Ammonicera sleursi, Sartori & Bieler, 2014

Sartori, André F. & Bieler, Rüdiger, 2014, Three new species of Ammonicera from the Eastern Pacific coast of North America, with redescriptions and comments on other species of Omalogyridae (Gastropoda, Heterobranchia), Zootaxa 3872 (1), pp. 1-21 : 6-8

Ammonicera sleursi sp. nov.

Figure 4

Examined material (92 specimens). Holotype: LACM 3288 ( SEM), flood control channel, Mission Bay , San Diego Co., U.S.A., 32°45.5’N, 117°15.0’W, 5-8ft [1.5–2.4m], leg. James H. McLean & Patrick LaFollette, 15 August and 11 October 1971 . Paratypes (3): LACM 3289 (Paratypes 1, 3; SEM, Paratype 3 previously lightphotographed), from the holotype lot ; FMNH 339460 (Paratype 2; SEM), from the holotype lot . Additional material: LACM 71-101 , 9 specimens from the type locality . LACM 71-83 , 6 specimens ( SEM), Los Arcos , Banderas Bay, Jalisco, West coast of Mexico, 20°32’N, 105°19’W, intertidal to 15ft [4.6m], leg. James H. McLean & Jeff Margetts, 30 May to 1 June 1971 ; LACM 68-41 , 1 specimen ( SEM), south side of Bahia Cuastocomate (3 air miles NW of Barra de Navidad), Jalisco, Mexico, 19°13’45”N, 104°44’53”W, 15–65 ft [4.6–19.8m], leg. James H. McLean & Peter Oringer, 13–21 October 1968 ; LACM 71-14 , 66 specimens, east side of Punta Entrada at Sail Rock (north entrance to Magdalena Bay ), Baja California, Mexico (24°32.4’N, 112°04’W, 10–50 ft [3–15.2m], leg. James H. McLean, 30–31 January 1971; LACM 66-12 , 1 specimen, Cape San Lucas, Baja California, Mexico (22°8’N, 110°W, 25–100 ft [7.6–30.5m], leg. James H. McLean & Peter Oringer, 3–4 April 1966; LACM 71-183 , 5 specimens, Man of War Cove, Magdalena Bay, Baja California, Mexico (24°37.5’N, 112°7.5’W, intertidal to 35 ft [10.7 m], leg. James H. McLean & Patrick LaFollette, 31 October 1971.

Diagnosis. Ammonicera with a broad spiral cord ornamenting the protoconch and teleoconch, gradually fading out on the body whorl; shell diameter c. 0.6–0.7 mm at 3 whorls.

Description. Shell planispiral, tightly coiled. Shell wall very thin, pellucid, glossy, fawn in coloration. Protoconch of c. 1.4 whorls, sculptured with 1 broad spiral cord on its apical and 1 broad spiral cord on its basal surface; spiral cords closer to the outer than to the inner suture. Basal surface of the protoconch finely pitted. Protoconch 2 stage absent; boundary between protoconch and teleoconch conspicuous to poorly marked. Teleoconch of c. 1.8 whorls, with a primary spiral sculpture composed of 5 broad cords separated by 4 marked grooves; the 2 most central cords (1 apical and 1 basal) continuous with those of the protoconch; 1 additional cord positioned at the shell periphery and 2 cords (1 apical and 1 basal) subperipherally; grooves between cords c. 0.1- 0.75 the width of the central cords. Secondary spiral sculpture of the teleoconch composed of numerous very fine lirae, with interspaces approximately matching their width, overlaying the primary spiral sculpture. Spiral sculpture gradually fading out in the last 1/2 whorl of the teleoconch. Axial sculpture of the teleoconch composed of growth lines only, which become crowded in the last 1/4 whorl of the teleoconch. Apical and umbilical sutures impressed; outer lip sharply convex in the vicinity of the sutures, uniformly rounded along the apical, peripheral and basal walls; inner lip broadly concave, flaring slightly. Aperture and operculum rounded.

Shell dimensions (in mm) and whorl counts:

Remarks. A. sleursi is remarkably similar to A. lignea Palazzi, 1988 , an Eastern Atlantic species endemic to the Madeira Archipelago. They share weak axial sculpture and broad spiral ribs that fade out towards the aperture. However, the shell of A. sleursi is considerably smaller than that of A. lignea at the same whorl count. The holotype and paratype of A. lignea illustrated by Palazzi (1988, figs 8,18) measure c. 0.92 mm at 3.24 whorls, and 0.82 mm at 3.13 whorls, respectively [our measurements], and Segers et al. (2009, p. 488) illustrated a specimen of A. lignea measuring 0.8 mm at c. 2.94 whorls. In contrast, the largest known shell of A. sleursi is the holotype, which measures 0.70 mm at 3.21 whorls. Obviously, the geographic separation of A. sleursi and A. lignea is also relevant in recognising them as separate species.

A. sleursi is also similar to the Western Atlantic A. circumcirra Rolán, 1992b , recorded from Cuba (the type locality; see Rolán, 1992b) and from the Saint Peter and Saint Paul Archipelago, Brazil ( Lima et al., 2011). However, the sculpture of A. circumcirra is more prominent than that of A. sleursi , particularly in the presence of weak elevations formed by the intersection of axial ribs with spiral cords. Additionally, the sculpture of A. circumcirra appears to be persistent, rather than fading along the teleoconch ( Rolán, 1992b, fig. 23; Lima et al., 2011, fig. 5).

Mediterranean A. fischeriana Monterosato, 1869 differs from A. sleursi in displaying a colour pattern of three spiral brown bands and in having a more pronounced axial sculpture.

Etymology. This species is dedicated to Dr. Willy J. M. Sleurs, Research Associate of the Royal Belgian Institute of Natural Sciences, in recognition of his contribution to our knowledge of Indo-Pacific omalogyrids.

Figures

FIGURE 4. Ammonicera sleursi sp. nov. A–B. Holotype, apical views; A. General view; B. Detail of the protoconch (interpreted boundary between protoconch and teleoconch at arrowhead); C–D. Paratype 1, umbilical views; C. General view; D. Detail of the protoconch; E and G. Paratype 3; E. Dorsal view; G. Apical view, showing coloration; F. Paratype 2, apertural view; H. Specimen from Los Arcos (LACM 71-83), apical view showing wide grooves between spiral cords. Scale bars: A, C, E–G = 0.2 mm; B, D, H = 0.1 mm.