Trilobitas Malvinocáfricos da Sub-bacia Alto Garças (Devoniano Inferior, Bacia do Paraná, Brasil): composição e taxonomia.

Abstract

We have identified and described new specimens of trilobites attributed to the families Calmoniidae and Homalonotidae, in the northwestern portion of the Paraná Basin, Alto Garças Sub-basin, Chapada 2 Group (Pragian-Emsian). Six calmoniid species from five different genera and one species of Burmeisteria, collected in the region of the municipality of Rio Verde de Mato Grosso (MS), expand the composition of the Devonian trilobite fauna in this part of the Basin. Considering the connection of the sub-basin with the Andean region of Bolivian outcrops and two other contemporary Brazilian depositional units (Parnaíba Basin and Apucarana Sub-basin), we observe the biostratigraphic position of components of this fauna and their correlation with these units. Metacryphaeus meloi Carvalho, Edgecombe & Lieberman 1997, unprecedented in the Paraná Basin, reveals itself here in the oldest biostratigraphic position in relation to specimens reported in outcrops of the Passagem Member of the Cabeças Formation, Parnaíba Basin, of Frasnian-Fammenian age, as well as Burmeisteria notica and Metacryphaeus australis Clarke 1913 in other outcrops, less recent, of that same Basin. The present investigation also revealed Pennaia pauliana Clarke 1913, Calmonia signifer Clarke 1913 and Kozlowskiaspis subseciva (Clarke 1913). Unpublished specimens of Bainella are here diagnosed as a new species, their distinction within the subgenera Bainella (Bainella) and Bainella (Belenops) Eldredge & Braniša 1980, while indicating a possible path of paleogeographic dispersion. The distribution of species in the Paraná Basin is raised here, listing the currently valid species.