Northwestern Venezuela Research Articles

New Galumnidae (Acari, Oribatida) from the Merida and Zulia States, Venezuela

Three new species of the family Galumnidae (Oribatida)—Sacculogalumna zuliaensis sp. nov., Pergalumna (Pergalumna) convergens sp. nov. and Carinogalumna meridaensis sp. nov.—are described, based on adults collected from cloud forest in the Merida State, Western Venezuela, and pasture meadow in the Zulia State, Northwestern Venezuela. The genera Sacculogalumna and Carinogalumna are registered in the Venezuelan fauna for the first time. Identification keys to the known species of Sacculogalumna and Carinogalumna are provided.

Application of herbivore ecometrics to reconstruct Neogene terrestrial palaeoenvironments in Falcón, Venezuela

Despite its important position close to the Isthmus of Panama, and abundance of fossil localities, the palaeoenvironment of the Falcón Basin in northwestern Venezuela has been understudied. The basin includes a sequence containing 6 terrestrial fossil assemblages, of which 5 are well-sampled enough for palaeoenvironmental reconstruction. Here we use these assemblages as a test case for taxon-free approaches in the Neotropics, that have been used in studies elsewhere, including dental functional traits, body mass and mesowear. Mesowear reveals browsing and grazing diets from the Late Miocene to the Late Pleistocene, and though the toxodontids (the most abundant mammalian herbivores) show a consistent browsing signal, other approaches support an environment which was largely more open than previously suggested. We find limited evidence for any dramatic climatic shift, instead finding more gradual changes in precipitation and tree cover. Ultimately, we find enough consistency in our results with those of other proxies to suggest that the methods employed here could potentially be applied to other localities in South America.

Osteology of the skull of the blind snake Helminthophis flavoterminatus (Peters, 1857) (Serpentes, Anomalepididae)

The blind snake Helminthophis flavoterminatus (Peters, 1857) is a species of Anomalepididae with distribution throughout northwestern Venezuela and western Colombia. Its osteology is poorly known, and thus this study presents information on its skull structure based on High-Resolution X-Ray Computed Tomography. The absence of the supraoccipital bone can be used for the determination of H. flavoterminatus in relation to its congeners, Helminthophis frontalis (Peters, 1860) and Helminthophis praeocularis Amaral, 1924.

Description of Bisbalus, a New Genus for the Gray Brocket, Mazama cita Osgood, 1912 (Mammalia, Cervidae), as a Step to Solve the Neotropical Deer Puzzle

The Neotropical deer genus Mazama is characterized by homoplastic morphological characters, a high karyotypic diversity, and a polyphyletic condition. The species of the genus have been recovered into two multigeneric lineages, the subtribes Odocoileina and Blastocerina, of the tribe Odocoileini (New World deer) in the family Cervidae. Within the Blastocerina, gray brockets include two non-sister species, Subulo gouazoubira, occurring south of the Amazon region, and Passalites nemorivagus, occurring in the Guianas and in the Amazon region. We clarify the taxonomic status and phylogenetic position of Mazama americana citus Osgood, 1912 (referred to as either S. gouazoubira or P. nemorivagus by other authors). We collected a topotype of M. a. citus from the eastern shore of Lake Maracaibo, Venezuela, characterize it morphologically and cytogenetically (conventional banding and fluorescence in situ hybridization), and carry out a phylogenetic analysis of its whole mitogenome and Cytb alongside two additional specimens of M. a. citus from northwestern Venezuela. Our analyses reveal the topotype to be a large gray brocket with a cinnamon band above the eyes and 2n = 61 and FN = 70 karyotype. Using cattle whole chromosome painting and bacterial artificial chromosome X probes, we determined its karyotype to differ in at least 10 rearrangements from that of S. gouazoubira. Bayesian inference recovers M. a. citus within the Blastocerina subtribe, separated phylogenetically from other gray brockets (100% branch value), revealing the Osgood’s gray brocket to be a valid species that should be assigned to a new genus. We propose the generic name Bisbalus, with Bisbalus citus (Osgood, 1912) as the type species.

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios.

