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Species Catalogue of Orthalicoidea in Argentina (Gastropoda: Stylommatophora)
Abstract and Figures
We provide a catalogue of all available species nomina of Orthalicoidea occurring in Argentina. Ongoing taxonomic revisions on the genera Bostryx Troschel, 1847, Clessinia Doering, 1874, Pilsbrylia Hylton Scott, 1952, and Spixia Pilsbry & Vanatta, 1898, highlighted the necessity of an updated catalogue for the region. A total of 101 orthalicoidean species classified into four families, Bothriembryontidae, Bulimulidae, Odontostomidae and Simpulopsidae are present in Argentina. The catalogue provided here is based on examination of primary literature, available revisions and monographs, comparative studies within and among species and revision of museum data, including most type specimens. Additional collection of specimens in various localities of the country was carried out for more than a decade to be able to accurately state distributional information on the species treated. Nomenclatural details are provided for all nominal species. Name-bearing types were located for 86 species-group taxa, and six lectotypes were designated for the stabilization of the taxonomy. We propose the following nine new combinations: Bulimulus fourmiersi (d'Orbigny, 1835), Clessinia cordovana (Pfeiffer, 1855), Drymaeus flossdorfi (Holmberg, 1909), Cyclodontina (Ventanía) avellanedae (Doering, 1881), Simpulopsis (Eudioptus) eudioptus (Ihering in Pilsbry, 1897), Spixia champaquiana (Doering, 1875), S. charpentieri(Grateloup in Pfeiffer, 1850), S. minor (d'Orbigny, 1837) and S. parodizi (Hylton Scott, 1951). The following four new synonymies are proposed: Bostryx sophieae Breure, 1979, with Bulimus cordillerae (Strobel, 1874) (current name Bostryx cordillerae); Cyclodontina (Clessinia) gracilis Hylton Scott, 1956, with Bulimus cordovanus Pfeiffer, 1855 (current name Clessinia cordovana); Spixia estherae Fernández, 1971, with Odontostomus (Spixia) costellifer Hass, 1936 (current name Spixia costellifer); Kuschelenia simulans Hylton Scott, 1951, with Helix tupacii d'Orbigny, 1835 (current name Scutalus tupacii). Bulimulus sporadicus gracilis Hylton Scott, 1948, is changed from subspecific to specific status.
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... Particularmente en la República Argentina, esta familia es la más rica y filogenéticamente diversa . En el catálogo de los Orthalicoidea argentinos, Cuezzo et al. (2013) (Breure, 1979) y son consideradas de tamaño grande por tener una longitud total entre 20,01-40,00mm (Emberton, 1995). Originalmente fueron descriptas en base a la fuente de caracteres más ampliamente utilizada que es la morfología conquiolar. ...
... vesicalis, al mismo tiempo que colaborar en la diferenciación de especies y que de esta forma se contribuya a ampliar el conocimiento de Bulimulus. Para el desarrollo de la segunda parte de la tesis se eligió a B. bonariensis como especie modelo de estudio debido a que es la más ampliamente distribuida en la región este de nuestro país Cuezzo et al., 2013), por lo cual puede constituir una especie referente dentro de los Bulimulus de Argentina. De esta manera, la información obtenida de estudios poblacionales tales como tasa y modelo de crecimiento, mortalidad, tiempo de vida, sumado al análisis del desarrollo gamético y edad de la primera madurez sexual, nos permitirá contar con información fundamental a la hora de efectuar posibles controles a nivel poblacional o futuras comparaciones con otros representantes del género. ...
... A mediados del siglo XX, Parodiz (1944) re-describió a la especie conquiolarmente y puso de manifiesto la similitud de B. rushii con B. durus Spix, 1847, aunque la diferenció por algunos aspectos de la conchilla como tamaño y coloración, sumado a que la distribución de la última especie mencionada habita en Brasil. Aún Cuezzo et al. (2013), denotaron la similitud de la conchilla, protoconcha y destacaron la importancia de realizar futuros estudios de partes blandas. Parodiz (1944) también, destacó que la protoconcha de B. ...
