On the presence of Arcellites disciformis Miner emend. Ellis & Tschudy (Salviniales), and other megaspores, from the Cenomanian of Patagonia, Argentina

PATRICIO SANTAMARINA; VIVIANA BARREDA; ARI IGLESIAS; AUGUSTO VARELA

San Salvador de Bahía

Congreso; International Organization of Paleobotany Conference; 2016

Universidad de Bahía

We report here the first South American record of Arcellites disciformis from theCenomanian Cerro Waring section (S49º31?16.8??-W71º29?07.7??), lower member of MataAmarilla Formation, Santa Cruz Province, Argentina.This taxon corresponds to a heterosporous fern related to Salviniales on thebases of morphological features, which posses a fossil age constricted to the Albianand Cenomanian, widely recorded in North America but without previous record forthe Southern Hemisphere. The Lower member of Mata Amarilla Formation representa shallow marginal marine embayment associated to important fresh water fluvialinflux, with a well constricted age to the early-middle Cenomanian, base on twoash beds (older than 96.23 ± 0.71 My). A.disciformis is associated with other megaspores assigned to Balmeisporites sp., and at least one otherundetermined form. Megaspores were analyzed under light and scanning electronicmicroscopes. Arcellites  has some previous Albian records in Patagonia,from the same sedimentary basin but with dissimilar species: A. santacrucensis Baldoni, A. humilisVillar de Seoane & Archangelsky, A.pentagonalis Villar de Seoane & Archangelsky and  Arcellites sp. A. The new Patagonianspecimens of Arcellites disciformis fitwith the range of variations of the original diagnosis. The new Cenomanian record extends the stratigraphicdistribution of Arcellites in the AustralBasin, and enlarges the importance of thesewater ferns probably related to extinct families among Salviniales. New studies in yet unexplored areaswould help to a better understanding of the evolutionary history of importantgroup of water ferns and others aquatic plants in the mid-Late Cretaceousecosystems of Patagonia.