Review and update of the benthic paleocommunities of the Malvinoxhosan Bioregion, a case study in the Paraná Basin, Brazil

Abstract

In 1971, Arthur James Boucot proposed the first paleocommunities for Devonian benthic marine invertebrates of the Malvinokaffric Realm: Lingula, Australospirifer, Eocoelia, and Notichonetes. However, since taphonomy was not widely applied at the time, some aspects were not considered. This work aims to revise these paleocommunities, taking those factors into account. Based on field observations, laboratory sample analysis, and literature review, the following paleocommunities are proposed: a) “Australospirifer”; b) “Infaunal Lingulids” (a provisional name until a taxonomic revision of Lingula is conducted); and c) “Pleurochonetes + Australocoelia”. These are positioned within the following paleoenvironmental settings: Lower Shoreface (first two) and Lower Shoreface to Offshore Transition (last one). These changes are justified by: (1) The Australospirifer Paleocommunity is retained, as it was identified both in the field and laboratory, except for some transported material previously interpreted as in situ. (2) The so-called Lingula paleocommunity is a thanatocoenosis, and the genus Lingula is no longer considered Paleozoic, making it unsuitable as a representative taxon. (3) The Eocoelia and Notichonetes paleocommunities may represent a single group, as they are often found together in the same paleoenvironment and sometimes in life position. Boucot's paleocommunities are a reference for the Devonian of the Paraná Basin but require updates due to numerous recent discoveries and the integration of new fields such as taphonomy and ichnology. Therefore, this work presents an updated arrangement of the Devonian paleocommunities in the Paraná Basin, based on field evidence and recent studies.