Chondrocyclus langebergensis Cole 2019, sp. nov.

Chondrocyclus langebergensis sp. nov.

urn:lsid:zoobank.org:act: 9C3B5371-50CA-43DD-A684-1796648C24BA

Figs 5, 10O, R, 25

Chondrocyclus convexiusculus – Connolly 1939: 537. — Herbert & Kilburn 2004: 91.

Diagnosis

Shell small, very depressed, discoidal; periostracum with axial costae producing spiral rows of simple, robust hairs concentrated at and on either side of periphery; operculum duplex, exterior portion very shallowly concave, with thickened ridge on multispiral lamella from which emanates a fairly long solid fringe and a very short fringe below this; radula with three large cusps on second lateral tooth.

Etymology

Named after the Langeberg mountain range, part of the Cape Fold Mountains.

Type material examined

Holotype

SOUTH AFRICA – Western Cape • Langeberge foothills, Pat Busch Nature Reserve, Karin Trail, riverine fynbos; 33.7551° S, 19.9947° E; 450 m a.s.l.; 7 Aug. 2014; M. Cole leg.; in leaf-litter beneath bushes; NMSA P 0642/ T 4159. (Fig. 10 O, R)

Paratypes

SOUTH AFRICA – Western Cape • 21 specimens; same collection data as for holotype; ELM D17981/ T 98 • 1 specimen; same collection data as for holotype; ELM W 3899 / T 99 • 14 specimens; same collection data as for holotype; 10 Oct. 2007; D. Herbert and L. Davis leg.; NMSA W 5768 / T 4120 • 117 specimens; same collection data as for holotype; 3 Mar. 2012; R. Daniels leg.; ELM D16920/ T 97 • 40 specimens; Langeberg Mountains, Heidelberg area, Grootvadersbosch Nat. Res., Bushbuck Trail, Afrotemperate forest; 33.9819° S, 20.8321° E; 19 Apr. 2012; M. Cole leg.; in leaf litter; ELM D16999/ T 90 • 6 specimens; same collection data as for preceding; ELM W 3660 / T 91 • 1 specimen; same collection data as for preceding; NHMUK 20120284 • 113 specimens; same collection data as for preceding; 3 Mar. 2012; R. Daniels leg.; ELM D16918/ T 100 • 7 specimens; same collection data as for preceding; ELM W 03613/ T 92 • 5 specimens; same collection data as for preceding; NHMUK 20120283 • 5 specimens; same collection data as for preceding; NMW. Z.2012.065.00011 • 5 specimens; same collection data as for preceding; RMNH MOL.330500 • 5 specimens; Grootvadersbosch Nat. Res. Melkhoutpad; 33.9819° S, 20.8321° E; 16 Sep. 2009; M. Cole leg.; ELM D16917/ T 93 • 1 specimen; same collection data as for preceding; W 3689/ T 94 • 6 specimens; Grootvadersbosch Nat. Res., Redwoods area, Podocarpus forest; 33.9826° S, 20.8296° E; 224 m a.s.l.; 14 Sep. 2003; J. Londt leg.; NMSA W 1043 / T 4117 • 20 specimens; Grootvadersbosch Nat. Res.; 33.9959° S, 20.8129° E; 22 Feb. 2005; A. Moussalli and D. Stuart-Fox leg.; NMSA W 5008 / T 4119 • 176 specimens; Marloth Nature Reserve, Swellendam, Duivelsbos Forest, 33.9934° S, 20.4587° E; 15 Sep. 2009; M. Cole leg.; ELM D16919/ T 95 • 31 specimens; same collection data as for preceding; W 03614/ T 96 • 4 specimens; Marloth Nat. Res., afrotemperate forest; 33.9897° S, 20.4544° E; 23 Feb. 2005; A. Moussalli and D. Stuart-Fox leg.; in leaf-litter; NMSA W 5016 / T 4118 • 6 specimens; Montagu; 33.7833° S, 20.1167° E; M. Connolly leg.; NMSA 2778 / T 4116.

