Chondrocyclus kevincolei Cole 2019, sp. nov.
Creators: name: Cole, Mary L.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Architaenioglossa
Cyclophoridae
Chondrocyclus
Chondrocyclus kevincolei

description: Chondrocyclus kevincolei sp. nov.
urn:lsid:zoobank.org:act: 2C3567A2-1004-4E9B-9452-C6E657323E18
Figs 5, 10 P–Q, 26
Chondrocyclus convexiusculus – Connolly 1939: 537.
Diagnosis
Shell small, depressed, lenticular; periostracum with axial costae producing spiral rows of simple hairs; spiral grooves on shell corresponding with rows of hairs; operculum duplex, exterior portion very shallowly concave, with step-shaped multispiral lamella terminating in a short fringe with uneven edge, diameter of exterior portion less than diameter of inner disc; radula with three large cusps on second lateral tooth.
Etymology
Named for the author’s husband, Kevin Cole, in acknowledgement of his indispensable assistance on fieldtrips.
Type material examined
Holotype SOUTH AFRICA – Western Cape • Platbos Forest near Gansbaai, Western Cape Milkwood Forest with large trees including Sideroxylon inerme Linne and Celtis africana N.L.Burm; 34.5671°S, 19.4495°E; 13 Aug. 2014; M. and K. Cole leg.; in leaf litter; NMSA W9270/T3073. (Fig. 10 P–Q)
Paratypes SOUTH AFRICA – Western Cape • 1 specimen; same collection data as for holotype; ELM D18004 / T85 • 2 specimens; same collection data as for holotype; ELM W3898 /T86 • 327 specimens; same collection data as for preceding; 9 Sep. 2009; M. Cole, K. Cole, D-J Hodgkinson and T. Pretorius leg.; ELM D16921 /T81 • 90 specimens; same collection data as for preceding; ELM W3615 /T82 • 20 specimens; same collection data as for preceding; NHMUK 20120282 • 23 specimens; same collection data as for preceding; NMSA P0598 /T4121 • 18 specimens; same collection data as for preceding; NMW.Z.2012.065.00010 • 15 specimens; same collection data as for preceding; RMNH MOL.330503 • 47 specimens; same collection data as for preceding; 18 Apr. 2012; M. Cole, D. Herbert and L. Davis leg.; ELM D16998 /T83 • 5 specimens; same collection data as for preceding; ELM W3659 /T84 • 27 specimens; Bredasdorp, about 5 miles to SW, on Elim Rd; 34.5450°S, 19.9614°E; ex Transvaal Museum; dry bush on hillside; NMSA W575 /T4123 • 34 specimens; Bredasdorp, 7 km south west on R43 to Elim, bushy valley with dam; 34.5912°S, 19.9992°E; 35 m a.s.l.; 13 Aug. 2014; M. Cole leg.; ELM D17983 /T87 • 15 specimens; same collection data as for preceding; ELM W3890 /T88 • 23 specimens; Grootbos Nat. Res., Gansbaai area, Milkwood forest; 34.5421°S, 19.4153°E; 7 Oct. 2007; D. Herbert and L. Davis leg.; in leaf-litter; NMSA W5659 /T4122 • 45 specimens; Grootbos Private Nature Reserve, between Stanford and Gansbaai, Western Cape Milkwood Forest; 34.5419°S, 19.4122° E; 203 m a.s.l; 13 Aug. 2014; M. Cole leg.; D18005/T89 • 6 specimens; Gansbaai dune scrub; 34.5795°S, 19.3442°E; 13 Feb. 2005; A. Moussalli and D. Stuart-Fox leg.; in leaf-litter; NMSA W3537 /T4124.
Description
SHELL (Fig. 26 A–F). Small, depressed, lenticular, adult diameter 3.59–5.34 mm, height 1.59–2.84 mm, diameter:height 1.68–2.37 (n = 87 from 4 populations; variations in dimensions between populations are given in Table 4). Spire little exserted, protoconch large and mammillate (Fig. 26A). Embryonic shell (Fig. 26G) approx. 2.25 whorls, almost smooth but microscopically malleate at tip, junction between embryonic shell and teleoconch evident with development of costae on teleoconch. Teleoconch comprising just over two whorls, very 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 Fig. 26C, F). Periostracum glossy and lacquer-like with lamellate axial costae at regular intervals on last whorl, 51–75 (n = 22) in Platbos population, but vary between populations (Table 4), which produce spiral rows of simple hairs varying in different populations from approx. 4–14 on last whorl, longest at periphery and shortest around umbilicus; intervals between axial costae with approx. eight microscopic axial threads (Fig. 26H); shell bears spiral grooves corresponding with the rows of hairs (Fig. 26 D–F). Shell translucent when fresh; two colour morphs present reddish brown and creamy white.
LIVING ANIMAL. Varies in colour between populations from creamy white with slight pigmentation on tentacles to very dark grey (see below).
