Amalda alabaster, Kantor & Castelin & Fedosov & Bouchet, 2020
Kantor, Yuri I., Castelin, Magalie, Fedosov, Alexander & Bouchet, Philippe, 2020, The Indo-Pacific Amalda (Neogastropoda, Olivoidea, Ancillariidae) revisited with molecular data, with special emphasis on New Caledonia, European Journal of Taxonomy 706, pp. 1-59 : 36-40
treatment provided by
Amalda alabaster sp. nov.
Figs 13 View Fig D–E, 15
Shell small, up to 27 mm, ovate fusiform, with low broad conical spire and small low dome shaped protoconch (diameter of first whorl ca 0.8 mm). Primary callus smooth, shallowly impressed on left side at last whorl suture, secondary callus weakly microshagreened. Olivoid groove very shallow and indistinct. Anterior band separated by distinct fasciolar ridge into upper and slightly broader lower bands. Colour uniformly white.
The specific epithet refers to the white and semitransparent shell. Used as a noun in apposition.
SOUTHERN NEW CALEDONIA • 22°06′ S, 167°03′ E; 190–200 m deep; TERRASSES; stn DW3093; MNHN IM-2007-43627; sequenced. GoogleMaps
9 sequenced specimens ( Table 1).
Not sequenced material
NEW CALEDONIA • 1 lv; type locality; IM-2007-43633 • 3 lv; Bassin des Loyauté ; 21°45′ S, 166°37′ E; 253–266 m deep; HALIPRO1; stn CP852 GoogleMaps • 3 dd; 17 lv; 21°45′ S, 166°37′ E; 241–250 m deep; HALIPRO1; stn CP853 GoogleMaps • 6 dd; east coast of mainland New Caledonia ; 21°48′ S, 166°41′ E; 239–250 m deep; BATHUS 1; stn DW649 GoogleMaps • 8 dd; 21°48′ S, 166°41′ E; 264–269 m deep; BATHUS 1 ; stn DW650 GoogleMaps • 5 dd; 21°17′ S, 165°57′ E; 237–298 m deep; BATHUS 1 ; stn DW654 GoogleMaps • 42 lv; 4 dd; 21°45′ S, 166°37′ E; 250 m deep; BATHUS 1; stn CP713. GoogleMaps
MEASUREMENTS. SL 26.7 mm, AL 13.5 mm, SW 10.7 mm.
SHELL. Small, ovate fusiform with relatively broad base, SW/SL 0.40; body whorl evenly weakly convex on right side, and slightly bulging on left side due to strong callus, greatest width of body whorl median. Protoconch nearly completely covered by callus with part of first whorl exposed, low dome shaped. First protoconch whorl diameter 0.79 mm. Spire low, broadly conical; primary callus thick and covering all whorls except part of protoconch, shallowly impressed on left side at last whorl suture. Surface of callus glossy, smooth, with weak indistinct spiral ridges, secondary callus thick, with distinct anterior border, joining parietal callus without visible border, extending to right ventral side of last whorl and continuing up to form a thick, tongue-shaped pad that reaches suture of antepenultimate whorl. Surface of secondary callus weakly shagreened. Body whorl cloak weakly glossy, smooth, not microshagreened. Olivoid groove very shallow and indistinct, terminating in short, broadly triangular, labral denticle. Rear edge of anterior band very sharp and distinct. Anterior band subdivided into upper and lower parts by distinct fasciolar ridge. Both upper and lower bands very weakly evenly convex, nearly flat. Plication plate with deep and broad groove at upper third, separating adapical largest spiral ridge, and two slightly smaller ridges similar in size. Columella smooth. Aperture irregularly oval, rounded posteriorly due to callus, widest medially; outer lip medium thick, orthocline in side view, nearly straight, with slight, blunt labral denticle; siphonal notch shallow, symmetrically U-shaped. Colour uniformly white.
RADULA (n =3) ( Fig. 13 View Fig D–F). Similar in all specimens. Central tooth tricuspid, with central cusp slightly longer than lateral ones. Cusps smooth, but lateral flaps strongly serrated and bearing longitudinal grooves between cusplets. 1–4 additional small cusplets between central and lateral major cusps.
All sequenced specimens of A. alabaster sp. nov. are very similar to the holotype. In addition to pure white specimens, some are light ivory in colour of the upper teleoconch whorls or even of the entire shell (MNHN IM-2007-43583, Fig. 15 View Fig C–D).
Conchologically Amalda alabaster sp. nov. is extremely similar to white specimens of A. montrouzieri . The slight differences may be the more regularly oval outline and the more cyrtoconoid spire of A. montrouzieri , but those differences are very subtle. The new species is recorded at larger depths than
Although A. montrouzieri and A. alabaster sp. nov. are closely related, a large genetic distance between them confirms their distinction. Furthermore, there appears to be a minor difference in the radula. In A. montrouzieri the central cusp of the central tooth is clearly shorter than the lateral ones, but in A. alabaster sp. nov. the situation is opposite – the central cusp is distinctly longer. The illustration of the radula of A. montrouzieri by Kilburn & Bouchet (1988: figs 51, 53) shows a central tooth with a morphology similar to that in our A. alabaster sp. nov. Regrettably, the authors did not present the station data of the specimen from which the radula was extracted and, therefore, it is not clear whether they indeed examined A. montrouzieri . All our sequenced specimens originated from only two stations off south and south-eastern New Caledonia at depths of 180–210 m, but numerous non-sequenced specimens (see Material) were collected in the depth range of 237– 298 m. Some have a light yellowish spire callus and upper anterior band.
One specimen (MNHN IM-2013-63897, Fig. 15 View Fig H–I) from a station more to the North on the east coast of New Caledonia is sister to A. alabaster sp. nov., with a very high support. Conchologically it differs from A. alabaster sp. nov. in having a stouter shell with thicker primary callus and a more pronounced colouration. It may represent a geographical morph (although it was collected very close to the type locality of A. alabaster sp. nov.) or even a separate species, but at the moment the lack of additional sequenced material does not allow to draw firmer conclusions. So, we refer to this and similar specimens as A. cf. alabaster sp. nov. The ABGD analysis also attributed A. cf. alabaster sp. nov. to the same PSH as A. alabaster sp. nov.
South-eastern New Caledonia, in 180– 280 m.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.