Fossil Cetaceans (Mammalia, Cetacea) from the Neogene of Colombia and Venezuela

Abstract

There are significant geographic gaps in our knowledge of marine mammal evolution because most fossils have been found and described from Northern Hemisphere localities and a few other high-latitude areas in the Southern Hemisphere. Here, we describe fossil cetacean remains from five geological units in the South American tropics (Urumaco, Codore, Castilletes, Cantaure, and Querales formations) generally representing marginal marine depositional environments (estuaries, deltas, and tidal flats). While fossil cetaceans from Venezuelan Neogene localities have been previously studied, this paper includes the first descriptions of fossil cetaceans from Colombia, including a diverse assemblage of mysticetes and odontocetes. We identified and provisionally referred fragmentary remains to the iniid Ischyrorhynchus vanbenedeni and to the platanistid Zarhachis flagellator. The latter suggests the presence of Platanistidae in the eastern coast of South America during the early-middle Miocene, representing the second record of Platanistidae in South America and the first record of Platanistidae in eastern South America. Other less-diagnostic specimens are characterized by features commonly seen in longirostrine odontocetes such as Iniidae, Platanistidae, Pontoporiidae, Lipotidae, Eoplatanistidae, and Squalodelphinidae.