Freshwater fish faunas from two Permian rift valleys of Zambia, novel additions to the ichthyofauna of southern Pangea

Abstract

Toward the end of the Paleozoic, Earth's land masses formed the supercontinent Pangea. Despite the relative lack of large-scale physical dispersal barriers, patterns of endemism and regionalization existed, likely driven by climate. During the later Permian the fossiliferous southern region of Pangea has proven to be remarkably homogeneous in terms of terrestrial floras and faunas. However, these signals among vertebrates are best documented amongst tetrapods, and little attention has been paid to freshwater fish assemblages often occurring in the same rocks. Given the increasingly arid and landlocked conditions of the interior of Pangea, the study of freshwater vertebrate communities can help contribute to an understanding of biogeographic patterns across the supercontinent. Here we report two Permian fish assemblages from the Madumabisa Mudstone Formation of Zambia consisting of actinopterygians and large-bodied elasmobranchs: 1) a middle Permian assemblage from the Mid-Zambezi Basin; and 2) a late Permian assemblage from the Luangwa Basin. These assemblages are compared with other middle and late Permian freshwater ichthyofaunas from Australia, Brazil, Chile and South Africa and found to reinforce signals of faunal homogeneity for terrestrial assemblages found using the richer and more well-documented tetrapod fossil record.