Pectinidae Wilkes, 1810

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 266-269

Family Pectinidae Wilkes, 1810

[as Pectinoidae, emend. Waller, 1978]

Attempts at producing a dichotomous key to the 20 genera of the Pectinidae occurring within the region covered proved unsuccessful on account of the variability of many characters within most genera, and the difficulty of defining degree of development of such characters. Instead, brief diagnoses of generic characters are summarised below, using shell characters. Similarly, descriptions of species have been reduced to diagnostic characters, so that separate diagnoses are not presented.

Synopsis of genera of Pectinidae in South Africa and Mozambique:

Delectopecten: Convex , fragile, inequivalve, equilateral, nearly orbicular, attains 30 mm in height, valves sculptured with commarginal rows of scales or vesicles, spinose radial ridges and/or delicate antimarginal striae, auricles unequal in size, byssal notch well-developed, ctenolium prominent.

Pseudamussium: Convex , fairly solid, inequivalve, slightly equilateral, nearly orbicular, attains 60 mm in height, valves with radial plicae or costae, sculptured with delicate to prominent radial ridges and/or radial striae, antimarginal microsculpture, auricles unequal in size, byssal notch shallow, ctenolium present.

Anguipecten: Convex , solid, inequivalve, slightly equilateral, suborbicular to elongate, laterally compressed, attains 70 mm in height, valves with 9–40 regularly spaced radial lirae, sculptured with delicate, closely spaced, commarginal lamellae, auricles more or less equal in size, byssal notch obsolete, ctenolium weak.

Bractechlamys: Convex , solid, inequivalve, equilateral, suborbicular to elongate, attains 60 mm in height, valves with 8–15 regularly spaced primary radial lirae, sometimes with nodules, secondary radial riblets present, prominently ribbed auricles unequal to subequal in size, byssal notch relatively deep, ctenolium weak.

Decatopecten: Convex , solid, inequivalve, juvenile equilateral, adult slightly inequilateral, suborbicular to elongate, attains 120 mm in height, valves with 5–15 regularly spaced primary radial lirae, closely spaced commarginal lamellae, delicate antimarginal microsculpture in early ontogeny and secondary radial sculpture in late ontogeny, byssal notch small, ctenolium weak.

Glorichlamys: Convex , solid, inequivalve, equilateral, suborbicular to elongate, attains 25 mm in height, valves with regularly to irregularly spaced radial lirae, simple to quadripartite, commarginal interstitial lamellae, auricles very unequal in size, byssal notch deep, ctenolium well developed.

Gloripallium: Convex , solid, inequivalve, equilateral, orbicular to suborbicular, attains 100 mm in height, valves with 7–14 regularly spaced primary radial lirae with prominent commarginal lamellae, secondary radial riblets (sometimes lacking), auricles unequal in size, noduliferous antimarginal macrosculpture on auricles, commarginal microsculpture on auricles and in early growth stages, byssal notch deep, ctenolium well developed.

Juxtamusium: Inflated , left valve nearly flat, right valve convex, rather fragile, equilateral to inequilateral, orbicular to suborbicular, attains 30 mm in height, valves with regularly to irregularly closely-spaced, weak radial lirae or riblets, delicate commarginal microsculpture throughout ontogeny, auricles nearly equal in size, resilifer on one side strongly erect, byssal notch shallow, ctenolium on both valves.

Mirapecten: Inflated , right valve more convex than left valve, solid to rather fragile, equilateral to inequilaterial, orbicular to suborbicular, attains 40 mm in height, valves with 5–7 regularly spaced primary squamous lirae to 7–11 irregularly spaced primary and secondary lirae, auricles unequal in size, microsculpture of closely spaced commarginal lamellae, byssal notch moderately deep, ctenolium well developed.

Pecten: Left valve almost flat, right valve strongly convex, solid, equilateral, orbicular to suborbicular, attains 150 mm in height, valves with radial macrosculpture and commarginal microsculpture, auricles almost equal in size, byssal notch weak, ctenolium weak in juvenile and absent in adult.

Laevichlamys: Weakly convex, solid, inequivalve, inequilateral, elongate, attains 60 mm in height, valves with delicate radial ribs or riblets (irregularly or regularly spaced), shagreened or reticulate microsculpture secondarily commonly lacking, intercalated antimarginal striae, commarginal lirae absent, byssal notch deep, ctenolium well developed.

Pedum: Solid , flattened left valve, convex right valve, dorsoventrally elongate, attains 100 mm in height, microsculpture of numerous scabrous radial riblets and closely spaced commarginal lamellae, anterior auricle in late ontogeny strongly curved, posterior nearly lacking, byssal notch deep, ctenolium present in immature, lacking in adult; living embedded in coral.

Semipallium: Weakly convex, solid, inequivalve, equilateral to inequilateral, elongate, up to 70 mm in height, regularly or irregularly spaced strong to weak primary radial lirae or costae, delicate secondary radial riblets commonly in late ontogeny, shagreened or reticulated microsculpture throughout ontogeny, auricles very unequal in size, byssal notch deep, ctenolium well developed.

Talochlamys: Rather inflated, weakly convex, solid to fragile, inequivalve, equilateral to inequilateral, elongate, attains 40 mm in height, valves with irregularly spaced primary radial squamous costae, secondary interstitial riblets in late ontogeny, microsculpture of weak antimarginal striae, intercalated widely spaced prominent commarginal lamellae, shagreened microsculpture commonly lacking, byssal notch deep, ctenolium well developed.

Veprichlamys: Rather inflated, weakly convex, rather fragile, inequivalve, inequilateral, elongate, attains 40 mm in height, valves with preradial antimarginal microsculpture, squamous primary and secondary intercalated (commonly in late ontogeny) radial macrosculpture, interstitial antimarginal microsculpture (rarely reticulate), byssal notch deep, ctenolium well developed.

Mimachlamys: Convex to rather inflated, solid, inequivalve, slightly equilateral, suborbicular to elongate, attains 100 mm in height, valves with preradial granulated microsculpture, macrosculpture commonly of regularly spaced, solid radial costae with spines, flanked with secondary costellae, antimarginal and/or divaricating interstitial microsculpture, byssal notch deep, ctenolium well developed.

Aequipecten: Convex to rather inflated, solid, inequivalve, slightly equilateral, orbicular to suborbicular, attains 80 mm in height, valves with preradial granulated microsculpture, macrosculpture of regularly spaced, radial costae, in early radial stage ventrally concave commarginal lamellae on rib flanks, auricles unequal in size, interstitial shagreened or ‘herringbone’ microsculpture lacking, byssal notch moderately deep, ctenolium present.

Cryptopecten: Very variable in convexity, solid, inequivalve, inequilateral, orbicular to suborbicular, attains 30 mm in height, valves with 12–25 radial costae, commonly lamellose, interspaces with delicate imbricated scales, auricles unequal in size, byssal notch moderately deep, ctenolium well developed.

Haumea: Left valve flattened and right valve strongly convex, solid, equilateral to inequilateral, nearly orbicular, attains 30 mm in height, macrosculpture of regularly spaced radial lirae, delicate closely spaced commarginal lamellae throughout ontogeny, auricles moderately small and nearly equal in size, byssal notch deep, ctenolium present.

Volachlamys: Rather flattened, convex, solid, inequivalve, nearly equilateral, orbicular to suborbicular, attains 60 mm in height, macrosculpture of regularly spaced prominent radial lirae and commarginal lamellae throughout ontogeny, intercalated imbricate microsculpture in early radial stage, weak intercalated radial microsculpture in late ontogeny (also lacking), byssal notch deep, ctenolium well developed.