Paradoxipoma enigmaticum, Watters, G. Thomas, 2014

Watters, G. Thomas, 2014, A revision of the Annulariidae of Central America (Gastropoda: Littorinoidea), Zootaxa 3878 (4), pp. 301-350 : 332

Paradoxipoma enigmaticum new species

Figures 8 A–E , 12 A

Type material. UF 479320, holotype (figs. 8 A, B); UF 479321 (3), paratypes (figs. 8 C, D), from type locality; UF 479322 (1), paratype (fig. 8 E), Rockville Quarry, Gracy Rock Hill.

Type locality. Limestone hill on south side of Sibun River at Cedar Banks, Belize District, Belize, 50 m.

Distribution and habitat. Known only from limestone outcrops in the vicinity of Gracy Rock Hill in Belize District, Belize, at ca. 50 m elevation. These limestone knolls extend south of the type locality for ca. 8 km.

Conservation. None of the localities are protected; one of the two known sites is a quarry.

Other material (specimens examined: 172). Belize. Belize District: UF 207315 (83), Rockville Quarry, Gracy Rock Hill; UF 207514 (89), limestone hill on south side of Sibun River at Cedar Banks, 50 m.

Description. Shell conic, turbinate, thin, translucent, adnate. Largest adult specimen seen 9.6 mm (nondecollate). Protoconch retained in adult, 1.5 whorls, smooth, prominent, flattened, dark brown or tan with a dark top, demarcation between protoconch and teleoconch very indistinct. Teleoconch of 3.5 rounded whorls with a blunt angle at the level of the juncture with the peristome. Umbilicus wide, open. Spiral sculpture of ca. 17 low threads, distantly spaced below suture, becoming progressively closer together towards the angle; the threads abruptly end at the angle and are absent on the base except for very faint signs of a few cords in the umbilicus. Axial sculpture of numerous very fine, very closely spaced lamellae. Intersections of axial and spiral sculpture minutely beaded or fenestrated. Suture strongly indented, smooth. Aperture somewhat triangular. Inner lip absent. Outer lip very narrow, reflection scarcely apparent, adnate with previous whorl. Base color dingy white or tan, earlier whorls often more darkly colored than last whorl. Many specimens show varying degrees of tan spiral banding composed of three bands above the angulation and one or two below; bands often broken into dots or dashes; bands visible in aperture and on outer lip. Opercula known from only two specimens, both incomplete, but having the remains of a multispiral, narrow, calcareous lamella with a broad sulcus between the whorls. Radula and anatomy unknown.

Variation in specimens. Specimens vary primarily in the intensity of the color pattern.

Comparison with other species. Specimens resemble juvenile individuals of other species. The angular whorls and lack of spiral sculpture on the base characterize this species.

Remarks. This species seems to be narrowly endemic to a series of limestone knolls that occupy ca. 50 km 2. It co-occurs with H. gruneri and H. kuesteri but is clearly distinguishable from juveniles of those species.

Etymology. L. aenigma, inexplicable, mystery.

Figures

FIGURE 8 A – E. Paradoxipoma enigmaticum new species. A – B. UF 479320, holotype, 9.4 mm. C. UF 479320, paratype, 8.3 mm. D. UF 479320, paratype, 7.7 mm. E. UF 479322, paratype, 8.4 mm, detail of operculum. FIGURE 8 F – K. Diplopoma osberti (Tristram, 1861). F. Fischer & Crosse, 1890: pl. 42, figs. 13, 13 a, 13 b. G. UF 190089, 11.4 mm. H. UF 190089, 9.8 mm. I. UF 190089, 9.5 mm. J. UF 190061, 10.9 mm. K. GTW 16017 a, 10.1 mm. FIGURE 8 L – W. Diplopoma rigidulum (Morelet, 1851). L. NHMUK 1893.2. 4.705, syntype, ca. 12 mm, photo courtesy J. Ablett (NHMUK). M – N. UF 155790, 8.8 mm. O. GTW 8731 a, 9.7 mm. P. Grego coll., 9.5 mm. Q. GTW 8713 c, 9.5 mm. R. GTW 8731 e, 9.1 mm. S. UF 15813, 6.4 mm. T. GTW 8713 g, 9.4 mm. U. UF 146240, 9.3 mm. V. UF 135055, 8.6 mm. W. UF 207341, 9.6 mm.

FIGURE 12 A – D. Distribution maps. A. Choanopomops largillierti (Pfeiffer, 1846) (black); Parachondria rubicundus (Morelet, 1849) (red); Parachondria cordovanus Pfeiffer, 1857 (blue); Paridoxipoma enigmaticum new species (white). B. Halotudora sumichrasti (Crosse & Fischer, 1874) (blue); Halotudora gaigei (Bequaert & Clench, 1931) (black); Diplopoma osberti (Tristram, 1861) (red); Halotudora gruneri (Pfeiffer, 1846) (white). C. Gouldipoma chiapasense (Crosse & Fischer, 1877) (red); Diplopoma rigidulum (Morelet, 1851) (black); Tudorisca andrewsae (Ancey, 1886) (blue); Gouldipoma coltrorum new species (white); Gouldipoma thomasi (Solem, 1961) (purple). D. Gouldipoma trochlearis (Pfeiffer, 1852) (red); Halotudora kuesteri (Pfeiffer, 1852) (black); Gouldipoma terecostatum (Thompson, 1966) (blue); Gouldipoma chrysostiria new species (purple); Gouldipoma callipeplum (Solem, 1961) (white).