A new platanistoid, Perditicetus yaconensis gen. et sp. nov. (Cetacea, Odontoceti), from the Chattian–Aquitanian Nye Formation of Oregon

The Platanistoidea is a large superfamily of odontocetes whose sole surviving member is Platanista gangetica, the Ganges river dolphin. Despite the diversity of the Platanistoidea, it remains poorly understood and in need of revision. As one of the earliest-diverging clade of crown odontocetes, understanding their distribution, morphology, and phylogeny is crucial to understanding the radiation of archaic odontocetes in the late Oligocene to the middle Miocene. Here we describe an archaic odontocete, named Perditicetus yaconensis, gen. et. sp. nov., from the latest Oligocene–earliest Miocene Nye Formation in Oregon. Perditicetus yaconensis, represented by the holotype USNM 335224, possesses several synapomorphies of the Platanistoidea. Intriguingly, strong morphological similarities exist between P. yaconensis and other archaic odontocetes in the ‘Chilcacetus clade’ especially in the vertex and pterygoid region. However, the results of our phylogenetic analyses failed to capture any phylogenetic relationships between Perditicetus and Chilcacetus. In this analysis, P. yaconensis is sister taxon to the clade Allodelphinidae + Squalodelphinidae + Platanistidae and we consider that P. yaconensis is one of the basal-most derived platanistoids. The type locality of the holotype specimen, in the Nye Formation, provides a window into the diversity of archaic odontocetes, especially platanistoids, during the latest Oligocene to earliest Miocene. http://zoobank.org/urn:lsid:zoobank.org:pub:9B370DA2-8035-4A12-929C-D8FCA84438AE