We document the first occurrence of Sigmodontinae (Mammalia, Rodentia, Cricetidae) from the Pliocene of northern South America, from the San Gregorio Formation of northwestern Venezuela. The recovered isolated molars are identified as Oligoryzomys sp. and Zygodontomys sp., two currently widespread sigmodontines in South America. These records constitute the oldest representatives of these genera, potentially new species, and the first Pliocene occurrence for Oryzomyini and the whole subfamily outside Argentina. Hypotheses on the historical biogeography of sigmodontines have been constructed almost exclusively using genetic data and the fossils we report provide a new kind of evidence. The occurrence of Oligoryzomys sp. and Zygodontomys sp. in Venezuela provides novel information for the diversification models suggested for Oligoryzomys, by supporting a potential eastern corridor of open environments from northern to southern South America. The presence of sigmodontines from the locality home of the new reports, Norte Casa Chiguaje, is consistent with the palaeoenvironmental conditions originally proposed for it based on mammals and botanical records, being characterized as mixed open grassland/forest areas surrounding permanent freshwater systems. The new sigmodontine evidence is used to discuss the putative scenarios of the ancient evolution of the subfamily in South America, favouring a model in which open areas (savannahs) to the east of the Andes played crucial role aiding or obstructing Late Miocene-Pliocene sigmodontine dispersion southwards.

Nutrients and trace elements of semi-arid dwarf and fully developed mangrove soils, northwestern Venezuela

Mangrove forests are characterized by a high carbon storage capacity. Anthropogenic activities and the climate change are threatening the stability of these ecosystems, specially those that are surviving on extreme environmental conditions, representing the most susceptible groups. This study aims to understand the geochemical differences of soils of mangrove forest with diverse degree of development of Rhizophora mangle and Avicennia germinans, located in two semi-arid regions from the Falcon state, Venezuela. The soil samples were collected in Punta Caimán region (dwarf mangroves of less than 2 meters height) and Boca de caño lagoon (fully developed mangroves of up to 8 meters height). The trace elements and macronutrients were determined in two sequential extraction, first with 1M HCl followed by an extraction with ultrapure grade HNO_{3}. Results showed that, in general, dwarf mangroves have limited capability to accumulate organic matter in the soil (average TOC of 0.6 pm 0.2%) and that the sampled surface soils from the dwarf mangrove region had no differences with deeper material. On the other hand, the TOC of soils dominated by developed mangroves is 6 pm 2 %, representative of semi-arid conditions. Moreover, the soils dominated by dwarf mangroves are characterized high concentrations of trace elements related to the chalcophile group. The difference in soil chemistry between Rhizophora mangle and Avicennia germinans becomes significant when mangroves are fully developed. Finally, soils of dwarf mangrove forests presented a greater concentration of trace elements than soils of fully developed mangroves, which might be due to a different sediment source, to an anthropogenic influence or to the difference in organic matter.

Damaged glyptodontid skulls from Late Pleistocene sites of northwestern Venezuela: evidence of hunting by humans?

The Muaco and Taima-Taima sites, in Falcón State of northwestern Venezuela, are among the earliest sites of human occupation in South America containing artifacts associated with preserved megafaunal remains and dating between 19,810 and 15,780 calybp. Here we report novel visual and CT scanning analysis of six glyptodont skulls of Glyptotherium cf. cylindricum from these sites, of which four exhibit distinct and similar patterns of breakages in the fronto-parietal region that suggest intentional blows by direct percussion by humans, with fractures not being diagenetic but instead antemortem or transmortem. This hypothesized and unreported hunting technique focused in an area of the skull where the cephalic shield becomes thin, thus increasing the effectiveness of the blow. From Taima-Taima other glyptodont remains included an inverted carapace, also previously reported as probable evidence of human–glyptodont interaction during the latest Pleistocene. We estimated that roughly 150-170 Kg of potentially accessible muscles and fat of an adult Glyptotherium cylindricum could be used as food sources.

Seasonal trends of Cyclospora cayetanensis infections in a community of Falcon State, Northwestern Venezuela.

