A new genus and species of late Miocene inioid (Cetacea, Odontoceti) from the Meherrin River, North Carolina, U.S.A.

ABSTRACT

A new genus and species of extinct inioid odontocete (Meherrinia isoni) is based on nine partial crania that probably originated from the late Miocene marine Eastover Formation in North Carolina, U.S.A. They were collected from the riverbed of the Meherrin River, a tributary of the Chowan River. Ossification of the mesethmoid and the tight interdigitation of many sutures indicate that these specimens represent mature individuals. Key characteristics of the new inioid include maxillae that ‘squeeze’ the nasals into a slight hourglass shape and supraoccipital that is deeply wedged between the frontals and maxillae on the vertex. As compared to the extant iniid Inia geoffrensis (Amazon River dolphin) and the extant pontoporiid Pontoporia blainvillei (La Plata dolphin), Meherrinia is more plesiomorphic in having less elevated premaxillary eminences and supraorbital processes. In other respects Meherrinia is intermediate in morphology between the two extant genera of inioids. For example, the essentially symmetrical vertex is intermediate in height between the low and high vertices in Pontoporia blainvillei and Inia geoffrensis, respectively. A cladistic analysis of morphological and molecular data supports a sister-group relationship between Meherrinia and Inia; thus our new taxon is tentatively assigned to the Iniidae. If correct, this is the first iniid represented by diagnostic remains from marine deposits and just the second from North America.

ACKNOWLEDGMENTS

We express our deepest gratitude to R. Ison and J. Magura for collecting and donating the specimens of Meherrinia described herein to the Calvert Marine Museum and M. Bosselaers for purchasing and donating one specimen to the IRSNB. C. Mehling brought the skull now catalogued as CMM-V-4060 to the attention of J.H.G. and facilitated the donation of this specimen by J. Magura to the Calvert Marine Museum. J. G. Mead (USNM), C. Potter (USNM), D. J. Bohaska (USNM), C. Lefèvre (MNHN), and G. Lenglet (IRSNB) are gratefully acknowledged for providing access to the collections of modern and fossil odontocetes in their care. We also thank G. Bianucci (University of Pisa) for providing unpublished photographs of Ischyrorhynchus material. J. Pojeta (USNM) provided liberal access to his laboratory where all but one of the skulls figured herein were whitened with sublimed ammonium chloride. M. Uhen's (George Mason University) detailed contributions to The Paleobiology Database were a most welcome resource.

For reviews of our manuscript, we are grateful to G. Bianucci and E. Fordyce and we appreciate the efforts of R. Holmes, who served as the handling editor of our article for JVP. This publication was made possible with funding to S.J.G. from the citizens of Calvert County, MD, its Board of County Commissioners, and the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum. This work was conducted with support from the National Science Foundation (DEB 1025260 to J.H.G.) and a postdoctoral grant of the Muséum National d’Histoire Naturelle, Paris (to O.L.).

Handling editor: Annalisa Berta