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The sigmodontine species name Geoxus lafkenche proposed by Teta and D’Elia (2016) is unavailable, given that the publication where it originally appears did not satisfy the requirements of the International Code of Zoological Nomenclature. In this note we establish the availability of the species name Geoxus lafkenche , by fulfilling those requirements.

The genus Microcavia includes five living species of caviomorph rodents endemic to southern South America. Microcavia jayat, the most recently described species, was recorded in only seven localities of Chaco Seco, in Santiago del Estero province, north-central Argentina. Based on cranial and mandibular remains, corresponding to 23 individuals recovered from owl pellets, we report the first record of this species in La Rioja province, Argentina. This new record implies a southwestern extension of approximately 390 km from the previously known nearest locality, and constitutes its first record in Chaco Serrano habitats within Chaco Seco ecoregion. El género Microcavia incluye cinco especies vivientes de roedores caviomorfos endémicos del sur de América del Sur. Microcavia jayat, la especie descrita más recientemente, se registró en sólo siete localidades del Chaco Seco de la provincia de Santiago del Estero, centro-norte de Argentina. Sobre la base de restos cráneo mandibulares, correspondientes a 23 individuos recuperados de egagrópilas de lechuza, informamos el primer registro de esta especie en la provincia de La Rioja. Este nuevo registro implica una extensión de aproximadamente 390 km hacia el suroeste de la localidad más cercana previamente conocida y constituye su primer registro en ambientes de Chaco Serrano de la ecorregión del Chaco Seco Fil: Bustamante, Erick Ivan. Universidad Nacional de Chilecito; Argentina Fil: Ortiz, Pablo Edmundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Jayat, Jorge Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina

We reviewed the alpha taxonomy of the genus Ctenomys Blainville, 1826 in southernmost South America, with emphasis on those nominal forms previously associated with C. magellanicus Bennett, 1836. We integrate distinct lines of evidence, including variation of mtDNA sequences, and the assessment of quantitative and qualitative traits of skins and skulls; when available, karyotypic data was also considered. Phylogenetic analysis of molecular markers shows low levels of divergence among specimens from southern South American mainland and the island of Tierra del Fuego (ca. 0.4%). This evidence plus the results of the multivariate analysis of metric data suggest that the nominal forms C. colburni J. A. Allen, 1903, C. fueginus Philippi, 1880, C. osgoodi J. A. Allen, 1905, C. m. dicki Osgood, 1943, and C. m. obscurus Texera, 1975 are subjective junior synonyms of C. magellanicus. In addition, we reviewed the status of C. fodax Thomas, 1910, a nominal form that have been alternatively considered as a valid species or related to C. magellanicus by previous researchers. Based on quantitative and qualitative morphological traits, we preliminarily regard C. fodax at the species level while citing it for the first time to Chile.

The combination of morphometrics, phylogenetic comparative methods, and open data sets has renewed interest in relating morphology to adaptation and ecological opportunities. Focusing on the Caviomorpha, a well-studied mammalian group, we evaluated patterns in research and data sharing in studies relating form and function. Caviomorpha encompasses a radiation of rodents that is diverse both taxonomically and ecologically. We reviewed 41 publications investigating ecomorphology in this group. We recorded the type of data used in each study and whether these data were made available, and we re-digitized all provided data. We tracked two major lines of information: collections material examined and trait data for morphological and ecological traits. Collectively, the studies considered 63% of extant caviomorph species; all extant families and genera were represented. We found that species-level trait data rarely were provided. Specimen-level data were even less common. Morphological and ecological data were too heterogeneous and sparse to aggregate into a single data set, so we created relational tables with the data. Additionally, we concatenated all specimen lists into a single data set and standardized all relevant data for phylogenetic hypotheses and gene sequence accessions to facilitate future morphometric and phylogenetic comparative research. This work highlights the importance and ongoing use of scientific collections, and it allows for the integration of specimen information with species trait data. Recientemente ha resurgido el interés por estudiar la relación entre morfología, ecología, y adaptación. Esto se debe al desarrollo de nuevas herramientas morfométricas y filogenéticas, y al acceso a grandes bases de datos para estudios comparados. Revisamos 41 publicaciones sobre ecomorfología de roedores caviomorfos, un grupo diverso y bien estudiado, para evaluar los patrones de investigación y la transparencia para la liberación de datos. Registramos los tipos de datos que se utilizaron para cada estudio y si los datos están disponibles. Cuando estos datos se compartieron, los redigitalizamos. Nos enfocamos en los ejemplares consultados, y en datos que describen rasgos ecológicos y morfológicos para las especies estudiadas. Los estudios que revisamos abarcan el 63% de las especies de caviomorfos que actualmente existen. Encontramos que raramente fueron compartidos los datos que se tomaron para especies, y menos aún para ejemplares. Los datos morfológicos y ecológicos eran demasiado heterogéneos e exiguos para consolidar en un solo banco de datos; debido a esta circunstancia, creamos tablas relacionales con los datos. Además, enlazamos todas las listas individuales de especímenes para crear un solo banco de datos y estandarizamos todos los datos pertinentes a hipótesis filogenéticas, así como los números de acceso de secuencias genéticas, para así facilitar eventuales estudios comparados de morfometría y filogenia. Este trabajo resalta la importancia de las colecciones científicas y documenta su uso, además permitiendo la futura integración de datos derivados de ejemplares con datos sobre rasgos ecomorfológicos a nivel de especie. Fil: Verde Arregoitia, Luis D.. Universidad Austral de Chile; Chile Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: D Elía, Guillermo. Universidad Austral de Chile; Chile

