IntroductionWeseldomfindevidenceofdirect interactionofanimals inthefossil record. But a few years agowe discovered a beautifullypreserved skull of the saber-toothed cat-like nimravid Dinictis(NDGScatalognumber59)withtooth-puncturemarks,indicatingthat it had been killed by another animal. This unusual fossilwas foundweathering out of the Oligocene (about 32million-year-old)BruleFormationatafossilsitethatwerefertoastheFitterer Ranch locality near Dickinson in Stark County (NDGSlocalitynumberL21).Thisdiscoverywasmadeduringstudiestolearnmore about the kinds of plants and animals that lived inwesternNorthDakotaduringthattime(HogansonandLammers,1992;Murphyetal.1993;Hogansonetal.1998).Over60speciesofmammalswere identified from fossils collectedduring thosestudies. Most of these animals were herbivores that roamedamostly treelessplain ina temperateclimate. The remainsofsome carnivores, although uncommon, were found, includingthe skull of Dinictis. Detailed preparation of the Dinictis skull

revealed well preserved puncture marks which prompted ourquesttodeterminethekindofanimalthatputthisDinictistorest(HogansonandPerson,2010).

TheFittererRanchlocalitywasapparentlyfirstdiscoveredbyanAmericanMuseumofNaturalHistoryFrickLaboratoryexpeditiontoNorthDakotaledbyMorrisSkinner(fig.1).SkinnercollectedBrule fossils from the Fitterer Ranch locality and other sites inNorthDakotafrom1944to1964.HedidnotdescribetheNorthDakotaBrulefossilsandapparentlydidnotcollectDinictis fromFitterer Ranch. Hoganson and Lammers (1992) were first toreportDinictis fromFittererRanchbasedontheskullspecimendescribedhere,buttheydidnotidentifythespecimentospecies.Murphy et al. (1993) and Hoganson et al. (1998) also did notidentifythisspecimentospecies. HogansonandPerson(2010)confidentlyassignedthisspecimentoDinictisfelinaLeidy,1854.

StratigraphyA complete section of the BruleFormationisexposedattheFittererRanchlocality(Murphyetal.,1993;Hoganson et al., 1998) (figs. 2 and3). The Fitterer Ranch locality isregisteredasaNorthDakotaNaturalArea because it is an importantgeological and paleontologicalsite. The lower part of the BruleFormation consists of pinkish-brown to gray-green complexlyinterbeddedclaystones,mudstones,siltstones, freshwater limestones,tuffaceous beds, and crossbeddedchannel sandstones. The channelsandstones, such as the “FittererBed” are difficult to trace for longdistances and usually containdisarticulated mammalian remains.A useful tuffaceous marker bed inthe lower Brule was termed theAntelope Creek tuff by Murphy etal.(1993)(fig.4).TheupperpartoftheBruleFormationat theFittererRanch locality is less variable andconsists primarily of alternating

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Tooth puncture marks on a 30 million year old Dinictis skull

John W. Hoganson and Jeff J. Person

Figure1.GeneralizedgeologicmapofNorthDakota.RedstarindicateslocationofFittererRanchlocality(NDGSL21).

JULY 2011 13

siltstones,mudstones,andclaystonesthatareledgeforming.TheBruleFormationisabout213ft(65m)thickatthislocality.

AttheFittererRanchlocality,theBruleFormationisunconformablyunderlainbythegrey-greenclaystoneoftheSouthHeartMemberoftheEoceneChadronFormationandunconformablyoverlainbyaconglomeraticsandstoneoftheArikareeFormation.

BiochronologySkinner (1951)wasfirst to suggest that at least the lower partoftheBruleFormationinNorthDakotawasOrellaninage.ThiswasconfirmedbyHogansonandLammers(1992),Murphyetal.(1993),andHogansonetal.(1998),mostlybasedonfossilsfromtheFittererRanchlocality. Mammalianfossilsaresparse intheupper part of the Brule Formation but a possible Whitneyanage is suggested by meager evidence (Hoganson et al., 1998).Magnetostratigraphic interpretation appears to corroborate anOrellanageforthelowerBruleandaWhitneyanagefortheupperBruleinNorthDakota(Protheroetal.,1983).

TheDinictis felina skull under consideration herewas found inaBruleFormationclayeysiltstone18.2 feet (5.55m)abovetheSouthHeartMemberoftheChadronFormationand10.3feet(3.15m)belowtheAntelopeCreektuff.FossilsfoundwiththeDinictisskull,includingthehorseMesohippusbairdi(fig.5)andtherabbitPalaeolagusburkei(fig.6)indicatealatestOrellan(Or4)intervalzone,thatis,32.5to32.0millionyearsago(table1).Theremains

Figure2.PhotoofAntelopeCreektuff(arrow)nearthelocationwheretheDinictisfelinaskullwasfoundattheFittererRanchlocality.JeffPersonrecordingfossilsfromDinictisfelinasite(left).BeckyGouldpointingtoAntelopeCreektuff(right).

Figure3.StratigraphicsectionattheFittererRanchlocality.

