Shell variability in Tawera gayi (Veneridae) from southern South America: a morphometric approach based on contour analysis

2010 ◽  
Vol 91 (4) ◽  
pp. 815-822 ◽  
Author(s):  
Sandra Gordillo ◽  
Federico Márquez ◽  
Javiera Cárdenas ◽  
Miguel Ángel Zubimendi
Keyword(s):  
South America ◽  
Late Quaternary ◽  
Common Species ◽  
Tierra Del Fuego ◽  
Elliptic Fourier Analysis ◽  
Contour Analysis ◽  
Southern South America ◽  
Morphological Variations ◽  
Marine Deposits ◽  
History Of

This study analyses the significance of shell morphological variations in the venerid clam Tawera gayi, a typical element of shallow marine soft bottoms in southern South America and the most common species recovered from Late Quaternary marine deposits along the Beagle Channel, Tierra del Fuego. Fossil and modern Tawera shells from different localities around the southern tip of South America were analysed using the Elliptic Fourier Analysis (EFA) method. Taking into account the palaeontological history of this genus in the southern hemisphere, EFA was also performed on shells of Tawera congeners from South Africa (T. philomela) and New Zealand (T. spissa). The use of EFA permitted the distinction between the three Tawera species and geographical differentiation in the T. gayi groups. These morphological variations of T. gayi appear best related to ecophenotypic plasticity as a response to different environmental conditions, although the palaeobiogeographical history of Tawera in South America cannot be ruled out.

Late Quaternary glaciation history of isla de los Estados, southeasternmost South America

2010 ◽  
Vol 73 (3) ◽  
pp. 521-534 ◽  
Author(s):  
Per Möller ◽  
Christian Hjort ◽  
Svante Björck ◽  
Jorge Rabassa ◽  
Juan Federico Ponce
Keyword(s):  
South America ◽  
Lake Sediments ◽  
Late Quaternary ◽  
Glacial Maximum ◽  
Tierra Del Fuego ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Glacial Erosion ◽  
Quaternary Glaciation ◽  
History Of

Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400–450 m a.s.l., and above that trimline a distinct sharp-edged nunatak derived landscape is present. The westernmost part of the island has a lower, more subdued topography, reflecting its "softer" geology but possibly also over-running and erosion by mainland-derived ice streams. The present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs. A combination of OSL and 14C datings show that these sediments mostly date from the latest (Wisconsinan/Weichselian) glacial cycle, i.e. from the last ca. 100 ka with the oldest (glaciolacustrine) deposits possibly as old as 90–80 ka. The upper parts of overlying tills, with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island, date from the last global glacial maximum (LGM). Radiocarbon ages of peat and lake sediments indicate that deglaciation began 17–16 cal ka BP.

A new fossil cricetid (Rodentia, Sigmodontinae) from northeastern Brazil with remarks on small mammal extinctions in the tropical Quaternary

2020 ◽  
Vol 101 (4) ◽  
pp. 1133-1147
Author(s):  
Simone B das Neves ◽  
Ulyses F J Pardiñas ◽  
Patrícia Hadler ◽  
Elver L Mayer ◽  
Ana M Ribeiro
Keyword(s):  
New Species ◽  
South America ◽  
Small Mammal ◽  
Late Quaternary ◽  
Northeastern Brazil ◽  
The South ◽  
Quaternary Deposits ◽  
Extant Species ◽  
Genetic Features ◽  
History Of

Abstract The rare cricetid rodent Bibimys Massoia, 1980 contains three extant species that are distributed in the lowlands of eastern South America between 35°S and 20°S and distinguished mostly by subtle morphological and genetic features. Several fragmented jaws belonging to this genus were recovered from Late Quaternary deposits located in northeastern Brazil, forming part of a rich archaeological and paleontological small mammal assemblage that has been recovered from caves in the Serra da Capivara, state of Piauí. This material is described herein as belonging to a new species, the most hypsodont member of the genus. The specimens also represent an extralimital occurrence of this sigmodontine, as the nearest extant population of Bibimys is ~1,200 km to the south. Because there are few reliable records of extinct small mammals from the Pleistocene–Holocene transition on the South American continent, in describing this new sigmodontine we extend the records of past biodiversity preserved in the Quaternary deposits of tropical South America. This new species likewise highlights that the Serra da Capivara deposits are promising for understanding the evolutionary history of cricetid rodents.

scholarly journals A history of Proterozoic terranes in southern South America: From Rodinia to Gondwana

2012 ◽  
Vol 3 (2) ◽  
pp. 137-145 ◽  
Author(s):  
C. Casquet ◽  
C.W. Rapela ◽  
R.J. Pankhurst ◽  
E.G. Baldo ◽  
C. Galindo ◽  
...  
Keyword(s):  
South America ◽  
Southern South America ◽  
History Of

scholarly journals Microsatellite typing of ancient maize: insights into the history of agriculture in southern South America

2006 ◽  
Vol 274 (1609) ◽  
pp. 545-554 ◽  
Author(s):  
Verónica V Lia ◽  
Viviana A Confalonieri ◽  
Norma Ratto ◽  
Julián A. Cámara Hernández ◽  
Ana M. Miante Alzogaray ◽  
...  
Keyword(s):  
South America ◽  
Ancient Dna ◽  
Microsatellite Loci ◽  
Southern South America ◽  
Maize Cultivation ◽  
High Incidence ◽  
Close Relationship ◽  
History Of ◽  
Frequent Allele ◽  
Positive Results

Archaeological maize specimens from Andean sites of southern South America, dating from 400 to 1400 years before present, were tested for the presence of ancient DNA and three microsatellite loci were typed in the specimens that gave positive results. Genotypes were also obtained for 146 individuals corresponding to modern landraces currently cultivated in the same areas and for 21 plants from Argentinian lowland races. Sequence analysis of cloned ancient DNA products revealed a high incidence of substitutions appearing in only one clone, with transitions prevalent. In the archaeological specimens, there was no evidence of polymorphism at any one of the three microsatellite loci: each exhibited a single allelic variant, identical to the most frequent allele found in contemporary populations belonging to races Amarillo Chico, Amarillo Grande, Blanco and Altiplano. Affiliation between ancient specimens and a set of races from the Andean complex was further supported by assignment tests. The striking genetic uniformity displayed by the ancient specimens and their close relationship with the Andean complex suggest that the latter gene pool has predominated in the western regions of southern South America for at least the past 1400 years. The results support hypotheses suggesting that maize cultivation initially spread into South America via a highland route, rather than through the lowlands.

The evolutionary history of Senna ser. Aphyllae (Leguminosae–Caesalpinioideae), an endemic clade of southern South America

2017 ◽  
Vol 303 (10) ◽  
pp. 1351-1366
Author(s):  
Federico O. Robbiati ◽  
Ana Anton ◽  
Brigitte Marazzi ◽  
Marilyn Vásquez-Cruz ◽  
Renée H. Fortunato
Keyword(s):  
South America ◽  
Evolutionary History ◽  
Southern South America ◽  
History Of
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