The key role of the skull in food intake and processing implicates its morphology should be to some extent adapted to the functional demands present in different diets, while also showing similarities between those which are closely related. Sigmodontine rodents, with a generalist body plan and broad dietary habits, are an interesting case study to explore these relationships. We used linear morphometrics to assess craniomandibular morphology, and explored its relationship with dietary composition and phylogeny in a sample of sigmodontines from central-eastern Argentina, representative of this subfamily's morphological and ecological diversity. We took 26 measurements performed on 558 specimens belonging to 22 species, and resorted to bibliographic information for proportion of food items in their diets, dietary categories, and phylogeny. Multivariate statistical analyses revealed a strong evolutionary integration between morphological traits of crania and mandibles, and a conspicuous relationship between them and dietary composition in our study group, independent of phylogeny. Species of larger sizes exhibited more robust skulls and a tendency towards folivorous diets, whereas smaller species had more gracile craniomandibular apparatuses and diets richer in seeds and invertebrates. Additionally, we used the observed patterns to made predictions of dietary categories for the three species of this region with unknown diets, completing the map of feeding ecology of one of the most researched group of sigmodontines and enabling future studies to further explore this topic. The present work contributes to understanding the link between morphology, ecology and phylogeny in small mammals.

The identification of taxa with small range sizes is important both from an ecological and conservational perspective. As other small mammals, several species of rodents have restricted geographical distributions, a situation that could increase their immediate risk of extinction. Species having restricted ranges and/or low population sizes have usually lower genetic variation than wide-ranging relatives, being highly susceptive to disruptive treats, such as new or introduced competitors, pathogens, and predators, severe climatic events, cataclysms, and/or population-level phenomena. We reviewed the most recent compilations on South American rodents to identify those only known from their type locality (i. e., an area with a maximum latitudinal and longitudinal range of < 10 km). This restriction is in accordance with an extent of occurrence < 100 km2, which fits partially with the criterion B1 of the IUCN for an extent of occurrence of a critically endangered species. For each species, we recorded the year of description, country of origin, main habitat use, use of substrate, and conservation status. We identified 58 species of South American rodents that are known only from their type localities or their vicinities. These species belong to two suborders, seven families, and 29 genera. The family with more species in this list is Cricetidae, which accounted for a half of the included species. Most species in our list were described during the decades of 1890-1930 and 1990 to recent. The habitat type with more species in the list was tropical forest. Almost a third of the species are considered under the highest categories of threat, such as CR, EN o VU. Two species within the list are considered to become extinct in historical times, including the akodont Juscelinomys candango and the vizcacha Lagostomus crassus. Almost half of the species in our list are referred as DD. Fifty eigth rodent species from South American are only known from their type localities and their surroundings; i. e., ca. 9 % of the currently approximately 650 recorded species of the subcontinent. The species list provided here need to be depurated trough additional field and collection based work. Even when some species could be removed from this list (due taxonomical changes or additional records from other localities), it is also possible than others could be included. Most species in our list are found at or close to highland areas, such as the Andes or the Serra do Mar, suggesting that at least partially the rarity of some of them could be related to the relative inaccessibility of these places. As in previous contributions focused on geographically restricted taxa, most species in our list are considered as DD in the IUCN Red List. This is unfortunate, since species listed as DD usually do not gain much attention (i. e., conservation programs, founds) as those considered as CR, EN or VU. Previous authors discussed this point, suggesting the need to designate as CR all species geographically restricted to their type localities, at least when no recent records (i. e., in the last 25 years) exists.

Akodon oenos, a nominal form with type locality in northern Mendoza province, Argentina, has an intricate taxonomic history. Recently, it was considered a junior synonym of Akodon spegazzinii on the basis of morphological similarities of one individual captured in southern Mendoza with specimens belonging to the type series of A. oenos, plus the genetic similarity of that single specimen with representatives of A. spegazzinii. We compared specimens of the Akodon boliviensis species group recently captured in Mendoza with the type series of A. oenos and series of A. spegazzinii from northwestern Argentina. We conducted an analysis of molecular markers (cytochrome-b gene) and quantitative morphological studies (comparisons of skull measurements). Our results showed that: (1) all sequenced specimens of the A. boliviensis group from Mendoza form a monophyletic clade closely related to A. spegazzinii; (2) contrary to previous hypothesis, specimens of Akodon from Mendoza are morphologically distinctive in size and shape of the skull, from A. spegazzinii; and (3) within the A. boliviensis species group, specimens from Mendoza are distinctive. We argue that the synonymy of A. oenos under A. spegazzinii must await further studies, including molecular markers other than mitochondrial and samples of DNA sequences from topotypical specimens of A. oenos.