Gastropods of the genus Bulimulus Leach, 1814 have a neotropical native distribution and are considered large in size because they measure between 20.01-40.00mm. The majority of its species were originally described based on their most widely used set of characters, conchological morphology. In some cases, information about the morphology of hard parts, such as the radula and jaw, was provided; however, data regarding their internal anatomy are scarce. Thus, of the 68 valid species of Bulimulus, according to the specialized database on molluscs, approximately 20% of the species have some anatomical data while; in terms of genetic approaches, only a few sequences corresponding to about 10% of the entities are currently available. As a result, for the majority of species, conchological characteristics are the only diagnostic tool available. Unfortunately, the length of the descriptions, the overlapping of conchological features, and the scarcity of anatomical information made it difficult to correctly identify numerous entities. The genus is represented in Argentina by eight species, three of which are found in the province of Buenos Aires.
Considering the on the one hand, B. bonariensis has little anatomical information, a wide distribution in the country, and has experienced population explosions with negative effects on crops on several occasions. And that, on the other hand, there is little or no anatomical information on B. rushii and B. vesicalis to complement the conchological data, as well as the fact that they were included on the list of priority species for conservation. Due to this, the objectives of this thesis are to conduct conchological and anatomical analyses with genetic support in order to complement the diagnosis of the species to contribute to elucidate certain confusing taxonomically situations as synonyms with other entities such as B. sporadicus and problems in the identification of specimens of B. rushii. On the other hand, this thesis focused on B. bonariensis to monitor an experimental population in order to gather information on its rate and pattern of growth, survival, mortality, age estimation and size at first reproduction, among other population parameters and characteristics of the life cycle. In addition to the analysis of gametic development, this study will provide us with valuable demographic information for conducting controls at the population level or comparisons with other members of the genus. Thus, using qualitative conchological analysis, we were able to identify specimens corresponding to the three species, with the sculptures of the protoconch being the most distinguishing feature of B. rushii, along with the length of the spire, length of the aperture, and general configuration, allowed the assignment of specimens to this species. As for B. vesicalis and B. bonariensis, the length of the spire, length of the aperture, and the low convexity of the whorls were the features that allowed such distinction.
In the morphometric analysis of the three species, a Principal Component Analysis (PCA) was first performed in order to explore the morphological variation of the shell shape, then the differences between the groups were deepened by means of a Discriminant Analysis (DA). In this way, the variables that allowed PCA discrimination were those associated with the penultimate whorl, length and width, and the smallest diameter. However, in the DA, the smallest diameter and the length of the spire were the variables of greatest contribution. Given the intraspecific morphological variability, morphometric tools were used to further analyze each species. Therefore, B. bonariensis displayed three distinct morphologies, with length penultimate whorl, the length spire, length total shell, length apertural, minor diameter and the largest diameter being the variables that contributed the most. B. vesicalis and B. bonariensis were qualitatively distinguishable from one another; yet, PCA and DA revealed a wide overlapping area. In B. rushii, variability at the conchological level was not observed within each population studied, but was found to be associated with geographic location. As a result, the length of the parietal space and aperture showed a significant difference in relation to altitude.
