Jeffersoniana 29

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The first terrestrial mammal from the Late Miocene Eastover Formation of Virginia
  ISSN 1061-1878 (print)ISSN 2163-8020 (online)  JEFFERSONIANA Contributions from theVirginia Museum of Natural History  Number 294 March 2013 The rst terrestrial mammal from the Late MioceneEastover Formation of Virginia Brian Lee Beatty and Alton C. Dooley, Jr.  Virginia Museum of Natural HistoryScientic Publications SeriesThe Virginia Museum of Natural History produces ve scientic publication series, with each issue published as suitable material becomes available and each numbered consecutively within its series. Topicsconsist of srcinal research conducted by museum staff or afliated investigators based on the museum’scollections or on subjects relevant to the museum’s areas of interest. All are distributed to other museumsand libraries through our exchange program and are available for purchase by individual consumers.Memoirs are typically larger productions: individual monographs on a single subject such as a regionalsurvey or comprehensive treatment of an entire group.  Jeffersoniana is an outlet for relatively short studies treating a single subject, facilitating expeditious publication.Guidebooks are publications, often semi-popular, designed to assist readers on a particular subject in a particular region. They may be produced to accompany members of an excursion, or may serve as a eldguide for a specic geographic area.Special Publications consist of unique contributions, usually book length, either single-subject or the proceedings of a symposium or multi-disciplinary project in which the papers reect a common theme. The Insects of Virginia is a series of bulletins emphasizing identication, distribution, and biology of individual taxa (usually a family) of insects as represented in the Virginia fauna. Originally produced atVPI & SU, the series was adopted by VMNH in 1993.Copyright 2013 by the Virginia Museum of Natural HistoryPrinted in the United States of America ISSN 1061-1878 (print)ISSN 2163-8020 (online)  Jeffersoniana, Number 29 pp. 1–6Virginia Museum of Natural History The rst terrestrial mammal from the Late MioceneEastover Formation of Virginia B rian L ee B eatty 1   and a Lton C. d ooLey , J r  . 2 ABSTRACT A partial deciduous premolar from a gomphothere is reported from the Late Miocene Eastover Formationin New Kent County, Virginia. This represents the rst denitive occurrence of a terrestrial mammal fromthe Eastover Formation.Gomphotheres are now known from nearly every marine formation from the Middle Miocene to theEarly Pliocene along the middle Atlantic Coastal Plain. Gomphotheres are typically associated with moreopen habitats, but oral data suggests that the region transitioned from warmer, more forested conditionsin the Middle Miocene to heterogeneous conditions in the Late Miocene. The persistence of gomphotheresthroughout this interval suggests that substantial open habitats were present along the Coastal Plain fromthe Middle Miocene to at least the Early Pliocene. 1 NYIT College of Osteopathic Medicine, Old Westbury, New York, USA. bbeatty@nyit.edu2 Virginia Museum of Natural History, Martinsville, Virginia, USA. INTRODUCTION Tertiary terrestrial mammal faunas are extremelysparse in northeastern North America, with onlya few key faunas available from the Miocene andPliocene that can illuminate anything about theregion’s fauna and environment before and after the dramatic environmental changes associatedwith the development of the East Antarctic IceSheet in the Middle Miocene, between 18-6.5 Ma(Flower and Kennett 1994). This limitation restricts paleoecological studies that require large samplesizes to comparisons of Florida faunas to those of the Great Plains and western faunas (Beatty andMihlbachler 2011), even though this makes it hardto isolate the effects of latitude from proximity tocoastal inuences on climate.Fossil sites bearing terrestrial mammals alongthe Atlantic margin are particularly good for makingmarine and non-marine correlations when localitiescan be linked temporally by diatom, foraminifera,or mollusk-based dating schemes. Much has beendone to establish such relationships for Earlyand Middle Miocene sediments of the Atlanticcoast, particularly that of Virginia, Maryland, theCarolinas, and Florida (Tedford and Hunter 1984).Late Miocene and Pliocene faunas are similarlyrare, but have had less benet from