Getman, Myron. 1994. Occurances of Mosasaur Remains from the Fox Hills Formation (Maastrichtian:...

8/7/2019 Getman, Myron. 1994. Occurances of Mosasaur Remains from the Fox Hills Formation (Maastrichtian: Late Cretace

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OCCURRENCES OF MOSASAREMAINS FROM THE FOX

MAASTRICHTIAN: LATE CRETACEOUS! OF NORTH DAKOTA

By Myron R.C. Getman

A Bachelors Thesis submitted to the Facultyof the Department of Geology of

St. Lawrence University

In partial fulfillment of the requirements forthe degree of

Bachelor of Science with Honors in Geology

Canton, N.Y.1994


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This thesis submitted byin partial fulfillment of the require

Bachelor of Scienc

Lawrence Universitapproved by the facultyadvisor under who

te


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pageTitle Page

ApprovalTable of Contents

List of Pigures'ist of Abbreviations

AcknowledgmentsAbstractIntroducti.onMethods

1V

V11V111

Previous Works

Ages and Locat onsStratigraphic DescriptionsSystematic PaleontologySummaryReferences

1820

3359

61

TABLE OF CONTENTS


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nr' T ov Frcunmspa25Stratigraphic Column of Site A1050

2. Strati graphi c Correlation ofSites I, 2,and 31050

."igure 3. Stratigraphic Column showing IronLightning/Fox Hills contact Carpenter et al. 1988! 32

Figure 4.Mosasaurus dekayi,buccal side and base oftooth 35

Frgure 5. Mosasaurusdekayi,lingual side and tzp of36tooth

Frgure 6. Mosasauzusdekayi,side views of toothshowrng longitudinal carznae 37

Figure 7. Mosasaurusdekayi,illustration of known38specrmen Russell, 199gj

Figure 8.Plaoplatecarpus sp., buccal sade and top oftooth

Figure 9.Plaoplatecarpus sp., lingual side and base oftooth

Figure 10.Pli oplatecarpus sp., side views of tooth

showing very faint longitudinal carrnaeFigure 11. Mosasaur vertebra

F gure 12. Mosasaur vertebraFigure 13. Iaedyosuchus sp., side vzew anti base of

tooth

Fzgure 14, Iaedyosuchus sp., anterror vrew a..d tip oftooth

V


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:.. g" e 15.Fig.re 16.Figure 17.Figure 18.Frgure 19.5355

58


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LIST OF ABBREVIATIONS

.Kansas StateKS...North Dakota Geological SurveyNDGS.

St. Lawrence UniversitySLU.


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ACKNOWLEDGMENTS

aid o the following people, this

:basis would not be possible: Dr. J. Markhis rmmeasurable patience, knowledge, andonal drive; Dr. John Hoganson for

finding most of the material used in thefcr '. s enthusiasm, respect and ability to

s rings"; Peter Connett for being a constantcos.panion anc partner during the field -session, forbeing patient, open minded, and being able to toleratemv oddities; Dean Schwartz and the Office of AcademicAffairs for giving Peter and I the arants we needed to

complete our work and for being patient; Dr. F.D. "Bud"Holland Jr. for heine a well sprinc of knowledge andconsiderable aid in the field; Ray are Kathy Haas for

allowing Peter and 1 to stay at their home and forgiving us much needed breaks from orr work birding andthe Laird outcrop!; rhe Rotary Club of Glens Falls, NYwithout whom most of my educational a..d thesis-relatedfinancial needs would never have beer met, my family who

have supported me throughout this experier ce, and thecountless others who have helped in ays ti ey may notrealize.


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Occurrences of Mosasaur and Other Reptilian fossilremains from the Fox Hills Formation

Maastrichtian: Late Cretaceous! of North DakotaMyron R.C. Hetman

ABSTRACT

In an attempt to add to the undezstancii..g of thevertebrate biota of the Fox Halls Fozma ion of rhe Upper

Cretaceous !Maastrichtian! of North Dako a, three teeth anda dermal scute recovered from the Timbe Lake/Iron Lightningboundary of the Fox Hills Formation by R.M. Feldmann nearLinton, Emmons County were identified. Basec on morphology,the larger of the two has been identified a Mosasaurusdekayi Bronn 1838. The smoother tooth exhibits the conzcal,

nearly circular horizontal cross-sectio c .aracteristicsassociated with crocodilian teeth. The smallest of the

teeth actually a tooth fragment! has been identified asbelonging to some type of Tyrannosaurid. The dermal scutehas been identified as belonging to the terrestrial turtleBaszlemys sp.

