Leptochiton antarcticus Sirenko, 2015

Sirenko, Boris, 2024, The chitons of the family Leptochitonidae (Mollusca: Polyplacophora) from the Emperor Seamounts, Pacific Ocean, Zootaxa 5474 (5), pp. 522-532 : 528

Leptochiton antarcticus Sirenko, 2015

Leptochiton antarcticus Sirenko, 2015a: 139 , figs 1–7; 2019b: 71, Figs 1–3 .

Type material. Holotype (ZISP 2250); 2 paratypes (ZISP 2251, 2252).

Type locality. Southern Ocean , Scotia Sea, off South Sandwich Islands, 59°42.0’S, 28°12.9’W, 142–160 m, gravel, mud .

Remarks. Besides the widespread specimens known from the slopes of Antarctica, the only other report of a specimen of this species was found on the slope of Nintoku Seamount ( Sirenko 2019b). Externally, L. antarcticus differs little from the other two species of the Emperor Seamounts ( Leptochiton milwaukensis n. sp. and Belknapchiton belknapi ). Like these species, L. antarcticus also has tegmentum granules arranged quincuncially on the head valve, lateral areas of intermediate valves and postmucronal area of tail valve and the dorsal scales have longitudinal ribs.

Leptochiton antarcticus differs from L. milwaukensis n. sp. by having 5 round pores of aesthetes in granules of the tegmentum (vs. 3 pores, 2 of them slit-shaped in L. milwaukensis n. sp.). The shape of the central teeth of the radula is also very different in these two species. Leptochiton antarcticus differs from Belknapchiton belknapi by having 5 aesthetes in granules of the tegmentum (vs. 3 aesthetes in B. belknapi ) and 12–16 longitudinal ribs on the dorsal scales (vs. 1–3 ribs in B. belknapi ). The shape of the central teeth of the radula is very different in these two species.

Figures

FIGURE 1. Map with locations of the Emperor Seamounts explored during the 33rd cruise of the R/V Odyssey in 1984.

FIGURE 2. Leptochiton milwaukensis n. sp., Pacific Ocean, Emperor Seamounts, Milwaukee Seamount, 675 m, holotype (ZIN 2473) BL 3.4 mm. A. Valve I, dorsal view. B. Valve V, dorsal view. C. Valve IV, dorsal view. D. Valve II, dorsal view. E. Valve V, detail of tegmentum in central area. F. Valve V, rostral view. G. Whole specimen, dorsal and lateral views.

FIGURE 3. Leptochiton milwaukensis n. sp., Pacific Ocean, Emperor Seamounts, Milwaukee Seamount, 675 m, holotype (ZIN 2473) BL 3.4 mm. A. Dorsal scales, marginal needles. B. Dorsal scales, marginal needles and scales. C. Sutural needles. D. Dorsal and ventral scales.