well-establishedregional collecting like the predominantly MiddleMiocene and Early Pliocene exposures found atthe Calvert Cliffs or Lee Creek Mine. Terrestrialmammals mentioned by Geisler et al. (2012) ascoming from the Late Miocene Eastover Formationfrom Gravatts Millpond in Virginia were in factrecovered from the upper part of the MiddleMiocene Calvert Formation according to Whitmore(1984).The Eastover Formation is an unconsolidatedmarine sand to clay located on the Middle AtlanticCoastal Plain. The unit has been identied at least asfar north as the Virginia side of the Potomac River (Ward 2005) and perhaps into southern Maryland(Ward and Blackwelder 1980), and to the southalong the Trent and Neuse Rivers in North Carolina(Ward 2008a; Ward and Blackwelder 1980). It isthin to the south, and in some areas is absent (for   J effersoniana 2 example, at Lee Creek Mine) (Ward 2008a). Twomembers have been identied in the Eastover, theolder Claremont Manor Member and the overlyingCobham Bay Member (Ward and Blackwelder 1980).Ward and Blackwelder (1980) reportedthe Eastover age as Late Miocene, based on aglauconite dates of 8.7±0.4 Ma and 6.46±0.15 Mafrom the Cobham Bay Member, and a glauconitedate of 12.0±0.5 Ma from the underlying St. MarysFormation. Ward (1992) placed the Cobham BayMember in Molluscan Interval Zone M-7, andcorrelates this with Planktonic ForaminiferalZone N17 (Blow 1969), which ranges fromapproximately 5.4-7.1 Ma (Berggren et al. 1985).The Claremont Manor Member is placed by Ward(1992) in Molluscan Interval Zone M-8, which hecorrelates with Planktonic Foraminiferal Zone N16(Blow 1969), which ranges from approximately7.1-10.2 Ma (Berggren et al. 1985).The Late Miocene is a key period in the transitionfrom the faunas associated with the warm climateof the early Neogene and the cooling environmentof the Plio-Pleistocene. This is a time during whichgrasslands that srcinated earlier in the Miocene(Strömberg 2005) were spreading across NorthAmerica and causing faunas of the Great Plains toshift from being dominated by browsers to grazers(Janis et al. 2004; Mihlbachler et al. 2011). Fossil- bearing Late Miocene strata in the Mid-Atlantic or  Northeast of North America are rare, making anyinformation available about terrestrial vertebratefaunas during this period precious. Here we reportthe rst specimen of a terrestrial mammal from theLate Miocene of Virginia.Abbreviations: FLMNH, Florida Museum of  Natural History, Gainesville, Florida; VMNH,Virginia Museum of Natural History, Martinsville,Virginia. SYSTEMATIC PALEONTOLOGY Order PROBOSCIDEA Illiger  1811 Family GOMPHOTHERIIDAE Hay 1922Genus INDETERMINATEReferrred specimen: VMNH 120092, a partiallower deciduous premolar. Collected by RoseSchooff and Christie Aldridge-Nunn from theSchooff Property, New Kent County, Virginia.Stratigraphic horizon and age: Eastover Formation, Cobham Bay Member. Late Miocene.The specimen was collected in situ in a shell bedthat included the bivalve  Isognomen sp., andimmediately below a bed that included the bivalve Chesapecten jeffersonius .  Isognomen sp. goeslocally extinct at the top of the Eastover Formation,while C. jeffersonius is restricted to the SunkenMeadow Member of the Yorktown Formation(Ward 1992).VMNH 120092 (Fig. 1) is a partial upper left deciduous premolar (most likely DP4) of agomphothere. Gomphothere dentitions can bediscerned from mammutids by having tetralophodontM3s (Lambert and Shoshani 1998). Unfortunately,this tooth is a partial upper premolar, and isdiagnosed from mammutids primarily because ithas trefoils present only on the pretrite half of cheek teeth (single trefoiling), unlike mammutids thathave trefoils on both posttrite and pretrite halves of upper molars (Lambert and Shoshani 1998).Gomphotheres have been known from the PlumPoint Member of the Calvert Formation (14-16 Ma)for over a hundred years (Case 1904; Gazin andCollins 1950). The Cobham Bay Member of theEastover Formation is a Late Miocene marine unit,approximately 6.5-9 million years old, and this newspecimen comes from New Kent County, Virginia,from the top of the unit, making it the youngestoccurrence of gomphotheres on the east coast northof the Carolinas. Occurrences of gomphotheres thatare as young or younger are rare in the southeasternUnited States, including the Late Miocene toEarly Pliocene (4.5-7 Ma) occurrence at the GrayFossil Site in Tennessee (Wallace and Wang 2004;
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