Kelliella rotunda ( Thiele & Jaeckel, 1931 )

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 85-86

Kelliella rotunda ( Thiele & Jaeckel, 1931)

Figures 43 A–D

Vesicomya rotunda Thiele & Jaeckel, 1931: p. 231 , pl. IV, fig. 105a.

Vesicomya rotunda Thiele & Jaeckel, 1931 — Boss, 1970: p. 76, figs. 12, 15–16.

Kelliella japonica Hayami & Kase, 1993: p. 91 , figs. 321–330. (syn. nov.)

Kelliella japonica Hayami & Kase, 1993 — Okutani, 2000: p. 993, pl. 495, fig. 2.

Material examined. One articulated specimen and nearly two dozen single valves (2 to 3 mm) (BK).

Diagnosis. Shell small (up to 3 mm in length), suborbicular and strongly inflated. Umbones low, while the lunule is pronounced and well defined. Exterior surface hyaline with commarginal sculpture. Interior shiny, with a fine furrow which runs along the entire margin. Hinge consists of two subparallel teeth in the RV, while the LV has one tubercular and one lamellar tooth.

Remarks. Hayami and Kase (1993) described the minute, 2.5 mm Kelliella japonica from bottom sediments in subtidal caves from Ie Islet, Okinawa. From EI the species is represented by 17 single valves, dredged from 30–50 m, and ranging in size from 1.8–3 mm. These conform to the hinge, suborbicular outline, size, defined lunule, and shiny surface with a commarginal sculpture to that of K. japonica .

Hayami and Kase compared their new species with K. galatheae Knudsen, 1970 , K. elegantula R.F. Bernard, 1989 , and K. sundaensis Knudsen, 1970 , as well as with the fossil species K. barbara Studencka, 1987 , and K. nakayamai Habe, 1953 . Unfortunately, they overlooked Vesicomya rotunda Thiele & Jaeckel, 1931 from Indonesia, also recorded from the Philippines and the South China Sea. Kelliella rotunda also shares the name giving rounded shape, the shiny and commarginally sculptured surface, the minute size of 2–3 mm, the defined lunule and the weakly protruding umbones. Furthermore, it lives in the same biogeographic area. Boss (1970: 76) redescribed and illustrated this species, including the hinge, and provided further records.

We see no arguments to keep K. japonica separate from the earlier K. rotunda . Thus, Kelliella japonica is here formally synonymized and the range of K. rotunda enlarged to include Okinawa and Easter Island.

Boss provisionally assigned rotunda to Kelliella . Allen (2001: 224) and Huber (2010: 706) confirmed the kelliellid placement.

Krylova & Sahling (2010) recently proposed a different view and advocated the genus Vesicomya Dall, 1886 for rotunda . However, their inclusion of the type species of Kelliella , namely, K. abyssicola , into Vesicomya which confirms that Vesicomya is a junior synonym of Kelliella .

They further proposed a separation of the group into small and large vesicomyids. However, substantial anatomical or genetic support for this new grouping was not provided. Consequently, the views of Allen (2001) and Huber (2010) are followed and Kelliella rotunda retained in Kelliellidae .

Habitat. Commonly found at various sublittoral locations around Easter Island, in fine sand, from 30–150 m, Recorded from sublittoral and lower bathyal, as well as in subtidal caves from other locations.

Distribution. Previously Kelliella rotunda was only known from Sumatra, the Philippines, South China Sea and Okinawa. Easter Island is now considered a range extension— E4.