Systematics and palaeogeographical implications of Early Devonian bivalves from the Ponta Grossa Formation, northwest border of the Paraná Basin, Brazil

Abstract

We report a remarkable Early Devonian, fully marine, bivalve-dominated assemblage from the Ponta Grossa Formation, Jaguariaíva Member, in the Alto Garças Sub-basin, northwestern Paraná Basin, Brazil. This discovery enhances our understanding of benthic invertebrate distribution within the basin. The assemblage includes cosmopolitan species (Nuculites africanus, Nuculites sharpei, Nuculites sp. Palaeoneilo magnifica, Nuculana viator, ‘Acharax’ bainii, and Pholadella epops), a new bivalve (Devonomya gondwanica gen. et sp. nov.), and indeterminate species (Anomalodesmata indet.). Excellent preservation reveals internal features (e.g. hinge, muscle scars), documented here for the first time in some species (e.g. Pholadella epops). The bivalves, mostly preserved in concretions, exhibit closed articulated shells without abrasion and fragmentation, some possibly preserved in situ, suggesting an autochthonous to parautochthonous origin. Shallow infaunal deposit-feeders dominate, followed by infaunal suspension-feeders. They thrived in low-energy, offshore-prodeltaic settings with fine-grained, organic-rich siliciclastic sediments under oxygen-deficient conditions. The identified species occur across Gondwana, some shared with South Africa, the Falkland Islands/Malvinas, and Antarctica. They are also found in coeval Pragian-Emsian strata of the same unit in southern Brazil, confirming a connection between the Alto Garças and Apucarana sub-basins during the Early Devonian marine transgression.urn:lsid:zoobank.org:act:0283CAEE-CD1A-4FDD-8F2A-2DB4A1EE1D86urn:lsid:zoobank.org:act:9F8B57AD-5FC0-4DB0-A3A8-A7F6A5FD01BD