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of other animals were alsofound with Dinictis includingthe tortoise Stylemys, thedogHesperocyon gregarious,the deer Leptomeryx evansi,themice Eumys elegans andParadjiduamo?, land snails,and seeds from the maidenhairtreeCeltis.

DiscussionThree distinct and well-defined tooth puncturemarks are present on theright temporal and parietalbones of this Dinictis felinaskull(fig.7).Anotherpossiblebite mark occurs on the leftparietal, although this markis less obvious because ofmissing and fractured bone.Two tooth scratchmarks arepresent on the left maxilla,near the orbit and suturewiththefrontal.Therearenoindications of healing around

Figure4. NDGSpaleontologist BeckyGould removingMesohippus bairdi partial skeleton fromDinictis site.ArrowshowinglocationofAntelopeCreektuff.

NDGS L21 Mammalian Biostratigraphy

Or4

Wh1

Wh2

Ar1

Ar2

Ar3

Ar4

Or3

Or2

Or1

Ch4

Ch3

Ch2

Ch1

Du1

Ui3

Ui2

Ui1

Eocene

Oligocene

Miocene

Table1.AgeoftheDinictis felinasiteattheFittererRanchlocality(NDGSL21).Thischartshowsthebiostratigraphicrangesofknownmammaliantaxafromthesiteandmammalintervals.Linesarerangesofgeneraandboxesarerangesofspecies.Theredboxillustratesthesub-agewherespeciescoexistandisthereforetheinterpretedageofthesite.

JULY 2011 15

thetoothpuncturemarks.Alsotheleftzygomaticarchisbrokenanddistorted.Webelievethetoothpuncturemarks,scratches,and broken zygomatic arch reflect an act of predation becauseit is likely that a scavengerwould have concentrated on fleshyareasofthecarcass,nottheskull.Thereisnoindicationthatthepunctureswerehealing,suggestingthattheblowtotheskullwasfatal.

Theposteriorbitemarkisontherightparietalnearthesagittalcrest and occipital. This mark is longer than it is wide and isperpendiculartotheothertwomarksvisibleonthissideoftheskull.Itis0.55inches(14.0mm)long(anterior/posterior)and0.3inches(7.3mm)wide(labial/lingual).Unliketheothertwomarks,thismarkis“sunken”producingadepressioninthebone,butthebonewasnotpierced.Theventralportionofthemark has a small asymmetrical concavity givingthe mark the shape of a footprint suggestingmultiplebites, slippingof thepenetrating toothorshakingoftheskull.

The middle bite mark is located on the rightparietal and is the largest of the three. Thispunctureis0.4inches(10.0mm)long(anterior/posterior)and0.6inches(15.9mm)wide(labial/lingual).Therearesmallpiecesofcrushedbonealongtheanteriorandventraledgesofthemarkwhich are broken concentrically, otherwise thepunctureisoval.

Theanteriorbitemark is locatednear the rightparietal/temporal suture and is the smallestof the threemarks. Thepuncture is 0.4 inches(10.0 mm) long (anterior/posterior) and 0.5inches (13.5mm)wide (labial/lingual). There isasmallpieceofcrushedbonealongtheventraledgeofthemarkwhichisbrokenconcentrically,otherwisethepunctureisoval.

Todetermine theanimal thatcaused thesebitemarks,wecomparedthepuncturemarksonourspecimen to others reported in the literature,to a skull of Nimravus also exhibiting a cranialpuncture in the collection of the South Dakota

SchoolofMines&Technology,andbycomparingthemorphologyandgeometryofthepuncturesonourskulltoteethofpotentialBruleFormationpredators.Animalsthatweconsideredpotentialpredator candidates were crocodilian, Dinictis, Hoplophoneus,Archaeotherium,Daphoenus,andHyaenodon,allofwhichhavebeenreportedfromtheBruleFormation inStarkCounty,NorthDakota.

Crocodilians have the capacity to inflict damage such as this.However, since they are ambush predators from water it isunlikely that a crocodilianwouldproducebiteson the topof askull.Inaddition,thepuncturesontheDinictisskullarelaterallycompressedwhereascrocodilianteetharemoreconical.Itisalsounlikely that Dinictis or Hoplophoneus produced the puncture

Figure7.ViewofbitemarksonrightparietalofNDGS59.Barsshowdistancebetweenbitemarks.Noteonemarkwouldhavebeenlocatedinsideorbitandwouldnothavepenetratedbone.

Figure5.PhotoofMesohippus bairdi skeleton.Length20inches(51cm)Thisspecimenisasub-adult,butadultscouldreach2ft.(60cm)tallattheshoulder,andupto4ft.(1.2m)long.

Figure6. PhotoofPalaeolagus burkei skull. Length2 inches(51mm)Theserabbitsprobablylookedsimilarinappearancetomodernrabbitsandgrewtolengthsof10inches(25cm).

