A review of the non-bulimulid terrestrial Mollusca from the Region of Atacama, northern Chile

Abstract Terrestrial mollusca are sparsely studied in Chile and, for the first time, a formal record of the diversity of land snails in northern Chile is reported. Coastal and desertic areas in the Region of Atacama, in the border of the Atacama desert and the Pacific Ocean, were surveyed with the aim to describe the presence and distribution of this poorly known fauna. Of the fourteen species recorded, the geographic distribution records for nine species are extended, and some taxa are recorded for the first time since their original descriptions. All, except one, of the fourteen terrestrial molluscan species occurring in the area are endemic to Chile; they are all terrestrial species, most of them have a restricted geographic distribution, and none of them is currently protected by law. The results reveal that the region of Atacama has one of the most diverse terrestrial snail biodiversity in Chile, ranking only after the Juan Fernandez Archipelago. Distribution records of all the studied species and a taxonomic key are also provided.


Introduction
Terrestrial molluscs are one of the least studied invertebrate groups in Chile, the first work compiling the records of land molluscan species is still extant (Stuardo and Vega 1985). Just a few subsequent studies have reviewed genera or families (Valdovinos andStuardo 1988, Stuardo andVargas-Almonacid 2000) or described new species, all of them micromolluscs (Vargas-Almonacid 2000, Vargas and Stuardo 2007, Miquel and Barker 2009, Miquel and Cádiz-Lorca 2009, Miquel and Araya 2013. Studies considering species from northern Chile have been very scarce, like the work of Rehder (1945), which reviewed the subgenus Peronaeus and the work of Valdovinos and Stuardo (1988), reviewing the genus Plectostylus in Chile.
This work presents an overview, with distributions and illustrations, of all the land molluscan species found in the Region of Atacama, northern Chile. Ellobiidae species are also included, taking into account their terrestrial habitat in the country. The distribution range and a taxonomic key to all the studied taxa is also provided. The aim of this preliminary paper is thus to contribute to the knowledge of the land snail fauna in Chile.

Methods
Most of the sampling was made in the coastal desert areas around the port of Caldera (27°04'S, 70°50'W), and in specific localities in the Region of Atacama, northern Chile, during the summers of 2009 to 2012 and in August-December 2012. This region occupies the southern part of the Atacama desert and has an arid to hyper-arid climate, with low precipitation, mostly associated with the El Niño Southern Oscillation (ENSO) events. Detailed descriptions of the surveyed area, particularly of the flora and higher fauna are provided in Squeo et al. (2008). A synopsis of all the localities is given in Table 1. The surveys used a similar approach like Cowie and Robinson (2003) by also collecting litter for further sorting in the laboratory. The terminology of shell morphology is based upon Breure (1979). Original descriptions of all species were carefully reviewed, and the references included in the synonymies are mostly the ones that contained detailed descriptions or figures. Dimensions of the shells, measured with Vernier callipers (± 0.1 mm) are depicted in the Figure 1. Abbreviations used for repositories of material are: JFA-LG, private collection of the author section land Gastropoda, Santiago, Chile; MZUC, Museo de Zoología de la Universidad de Concepción, Concepción, Chile; RMNH.MOL, Naturalis Biodiversity Centre, The Netherlands, Mollusca collection; RCG, private collection of Ricardo Catalán, Sernapesca, Caldera, Chile.
The genus is extant and distributed in Chile and Argentina, its type species is endemic to Chile. All the species have a minutely rugose, granulate or striate protoconch.  and Stuardo 1988). This species was moderately abundant in the area, living in sand near cacti, and in rocky outcrops. Distribution and remarks. Huasco (28°20'S, 71°15'W) (Valdovinos and Stuardo 1988). This is the northernmost record for the species. This species is easily distin- guished from P. broderipii due to the conspicuous rimate umbilicus, the more globose whorls, stouter shell and shorter spire. (Pfeiffer, 1842) http://species-id.net/wiki/Plectostylus_elegans Figs 3.10-3.14,
Distribution and remarks. Huasco (28°20'S, 71°15'W) (Valdovinos and Stuardo 1988). The specimens here studied constitute the northernmost record for this species. Breure and Ablett (2012) synonymized this species as P. broderipii. However, the shells here examined were much lighter, thinner and broader than P. broderipii. Shell patterns, which are contained in the thin outer shell layer, can easily differenciate P. elegans from P. broderipii in having axially marked reddish-brown lines, even in juvenile specimens. Only extensive comparative anatomy, including soft parts as well as shell morphology, would certainly help to establish its true identity.

