New species of Gastrocopta from Argentina (Mollusca Eupulmonata Gastrocoptidae)

: The species of Gastrocopta here described share the angular lamella united with the parietal lamella at the inner end of the former, giving the shape of a “Y”. We describe two new species inhabiting the central and northern part of Argentina, and we report G. iheringi (Suter, 1900), which has the same structural feature, for the first time in the country. Present species of Gastrocopta live in Argentine temperate and tropical areas, but previous records indicate that the most ancient fossil record with such a characteristic anguloparietal lamella is from the Early Miocene of Santa Cruz Province (southern Patagonia).


INTRODUCTION
Argentina is situated in southern South America, with a surface of about 2.800.000 km². The country has a wide variety of biomes and soil types, including several arid, semiarid, wetland, forest and pasture areas. Many environments show marked degradation signs due to the advancement of human activities as agriculture, livestock, mining and forestry (Bertonatti & Corcuera, 2000).
The genus Gastrocopta Wollaston, 1878 has an almost worldwide distribution, except Europe. Most of the species in the genus inhabit in North America (Pilsbry, 1948;Bank, 2017). They are differentiated by shell morphology, in particular by the variety of apertural callous barriers, which are well developed only in fully grown specimens (Pokryszko, 1997;Miquel & Brito, 2019).
Gastrocopta has been scarcely studied in Argentina, where only eight recent species were reported during the last century, all of them from subtropical and temperate areas (Doering, 1879;Hylton Scott, 1945, 1948Miquel & Parent, 1996). Fossil species were studied from the Early Miocene of Santa Cruz province (Miquel & Rodriguez, 2015), Early Pliocene of Mendoza (Turazzini & Miquel, 2014), and Late Holocene of Entre Ríos (Miquel & Aguirre, 2011).
In this paper we describe two new species inhabiting the central and northern part of Argentina, and we report G. iheringi (Suter, 1900) for the first time in the country.

MATERIAL AND METHODS
The material studied here was collected in Argentina and southern Brazil, and is housed at the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (Buenos Aires) and Museo de La Plata (La Plata). The acronyms of these collections are MACN-In (Invertebrate Division, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"), MLP (Museo de La Plata) and MPM (Museo Regional Provincial "Padre Manuel Jesús Molina", Río Gallegos).
All the available specimens are adult shells. The methodology to study the apertural barriers follows Miquel & Brito (2019). The abbreviations used to identify the barriers are: apl: anguloparietal, ipl: infraparietal, cl: columellar, scl: subcolumellar, for lamellae; bf: basal, lpf: lower-palatal, upf: upper-palatal, for folds. After each description, a formula, e.g., [ap + c + sc/0] l + [b + lp + up] f, is given. Outside the first brackets an "l" indicates these are lamellae, while an "f" after the second brackets means folds. When a barrier may be either present or absent it is coded as sc/0. Shells were observed and measured under a stereoscopic microscopy; some specimens were coated with gold-palladium and imaged by Scanning Electronic Microscopy (MACN).
The species analyzed in this paper are members of the uncertainly defined group or subgenus Gastrocopta (Immersidens) Pilsbry & Vanatta, 1900, characterized by the angular lamella uniting to the parietal one at the inner end of the former, the two diverging forwards to shape together a Greek letter λ, or a reversed y. They also have two palatal folds, not standing on a callous ridge; the lower one is often deeply immersed (Pilsbry, 1948: 894). (Doering, 1879) ( Fig. 1) Pupa dicrodonta Doering, 1879: 83. Gastrocopta (Immersidens) dicrodonta: Pilsbry, 1916: 100;Parodiz, 1957: 129;Fernández, 1973: 31. Gastrocopta dicrodonta: Hylton Scott, 1948 Translation of the Latin original description by Pilsbry (1916: 100). "Shell minute, pupoid, smooth, substriatulate, a little shining, brownish-corneous. Spire subconical, the summit tapering, rather than obtuse. Whorls 5 ½ to 6, a little convex, the last about two-fifths the length. Aperture oval-rounded, with 5 (-6) teeth: the first, on the parietal wall, largest, twisted, bifid (forked or biramose), the right branch elon-gated to the margin of peristome, the other remote from the margin of the aperture; second tooth columella, tortuous, angulate, lengthened within, three pliciform palatal teeth. Peristome expanded, scarcely reflected, whitish, the margins nearly connected, right margin curved. Length 1.8 to 2, width 0.9 mm; aperture 0.7 to 0.8 mm. long". Type specimens and other materials. Unkown. Type locality. Originally recorded from Mendoza, Córdoba and San Luis provinces; Parodiz (1957: 129) tried to restrict it to Villavicencio (Mendoza) (Fig. 1), with no indication of analyzed materials. Remarks. The absence of either a type specimen or any original illustration hinders a comparison with other species. It is here considered a species inquirenda.