Sigmodontine rodents, with 86 genera and ~430 living species, constitute one of the most successful radiations of Neotropical mammals. In this contribution, we studied the distributional ranges of 108 sigmodontine species in Argentina. Our objectives were (i) to establish geographical patterns of species richness and endemism, and (ii) to evaluate the regional conservation status of these taxa. We constructed a minimum convex polygon for each species, using information from literature and biological collections. Individual maps were superimposed on a map of Argentina divided into cells of 25 km on each side. For each cell, we calculated the species richness, which varied between 1 and 21 species, and its degree of endemism, which fluctuated between 0.001 and 3.28. There were 30 species of sigmodontine rodents distributed almost exclusively in Argentina, most of them restricted to forested areas (Southern Andean Yungas) or to arid and semiarid environments (High and Low Monte and Patagonian Steppe). Areas with high species richness and endemism scores corresponded grossly with the Southern Andean Yungas, the Humid Chaco plus the Paraná flooded savannas, the Alto Parana Atlantic forests plus the Araucaria moist forests, the High Monte and the ecotone between the Patagonian steppe and the Valdivian temperate forests. A reassessment of the conservation status of sigmodontine rodents distributed in Argentina retrieved 2 extinct species, 7 endangered, 7 vulnerable, 6 near threatened and 13 data deficient. These numbers suggest a much more serious situation than the expressed by previous evaluations, highlighting the urgent need to establish conservation measures for the protection of this group. Los roedores sigmodontinos, con 86 géneros y ~430 especies vivientes, constituyen una de las radiaciones más exitosas de mamíferos neotropicales. En esta contribución, estudiamos los rangos de distribución de 108 especies de sigmodontinos en Argentina. Nuestros objetivos fueron (i) establecer patrones geográficos de riqueza de especies y endemismo y (ii) evaluar el estado de conservación regional de estos taxones. Construimos un polígono convexo mínimo para cada especie, utilizando información de la literatura y colecciones biológicas. Los mapas individuales fueron superpuestos en un mapa de Argentina dividido en celdas de 25 km de lado. Para cada celda, calculamos la riqueza de especies, que varió entre 1 y 21, y su grado de endemismo, que fluctuó entre 0.001 y 3.28. Hubo 30 especies de roedores sigmodontinos distribuidos casi exclusivamente en Argentina, la mayoría de ellos restringidos a áreas boscosas (Yungas andinas del sur) o a ambientes áridos y semiáridos (Monte alto y bajo y Estepa Patagónica). Las áreas con mayor riqueza de especies y valores más altos de endemismo se correspondieron groseramente con las Yungas andinas del sur, el Chaco húmedo más las Sabanas inundadas de Paraná, el Bosque Atlántico del Alto Paraná más los Bosques húmedos de araucaria, el Monte alto y el ecotono entre la Estepa Patagónica y los Bosques templados valdivianos. Una reevaluación del estado de conservación de los roedores sigmodontinos distribuidos en Argentina recuperó 2 especies extintas, 7 en peligro, 7 vulnerables, 6 casi amenazadas y 13 con datos deficientes. Estas cifras sugieren una situación mucho más grave que la expresada en evaluaciones anteriores, destacando la necesidad urgente de establecer medidas de conservación para la protección de este grupo. Fil: Formoso, Anahí Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Fil: Olmos, Matias Natanael. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Zootaxa came as a new and innovative publication medium for taxonomy, amidst a scenario of devaluation of this important biological science. After 20 years, it has ascertained itself as one of the main journals in animal taxonomy. However, the contribution of the journal to the taxonomy of Mammalia (mammals), one of the most studied groups of animals with a long-standing, dedicated spectrum of specialized journals (mammalogy), could have been expected as minor. All the current and former editors of the Mammalia section of Zootaxa analyzed the relative contribution of the journal to the description of new species of mammals since 2001. We also analyzed the contribution of Zootaxa by taxon, geographic origin of taxa, and geographic origin of first authors. The taxonomic methodology of authors in species description is described as well as the temporal trends in publications and publication subjects. We highlight the editors’ picks and eventually, the challenges for the future. We found that Zootaxa has had a significant contribution to mammalogy, being the second journal (the first being Journal of Mammalogy) in terms of number of new species described (76; 10.6% of the new mammalian species described between 2001 and 2020). The majority of the new species were described following an integrative taxonomic approach with at least two sources of data (86%). The analysis of published taxa, their geographic origin, and the country of origin of first authors shows a wide coverage and exhaustive representation, except for the species from the Nearctic. We conclude that Zootaxa has likely responded to a repressed demand for an additional taxonomic journal in mammalogy, with as possible appeals the absence of publication fees and an established publication speed. With 246 articles published in the past 20 years, the Mammalia section of Zootaxa embraces a large spectrum of systematic subjects going beyond alpha taxonomy. The challenges for the future are to encourage publications of authors from the African continent, still poorly represented, and from the palaeontology community, as the journal has been open to palaeontology since its early days.