Cyclosporiasis has a marked seasonality. Few community-based studies have addressed this issue and there are no reports from Venezuela. A study was conducted to determine the seasonal variation of infection in a community from Falcon State, Venezuela. A sample of 732 individuals was collected for 1 y. Stools were examined with modified Ziehl-Neelsen carbolfuchsin staining of ethyl acetate-formalin concentrates and ultraviolet epiflorescence of wet mounts. Cyclospora prevalence was 9.9% (73/732) with monthly variation from 0% to 35.3%. A trend of increased infections coinciding with the rainy time was observed (p<0.001). Cyclosporiasis is common in this area with high endemicity during the rainy periods.

The taxonomic status of Myotis nesopolus larensis (Chiroptera, Vespertilionidae) and new insights on the diversity of Caribbean Myotis.

Myotisnesopolus currently comprises two subspecies. The nominate subspecies (M.n.nesopolus) occurs on the Caribbean islands of Curaçao and Bonaire, Netherlands Antilles, whereas M.n.larensis is known from mainland South America in northeastern Colombia and northwestern Venezuela. Our Maximum Likelihood phylogenetic analyses of cytochrome-b gene sequences recovered M.nesopolus as a paraphyletic group, with M.n.nesopolus and M.n.larensis as non-sister lineages. The haplotype network indicates that these two subspecies do not share any haplotypes and are in different evolutionary trajectories. Additionally, these two subspecies can be distinguished on the basis of qualitative and quantitative morphological traits. This pattern supports the recognition of M.nesopolus and M.larensis as full species. Our results also reveal that the assemblage of Caribbean Myotis do not form a monophyletic group. Caribbean species are phylogenetically close to mainland species from northern South America and Central America, suggesting that colonization of Caribbean islands happened multiple times.

Uso de enmiendas en la producción de maíz para ensilaje con riego orgánico mineral

Introducción. La situación del manejo inadecuado de los recursos en los sistemas productivos de maíz, estimula el desarrollo de nuevas estrategias orientadas al mejoramiento de la calidad, fertilidad y la salud del suelo junto a su entorno. Entre ellas, el uso de enmiendas para solventar las limitaciones presentadas en el crecimiento y desarrollo del cultivo como el problema de tipo antropogénico que afecta principalmente la calidad del suelo (alcalinidad, salinidad). Objetivo. Evaluar el efecto de 3 enmiendas sobre el crecimiento y desarrollo del cultivo de maíz con un plan de fertilización orgánico mineral. Materiales y métodos. El ensayo se estableció en la Finca El Danubio ubicada en Duaca al noroccidente de Venezuela con un diseño experimental de bloques completamente al azar con 6 tratamientos: T1: compost Don Manuel (CDM); T2: compost Minco Fértil (CMF); T3: Fosfoyeso (FY); T4: CDM+FY; T5: CMF+FY y control sin enmiendas. Las mismas fueron aplicadas manualmente en el surco de siembra, mientras que la fertilización orgánica con 16 productos y mineral (urea) fueron aplicadas a través del riego a partir de los 15 y 22 días después de la siembra. Resultados. Los resultados encontrados mostraron que el preparado de compost fórmula Minco fértil incrementó el crecimiento, altura de la planta, número de hojas y área foliar. Los mayores rendimientos de maíz para ensilaje y materia seca total fueron obtenidos con el preparado de compost Don Manuel y Minco fértil. No se encontró respuesta a la aplicación de las enmiendas orgánicas en las variables nutricionales de la planta. Conclusión. Se puede producir maíz forrajero con enmiendas orgánicas con efectos positivos en el crecimiento y producción del cultivo.

A review of the genus Mimicoclytrina Bellamy, 2003 (Coleoptera: Buprestidae) and description of a new species from northwestern Venezuela

The Neotropical genus MimicoclytrinaBellamy, 2003 is revised and a new species from Venezuela, Mimicoclytrina bellamyisp. nov., is described and compared to its most closely related species. A lectotype for Acherusia tristisThomson, 1878 is designated, and the taxon is classified as a subspecies of M. piliventris (Saunders, 1869). Mimicoclytrina piliventris ssp. venezuelica (Cobos, 1980) is placed in synonymy with M. piliventris ssp. tristis (Thomson, 1878). The previously unavailable subgenus name NelsonilaCobos, 1980 is redescribed as a new subgenus Antoniolasg. nov. and a type species is designated. All species of the genus are illustrated, including type specimens. A key to all known taxa is given, together with data on distribution, biology and taxonomic position.

