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The genus Smacigastes Ivanenko & Defaye, 2004 (Harpacticoida, Copepoda) is the most primitive genus in the family Tegastidae Sars, 1904, occurring in deep-sea chemosynthetic environments, such as hydrothermal vents, cold seeps, whale falls and wood falls. Our exploration of the Onnuri Vent Field, the sixth active hydrothermal vent system in the Central Indian Ridge, resulted in the discovery of a new species in the genus Smacigastes. A detailed morphological analysis of S. pumilasp. nov. reveals that it most resembles S. barti Gollner, Ivanenko & Martínez Arbizu, 2008, described from a hydrothermal vent in the East Pacific Ridge; the new species can be distinguished from the existing species by the 8-segmented female antennule, the absence of an abexopodal seta on the antennary basis, the mandibular exopod represented by a single seta and the exopod of the first leg with five setae. This is the first record of Smacigastes in the Indian Ocean. A dichotomous key to species of the genus Smacigastes worldwide is provided.

Senecio festucoides is described from northern Chile. The new species is morphologically similar to the discoid caespitose Andean species and belongs to the subgroup displaying yellow corollas and yellowish anthers and style branches. It is characterized by a weak, not self-supporting stem, narrowly linear leaves, long pedunculate capitula with (17–)21 involucral bracts, and minutely papillose achenes. Among other characters, the color of the corollas, anthers, and style branches and the number of involucral bracts differentiate it from S. scorzonerifolius, which is the morphologically closest species. The new species thrives in the desertic Puna ecoregion and grows amongst tufts of Festuca chrysophylla (Poaceae). Detailed pictures of living plants are provided, as well as a distribution map and a dichotomous key to the discoid caespitose Senecio species from northern Chile.

The identification of anuran amphibians is still a challenge in megadiverse assemblages. In the Neotropics, the Atlantic Forest harbors more than 600 anuran species, and many studies in this ecoregion report anuran assemblages surpassing 30 species. Taxonomic keys facilitate the identification of biological diversity, however only a few are available for anuran assemblages in the Atlantic Forest. Herein we present an identification key for 40 anuran species distributed across 20 genera and nine families, occurring in the Environmental Protection Area of Catolé and Fernão Velho, northeastern Atlantic Forest. Thirty-five morphological characteristics were used in the key, all of which can be easily observed in living and museum specimens. This pioneer study provides the first identification key for an amphibian assemblage in the northeastern Atlantic Forest and this baseline information acts as the starting point for the development of evolutionary and ecological research in this conservation unit.

Myrtaceae is a plant family with outstanding diversity in the neotropics, which species are of difficult identification. Thus, for the differentiation between species to be possible, targeted inventories and detailed descriptions are necessary, to develop accessible and reliable identification tools. The goal of this research is to quantify the species richness and describe vegetative characters of Myrtaceae species from a Araucaria Rainforest remnant, through identification of patterns and the elaboration of an dendrological key. For the characterization of trunk and bark, up to five healthy adult individuals of each species were selected, and for branches and leaves, up to three individuals. The voucher material was deposited at the Herbarium EFC. The vegetative morphology of each species was described and an identification key was prepared. 29 species, belonging to 11 genera, were documented: Blepharocalyx (1), Campomanesia (3), Eugenia (5), Myrceugenia (5), Myrcia (8), Myrcianthes (1), Myrciaria (1), Myrrhinium (1), Pimenta (1), Plinia (1) and Psidium (2). The main dendrological characteristics used for the species differentiation were: rhytidome aspect, appearance and colour of the internal bark, venation, punctuations, indumentum and dimensions of the leaf blade. Differentiation was possible using vegetative characters, with greater difficulty for two very similar species of Campomanesia. Resumo A família Myrtaceae apresenta grande diversidade nos neotrópicos e suas espécies são de difícil identificação, sendo necessários inventários específicos e descrições detalhadas para elaborar ferramentas acessíveis e confiáveis que facilitem sua diferenciação. O objetivo desta pesquisa foi quantificar a riqueza e descrever os caracteres macromorfológicos vegetativos das espécies de Myrtaceae de um remanescente de Floresta Ombrófila Mista, visando identificar padrões e elaborar uma chave dendrológica de identificação. Foram selecionados até 5 indivíduos adultos e sadios por espécie para caracterização de tronco e casca, e até 3 para ramos e folhas. O material testemunho foi depositado no Herbário EFC. Foi descrita a morfologia vegetativa de cada espécie e elaborada uma chave de identificação. Foram encontradas 29 espécies pertencentes à 11 gêneros: Blepharocalyx (1), Campomanesia (3), Eugenia (5), Myrceugenia (5), Myrcia (8), Myrcianthes (1), Myrciaria (1), Myrrhinium (1), Pimenta (1) Plinia (1) e Psidium (2). As principais características dendrológicas utilizadas para diferenciação das espécies foram: aspecto do ritidoma, aparência e cor da casca interna, venação, pontuações, indumento e dimensões do limbo foliar. Foi possível a diferenciação das espécies utilizando caracteres vegetativos, com ressalva para o gênero Campomanesia, que apresenta duas espécies muito similares com maior dificuldade de diferenciação entre si.

