Bohaskaia monodontoides, a New Monodontid (Cetacea, Odontoceti, Delphinoidea) from the Pliocene of the Western North Atlantic Ocean Author(s): Jorge Vélez-Juarbe and Nicholas D. Pyenson Source: Journal of Vertebrate Paleontology, 32(2):476-484. 2012. Published By: The Society of Vertebrate Paleontology URL: http://www.bioone.org/doi/full/10.1080/02724634.2012.641705 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Journal of Vertebrate Paleontology 32(2):476–484, March 2012 © 2012 by the Society of Vertebrate Paleontology ARTICLE BOHASKAIA MONODONTOIDES, A NEW MONODONTID (CETACEA, ODONTOCETI, DELPHINOIDEA) FROM THE PLIOCENE OF THE WESTERN NORTH ATLANTIC OCEAN JORGE VELEZ-JUARBE´ *,1,2 and NICHOLAS D. PYENSON2,3 1Laboratory of Evolutionary Biology, Department of Anatomy, Howard University, Washington, DC 20059, U.S.A., [email protected]; 2Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121 P.O. Box 37012, Washington, DC 20013-7012, U.S.A., [email protected]; 3Department of Paleontology, Burke Museum of Natural History and Culture, Seattle, Washington 98195, U.S.A. ABSTRACT—Here we describe Bohaskaia monodontoides, a new taxon of beluga-like odontocete cetacean from the early Pliocene Yorktown Formation of Virginia and North Carolina. Among odontocetes, Bohaskaia shares key characteristics of the rostrum and face with belugas (Delphinapterus leucas), narwhals (Monodon monoceros), and Denebola brachycephala from the late Miocene of Baja California, thus placing it as a member of the Monodontidae. It also displays autapomorphies that merit its placement in a new genus and species. Both Denebola and Bohaskaia occurred in warmer latitudes than those of extant monodontids, even accounting for extralimital records. Such data from the fossil record of Monodontidae indicates that putative cold climate adaptations of living monodontids might have appeared under different environmental conditions and that their Holarctic and sub-Arctic distribution is a relatively recent phenomenon. INTRODUCTION these finds includes material from the Lee Creek Mine, in North Carolina, which consists of an associated collection of isolated pe- The only extant members of Monodontidae Gray, 1821, riotics, a fragmentary mandible, and skull fragments (Whitmore include two iconic Holarctic cetaceans: narwhals (Monodon and Kaltenbach, 2008). Here we describe a new genus and new monoceros) and belugas (Delphinapterus leucas). Both species species of monodontid based on a nearly complete skull from the have been documented in Arctic and sub-Arctic waters (Stewart Yorktown Formation in Virginia, U.S.A., and refer some of the and Stewart, 1989; Heide-Jørgensen et al., 2002), with occa- aforementioned Lee Creek material to this new taxon. sional extra-limital occurrences recorded in temperate latitudes Geological Setting—The type specimen USNM 25819 was col- (e.g., Gladden et al., 1999). The fossil record of monodontids, lected from the Rice’s Pit locality of the Morgarts Beach Member however, indicates that this group was represented by extinct of the Yorktown Formation, in Hampton, Virginia, U.S.A. Hazel lineages that were distributed in lower, warmer latitude envi- (1971) recorded that USNM 25819 was collected from Locality ronments (Barnes, 1984; Barnes and Demer´ e,´ 1991), challenging 11 (now known as Rice’s Pit), approximately 45–75 cm below panselectionist interpretations of monodontid specializations a Pleistocene shell bed (dominated by the marine bivalve Ensis as adaptations to Arctic climate (e.g., Noren and Williams, sp.) in a clayey sand. Rice’s Pit is an extensive open excavation 2000; Williams et al., 2011). The oldest fossil monodontids pit, about 13.2 m deep, which exposes marine sediments from the date to at least the late Miocene, with Denebola brachycephala Pleistocene Tabb Formation, overlying the thicker Yorktown Barnes, 1984, from the late Miocene Almejas Formation of Baja Formation, whose uppermost section is relatively fossiliferous California, Mexico (Barnes, 1984). A Denebola-like form has and has previously yielded a monachine seal, Pliophoca etrusca been reported from the late Miocene San Mateo Formation of (Koretsky and Ray, 2008), and the type specimen of Balaena California, but it remains undescribed (Barnes and Demer´ e,´ ricei Westgate and Whitmore, 