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marksbecausetheiruppercaninesaretoolaterallycompressedcompared to the oval shape of the punctures. Their uppercanineswerealsoprobablytoofragiletobeabletopenetratetheskull.Theirlowercaninesweretoosmalltocreatethepunctures.The upper and lower canines ofDaphoenus are also too smalltohavecausedthepunctures. TheupperandlowercaninesofArchaeotheriumaretoolargetohavecausedthepuncturesandthespacingbetweenthecaninesisalsomuchtoowidecomparedtospacingbetweenthepunctures.

We suggest that Hyaenodon killed this Dinictis because thegeometryofthetoothpuncturesissimilartotheslightlylabially/linguallycompressedshapeoftheuppercaninesofHyaenodon(fig.8).Also,thedistancebetweenpuncturesisconsistentwiththe spacing between the upper canines ofHyaenodon. This isparticularly true ifmultiplebitesoccurred, aswe suggest. Thepunctureswere notmade by the lower canines ofHyaenodonbecausetheyaresplayedout labiallyandwouldhaveproduceda different shaped puncture. Both Hyaenodon horridus andHyaenodon crucians have been recovered from the BruleFormation in North Dakota, but because the range of spacingbetween the upper canines (table 2) is more consistent withHyaenodon horridus, we suggest that H. horridus is the morelikelypredator.

ConclusionWeenvisionthatHyaenodonhorridusattackedthisDinictisfelinafromtherearon its leftside(figs.9and10). ItdispatchedtheDinictis bymultiple bites to the skull. After at least two bites,its upper front canines created two incipient bite marks on

the parietal near the sagittal crest and two crushing and deeppenetratingpunctureson the rightparietal. During theattack,thelowerjawofHyaenodoncrushedtheleftzygomaticarchandits lower premolars created scratches on the left maxilla andanotherbitemarkontheleftparietal.

Dinictis therockstarOurNorthDakotaDinictis specimenbecamepartof aNationalGeographictelevisiondocumentary.ThedocumentarywaspartofNational Geographic’s Prehistoric Predators series that airedduring the fall of 2009 on the National Geographic channel.This episodewas aboutHyaenodon, called “Razor Jaws” in thedocumentary, in referenceto itssharp,flesh-tearingteeth. WearefilmedmakingskullandtoothmeasurementsofDinictisandHyaenodon,anddiscusshowwedeterminedthatHyaenodonwasthepredatorthatkilledDinictis.

AcknowledgementsWewouldliketothankthefollowingfortheircontributionstotheproject.TheFittererfamily,Dr.JamesMartin,Ms.SallyShelton,Ms. Becky Gould, and the South Dakota School of Mines andTechnology.

Figure8.PhotoofHyaenodonskull.Length10inches(25cm)

Figure9.AuthorsinterpretationofhowbitemarkswereproducedontheskullofDinictis felina (white)by Hyaenodon horridus (tan).IllustrationbyBeckyGould.

Table2.Measurementsofvariousskullsstudied.

JULY 2011 17

ReferencesCitedHoganson, J.W., and Gould, B., 2011, Prehistoric life of North

Dakota coloring and activity book: North DakotaGeologicalSurveyEducationalSeries32.

Hoganson, J.W., and Lammers. G.E., 1992, Vertebrate fossilrecord,ageanddepositionalenvironmentsoftheBruleFormation(Oligocene)inNorthDakota,inErickson,J.M.,andHoganson,J.W.eds.,FrankD.Holland,Jr.,Symposium:NorthDakotaGeologicalSurveyMiscellaneousSeries76,p.243-257.

Hoganson,J.W.,andPerson,J.J.,2010,ToothpuncturemarksonaskullofDinictis(Nimravidae)fromtheOligoceneBruleFormation of North Dakota attributed to predation byHyaenodon (Hyaenodontidae): Society of VertebratePaleontologyProgramandAbstracts,p.106A.

Hoganson, J.W., Murphy, E.C., and Forsman, N.F., 1998,Lithostratigraphy, paleontology, and biochronology ofthe Chadron, Brule, and Arikaree Formations in NorthDakota,inTerry,D.O.,Jr.,LaGarry,H.E.,andHunt,R.M.,Jr. eds., Depositional environments, lithostratigraphy,and biostratigraphy of the White River and ArikareeGroups(LateEocenetoEarlyMiocene,NorthAmerica):

Boulder,Colorado,GeologicalSocietyofAmericaSpecialPaper325,p.185-196.

Murphy, E.C., Hoganson, J.W., and Forsman, N.F., 1993, TheChadron, Brule, and Arikaree Formations in NorthDakota: North Dakota Geological Survey Report ofInvestigation96,144p.

Prothero, D.R., Denham, C.R., and Farmer, H.G., 1983,Magnetostratigraphy of the White River Groupand its implications for Oligocene geochronology:Palaeogeography, Palaeoclimatology, Palaeoecology, v.42,p.151-166.

Skinner,M.F.,1951,TheOligoceneofwesternNorthDakota, inBump,J.D.,ed.,Guidebook,5thAnnualFieldConference,western South Dakota, August-September 1951: RapidCity,SocietyofVertebratePaleontology.

Figure10.ColoredsceneofDinictis(middle)andHyaenodon(right)fightingoverthecarcassofMerycoidodon(left)(HogansonandGould,2011).