Anatoma alternatisculpta, Geiger, Daniel L. & Mclean, James H., 2010

Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), Zootaxa 2356, pp. 1-35 : 15

Anatoma alternatisculpta n. sp.

Figures 11–12

Type material. Holotype USNM 1132066 . 9 paratypes from type locality ( USNM 1132067). 15 paratypes 137–146 m, off Pelican Island, Barbados, 13.167˚N, 59.567˚W ( USNM 500678). One paratype 165–183 m, off Lazaretto, Barbados, 13.133˚N, 59.617˚W ( USNM 1132065, 1).

Type locality. 137 m, Off Pelican Island , Barbados, 13.167˚N, 59.567˚W.

Etymology. Alternati-, Latin for differing on two sides, -sculpta, Latin for sculpture, referring to the predominant axial sculpture on shoulder, while the base has predominantly spiral sculpture. Adjective.

Description. Shell medium size (to 2.09 × 2.15 mm W × H), trochiform globular. Protoconch of 0.875 whorls, 175 µm long in holotype, embryonic cap with some flocculent sculpture, remainder smooth, weak apertural varix not connected to embryonic cap, apertural margin slightly sinusoid. Teleoconch I of 0.66–0.75 whorls, 14–19 axial cords, some with a spiral cord in position of selenizone. Teleoconch II of 2.66 whorls, suture moderately impressed. Shoulder strongly convex, approximately 34 distinct equally spaced axial cords; first spiral line shortly after onset of selenizone, 3–4 thick spiral lines at apertural margin concentrated in middle of shoulder, running over axial cords forming minute thickenings. Base with weak constriction below selenizone, evenly curving into umbilicus, approximately 20 axial cords of decreasing strength from selenizone towards mid-base, then increasing in strength towards umbilicus; about twice as many thick spiral threads as on shoulder, weak below selenizone, increasing in strength to cords towards umbilicus. Umbilicus open, moderately wide. Selenizone at periphery, keels moderately strong, strongly elevated, lunules distinct; slit open, with parallel margins. Aperture round, flared, roof overhanging. Animal unknown.

Differential diagnosis. Anatoma proxima from the SE United States to Brazil has similar sculpture on shoulder and base, a less convex shoulder, and a protoconch with flocculent sculpture. Anatoma atlantica ( Bandel, 1998) from the eastern US is proportionally wider (width to height ratio 1.219 in holotype of A. atlantica , 0.973 in holotype of A. alternatisculpta ), has finer sculpture and a much larger protoconch. Anatoma plicatazona n. sp. from the Caribbean has a more turreted shell form, and the keels of the selenizone are strongly curved towards the apex. Anatoma alta (Watson, 1886) from the NE Atlantic is more globular in shape, the selenizone distinctly above the periphery, and has similar sculpture on shoulder and base.

Figures

FIGURE 11. Holotype of Anatoma alternatisculpta n. sp. 137 m, Off Pelican Island, Barbados, 13.167 ˚ N, 59.567 ˚ W. USNM 1132066. Scale bar shell = 1 mm. Scale bar protoconch = 100 µm.

FIGURE 12. Paratypes of Anatoma alternatisculpta n. sp. A – B. 137 – 146 m, off Pelican Island, Barbados, 13.167 ˚ N, 59.567 ˚ W (USNM 500678). C. One paratype 165 – 183 m, off Lazaretto, Barbados, 13.133 ˚ N, 59.617 ˚ W (USNM 1132065, 1). Scale bar shell = 1 mm. Scale bar protoconch = 100 µm.