2002. It is unclear if these latter 1991). This distribution suggests that monodontids belonging to occurrences share the same precise stratigraphic provenance lineages other than extant ones had ranges that extended to tem- as USNM 25819, although it is likely, given that the marine perate latitudes at least by the late Miocene. With the exception mammal-bearing horizons at Rice’s Pit are restricted to the of a putative monodontid occurrence based on a single periotic uppermost, exposed horizons (Westgate and Whitmore, 2002). from the early Pliocene of Peru (Muizon and DeVries, 1985), Nearly all of the Yorktown Formation exposed at Rice’s Pit be- other early Pliocene and Pleistocene remains referable to mon- longs to the Mogarts Beach Member (Dowsett and Wiggs, 1992), odontids are known from the east coast of North America and based on the dominant presence of the planktic foraminiferans the North Sea Basin (Whitmore, 1970, 1994; Post, 2005; Lambert Globigerina bulloides and Neogloboquadrina acostaensis.Also, and Gigase, 2007; Whitmore and Kaltenbach, 2008). Some of the Hazel (1971) placed Rice’s Pit in the Orionia vaughani Zone, remains from the North Sea Basin consist of cranial material that based on that ostracode’s presence at the locality. Dowsett and shares some similarities with Delphinapterus, although they are Wiggs (1992) reported an age estimate of 4.0–3.0 Ma, a range that too incompletely preserved for identification below the family largely concurred with Cronin et al. (1984)’s placement of York- level (Lambert and Gigase, 2007). Reported fossils from the east town Formation localities from southeastern Virginia in standard coast of North America have been collected from the Yorktown planktic foraminifer zones N19–21 and Blackwelder (1981)’s M5 Formation in North Carolina and Virginia; the most notable of molluscan zone for the Morgarts Beach Member of the Yorktown Formation. Collectively, these biostratigraphic indicators point to *Corresponding author. Piacenzian age for this new monodontid. 476 VELEZ-JUARBE´ AND PYENSON—-NEW PLIOCENE MONODONTID 477 Institutional Abbreviations—IRSNB, Institut royal des Sci- TABLE 1. Measurements of holotype skull (USNM 25819) of ences naturelles de Belgique, Brussels, Belgium; M,Fossilmam- Bohaskaia monodontoides, gen. nov., sp. nov., in mm (after Perrin, 1975). mal collection of types and figured specimens of the IRSNB; UCMP, Museum of Paleontology, University of California, Berkeley, California, U.S.A.; UCR, Department of Geological Length of rostrum—from tip to line across hindmost limits of 259 antorbital notches Sciences at the University of California, Riverside, California, Width of rostrum at base—along line across hindmost limits 216 e U.S.A.; USNM, Department of Paleobiology and Department of antorbital notches Vertebrate Zoology (Division of Mammals), National Museum Width of rostrum at 60 mm anterior to line across hindmost 151+ of Natural History, Smithsonian Institution, Washington, D.C., limits of antorbital notches U.S.A. Width of rostrum at midlength 138 Specimens Observed—Delphinapterus leucas (USNM A21051, Width of premaxillae at midlength of rostrum 82 Width of rostrum at 3 length, measured from posterior end 112 A21052, A22433, A23208, 238105, 275068, 572014); Monodon 4 Distance from tip of rostrum to external nares (to mesial end 381 monoceros (USNM A22983, A23455, A267957–267961). of anterior transverse margin of right naris) Greatest width of external nares 72 Greatest width of premaxillae 121 SYSTEMATIC PALEONTOLOGY Projection of premaxillae beyond maxillae measured from tip 15 of rostrum to line across foremost tips of maxillaries visible CETACEA Brisson, 1762 in dorsal view ODONTOCETI Flower, 1867 Distance from foremost end of junction between nasals to 50 DELPHINOIDEA Gray, 1821 hindmost point of margin of supraoccipital crest Length of upper left tooth row—from hindmost margin of 154 MONODONTIDAE Gray, 1821 hindmost alveolus to tip of rostrum BOHASKAIA, gen. nov. Number of teeth—upper left 12 Number of teeth—upper right 11 Type and Only Known Species—Bohaskaia monodontoides, sp. nov. + Diagnosis—Same as that of the species. Abbreviations: e, estimate; , measurement on incomplete element. Etymology—Honors David J. Bohaska, in recognition of his extensive contributions to understanding