Late Jurassic lungfishes (Dipnoi) from Uruguay, with comments on the systematics of Gondwanan ceratodontiforms

Abstract

ABSTRACT We describe herein the only known fossil dipnoans from Uruguay, recovered from continental deposits of Kimmeridgian–?early Cretaceous age (Batoví Member of the Tacuarembó Formation). The material includes several tooth plates referred herein to “Ceratodus” tiguidiensisTabaste, 1963 (the current generic assignment being either Arganodus or Asiatoceratodus), and one to Ceratodus africanusHaug, 1905. “C.” tiguidiensis was so far only recorded in the Upper Jurassic–Lower Cretaceous of Saharan Africa and the ‘middle’ Cretaceous of Brazil (and perhaps the Lower Triassic of Australia), and C. africanus in the Lower to Upper Cretaceous of Saharan Africa and the ‘middle’ Cretaceous of Brazil. Hence, these are the oldest and southernmost South American records of both taxa, and the oldest and southernmost record of C. africanus in the world. These findings reveal an unrecognized dipnoan diversity in South America prior to ‘middle’ Cretaceous times. In the Late Jurassic–Early Cretaceous of western Gondwana only the ceratodontiform genera Ceratodus, Arganodus/Asiatoceratodus, and Retodus were present, Neoceratodus being absent. The Tacuarembó Formation paleoichthyofauna comprises a low-diversity freshwater assemblage including, besides dipnoans, putative semionotids (the most abundant fossils) and hybodontid sharks.