In terms of internal anatomy, differences that allowed complementing the diagnosis of each species were shown. At the level of the mantle organs, the location of the heart and pericardial cavity in relation to the kidney differed between the three species. In addition, B. rushii has a secondary collar vessel and a larger lung area. Regarding the digestive system, the main differences were observed in the buccal bulb, since B. rushii presented a greater number of muscles and a more quadrangular morphology of the jaw plates. On the other hand, there was only a subtle difference in the length of the cerebro-pleural connective tissue in the central nervous system between B. bonariensis and B. vesicalis, while in B. rushii there was extensive fusion of the pleural and pedial ganglia. There was also a significant difference at the reproductive level, which was considerably simpler compared to the other treated species, with a basic histological structure of the penial complex and no diverticula. When B. bonariensis and B. vesicalis were compared, differences in the thickness of the bursa copulatrix duct and the general and histological morphology of the penial complex were found. Moreover, when compared to samples from Buenos Aires, seven different penial complexes were present within the nominal species B. bonariensis. The molecular information through genetic distances, phylogenetic reconstructions and two species delimitation methods (ABGD and к/θ) allowed to consolidate what was observed from the anatomical point of view. So that, what was understood as a single species, is actually a complex of species formed by at least eight, which are considered cryptic based on the analysis of the conchological morphology.
Concerning the second part of the thesis, the laboratory study was carried out using B. bonariensis as the model species. In this way, it was possible to monitor a complete life cycle. The average number of eggs per clutch was calculated at 44, with a 14-day embryonic development time. The birth rate was nearly 42% and of this percentage, during the first 50 days mortality of 50% of the individuals born was observed. Thus, they presented a type III survival curve, with a high early mortality rate and a life expectancy of two to three years. The logistic growth model was the best fit. Through the histological study of the gonad, in a natural population and over the course of two years, biological peculiarities such as the location of the different cell types in the follicles could be identified. Furthermore, at the beginning of their development they are protogynous hermaphrodites and after reaching gonadal maturity, they become simultaneous hermaphrodites. It has also been determined that it is an iteroparous species. On the other hand, three reproductive periods were identified: pre-recruitment in the fall; recruitment, which begins in winter, but the main event occurs in spring; post-recruitment in summer, where the absence of gonadal rest was observed. In pre-recruitment resorption was observed in addition to abundant primary and secondary spermatocytes and growing vitellogenic oocytes. At the same time, it was possible to correlate the degree of spermoviduct development with the stage of gonadal development. By means of logistic regression, the size at which they reach gonadal maturity was calculated, which was established at 12 mm of total shell length. By relating this length with the laboratory study, it was possible to deduce that this size is reached after 200 days of life. Therefore, the first gametic maturation is achieved before one year of life, where a first decrease in the growth rate occurs. Finally, it was inferred that, since the reproductive period occurs the following spring, at one year of life during the recruitment period, the first reproduction takes place when they reach an average of 17 mm and there is a second decrease in the growth rate.
... The shells are morphologically similar to the members of family Cyclodontinidae (which was formerly part of Odontostomidae; see Salvador et al. 2023 for the revised classification within superfamily Orthalicoidea), in particular to members of genera such as Clessinia Doering, 1875 and Cyclodontina H. Beck, 1837. Thus, since its description, Pilsbrylia has been classified in that family (e.g., Hylton Scott 1952;Breure 1974;Fernández and Rumi 1980;Schileyko 1999;Cuezzo et al. 2013;Simone 2018). ...
The land snail genus Pilsbrylia Hylton Scott, 1952 has been recently shown to not belong to the superfamily to which it was originally assigned (i.e., the Orthalicoidea), instead pointing out a relationship with the Clausilioidea. In this study, we included the type species of the genus in a multi-marker molecular phylogenetic framework to reassess its family-level classification. Our results show that Pilsbrylia belongs to family Clausiliidae (known as ‘door snails’) and more specifically, to subfamily Peruiniinae. This family is unique among stylommatophorans for consisting almost exclusively of animals with sinistral (left-handed) shells, whilst Pilsbrylia has a “typical” dextral shell.
... The family Bulimulidae Tryon, 1867 comprises about 543 valid species (MolluscaBase, 2022) native to the tropics and subtropics of South America, Australia, New Zealand, Tasmania, and Africa (Breure, 1979;Herbert & Mitchell, 2009). Especially in the Argentine Republic, this family is the richest and most phylogenetically diverse, as it includes five genera with 46 species (Cuezzo, Miranda & Ovando, 2013;Miranda, 2014;Miranda & Cuezzo, 2014). Within Argentina, eight species in Bulimulus Leach, 1814 have been described, among which Bulimulus bonariensis is the most widely distributed, extending over twelve provinces: Buenos Aires, Chaco, Córdoba, Corrientes, Entre Ríos, Formosa, Jujuy, Misiones, Salta, Santiago del Estero, Santa Fe, and Tucumán (Miquel, 1991). ...
