A new terrestrial snail species (Gastropoda: Bulimulidae) from the Región de Antofagasta, northern Chile

Material collection

Sixteen specimens, all of them empty shells, were collected buried in humus and under boulders and fallen rocks north of Paposo (24°55′S; 70°30′W, altitude 150–170 m; precise locality data available from first author on request), Región de Antofagasta, northern Chile (Figs. 1 and 2). The dimensions of the shells, measured with Vernier calipers (±0.1 mm) are depicted in Fig. 3; measurements are given in mm and include, when appropriate, the additional thickness of the lip. Type specimens are deposited in the collections of the Museo Paleontológico de Caldera (MPCCL), in Caldera, Chile and in the Santa Barbara Museum of Natural History (SBMNH) at Santa Barbara, USA. Field study permits were not required for this study and none of the species studied herein are currently under legal protection. The distribution map (Fig. 1) was prepared using SimpleMappr (Shorthouse, 2010).

Nomenclature

The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new name contained herein is available under that Code from the electronic edition of this article (ICZN, 1999; ICZN, 2008). This published work and the nomenclatural acts it contains have been registered in ZooBank, under the LSID urn:lsid:zoobank.org:pub:C9BE441E-6159-4973-888D-74660B2C25F3. The electronic edition of this work is available from the following digital repositories: PubMed Central, LOCKSS.

Systematic account

Diagnosis (Modified from Breure, 1979): Shell elongate-ovate to rather globose or depressed conical; (broadly) perforate; solid. Whitish to brownish in color, often with darker spiral bands, with axial streaks or coalescent spots in some species. Surface granulate or with incrassate growth striae. Protoconch pit-reticulate. Whorls slightly convex. Aperture (sub) ovate. Peristome more or less expanded. Columella in some species with a fold within the last whorl.

Type species Bulinus proteus Broderip, 1832

Diagnosis: A species with a medium sized thick and elongated shell (H to 25.5 mm), whitish or variegated in color, sculptured by growth lines and sometimes presenting shallow varices. The shell is mainly characterized by the subovate peristome with an expanded and reflexed outer lip, a narrow and deep umbilicus and by the presence of a columellar fold.

Description: Shell solid, of medium size (H up to 25.5 mm), elongated, fusiform; around 2.3 times as long as wide, rimate; upper whorls conic. Surface slightly shining; color white, corneous, or white with brownish axial streaks; sculptured by faint prosocline growth lines, crossed by minute and irregular spiral lines, forming a minutely reticulated surface in some areas. Irregular, longitudinal varices formed by old peristomes are occasionally found on the shell. Protoconch one and a half whorls, white to reddish-brown in color; smooth to the naked eye but actually sculptured with many small nodules and striations visible under microscope. Protoconch-teleoconch boundary well defined; teleoconch sculptured with fine growth lines and minor spiral lines better visible on earlier whorls; sculpture more distinct toward the umbilical area. Six and a half flat to slightly convex whorls; last whorl convex and slightly angulated, about 0.66–0.68 of total height. Sutures impressed but shallow. Aperture large (HA about 0.44–0.48 of H), subovate (around 1.50–1.54 times as long as wide), slightly oblique and prosocline (about 27°with columellar axis). Columellar margin short, dilated above, minutely rugose, with a columellar fold in the interior of its upper part. Terminations of peristome joined by a moderately thin, oblique, parietal callus. Outer lip expanded and reflexed, sharp, often with the internal margin thickened. Umbilicus narrow and very deep. Soft parts unknown.

Type material: Holotype MPCCL 020617 (Figs. 4A–4H): H: 24.8, HA: 10.6, LW: 16.6, NW: 7.5, SA: 47.5°, W: 10.7, WA: 7.3; paratype 1 MPCCL 030617A (Figs. 4J–4K): H: 25.3, HA: 12.4, LW: 16.8, NW: 7.5, SA: 50°, W: 11.2, WA: 8.1; paratype 2 (juvenile) MPCCL 030617B (Figs. 4L–4N): H: 18.1, HA: 9.4, LW: 12.9, NW: 7.0, SA: 59°, W: 9.2, WA: 6.2; paratype 3 (juvenile) MPCCL 030617C (Figs. 4O–4Q): H: 15.3, HA: 8.1, LW: 10.6, NW: 6.5, SA: 57°, W: 8.3, WA: 5.0; paratype 4 (juvenile) SBMNH 460094 (Figs. 5A–5D): H: 15.7, HA: 7.3, LW: 10.5, NW: 6.75, SA: 54°, W: 8.6, WA: 4.9; paratype 5 MPCCL 030617D (Fig. 4I): H: 25.4, HA: 12.6, LW: 17.2, NW: 7.5, SA: 47.67°, W: 11.2, WA: 8.1. All the specimens collected by M Araya and JF Araya, January 17, 2016.