A small tooth, a metacarpal and a verteoza werezdentified. The tooth has been identified as belonging to

Plioplatecazpus sp. and the metacarpal be'ongs to anunidentified reptile. The vertebra has been identzfied asbelongzng to a mosasaur.


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ddrtron, field work was performed during 1993. A=-'te '." : a Timber Lake Member of the Fox Hills Formation

' as '= := ' in Bowman County, North Dakota whrch, afterexo'cr=- ","*, excavation and considerable sievrng producedma erial and, based on a broken metacarpal, is

thought to possibly belong to some type of turtle. The bone

belongs o two drstinct types, a compact "structural" type,thought to be rib material, and a thinner, more porous typebelieved to be a portion of the skull. During the fieldsessron, a bone was also discovered within a concretion inEmmons County. After cleaning and inspection, this bone hasbeen identified as a mosasaur vertebra.

The discovery of these vertebrate fossils aids in theunderstandrng of the little studied Fox Hills reptilianfaunas. All the fossils, with the exception ofBasi lemys

sp. arepreviously known in the Fox Hills Formatron.Basilemys sp. is known from the Fox Hills of South Dakotabut not from North Dakota. An unrdentified mosasaur tooth

was repo ted by A.G. Leonard in the 1912 Hnited StatesGeological Survey Bismark F'olio. At this time, the locationof the tooth is unknown.

The presence of Mosasaurus dekayi in the Fox Hillsrepresents a stratiaraphic and geographic range extension.ThePli oplatecarpus sp., because its species is uncertainmay epresent a stratrgraphic range exten io from theCampanran age Frerre Shale of South Dakota. cr a geographicexent o.. From the Maastrichtian of New ersey. Two


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r..ma-e mosasaur vertebrae lend credrbrlity to the.osasaurs in the Fox Hrlls sediments. The

. ;..c =-"" tooth fragment represents a stratigraphic range.".== ase from the overlaying Hell Creek. Further

=-= chary reptilian fossil remains provide furtherofferee of vertebrate faunas in the Fox Hills Formation.


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INTRODUCTION

rs known about the reptilran fossils which arethe stratigraphy of the Fox Hills Formation.

sert of creatures might be found contained within thiswhich is transitional between the marine sediments

the Pierre Shale with its mosasaurs and other marine

eptrles and the terrestrial deposits of the Hell CreekFormation and its dinosaurs'? Could there have been

rosasaurs exploiting the deltaic, barrier island, and other

regresszve environments that the Fox Hills FormationErickson, 1992! represents? Could they have been swimming

in the shallow waters feeding on ammonites, fish or, likekiller whales and sharks today, chasing larger prey onto thebeach to be devoured. These creatures and their marine

brethren were highly adapted, undoubtedly capable of amazing

hunting abilities. Could there have been tyrannosaurshunting on the terrestrral portion of the delta? There isno reason to believe both these creatures and theirassociated faunas were not in the deltaic environment of the

Fox Hills Formation. Previously, little of their remainshave been found. Perhaps the envrronment, which would havebeen rich wrth brologrcal activrty, of the Fox Hills was notconducive for the creation of fossils or perhaps, peoplenave not been lookrng or wrlling to take the rime to look inthe rroht places. As a result, the vertebrate faunas of theFox Hrll Fcrma ron have not been studiec as closely asthose r. .he Prer e Shale and Hell Creek Formatrons.


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there is now evidence of their, and other,nas, existing in the paleoenvrronments

by t' e Timber Lake Member of the Fox Hills

: as my rntent to aid in the study of vertebratefa"nas ": the Fox Hills Formation when Peter Connett and I;ear our to North Dakota in July, 1993. My goal was to aid

he collection of fossil fish and shark teeth for Drs.Hoga. son and Mark Erickson and to look for a potential

o" basis project. Fortunately, a location with bone onthe surface was found by Mr. Ray Haas, an expedition member,on he first day of tooth collection near Bowman, NorthDakota. This sate was placed stratigraphically within theTimber Lake Member of the Fox Hills Formation. It was later

excavated and more bone was recovered. Shortly afterwards,

a bone whrch was contained within a concretion was found byMark Erickson. This bone, since recognized as a mosasaurvertebra, was also from the Fox Hills Formation. Dr.Erickson later added another mosasaur vertebra, which had

also been contarned within a Disiniopsis pod, that had beenrecovered during a previous field session.