The names Werneria melanandra and W. pygmophylla are transferred to the genus Senecio. They belong to the group of the discoid caespitose Andean Senecio, specifically to the subgroup with blackish anthers and style branches and whitish corollas. The recognition of S. digitatus as a distinct species is also discussed. Within the framework of the mentioned group, the names S. casapaltensis and S. macrorrhizus are lectotypified, S. humillimus var. melanolepis is neotypified, an epitype is designated for the name W. melanandra, and nine new synonyms are proposed. An updated comprehensive dichotomous key including all discoid caespitose Senecio species from Bolivia and Peru is provided.

Until recently, only two haemaphysaline species, Haemaphysalis chordeilis (Packard, 1869) and Haemaphysalis leporispalustris (Packard, 1869), were known to occur in the United States, and neither was considered to be of significant medical or veterinary importance. In 2017–2018 established populations of the Asian longhorned tick, Haemaphysalis longicornis Neumann, 1901, were detected in the eastern US for the first time. Haemaphysalis longicornis has the potential to be a significant threat to human and animal health, and the urgent need to determine the full extent of its distribution and host range requires availability of a straightforward and practical guide to differentiate it from native species. We created a pictorial dichotomous key to all stages of Haemaphysalis spp. known to occur in North America with scanning electron photomicrographs of all H. longicornis life stages, including rarely seen males, to aid researchers in differentiating these species. The largely Neotropical species Haemaphysalis juxtakochi Cooley, 1946, with established populations in Mexico and sporadic detections in the US on migrating birds is also included. EEA Rafaela Fil: Egizi, Andrea M. Monmouth County Mosquito Control Division, Titon Falls; Estados Unidos. Rutgers University; Estados Unidos Fil: Robbins, Richard G. Smithsonian Institution. Department of Entomology; Estados Unidos Fil: Beati, Lorenza. Georgia Southern University. Institute for Coastal Plain Science. United States National Tick Collection; Estados Unidos Fil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Evans, Colleen R. Georgia Southern University. Institute for Coastal Plain Science. United States National Tick Collection; Estados Unidos Fil: Occi, James L. Rutgers University; Estados Unidos Fil: Fonseca, Dina M. Rutgers University; Estados Unidos

Members of the sucking louse genus Pedicinus are ectoparasites of cercopithecid primates in Africa, Asia, and Gibraltar. Pedicinus gabonensis n. sp. is described based on adult male and female specimens collected from the mandrill (Mandrillus sphinx) in Gabon. The new species is compared morphologically with other members of the genus Pedicinus, and a nuclear elongation factor 1 alpha gene sequence is provided. Host associations and geographical distributions of the 18 previously recognized species of the genus, and of Pedicinus gabonensis n. sp., are reviewed. Updated identification keys are provided for males and females of all known valid species of Pedicinus.

The objective of this work was to elaborate supporting tools for the correct identification of Scarabaeidae, by an identification key of genera, and a commented list of the species present in Brazilian pastures. A data survey was performed on the specimens deposited in the main Brazilian collection and reported on the recent scientific literature. The distribution of the species was identified in the Brazilian states, based on information on feeding preference, ecological aspects, and potential for faeces removal action. The species were classified according to their importance for pastures, as: high, medium, and low. A key for the identification of the genera and subgenera of Scarabeidae present in the pastures was constructed through the analysis of the external morphology of the species and, when needed, by the analysis of sexual traits. Twenty genera and 76 species of scarab beetles were recorded for Brazilian pasturelands, among which Dichotomius bos, Dichotomius nisus, Trichillum externepunctatum, Ontherus appendiculatus, Onthophagus aff. hirculus, and Digitonthophagus sp. were considered as the most frequent, widely distributed, abundant, and important. The dichotomous key will contribute to the identification of the genera and subgenera of dung beetles (Scarabaeidae: Scarabaeinae) occurring in the Brazilian pastures.

