Gouldipoma terecostatum ( Thompson, 1966 )

Watters, G. Thomas, 2014, A revision of the Annulariidae of Central America (Gastropoda: Littorinoidea), Zootaxa 3878 (4), pp. 301-350 : 321-322

Gouldipoma terecostatum ( Thompson, 1966)

Figure 5 M – P, 12 D

Type material. UMMZ 216554, holotype (fig. 5 M); UMMZ 216555 (6), paratypes; UMMZ 216556 (1), paratype; UF 29313 (1), paratype (figs. 5 N, P); USNM 669201 (1), paratype; ANSP 305061 (1), paratype; MCZ 260881 (1), paratype; P: Museo Nacional de México, unnumbered (1), paratype.

Type locality. “ limestone hillside 15.8 miles [25.4 km] northwest of Ocozocoautla, Chiapas, 2700 ft. [823 m] alt.”

Type figured. Thompson, 1966: figs. 1, 5, 7.

Chresonymy.

Choanopoma terecostatum Thompson, 1966: 24 – 28, figs. 1, 5 [operculum], 7; Richardson et al., 1991: 43.

Halotudora terecostata ( Thompson, 1966) . Watters, 2006: 73, 506.

Choanopoma (Choanopomops) terecostatum Thompson, 1966 . Thompson, 2011: 47, 285.

Distribution and habitat. This species is only known from northwest of Ocozocoautla de Espinosa, Chiapas State at ca. 800+ m altitude. Specimens were collected on a limestone hillside.

Conservation. The range of this species may be nearly completely contained in the Parque Natural El Ocote.

Other material (specimens examined: 1). Paratype UF 29313.

Description. Little needs to be added to Thompson’s original description (below) except to mention the lavender ring of color behind the peristome of some individuals. Specimen size ranges from 12.0 – 13.1 mm. Radula and anatomy unknown.

Variation in specimens. Only the holotype and a paratype seen, which differ only in the intensity of the base color.

Comparison with other species. As mentioned by Thompson (1966), this species is “nearly identical” to Parachondria rubicundus . It occurs on the western edge of P. rubicundus ’s range. As Thompson stated, the two are easily differentiated by their opercula: P. rubicundus lacks the calcareous lamella found in G. terecostatum . Unfortunately, the great majority of specimens encountered are dead shells lacking opercula. However, there are several other criteria to discern the two species: G. terecostatum lacks the spiral cords usually found in the umbilicus of P. rubicundus and P. rubicundus tends to retain the protoconch as an adult whereas it is usually lost in G. terecostatum . Exceptions occur and it is entirely possible that specimens may be misidentified in collections. It is of interest to note that a similar case occurs in the Lesser Antillean annulariids where Diplopoma decussatum (Lamarck, 1822) and Parachondria lineolatus (Lamarck, 1822) are virtually indistinguishable without the operculum.

Gouldipoma terecostatum also resembles G. coltrorum , which also has a pigmented ring behind the peristome. Gouldipoma terecostatum lacks the spiral sculpture of G. c o l t ro r u m.

Remarks. Despite the potential problems of confusing this species with C. rubicundum , this appears to be a very rarely seen snail.

Original description: “Shell conical, 0.53 – 0.60 times as wide as long. Shiny; light orange in color with vague alternating light and dark zones; slightly darker on upper whorls. Peristome and aperture same color as rest of shell. Shell with 4 faint, narrow, broken rose-colored bands which may be indistinct in old specimens; upper 2 bands located near periphery of whorls and visible through length of shell; lower 2 bands evident only on base of last whorl. Decollate, 4.2 – 4.7 whorls remaining. About 2.0 – 2.5 juvenile whorls lost in adult shells. Apical plug purplish, sloping, about ¼ whorl long. Suture deeply impressed. Whorls strongly inflated; supraperipheral area moderately curved, sloping, not shouldered; peripheral and subperipheral area more strongly rounded. Umbilicus about 1/5 – 1/6 diameter of shell. Aperture adnate to preceding whorl; broadly ovate, 1.07 – 1.16 times as high as wide; 0.34 – 0.36 times length of decollate shell. Inner peristome not extended; demarcated only as a strong annulation on lip. Outer peristome strongly expanded; about 0.5 – 0.8 mm. wide or about 1/5 – 1/7 width of aperture; widest at upper corner, which is vertical and not deflected. Outer peristome constricted in parietal region and only slightly flexed forward. Sculpture of adult shell consisting of smooth, uniformly spaced axial ribs that are slightly oblique and weakly recurved. Five – six ribs per mm. on body whorl; slightly more crowded on early whorls. Ribs of uniform intensity from suture to umbilicus, where they become reduced to sharp threads. Spiral sculpture absent. Two embryonic whorls (lost from adult shells) smooth.

Operculum flat, consisting of about 3.5 rapidly expanding whorls. Nucleus acentric. Calcareous lamella broadly reflected over basal chondroid plate and nearly covering latter. Reflected lamella parallel to chondroid plate and supported by numerous narrow calcareous buttresses and ribs that parallel growth striations. Lamellae of adjacent whorls separate.”

Etymology. L. teres, smooth + L. costatus, ribbed—smoothly ribbed.

Figures

FIGURE 5 A – L. Gouldipoma coltrorum new species. A – B. UF 479664, holotype, 13.8 mm. C – D. UF 479665, paratype, 11.4 mm. E – F. UF 479665, paratype, 11.4 mm. G – H. UF 479665, paratype, 11.3 mm. I – J. UF 213711, 11.3 mm. K – L. UF 13711, 10.6 mm. FIGURE 5 M – P. Gouldipoma terecostatum (Thompson, 1966). M. UMMZ 216554, holotype, 12.4 mm, photo courtesy of Taehwan Lee, UMMZ. N – P. UF 29313, paratype, 13.6 mm and operculum.