Wallerconcha sarae Valentich-Scott & C.L. Powell

Valentich-Scott, Paul, Powell, Charles L., II,, Lorenson, Thomas D. & Edwards, Brian E., 2014, A new genus and species of Thyasiridae (Mollusca, Bivalvia) from deep-water, Beaufort Sea, northern Alaska, ZooKeys 462, pp. 11-26 : 14-19

Taxon classification Animalia Lucinoida Thyasiridae

Wallerconcha sarae Valentich-Scott & C.L. Powell sp. n. Figure 3 A–H, 7B

Description.

Shell shape. Shell subtrigonal, moderately thin, equivalved, highly inflated; anterior margin broadly rounded; posterior end subtruncate; umbo broadly rounded, strongly prosogyrate; dorsal margin strongly sloping on both sides of the umbo; escutcheon moderately narrow, moderately deep, well-defined; lunule absent. Maximum length 24 mm, maximum height 24 mm, maximum width 17 mm.

Sculpture and periostracum. Shell with closely spaced, irregular commarginal striae and ribs; shallow, narrow radial sulcus extends from posterior of the umbo to the posterior ventral margin; shallow radial depression from the umbo to the central ventral margin, forming a slight undulation along the ventral margin; periostracum thick, wrinkled, dehiscent, light to dark brown, silky.

Hinge. Hinge heavy, edentulous, or with minute tubercles under beaks; anterior section narrow; posterior section with wide lateral platform, supporting deeply sunken nymph; ligament external, deeply sunken, long, dark brown.

Adductor muscle and pallial scars - anterior adductor muscle scar large, long, wide, subelliptical, with irregular upper and lower margins, upper margin of scar concave near the center; posterior adductor muscle scar smaller, irregular ovate, with a pointed projection in juveniles; pallial line scalloped, without a sinus.

Interior - interior dirty white to gray; with faint radial crescent-shaped lines that extend from near the umbo to the near the ventral margin, lines have broad depressions between them near the central ventral margin.

Type locality.

USA, Alaska, Beaufort Sea, Canning Seafloor Mound. Specifically, 71.317°N, 143.999°W; 2,358 m water depth (ECS004 137, Core IP– 1, section 3, 31 cm, 4.65 mbsf).

Type specimens.

Holotype - SBMNH 235481, 1 pair, length = 23.9 mm, height = 21.3 mm, width = 16.7 mm. Alaska, Beaufort Sea, Canning Seafloor Mound; 71.317°N, 143.999°W; 2,358 m water depth (ECS004137, Core IP– 1, section 3, 31 cm; 4.65 mbsf)

Paratype 1 - CAS paratype 72852

Alaska, Beaufort Sea, Canning Seafloor Mound; 71.317°N, 143.998°W; 2,350 m water depth (ECS 004 122. Core 1 GB– 1 102 cm, 1.02 mbsf); length = 12.8 mm, height = 10.9 mm

Paratype 2 - LACMIP paratype 14470

Alaska, Beaufort Sea, Canning Seafloor Mound; 71.317°N, 143.999°W; 2,358 m water depth (ECS004242, Core IP1, section 1, 52 cm, 2/2, 0.52 mbsf); length = 15.0 mm, height = 13.1 mm

Paratype 3 - SBMNH paratype 235613

Alaska, Beaufort Sea, Canning Seafloor Mound; 71.317°N, 143.998°W; 2,350 m water depth (ESC004180, Core 1 GB– 1, 44 cm, 0.44 mbsf); length = 19.2 mm, height = 17.5 mm

Paratype 4 - SBMNH paratype 235614

Alaska, Beaufort Sea, Canning Seafloor Mound; 71.317°N, 143.998°W; 2,350 m water depth (ESC004180, Core 1 GB– 1, 44 cm, 0.44 mbsf); length = 23.9 mm, height = 23.8 mm.

Etymology.

Named in honor of Sara Powell, of San Jose, California, daughter of Charles L. Powell.

Distribution.

Wallerconcha sarae is presently only known only from the region around the type locality; the Canning Seafloor Mound (71.3175°N, 143.9997°W), Beaufort Sea, Alaska, USA. Given the collection depth of 0.02-4.65 mbsf, we surmise this is a fossil species. However we cannot discount that it could still be living in the region.

Other specimens examined.

Piston core: ESC 004112, Core 1P1, section 4, 15 cm, 4.65 mbsf (articulated specimen; frozen for further analysis), ECS 004137, Core 1P1, section 3, 31 cm, 181 mbsf (one articulate specimen (holotype Figure 3 A–G), three larger fragments), ESC 004242, 1P1, sec. 1, 52 cm, 0.52 mbsf, (one left valve), ESC 004242, 1P1, sec. 1, 52-54 cm, 0.53 mbsf (seven large fragments), ECS 004242, 1P1, sec. 1, 52-54 cm, 0.53 mbsf (one fragment). Gravity Core: ESC 004115, Core 1GB1, 0.02 mbsf (left valve; used for chemical analysis), ESC 004122, 1GB1, 102 cm, 1.02 mbsf (one small left valve), CS 004180, Core 1GB1, 44 cm, 0.44 mbsf (one articulate specimen, one left valve, two fragments). EESC 004257, Core 1TC1, section 1, 72 cm, 0.72mbsf (two larger fragments).