After beginning the Fall 1993 semester, and in theprocess of sieving for my Senior Thesis, rwo teeth were sentto me by Dr. John Hoganson in the hopes I might be able toidentify then' and ncorporate them into the theses. Theyhad alee bee reccvered from the Fox Hills Fo mation by R.M.Feldmannn ar - s re .,ear Lrntorw North ajora where he had


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ty annosaurrd tootn and ate, also recovered by :eldmann, were

,:= pt o. and illustration. During the springse-eater .-";'= =- on a trip to meet Dr. Gorden BellJr.,

Boganson niscovered a tiny,reptilian tooth and a

metacarpal in the Timber Lake approximately onefrom the excavation site. These were also sent for

snnsecp ent desc iption, illustration, and possible'on


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METHODS

The Ho man site T. 130 N, R. 106 W, Sec. 24! wasthoro:ghlv surface collected. It was orrgir ally intended tosuzface collect and then dry sieve the rema ning surfacenaterral before the hill which the bone was zound on was cut

into for the excavation. Unfortunately, inclement weatherprevented this ideal situation. Due to the constant rainsand the hrgh clay content of the suzface material, it wouldhave to be wet-sieved. Unfortunately, neirher the time northe equipment were available for this ur.derraking in thefield. The entire surface of the hill was scrapped, baggedand shipped to the St. Lawrence Geology Department where itwould later be wet-sieved properly. The excavatron was thenundertaken. Despite removing many cubic meters of sediment

centimeter by centimeter with trowel and trenching tool, noadditional material was recovered.

The materral which had been shipped to St.. Lawrence waswet sieved. It was quickly learned tnat th considerableclay content prevented proper wet sieving. As a result, thematerral was wasl'ed before sieving witt warm water and asmall amount of Calgon. After sieving, rhe debris wastirvrded into two portions, a finer green srze 2 3 mm! which wouldcontain preces of bone f om the sate. After drying, the


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was packed through to find any preces of

=:fter all the shipped material had been wet sreved and

eked through, the bone was examined for any matches wrthotner pieces of bone. If any matches were found, the pieceswere carefully glued together. The bone material was thenexamined.

The bone contained within the concretion found was

carefully cracked free from its confinement. Unfortunately,

some material was lost from the bone as a result of thecracking of the very hard concretion. Next, excessconcretronary material was cut away with the use of a dremeltool and a dramond blade. The bone was then examined.

Fortunately, the teeth, scute, and metacarpal requiredno cleaning or preparationor where already prepared. They

were carefuliy examrned for any distinguishing featureswhich may be used for their proper identification. Thisprocess was greatly aided by drawing illustrations andcareful measurement.


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PREVIOUS WORKS

The Mosasauridae were an interesting Family ofscca. ory marine lizards which exzsted du i c the

Cretaceous. Mosasrapid evolution, "...tsucceeded zn estayears, as tCretaceoucontemporS li 199


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Ti.e story about the first discovery of a mosasaur is avery fr terestingone. In1780, 42 vears before theciscove y of the first dinosaur fossil, the first mosasaurfos 11 was found by quarrymen, in Cretaceous rocks, 90 feetbe w St. Peters Mount in Maastricht, Holla. d Russell,

1967!. Dr. Hoffman, a surgeon who lived in Maastricht,examined the skull and vertebral column and also directedthe excavation Russell, 196'7!. The first complication inthe Maastricht mosasaur's story occu red when a clergyman

.=-. ec Goddin, whose land the fossil had been found on,clair:,ed the fossil as his own rather than allow it to beexamined and described by Hoffman Russell, 1967!. Due toits unique character, the fossil soon attracted a degree offame. Nnen the French laid si.ege on Maasnr'cht in 1795, thecommanding officer of the French Republicordered that the

artillery avoid Goddin's house obviously to avoid damagingthe fossil and so that it could be taken back with them to