Plectostylus moestai (Dunker, 1864)
http://species-id.net/wiki/Plectostylus_moestai  (Pilsbry 1897). Valdovinos and Stuardo (1988), in their review of the genus, could no locate specimens of this species. Although this species has been cited for the area, searches at the type locality were unsuccessful. This may represent an extinct taxon. Diagnosis. This elongated Plectostylus species has a thin and somewhat fusiform shell, with an acute, long spire and five slightly convex whorls, sculptured with minute granules and growth lines. The aperture is narrow and descending, somewhat expanded in the anterior side. Periostracum is thin, opaque and yellowish.
Distribution and remarks. Valdovinos and Stuardo (1988)  Diagnosis. This relatively large species (up to 52 mm) has a thin but stout shell, with an acute, somewhat short spire and five slightly convex whorls sculptured by thin growth lines and fine spiral threads. The aperture is large, oval and slightly angulated in the columellar lip, which is completely white in its anterior part.
Distribution and remarks. Valdovinos and Stuardo (1988) cited this species from Paposo (25°05'S, 70°25'W) to Lomas de Huasco (28°20'S, 71°15'W). According to Breure and Ablett (2012) this species is a subjective synonym of P. broderipii. The specimens here examined seem slightly different; the shells are more elongated, with a larger aperture and a more acute spire. Some specimens have rimate shells, with a pseudo-umbilicus formed by the folding of the columellar lip. These specimens have a thin, opaque, persistent and delicate brownish periostracum. Diagnosis. This species has a tiny (largest specimen: 3.1 mm width), orbicular, low-spired shell, sculptured by numerous axial lamellae (about 90-95 in last whorl), with a depressed apex, a thin and brownish periostracum and an ample umbilicus. Live animals are unknown.
Distribution and remarks. According to Miquel and Araya (2013) this species has a patchy distribution, having been found only in the vicinites of the port of Caldera, Region of Atacama, Chile.
The genus is extant and distributed in South Africa, New Zealand and Chile, its type species is found from Ecuador to Chile.

Marinula pepita King, 1832
http://species-id.net/wiki/Marinula_pepita Table 2 Marinula pepita King,1832: 344;Keen 1971:850, fig Diagnosis. This species have small shells (up to about 11 mm), brownish or reddish in colour, higher than wider, of short spire, a large last whorl and an impressed suture. Aperture is simple, with a thin lip with a tooth in the inner external lip and three more in the columellar area. Animals are traslucent, with darker tentacles and a comparatively short foot.
Distribution and remarks. This species has been cited from Coquimbo to Chiloé Island, Chile (Keen 1971), and in Lima, Peru (Paredes et al. 2005). The specimens here examined constitute the northernmost record of this species in Chile. It has been found that this species feeds on remains of birds, fishes and sea urchins (Paredes et al. 2005).
The genus and its type species are extant and distributed in Chile and Peru.

Sarnia frumentum (Petit de Saussaye, 1842)
http://species-id.net/wiki/Sarnia_frumentum Diagnosis. This is one of the smallest terrestrial snails found in northern Chile. They have small (up to about 7 mm) whitish-orangish shells, of subcylindrical shape, with a simple and sharp aperture, with three plyes in the columellar side.
Distribution and remarks. This species has been cited from El Callao, Peru to Chañaral, Chile (Paredes et al. 2005). This is the southernmost record for this species in Chile. It has been found that this species feeds on remains of birds, fishes and sea urchins (Paredes et al. 2005).
The subgenus is extant and distributed in USA, northern Mexico, Cuba and Chile, its type species is restricted to southern USA.
Distribution and remarks. Paposo to La Serena (Stuardo and Vargas-Almonacid 2000). Here the species seem to be narrowly distributed, with small but abundant communities found in elevated rocky areas facing the Pacific Ocean.
The genus and type species are extant and endemic to Chile; protoconchs of all species of the genus have a characteristic spiral striation.  Diagnosis. This species have small (up to 23 mm), pale brown, thin ovate-oblong shells, minutely sculptured by fine spiral lines, with a reflexed and delicate thin lip and a comparatively large protoconch decorated by spiral threads. This is the smallest species in the Strophocheilidae.

Chiliborus pachychilus
Distribution and remarks. Questa de Arenas, Huasco (28°20'S, 71°15'W) and Coquimbo (29°57'S, 71°20'W) (Stuardo and Vega 1985). The specimens studied here constitute the northernmost record for the species.  Diagnosis. This species has large (up to 89 mm in examined specimens), brownish and elongate shells decorated with growth lines. Shells have crenulated sutures, a large protoconch and a thick lip. Animals have an orange or brownish body, with short grey tentacles.
Distribution and remarks. From Huasco to Chiloé Island (42° S, 73° W) (Stuardo and Vega 1985). This is the northernmost record for the species.
Distribution and remarks. According to Valdovinos (1999) this species has records in Chile from La Serena (29°54'S, 71°15'W) to the Chiloé Island, and the Juan Fernandez Archipelago (33°38'S, 78°84'W). This is the northernmost record of this species in Chile and it is the only introduced land snail species found in the area.

Conclusions
The terrestrial molluscs found in the Region of Atacama encompasses five families: Bothriembryontidae, a Gondwanan family which in Chile is solely represented by the genus Plectostylus; Charopidae, a widely extended family of tiny snails; Ellobiidae, a family which includes conspicuous terrestrial species living in litoral areas, in mangroves and under rocks in salty conditions; Strophocheilidae, with conspicuously large snails and Bulimulidae, with 29 species in Chile, all in genus Bostryx. This last family is currently under study, with twenty three species represented in the Region of Atacama, and will be reviewed in a further work. Most of the species here considered occur in patchy distributions along the coastal desert of northern Chile, most of them with sparse records and very few have been found alive.
In summary, fourteen species of terrestrial molluscs are recorded in the Region of Atacama. All of them are ground dwellers, and only one introduced species, Cornu aspersum, has been found in the residential gardens of Caldera. Chiliborus bridgesii, C. pachychilus, C. rosaceus, C. aspersum, Marinula pepita, Plectostylus coturnix, P. elegans, P. variegatus and Sarnia frumentum are recorded from the Atacama region for the first time and thus they extend their distribution records in the country. Taking into account the twenty three species of Bulimulidae, which will be reviewed in another work, the number of species recorded in the region of Atacama make it one of the richest places in Chile in terms of terrestrial molluscan biodiversity. Intensive collections are needed for a further understanding of the biology and ecology of this group.