Rare Carboniferous and Permian glacial and non-glacial bryophytes and associated lycophyte megaspores of the Paraná Basin, Brazil: A new occurrence and paleoenvironmental considerations

Abstract

Fossil bryophytes are rare because their preservation is compromised by the presence of a thin cuticle (if any) and a lack of lignin. Except for the occurrence of one bryophyte in the glacial Dwyka Group of the Karoo Basin, the other rare Late Paleozoic records in Gondwana are notably from the Paran a Basin in Southeast/South Brazil. Four bryophyte sites (including a newly discovered one) were found in the lower part of the thick Permo-Carboniferous glacial succession of the Itarar e Group, and one was found in the Guadalupian Teresina Formation, which was roughly assigned to an epeiric sea (or "lake") dominated by a warm, semi-arid climate. This study describes the fossils from the new occurrence from the Itarar e Group and discusses the context in which the bryophyte beds originated in the basin. The new samples confirm that all of the bryophytes of the Itarar e Group can be classified as Dwykea araroii Ricardi-Branco et al. (a possible pleurocarp) and are associated with the lycophyte megaspore Sublagenicula brasiliensis (Dijkstra) Dybov a-Jachowicz. In the much younger Teresina Formation, the bryophytes are Yguajemanus yucapirus Cristiano-de-Souza et al. and Capimirinus riopretensis Cristiano-de-Souza et al., and abundant charophytes and rare dwarf lycophyte stems and bracts are present in the same layers. Although the two stratigraphic units represent distinct paleoenvironments and climates, they seem to share some characteristics: a) the bryophyte assemblages were transported very little; b) they were deposited in very calm environments; c) they were the main components (along with some lycophytes) of local or poorly diversified regional vegetation. The low number of species, which is characteristic of opportunistic communities, can be explained by local or regional conditions that would have been stressful for the vascular plants in other areas. During the deposition of the Itarar e Group, the main control was probably the cold climate in addition to a relative (liquid) water deficit because the bryophyte vegetation may have belonged to a tundra biome in areas of retreating glaciers. For the Teresina Formation, it is possible that the control was scarce freshwater, an unstable environment and water-saturated soil in a scenario of bryophyte vegetation living around temporary ponds in a wide marginal area of the epeiric sea.

Descrições e reconstruções de aracnídeos fósseis do Brasil

“…. The studied gametophytes bear wider and shorter phyllids than Dwykea goedehoopensis from Africa (comparisons in Table 1), what reinforces the previous justification for the proposal of the species D. araroii Ricardi-Branco et al, 2013. The new analysed specimens present little wider phyllids than those in Ricardi-Branco et al (2013) (0.3 mm instead of 0.2 mm) and, in general, the stems are more fragmented, not reaching half the length of some previously described specimens.…”

“…Dwykea sp. and synonymized with D. araroii in Ricardi-Branco et al (2013), with a 0.6 mm long and 0.04 mm wide seta, holding a 0.2 mm long and 0.08 mm wide capsule.…”

Projeto geobike

“…2A). Bryophyte and spore fossils belonging to the Carboniferous megaflora are identified in the pelitic rocks (Perinotto & Lino et al, 2007, Ricardi-Branco et al, 2016 (Fig. 2B).…”