Permineralized fern petioles and roots from the Upper Cretaceous, James Ross Island, Antarctica

LAURA PIPO, M.; ARI IGLESIAS; BODNAR JOSEFINA

La Plata

Congreso; reunión Anual de Comunicaciónes de la Asociación Paleontológica Argentina; 2019

Asociación Paleontológica Argentina

The Antarctic fossil record of ferns extends since the Permian to the Oligocene, and consists mostly of leaf compressions.Permineralized organs are less known, only some reports from the Permian, Triassic and Jurassic of rizhomes, petioles,fronds and sporangia from the Transantarctic Mountains and Early Cretaceous cyathealean and osmundalean stems. Although,permineralizedfernswerenotfoundinUpperCretaceousrocks,previousstudiesofsporesandcompressionssuggestedthepresenceofthefamiliesPteridaceae,Matoniaceae,Schizaeaceae,MarattiaceaeandGleicheniaceae.In this work, we describe the first record of permineralized petioles and roots in marine calcareous concretions from early Campanian sediments from the Santa Marta Formation (James Ross basin).The roots present diarch steles, a continuous pericicle and cortical parenchyma. The petioles have one C-shaped amphyphloic vascular bundle, with different degrees of constriction in the bundle, endodermis, pericicle and cortical parenchyma. C-shaped vascular bundles characterize several groups including the basal Polypodiopsida, and the constrictions in the bundle resemble those  from extant Gleicheniaceae. The pres ence of framboidal pyrite and the micritic/sphalerite cementation enabled very good preservation of the plant organs whichindicate fast and early diagenetic processes. This preservation holds important anatomical information about plant organs that were not known for the Southern Hemisphere, and let us do more complete reconstructions of plants that lived in the Antarctic Continent during the Upper Cretaceous.