The surface expression of hydrocarbon seeps characterized by satellite image spectral analysis and rock magnetic data (Falcon basin, western Venezuela)

Satellite images have been widely used to characterize mineral alteration zones in surface rocks affected by hydrocarbons' upward seepage. Likewise, magnetic surveys over oil fields have been employed for similar purposes. This work integrates satellite image spectral analyses with rock magnetic and geochemical data (i.e., mass-specific magnetic susceptibility χ, saturation isothermal remanent magnetization SIRM, analysis of SIRM acquisition curves, absorption spectro-radiometry, and X-ray diffraction analyses). The target area was an oil-prospective region in northwestern Venezuela (Falcon Basin) swarmed by hydrocarbon seeps. The study's main goal was to depict the spatial extension and vertical reach of the hydrocarbon-mediated alteration produced by these seeps and gain some knowledge about the processes involved in the subsequent mineral changes. Multispectral and hyperspectral satellite images showed three hydrocarbon-induced diagenetic anomalies (HIDAs) associated with undifferentiated clays and kaolinite, and low dolomite content. A simple weathering model was suggested combining the likely effects of the ascending seepage of oil and gas with the seasonal alternation of leaching and evaporation of meteoric waters. This model explains the magnetic enhancement with depth due to Fe oxides and sulfides' formation by reducing and oxidizing events. A non-supervised Two-Step Cluster Analysis (TSCA) was applied to integrate geochemical and rock magnetic properties with satellite images. The input variables were log SIRM and proxies of undifferentiated clays and dolomite concentrations obtained from the band-ratio ASTER images. The TSCA yields three clusters associated with different alteration levels in the top and low (0.3–1 m) soils and sediments. By mapping the class membership of each sampling site, for both depth levels, it was possible to obtain a broad view of the synergistic change of these combined properties, not only over the whole extent of the study area but also from top to bottom of the weathered sequence. This case study illustrates the potential of such an integrated method as an oil exploration tool, and a means to assess the level and scope of the environmental impact produced by hydrocarbon seepage on terrestrial ecosystems.

New cranial and postcranial elements of Mourasuchus (Alligatoroidea: Caimaninae) from the late Miocene of Venezuela and their palaeobiological implications

ABSTRACT A partial skeleton of Mourasuchus, one of the most peculiar crocodylians of all time, that includes cranial and postcranial elements recovered from the late Miocene bone-beds of the Urumaco Formation (northwestern Venezuela) is herein described. Based on the presence of tall squamosal eminences, we assigned it to Mourasuchus arendsi. To provide an empirical assessment of the palaeobiological affinities of Mourasuchus, we performed estimations of the body mass and body length based on several Mourasuchus skull measurements, and an analysis of death roll capability. Our results indicate that Mourasuchus was indeed a large crocodylian, with a body length bigger than 9 m and weighed more than 4 tons. We find that Mourasuchus arendsi was incapable of executing the ‘death roll’ as a feeding behaviour and as such was unable to predate giant mammals, which are relatively common in the Urumaco Formation. Finally, the specimen includes a slender humerus, which may indicate that Mourasuchus had weak forelimbs and would spend more time in the water.

Two new species of Dendrophthora (Viscaceae) from the Venezuelan Andes.

Two new species of Dendrophthora Eichler (Viscaceae) from northwestern Venezuela are described and illustrated. Both mistletoes, D.apiculata Canelón et al., sp. nov. and D.coronata Canelón et al., sp. nov., are confined to subpáramo and páramo ecosystems of the Venezuelan Andes and are, at present, only known from Guaramacal National Park (Portuguesa and Trujillo states). Ecological aspects and possible taxonomic affinities are discussed. A distribution map also is presented.