Rodents are an important component of South America fauna. Their high diversity has motivated researchers to continually review their taxonomy, genetic diversity, species limits, and phylogenetic relationships. Here, we applied DNA-barcodes for assessing the taxonomic and genetic diversity in the two major lineages of South American rodents: caviomorphs and sigmodontines. We analysed 335 COI barcodes in 34 morphologically determined species from 39 localities along central Andes and arid lands of Argentina. Neighbour-joining and maximum likelihood reconstruction provided clear separation between species. The Barcode Index number and Bayesian Poisson tree processes were used to confirm concordance between sequence clusters and species designations by taxonomy. We found deep divergence within the Phyllotis xanthopygus species complex, with distances up to 13.0% between geographically separated lineages. Minor divergences (3.30% and 2.52%) were found within Abrothrix hirta, and Tympanoctomys barrerae, respectively, with differentiation in their genetic lineages. Also, we documented geographically separated clusters for Akodon spegazzinii and A. oenos with up to 2.3% divergence, but clustering methods failed to distinguish them as different species. Sequence results show a clear barcode gap with a mean intraspecific divergence (0.56%) versus a minimum nearest-neighbour distance averaging (10.1%). Distances between congeneric species varied from 4.1 to 14%, with the exception of two related forms within Euneomys and the sister species Akodon spegazzinii and A. oenos. This study constitutes a substantial contribution to the global barcode reference library. It provides insights into the complex phylogeographic patterns and speciation scenarios in rodents, while highlighting areas that require in-depth taxonomic and integrative research.

Los micromamíferos representan uno de los componentes más importante de las comunidades de vertebrados terrestres neotropicales. Una metodología muy utilizada para analizar la composición de sus ensambles y los parámetros que los caracterizan (i.e., riqueza, diversidad) es el análisis de egagrópilas de aves rapaces. En Argentina, uno de los pioneros en utilizar esta metodología fue Elio Massoia en la década de 1960. Desde entonces, los trabajos basados en el estudio de egagrópilas para obtener información sobre micromamíferos fueron en aumento. El objetivo de este trabajo es documentar cómo esta metodología cambió nuestro conocimiento sobre los micromamíferos patagónicos. Se revisó la bibliografía publicada sobre análisis de egagrópilas y estudios enfocados en micromamíferos para la Patagonia argentina. El material recuperado de las egagrópilas ha permitido analizar la variabilidad intraespecífica de especies poco representadas en colecciones de museos o difíciles de capturar mediante trampas. Esta herramienta cambió de forma extraordinaria nuestra percepción sobre la biogeografía y distribuciones geográficas de muchas especies patagónicas (e.g., Calomys musculinus, Galea leucoblephara, Graomys griseoflavus, Lestodelphys halli, Loxodontomys micropus, Microcavia australis, Notiomys edwardsii, Paynomys macronyx, Thylamys pallidior). Asimismo, permitió reconsiderar las categorías de conservación de algunas especies que se creían raras y que demostraron solamente estar subrepresentadas en los muestreos tradicionales (i.e., N. edwardsii, L. halli, Euneomys chinchilloides e Irenomys tarsalis). Finalmente, también nos ha permitido reconstruir la estructura de los ensambles y los cambios que han atravesado desde al menos el Pleistoceno Tardío, documentando retracciones regionales, variaciones dramáticas en las frecuencias relativas y cambios en la dominancia de especies en los conjuntos actuales como consecuencia del impacto antrópico. El análisis de egagrópilas de aves rapaces representa una herramienta poderosa, especialmente en áreas extensas que serían difíciles de prospectar mediante otros métodos. Micromammals represent one of the most important components of the Neotropical terrestrial vertebrate communities. A widely used methodology to analyze the composition of their assemblages and the parameters that characterize them (i.e., richness, diversity) is the analysis of pellets produced by birdsof prey. In Argentina, one of the pioneers in using this methodology was Elio Massoia. From that momenton, the studies based on the study of pellets to obtain information on small mammals were on the rise. Theobjective of this work is to document how this methodology changed our knowledge about Patagonian micromammals. We reviewed the published bibliography on pellet analysis and studies focused on smallmammals for Argentinian Patagonia. The material recovered from pellets has made it possible to analyze theintraspeci c variability of species poorly represented in museum collections or di cult to capture using traps.This tool also dramatically changed our perception of the biogeography and geographical distributions of manyPatagonian species (e.g.,Calomys musculinus,Galea leucoblephara,Graomys griseo avus,Lestodelphys halli,Loxodontomys micropus,Microcavia australis,Notiomys edwardsii,Paynomys macronyx,Thylamys pallidior).Likewise, it allowed reconsidering the conservation categories of some species that were believed to be rare(i.e.,N. edwardsii,L. halli,Euneomys chinchilloidesandIrenomys tarsalis). Finally, it has also allowed us toreconstruct the structure of the assemblages and the changes on them since at least the Late Pleistocene,documenting regional retractions, dramatic variations in relative frequencies, and changes in the dominanceof species in recent assemblages as a consequence of the anthropic impact. Pellet analysis of birds of preyrepresents a powerful tool, especially in large areas that would be di cult to survey by other methods Fil: Formoso, Anahí Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad del Chubut; Argentina Fil: Udrizar Sauthier, Daniel Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia San Juan Bosco; Argentina Fil: de Tommaso, Daniela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentina. Universidad Tecnológica Nacional. Facultad Regional Chubut; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Molecular genetic data are increasingly used to assist in species identification and delimitation, and provide a powerful tool to detect conservation units (population/s of an organism considered to be different for conservation purposes). In combination with distributional and ecological information, molecular genetic data can contribute to establishing the conservation status of species and populations. Here, we review these applications to rodent species in Argentina, a diverse assemblage of some 200 species. We capitalize on recent efforts to establish the conservation status of mammals in Argentina and combine this information with available molecular genetic data for rodents in this country. This portion of the southern South America offers exceptional cases of population differentiation and species diversification related to a wide and diverse geography, which includes varied landscapes such as the Patagonian steppe, Andean highlands, tropical and subtropical forests, and the Monte and Pampa regions. Many species are data deficient (including no or limited genetic data) and only known from their type localities. Among the remaining species, most have at least some available mitochondrial DNA sequence data and these, coupled with morphological, karyotypic and (less frequently) nuclear DNA sequence or microsatellite data have been instrumental in identifying and delimiting species. In general, multilocus data with the desirable geographical density are lacking for all but a few species that have been studied in greater detail. Studies coupling genetic and ecological data (e.g. landscape or ecological genetics) are limited to a handful of more intensively studied cases. Given that habitat loss and fragmentation are among the major threats for survival of natural populations, assessing the extent of these threatening processes is crucial in conservation management and a priority in studies of conservation biology.

