Talochlamys contorta Dijkstra, 1993
DIJKSTRA, H. H. 1993. Talochlamys contorta n. sp. from southern East China Sea (Bivalvia: Pectinidae). La Conchiglia, 25 (268): 24-28, figs 1-13 [p. 24, figs 1-5 ]
1993 Talochlamys contorta Dijkstra, 1993
H. H. Dijkstra, 1993, figures 1-5.
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«Talochlamys contorta sp. nov.
Description
Shell rather small, approximately 20 mm. in height, higher than wide, and equilateral. Anierior and posterior auricles very unequal (5.5 x 3.2 mm.). Umbonal angle of about 95°. The exterior surface of the left valve is composed by very small scratches beneath the umbonal apex. About 14 irregular immature radial costae start approx. 2 mm. beneath the apex and increase in number to 18 primary radial costae, with one to four irregular secondary interstitial radial riblets, near the ventral margin. Primary and secondary ribs are rounded and bear smal1 circular lamellae. Between the radial costae a microscopic irregular diverged granulation is visible (30 x), sometimes covered by concentric ridges (antero-central region), and crossed by small secondary radial riblets. The anterior auricle of the left valve bears about ten radial costae with fine pronounced scales and interstitial scratch whereas the posterior auricle has fewer radial riblets, which are somewhat flatter. The exterior surface of the right valve has more irregular radial costae, and the microscopic diverged granulation ('Camptonectes' structure) is most developed near the antero-marginal region. Concentric ridges are lacking, but growth lines are present near the ventral margin. The lamellae on the radial costae are nearly absent. The byssal fasciole is rather broad, and on the suture an inactive and active ctenolium (5 teeth) is well developed. The interior surf'ace of both valves has irregular fine plicae, and is glossy white with a brownish spot near the umbonal region. The resilial insertion is triangular and erected. The posterior and anterior outer ligament insertions are strongly developed with cardinal crura on both auricles. The colouration is basically creamy on the left valve with a brown spot and white dots near the umbonal region, and brownish coloured ones on the primary costae. The right valve is uniform milky-white coloured with a creamy spot near the umbo. Locus typicus
Dredged alive by commercial fishing of coralboats off northeastern Taiwan on the Taiwanese shelf; 1981. Don. F. Nolf (ex T.C. Lan). Paratypes will be distributed to: Australian Museum Sydney (AMS); Institute of Oceanology Academia Sinica. Qingdao (lOAS); Museum National d'Histoire Naturelle, Paris (MNHN); National Natuurhistorisch Museum. Leiden (NNM); National Museum of New Zealand, Wellington (NMNZ); National Science Museum, Tokyo (NSMT); U.S. National Museum of Natural History, Washington (USNM); Western Australian Museum, Perth (WAM). Distribution
So far only known from the type locality. Live collected specimens were bysally attached to corals on sandy bottoms at littoral to sublittoral depths. Etymology
This species has a complex sculpture (Latin: contortus, adi.) on the exterior surface of the left valve. Comparison
Talochlamys contorta is most similar to Talochlamys multicolor (Melvill & Standen, 1907) from Gough Island (40°20'S 9°56'W), S. Atlantic Ocean, as for the conchological features of the complex sculpture of the left valve. The sculpture of T. multicolor is more pronounced, viz. the radial costae are more strongly developed, and also the lamellae on the costae of both valves. Melvill & Standen (1907: 147) compared T. multicolor with Chlamys limatula (Reeve, 1853), an Indo-Pacific pectinid, which has fine regular close-set radial costae on both valves. Wagner (1982: 86) placed the latter species in the synonymy of Chlamys irregularis (Sowerby II, 1842), and Rombouts (1991: 33) also, together with T. multicolor and some other species. The irregular radial costae of C. irregularis are more pronounced and fewer in number. This species is also larger, more oblong, and highly coloured, with prickly scales on the radial costae. C. limatula is more similar to Chlamys marshallensis Waller, 1972, and perhaps even a senior synonym of it.
Talochlamys famigerator (Iredale, 1925) from the southern region of Australia (S.W.A. to N.S.W.) is also alike T. contorta with the same complex structure on the left valve. However, this sculpture is more variable, sometimes with Mimachlamys characters in the mature stage, and much more pronounced. Talochlamys dichroa (Suter, 1909), another representative from New Zealand, has the most pronounced sculpture, with very strongly developed radial costae. it is possible that Talochlamys taiaroa (Powell, 1952), which is similar in size and shape to T. dichroa, but weaker in sculpture, is only a variant of the latter species.
It is remarkable that most of the Talochlamys species are living in the temperate zone of the southern hemisphere, and only T. contorta, so far, in the tropical zone of the western Pacific. Talochlamys lredale could be best placed in the Mimachlamys group (Waller, 1991).» HENK H. DIJKSTRA, 1993
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