Bulimulus bonariensis , a snail distributed over a large part of Argentina, has generated negative effects on the agribusiness. We accordingly conducted a seasonal sampling during 2018–2019 in order to characterize the gametic cycle and establish the size of this gastropod at gonadal maturity. Three reproductive stages were identified: the mature in autumn; the spawn, which begins in winter but occurs mainly in the spring, followed by the post-spawn in summer, where an absence of gonadal rest was evidenced. In the fall, in maturity resorption was observed in addition to abundant primary spermatocytes, secondary spermatocytes, and growing vitellogenic oocytes. At the same time, could correlate the degree of spermioviduct development with the stage of gonadal development. Moreover, we used a logistic regression to calculate the size at gonadal maturity, which was established at the total shell length of 12 mm. In addition, we found that at the beginning of reproductive development those gastropods are protogynous hermaphrodites, but after reaching gonadal maturity became simultaneous hermaphrodites. Finally, B. bonariensis also proved to be an iteroparous species. The information provided here will be essential for delineating and establishing population control strategies.
... The genus is found mostly in the Chaco ecoregion in Argentina (northwest, northeast and central Argentina), plus dry areas of southern Bolivia, Brazil, Paraguay, and Uruguay. The Argentinean species have been treated in PilSbry (1898), SalaS OrOñO (2007OrOñO ( , 2010OrOñO ( , 2021 and cuEzzO et al. (2013) under Spixia Pilsbry et Vanatta, 1898, andcuEzzO et al. (2018) under Clessinia. The latter authors stated that Spixia Pilsbry et Vanatta, 1898 was a synonym of Clessinia Doering, 1875 (dOEring 1875a) arguing that both genera shared morphological similarities and had overlapping distribution ranges. ...
Two new species of Odontostomidae are described from Argentina: Clessinia juramentoensis sp. nov. (near Juramento river, Metán Political Department, Salta province) and Clessinia subcylindrica sp. nov. (from Chancani, Pocho Political Department, Córdoba province). Both species are compared with all the species of Clessinia represented in Argentina; images of the related species are presented. C. juramentoensis is characterised by its sub-pyriform shell, small, lustrous to naked eye; secondary ureter opening between the middle and the distal area of the lung roof; penis inner wall with penial area IV occupying 1/3 of penis total length. C. subcylindrica is characterised by its small sub-cylindrical-globose shell, penial area II sculptured with numerous, long, strongly contracted lamellae, penial area III with a pilaster formed of a single fold, much contracted, becoming scalloped. The purpose of this study is to provide complete data on shell morphology and internal anatomy, as well as the distributional information on both species.
Gastropods are a large and diverse taxonomic group, and South America has an
impressive diversity of land snails. However, there are no accurate and complete lists
or estimates of native species’ richness in South America. The aim of this work is to
evaluate the use of iNaturalist in Argentina for terrestrial gastropods and its potential
to contribute to the knowledge of malacofauna. A search was performed for
Argentina on 15 June 2024, filtering observations for terrestrial gastropods, yielding
3,758 records, of which about 10% were of interest for this work. Exotic species
represented between 60–63% of the observations in iNaturalist, and native species
represented between 37–40%, with post-validation and pre-validation respectively.
The geographical distribution of exotic species was mostly concentrated in the urban
areas of the capital cities, and the observations of native species were concentrated in
a few provinces. It was possible to detect and expand the distribution area of exotic
species such as Rumina decollata, Limacus flavus, Bradybaena similaris, Deroceras
laeve, Deroceras reticulatum, Deroceras invadens, Arion intermedius, Milax gagates,
Limax maximus, Vallonia pulchella, possibly Laevicaulis alte; native species such as
Phyllocaulis soleiformis, Drymaeus poecilus, Drymaeus papyraceus. Potential species
not recorded in Argentina were identified as Helix pomatia, Mesembrinus gereti. We
also recorded species within the known range, potential new species not described by
science, a possible case of accidental transfer of Mesembrinus interpunctus, and the
prediction of the distribution of Megalobulimus lorentzianus was verified. Through
the development of this study, we were able to demonstrate the relevance of citizen
science in providing interesting contributions to the knowledge of terrestrial
mollusks biodiversity in Argentina.
Land-snail inventory suffers many gaps in knowledge, especially in countries of the Global South such as Brazil. Studying undersampled regions and providing data on species distributions are among the most pressing matters in Brazilian malacology. Here, we study a sample of land snails collected in the Central-West region of Brazil (“Midwest”) housed in the Coleção Malacológica, Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (University of São Paulo). Ten species from seven families were identified in the material: Alterorhinus constrictus, Anostoma rossi, Aperostoma redfieldi, Bulimulus corumbaensis, Cyclodontina gemellata, Cyclodontina sectilabris, Drymaeus poecilus, Megalobulimus aff. elongatus, Solaropsis fairchildi, and Solaropsis rosarium. The geographic range of four species and one family (Bothriembryontidae) are expanded. We reassess the taxonomic status of two species and consider Anostoma luetzelburgi Weber, 1925 to be a junior synonym of A. rossi Weber, 1925.
Background
Herein, we attempted to obtain detailed data on the distribution of the species of Drymaeus ( Mesembrinus ) in Brazil, using biodiversity databases, malacological collections and literature as sources of occurrence records. We provided a catalogue of species, along with distribution maps. We also estimated the suitable distribution of Drymaeus ( Mesembrinus ) interpunctus using the maximum entropy approach. A detailed description of the anatomy of the soft parts of this species was provided, with new data on the pallial system.
Materials and Methods
For each species we provided information on the compiled data associated with museum collections and the literature. Distribution maps including geographic boundaries, Brazilian biomes and altitude were made with QGIS software 3.16.10 Hannover. For niche modelling, nineteen bioclimatic variables and a topographic variable were used as predictors. The models were performed with MaxEnt version 3.3.3k.
Results
Most of the species are represented by scarce material in malacological collections; for some species, these records correspond to type material, indicating that they have not been recollected. Most of the species were represented by shells making anatomical comparison and DNA analysis difficult, limiting our ability to provide new criteria for species delimitation. Our results allowed us to expand the known distribution area for three species, Drymaeus dutaillyi , D. gereti and D. oreades , with new occurrence records in Brazil. The MaxEnt model showed a thin area of high suitability to D. ( M. ) interpunctus in the Southeastern Brazil, corresponding to the Atlantic Forest. Minimum temperature of the coldest month and mean temperature of coldest quarter were the variables that most influenced the development of the model.
Discussion
Drymaeus interpunctus was described based on specimens collected in Brazil without mention to the exact localities. Herein the new records from databases allowed to expand the known geographic distribution for this species and to infer its potential distribution. Although the type locality of D. interpunctus is in Brazil, the anatomy of the soft parts of specimens from this country was not previously described. The anatomy of the reproductive system of the specimens analyzed herein mostly corresponds to a previous description for specimens from Paraguay, except for the absence of penial sheath and the relative length of the bursa copulatrix duct. The results of niche modeling showed a thin area of high suitability for D. interpunctus and a vast area of moderate suitability, indicating that this species present a niche breadth that favors its occurrence in a range of different biomes, including less suitable areas.
Conclusion
The small number of records obtained for most of the species and their restricted ranges associated with habitat destruction may indicate that they are of conservation concern.
