Vermes tubícolas: revisão taxonômica, distribuição geográfica e estratigráfica no devoniano da bacia do Paraná, Brasil.

Abstract

Tubeworms are an informal designation for a biological group of animals associated to rigid tubes production around their bodies. By encompassing organisms from different phyla, and presenting a wide stratigraphic distribution, controversies of taxonomic and biostratigraphic nature have been related to the group which does not distintly present itself to the Devonian Period in the Paraná State. Furthermore, the region group occurrences, in the bibliography, suggests an association with immediate postextinction environments. Thus, the main objective of this study is to elucidate the taxonomic, and biostratigraphic implications of tubeworms in the Devonian of Paraná, as a basis for paleoenvironmental interpretation. In addition to the required bibliographic review, we selected 229 samples containing one or more fossils of tube worms, representing 2,203 bioclasts from the collections deposited at the Laboratory of Stratigraphy and Paleontology of the Department of Geosciences of the Ponta Grossa State University (UEPG-DEGEO). Through the taxonomic revision, we could observe that Serpulites sp. was a valid taxon for the region and ?Vestimentifera was an invalid one, being its specimens representative of the genus Annulitubus. There is also a record of the new species Cornulites auxilium. Annulitubus is the most numerou taxon of tubers in the region, allowing interpretations related to its morphology, way of life, and stratigraphic distribution. It was found that the genus diagnosis was based only on a part of the animal, which presents a morphological variation along the tube representing three stages of deposition of the tube. This characteristic, added to the possibility that they were chemosymbiont animals due to the presence of sulfur in analyzed samples, enable to classify Annulitubus genus as belonging to the Siboglinidae family. Annulitubus represents animals of the Malvinocafric Province, with occurrences since the Neo-Praguian, not being members of an adventitious fauna as previously proposed. They represent opportunistic species, possibly with a chemosymbiotic livelihood, verified by their increased occupation of eco-space in a post-biotic crisis context, where their population becomes abundant whereas the others become scarce. Thus, the biostratigraphic implications of the Annulitubus presence are extremely important regarding to the paleoenvironmental interpretation, and deserves greater attention and studies, also considering aspects related to the paleoecology of these animals, especially concerning to their paleoautoecological implications.