Yagonia Roberts (Brachiopoda: Chonetidina) from the Malimán Formation, Lower Carboniferous of western Argentina: palaeobiogeographical implications

Abstract

A new anoplid chonetid species, Yagonia furquei sp. nov., is described from the Lower Carboniferous (late Tournaisian–early Viséan) Malimán Formation of western Argentina. The associated temperate ‘Malimanian’ fauna is suggested to indicate an initial biotic segregation that took place in western Gondwana (southwestern South America), a palaeobiogeographic event that predated the late Viséan global cooling and associated major palaeolatitudinal biotic differentiation. Occurrences of Yagonia are here interpreted as evidence of a ‘south to north’ faunal migration pathway, here named the Austropanthalassic–Rheic oceanic corridor, established in western Gondwana during the late Early Carboniferous.

Key words:

• Brachiopoda
• Yagonia
• Malimanian fauna
• Malimán Formation
• Early Carboniferous
• South America
• palaeobiogeography

Acknowledgements

All comments by reviewers Dr Gabriela Cisterna and Dr Michael Mergl and Alcheringa's editor in Chief, Dr Stephen McLoughlin, helped to improve the manuscript. Dr G. Cisterna deserves special gratitude, since she kindly provided additional topotypic material of Yagonia furquei sp. nov. that allowed more detailed morphological description and characterization of the new species. ACT extends his gratitude to Dr Carlos R. González, Mr Miguel A. Aredes and Mr Ricardo Brizuela for field assistance and Mr Mario Campaña for drawings. His thanks are also extended to the Evolution and Biodiversity Research Laboratory (LIEB) of the ‘San Juan Bosco’ Patagonian National University and the Palaeontological Institute of the Miguel Lillo Foundation, which provided laboratory facilities. Financial support was supplied by ANPCyT (Argentina) with the Project PICTR2003-00313 ‘Biodiversity of the taphofloras and invertebrate faunas in upper Palaeozoic basins of Argentina and southern South America: Systematic, Biostratigraphic and Correlation’. GRS acknowledges continuing support from the Australia Research Council (DP0772161), which enabled Dr A.C. Taboada to visit Australia in 2008 for research collaboration.