Paleocomunidades e Paleoambientes do Devoniano da Bacia do Paraná, Brasil

Abstract

The Devonian sedimentary succession of the Paraná Basin presents an endemic fauna of benthic marine invertebrate organisms, constituting associations of brachiopods, arthropods, mollusks, cnidarians, echinoderms, and annelids. These paleoecological groupings were proposed by Arthur James Boucot in 1971, and are subdivided into four paleocommunities: Lingula, Notichonetes, Eocoelia, and Australospirifer. However, as taphonomic investigations were rare at the time, some fossil groupings that were displaced from their original habitat or had their placement reoriented were mistakenly interpreted as constituents of the paleocommunities. Therefore, much of what was understood as part of the paleocommunities may have been transported, as well as the presence of species that did not coexist in time, pointing to time-averaged paleocommunity. In this perspective we aimed to analyze the ecological associations proposed by Boucot under a tafonomic perspective, allowing us to infer if the groupings present in Devonian outcrops can be considered as representatives of paleocommunities and to infer their respective paleoenvironments. For this purpose, an extensive bibliography was analyzed in conjunction with paleobiogeographic and biostratigraphic observations. In the end, three different palaeocommunities were obtained (Infaunal Lingulids, Australospirifer e Pleurochonetes + Australocoelia), distinct in positioning and organization from those previously proposed by Boucot. They were distributed between shoreface and transitional offshore. In addition, the trophic guilds (Suspension feeders, Debris-eaters, Herbivores and Carnivores) and functional groups (Burrow-makers, Filter-feeding, Decomposers, Predators and Grazers) responsible for maintaining the environment were characterized. From this work we can extend the paleoecological knowledge of benthic marine invertebrates, thus arriving at an extensive paleoecological analysis of the component fauna of the Malvinoxhosan Bioregion belonging to the Paraná Basin.