Lithospheric Structure of Northwestern Venezuela From Wide‐Angle Seismic Data: Implications for the Understanding of Continental Margin Evolution

AbstractNorthwestern Venezuela is located in the complex deformation zone between the Caribbean and South American plates. Several models regarding the lithospheric structure of the Mérida Andes have been proposed. Nevertheless, they lack relevant structural information in order to support the interpretation of deeper structures. Therefore, a 560‐km‐long refraction profile across the northern part of Mérida Andes, oriented in a NNW direction, covering areas from the Proterozoic basement in the south, to both Paleozoic and Meso‐Cenozoic terranes of northwestern Venezuela to the north, is analyzed in this contribution. Thirteen land shots were recorded by 545 short‐deployment seismometers, constraining P wave velocity models from first‐arrival seismic tomography and layer‐based inversion covering the whole crust in detail, with some hints to upper mantle structures. The most prominent features imaged are absence of a crustal root associated to the Mérida Andes, as the Northern Andes profile is located marginal to the Andean crustal domain, and low‐angle subduction of the Caribbean oceanic slab (~10–20°) beneath northwestern South America. Further crustal structures identified in the profile are (a) crustal thinning beneath the Falcón Basin along the western extension of the Oca‐Ancón fault system interpreted as a back‐arc basin; (b) suture zones between both the Proterozoic and Paleozoic provinces (Ouachita‐Marathon‐related suture?), and Paleozoic and Meso‐Cenozoic terranes (peri‐Caribbean suture) interpreted from lateral changes in seismic velocity; and (c) evidence of a deep Paleozoic(?) extensional basin, underlying thick Mesozoic and Cenozoic sequences (beneath the Guárico area).

Unveiling species diversity in collared frogs through morphological and bioacoustic evidence: a new Mannophryne (Amphibia, Aromobatidae) from Sierra de Aroa, northwestern Venezuela, and an amended definition and call description of M. herminae (Boettger, 1893).

Species diversity in collared frogs of the genus Mannophryne is presumed to be underestimated due to the paucity of external morphology characters, but combining morphology with bioacoustics and other lines of evidence has shown to be useful in delimiting species of this group. Herein we describe a new species of Mannophryne from Sierra de Aroa in northwestern Venezuela. The new species is morphologically similar to M. herminae but is readily recognized by its strikingly different advertisement call. It also can be distinguished from all its congeners by the unique combination of its small body size, general color pattern, basal toe webbing, and advertisement call consisting of long trills of single tonal notes emitted at a rate of 2-3 notes/s. Additionally, to facilitate future diagnosis of undescribed species related to M. herminae, we amend the definition of the latter, describe in detail its advertisement call, and redefine its known distribution range. The new species increases the number of described species of Mannophryne to 20.

Rubiacearum Americanarum Magna Hama Pars XL: Overview ofPalicoureasect.Egenses, with Two New Species and a New Subspecies (Palicoureeae)

The newly circumscribed group Palicourea Aubl. sect. Egenses C. M. Taylor includes 13 species found in South America in the Amazon and Orinoco basins, the Guayana Highlands, northwestern Venezuela, and the central Andes, often on nutrient-poor (oligotrophic) soils, and is diagnosed by features of its leaves, inflorescences, and fruits. Its species are separated mainly by details of stipules, inflorescence arrangement, bracts, and flower and fruit size, as outlined in a key, and have different ranges and some unusual morphological features as detailed for each. Newly published here are the combination P. moyobambana (Standl.) C. M. Taylor, the new species P. articulata C. M. Taylor from southeastern Colombia and P. flagellifera C. M. Taylor from Amazonian Colombia, and the new subspecies P. egensis subsp. zuliana C. M. Taylor from northwestern Venezuela.

