The Early Miocene odontocete Araeodelphis Natator Kellogg, 1957 (Cetacea; Platanistidae), from the Calvert Formation of Maryland, U.S.A.

ABSTRACT

On the basis of an assigned specimen (USNM 526604, from the Plum Point Member of the Calvert Formation, Early Miocene, Maryland, U.S.A.), Araeodelphis natator Kellogg, 1957, is referred to the Platanistidae. A phylogenetic analysis identifies A. natator as the most stemward member of the family. By contrast, the extant river dolphin, Platanista gangetica (Platanistidae), is one of the most specialized odontocetes. Araeodelphis natator exhibits the following unique combination of characters: overall skull length (condylobasal length) estimated at about 50 cm; rostrum twice the length of the facial region; rostrum wider than deep throughout its entire length; approximately 50 teeth in each quadrant of rostrum; mesorostral canal closed dorsally through anterior half of rostrum by apposition of contralateral premaxillae; cranium with elevated orbits directed anterolaterally; maxillary crest (supraorbital process of frontal and overlapping maxilla) modestly thickened laterally and elevated above midline of skull; non-pneumatized supraorbital eminences; lobe of the pterygoid air-sac sinus occupying orbital surface of frontal; zygomatic process compressed transversely; no postglenoid process; and glenoid facet faces medially. Araeodelphis provides new data about the definition and phylogenetic relationships of platanistids with other platanistoids, confirming the sister-group relationship with the extinct squalodelphinids and the ancestral platanistid skull morphology preceding the platanistine-pomatodelphinine split.

Citation for this article: Godfrey, S. J., L. G. Barnes, and O. Lambert. 2017. The Early Miocene odontocete Araeodelphis natator Kellogg, 1957 (Cetacea; Platanistidae), from the Calvert Formation of Maryland, U.S.A. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1278607.

ACKNOWLEDGMENTS

We sincerely thank R. E. Fordyce (University of Otago) for helpful comments and detailed reviews of several versions of the manuscript. M. D. Uhen (George Mason University) also included in his review for JVP many valuable recommendations for which we are very grateful. We are also indebted to J. Pojeta (USNM) for providing liberal access to his laboratory so we could whiten USNM 526604 with sublimed ammonium chloride to improve photographic contrast. N. D. Pyenson and D. J. Bohaska (both at the USNM) provided helpful access and loans of fossil odontocetes in their care. M. Parrish (USNM) scanned the images used to create Figure 5. Van Valkenburgh (editor, JVP) guided the manuscript through the publication process; many thanks!

This publication was made possible with funding from the citizens of Calvert County, MD, the Board of Calvert County Commissioners, and the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum. Travel and other support were provided to L.G.B. by the Natural History Museum of Los Angeles County, by its Foundation, and by the Fossil Marine Mammal Research Account of the Museum's Foundation, and to O.L. by the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum.