Ammonicera mexicana, 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 : 10-12

Ammonicera mexicana sp. nov.

Figure 6

Examined material (24 specimens). Holotype: LACM 3286 ( SEM, color photograph before 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 [4.6–19.8 m], leg. James H. McLean & Peter Oringer, 13–21 October 1968 . Paratypes (3): LACM 3287 (Paratypes 1, 2; SEM), from the holotype lot ; FMNH 339462 (Paratype 3; SEM), from the holotype lot . Additional material: LACM 68-41 , 7 specimens from type locality ; LACM 71-83 , 9 specimens, 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 65–28 , 1 specimen, Barra de Navidad , Jalisco, West coast of Mexico, 19°20’N, 105°W, 5–20ft [1.5–6.1m], leg. Nick Furjanick, 26 June 1965 ; LACM 67-9 , 1 specimen, Isla Isabela , 45 miles northwest of San Blas, Nayarit, West coast of Mexico, 21°51’N, 105°55’W, 30ft [9.1m], leg. Chuck Snell & Bob McMillen, 11 February 1967 ; LACM 67-155 , 2 specimens, Isla Roqueta , Acapulco de Juaréz, Guerrero, West coast of Mexico, 16°49’N, 99°56’W, 15–20 ft [4.5–6.1m], leg. Twila Bratcher, 10 May 1967 .

Diagnosis. Ammonicera with spiral cords delimiting a keeled peripheral wall; additionally sculptured by a single row of 14–20 nodules each on the apical and basal walls of the body whorl.

Description. Shell planispiral, tightly coiled. Shell wall very thin, pellucid, glossy, amber in coloration. Protoconch of c. 1.4 whorls, with the first whorl sculptured on its apical and basal surfaces by 3 spiral cords; inner spiral cord positioned approximately mid-whorl, broad, prominent; central and outer spiral cords approximately equidistantly distributed between the inner cord and the outer suture; central cord c. 1/4 the width and height of the inner cord; outer cord c. 1/2 the width and equivalent in height to the central cord; surface of the protoconch finely pitted between inner suture and inner spiral cord, and with a reticulate sculpture between inner spiral cord and outer suture; sculpture of the protoconch transitioning to large nodules positioned mid-whorl along approximately the last 1/2 whorl. Protoconch 2 stage absent; boundary between protoconch and teleoconch poorly marked. Teleoconch of c. 1.4 whorls, sculptured by 1 broad and prominent spiral cord at the shell periphery and on both the apical and basal surfaces by 1 similar spiral cord each at the junction with the peripheral wall; apical and basal surfaces additionally sculptured by 1 spiral row of axially elongated nodules, positioned in the inner half of each whorl, with interspaces c. 1–3 times their width, gradually increasing in height throughout the teleoconch; body whorl with 14–20 nodules; secondary sculpture of the teleoconch composed of very fine and somewhat wavy spiral grooves. Apical and umbilical sutures shallowly impressed; outer lip convex in the vicinity of the sutures, straight along each of 4 segments between obtuse vertices corresponding to the 3 continuous spiral cords and 2 nodulose spiral cords of the teleoconch; inner lip concave, not flaring. Aperture almost hexagonal.

Shell dimensions (in mm) and whorl counts:

Remarks. Ammonicera mexicana appears to be closely related to A. mcleani , from which it differs in having a keeled periphery, a more discoidal shape and slightly less prominent nodules. Criteria to distinguish Ammonicera mexicana from seemingly more distantly related look-alikes were discussed under the remarks for A. mcleani .

Etymology. Mexicanus-a-um, adjective; from Mexico.

Figures

FIGURE 6. Ammonicera mexicana sp. nov. A–C. Holotype, apical views; A. General view; B. Detail of the protoconch (interpreted boundary between protoconch and teleoconch at arrowhead); C. Coloration; D–E. Paratype 1, umbilical views; D. General view; E. Detail of the protoconch; F. Paratype 2, dorsal view; G. Paratype 3, apertural view. Scale bars: A, C, D, F, G = 0.2 mm; B, E = 0.1 mm.