The dioecious seagrass species Halophila stipulacea reproduces mainly through fast clonal growth, underlying its invasive behavior. Here, we provide morphological evidence to show that the first findings of fruits in the Caribbean were misidentified. Consequently, H. stipulacea reproduction is likely still only asexual in the Caribbean. Therefore, we introduce an identification key of H. stipulacea reproductive structures to encourage careful identification and quantification throughout its invasive range. Until large-scale seed production in invaded habitats is reported, the apparent low rate of sexual reproduction needs to be considered in current studies investigating the invasion capacity of this species.

Laticorophium baconi (Amphipoda, Corophiidae) was recorded for the first time in European marine waters from buoy fouling communities at the Sant Carles de la Rapita marina (Alfacs Bay, Eastern Mediterranean Spanish coast). Presence of juveniles, adult males, brooding and ovigerous females were indicative of a well-established population. An entire description of the species, together with a dichotomous key to Corophiini genera characterized by urosome segments fused with uropod 1 ventrally inserted, are provided. This record supports the view that L. baconi may have been overlooked and/or potentially confused with otherCorophiini species such as Apocorophium acutum in previous studies

The genus Pteranabropsis is reviewed. Diagnostic characters for the superficially similar species of the genus are discussed. An extended key to the species is provided. Six new species are described: P. angustasp. nov., P. cuspissp. nov., P. bavisp. nov., P. copiasp. nov., and P. pusillasp. nov. from northern Vietnam, and P. guadunsp. nov. from the Wuyishan Mountains in China. Types and all other specimens from Vietnam are stored in ISNB Brussels; those from Wuyishan in ZFMK Bonn.

A history of the description of the 50 valid species ofNarellais given, beginning with the first species described in 1860. To help differentiate the various species, a tabular and a polychotomous key are provided. The species in the keys are arranged using nine characters or character sets that are believed to be of value at the species level. New characters or new significance given to previously described characters used in our keys include: 1) the nature of the dorsolateral edge of the basal scale, being ridged or not, 2) the thickness of the body wall scales, and 3) the arrangement of the coenenchymal scales (imbricate or mosaic), their thickness (thin or massive), and their outer surface ornamentation (ridged or not). All characters used in the keys are illustrated.

The American genus Neonella Gertsch, 1936 consists of very small jumping spiders whose biology is not well known. The genus currently includes eleven valid species, of which eight are known from both sexes and two are only known from one sex. This paper describes and illustrates a new species Neonella acostae sp. n., demonstrates male palpal variation in Neonella montana Galiano, 1988, and provides some information on the ecology of three sympatric species. New records of N. montana and N. minuta Galiano, 1965 are reported. Because the previously described species of Neonella were well illustrated and diagnosed, a dichotomous key to males is given along with genital illustrations of both sexes for all known species. Fil: Rubio, Gonzalo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; Argentina Fil: Argañaraz, Carina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (P). Grupo Vinculado Centro de Relevamiento y Evaluación de Recursos Agrícolas y Naturales; Argentina Fil: Gleiser, Raquel M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (P). Grupo Vinculado Centro de Relevamiento y Evaluación de Recursos Agrícolas y Naturales; Argentina

Este artículo contiene 7 páginas, 3 figuras., Knowledge of the Haplosyllis species in the Saudi Arabian Red Sea is rather limited, since the so-called cosmopolitan Haplosyllis spongicola and Haplosyllis djiboutiensis apparently present all along the region are the only reported species. However, both are revealed to be species-complexes, the former mostly composed of European species and the later distributed in the Indo-Pacific area. Recently, several new species have been described following more comprehensive taxonomic studies in the respective areas. Haplosyllis leylae sp. nov. can be framed within the Bdjiboutiensis^ complex. The new species, which is herein fully described and illustrated, can be clearly distinguished by the combined presence of numerous small dorsal granules, the low number of articles on each dorsal cirrus, and the chaetal morphology. A dichotomous key of the Indo-Pacific species of Haplosyllis and new information on Haplosyllis eldagainoae are also included., This paper has been partially supported by the projects CTM2014-57949-R funded by the Spanish Ministry of Economy and Competitiveness, and the projects CTM2010- 22218 and CTM2013-43287-P funded by the Spanish State Research Plan, and the Consolidated Research Group of Marine Benthic Ecology of the Generalitat de Catalunya (2014SGR120).

