A new species of Aeneator Finlay, 1926 (Mollusca, Gastropoda, Buccinidae) from northern Chile, with comments on the genus and a key to the Chilean species

Abstract A new species of the genus Aeneator Finlay, 1926 is described from off the coast of Caldera (27°S), northern Chile. Aeneator martae sp. n. has a small, broad, stout, angulated shell with more prominent axial ribs and a more obviously keeled periphery than all previously named Chilean species. Comparisons are provided with all other South American named species of Aeneator.


Introduction
The genus Aeneator Finlay, 1926 comprises a group of deep-water gastropods of moderate size, distributed in the South Pacific Ocean around New Zealand (Powell 1979, Beu 1979 and Chile (Rehder 1971, McLean and Andrade 1982, Fraussen and Sellanes 2008. Almost all the species have offshore distributions, and they are common on the sea floor (Dawson 1965, Powell 1979, Beu and Maxwell 1990. Their elongate fusiform shells have rounded whorls with a subsutural concavity, a lip with a broad shallow sinus below the suture, and a sculpture of strong axial ribs overridden by spiral cords (McLean and Andrade 1982).
The present work describes a new species of Aeneator from northern Chile based on shell morphological features. Criteria were shell shape, number of primary spiral cords, development of secondary spirals, and axial sculpture. An identification key, based on shell characters, is given for all the extant Chilean Aeneator species.
Examination was made of shell only specimens; all measurements were made with vernier callipers (± 0.1 mm). For the measure of length of aperture and angle of the spire, the methodology of Dépraz et al. (2009) andChiu et al. (2002)  Distribution. Known only from the type locality; Chile, Region de Atacama, Caldera (27°04'S, 70°50'W), 550-600 m depth.
Diagnosis. A small species of Aeneator, height up to 47.9 mm, shell stout, inside of aperture pale orange, exterior sculptured by well-defined axial ribs, spiral cords, and a conspicuous stepped shoulder.
Description. Shell small for genus (height up to 47.9 mm, Table 1), thick, solid, fusiform, chalky white to pale brownish, inside of aperture pale orange. Shape broad, angulate, length of aperture and canal more than half length of shell, width/height ratio 0.53 to 0.56, whorls convex apart from slightly concave sutural ramp, suture shallow but impressed. Spire angle 63° to 68°. Protoconch and upper teleoconch whorls missing, remaining whorls about 4.5, last 3 with sculpture intact with 7-9 primary spiral cords, interspaces each occupied by one narrow, well defined secondary cord. Last whorl with 16-18 spiral cords, more prominent at periphery of shell than elsewhere, forming a distinct keel. Spire whorls with 24-28 pronounced axial ribs, interspaces deep, each almost equal to a rib in width. Last whorl with 14-15 such ribs. Ribs more pronounced towards the anterior end of shell. Aperture ovate. Parietal and columellar area well-defined, glazed; outer lip thin, slightly crenulated, without lirae or teeth. Siphonal canal short, open, directed slightly to left. Operculum large, thin, dark brown, elongate, nucleus terminal, tip sharp.
Etymology. Named in honour of Mrs Marta Araya, Caldera, Chile, who presented the specimens to the author.
In size, the shell of Aeneator martae sp. n. is similar to A. prognaviter (Figs 20,37,38) and A. portentosus (Figs 35,36). However, the former of these two can be clearly differentiated from the new species by its wider and shorter siphonal canal, less numerous and more curved axial ribs and a thinner, snow white shell (Fraussen and Sellanes 2008). From A. portentosus the new species differs by having a much wider, thicker shell with a shorter spire, a more elongate aperture, dominant axial sculpture and less rounded whorls. Moreover A. portentosus exhibit a very distinctively sculptured peri- ostracum (Fig. 19), with low axial ridges, very different from all the other Chilean Aeneator species. A periostracum is absent in the examined specimens of A. martae sp. n. Aeneator castillai (Figs 33, 34), and A. fontainei (Figs 21-26) differ markedly from the new species by their much larger shells, reaching up to 85.8 mm, more fusiform shells, with a much less stepped or indistinct shoulder, lower and fewer axial ribs, ing the interspaces and exhibits a longer, twisted, siphonal canal. In contrast A. martae sp. n. lacks any brown coloration, shows a sculpture of alternated single major and minor spiral cords defined mostly in the posterior part of the whorls, and has a conspicuous stepped shoulder, forming a keel at the periphery.
Aeneator loisae (Figs 27-32) differs from the new species in having a larger, up to 104 mm, white to snow white shell (different from the white to light brown shell of A. martae sp. n.), more inflated last whorl, with a much longer siphonal canal, a higher number of primary and secondary spiral cords, more prominent spiral sculpture, and fewer, more tenuous, axial ribs.
The new species is tentatively assigned, given the generic uncertainties within the Chilean species, to the genus Aeneator Finlay 1926, typified by the species A. marshalli marshalli (Murdoch, 1924) recorded from Castlecliff (as fossils) and, as a recent species (= A. marshalli separabilis Dell, 1956), from Wanganui and Ohope beach, Whakatane, New Zealand. Similar to the type species, A. martae sp. n. has a fusiform shell with moderately tall spire, shallow sinus in outer lip and a spiral sculpture of cords crossed by axial costae (Beu and Maxwell 1990). The new species differs from A. marshalli in its smaller shell, shorter anterior canal, the absence of nodules along the columellar lip, less inflated whorls and by the presence of a distinct keel at the periphery. From the genus Austrofusus Kobelt, 1879, with the type species Austrofusus glans (Röding, 1798), the new species differs in the smaller size, its thicker shell, more prominent sculpture, the more prominent ridges over the periphery, and the pale orange colour of the aperture, which is white in A. glans (Beu & Marshall 2010). Comparative characters in the Chilean species of Aeneator are compared in table 2.
In a recent revision of the fossil fauna of Mejillones, north of Chile (Nielsen 2012), the species Aeneator loisae was synonymized with the fossil species Fusus steinmanni Möricke, 1896 into Austrofusus. However, this was based partly on the incorrect conclusion by Beu and Marshall (2010) that A. fontainei is the type species of Austrofusus; this was later corrected by Beu and Marshall (2011). On morphological grounds, the author concurs with McLean and Andrade (1982) and considers that Aeneator (Ellicea) loisae does belong to the genus Aeneator and the sub-genus Ellicea Finlay in Marwick, 1928. However the generic placement of the species A. fontainei, A. castillai, and possibly the new species described here, should be further investigated or even be ascribed to a new genus.
Further study of radular characters, comparative anatomy and DNA will improve the taxonomic placement of the Chilean species. Fossil studies would also give a general insight into the development of the genus and their relationships with the South Pacific related fauna, especially those from New Zealand and adjacent waters.