal structure of genital atrium and atrial diverticulum. D. Spermatophore.