As opposed to dominant mode of ecological transition in the evolution of marine mammals, different lineages of toothed whales (Odontoceti) have repeatedly invaded freshwater ecosystems during the Cenozoic era. Notably, this assemblage of broadly convergent taxa has a biogeographic distribution across different freshwater river systems of South Asia and South America, and in estuarine and coastal waters of the latter as well. While work for most of 20th century implied or proposed that the river dolphins were all most closely related to one another (e.g., Simpson, 1945), the advent of molecular phylogenies clarified that these lineages are not all directly related to one another (see Geisler et al., 2011 PH-797804 for a useful summary), although both molecular and morphological analyses consistently group the two South American genera, and within Delphinida (i.e., Inioidea + Delphinoidea outside of Delphinida. and have only been grouped together in analyses using purely morphological datasets PH-797804 PH-797804 (e.g., Geisler & Sanders, 2003). With restricted distributions, serious conservation threats, and relatively low taxonomic richness compared with other odontocete clades, the evolutionary history of river dolphins remains a topic of perennial interest (Cassens et al., 2000; Hamilton et Fgfr2 al., 2001; Nikaido et al., 2001; Pyenson, 2009; Ruiz-Garcia & Shostell, 2010; Turvey et al., 2010; Geisler et al., 2011). The fossil record of South Asian river dolphins can be poor, without taxa reported from undisputable continues to be (e.g., in South Asia, nonetheless it is in keeping with the wide-spread distribution of fossil platanistoids reported somewhere else in the globe from past due Paleogene through Neogene stones along the coasts from the South and North Pacific as well as the North Atlantic oceans (Fordyce, 2009). Likewise, the fossil record of inioids stretches well beyond SOUTH USA (Fig. 1). Fossil pontoporiids have already been referred to from shallow sea and estuarine strata of early past due Miocene to Early Pliocene age group through the Atlantic coastline of THE UNITED STATES, including Maryland, Virginia, NEW YORK and Florida (Morgan, 1994; Whitmore, 1994; Godfrey & Barnes, 2008; Gibson & Geisler, 2009; Geisler, Godfrey & Lambert, 2012). Along the Atlantic coastline of European countries, sp. and indeterminate Pontoporiidae) through the marine Gram Development in Denmark, which can be early past due Miocene age group. To date, no fossil pontoporiids have been described from the North Pacific Ocean. The two species of (Geisler, Godfrey & Lambert, 2012), although is sometimes also grouped with and skeletal remains using a Flip camera (Cisco Systems Inc., San Jose, California, USA) on time-lapse settings. Later, subsequent to the specimens preparation in the Department of Paleobiology, we used computed tomography (CT) to scan the type specimen USNM 546125 in the Department of Anthropology with a Siemens Somatom Emotion 6 at slice thickness of 0.63 mm (which results in a three-dimensional reconstruction increment of 0.30 mm). The resultant DICOM files were processed by loading image files in Mimics (Materialise NV, Leuven, Belgium), and a mask was created based on the threshold of bone, relative to the nominal density of air. We then created a three-dimensional (3D) object from this mask, and exported the resultant file as an ASCII STL, which was opened in Geomagic (ver. 2012) for final imaging edits. We also attempted to use laser surface scanning (i.e., laser arm scanner) to capture 3D data, but line of sight issues with overhanging morphological features and the geometric complexity of the type specimen prevented a full capture of the surface geometry. As a result, we elected to use the 3D models of the skull, mandibles, and scapula generated from CT data because this method provided complete capture of the external and internal morphology. After converting the CT files into 3D data, the watertight model was then processed in Autodesk Maya (ver. 2013) by Pixeldust Studios (Bethesda, Maryland, USA), decimating the models to 100,000 triangles and creating diffuse, normal, and occlusion texture maps. The resultant 3D surface model datasets, processed from the computed tomography scans, provided sub-millimeter accuracy, and full resolution files can be downloaded at the open-access Smithsonian X 3D browser (http://3d.si.edu). These files, along with supplemental ones, are also archived at Zenodo (http://zenodo.org) at the following DOI: 10.5281/zenodo.27214. Phylogenetic analysis Recent work on the systematics of living and extinct odontocetes has recently provided several phylogenetic frameworks to use in this study. Geisler et al. (2011) used a combined morphological and molecular analysis to clarify the relationships among extant PH-797804 and fossil lineages of cetaceans, with mostly a focus on odontocetes, including some important fossil taxa, but taxon sampling within Inioidea was relatively sparse compared to Geisler, Godfrey & Lambert (2012). This latter work, which described as an operational taxonomic unit to the Aguirre-Fernndez & Fordyce (2014) matrix of 311.