Bractechlamys adorabilis Dijkstra & Roussy, 1994
DIJKSTRA, H. H. & H. P. ROUSSY, 1994. Bractechlamys adorabilis n. sp. from the Andaman Sea, off southern Phuket Island, Thailand. - La Conchiglia/The Shell, 26 (271): 4-9. [p. 4, figs. 7-12]
1994 Bractechlamys adorabilis Dijkstra & Roussy, 1994
H. H. Dijkstra & H. P. Roussy, 1994, figures 5-8.
H. H. Dijkstra & H. P. Roussy, 1994, figures 9-14.
|
«DESCRIPTION
Shell rather small, up to 22.5 mm in height, convex, slightly oblique, higher than wide, nearly equilateral, auricles unequal (7.8 x 5.5 mm), umbonal angle about 90°. The exterior surface of the left valve is composed with eight rounded radial costae, covered with delicate closely arranged concentric lamellae. The radial interstices are smaller than the radial costae and developed with one to three secondary riblets. The primary costae bear one small crest on the central part. The ventral margin is slightly undulated. The anterior auricle is larger, and provided with a few more radial riblets (7), than the posterior one (5). The sculpture of the right valve is similar to the left, although the secondary radial riblets are very weak and only visible near the periphery. The radial riblets on the anterior auricle are more prominent than on the posterior. On the anterior and posterior side of the dorsal margin strongly developed spines are present. Hinge line is straight. The inner surface is silky and glossy, ornamented with radial plicae, more dominant near the ventral margin. Resilial pit is oblique and triangular. Resilial, intermediate and dorsal teeth well developed and orange-red in colour. Ctenolium present (3 teeth). Byssal notch rather small. The colour of the left valve is pinkish-purple with creamy maculations; the right valve more yellowish-white. The inner side white and glossy with an orange-red blotch near the dorsal margin. TYPE LOCALITY Thailand, off Phuket Island, Kai Islet, 7º44'N 98º37'E, collected alive by a local compressor diver, 7-25 m, rocks and coral, sandy bottom, iii 1992. DISTRIBUTION So far only known from southeastern and southern Phuket Island, Thailand. Specimens are live and dead collected among coral rubble and under coral rocks on a sandy bottom of a bathymetric range of 7-40 m. ETYMOLOGY This species is named after its pretty appearance (Latin: adorabilis, adj.). COMPARISON The closest allied congeneric species is Bractechlamys oweni (de Gregorio, 1884), a nomen novum for Pecten pictus G.B. Sowerby II, 1842 (not Goldfuss, 1833). This species occurs in the western and southwestern Pacific and differs from B. adorabilis by several conchological features: less convex, slightly more orbicular, more closely spaced radial costae (13), somewhat larger auricles; size and coloration are similar. Another allied species is Bractechlamys langfordi (Dall, Bartsch & Rehder, 1938) from the Hawaiian Islands. This species differs from B. adorabilis by a larger convexity, a more orbicular shape, prominent secondary radial riblets, nodules on the primary costae, a different coloration, and a larger size to 30 mm in height. Bractechlamys nodulifera (G.B. Sowerby II, 1842), which is close alike B. langfordi, and known from the western and southwestern Pacific to the western region of the Indian Ocean, differs from B. adorabilis by a larger size up to 45 mm in height, more orbicular in shape, one more radial costa, more prominent secondary radial riblets, nodules on the primary costae, and coloration; the convexity is strongly variable. Young specimens of Bractechlamys vexillum (Reeve, 1853) are also somewhat alike B. adorabilis, and known from the western to the southwestern Pacific. This species is much larger, up to 60 mm in height, covered with a few more radial costae, delicate concentric lamellae are more prominent and more widely spaced, the auricles are somewhat larger, and the coloration is different. Specimens of B. adorabilis could easily be confused with Decatopecten amiculum (Philippi, 1851), known from the same region. The latter species is slightly larger, up to 45 mm in height, more circular in shape, covered with more prominent secondary radial riblets, also on the primary costae, more radial riblets on the auricles, auricles slightly more equal, lacking spines on the dorsal margin of the auricles, convexity and costae variable.» HENK H. DIJKSTRA & HENRY P. ROUSSY, 1994
|