OPERCULUM (Fig. 26 J–K). Duplex, shallowly concave; multispiral lamella of outer portion with 4.5 whorls, each step-shaped, growing edge of lamella at angle, perpendicular where it is attached to disc; fringe very short and solid, with a frayed distal edge even in fresh specimens, fringe of each whorl not fused to lamellar blade of following whorl, diameter of outer multispiral portion smaller than diameter of inner disc due to very short fringe; operculum retractile.
RADULA (Fig. 26I). Rachidian with five cusps, middle one longer than two cusps on either side of it; first and second lateral teeth each with four cusps and a vestigial 5 th, the third cusp from centre the largest.
PENIS (Fig. 26L). Shaft more or less cylindrical and slightly flattened dorsoventrally, distal half slightly expanded on left side, numerous annular rugae, distal end smooth, intromittent organ short.
Distribution and habitat
Western Cape, Agulhas Plain, between Gansbaai and Bredasdorp. Various forested or bushy habitats in patches of Western Cape Milkwood Forest (part of Southern Coastal forest group) (von Maltitz et al. 2003) with large trees, characterised by white milkwoods (Sideroxylon inerme), white stinkwoods (Celtis africana) and white pear (Apodytes dimidiata E. Mey. ex Arn.), including the southernmost forests in Africa (Platbos and Grootbos), dune scrub at Gansbaai and ‘dry bush on hillside’ (south-west of Bredasdorp); in leaf-litter (Fig. 5).
Remarks
The distinct spiral grooves on the shell of C. kevincolei sp. nov. (Fig. 26 D–F) are unique among species of Chondrocyclus although there are sometimes faint traces of spiral grooves on shells of A. isipingoensis gen. et comb. nov. and C. langebergensis sp. nov. visible only at very high magnification. Chondrocyclus langebergensis sp. nov. differs from C. kevincolei sp. nov. in its lack of prominent spiral grooves on the shell, the spiral rows of long hairs are concentrated around the periphery, the protoconch is more strongly sculptured and the opercula differ. In C. langebergensis sp. nov., the lamellar fringe of each spiral whorl of the operculum emanates from a ridge at the base of the lamellar blade and is fused to the lamellar blade of the following whorl. The terminal fringe is long and overlaps the base when viewed from above (Fig. 25F). In C. kevincolei sp. nov. the fringe emanates from near the top of the lamellar blade and is very short and appears distinct from the following lamellar whorl; the outer saucershaped portion is smaller than the polished base (Fig. 26J). These differences together with molecular evidence, are considered to warrant recognition of at least two distinct species, one in the Langeberg Mountains and the other on the relatively low-lying coastal region of the Agulhas Plain. The Langeberge and Agulhas Plain are separated by the Breede River valley and by a belt of relatively arid vegetation, consisting mainly of Ruens Shale Renosterveld and Agulhas Limestone Fynbos (Rebelo et al. 2006), which developed in the Pliocene (Cowling et al. 2008). Molecular studies in unrelated faunal taxa also provide evidence for separate lineages in the Langeberge and the Agulhas Plain (e.g., Price et al. 2007; Moussalli et al. 2009; Gouws et al. 2010; McDonald & Daniels 2012) and for an absence of gene flow between these areas (Myburgh & Daniels 2015). Species of Chondrocyclus have not been recorded in the Riviersonderendberge where apparently suitable habitat exists.
There are morphological differences between populations of C. kevincolei sp. nov. (Table 4). The number of spiral rows of hairs is fewer in the Bredasdorp population (only 4–5 as opposed to 8–15 in the Platbos and Grootbos populations). The colour of the living animal is creamy white with only slight pigmentation of the tentacles in the Platbos population and dark grey to almost black at Bredasdorp. There were relatively large genetic divergences between populations (Cole et al. 2019). Their long branch lengths (Fig. 1) suggest isolation in shrinking refuges as arid-adapted vegetation replaced forest (see Tolley et al. 2006, 2008). Recent radiations of faunal taxa in this region are associated with adaptation to open habitats (Tolley et al. 2006; Herbert & Moussalli 2010). Sea level changes have also had dramatic effects on vegetation of the Agulhas Plain (Linder 2003) and its biota with marine transgressions potentially restricting ancestral populations of Chondrocyclus to refuges at higher elevations and thus driving allopatric divergence or eliminating closely related taxa at lower elevations. Further studies including unsampled populations on the Agulhas Plain and additional markers may shed light on whether separate populations may warrant species status. It was, however, decided to treat these as one species pending further investigation. By contrast, C. langebergensis sp. nov. occurs in relatively stable relictual forest patches in the Langeberge and has undergone little change.
description: Published as part of Cole, Mary L., 2019, Revision of Chondrocyclus s. l. (Mollusca: Cyclophoridae), with description of a new genus and twelve new species, pp. 1-92 in European Journal of Taxonomy 569 on pages 56-59, DOI: 10.5852/ejt.2019.569, http://zenodo.org/record/3517522