Brachyphyllum: State of the art and new data regarding B. obesum, the most representative fossil plant in the Araripe Basin, Brazil

Abstract

Among the rich paleobotanical record of the Araripe Basin, the coniferous fossil taxon Brachyphyllum stands out, found in the Crato, Romualdo, and possibly Ipubi formations. In these units, species Brachyphyllum obesum, Brachyphyllum castilhoi, and Brachyphyllum sattlerae are found, the first being the most common. However, there are still many gaps, especially regarding the paleoecology and parataxonomy of this fossil genus. This study aims to make a broad review of the current stage of knowledge of Brachyphyllum from the Araripe Basin, a very representative taxon of the local palaeoflora. We consider data available in the literature and morpho-anatomical analyses of new specimen using Scanning Electron Microscopy. The specimen analyzed in SEM has tracheids and features typical of Araucariaceae, like biseriate and alternating intervascular pits. However, there is variation in the number of pits per cross-field compared to other specimens. This variation may indicate greater diversity of fossil Brachyphyllum in the Araripe Basin. All species of Brachyphyllum from the Araripe Basin have xeromorphic characteristics, which can be adaptive responses to the conditions of aridity and/or salinity in the Crato and Romualdo formations.