Chondrocyclus putealis Connolly 1939

Chondrocyclus putealis Connolly, 1939

Figs 16B, 22–23

Chondrocyclus putealis Connolly, 1939: 538, pl. xvi, figs 25–27 (type loc.: Southport [Puzey]).

Chondrocyclus putealis – Herbert & Kilburn 2004: 91.

Diagnosis

Shell small, depressed, lenticular; periostracum with dense axial costae expanded into three spiral rows of flanges on last whorl. at periphery around umbilicus and below suture; operculum duplex, multispiral lamella of exterior portion deeply concave, with horizontal shelf of interwoven bristles spiralling up on inside of lamella and connected to a very long, loose fringe reflexed over peristome; radula with three large cusps on second lateral tooth; penis flattened dorsoventrally with lateral expansions of shaft towards distal end, more prominent on left side.

Etymology

The specific name is derived from the Latin ‘ putealis ’, meaning ‘of or relating to a well’, with reference to the deep well-like operculum.

Type material examined

Syntypes

SOUTH AFRICA – KwaZulu-Natal • 4 specimens; Natal, Southport; NHMUK 1937.12.30.5087– 1937.12.30.5090. (Fig. 22 A)

Other material examined

SOUTH AFRICA – KwaZulu-Natal • 12 specimens; Port Shepstone area, Marble Delta; 30.6509° S, 30.3560° E; 10 May 2001; D. Herbert leg.; NMSA V 9390. – Eastern Cape • 46 specimens; Mkambati Nature Reserve, Mtentu River gorge, south bank, 4.25 km usptream of mouth; 31.2316° S, 30.0100° E; 31 m a.s.l.; 12 Jan. 2012; M. Cole leg.; ELM D16954 • 17 specimens; same collection data as for preceding; ELM W 03656 • 3 specimens in ethanol; same collection data as for preceding; NHMUK 20120272 • 3 specimens in ethanol; same collection data as for preceding; NMW. Z.2012.065.00004 • 3 specimens in ethanol; same collection data as for preceding; RMNH. MOL 330498 • 3 specimens; Mtentu, north bank, 3.25 km upstream of mouth, scarp forest on steep slope with large rocks; 31.231000° S, 30.0174° E; 12 Jan. 2012; M. Cole leg.; ELM D16955 • 5 specimens; same collection data as for preceding; ELM W 03657.

Description

SHELL (Fig. 22 A–D). Small, depressed, lenticular, adult diameter 4.91–5.38 mm, height 2.49–3.26 mm, diameter:height 1.61–2.00 (n = 20). Spire not much raised, apex almost flat (Fig. 22A, C). Embryonic shell (Fig. 23A) approx. 1.75 whorls, microscopically malleate, roughest in centre, junction between embryonic shell and teleoconch evident with appearance of a few weak axial costae, but not sharply demarcated. Teleoconch comprising 2.5–2.75 whorls, moderately convex, rapidly increasing, suture deeply impressed. Aperture circular, last whorl descending strongly near aperture, peristome simple, continuous and free. Umbilicus wid and deep, exposing all the whorls (Fig. 22D). Periostracum glossy, honey-brown and lacquer-like with dense lamellate costae at regular intervals, 107–150 (n = 15) on last whorl, expanded into paddle-shaped flanges at periphery and umbilicus, as well as a row of shorter broadly rounded lamellae below suture (Fig. 22 B–D); flanges bear axial riblets visible at very high magnification (Fig. 23B); intervals between costae with microscopic axial threads.

OPERCULUM (Fig. 23 D–E, G–H). Duplex, outer multispiral portion with approx. five whorls; lamellar blade high and steep sided, resulting in a deeply concave outer portion with more-or-less perpendicular sides towards the top and curving inwards towards the bottom; upper edge of lamellar blade thickened, forming a horizontal shelf of interwoven bristles which forms a spiral staircase on the inside of the lamellar blade; in the outermost whorl the latter is connected to a very long fringe reflexed over peristome and preventing operculum being withdrawn into shell. In earlier whorls this fringe is not visible and appears fused with the lamella; surface of lamella of last whorl tuberculate at high magnification (Fig. 23H). Shell translucent, glossy, honey-brown when fresh.

RADULA (Fig. 23C). Rachidian with five cusps, central one approx. twice length of outer two on each side, the latter four approx. equivalent length; first and second lateral teeth each with three large cusps, a smaller fourth and a vestigial fifth, second lateral tooth is larger.

PENIS (Fig. 23F, I). Shaft dorsoventrally flattened, with lateral expansions towards the distal end on both sides but more prominent on left, with numerous annular rugae, distal end bulbous and smooth.

Distribution and habitat

Endemic to a narrow range primarily near the coast in southern KwaZulu-Natal and Pondoland (the northeastern region of the Eastern Cape province), between Mtentu in northern Transkei and Southport in southern Kwazulu-Natal, but also recorded inland in the Port Shepstone area (ca 200 m a.s.l.) (Fig. 16B).

Indigenous Scarp Forest (Mucina & Geldenhuys 2006) on banks of rivers, in leaf litter.

Remarks

Morphological differences between C. putealis and C. bathrolophodes are slight. The shell of C. putealis resembles C. bathrolophodes in shape but attains slightly smaller size. The position of spiral rows of flanges is similar in the two species, but costae are slightly more dense on average in C. putealis and the peripheral and umbilical cords stronger than those of C. bathrolophodes. The opercula of the two species are very similar although the operculum of C. putealis is deeper with perpendicular sides near the top and curving inward near the disc, while the lamellar blade of C. bathrolophodes widens evenly towards the top. Both species occupy a relatively narrow range, separated geographically by a wide intervening distance in which C. cooperae sp. nov. (below) and C. pondoensis sp. nov. occur. On morphological grounds alone, it was not clear whether C. putealis and C. bathrolophodes should indeed be considered distinct species, in spite of subtle differences. In the molecular analyses C. pondoensis sp. nov. is nested within this group (Fig. 1), adding weight to the evidence to treat these lineages as distinct species.

Chondrocyclus putealis appears to be a very rare species and there are only a few localities where recent specimens could be found and it was patchily distributed at these localities. Chondrocyclus putealis is replaced by the closely related C. cooperae sp. nov. westwards along the coast, while C. pondoensis sp. nov. also extends westwards from Pondoland and is sympatric with both these species. This region of the north-eastern coast of the Eastern Cape is an important centre of cladogenic events in rhytidid molluscs (Moussalli et al. 2009; Herbert & Moussalli 2010) and is a focus of endemism in sylvian mollusc taxa (Bursey & Herbert 2004; Herbert & Kilburn 2004; Cole & Herbert 2009; Herbert 2017). Botanically, this area harbours a large number of palaeoendemics and neoendemics concentrated in scarp forests in deep gorges (van Wyk & Smith 2001; Mucina et al. 2007).