Gastrocopta dicrodonta
Gastrocopta iheringi (Suter, 1900) ( Remarks. Gastrocopta subandina n. sp. shows some morphological variations: while some shells have a cylindrical form, other ones have an oblong or conical form. Shells collected from Catamarca have an infraparietal lamella and a lower-palatal fold inside the peristome, a longer parietal lamella, and they lack a subcolumellar lamella. Comparisons. Gastrocopta subandina n. sp. is longer than G. maxbirabeni n. sp., and its apertural barriers are simpler than those of the lat-ter. Gastrocopta subandina has an anguloparietal lamella shorter than in G. iheringi and G. maxbirabeni, and does not have a concave and curved columellar lamella as G. maxbirabeni and G. iheringi do. Gastrocopta dicrodonta (Doering, 1879) is known to be smaller, pupoid, subconical, and differnt from Gastrocopta subandina (Pilsbry, 1916: 100). Some specimens of G. subandina have a subcolumellar lamella, which is absent in the other species described in this paper. Diagnosis. Shell pupoid, cylindrical or conical, with 5 or 6 apertural barriers: anguloparietal, infraparietal (sometimes absent) and columellar lamellae, and basal, lower-palatal and upperpalatal folds. Anguloparietal and columellar lamellae and the basal fold occupy a large space. Apertural barriers small with a columellar lamella slightly concave and oblique. Description. Shell pupoid, oblong or conical, light brown color, spire obtuse, not prominent, rimate, 4.5-5.25 convex whorls with growth lines very low but marked, oblique and irregularly parallel; the last whorl about 58% the total length; shallow suture. Peristome rounded square, reflected; 5 or 6 apertural barriers. Angular and parietal lamellae joined at base diverging forwards; parietal lamellae curved to the periphery, larger than the angular lamella; infraparietal lamella small, similar to a callus or tubercle, sometimes absent; columellar lamella concave, bent towards the parietal wall, sometimes very strong; basal fold sometimes strong, semicircular and slightly prolonged towards inside the peristome; lowerpalatal fold oblique, elongate, sometimes deeper in peristome than other folds; upper-palatal fold semicircular, elongate. Comparisons: Gastrocopta maxbirabeni n. sp. is shorter than G. subandina and it has stronger apertural barriers. These, mainly the anguloparietal and, sometimes, the columellar lamellae, occupy a large area of the aperture, which allow differentiate from G. subandina. Gastrocopta maxbirabeni is also distinct from G. iheringi as the new species is larger, with a smaller number of whorls; the latter has a longer anguloparietal lamellae. Some specimens of G. maxbirabeni have an infraparietal lamella, which is absent in other species described in this paper.

DISCUSSION
Recent specimens of Gastrocopta have been collected from humid areas of South America. Semiarid areas of the subandean region of Argentina are here added as new records. From a physiographical viewpoint, these areas are environmentally similar to those from which the genus was described from and mainly studied in North America (Pilsbry, 1948).
Gastrocopta iheringi is known from Brazil. Here, it is also recorded from the Corrientes Province (Argentina). The record for Santa Fe Province (Miquel & Parent, 1996) was erroneous (Salvador, 2021); the image of the specimen does not resemble G. iheringi but to an indeterminate species of Gastrocopta. Mentions of G. iheringi from Peru (Ramírez et al., 2003) and Venezuela (Thompson & López, 1996) need to be confirmed.
A comparison to the type series of Gastrocopta patagonica Miquel & Rodríguez, 2016, a fossil species from the late Early Miocene of the Santa Cruz Formation, is problematic because the paratype (MPM PI 3315) shows the characteristic anguloparietal lamella of the here analyzed species, while in the holotype (MPM PI 3314) this area is hidden by sediment (Miquel & Rodríguez, 2016 ("2015"): fig. 3.1-3.4).
Up to now specimens have been collected from only seven out of the 23 provinces of Argentina, in scattered localities far apart from each other. We therefore consider that the spread of this genus is still understated in the country, and many new localities could be added with a larger sampling.
Universytetu Wroclawskiego (Poland), for sending us Pokryszko's papers about the genus Gastrocopta; F. Tricárico for photographs taken at the Scanning Electronic Microscopy Service (MACN); C. Damborenea, head of the Invertebrate Division, and G. Darrigrán, head of the Mollusk Section at MLP, and A. Tablado, head of the Invertebrate Division at MACN, for allowing us to inspect the collections of these museums. The opinions expressed here are the responsibility of the authors. The authors be- The authors belongs to Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.