The triassic Taphoflora from Parana basin, southern Brazil: an overview

Abstract

A Triassic identified in the central region of the State of Rio Grande do Sul, Southern Brazil, represents an important biostratigraphic stage in the palaeofloristic succession of Parana basin. The megafloristic association composed of compressed leaves, fronds and seeds shows a predominance of the genus Dicroidium, with several species, and other important taxa like Neocalamites sp, Cladophlebis sp., Tetraptilon aff. heteromerum, Ginkgoites antarctica, Sphenobaiera sp, Podozamites sp, Nilssonia sp, Pteruchus sp and Carpolithus sp. Taking into account the stratigraphic distribution of different species of the genus Dicroidium, a biostratigraphic framework was previously established and an informal floristic interval, named Dicroidium odontopteroides Flora was proposed (Late Anisian to Late Ladinian, Middle Triassic). The general composition of the in Rio Grande do Sul is similar to the Dicroidietum odontopteroidium characterized for Australasia corresponding to a forest association composed by trees, woody shrubs, ground cover and swamps growths. The presence of xilopteroid leaves indicates levels of water stressed substrate. The homogeneous composition of the assemblage, and the small size of leaves of the whole association in relation to the of other Gondwana regions (e. g. Molteno Formation) seems to indicate particular drainage patterns prevailing during deposition of Santa Maria Formation.