New clues on the palaeodiversity of the middle Miocene freshwater ichthyofauna from the Tatacoa Desert, Colombia

The middle Miocene rocks of the Honda Group (La Victoria and Villavieja formations) in the Tatacoa Desert, Upper Magdalena River Valley, Colombia, possess one of the best studied continental faunas of the Neotropics, ranging in age from c. 16 to c. 10.5 Ma. The fossil record of the region shows a high diversity of fishes, crocodylians, snakes, lizards, turtles, and aquatic/terrestrial mammals. Here we present a new overview of the freshwater fish palaeodiversity and its biostratigraphic context. The new data includes the description of a new fossil catfish †Sciades maldonadonis n. sp., the putative first fossil record of the cichlids Astronotus and Cichla, the first report for the region of the thorny catfish Oxydoras, and taxonomical comments on some taxa previously reported for this stratigraphic unit. With a palaeodiversity tentatively represented by at least 23 taxa of chondrichthyans and bony fishes, the Honda Group preserves one of the most diverse Miocene freshwater fish fauna so far known from the Neotropics. The taxonomical and biogeographical affinities of the fossil fish assemblage, with extant taxa in the Orinoco and Amazonas river systems, sustain the hypotheses of drainages flowing from western Amazonia into the proto-Caribbean Sea. This middle Miocene fish assemblage also offers significant evidence for the evolutionary history of the Neotropical freshwater fishes and ancient environments.