Talochlamys humilis (Sowerby, 1904)

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 298-300

Talochlamys humilis (G. B. Sowerby 3rd, 1904), comb. n.

(Figs 36–37)

Chylams [sic] humilis Sowerby, 1904: 3 , pl. 6, figs 3. Type locality: 65 mi. off Cape St. Blaize , N by E + E

(= S by W + W), Agulhas Bank, 90 fath. (165 m).

Chlamys humilis ; E. A. Smith, 1906: 59; Kilburn & Rippey, 1982: 216; Lussi, 1995: 2, fig. 7.

Chlamys tincta [in part]; Barnard, 1964: 424; idem, 1974: 761.

Chlamys (Chlamys) humilis ; Wagner, 1983: 145–148, figs 2, 6–8 (references, type data, description,

discussion).

Description: Shell height to ca. 25 mm (averaging 15–20 mm), suborbicular to elongate, RV somewhat more convex than LV, inequilateral, auricles strongly unequal, umbonal angle ca. 85–90°. Both valves sculptured with numerous, closely spaced, rounded, squamous radial costae (ca. 55–70). Preradial stage of LV with microscopic antimarginal striae and commarginal growth ridges, on RV nearly smooth. Intercostal antimarginal striated microsculpture throughout, intercostal commarginal lamellated microsculpture on central part of disc. Anterior auricle of LV with 8–10 squamous radial riblets with weak interstitial antimarginal microsculpture, posterior with 3–5 weakly squamose radial riblets and more prominent antimarginal microsculpture. Anterior auricle of RV with

36

37

Figs 36–37. Talochlamys humilis (Sowerby, 1904) : NMSA V754 , S of Cape St Blaize, Agulhas Bank , 101 m, pv, 23.1 x 20.9 mm. 36. LV exterior. 37. RV exterior .

5–6 lamellated radial riblets, on posterior auricle very weak, with or without 3–5 spinous radial riblets, antimarginal striated microsculpture well developed. Hinge line straight, somewhat declivous on antero-dorsal margin. Byssal fasciole broad, byssal notch rather deep, active ctenolium with 4–7 prominent teeth on suture. Auricular crura well developed; resilifer triangular-oblong. Colour strongly variable, uniform cream, yellow, orange, reddish, pinkish, purplish or brownish, also with dark or light rays and pale streaks.

Type material: Lectotype SAM 14858 , designated by Wagner (1983: 145, fig. 2); paralectotype BMNH 1904.12 .23.163. Seen by HD.

Wagner (1983: 145) selected the SAM syntype as lectotype, although it was only Sowerby’s second mentioned specimen. He selected two valves in the BMNH type lot as paralectotypes, and identified these as ‘ Chlamys tincta ’. However, Waller has pointed out (pers. comm., 1977) that these valves do not match, and that only the RV was a potential lectotype. During a visit to the BMNH (pers. comm., 1986) HD was able to trace the missing LV, which proved to have been accidentally transposed with a LV of the type lot of Pecten altus Reeve, 1853 . Although the BMNH type specimen matches Sowerby’s original description and measurements, Wagner’s lectotype designation must stand.

Regional locality data (all NMSA: NMDP, unless otherwise stated, selected records only): SOUTH AFRICA: Transkei: off Sandy Point, 135–144 m, marine growths, dead (C5029). Agulhas Bank : off Nahoon , 85 m, medium sand, broken shell, dead (B8395); off Kidd’s Beach , 90 m, coarse sand, sponge, live (B7795); off East London , 100 m, live (B7806); off East London , 90 m, sponges, gorgonians, live (B8219); off Storms River , 117 m, ex pisce (V1431); E of Plettenberg Bay, 72 m, thick mud with agglutinated worm tubes and large rocks, live (V3219); SE of Plettenberg Bay, 109 m, live (V147); SE of Tsitsikamma , 115 m, coarse sand and shell gravel, dead (V3488); SSE of Knysna, 101 m, living bryozoan corals, sand and shell gravel, live (V981); same loc., 103 m, bored rocks, hard clay, live (V3302); SE of Knysna, 99 m, live (V1117); S of Cape St Blaize , 101 m, ex pisce, dead (V1303); S of Gouritz River mouth, 108 m, living between folds of bryozoan (V754); SSE of Cape Infanta , 91 m, coarse shell grit, dead (V676) .

Distribution: Endemic to Agulhas Bank of South Africa as far east as western Transkei. Habitat: Continental shelf from about 70–140 m, living byssally attached to rocks, bryozoans and other growths.

Remarks: Barnard (1964: 424) treated T. humilis as a junior synonym of Pecten tinctus Reeve, 1853 [= T. multistriata ( Poli, 1795) ], but Kilburn & Rippey (1982: 216) gave reasons for regarding it as a valid species. The sculpture of humilis (interstitial antimarginal striae and commarginal lamellae) agrees better with that found in genus Talochlamys than in Chlamys (in which there is interstitial shagreened or reticulated microsculpture).

T. humilis appears to be an important prey species of the horsefish Congiopodus torvus (Gronovius, 1772) , from whose gut large samples have been taken.