The movement of species is among the most serious environmental threats of the new millennium, as the transplantation of species beyond their native or historical range has intensified in the last five decades. Traditionally, studies on bioinvasions have focused on species that have been introduced, deliberately or accidentally, to biogeographic regions where they did not previously occur. However, less attention has been given to species movement to novel areas within the same biogeographic region. Our research group, the South America Introduced Molluscs Specialists, analyzed potential cases of native South American mollusc species introduced deliberately or accidentally beyond their natural range within South America. To achieve this, it is key to differentiate between anthropogenic processes and passive responses to environmental conditions. We considered the past and current spatial distribution of species, analyzed known or putative vectors, and discuss the impacts of taxonomic and nomenclatural knowledge. Based on the evidence currently available, we propose different scenarios to explain observed changes in mollusc distributions within South America. Seventeen transplanted mollusc species (TMS) were recognized, considering marine, freshwater, and terrestrial environments. Of the 189 South American ecoregions 31 were occupied by transplanted species, but this proportion varied by environment: 10 of 28 marine ecoregions, 12 of 52 freshwater ecoregions, and 9 of 109 terrestrial ecoregions. The ecoregions with TMS are generally located in the peripheral zones of the continent. Those with the highest number of TMS were the Southern Caribbean (three species) in the marine environment, the Central Andean Pacific Slopes (three species) in the freshwater environment, and the Alto Paraná Atlantic forests (two species) in the terrestrial environment. The number of unintentionally moved TMS is greater than those moved intentionally. The transplantation process is similar to the introduction and settlement process of non-native mollusc species, and so is their impact.
In the central region of Argentina, there is a diverse land snail fauna dominated by endemic species. Among them, Austroborus cordillerae (Doering) is a little-known species that could be on the verge of extinction. This work therefore provides updated information on the records of shells by incorporating new field findings.
Despite its natural focus on the New Zealand region, the malacological collection of the Museum of New Zealand Te Papa Tongarewa (NMNZ), also includes a variety of specimens from elsewhere in the world, including a fair share of South American specimens. Examination of this material reveals valuable distributional data for several species, as well as previously unreported type material. This article examines and reidentifies all South American (and Trinidadian) gastropods from the NMNZ collection, excluding those from Brazil, Uruguay and Argentina, which were analysed in a separate publication. All the information gathered is compiled and presented here as an annotated species checklist, including photographs of the most important specimens. In total, 91 species are reported. Paralectotypes of Neniops smithiae (Pilsbry, 1902) (from the private collection of zoologist Henry Suter (1841-1918)) were found in the NMNZ collection and are illustrated here.
A new species of Spixia is described in the context of a revision of the genus. Spixia cuezzae is distributed in the mountain area of Punilla political department, Cordoba, Argentina. The shell is characterised by its fusiform shape sculptured with tall thin ribs separated by narrow intervals and a sub-oval to sub-circular aperture. A large and muscular penial sheath is observed internally. In Spixia, the sculpture of the penis wall is important for differentiation of the species. Spixia cuezzae is characterized by a muscle group forming an inverted V-shape in penial area I. Penial area III exhibits zigzag folds which form a transition and are continuous with pental area IV where the folds straighten longitudinally towards the distal part of the penis. This kind of sculpture has not been observed in other species of the genus. Spixia cuezzae was compared with its most similar species, S. costellifer (Haas 1936) and S. philippii (Doering 1874). Spixia cuezzae differs from them not only in the shell shape, size and teleoconch sculpture but also in some genital characters such as penial sheath length and thickness as well as sculpture of the penial wall.
