WOODS WITH AFFINITIES TO THE EUROAMERICAN CORDAITALES IN PEDRA DE FOGO FORMATION, PERMIAN OF THE PARNAÍBA BASIN, BRAZIL

CONCEIÇÃO, DOMINGAS MARIA DA; CRISAFULLI, ALEXANDRA; IANUZZI, ROBERTO; NEREGATO, RODRIGO

Cuiaba

Simposio; XV SIMPÓSIO BRASILEIRO DE PALEOBOTANICA E PALINOLOGIA; 2019

ALPP, SOCIEDAD BRASILEIRA DE PALEONTOLOGIA

Even though permian fossils plants from the Parnaíba Basin have been known since the nineteenth century, they have received little attention in the last decades, principally the flora from Pedra de Fogo Formation (PFF). Actually, there is still a significant gap in our knowledge, especially regarding the gymnosperms petrified woods when compared with other parts of the Southern Hemisphere (e.g., Paraná Basin). Cordaitales are an extinct group of gymnosperms with records from the Carboniferous to the Permian. The most complete records of this group come from the floristic province Euramerican. On the other hand, in floristic province Gondwana there are few woods associated with these plants. Generally, stems belong to these plants display regular septations like artisia pith, and commonly are placed either in Mesoxylon Scott and Maslen 1910 or Cordaixylon Grand´Eury 1877 and both are record in province Euramerican. In the last few years, several prospections have been carried out in the PFF focusing on mapping fossil-bearing localities in the eastern and southeastern portions of the basin, which evidenced important outcrops with plant assemblages mostly composed of gymnosperm petrified woods, some of them still in life position. Thus, here we present the first results of taxonomic analysis of these woods, recovered from these new outcrops. The woods were cut in three distinct planes: cross-section, tangential longitudinal and radial longitudinal; following the standard procedures for woody taxonomy studies. These sections were prepared at the Laboratório de Laminação, Universidade do Vale do Rio dos Sinos (UNISINOS), São Leopoldo, Brazil. The new woods described herein have large septate pith surrounded by approximately c.29 primary xylem bundles endarch organized in a vascular architecture sympodial. Radial bordered pits of tracheids are mostly bi- or triseriate, cupressoid cross-field pits and xylem rays are uniseriate and rarely biseriate. Considering the genera of the Gondwana classified as Cordaitales show anatomical distinct characteristics, comparing to the specimens in question, and Mesoxylon has mesarch cauline bundles, and for this reason these specimens are inserted in Cordaixylon. The permian plants of the basin represent a subtropical flora that was located between the two major paleozoic floristic provinces i.e., Gondwana in the south and Euroamerican in the north, in a particular paleofitogeographic position, which has generated some questions about the possible composition of its floristic elements and what they would represent in terms of similarities with gondwanic and nordic (tropical) floras. Thus, the results are important for a better understanding of this discussion and encourage the researchers to reflect about this issue deeper, and it can provide relevant data in terms of paleoecology and the life paleoenvironments of this flora.