The genus Ctenomys Blainville, 1826 is, with 64 living species, one of the most species-rich genera of Mammalia. In this chapter, structured in two main sections, we discuss distinct issues related to the taxonomy and phylogeny of these rodents. Each section begins with a short historical summary and then focuses on the current state of knowledge. We provide a list of currently considered distinct species (remarking on departures from the most recent tuco-tuco taxonomic catalog), discuss candidate species, and unavailable names (i.e., those never properly published, such as C. “chasiquensis” or C. “yolandae”). In what constitutes the single nomenclatorial act of this contribution, we propose that C. azarae Rusconi and C. porteuosi Thomas are subjective junior synonyms of C. mendocinus Philippi. We provide a historical perspective about phylogenetic studies of tuco-tucos, remarking on species relationships and species groups, and summarizing the contents of the species groups. We also synthesize the available dating studies for this genus. In each section, we also highlight gray areas that need to be the focus of future research.

The anthropic effect associated with worldwide European settlements over the last 500 years has caused dramatic environmental changes, modified regional patterns of biodiversity, and often led to local or complete extinctions. The sigmodontine rodents of Bahía Samborombón (Humid Pampas, central-eastern Argentina) constitute a good case study: a late Holocene archaeological site allowed us to compare a pre-European settlement assemblage (12 species) with the extant one (nine species). We used linear morphometrics (16 cranial and ten mandibular measurements) to assess interspecific morphological variations of the masticatory apparatus in relation to dietary habits for each assemblage. Even though sigmodontines have a tendency towards omnivory, groups based on dietary preference only overlapped partially. Size was one of the main variables involved in niche segregation, and shape characteristics such as rostrum elongation or mandible robustness were linked to different diets. We found that a combination of dietary preference and size was associated with extinctions. The main morphospace change between the two assemblages was related to the local extinction of the three greater insectivores and the smallest graminivore, located towards the center of the assemblage’s morphospace. An insectivore was incorporated, involving no significant changes in the general morphospace. Graminivores and larvivores were not affected. Our study sheds light on the causes of local extinctions of small mammals at the Humid Pampas, a phenomenon that had never been studied from an ecomorphological approach. Fil: Barbero, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Cassini, Guillermo Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina

Sobre la distinción y disponibilidad de los nuevos taxones propuestos por Agnolin et al. 2019. Recientemente, Agnolin et al. (2019) describieron 14 especies nuevas de mamíferos, incluyendo 12 roedores, un murciélago y un carnívoro, y una nueva subespecie de roedor. Además, estos autores propusieron varios otros actos nomenclatoriales: algunas formas nominales se eliminaron de las sinonimias y se hipotetizaron como especies distintas; se nombraron tres nuevos géneros, una subtribu y una tribu demamíferos. Revisamos todos los actos nomenclatoriales propuestos por Agnolin et al. (2019) y concluimos que las 14 nuevas especies y la nueva subespecie, así como las formas eliminadas de las sinonimias, deben tratarse como sinónimos de especies ya conocidas. Sugerimos lo mismo con respecto a los tres nuevos taxones supraespecí cos presentados por Agnolin et al. (2019), de los cuales dos no están disponibles ya que no cumplen con las disposiciones del Código Internacional de Nomenclatura Zoológica. Terminamos esta contribución criticando la forma en que Agnolin et al. (2019) realizaron su abordaje taxonómico. Recently, Agnolin et al. (2019) described 14 new species of mammals, including 12 rodents,one bat, and one carnivore, and one new subspecies of rodent. In addition, these authors proposed severalother nomenclatorial acts: some nominal forms were removed from synonymies and hypothesized as distinctspecies, at the time that three new genera, one subtribe, and one tribe of mammals were also named. Wereviewed the merits of all nomenclatorial acts proposed by Agnolin at al. (2019) and concluded that all 14new species and the new subspecies, as well as those forms removed from synonymies, should be treatedas synonyms of already known species. We suggest the same regarding the three new supraspecic taxapresented by Agnolin et al., two of which are not available as they fail to comply with the provisions of theInternational Code of Zoological Nomenclature. We end this contribution criticizing the way that mammaltaxonomy was approached by Agnolin et al. (2019). Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: D'elía, Guillermo. Universidad Austral de Chile; Chile Fil: Jayat, Jorge Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina Fil: Gonçalves, Pablo Rodrigues. Universidade Federal do Rio de Janeiro; Brasil Fil: Simoes Libardi, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentina. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil Fil: Oliveira, João Alves de. Universidade Federal do Rio de Janeiro. Museu Nacional; Brasil Fil: Moratelli, Ricardo. Fundación Oswaldo Cruz; Brasil Fil: Reis Percequillo, Alexandre. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil Fil: Prado, Joyce Rodrigues do. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil Fil: Ortiz, Pablo Edmundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Miguel Lillo; Argentina Fil: Hurtado, Natali. Universidad Nacional de San Agustin; Perú Fil: Schiaffini, Mauro Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagónica. Universidad Nacional de la Patagonia "San Juan Bosco". Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Laboratorio de Investigaciones en Evolución y Biodiversidad; Argentina Fil: Abreu Jr., Edson Fiedler de. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil Fil: Chiquito, Elisandra Almeida. Instituto Nacional da Mata Atlântica; Brasil Fil: Giménez, Analía Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagónica. Universidad Nacional de la Patagonia "San Juan Bosco". Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Laboratorio de Investigaciones en Evolución y Biodiversidad; Argentina Fil: Torres, Julio. Instituto de Investigación Biológica del Paraguay; Paraguay

En esta nota reportamos tres nuevos especímenes de Abrothrix (Angelomys) xanthorhina para Isla de los Estados, en el extremo austral de Argentina, que son representativos de la forma nominal Akodon llanoi Pine 1976. Estos son los primeros especímenes de referencia desde su descripción, hace más de cuatro décadas. Adicionalmente, proveemos datos morfométricos para estos ejemplares y una actualización de la distribución de esta especie en la isla. En virtud de su rareza y su condición de endemismo insular, sumada a la presencia de Rattus norvegicus en Isla de los Estados, sospechamos que el estado de conservación de este ratón estaría comprometido. In this note we report three new specimens of Abrothrix (Angelomys) xanthorhina from Isla de los Estados, southernmost Argentina, which are representative of the nominal form Akodon llanoi Pine 1976. These are the first voucher specimens since the species description, more than four decades ago. In addition, we provide morphometric data for these specimens and update the distribution of the species on the island. Because of its rarity and isolated condition, added to the presence of Rattus norvegicus in Isla de los Estados, we suspect that the conservation status of this population could be compromised. Fil: Sánchez, Julieta. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Poljak, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina Fil: Lanusse, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Balza, Ulises. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Salom, Amira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Lois, Nicolás Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Lizarralde, Marta Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