Type locality: Foothills of the Chilean Coastal Range, north of Paposo (24°55′S; 70°30′W, altitude 150–170 m), Comuna de Taltal, Región de Antofagasta, northern Chile.

Distribution and habitat: Only known from type locality; shells found in humus under boulders and fallen rocks, usually near communities of the arborescent cacti Eulychnia iquiquensis, the large succulent shrub Euphorbia lactiflua and other small vegetation in the foothills of the Chilean Coastal Range. Many old shells and shell fragments were found buried in sediments in creeks and gullies, but no live specimens were recovered.

Etymology: A patronym (noun in apposition) in honor of the Chango people (now extinct) who inhabited coastal areas of northern Chile, having their last communities at Paposo, the type locality of the new species.

Remarks: Juvenile specimens have an obtusely angulated to almost carinated last whorl (Figs. 4L–4Q) and a rather narrow and slanted aperture (Figs. 4L and 5A), slightly semilunar in some specimens (Fig. 4O); the external lip becomes reflexed and expanded, and the columellar lip widens in more mature specimens (Fig. 4L), while in fully mature shells the peristome is almost continuous, with a large, expanded and reflexed outer lip and a thin columellar fold (Figs. 4A and 4J). Evidence of episodic growth is seen in the irregular varices found in several specimens; this characteristic is unseen in any other Chilean terrestrial mollusk.

Comparisons with related taxa: This species differs from all other species of Chilean terrestrial snails by its slender shell, a flared and reflected apertural lip and by the presence of a columellar fold, a feature so far unique among Chilean terrestrial species. At first glance, this new taxon resembles Scutalus latecolumellaris Preston, 1909, which was reported by Weyrauch (1967) from northern Peru at an elevation of 1,700 m. However, the size difference (25 vs. 54 mm) immediately distinguishes both species. All other Scutalus species are decidedly stouter and cannot be confused with the new species. The protoconch of the type specimen of S. latecolumellaris (see Breure & Ablett, 2014: 106) differs slightly from this new species: “the sculpture [of S. latecolumellaris] looks more pitted than the wave like sculpture [in S. chango]” (J Ablett, pers. comm., 2017). Also, the protoconch of specimens of S. proteus Broderip, 1832 in the Leiden museum are slightly more pitted than in the new species. Scutalus chango sp. n. corresponds with the Scutalus species from northern-central Peru in the ecology and the occurrence in the low-altitude coastal area. We have also compared this new species to members of Kuschelenia Hylton Scott, 1951, found in high-altitude Andean areas in Argentina, Bolivia, Ecuador and Peru (Hylton-Scott, 1951; Weyrauch, 1967; Breure, 1978; Breure, 1979; Miquel, 1998; Cuezzo, Miranda & Ovando, 2013). The protoconch in Kuschelenia species has (anastomosing) axial wrinkles (Breure, 1979: 87), which are more prominent than in S. chango sp. n. The whorls of the new species are more convex, and the peristome more expanded than those in Kuschelenia species. The gap in distribution between S. chango sp. n. and other Scutalus species (northern Chile versus central and northern Peru; Weyrauch, 1967; Breure, 1979) is larger than the distribution gap between the new species and the nearest Kuschelenia species (northern Chile versus the altiplano of Bolivia). It cannot be excluded a priori that the new species may turn out to be a low-altitude representative of this genus. Although this remains somewhat puzzling, this can only be resolved in the future with anatomical and molecular data. For the time being, we prefer to consider the new species as a member of Scutalus. Finally, the shell shape of S. chango sp. n. is reminiscent of some Drymaeus species; however, the lattice sculpture of the protoconch, with axial riblets and spiral sculpture in the latter genus is clearly different from the protoconch sculpture in this new species. Type localities and records housed at the Leiden Museum of Scutalus and Kuschelenia species are shown in Fig. 1.