Record of Brachyoxylon patagonicum, a Cheirolepidiaceae wood preserved by gelification in the Aptian Maceió Formation, Sergipe–Alagoas Basin, NE Brazil

Abstract

A gelified wood from the late Aptian Maceió Formation (Sergipe–Alagoas Basin, northeastern Brazil) was studied under scanning electron microscopy and organic petrography allowing for the record of the fossil-species Brachyoxylon patagonicum, likely belonging to the Cheirolepidiaceae family. The anatomical structure of the secondary xylem is characterized by mixed type of radial tracheary pitting, composed exclusively by uniseriate bordered pits, in separated, contiguous and compressed arrangements. Cross-field pits are of the araucarioid type, xylem rays are uniseriate or rarely partially biseriate, and probable sporadic traumatic resin canals are present. The present record expands the paleobiogeographic distribution of the fossil-genus in South America and amplifies its climatic tolerance, since the parent plants lived in the Aptian Tropical Equatorial Hot arid belt. The presence of fungal remains within the wood tissue, and the absence of signs of plant defense against fungal decay suggest saprophytic fungus–wood interactions that likely occurred during a stage of aerobic exposure before burial.