Ammonicera sucina ( Laseron, 1954 )

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 : 4-6

Ammonicera sucina ( Laseron, 1954)

Figure 3

Helisalia sucina Laseron, 1954, p. 17 , figs 47,47a.

Ammonicera sucina ( Laseron, 1954) — Ponder & de Keyzer, 1998, p. 864, fig. 15.185 A, C.

Examined material (12 specimens). LACM 79-58 , 11 specimens (4 under SEM, one previously lightphotographed), rocky substrate, Long Reef , Sydney, New South Wales, Australia, 33°44.5’S, 151°19.2’E, intertidal, leg. James H. McLean, 13 May 1979 ; FMNH 339459 , 1 specimen, same collection data as LACM 79- 58 .

Type locality. North Harbour , New South Wales, Australia .

Diagnosis. Ammonicera with a conspicuous spiral groove and a faint spiral cord on the protoconch; teleoconch sculptured by weak axial ribs and by a spiral sculpture of broad, elongated pits interspersed with raised nodules; spiral sculpture fading out on the body whorl.

Description. Shell planispiral, tightly coiled. Shell wall very thin, pellucid, glossy, amber in coloration. Protoconch of c. 1.2 whorls, finely pitted, sculptured on its apical and basal surfaces by a faint spiral cord midwhorl and a broad spiral groove positioned equidistantly between the cord and the outer suture. Boundary between P1 and P2 poorly marked to indistinct; boundary between protoconch and teleoconch marked by interruption of the spiral grooves and onset of the axial sculpture of the teleoconch. Teleoconch of c. 2 whorls, with an axial sculpture of weak ribs; spiral groove of the protoconch replaced on the first 1.5 whorls of the teleoconch by a primary spiral sculpture of broad, elongated pits interspersed with raised nodules, the latter positioned at intersections with the axial ribs; primary spiral sculpture fading out on the last 1/2 whorl of the teleoconch. Secondary spiral sculpture of the teleoconch composed of numerous very fine lirae, with interspaces approximately matching their width, occurring on both apical and basal surfaces from mid-whorl to the shell periphery. Shell periphery transitioning from obtusely angled along the first 1.5 whorls of the teleoconch to uniformly rounded subsequently. Apical and umbilical sutures impressed; outer lip sharply convex in the vicinity of the sutures, straight to broadly convex along apical and basal walls, uniformly rounded along periphery; inner lip concave, flaring slightly. Aperture subcrescent.

Shell dimensions (in mm) and whorl counts:

Remarks. The original description and illustrations of Helisalia sucina by Laseron (1954), who tentatively assigned this species to the family Liotiidae Gray, 1850 , were based on light microscopy alone and are insufficiently detailed. Ponder & de Keyzer (1998) recognised this species as a member of Ammonicera and published the first SEM image of the shell in apical view, as well as a sketch of the live animal. The redescription presented herein is based on SEM micrographs of shells collected c. 10 km north of the type locality.

A. sucina shares with A. plicata Sleurs, 1985b , which is only known from its type locality in the Maldives, a similar sculptural pattern, but differs from the latter species in several aspects: (1) the shell periphery is obtusely angled in A. sucina , rather than uniformly rounded (compare Figure 3E–F herein with fig. 7 in Sleurs, 1985b); (2) apical and basal walls are flattened in A. sucina , whereas they are uniformly rounded in A. plicata ; (3) A. sucina has a shallower apical suture; and (4) the spiral sculpture of the teleoconch fades out sooner in A. plicata (approximately from the beginning of the third shell whorl) than it does in A. sucina (from the second half of the third shell whorl).

A further related look-alike is the Atlantic A. lineofuscata Rolán, 1992b , which is readily distinguished from A. sucina by a more pronounced sculpture (see Rolán, 1992b, figs 22, 24, 25), and a colour pattern of three spiral brown bands (see Tunnell et al., 2010, p. 258).

Figures

FIGURE 3. Ammonicera sucina (Laseron, 1954) A–B. Specimen 1, apical views; A. General view; B. Detail of the protoconch (interpreted boundary between protoconch and teleoconch at arrowhead); C–D. Specimen 2, umbilical views; C. General view; D. Detail of the protoconch; E. Specimen 4, dorsal view; F. Specimen 5, apertural view; G. Specimen 3, apical view. Scale bars: A, C, E–G = 0.2 mm; B, D = 0.1 mm.