Taxonomical Consideration, Phylogeny and Paleobiogeography of Some Argentinian Ypresian Benthic Foraminiferal Species

Abstract

Rich and well preserved Argentinian taxa made it possible to correlate them with those previously identified species in the coeval sequence in different Tethyan North America, Europe and Middle East localities. This study deals with new information on paleontology and lineages of fourteen Argentinian Ypresian benthic foraminiferal species from the Punta Torcida Formation, lower-middle Eocene (Ypresian-lower Lutetian), Tierra del Fuego Island and Fuegian continental shelf, which belongs to twelve genera: Laevidentalina, Lagenoglandulina, Tollmannia, Tristix, Leticuzonaria, Palmula, Leroyia, Marginulina, Ramulina, Orthokarstenia, Rectuvigerina and Pleurostomella. Ten of the illustrated species are believed to be new: Laevidentalina jannoui, Lagenoglandulina argentinica, Tollmannia argentinica, Leticuzonaria argentinica, Palmula americana, Leroyia argentinica, Marginulina argentinica, Ramulina subornata, Ramulina morsii and Rectuvigerina argentinica sp. nov. The paleoenvironment of the Argentinian taxa would have been a shelf sea of normal salinity, where muds were deposited under low energy and low oxygen conditions, as is suggested by the dominance of infaunal morphotypes and excellent preservation of the tests, whereas intercalated sandstones reflect moderate energy and oxic conditions, bearing microfossil assemblages displaced from shallower settings.