The Neogene Record of Northern South American Native Ungulates

South America was isolated during most of the Cenozoic, and it was home to an endemic fauna. The South American Native Ungulates (SANUs) exhibited high taxonomical, morphological, and ecological diversity and were widely distributed on the continent. However, most SANU fossil records come from high latitudes. This sampling bias challenges the study of their diversity dynamics and biogeography during important tectonic and biotic events, such as the Great American Biotic Interchange, the faunal exchange between North and South America after the formation of the Isthmus of Panama. We describe new SANU remains from the Neogene of the Cocinetas (northern Colombia) and Falcon (northwestern Venezuela) Basins. In the Cocinetas Basin, the middle Miocene fauna of the Castilletes Formation includes Hilarcotherium miyou sp. nov. (Astrapotheriidae), cf. Huilatherium (Leontiniidae), and Lambdaconus cf. L. colombianus (Proterotheriidae). The late Pliocene fauna of the Ware Formation includes a Toxodontinae indet. and the putative oldest record of Camelidae in South America. In the Falcon Basin, the Pliocene/Pleistocene faunas of the Codore and San Gregorio Formations include Falcontoxodon aguilerai gen. et sp. nov. and Proterotheriidae indet. We provide a phylogenetic analysis for Astrapotheriidae and Toxodontidae. The new data document a low-latitude provinciality within some SANU clades (e.g., Astrapotheriidae, Leontiniidae) during the middle Miocene. This contrasts with the wide latitudinal distribution of clades of other mammals recorded in the fauna, including the sparassodont Lycopsis padillai, the sloth Hyperleptus?, and the proterotheriid Lambdaconus cf. L. colombianus. The Pliocene/Pleistocene tropical faunas from northern South America are characterized by the predominance of native taxa despite their proximity to the Isthmus of Panama (fully emerged by that time). Only one North American ungulate herbivore immigrant is present, a cf. Camelidae indet. The Pliocene and early Pleistocene faunas suggest that environmental changes and biotic interactions affected the diversity dynamics and biogeographic patterns of SANUs during the Great American Biotic Interchange.

Sustainability and design assessment of rural hybrid microgrids in Venezuela

Nowadays, 1.2 billion people lack access to electricity, mainly in rural areas of developing countries. In particular, 22 million people do not have electricity in Latin America and many governments are developing rural electrification programs to deal with this situation. Off-grid hybrid microgrids based on renewable energy are an efficient option for providing dispersed rural populations with access to electricity. However, microgrids are still a minority option, as governments of developing countries generally consider them expensive and not effective. In this context, the evaluation of projects based on hybrid microgrids is required in order to improve the knowledge about these technologies. In this paper, 13 microgrid projects in north-western Venezuela are presented and their environmental, technical, socioeconomic and institutional dimensions of sustainability are evaluated. For this purpose, an evaluation methodology based on some ad hoc criteria is developed, assessed by means of technical visits, semi-structured interviews and 106 surveys of technical operators and beneficiaries. The results show that microgrids can satisfy the energy needs of the population, while promoting technological change towards the use of more sustainable technologies. In addition, the key aspects for strengthening projects’ sustainability are highlighted.

Gryposuchus (Crocodylia, Gavialoidea) from the early Miocene of Venezuela

Here, a fragment of a mandible recently discovered in the Cerro Zamuro site (Castillo Formation, Lara State, northwestern Venezuela) is assigned to the giant gavialoid Gryposuchus. This specimen, recovered from putative brackish environments of the early Miocene (~18 Ma) age, is unequivocally the earliest record of the genus in South America. Gryposuchus, together with the other gryposuchine previously recognized from the Castillo Formation, Siquisiquesuchus venezuelensis, increases the early Miocene taxonomic diversity of the group in the northern Neotropics. This new information from the Castillo Formation supports the conclusion that early gryposuchine evolutionary stages were in coastal, shallow marine or brackish environments, while the presence of some genera, such as Gryposuchus, in middle to late Miocene freshwater environments, is secondary habitat colonization late in the evolution of the clade. Freshwater colonization is probably the result of the gradual adaptation of early marine-adapted gryposuchines to the extensive estuarine-like environments of northern South America lowlands associated with marine transgressions that systematically occurred during the middle Eocene to early Oligocene. This new record is evidence of the wide chronological distribution of Gryposuchus in northern South America, highlighting the importance of this area as the center of origin and radiation of this successful Miocene gavialoid.