Nymphaea has seven species already catalogued in the flood prone areas of the Brazilian Pantanal. However, some species remain difficult to identify and descriptions of the anatomy of vegetative organs are an important tool for infrageneric separation to aid in group taxonomy. The species collected in the Pantanal and prepared according to the usual techniques for anatomical studies showed similar structural characteristics, and data on the arrangement of vascular bundles in the midrib and petiole, as well as the form and distribution of sclereids, were consistent. Nymphaea oxypetala stands out from the other evaluated species for having a greater number of differential characters, including angular collenchyma and the absence of bicollateral bundles in the petiole. Nymphaea lingulata stands out as the only species to feature bicollateral bundles in the leaf blade. The results, summarised in the dichotomous key, facilitate the identification of species that use the flower as the main differentiation, but are in a vegetative stage.

The male genital sclerites of cockroaches of genus Muzoa Hebard, 1921 are described for first time and the new species Muzoa curtalata sp. n. is described and ilustrated. A dichotomous key to identify the species of genus Muzoa is given.

Presently the only keys available for identification of genera of Anthonomini are limited to those of the United States of America and Canada. A dichotomous key is presented to identify all genera of Mexican and Central American Anthonomini. Previous keys do not include the genera Achia, Botanebius, Loncophorus, Loncophorellus and Melexerus. A brief synopsis is given for each genus and photographs of representative species are included.

A taxonomic revision of the New Caledonian species of Arsipoda Erichson, 1842 is provided. This group includes 21 species, of which 14 are new to science: Arsipoda atra sp. nov., A. communis sp. nov., A. doboszi sp. nov., A. elongata sp. nov., A. gomezzuritai sp. nov., A. gressitti sp. nov., A. longifrons sp. nov., A. montana sp. nov., A. paniensis sp. nov., A. povilaensis sp. nov., A. punctata sp. nov., A. rutai sp. nov., A. transversa sp. nov. and A. wanati sp. nov. A key for the identification, with figures of habitus, main diagnostic characters, and genitalia is supplied. The range of host plants for these species is extraordinarily broad, and a significant number of them feed on pollen. Crepicnema Scherer, 1969, close to Arsipoda , is also investigated and maintained as a separate genus, and the following synonymies and combination are proposed: Crepicnema parvula (Jacoby, 1885) comb. nov. = Chaetocnema tenimberensis Jacoby, 1894 syn. nov., = Arsipoda salomonensis Bryant, 1941 syn. nov. The phylogenetic analysis, including also A. bifrons Erichson, 1842 and Crepicnema , confirms some trends in distribution patterns of the endemic New Caledonian fauna, and highlights the necessity of further studies to clarify the relationships between Arsipoda and related genera.

Pseudobranchiomma (Sabellidae, Annelida) is a small and heterogeneous group of fan worms found in shallow marine environments and is generally associated with hard substrates. The delineation and composition of this genus is problematic since it has been defined only by plesiomorphic characters that are widely distributed among other sabellids. In this study we have combined morphological and molecular (mitochondrial and nuclear DNA sequences) data to evaluate species diversity in Australia and assess the phylogenetic relationships of these and other related sabellids. Unlike morphological data alone, molecular data and combined datasets suggest monophyly of Pseudobranchiomma. In this study, a new species of Pseudobranchiomma is described and three others are considered as potential unintentional introductions to Australian waters, one of them reported for the first time for the continent. Pseudobranchiomma pallida sp. n. bears 4–6 serrations along the radiolar flanges, lacks radiolar eyes and has uncini with three transverse rows of teeth over the main fang. In the new species the colour pattern as well is characteristic and species specific. Copyright María Capa, Anna Murray. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Reticulitermes nelsonae, a new species of Rhinotermitidae (Isoptera) is described based on specimens from Sapelo Island, GA, Thomasville, GA, Havelock, NC, and Branford, FL. Adult (alate) and soldier forms are described. Diagnostic characters are provided and incorporated into a supplemental couplet of a dichotomous key to the known species of Reticulitermes found in Georgia, USA.

