Paleoecologia dos peixes ósseos da formação Pirabas

Abstract

The Pirabas Formation is interpreted as a transgressive depositional event that occurred in the Lower Miocene, whose record of outcropping rocks is best represented in the northeastern region of Pará. The invertebrate and vertebrate communities, continental and coastal floras, and microfossils indicate the existence of tropical paleoenvironments ranging from shallow open platforms to reefs, lagoons and mangroves. The focus of research to date has been on determining the age of the geological unit, based on systematic review studies, and subordinately few papers presenting paleoecological aspects. Within this scenario, bony fishes, despite their high potential to generate and test hypotheses about paleoecological aspects, have not received more attention from researchers. In this work we carried out an ecological characterization of the bony fish community, based on the requirements of its present representatives, in order to contribute to the paleoenvironmental interpretation and the elaboration of a database on the geology and paleoecology of the Pirabas Fonnation. The material studied consists of 34 specimens, distributed in four genera, with the endemic species: Spbyraena cunbai, Spbyraena egleri and Diodon ferreirai; and Arius pp. represented by teeth, dental plates, dorsal spines and otoliths. The specimens come from the state of Pará and are deposited in the Paleontology collection of the Goeldi Museum. The families of bony fishes from the Pirabas Formation are predominantly tropical and corroborate the presence of diverse environments: A) regarding the occurrence of lagoons: not only Ariidae occur mainly in estuarine and marine waters and eventually in fresh waters, but also several species of Sphyraenidae occur in estuaries; B) regarding the presence of mangroves: several species of Spbyraena use mangrove areas as nursery; C) regarding the presence of coral reefs: most species of Diodon and several species of Sphyraena are associated with reef environments.