Primeiro registro de Pecopteris Taguaiensis no Monumento Natural das Árvores Fossilizadas do Estado do Tocantins

Abstract

In this study, the analysis of a fossil leaf, of Permian period, specimen preserved threedimensionally through silica permineralization is presented. The specimen originates from the Monumento Natural das Árvores Fossilizadas do Estado do Tocantins (Monaf), located in the Parnaíba sedimentary basin. The monument is a fully protected conservation unit that houses the most significant fragment of the Petrified Forest of Northern Tocantins. The area features outcrops of tree fern stems and epiphytes, sphenophytes, gymnosperms, and fertile and sterile fern leaf organs. Its rich fossil assemblage is notable for the size, quantity, and state of preservation of the specimens. The studied specimen, collected from the surface, was registered and deposited in the Paleobiology Laboratory of the Federal University of Tocantins, Porto Nacional Campus, where it was photographed, sketched, and subjected to morpho-anatomical measurements using a stereomicroscope, electron microscope, digital caliper, and compass. The analyses were performed through comparison with data available in paleobotanical literature. The fossilized structures, composed of a fragment of the frond rachis in organic connection to pinnae and pinnules, were related to sterile leaves of Pecopteris taguaiensis. This identification is based on the robust rachis, pinnae inserted into the frond rachis at a 54° angle, sterile pinnules that are oblong and contiguous, free from each other but fully attached to the rachis at the base, smooth entire margins, robust midveins emerging at approximately 90° from the rachis, and lateral veins bifurcating near the apex and leaf edges. The fossil specimen was identified as Pecopteris taguaiensis, marking the occurrence of this species at the collection site, the fossiliferous site known as Fazenda Buritirana, Mutuca Formation, within Monaf. located in the municipality of Filadélfia, State of Tocantins.