A Pliocene-Pleistocene continental biota from Venezuela.

The Pliocene-Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86Sr/88Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.

Reproductive pattern of the large fruit-eating bat, Artibeus amplus (Chiroptera: Phyllostomidae) in the Venezuelan Andes / Patrón reproductivo del murciélago frugívoro grande, Artibeus amplus (Chiroptera: Phyllostomidae) en los Andes venezolanos

Abstract:Bimodal polyestry is the most common reproductive pattern in tropical bats, and it consists in producing one offspring per female twice a year. Reproductive patterns are closely related to rainfall regimes, frequently occurring twice a year in tropical regions. The goal of our study was to determine the reproductive pattern of the large fruit-eating bat, Artibeus amplus Handley, 1987 in a cave in the Venezuelan Andes inhabited by a large, stable colony. Thus, in this study we describe for the first time this important biological aspect of this unknown Neotropical bat species through the examination of external reproductive characteristics of males (inguinal or scrotal testes) and females (pregnant, lactating, post-lactating), based on 211 individuals (120 males and 91 females) captured between September 2008 and August 2009, in Cueva del Parque Las Escaleras, Estado Táchira, Venezuela. During this period of monthly sampling for a full year, most males displayed large scrotal testes, averaging 10 mm maximum length. The examination of females indicated that although pregnancy was first observed in November 2008, it reached a maximum during January and February 2009. Although adult males with scrotal testes throughout the year could imply that females have more than one pregnancy, our results suggested a seasonally monoestrous reproductive pattern for A. amplus. This study represents the first report of reproductive pattern for this poorly-known Neotropical frugivorous species. The observed monoestrous reproductive pattern supports the existence of synchronization between precipitation and reproduction. This synchronization has been frequently observed in most species of fruit bats. In this study, Artibeus amplus presumably adjust the parturition to anticipate the rainy season, as a strategy that allows maintenance of offspring during high availability of fruits. Rev. Biol. Trop. 65 (1): 335-344. Epub 2017 March 01.

ResumenPoliestría bimodal es el patrón reproductivo más común en murciélagos tropicales, y consite en producir una cría por hembra dos veces al año. Los patrones reproductivos estan estrechamente relacionados con regímenes de precipitación, frecuentemente manifestándose dos veces al año en regiones tropicales. El objetivo de nuestro estudio fue determinar el patrón reproductivo del murciélago frugívoro grande, Artibeus amplus Handley 1987, en una cueva en los Andes venezolanos habitada por una colonia grande y estable. De este modo, en este estudio describimos por primera vez este aspecto biológico fundamental de esta especie de murciélago Neotropical desconocida, a través de la examinación de características reproductivas externas de machos (testículos inguinales o escrotados) y hembras (preñadas, lactantes o postlactantes), basado en 211 individuos (120 machos y 91 hembras) capturados entre septiembre 2008 y agosto 2009, en la Cueva del Parque Las Escaleras, en Táchira, Venezuela. Durante este período de muestreo mensual por un año, la mayoría de los machos mostraron testículos escrotados grandes, con promedio de 10 mm de longitud máxima. La examinación de las hembras indicó que aunque la preñez fue observada por primera vez en noviembre 2008, esta alcanzó su máximo durante enero y febrero 2009. Aunque la presencia de machos adultos con testículos escrotados a lo largo del año podría implicar que las hembras experimentan más de una preñez, nuestros resultados sugieren un patrón reproductivo monoestro estacional para A. amplus. Este estudio representa el primer reporte de patrón reproductivo para esta especie de frugívoro neotropical desconocido. El patrón reproductivo monoestro observado apoya la existencia de una sincronización entre precipitación y reproducción. Esta sincronización ha sido frecuentemente observada en especies de murciélagos frugívoros. En este estudio, Artibeus amplus presumiblemente ajusta el parto anticipando la estación lluviosa, como una estrategia que permite el mantenimiento de las crías durante la disponibilidad máxima de frutas.

Reproductive pattern of the large fruit-eating bat, Artibeus amplus (Chiroptera: Phyllostomidae) in the Venezuelan Andes.

Bimodal polyestry is the most common reproductive pattern in tropical bats, and it consists in producing one offspring per female twice a year. Reproductive patterns are closely related to rainfall regimes, frequently occurring twice a year in tropical regions. The goal of our study was to determine the reproductive pattern of the large fruit-eating bat, Artibeus amplus Handley, 1987 in a cave in the Venezuelan Andes inhabited by a large, stable colony. Thus, in this study we describe for the first time this important biological aspect of this unknown Neotropical bat species through the examination of external reproductive characteristics of males (inguinal or scrotal testes) and females (pregnant, lactating, post-lactating), based on 211 individuals (120 males and 91 females) captured between September 2008 and August 2009, in Cueva del Parque Las Escaleras, Estado Táchira, Venezuela. During this period of monthly sampling for a full year, most males displayed large scrotal testes, averaging 10 mm maximum length. The examination of females indicated that although pregnancy was first observed in November 2008, it reached a maximum during January and February 2009. Although adult males with scrotal testes throughout the year could imply that females have more than one pregnancy, our results suggested a seasonally monoestrous reproductive pattern for A. amplus. This study represents the first report of reproductive pattern for this poorly-known Neotropical frugivorous species. The observed monoestrous reproductive pattern supports the existence of synchronization between precipitation and reproduction. This synchronization has been frequently observed in most species of fruit bats. In this study, Artibeus amplus presumably adjust the parturition to anticipate the rainy season, as a strategy that allows maintenance of offspring during high availability of fruits.

A new enigmatic Late Miocene mylodontoid sloth from northern South America.

A new genus and species of sloth (Eionaletherium tanycnemius gen. et sp. nov.) recently collected from the Late Miocene Urumaco Formation, Venezuela (northern South America) is herein described based on a partial skeleton including associated femora and tibiae. In order to make a preliminary analysis of the phylogenetic affinities of this new sloth we performed a discriminate analysis based on several characters of the femur and tibia of selected Mylodontoidea and Megatherioidea sloths. The consensus tree produced indicates that the new sloth, E. tanycnemius, is a member of the Mylodontoidea. Surprisingly, the new taxon shows some enigmatic features among Neogene mylodontoid sloths, e.g. femur with a robust lesser trochanter that projects medially and the straight distinctly elongated tibia. The discovery of E. tanycnemius increases the diversity of sloths present in the Urumaco sequence to ten taxa. This taxon supports previous studies of the sloth assemblage from the Urumaco sequence as it further indicates that there are several sloth lineages present that are unknown from the better sampled areas of southern South America.

Erratum: A new enigmatic Late Miocene mylodontoid sloth from northern South America.

[This corrects the article DOI: 10.1098/rsos.140256.].