Anatoma tangaroa, Geiger, Daniel L. & Marshall, Bruce A., 2012

Geiger, Daniel L. & Marshall, Bruce A., 2012, New species of Scissurellidae, Anatomidae, and Larocheidae (Mollusca: Gastropoda: Vetigastropoda) from New Zealand and beyond, Zootaxa 3344, pp. 1-33 : 27-28

Anatoma tangaroa new species

( Figures 21–22 )

Chresonymy. Anatoma sp. 6 Spencer et al. 2009: 201.

Type material. Holotype ( NMNZ M.303297 Fig. 21 ). 1.79 × 1.42 mm. Paratypes from type locality ( NMNZ M. 150335, 10: Fig. 22 A). Additional paratypes: Middlesex Bank, NW of Three King Islands, New Zealand, 34.033˚S, 171.733˚E, 246–291 m ( NMNZ M.148568, 25: Fig. 22 C); 28 km S of Great Island, Three King Islands, 34.400˚S, 174.280˚E, 120 m ( NMNZ M. 160285, 15: Fig. 22 B).

Type locality. NW of Three Kings Islands, northern New Zealand, 34.033°S, 171.806°E, 188 m, 27 June 1978, RV Tangaroa , comminuted bryozoans and shell.

Etymology. After RV Tangaroa , from which the type material was dredged. Noun in apposition.

Description. Shell medium size (to 2.2 mm: Figs 21–22 ), trochiform rounded biconical. Protoconch of 0.75 whorl, coarse flocculent sculpture, no apertural varix. Teleoconch I of 0.3 whorl, 5–7 axial cords, spiral in position of selenizone forming thickenings at intersection with axial cords. Teleoconch II of 2.2 whorls, suture moderately impressed; sutsel at onset of selenizone 0.5× width of selenizone, at apertural margin 1–1.5× width of selenizone. Shoulder moderately convex, strong axial cords, approximately 40 on first whorl; first spiral line after 0.2–0.5 teleoconch II whorl, approximately 10–15 at apertural margin, forming small thickenings at intersection with axial cords. Base without constriction below selenizone, same density and strength of axial cords as on shoulder; approximately 20 spiral threads, regularly spaced. Umbilicus open, continuously sloping with base, no funiculus. Aperture rounded, roof overhanging. Selenizone at periphery, rather wide; keels of moderate strength, moderately elevated; lunules distinct; slit open, margins converging towards aperture. Animal unknown.

Distribution. Northern New Zealand, 120– 291 m.

Specimen records. New Zealand. S of Great Island, Three King Islands, 34.235˚S, 172.150˚E, 192–202 m (NMNZ M. 160289, 10).

Remarks. Anatoma amydra from the Indo-Malayan Archipelago has weaker spiral threads on the base, has a protoconch with an apertural varix, and has a longer teleoconch I (>0.5 vs. 0.3 whorl). Anatoma flexidentata from the Indian Ocean to the Western Pacific has a wider selenizone, a narrower sutsel on early whorls (<0.25× vs. 0.5× width of selenizone), and has weaker axial cords. Anatoma pseudoequatoria from the Indo-Malayan Archipelago and Central Pacific has a more subquadrate whorl profile, has no spiral cord in position of the selenizone on teleoconch I, and has a distinct funiculus. Anatoma japonica from the Indo-Pacific has a longer teleoconch (>0.5 vs. 0.3 whorl), has a protoconch with an apertural varix, and the protoconch does not project at the apex. Anatoma maxima from the Indo-Malayan Archipelago to the Western Pacific has a longer teleoconch I (0.75 vs. 0.3 whorl), and has no sutsel on early whorls. Anatoma rainesi from the Eastern and Western Pacific has a protoconch with a varix, and has a longer teleoconch I (0.6 vs. 0.3 whorl). Anatoma rapaensis from the Indo-Central Pacific has no sutsel, has a more impressed suture, and has spiral steps on shoulder and base.

Figures

FIGURE 21. Anatoma tangaroa new species. Holotype, NW of Three Kings Islands, northern New Zealand, 188 m (NMNZ M. 303297). Scale bar shell = 1 mm. Scale bar protoconch = 100 µm.

FIGURE 22. Anatoma tangaroa new species. Paratypes. A. NW of Three Kings Islands, 188 m (NMNZ M. 150335). B. 28 km S of Great Island, Three King Islands, 120 m (NMNZ M. 160285). C. Middlesex Bank, NW of Three King Islands, 246 – 291 m (NMNZ M. 148568). Scale bars shell = 1 mm. Scale bars protoconch = 100 µm.