Terminalia palaeopubescens nov. sp. (Combretaceae), from the fonseca formation (Eocene/oligocene), minas gerais state, Brazil: Leaf architecture, epyphyllous fungi and paleoclimate [Terminalia palaeopubescens sp. nov. (Combretaceae) da forma??o fonseca (Eoceno/oligoceno) de minas gerais, Brasil: Morfología foliar, fungos epifilicos associados e paleoclima]

摘要

In this study, well-preserved leaf-blade compressions and impressions from shale levels in the Fonseca Formation (Priabonian/Rupelian of the Fonseca Basin, state of Minas Gerais, southeastern Brazil) and associated epiphyllous fungi are described. Based on leaf architecture and indumentum, a new species is established, assigned to the extant tropical genus Terminalia L. (Combretaceae). The leaf of Terminalia palaeopubescens sp. nov. is mesophyll, narrow obovate and with an entire margin. Its secondary veins are camptodromous- brochidodromous, the tertiary pattern is percurrent mixed predominantly alternate, the quaternaries are alternate percurrent and the higher orders regular polygonal reticulate, with small and well developed areoles. Trichomes are present in the indumentum and are simple, slender, pointed, and with a swollen base, typical of the Combretaceae. Epyphyllous fungi, in the shape of microthyrioid disks of variable size and profusely colonizing the leaf surface, were assigned to Callimothallus Dilcher (Microthyriaceae). The presence of those biogenic structures (besides Phragmothyrites Edwards, already reponed in the same levels of the Fonseca Formation) indicates that a prominent leaf mycoflora was associated to the vegetation, probably sustained by warm and humid conditions. The data here presented, analyzed together with other taxonomic, taphonomic and foliar physiognomic indicators, lead to the hypothesis that a dense rainforest, supported by heavy rainfall and high temperatures, was thriving near the banks and floodplain environments associated to fluvial systems of the Fonseca Formation, during the Eocene/Oligocene transition, in southeastern Brazil.