Godfrey et al.—New specimen of Agorophius pygmaeus (Odontoceti, Cetacea) With the assignment of both ChM PV4256 and SC


2015.51.1 to Agorophius pygmaeus, it is now possible to accurately characterize the family and thankfully, we can now move beyond the problems created by not knowing the whereabouts of the type. Although much more remains to be learned about the osteology of Agorophius pygmaeus, identify- ing some of the morphological features that characterize the family should facilitate the assignment of undescribed odonto- cetes to the Agorophiidae or not. Obviously, this monotypic family exhibits little morphological variation as compared to the more diverse Xenorophidae (Geisler et al., 2014; Uhen, 2008b). Some of that inequity will diminish as more agorophiids are added to its ranks, and known taxa are reappraised in the light of the specimen described herein. In light of the phylogeny presented here, and in other recent publications (Geisler et al., 2012, 2014), Xenorophidae (inclusive of Archaeodelphis contra; Sanders and Geisler, 2015) is the most plesiomorphic clade of Odontoceti (albeit with some synapomorphies of their own) followed by the Ashleycetidae (Ashleycetus planicephalus), then Mirocetidae (Mirocetus riabinini) (Sanders and Geisler, 2015), followed byAgorophiidae (Agorophius pygmaeus +ChM PV 4178). Agorophiids exhibit odontocete symplesiomorphies that differentiate it from archaeocetes and mysticetes (following Geisler and Sanders, 2003 and references therein): lacrimal and jugal form posterior wall of the antorbital notch; premaxillary foramina present; premaxillary sac fossa mostly anterior to the antorbital notch; dorsal infraorbital foramina anterior to the antorbital notch; maxilla covers most of the supraorbital process of the frontal; posterior edge of nasals in line with gap between postorbital and zygomatic processes; nasals elevated above the rostrum (Uhen et al., 2008). Many of these odontocete symplesiomorphies, that give them an archaic odontocete look, relate to the degree to which its skull is telescoped. At first glance, what distinguishes Agorophius pygmaeus


from Neogene and Recent odontocetes are not its autapo- morphies but rather its most conspicuous plesiomorphy; i.e., parietals contributing to the skull roof comprising the intertemporal constriction. This easily identifiable plesio- morphy, inherited from basilosaurid archaeocetes, disappears from Oligocene odontocetes between Simocetidae (where the parietals still contribute prominently to the skull roof) and the more derived Patriocetidae (where the parietals are expressed only as a narrow crescent between the frontals and the supraoccipital). Other archaeocete characteristics include temporal fossae open dorsally, prominent nuchal (lambdoid) crests, broadly exposed palatines (Fordyce, 2002), two-rooted cheek teeth, multiple accessory denticles on the teeth, and a heterodont dentition (Uhen, 2008b).


Conclusions Accessibility of supplemental data


For much of the 20th century, the Agorophiidae had been considered to include both the phylogenetically and geologically oldest odontocetes (Fordyce, 1981, 2002).However, the loss of all but a single tooth of the type specimen of the type genus and species (Agorophius pygmaeus) upon which the family Agorophiidae was based frustrated attempts to clearly diagnose the family (beyond symplesiomorphies confirming its status as a grade family) and add to its rankswith any confidence species that


Supplemental data deposited in Dryad data package: http:// datadryad.org/handle/10.5061/dryad.d6jk5


References Abel, O., 1914, Die vorfahren der bartenwale: Denkschriften der Kaiserlichen Akademie der Wissenschaften Mathematisch-Naturwissenschaftliche Klasse, v. 90, p. 155–224.


167


share familial autapomorphies (Fordyce, 1981, 2002). The disciplined approach taken by Fordyce (1981, 2002) to abandon the grade familyAgorophiidae has paid offwith the establishment of several families of Oligocene odontocetes: the Ashleycetidae and Mirocetidae (Sanders and Geisler, 2015), the Simocetidae (Fordyce, 2002) and Xenorophidae (Uhen, 2008b). In recent phylogenetic analyses of cetaceans (Geisler, 2001; Geisler et al., 2012, 2014), these families, along with the Agorophiidae, comprise the most archaic odontocetes presently known. It comes as no surprise to us that the Agorophiidae was


considered central to odontocete origins and early evolution. The relatively few uniquely derived features exhibited by this family results in its basal position within the odontocete clade. When one compares that number to the many easily identifiable autapomorphies exhibited by xenorophids and simocetids, little wonder Agorophius pygmaeus featured so prominently in discussions of early odontocete evolution; it displays many characteristics that are intermediate between archaeocetes and more derived odontocetes. That there are some morphologically unexpected or unusual Oligocene odontocetes is suggestive of an early odontocete radiation, about which we are only beginning to learn.


Acknowledgments


The first two authors contributed equally to this publication. Additional preparation work on SC 2015.51.1 was completed by J. Velez-Juarbe and A. Jukar, including extraction of the periotic (SC 2015.51.1c) for study. D. Cicimurri, N. Pyenson, D. Bohaska, and J. McCormick kindly provided liberal access to the fossil odontocetes in their care. We extend out sincerest thanks to J. Pojeta for the use of his lab where SC 2015.51.1 was whitened with sublimed ammonium chloride. We have also benefitted greatly from discussions with R. E. Fordyce on how best to interpret this specimen. J. H. Geisler kindly helped integrate the data matrices from several previous publications prior to the addition of data for our phylogenetic analysis. The authors would also like to thank Coral Edge Adventures for technical and material support of fieldwork. Constructive comments provided by J. H. Geisler and


one anonymous reviewer improved upon our initial effort. J. Repetski helped with final checks. M. Silcox and S. Hageman guided this paper through the publication process for the Journal of Paleontology; thank you. SJG received funding from the Citizens of Calvert County,


Maryland, the Board of Calvert County Commissioners, and the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum.


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