Chondrocyclus convexiusculus ( Pfeiffer, 1855 )

Cole, Mary L., 2019, Revision of Chondrocyclus s. l. (Mollusca: Cyclophoridae), with description of a new genus and twelve new species, European Journal of Taxonomy 569, pp. 1-92: 9-12

publication ID

https://doi.org/10.5852/ejt.2019.569

publication LSID

lsid:zoobank.org:pub:79BE13FC-B840-4C39-8D25-3328BDCC44D2

persistent identifier

http://treatment.plazi.org/id/101687E3-D558-FFC3-FDF9-A837FECED008

treatment provided by

Plazi

scientific name

Chondrocyclus convexiusculus ( Pfeiffer, 1855 )
status

 

Chondrocyclus convexiusculus ( Pfeiffer, 1855) 

Figs 4View Fig, 5View Fig, 8CView Fig

Cyclostoma (Cyclophorus) convexiusculum Pfeiffer, 1855: 104  (type loc.: Simonstown [Macgillivray]). Cyclophorus convexiusculus var. minor Benson, 1856: 438  (type loc.: Table Mountain [Layard]).

Chondrocyclus convexiusculus – Kobelt 1902: 230  . — Connolly 1939: 536. — Herbert & Kilburn 2004: 92.

Diagnosis

Shell small, depressed, lenticular; protoconch mammillate and tilted; periostracum with axial costae developing at the periphery broad triangular flanges each terminating in a long, hair-like spine; operculum flattened, exterior portion shallowly concave, with step-shaped multispiral lamella terminating in a long solid fringe; radula with three large cusps on second lateral tooth.

Etymology

The specific name is derived from the Latin ‘ convex ’, meaning ‘arched or vaulted’.

Type material examined

Syntypes

SOUTH AFRICA – Western Cape • 3 specimens; syntypes of Cyclostoma (Cyclophorus) convexiusculum Pfeiffer, 1855  ( Fig. 4AView Fig); Simons Bay ; [Mrs] Cuming leg.; NHMUK 20120231View Materials  .

Other material examined

SOUTH AFRICA – Western Cape • 6 specimens; Cape Peninsula, Simonstown ; 34.1912° S, 18.4211°E; M. Connolly coll.; NMSA 2777View MaterialsGoogleMaps  2 specimens; same collection data as for preceding; ex. M. Connolly coll.; NMSA A8004View MaterialsGoogleMaps  11 specimens; Cape Town, 2.8 km south of Miller’s Point, forest in a depression with a few invasive trees ( Eucalyptus  and Port Jackson ), steep slope with rocks and root buttresses; 34.2507° S, 18.4729° E; 25 Jun. 2011; R. Daniels leg.; thick and moist leaf litter, about a week of rain before collection; ELM D16879View MaterialsGoogleMaps  11 specimens; same collection data as for preceding; ELM W3636View MaterialsGoogleMaps  1 specimen in ethanol; same collection data as for preceding; NHMUK 20120276View MaterialsGoogleMaps  40 specimens; same collection data as for preceding; 1 Feb. 2012; R. Daniels leg.; ELM D16880View MaterialsGoogleMaps  17 specimens; same collection data as for preceding; ELM W3637View MaterialsGoogleMaps  3 specimens; same collection data as for preceding; NHMUK 20120277View MaterialsGoogleMaps  2 specimens; same collection data as for preceding; NMW.Z.2012.065.00007GoogleMaps  5 specimens; DuToits Kloof, Donkerkloof, patch of Southern Afrotemperate forest in steep ravine; 33.7536° S, 19.0696° E; 462 m a.s.l.; 7 Aug. 2014; M. Cole leg.; ELM D17970View MaterialsGoogleMaps  1 specimen; same collection data as for preceding; ELM W3891View MaterialsGoogleMaps  26 specimens; Kogelberg Nature Reserve, small patch of Southern Afrotemperate forest near Leopards Gorge waterfall; 34.3409° S, 18.9407°E; 312 m a.s.l.; 12 Aug. 2014; M. Cole leg.; ELM D17955View MaterialsGoogleMaps  22 specimens; same collection data as for preceding; ELM W03876View MaterialsGoogleMaps  22 specimens; Kogelberg Nature Reserve, Oudebosch, patch of Southern Afrotemperate forest in kloof with Oudebos River ; 34.3337° S, 18.9487°E; 260 m a.s.l.; 12 Aug. 2014; M. Cole leg.; ELM D17975View MaterialsGoogleMaps  25 specimens; same collection data as for preceding; ELM W03877View MaterialsGoogleMaps  .