A new species, Gloiocephala cerkezii, is described from Croatia. It is characterized by a pale brown to rusty brown pileus, an elongated central to slightly eccentric stipe, vein-like lamellae, large and elongate spores, subcapitate to capitate cystidia, a gelatinized trama, and the absence of hairs on the pileus and stipe. The description is accompanied by black and white photograph of basidiocarps and line drawings of microscopic elements. G. cerkezii is compared to closely related species, and a dichotomous key to European species of the genus Gloiocephala is provided. A new combination Gloiocephala pseudocaricis is made.

A new species of Selenipedium (Orchidaceae: Cypripedioideae) from northern Ecuador is described here and its affinities are discussed. A key to the known species of the genus is provided. A new species of Selenipedium (Orchidaceae: Cypripedioideae) from northern Ecuador is described here and its affinities are discussed. A key to the known species of the genus is provided.

The taxonomy of the family Desmodoridae (Nematoda: Desmodorida) is partially revised based on morphology. The diagnoses of the Desmodoridae and the subfamilies Desmodorinae and Spiriniinae are emended to accommodate re-analyzed morphological features. Eight known species are redescribed and the implication of the new findings for the taxonomy of the group is discussed. Amphispira and Metadesmodora are confirmed as genera inquirendae. Alaimonema and Sigmophoranema, and their corresponding type species, are proposed as inquirendae due to poor descriptions of the type material. The other three species of Sigmophoranema are transferred to the genus Onyx because they bear the diagnostic features of this group: spear-like dorsal tooth and s-shape precloacal supplements. Echinodesmodora, Paradesmodora and Stygodesmodora are transferred to the Spiriniinae based on the absence of a head capsule and on the amphidial fovea being surrounded by cuticle striation. Paradesmodora toreutes is transferred to the genus Acanthopharyngoides as A. toreutes comb. nov. The genus Onepunema does not fit in the family Desmodoridae because of diorchic males; thus, it is regarded as taxon incertae sedis. Lists of valid genera for the two subfamilies are provided. A dichotomic key for the identification of the 14 genera within the Spiriinae is provided.

Two new species of the family Trefusiidae, viz., Trefusia piperata sp. nov. and Trefusialaimus idrisi sp. nov., are described from the crest of the Chatham Rise, Southwest Pacific Ocean (350 m water depth). The present study provides the first species records for this family in the region. Trefusia and Trefusialaimus comprise twenty and three valid species, respectively. A key to males of Trefusia is provided.

Este estudio se orientó para establecer la composición faunística de ácaros acuáticos de diferentes regiones de Colombia. Los ácaros principalmente fueron extraídos de colecciones. De las 11 colecciones revisadas se encontraron individuos en 8 de ellas. Se revisaron un total de 1220 individuos, 990 de estos registrosfueron identificados como ácaros acuáticos (Hydrachnidiae). Se encontraron un total de 17 familias (3 nuevos para Colombia). Se identificaron un total de 44 géneros (12 nuevos para Colombia, 3 nuevos para la ciencia).La familia más abundante es Hygrobatidae con 349 individuos, seguida de Arrenuridae con 151 individuos y Unionicolidae con 150 individuos. Hygrobatidae fue también la familia que se encontó más ampliamente distribuida (seis departamentos), seguida por Anisitsiellidae y Limnesiidae (cinco departamentos). Los departamentos con mayor de riqueza son Chocó con 11 familias y 22 géneros, seguido de Caldas con 9 familias y 19 géneros, Meta con 8 familias y 15 géneros, y Cundinamarca con 7 familias y 12 géneros.Se identificaron de 48 especies (9 son nuevos reportes para Colombia y 32 son nuevas especies para la ciencia).Además se presenta una clave dicotómica para las familias y géneros de ácaros acuáticos presentes en Colombia y se mencionan algunos aspectos ecológicos y geográficos. Por ultimo, se presenta una clave dicotómica para todas las especies de la familia Rhynchohydracaridae, incluyendo dos nuevas especies de Colombia. Abstract. This study was aimed to set up the water mites’ composition from different regions of Colombia. Mites were extracted from collections. Water mites were found in 8 of the 11 collections reviewed. A total of 1220 mites were identified, 990 as water mites. A total of 17 families were found (3 new records for Colombia). A total of 44 genera were identified (12 new reports for Colombia , 3 are new to science ).In this work is reported water mites from eight Departments of Colombia. Hygrobatidae was the most abundant family with 349 water mites, followed by Arrenuridae with 151 and Unionicolidae with 150. Family Hygrobatidae also showed the widest geografical distribution in Colombia in six Departments, followed by Limnesiidae and Anisitsiellidae in five Departments. The Departments with highestrichness were Chocó with 11 families and 22 genera, followed by Caldas with 9 families and 19 genera, Meta with 8 families and with 15 genera, and Cundinamarca with 7 families and 12 genera. 48species were identified (9 are new records for Colombia and 32 species are new to science). Here is also include a dichotomous key to families and genera of water mites in Colombia. Some ecological and geographical aspects are mentioned. Furthermore a dichotomous identification key for all species of the family Rhynchohydracaridae is presented including two new species from Colombia. Maestría

