Permian woods with preserved primary structures from the southeast of Brazil (Irati Formation, Paraná basin)

Abstract

This research described fossil woods with preserved pith and primary xylem from strata of the Irati Formation (Artinskian) of the Paraná Basin (southeastern Brazil). The three specimens studied are all related to the Coniferales and include the following taxa: Solenopitys paulistana Kräusel, Atlanticoxylon ibiratinum n. sp. and Abietopitys sp. Kräusel. Solenopitys paulistana represents a species with a solid, heterocellular pith with a peripheral secretory canal system. Atlanticoxylon ibiratinum n. sp. has a lacunose, heterocelular pith with “nests” of sclereids, with a central secretory canal and a peripheral system of canals. Abietopitys sp. has a solid, lobed, homocelular pith associated with a secondary xylem containing cross-fields with non-contiguous pits (abietoid vascular rays). Xeromorphic features observed in these specimens, such as a pith with groups of sclereids and false growth rings, may be related to the depositional environment of the Irati Formation. The specific factor triggering the xeromorphy has not yet been determined, but the present study corroborates clearly the sedimentary evidence of dry conditions during the deposition of the Irati Formation, as seen in the 30-m-thick carbonate layer extending through four South American countries.