New Neogene taxa of the tribe Chlamydini Teppner, 1922 (Pectinidae, Bivalvia) of southern South America

2019 ◽  
Vol 93 (06) ◽  
pp. 1088-1104
Author(s):  
María B. Santelli ◽  
Claudia J. del Río
Keyword(s):  
South America ◽  
Antarctic Circumpolar Current ◽  
Middle Miocene ◽  
South American ◽  
Southern South America ◽  
Southeastern Pacific ◽  
Previous Proposal ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Middle Pliocene

AbstractThe Chilean species traditionally assigned to the genera Chlamys Röding, 1798 or Zygochlamys Ihering, 1907 are now placed in two new endemic South American taxa: Dietotenhosen n. gen. (middle Miocene–early middle Pliocene), to include the southeastern Pacific Ocean species D. hupeanus (Philippi, 1887) n. comb. and D. remondi (Philippi, 1887) n. comb., and Ckaraosippur n. gen. (earliest middle Miocene–Pliocene), for C. calderensis (Möricke, 1896) n. comb. (Chile) and C. camachoi n. sp. (Argentina). Both genera are the youngest survivors of the tribe Chlamydini in southern South America. None of them is related to the circumpolar genus Psychrochlamys Jonkers, 2003, and the previous proposal of the dispersal through the Antarctic Circumpolar Current for the species included herein in Dietotenhosen is rejected.UUID: http://zoobank.org/61b4bb50-321f-4b78-9069-609178ef0817

The santonian through paleogene record of Proteaceae in the southern South America - Antarctic peninsula region

1998 ◽  
Vol 11 (4) ◽  
pp. 373 ◽  
Author(s):  
Rosemary A. Askin ◽  
Alicia M. Baldoni
Keyword(s):  
South America ◽  
Antarctic Peninsula ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Type Species ◽  
Pollen Record ◽  
South American ◽  
Southern South America ◽  
Nothofagus Forest ◽  
The Antarctic

Proteaceous plants were an important component of the high-latitude Late Cretaceous–Paleogene podocarpaceous conifer and Nothofagus forest vegetation growing in high-rainfall temperate conditions. In the southern South America–Antarctic Peninsula region the fossil record of the Proteaceae comprises pollen, leaves, fruits and wood with affinities to the extant subfamilies Grevilleoideae, Proteoideae, and possibly Carnarvonioideae and Persoonioideae. The oldest reported occurrences of Proteaceae in this region are in the middle–late Santonian of the Antarctic Peninsula and include pollen of Proteacidites subscabratus Couper, with the addition in the Campanian of other species of Proteacidites and Propylipollis, Cranwellipollis spp. and Peninsulapollis spp. Diversity of proteaceous pollen increased through the Campanian and Maastrichtian, reflecting the spread of Proteaceae along the Antarctic Peninsula and into South America. Both endemic species and species derived from the Australian region are represented. Compared to coeval Australian assemblages, however, proteaceous diversity remained relatively low. Interestingly, Beauprea-type species (Beaupreaidites spp., Peninsulapollis spp.) are common and varied in the Antarctic Peninsula from Campanian into the Eocene, yet the South American pollen record does not include these forms, except for rare Peninsulapollis gillii. Possibly drier conditions may have discouraged northward migration of this group. South American fossil proteaceous taxa are primarily related to Grevilleoideae, a trend that continues into the modern flora on that continent.

Neogene Pectinidae (Bivalvia) of tribe Chlamydini Teppner, 1922 in Patagonia (Argentina):ZygochlamysIhering, 1907 and three new genera

2018 ◽  
Vol 93 (2) ◽  
pp. 312-336 ◽  
Author(s):  
María B. Santelli ◽  
Claudia J. del Río
Keyword(s):  
Late Miocene ◽  
Type Species ◽  
Antarctic Circumpolar Current ◽  
Middle Miocene ◽  
New Genus ◽  
Early Miocene ◽  
New Genera ◽  
Early Pliocene ◽  
Circumpolar Current ◽  
The Antarctic

AbstractZygochlamysIhering, 1907 is revised and three new genera of tribe Chlamydini are named: the monospecific early Miocene generaPixiechlamysnew genus (type species:Pecten quemadensisIhering, 1897) andChokekenian. gen. (type species:Zygochlamys nicolasiMorra, 1985), and the late Miocene–early PlioceneMoirechlamysn. gen., containingPecten actinodesSowerby, 1846 (type species) andChlamys auroraeFeruglio, 1954.Zygochlamysis restricted to includeZ. geminata(Sowerby, 1846) (type species),Z. jorgensisIhering, 1907, andZ. sebastianiMorra, 1985. The present analysis increases the biostratigraphic usefulness of the group and improves taxonomic knowledge of the Neogene molluscan assemblages defined previously for Patagonia.Zygochlamys geminatais confined to the latest Oligocene–early Miocene interval of the Austral Basin of Patagonia (Argentina) and to the early Miocene of Chile,Z. jorgensisis restricted to the early to middle Miocene of the Golfo San Jorge and northern Austral Basins, andMoirechlamysn. gen., the most widespread genus, occurs in the late Miocene–early Pliocene of the Austral, Golfo San Jorge, Valdés, and Colorado basins. All these genera are endemic to southern South America;Zygochlamysis not related to other circumpolar genera such asAustrochlamysJonkers, 2003 orPsychrochlamysJonkers, 2003, rejecting its dispersal in the Antarctic Circumpolar Current, as has been proposed previously.UUID:http://zoobank.org/55d7ea85-5ec5-477a-9ede-5d3d795b75b5

scholarly journals Links between CO<sub>2</sub>, glaciation and water flow: reconciling the Cenozoic history of the Antarctic Circumpolar Current