Los gorgojos (Coleoptera: Curculionoidea) de America del Sur se clasifican actualmente en las siguientes familias y subfamilias: Nemonychidae (Rhinorhynchinae), Anthribidae (Anthribinae), Belidae (Belinae y Oxycoryninae), Attelabidae (Attelabinae y Rhynchitinae), Brentidae (Apioninae y Brentinae), Caridae (Carinae) y Curculionidae (Erirhininae, Dryophthorinae, Entiminae, Aterpinae, Gonipterinae, Rhythirrininae, Thecesterninae, Eugnominae, Hyperinae, Curculioninae, Cryptorhynchinae, Mesoptiliinae (= Magdalidinae), Molytinae, Baridinae, Lixinae, Conoderinae (= Zygopinae), Cossoninae, Scolytinae y Platypodinae). En la presente contribucion se brinda una clave dicotomica para la identificacion de las siete familias y 28 subfamilias de Curculionoidea sudamericanos, y para varias (21) tribus de Curculioninae y Molytinae. Estas tribus son Curculionini, Anthonomini, Ceutorhynchini, Derelomini, Otidocephalini, Erodiscini, Camarotini, Piazorhinini, Prionobrachiini, Smicronychini, Rhamphini y Tychiini, dentro de Curculioninae, e Hylobiini, Pissodini, Conotrachelini, Cleogonini, Sternechini, Pacholenini, Cholini, Petalochilini y Amalactini, dentro de Molytinae. La mayoria de estas tribus han sido clasificadas como subfamilias en los esquemas tradicionales. La clave se basa principalmente en caracteres morfologicos externos, e incluye ademas datos de la genitalia, piezas bucales, y rasgos biologicos de las especies. El trabajo provee definiciones e ilustraciones de los caracteres diagnosticos utilizados en la clave

A new species of Desmioza Enderlein, 1937 from Argentina is described: Desmioza biancae n.sp. Adults were collected with Malaise traps in the Nahuel Huapi National Park, in the Argentinean Patagonia. This is the third species of the genus described in the Andean region, Patagonian subregion. A dichotomous key for the identification of all known species of the genus is included. Fil: Omad, Guillermo Hugo. Universidad Nacional de la Patagonia ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina

A taxonomical study of 15 Rhoicosphenia species based on light and scanning electron microscope was performed. The genus Rhoicosphenia is characterized by frustule heterovalvy, with a fully developed raphe on the concave valve (referred also as R valve) and reduced raphe on the convex valve (referred as D-valve). One of the most frequently reported species, R. abbreviata, is characterized by narrow, linear valves with low stria density. In contrast, Rhoicosphenia macedonica has broadly clavate valves with a high stria density. According to valve shape R. macedonica is similar to the widely distributed marine species R. marina, but the latter has broader valves (8.5-11 μm wide) and a lower stria density. Both, R. tenuis and R. baicalensis have similar valve sizes and shapes, but the latter is characterized by a lower stria density on the D-valve. Rhoicosphenia baltica is a brackish water species with protracted and subcapitate base poles, narrower valves and lower stria density compared with R. marina. The main distinctive features of R. flexa are the absence of a raphe branch on the head pole of the convex D-valve, and coarsely punctate striae. R. genuflexa has isopolar, linear valves. Four other species have different combinations of characters (valve size, shape and stria density) compared to above mentioned species, and their formal descriptions are provided. Rhoicosphenia lacustris sp. nov. is characterized by larger and broadly clavate valves, densely spaced striae and elongated areolae. Rhoicosphenia affinis sp. nov. has broadly lanceolate valves with attenuated and slightly protracted head pole with a higher stria density compared to R. abbreviata. Rhoicosphenia adriatica sp. nov. is a brackish water species having narrow, linear valves, with a high stria density. Finally, R. omblaensis sp. nov. has a characteristic central area, which appears as a narrow hyaline area around the central pores.