Description

SHELL ( Fig. 4View Fig B–D). Small, depressed, lenticular, adult diameter 3.97–5.18 mm, height 2.29–3.20 mm, diameter:height 1.59–1.88 (n = 21). Spire little exserted, apex mammillate and tilted ( Fig. 4A, CView Fig). Embryonic shell ( Fig. 4EView Fig) approx. 2.25 whorls, microscopically malleate, sculpture strongest on earliest part, junction between embryonic shell and teleoconch evident with development of axial costae and threads on teleoconch. Teleoconch comprising 2.25 whorls, convex, rapidly increasing, suture deeply impressed. Aperture circular, last whorl descending near aperture, peristome simple, continuous and free. Umbilicus wide and deep, exposing all the whorls. Periostracum glossy, honey-brown and lacquerlike with lamellate axial costae at regular intervals, 44–61 (n = 16) on last whorl, developing at periphery broad triangular flanges terminating in a long, hair-like spine ( Figs 4FView Fig, 8CView Fig); intervals between costae with 3–5 indistinct microscopic axial threads. Shell translucent glossy honey-brown or creamy-white when fresh.

LIVING ANIMAL. Head, tentacles and snout dark grey; underside of foot white.

OPERCULUM ( Fig. 4View Fig H–I). Duplex, outer portion concave, consists of multispiral lamella with almost five whorls, each step-shaped; the growing edge of the lamellar blade angular and is more or less perpendicular to disc where it is attached; long fringe of fused bristles emanates from outer side of lamellar blade and curves upwards and outwards forming a furrow between fringe and lamellar blade partially covered by top edge of lamellar blade which curves outwards; top edge of lamella projects above fringe; fringe of each whorl fused to lamella of following whorl.

RADULA ( Fig. 4GView Fig). Rachidian with five cusps, central cusp approx. twice as long as two on either side of it; first and second lateral tooth each with four cusps and a swelling representing the fifth cusp, first three cusps (from centre) increasing in size and fourth considerably smaller.

PENIS ( Fig. 4View Fig J–K). Shaft more-or-less cyclindrical with slightly swollen distal end and a short intromittent organ.

Distribution and habitat

Western Cape, mountains of the Cape Peninsula and north-south running mountains to the east of the Cape Flats. Inland populations appear to be bounded by the upper Breede River valley and coastal populations by the relatively low-lying Agulhas Plain ( Fig. 5View Fig). There are no records from the Riviersonderend Mountains.

Western Cape Afrotemperate forest ( von Maltitz et al. 2003), very small patches in sheltered ravines; in leaf-litter.

Remarks

Connolly (1929) distinguished this species from C. alabastris  on the basis of the second lateral tooth of the radula, that of C. convexiusculus  having three large cusps and C. alabastris  two. This is confirmed by comparing Fig. 4GView Fig and Fig. 7FView Fig. There are also differences in the periostracum and operculum discussed under C. alabastris  . The molecular analyses placed C. convexiusculus  and C. alabastris  in different clades ( Fig. 1View Fig).

NMSA

KwaZulu-Natal Museum

ELM

East London Museum

NMW

Naturhistorisches Museum, Wien

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Architaenioglossa

Family

Cyclophoridae

Genus

Chondrocyclus

Loc

Chondrocyclus convexiusculus ( Pfeiffer, 1855 )

Cole, Mary L. 2019
2019
Loc

Cyclostoma (Cyclophorus) convexiusculum

Benson W. H. 1856: 438
Pfeiffer L. 1855: 104
Loc

Chondrocyclus convexiusculus –

Herbert D. & Kilburn D. 2004: 92
Connolly M. 1939: 536
Kobelt W. 1902: 230