We conducted a geometric morphometric analysis to investigate the morphological variation of the golden wolf, Canis lupaster, and to clarify the morphological and taxonomic affinities of different taxa of the genera Canis and Lupulella. We suggest that the variation observed within the complex of Canis lupaster may be incompatible with what would be expected for a single species. We hypothesize that the nominal form C. l. soudanicus is a synonym of Lupulella adusta rather than being part of the golden wolf complex. The subspecies C. l. bea has a generalized jackal morphology (i.e., clusters together with L. mesomelas and C. aureus) and C. l. lupaster occupies an intermediate morphospace position, between jackal-like forms and wolf-like forms. These results contrast with previously published molecular analysis in which mitochondrial data failed to identify differences among golden wolf populations, and nuclear evidence points to the existence of groups that are incompatible with those recovered by morphological analysis. Regarding other jackals, our results depict the absence of morphological overlap between L. m. mesomelas and L. m. schmidti and no differences between putative subspecies of L. adusta. We call attention to the need for more integrative approaches to solve the taxonomic questions in various African Canidae. Fil: de Andrade Machado, Fabio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. University of Massachussets; Estados Unidos Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Background Leptospirosis is a zoonotic disease that can be transmitted by contact with the urine of infected mammals. Rodents play a mayor role in the transmission of leptospires to humans. The province of Santa Fe reports the greatest number of cases in Argentina. Yet, in this region, there are still knowledge gaps regarding the diversity of rodent species that may be hosts of pathogenic leptospires. The aims of this study were to evaluate the presence of leptospiral antibodies in rodents from three riverside communities of Santa Fe, and to identify factors associated with leptospiral infection. Methodology/Principal findings Each community was divided into three environmental settings based on the level of human disturbance, and sampled during two springs (Sep-Oct 2014 and 2015) and one autumn (Mar-Apr 2015). Serum samples of captured sigmodontine and murine rodents were tested for leptospiral antibodies by enzyme-linked immunosorbent assay (ELISA), and microagglutination test (MAT) was used to assess the infecting serovar in seropositive individuals. Factors influencing seropositivity were analyzed using logistic regression models. We caught 119 rodents, of which 101 serums were suitable for analysis. Most frequently trapped species were Scapteromys aquaticus, Akodon azarae and Oligoryzomys spp., with seroprevalences of 41.3%, 42.9% and 55% respectively. Seropositivity was higher in individuals with an average body condition score and in those that were sexually mature, but in the latter the differences were marginally significant. Conclusions/Significance Our results suggest that native rodents may be playing a role in the environmental circulation of pathogenic leptospires and provide relevant information for public health policies in the area., Author summary Rodents are considered as the main reservoirs of pathogenic leptospires, which can cause leptospirosis, a disease that can be severe for both humans and domestic animals. Multiple socio-environmental factors have been found to influence the risk of leptospirosis, and many mammal species can play a role in the transmission of the bacteria. The purpose of this study was to investigate the local conditions and rodent fauna that may influence the risk of leptospirosis in communities located in the floodplains of the Parana river, near Santa Fe, Argentina. We conducted a survey of antibodies against leptospires in rodents from the center, border, and outside of three riverside settlements. We observed a relatively high seroprevalence among captured individuals (42%). Animals with an intermediate body condition were more likely to be seropositive. In most sites, native rodents were dominant over introduced rats and mice and lived close to human dwellings. Given the socio-environmental conditions observed in these settlements and the high frequency of floods that affect them, the presence of potentially infected rodents provide ample opportunities for leptospirosis to affect these communities.

Ctenomys Blainville 1826 is one of the most diverse genera of South American caviomorph rodents. Currently, six species of this genus are reported from Patagonia, south of 42◦S. In this contribution, we assessed the taxonomic status of several populations from eastern and central Chubut province, northern Patagonia. Based on phylogenetic analyses of DNA sequences, morphology assessment (qualitative and quantitative), and previously published karyological data, we describe three new species of this genus, one formed by two subspecies, endemic to northern Patagonia. In addition, we include C. coyhaiquensis Kelt and Gallardo 1994 into the synonymy of C. sericeus J.A. Allen 1903. Finally, we discussed the need for additional integrative approaches, including field collection of specimens, to better understand the diversity of this highly speciose rodent genus. Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: D Elía, Guillermo. Universidad Austral de Chile; Chile

Se reporta una nueva localidad de registro para Lyncodon patagonicus en la provincia de San Luis, Argentina. Se colectó el cráneo de un ejemplar de esta especie en el Parque Nacional Sierra de las Quijadas, siendo el primer registro reciente de este carnívoro para esta provincia. A new record for Lyncodon patagonicus is reported for San Luis province, Argentina. A skull of an individual of this species was collected in Sierra de las Quijadas National Park, being the first recent record of this carnivore for this province. Fil: Martínez Retta, Lucia. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentina Fil: Ochoa, Ana Cecilia. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; Argentina Fil: Gatica, Ailin. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; Argentina Fil: Lucero, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Pardo, Victor M.. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Bioquímica y Ciencias Biológicas; Argentina

Se reportan dos nuevas localidades de registro para Monodelphis domestica en Argentina, que son a su vez las primeras para la provincia de Santiago del Estero. Los ejemplares fueron capturados en dos localidades del departamento Copo: i) cercanías de Caburé Sur (26° 07´ 37.4″ S, 62° 30´ 41.07″ O) y ii) Parque Provincial Copo (25° 55´ 2.54″ S, 61° 54´ 54.55″ O). Estos nuevos registros extienden 200 km al SSO la distribución conocida de este marsupial. We report two new localities for Monodelphis domestica in Argentina; these are also the first records for the province of Santiago del Estero. The species was captured in two localities of Copo Department: i) vicinity of Caburé Sur. (S26° 07´ 37.4″, W62° 30´ 41.07″) and ii) Parque Provincial Copo (S5° 55´ 2.54″, W61° 54´ 54.55″). These records extend the known distribution of this marsupial 200 km SSW. Fil: Ochoa, Ana Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Bioquímica y Ciencias Biológicas; Argentina Fil: Paez, Ricardo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

Fil: Lanzone, Cecilia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Instituto de Biologia Subtropical. Instituto de Biologia Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biologia Subtropical. Instituto de Biologia Subtropical - Nodo Posadas; Argentina

