Chondrocyclus pulcherrimus sp. nov.

urn:lsid:zoobank.org:act: F19B8F07-075C-4A7F-BD19-BB875003E7D0

Figs 10 J–K, 16A, 19

Diagnosis

Shell very small, very depressed, discoidal; periostracum with very dense axial costae developing at the periphery a row of quadrangularly-shaped flanges and several spiral rows of semicircular flanges above and below this; operculum duplex, exterior saucer-shaped portion with step-shaped multispiral lamella terminating in a long solid fringe reflexed over peristome; radula with three large cusps on second lateral tooth, cusps on rachidian uniform in size; penis flattened dorsoventrally and laterally expanded on left side from about midway down the shaft.

Etymology

The specific name is derived from the Latin ‘ pulcherrimus ’, meaning ‘most beautiful’, with reference to the ornate periostracum with very dense axial lamellae and a larger number of spiral rows of flanges than any other species.

Type material examined

Holotype

SOUTH AFRICA – KwaZulu-Natal • Ngome Forest, west of Nongoma, Southern Mistbelt forest; 27.8245° S, 31.4191° E; 1136 m a.s.l.; 19 Jan. 2010; M. and K. Cole leg.; in leaf litter; NMSA W 9272 / T 3075. (Fig. 10 J–K)

Paratypes

SOUTH AFRICA – KwaZulu-Natal • 66 specimens; same collection data as for holotype; ELM D16939/ T 118 • 1 specimen; same collection data as for holotype; ELM W 3626 / T 119 • 5 specimens; same collection data as for holotype; NHMUK 20120281 • 3 specimens in ethanol; same collection data as for holotype; NMW. Z.2019.004.00009 • 2 dry specimens; same collection data as for holotype; NMW. Z.2019.004.00008 • 4 specimens; same collection data as for holotype; RMNH MOL.330504 • 11 specimens; Ngome Forest, mist-belt Podocarpus forest; 27.8250° S, 31.4183° E; 1200 m a.s.l.; 2 Dec. 1998; Herbert, Seddon and Tattersfield leg.; in leaf-litter beneath T richocladus grandilflorus; NMSA V 7103 / T 4112 • 24 specimens; Ngome Forest, mist-belt Podocarpus forest; 27.8250° S, 31.4833° E; 1100 m a.s.l.; 2 Dec. 1998; Herbert, Seddon and Tattersfield leg.; in leaf-litter; NMSA V 8530 / T 4113 .

Description

SHELL (Fig. 19 A–C). Small, very depressed, discoidal, adult diameter 3.50–4.85 mm, height 1.38– 2.56 mm, diameter:height 1.87–2.54(n = 22). Spire almost flat with sometimes only protoconch projecting (Fig. 19A), suture deeply impressed. Embryonic shell (Fig. 19D) just over two whorls, sculptured with pock marks, junction between embryonic shell and teleoconch not particularly distinct, with weak costae at first, becoming stronger. Teleoconch comprising two whorls, rapidly increasing, suture deeply impressed. Aperture circular, last whorl descending near aperture, peristome simple, continuous and free. Umbilicus very wide, exposing all the whorls (Fig. 19C). Periostracum glossy, light yellowishbrown and lacquer-like, with very dense lamellate axial costae at regular intervals, approx. 300 on last whorl (300 and 340 in Fig. 19B and A, respectively), developing at the periphery quarangularly-shaped flanges, their expanded distal ends fused to form a solid fringe (Fig. 19E); above periphery are four–five spiral rows of flanges and six–seven rows below it spiraling into umbilicus, height of flanges forming spiral rows varies; row of flanges below suture forms a channel (see Fig. 19B,D); intervals between costae smooth. Shell pale, corneous and translucent when fresh.

OPERCULUM (Fig. 19 G–I). Duplex, outer portion consists of multispiral lamella with about 4.5 whorls, each step-shaped; at the growing edge the top of lamellar blade slopes down at an angle then curves under the step formed by the previous whorl and is thinner and more or less perpendicular where it is attached to the disc; very long fringe of fused bristles emanates from near base of vertical portion of step and curves upwards and then outwards forming a deep furrow between fringe and lamellar blade, spanned by a few bristles; a very short solid horizontal fringe emanates just below main fringe; top edge of lamella projects above level of fringe; fringe of each whorl fused to lamella of following whorl; outermost lamellar fringe very long and reflexed over peristome.

RADULA (Fig. 19F). Rachidian with five cusps of approx. equivalent length; first lateral tooth with three cusps of approx. equivalent length and a very small fourth; second lateral tooth with three cusps of approx. equivalent length and two vestigial outer cusps; teeth do not differ much in size.

PENIS (Fig. 19 J–K). flattened dorsoventrally and laterally expanded on left side from about midway down the shaft, with numerous annular rugae, smooth distal end occupies about one quarter of shaft.

Distribution and habitat

Known only from Ngome Forest, KwaZulu-Natal. Indigenous Eastern Mistbelt Forest (von Maltitz et al. 2003) with large trees, south-facing; in leaf-litter (Fig. 16A).

Remarks

The very dense costae of the periostracum of C. pulcherrimus sp. nov. and large number of spiral rows of flanges, as well as the flat spire, immediately distinguish this species from all other species of Chondrocyclus .

Chondrocyclus pulcherrimus sp. nov. resembles C. trifimbriatus in features of the operculum, radula, penis and the rough texture of the protoconch. The operculum is similar to that of C. trifimbriatus, but the fringe emanates from near the bottom of the vertical portion of the stepped lamellar blade forming a deep groove while in C. trifimbriatus it emanates from near the top of the blade and there is a very shallow groove between the fringe and lamella.

The Ngome Forest is 3360 ha and much of the forest is protected in the Ntendeka Wilderness Area. Chondrocyclus pulcherrimus sp. nov. is locally very common unlike C. trifimbriatus which appears to be rare in all populations sampled.