ACKNOWLEDGMENTS
We are grateful to J. Hutchinson who brought the ziphiid partial skull to the USNM. D. Bohaska (USNM), J. Mead (USNM), and C. Potter (USNM) generously provided access to the collections of both fossil and extant ziphiids in their care. L. E. Edwards (U.S. Geological Survey) identified the microfossils; we are very grateful for her expertise. Comments by G. Bianucci, an anonymous reviewer, and JVP Editor J. H. Geisler improved the quality of an earlier version of this article. This publication would not have been possible without funding from the Board of Calvert County Commissioners, the Citizens of Calvert County, Maryland, and the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum. We would also like to acknowledge the Citizenship and Immigration Services of the U.S. Department of Homeland Security for issuing the visa to A. Fuller, which allowed her to begin this study as a research intern at the Calvert Marine Museum. The work of O.L. at the IRSNB is financially supported by the Research Project MO/36/016 of the Belgian Federal Science Policy Office.