DOI: 10.15468/g9fzmq
title: A new odontocete (Inioidea, Odontoceti) from the late Neogene of North Carolina, USA

description: This dataset contains the digitized treatments in Plazi based on the original journal article Godfrey, Stephen J., Gutstein, Carolina S., Morgan Iii, Donald J. (2021): A new odontocete (Inioidea, Odontoceti) from the late Neogene of North Carolina, USA. Fossil Record 24 (2): 275-285, DOI: 10.5194/fr-24-275-2021, URL: http://dx.doi.org/10.5194/fr-24-275-2021Abstract. A new monotypic genus of Neogene odontocete (Isoninia borealis) is named on the basis of a partial skull (CMM-V-4061). The holotype was found on the riverbed of the Meherrin River (North Carolina, USA) and probably originated from the Miocene marine Eastover Formation. Deep interdigitation of the cranial sutures indicates that this individual was mature. The new taxon differs from all other delphinidans in the unique combination of the following characters: anteriorly retracted premaxillae and maxillae; premaxillae not contacting nasals; thick nasals with ventrolateral margins deeply imbedded within corresponding troughs in the frontals (this is an apomorphy); nasals with transversely convex dorsal surface; nearly symmetrical vertex; os suturarum (or interparietal or extra folds of the frontals) at the vertex; large dorsal infraorbital foramen level with the posterior margin of the external bony nares; and a postorbital recess on the ventrolateral face of the frontal below and behind the postorbital process of the frontal. This odontocete exhibits two small but pronounced concavities on the cerebral face of the frontal/presphenoid that are presumed to have held vestigial olfactory bulbs in life. Inioidea is only diagnosed by a single unequivocal synapomorphy: width across nasals and nares subequal. Isoninia shares this feature with other inioids and forms the basis for the placement of Isoninia within this clade. A relatively high vertex coupled with a supraoccipital that is deeply wedged between the frontals suggests placement of this new inioid species within the family Iniidae. This is the second inioid described from the Eastover Formation (the other being Meherrinia isoni). This new species adds new cranial morphology and a new combination of cranial characters to this taxonomically small but growing group of mostly marine and mostly Western Hemisphere odontocetes (urn:lsid:zoobank.org:pub: E8B817CAB250-42B3-9365-36EFBFE351C9).1 IntroductionThe extant South American river dolphins (Inia and Pontoporia) are traditionally grouped in the Inioidea (sensu de Muizon, 1988), a conclusion with which more recent work is in agreement; however, there has been some discussion of whether its sister group is the Yangtze river dolphin (Lipotidae) or modern marine dolphins (Delphinoidea) (Arnason and Guldberg, 1996; Yang and Zhou, 1999; Yang et al., 2005; Cassens et al., 2000; Hamilton et al., 2001; Nikaido et al., 2001; Cozzuol, 2010; Geisler and Sanders, 2003; McGowen et al., 2009; Geisler et al., 2011, 2012; Gatesy et al., 2013; Pyenson et al., 2015; Post et al., 2017; Lambert et al., 2017, 2018, 2020; McGowen et al., 2020). Extant Inioidea are comprised of two monotypic families (Ruiz-Garcia and Shostell, 2010), Iniidae Gray, 1846, and Pontoporiidae Gill, 1871. Inia is a strictly freshwater form that includes three living species: Inia geoffrensis (de Blainville, 1817) found within the Orinoco and Amazon river basins, Inia boliviensis (Banguera-Hinestroza et al., 2002) that inhabits the Beni– MamorØ river basin, and possibly Inia araguaiaensis (Hrbek et al., 2014) from the Araguaia– Tocantins river basin. Pontoporia is monotypic (P. blainvillei; Gervais and d’Orbigny, 1844) and occupies shallow marine and estuarine environments along the southeastern coast of South America, with some entrance into proximal riverine systems including Babitonga Bay, southern Brazil (Cremer and Simıes-Lopes, 2005), and the La Plata river of Argentina and Uruguay (Casinos) (Secchi, 2010).The Pontoporiidae (sensu Geisler et al., 2012) is known from the late middle Miocene to the Holocene. Several authors (Lambert and Post, 2005; Godfrey and Barnes, 2008; Gutstein et al., 2009; Lambert and Muizon, 2013; Pyenson and Hoch, 2007; Pyenson et al., 2015; Post et al., 2017; Lambert et al., 2020) have detailed the geographic and stratigraphic extent of the extinct members of this family, which includes small-bodied, mostly coastal odontocetes with rostra ranging from short to long.Extinct iniids include Kwanzacetus khoisani Lambert et al., 2018, from the Kwanza Basin, Angola; the Argentinian forms Ischyrorhynchus vanbenedeni Ameghino, 1891 (Cozzuol, 1985, 1996, 2010; Cione et al., 2011; Pyenson et al., 2015), Saurocetes argentinus Burmeister, 1871, and S. gigas Cozzuol, 1989, all from the late Miocene Ituzaingó Formation (Cozzuol, 1989, 1996); a Pleistocene species of Inia from Brazil (Cozzuol, 2010); Isthminia panamensis Pyenson et al., 2015, from the late Miocene Chagres Formation of Panama; Brujadelphis ankylorostris Lambert et al., 2017, from the late Miocene Pisco Formation, Pisco Basin, in Peru; and Goniodelphis hudsoni Allen, 1941, from the late Miocene Bone Valley Formation of Florida, USA (Morgan, 1994).Within Inioidea, several taxa move from one family to the other in successive phylogenetic analyses, which indicates that for some species final family attribution is not yet settled. Furthermore, eventually some of those could even fall as stem inioids, branching before the node Iniidae + Pontoporiidae.The discovery of marine iniids has fostered a discussion about the Mio-Pliocene global distribution of inioids in general and has raised questions about the timing and paleobiology of the origin and diversification of marine forms and of the extinction of most iniids except for the exclusively freshwater South American riverine forms (Cassens et al., 2000; Gutstein et al., 2014; Pyenson et al., 2015).Odontocetes, including inioids, present a dizzying array of cranial morphologies. Our goal here is to add to that diversity by describing and naming a new genus and species of inioid from the late Neogene of North Carolina (USA).