Description

SHELL (Fig. 25 A–C). Small, very depressed, discoidal, adult diameter 3.63–5.76 mm, height 1.42– 2.76 mm, diameter:height 1.79–2.85 (n = 67, measured in four different populations; Table 3). Spire almost flat (Fig. 25A), sometimes concave, usually with only the mammillate, tilted protoconch projecting. Embryonic shell (Fig. 25D) approx. 2–2.25 whorls, microscopically malleate, junction between embryonic shell and teleoconch evident with development of widely spaced axial costae on teleoconch.Teleoconch comprising2.25 whorls, very rapidly increasing, convex, suture deeply impressed. Aperture circular, last whorl descending steeply nearing aperture, peristome simple, continuous and free. Umbilicus very wide, exposing all the whorls (Fig. 25C). Periostracum glossy and lacquer-like with lamellate axial costae at regular intervals, 47–63 (n = 14) on last whorl in Grootvadersbosch population but varies between populations (Table 3), which produce six spiral rows of simple, very long and robust hairs around the periphery; intervals between costae with six–eight microscopic axial threads. Shell translucent reddish brown, honey brown or yellowish-white when fresh. Living animal. Variable in colour between populations from creamy white with light brown pigmentation on tentacles to almost black, underside of foot creamy white.

OPERCULUM (Fig. 25F, I). Duplex and shallowly concave; multispiral lamella of outer portion with five low whorls, thickened horizontal ridge near base of lamellar blade runs parallel to disc surface, a long fringe of fused bristles and a second very short fringe below it emanate from this ridge; main fringe grows upwards (i.e., parallel to lamellar blade) and then downwards, leaving a deep, wide groove between fringe and blade of lamella; lamellar blade projects above level of fringe and is very thin; fringe of each whorl fused to lamellar blade of next whorl; fringe of outermost whorl overlaps disc slightly and is reflexed over peristome in life although operculum is retractile.

RADULA (Fig. 25E). Rachidian with five cusps, middle one longer than 2 cusps on either side of it; first and second lateral teeth with five cusps (5 th sometimes vestigial), the third cusp from centre the largest.

PENIS (Fig. 25 G–H). Shaft more or less cylindrical and slightly flattened dorsoventrally, distal half slightly expanded on left side, numerous annular rugae, distal end smooth but not bulbous, intromittent organ short.

Distribution and habitat

Western Cape, evidently endemic to Langeberg mountain range in Cape Fold Mountain belt, southfacing slopes and on northern side of range in Montagu area (Fig. 5).

Diverse vegetation types: patches of Western Cape Afrotemperate Forest (von Maltitz et al. 2003) and riverine fynbos, in leaf litter.

Remarks

In terms of its hairy periostracum Chondrocyclus langebergensis sp. nov. resembles Afrocyclus isipingoensis gen. et comb. nov., but the molecular analyses placed C. langebergensis sp. nov. and C. kevincolei sp. nov. in a well-supported monophyletic clade, termed the Overberg clade, within the Chondrocyclus s.s. radiation (Cole et al. 2019; Fig. 1). The major morphological feature distinguishing this clade from A. isipingoensis gen. et comb. nov. is that the second lateral tooth of the radula has three large cusps (Fig. 25E) as opposed to two in A. isipinoensis comb. nov. (Fig. 27E). Differences between C. langebergensis sp. nov. and C. kevincolei sp. nov. are discussed under the latter species.

The Overberg clade and the other taxon in the southwestern Cape, C. convexiusculus, have not been recorded sympatrically although they occur in close proximity inland in the upper Breede River valley and near the coast (Fig. 5). Other taxa also contain distinct clades in either the Hottentots-Holland Mountains or the Overberg which do not occur in the other region (e.g., Gouws et al. 2010; Herbert & Moussalli 2010; McDonald et al. 2012; Daniels et al. 2013) and the Breede River valley is considered an important barrier to gene flow (Weimarck 1941; Linder 2003; McDonald & Daniels 2012).