2014 ◽  
Vol 10 (6) ◽  
pp. 1957-1966 ◽  
Author(s):  
J.-B. Ladant ◽  
Y. Donnadieu ◽  
C. Dumas
Keyword(s):  
Antarctic Circumpolar Current ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Late Eocene ◽  
Early Oligocene ◽  
History Of ◽  
Potential Impact ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Exact Timing

Abstract. The timing of the onset of the Antarctic Circumpolar Current (ACC) is a crucial event of the Cenozoic because of its cooling and isolating effect over Antarctica. It is intimately related to the glaciations occurring throughout the Cenozoic from the Eocene–Oligocene (EO) transition (&amp;approx; 34 Ma) to the middle Miocene glaciations (&amp;approx; 13.9 Ma). However, the exact timing of the onset remains debated, with evidence for a late Eocene setup contradicting other data pointing to an occurrence closer to the Oligocene–Miocene (OM) boundary. In this study, we show the potential impact of the Antarctic ice sheet on the initiation of a strong proto-ACC at the EO boundary. Our results reveal that the regional cooling effect of the ice sheet increases sea ice formation, which disrupts the meridional density gradient in the Southern Ocean and leads to the onset of a circumpolar current and its progressive strengthening. We also suggest that subsequent variations in atmospheric CO2, ice sheet volumes and tectonic reorganizations may have affected the ACC intensity after the Eocene–Oligocene transition. This allows us to build a hypothesis for the Cenozoic evolution of the Antarctic Circumpolar Current that may provide an explanation for the second initiation of the ACC at the Oligocene–Miocene boundary while reconciling evidence supporting both early Oligocene and early Miocene onset of the ACC.

scholarly journals Otolith chemistry indicates population structuring by the Antarctic Circumpolar Current

2008 ◽  
Vol 65 (2) ◽  
pp. 135-146 ◽  
Author(s):  
Julian R Ashford ◽  
Cynthia M Jones ◽  
Eileen E Hofmann ◽  
Inigo Everson ◽  
Carlos A Moreno ◽  
...  
Keyword(s):  
Population Structure ◽  
South America ◽  
Early Life ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Advective Transport ◽  
Complex Population ◽  
Population Structuring ◽  
Circumpolar Current ◽  
The Antarctic

Large-scale transport of seawater in ocean currents may generate spatially complex population structure through the advection of life stages of marine fish species. To test this, we compared the chemistry of otolith nuclei from Patagonian toothfish (Dissostichus eleginoides), presently managed as spatially discrete populations corresponding to fishing management areas along the Antarctic Circumpolar Current (ACC), which transports water eastward around the Southern Ocean. The chemistry of otolith nuclei, laid down during early life, differed significantly between fishing areas off South America and the Antarctic and between some Antarctic areas. However, we found significant discrepancies from expectation for a population structure corresponding to fishing areas. We also found evidence of four groups of fish with different early life chemistry: one associated with South America and three Antarctic groups showing mixing consistent with advective transport along the ACC. These results suggest that toothfish populations are structured by their physical environment; population abundance and persistence may rely on a restricted number of breeding members with access to spawning grounds, whereas fisheries may rely substantially on nonbreeding vagrants transported from fishing areas upstream.

A linear model of the Antarctic circumpolar current

1968 ◽  
Vol 32 (3) ◽  
pp. 465-488 ◽  
Author(s):  
A. E. Gill
Keyword(s):  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Friction Model ◽  
South American ◽  
Average Width ◽  
Friction Parameter ◽  
Circumpolar Current ◽  
Zonal Models ◽  
The Antarctic ◽  
Numerical And Analytical Methods

A simple frictional wind-driven model of the Antarctic circumpolar current is examined. The geometry includes what are thought to be the main features effecting the current, namely a gap corresponding to Drake Passage and a partial barrier corresponding to the South American peninsula. Solutions obtained by both numerical and analytical methods are presented. The analytic solution, valid for small values of a friction parameter, enables the total rate of transport of water by the current to be calculated as a function of the friction parameter and the wind stress distribution. The width which controls the rate of transport by the current tends to be the narrowest encountered rather than the average width as assumed in earlier zonal models. However, the current spreads out to several times this width due to frictional effects. The values of the eddy viscosity required to give a rate of transport of the observed order are about 103cm2/s for a bottom-friction model and of the order of 108cm2/s for a lateral friction model.

scholarly journals Nonlinear Differential Equations Modeling the Antarctic Circumpolar Current

2021 ◽  
Vol 23 (4) ◽  
Author(s):  
Jifeng Chu ◽  
Kateryna Marynets
Keyword(s):  
Fixed Point ◽  
Differential Equations ◽  
Boundary Conditions ◽  
Topological Degree ◽  
Antarctic Circumpolar Current ◽  
Fixed Point Theorems ◽  
Nonlinear Differential Equations ◽  
Existence Results ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe aim of this paper is to study one class of nonlinear differential equations, which model the Antarctic circumpolar current. We prove the existence results for such equations related to the geophysical relevant boundary conditions. First, based on the weighted eigenvalues and the theory of topological degree, we study the semilinear case. Secondly, the existence results for the sublinear and superlinear cases are proved by fixed point theorems.

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