El género Galea (Rodentia, Caviidae) incluye cinco especies vivientes y dos extintas de cávidos terrestres y herbívoros, que ocupan pastizales y matorrales rocosos, tanto en áreas altas como bajas de América del Sur. Algunas muestras fósiles del Pleistoceno-Holoceno del centro-este de Argentina han sido referidas como Galea sp., G. musteloides o G. cf. musteloides y finalmente se describieron como una nueva especie bajo el nombre de G. tixiensis. Sin embargo, estudios recientes basados en series grandes de individuos fallaron en encontrar diferencias morfológicas cualitativas entre G. lecucoblephara y G. tixiensis. Sobre la base de estos hallazgos, en esta contribución revisamos el estatus taxonómico de la especie extinta G. tixiensis. Se examinaron 110 individuos de las tres subespecies actualmente reconocidas de G. leucoblephara (i.e., G. l. demissa, G. l. leucoblephara y G. l. littoralis) de Argentina, Bolivia y Paraguay. Se registraron nueve medidas cráneo-dentarias. Los datos cuantitativos se sometieron a un análisis de componentes principales (PCA) con el fin de identificar la contribución de cada medida a la varianza total. Los caracteres cualitativos se evaluaron a través de las comparaciones de los rasgos supuestamente diagnósticos de G. tixiensis con la variabilidad representada por las muestras recientes. Los espacios multivariados de las tres subespecies estudiadas se superpusieron ampliamente en el PCA, lo que sugiere que estos taxones no difieren significativamente en la figura del cráneo. El holotipo de G. tixiensis se ubicó dentro del morfoespacio correspondiente a muestras recientes de G. l. littoralis. Los caracteres cualitativos supuestamente diagnósticos de G. tixiensis también se verificaron en muestras recientes de G. leucoblephara, en particular de G. l. littoralis. Sobre la base de sus rasgos craneanos cualitativos y cuantitativos se sugiere que G. tixiensis es un sinónimo de G. leucoblephara. Los mayores valores para algunos rasgos craneanos cuantitativos en las muestras fósiles –comparadas con las actuales– son reinterpretados en este trabajo como una respuesta ecofenotipica a las condiciones climáticas más severas durante el Holoceno. The genus Galea (Rodentia, Caviidae) includes five living and two extinct species of terrestrial and herbivorous cavies that inhabit grasslandsand rocky scrub areas at both high and low elevations in South America. Fossil samples from the late Pleistocene-Holocene from central-easternArgentina have been referred to as Galea sp., G musteloides or G. cf. musteloides and finally described as a new species under the name of G. tixiensis. However, recent studies based on large series of individuals fail to find qualitative morphological differences between G. leucoblephara and G.tixiensis. Based on these findings, in this contribution we reviewed the taxonomic status of the fossil species G. tixiensis. A total of 110 individualsof the three currently recognized subspecies of G. leucoblephara (i. e., G. l. demissa, G. l. leucoblephara and G. l. littoralis) from Argentina Boliviaand Paraguay were examined. Nine craniodental measurements were recorded. Quantitative data were subjected to a principal component analysis (PCA) in order to identify the contribution of each measurement to the total variance. Qualitative characters were evaluated through the comparisons of the diagnostic traits of G. tixiensis with the variability derived from the recent samples. PCA showed a high overlap of the multivariate spaces of the three subspecies studied, suggesting that they do not differ significantly in terms of cranial shape. The holotype of G. tixiensis was allocated within the morphospace of the recent G. l. littoralis samples. Qualitative traits diagnostic of G. tixiensis were also recorded in recent samples of G. leucoblephara, in particular of G. l. littoralis. Based on both qualitative and quantitative cranial traits, we suggest that G. tixiensis is a synonym of G. leucoblephara. The morphological traits supposedly unique to G. tixiensis were also recorded in specimens of living populations of G. l. littoralis. The large values of some quantitative cranial traits in fossil samples -compared to living ones- are reinterpreted here as an ecophenotypical response to the more severe climatic conditions of the Holocene. Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Campo, Denise Heliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina

Rodents are a very diverse group with large chromosome variability. One of the most species rich linage in the Neotropics is the Sigmodontinae. Among them, the tribe Abrotrichini was recently defined and its taxonomy and phylogeny were mostly elucidated through molecular and morphological evidence. Meanwhile, chromosome data were only secondarily used because of fragmentary information. In this contribution, we conduct a chromosome characterization of Abrothrix hirta, A. olivacea, A. andina, and Paynomys macronyx, review the cytogenetic background of the tribe, and contrast it with molecular data. Chromosomes were analyzed by conventional and differential techniques. All Abrothrix species presented 2n = 52/FNa = 56, with a high similarity in the banding patterns reflecting a conserved karyotype, which does not coincide with its high molecular variability. In turn, P. macronyx have 2n = 54/FNa = 58–59, varying due to a heteromorphic pair of autosomes. In addition, in this last species, different morphologies of the X chromosome and the presence of B chromosomes were detected. Heterochromatin was involved in these variants. The telomeric probe in P. macronyx marks terminal regions of all chromosomes. B chromosomes generated strong telomeric signals. The Ag-NORs banding revealed the same patterns in Abrothrix and Paynomys. Cytogenetic data support phylogenetic relationships previously proposed and suggest that the specious genus Abrothrix could have retained the ancestral karyotype of the subfamily. In the tribe, the relatively conserved chromosome complement contrasts with its high molecular variability. This indicates decoupling between the rates of chromosomal and molecular divergence, as observed in other rodent lineages. In abrotrichines, chromosome evolution was slower., Facultad de Ciencias Naturales y Museo