Unique conifer assemblage from Late Jurassic-Early Cretaceous deposits (NE Brazil) unveils the paleoclimate and paleobiogeography in the interior of equatorial Gondwana

Abstract

The Brazilian paleoxyloflora conspicuously lacks a robust Late Jurassic-Early Cretaceous record. However, several fossil woods have been reported since the 18th century from the Upper Jurassic to Lower Cretaceous deposits of Missão Velha Formation, Araripe Basin, northeastern Brazil, although no taxonomic and systematic analysis has been carried out so far. Here, we provide the first taxonomic and systematic study of these fossil woods, utilizing them for paleoclimatic and paleobiogeographic inferences for this region in equatorial Gondwana. We thus describe a new fossil-species, Metapodocarpoxylon brasiliense, and document, for the first time, the presence of Agathoxylon mendezii in Brazil. They are distinguished by characters of radial pit arrangement, cross-field pits, presence of resin plugs, axial parenchyma, septate tracheids, and ray seriation and height. These fossil-genera have been previously observed in other Mesozoic paleoxylofloras of Gondwana, being Metapodocarpoxylon, in particular, restricted to the tropical belt and coastal areas, and its occurrence in Brazilian paleofloras is unknown to date. Its new occurrence suggests a migration of this element of the paleovegetation towards inland areas likely triggered by paleoclimatic changes from the Late Jurassic onwards. The presence of indistinct and distinct growth rings with narrow latewood in the conifer assemblage suggests a moderately seasonal paleoclimate with rainy and dry seasons, which is also supported by the geological data, probably stimulated by the monsoonal regime in the basinal area. The new wood records, combined with geological and paleoclimatological background information and palynological data obtained from the study area in the early 2000’s allowed for a preliminary reconstruction of a segment of the landscape during deposition of the Missão Velha Formation.