Bashkirian-Moscovian (Lower–Middle Pennsylvanian) conodonts from the Amazonas Basin, northern Brazil: Biostratigraphy, biofacies, and paleobiogeographic significance for Western Gondwana

Bashkirian-Moscovian (Lower to Middle Pennsylvanian) Itaituba Formation is well exposed in the Itacimpasa Quarry at the southern platform of the Amazonas Basin, northern Brazil. An abundant and diverse conodont fauna was recovered from this predominantly carbonate formation, with a total of 19 species belonging to 8 genera identified. The following species were documented and systematically described for the first time in the basin: Declinognathodus marginodosus, Declinognathodus donetzianus, Idiognathoides postsulcatus, Idiognathoides fossatus, Diplognathodus benderi, Adetognathus spathus, and Idioprioniodus conjunctus, providing significant stratigraphic and environmental insights into the Bashkirian-Moscovian boundary (BMB) interval. The Declinognathodus marginodosus – Neognathodus atokaensis (upper Bashkirian Stage) and the Declinognathodus donetzianus – Diplognathodus ellesmerensis (lower Moscovian Stage) zones are recognized. The distribution of conodonts studied through cluster analysis reveals the conodont biofacies Idiognathodus/Adetognathus and Declinognathodus/Idiognathoides biofacies. Changes in these conodont biofacies are interpreted as the result of a marine ingression event in Western Gondwana during the BMB interval. The fauna recorded in the studied section shows affinities with conodont faunas reported from Paleo-Tethys Ocean regions indicating a faunal connection of this ocean with the Panthalassa in Western Gondwana. These findings contribute significantly to the refinement of the biostratigraphy and paleobiogeography of the Bashkirian-Moscovian boundary interval in the Amazonas Basin and Western Gondwana.