The genus Spixia (Pilsbry & Vanatta, 1898) is endemic from southern South America. Information about this group is scarce, particularly referring to its anatomy and shell ultrastructure. According to current classification the Spixia pyriformis complex includes the following species, S. doellojuradoi (Parodiz 1941), S. martensii (Doering 1874), S. pyriformis ( Pilsbry 1901) and S. tucumanensis ( Parodiz 1941). In the present study a complete redescription of the species component of this complex, as well as new information on shell ultrastructure and anatomy of the different organ systems is provided. The Spixia pyriformis complex has a pyriform-subpyriform shell shape that distinguishes it from the rest of the species of the genus. Three of the four species studied have a similar periostracum structure consisting of spiral striae and triangular lamellae. Radular morphology is similar in all species. Jaw structure is diagnostic for each species. The inner morphology of the penis is divided into five areas marked by differential pattern of sculpture. Four new anatomical characters, the presence of a pallial gland in the distal portion of the pulmonary roof, the presence of a penial gland in the penial complex, the position of the insertion of the penial retractor muscle in either penial area I or area II and the sculpture of penis inner wall, are identified as the most informative for species diagnosis.
The genus Spixia (Pilsbry & Vanatta, 1898) is endemic from southern South America. Information about this group is scarce, particularly referring to its anatomy and shell ultrastructure. According to current classification the Spixia pyriformis complex includes the following species, S. doellojuradoi (Parodiz 1941), S. martensii (Doering 1874), S. pyriformis (Pilsbry 1901) and S. tucumanensis (Parodiz 1941). In the present study a complete redescription of the species component of this complex, as well as new information on shell ultrastructure and anatomy of the different organ systems is provided. The Spixia pyriformis complex has a pyriform-subpyriform shell shape that distinguishes it from the rest of the species of the genus. Three of the four species studied have a similar periostracum structure consisting of spiral striae and triangular lamellae. Radular morphology is similar in all species. Jaw structure is diagnostic for each species. The inner morphology of the penis is divided into five areas marked by differential pattern of sculpture. Four new anatomical characters, the presence of a pallial gland in the distal portion of the pulmonary roof, the presence of a penial gland in the penial complex, the position of the insertion of the penial retractor muscle in either penial area I or area II and the sculpture of penis inner wall, are identified as the most informative for species diagnosis.
Catálogo Preliminar de la Malacofauna del Paraguay
Quintana, Manuel G.
1982 Rev. Mus. Arg. Cienc. Naturales e Inst. Nac. Invest. Cienc. Nat., Zoología, 11 (3): -158. (in Spanish)
ABSTRACT
The aim of this investigation has been to catalogue systematically the recent mollusks from the Republic of Paraguay, in order to facilitate the access and handling of the existent information for future studies.
174 species and subspecies which belong to 32 families of Gastropoda and 4 of Bivalvia have been registered. One-third of them has been recorded for the first time in this country, extending therefore its known distribution area in some cases.
From the systematical analysis, 19 new nominal combinations (comb. nov.) have been proposed.
For each taxa fundamental synonymy, distribution and location in Paraguay are given. The localities in Paraguay include the bibliographic citations and those given by the author relying on the study of numerous samples taken of paraguayan material.
There is also given a systematical synopsis, bibliography and an index.
Plagiodontes dentatus (Wood, 1828) is the type species of a South American genus including eight named species that show a high degree of local endemism. Due to some misidentifications with P. multiplicatus (Doering, 1874) and P. daedaleus (Deshayes, 1851), P. dentatus has been cited as inhabiting two disjunct areas with quite different ecological conditions. In this paper the identity of this morphospecies is clarified through a study of shell sculpture and apertural teeth data, and a comparison with the smaller adult specimens (<25 mm long) of its closest species, P. patagonicus (d’Orbigny, 1835) and P. multiplicatus, i.e., the only shells to which P. dentatus could have been confounded. A statistical analysis of shell variability revealed that, beyond the qualitative diagnostic characters, there are significantly different shell proportions that also define P. dentatus. The distribution of P. dentatus over two disjunct areas is not supported, its confirmed geographic range being restricted to the Oriental Republic of Uruguay and the Argentine provinces of Entre Ríos and northeastern Buenos Aires. An intraspecific multivariate analysis upholds the opinion that any subspecific discrimination is unwarranted.