Commentary p306

A taxonomic revision of Middle Devonian chitinozoans identified as Ramochitina boliviensis Grahn, 2002, from the Los Monos Formation in Tacobo TCB X-1001 and Ramos R-1011 boreholes Tarija Basin (South Bolivia northwestern Argentina), has been conducted. Given morphological similarities between R. ramosi (Sommer & van Boekel, 1964), an extensive literature review detailed morphometric analysis were undertaken. The results indicate that both species range late Emsian to middle Givetian are...

Veryhachium Deunff 1954, originally described from the Ordovician of western France, in one most frequently recorded acritarch genera. Over 250 species and subspecies, Cambrian to Neogene, have been attributed genus. This genus has a simple morphology; it displays triangular, rectangular, or polygonal central vesicle, with few, processes drawn out angles vesicle single plane, ad sometimes supplementary auxillary arising body. emended reised numerous times. The number valid is excessive: are...

Chitinozoans recovered from one section of the Middle Devonian Los Monos Formation in TCB X-1001-Tacobo borehole, sub-Andean basin Bolivia, have been analysed. Eleven eighteen processed cutting samples yielded specimens that allowed taxonomic study. genera and thirty-five chitinozoan species were identified with four them recorded for first time Western Gondwana. Ancyrochitina biconstricta , parisi Angochitina galarzae Ramochitina boliviensis are among most relevant taxa restricted to...

Palynomorph assemblages have been recovered from deposits believed to straddle the Ordovician/Silurian boundary, upper member of Salar del Rincón Formation, in Puna region north‐west Argentina. The palynomorph are dominated by terrestrial cryptospores, but also contain marine elements (acritarchs, prasinophycean algae and chitinozoans). cryptospore similar composition those described coeval worldwide, suggesting that producers were cosmopolitan tolerated a wide range climatic conditions....

First Appearance Datums (FADs) of selected, easily recognizable acritarch morphotypes are assessed to determine their potential contribution correlation between Lower and Middle Ordovician stages substage divisions along the Gondwanan margin (Perigondwana) Perigondwana other palaeocontinents. The FADs for 19 genera, species groups recorded throughout biogeographical ranges. taxa investigated fall into three groups. Some have at about same level ranges useful long-distance intercontinental...

The origin of land plants is one the most important evolutionary events in Earth’s history. mode and timing terrestrialization remains debated previous data indicate Gondwana to be center land-plant radiation at ~ 470–460 Ma. Here we present oldest occurrences trilete spores, probably earliest traces vascular yet recorded. spores occur Ordovician, Sandbian (455 million years old) successions central Sweden, once part paleocontinent Baltica. These strata are independently dated by marine...

Abstract Veryhachium Deunff 1954, originally described from the Ordovician of western France, is one most frequently recorded acritarch genera. Over 250 species and subspecies, Cambrian to Neogene, have been attributed genus. This genus has a simple morphology; it displays triangular, rectangular, or polygonal central vesicle, with few, processes drawn out angles vesicle in single plane, sometimes supplementary auxiliary arising body. emended revised numerous times. The number valid...

The palynological assemblages of the upper part Los Espejos Formation and lower Talacasto Formation, in northern outcrops San Juan Precordillera, Argentina, were studied.This section spans Silurian/Devonian boundary.Therefore analysis helps to constrain age identify position system boundary.This interval has been much discussed owing scarcity stratigraphically valuable fossils.The miospores marine phytoplankton present point a Late Ludlow/ Přídolí? early Lochkovian age.The occurrence...

Abstract Early Paleozoic rocks are widespread, superbly exposed, and reach several thousand metres thick in southern South America. A largely quadripartite geotectonic subdivision of this huge area encompasses: (1) intracratonic basins forming the sedimentary cover Amazonian craton (Brazilian collage); (2) a clastic platform surrounding Pampia Terrane (Sierras Subandinas Cordillera Oriental); (3) subduction-related parautochthonous volcanic arcs associated volcano-sedimentary (Puna–Famatina...

The palynological assemblages of the Talacasto and Punta Negra formations, from Argentinean Precordillera, were analysed. Marine phytoplankton is dominant in both stratigraphic units. ?Cymatiosphaera florida, Evittia sommeri, Palacanthus ledanoisii, Riculasphaera fissa, Schizocystia pilosa, Tysanoprobolus polykion Winwaloeusia distracta are among most age-significant species Formation, while Amicosporites sp. cf. A. streelii, Dictyotriletes emsiensis Morphon, favosus ?Knoxisporites riondae...

The Middle Member of the Zorritas Formation in Antofagasta region northern Chile, yielded terrestrial and marine palynomorph assemblages which span Devonian/Carboniferous boundary. show a clear predominance palynomorphs with 70 miospore species, 18 phytoplankton two non-marine algae one chitinozoan all coming from 15 productive levels. Palynomorphs are poorly preserved most them reworked. Three palynological associations recognized based on miospores. These assigned to Tournaisian–Visean,...

SILURIAN MARINE ORGANIC-WALLED PHYTOPLAKTON AND MIOSPORES OF THE LOS ESPEJOS FORMATION, IN RIO DE LAS CHACRITAS SECTION, SAN JUAN PRECORDILLERA, ARGENTINA. Marine organic-walled phytoplankton (acritarchs and chlorophytes) miospores were recorded from nine productive levels of the lower to middle section Los Espejos Formation, in Río de Las Chacritas stratigraphic column, Central San Juan Precordillera. The marine is highly diversified dominates palynological assemblage through section, with...