France Russell, 1967!. Goddin anticipated the Frenchinterest in the fossil and hid it in the town Russell,

1967!. Despite Goddin's best attempts at hiding themosasaur, it was found and sent to Pa~is where it stillresides in the Museum National d'Histoire Naturelle

Russell, 1967!. In 1808, Cuvier reexamined the fossil anddecided it was related to the varanid lizards Russell,

1967!. Other experts of the period haci dizferent ideasabout tl.e oss ' origin. Pierre Camp r and Van Harumthought ihe Maastrich mosasaur wa cerace n, Faujas Saint


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was - crocodrle, and Adrien Camper sharedrha- ir. was a lizard. It would be ten year

818! reexaminatron of the Maastrrchtrhe frrst mosasaur would be discovered rnNcrrc .=.:..aries zn the Cretaceous of New Jersey by Mitchrll

1967!. Mitchill correctly recognized hrs fossilbern similar to the Maastricht mosasaur Russell, 1967!.

Mosasaurs were platynotan lizards and had evolved from=:. "'"" e Cretaceous aigialosaurs, whrch were varanoids thats' are many similar cranial characteristics with mosasaursour. rhezr post-cranial morphology was more similar to theVaranus lrzards which are alive today rn Australia andAfrica Russell, 1967! "The skull is nearly, in everyrespect, of the pattern of the Varanidae...," Baur, 1890!,The Varanidae and Mosasauridae both have an articulatzng

joint in the middle of their rami Baur, '890!. "Among thediverse irving groups rncluded in the I acertilia, mosasaursresemble the varanids or monitor lizards most closely, afact that has been generally recognized since the beginningof the nrneteenth century," Russell, 1964, p. I!.

The varanids are a very old group of reptrles goingback at least to the Jurassic Williston, 1904!. Thed sccverv of Arazalosauridae and Dolrchosauridae in theearly la er Cretaceous of England and Yugoslavia helpeddevelop a mos- =- r nd lizard assocrarion b cause they both

possesse- vararorc characteristrcsdecided tha mc =- azrs could not h


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dclichcsaurs '" cause of the greater numbe of cervicalthe dolichosaurs Russell, 1967!

icicnall v, ihe aigialosaurs, opeti.osaurs, and mosasaurs'iffer from the moni.tora in that they have seven ~ertebraein their necks a characteristic no othez reptiles possesWilliston, 1904!. The aigialosaurs, to strengthen the

case, have all the intermediate traits whi.ch link themosasaurs to the monitors Williston, 1914!.

Ncsasaurs belong to the Order Souamata, which isdescribed as: "A single, upper temporal vacuity, or,secondarily none; quadrate loosely articulated with cranium;teeth on palate; intercentra more or less persistent; asingle coracoid; ribs single-headed, central," Williston,1914, p. 17!. One very distinguishing feature of thisOrder, which makes up a majority of all 1'ving reptiles, is

its members have overlapping dermal scales Williston,1914!. Osborn, after studying the mosasaurs, decided thatmosasaurs were an ancient offshoot of the Lacertilia

Russell, 1967!. The Lacertilia are described aspossessir,g: "Continuity of the parietal and sphenoid wallsinterrupted. Rami of the mandible united by suture," Cope,1864, p. 224!. "Ancestral mosasaur" seem to have been oftwo basic ypes; forms with long bodies and short dilatedtails giving zi.se to the mosasaurines, anci forms with shortbodies and iona pointed tails giving rise to theplioplatecarpi. es and tylosaurines," Russo 1, 1967!.


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10

e dave'oped the Order, Pyzhonomorpha,ncluszon of mosasaurs Russell, 1967!

r'ginally, in Cope's Pythonomorpha andafter examin.ing the characteristics for Cope's

deca ed . osasaurs could not be separated from the;R .sse'1, 1967! . Leidy liked the idea of a separate

cf ept'les for the mosasaurs but he did not like the"Py honomorpha" Russell, 1967!. Eventually, Marsh

and ned the term and put the suborder Mosasauria in the

Lace tilia based on, "the presence of a sternum, fore and'mw , anzi the absence of palatine teeth," Russell,

1907,p. 9!.Presently, there are three recognized subfamilies of

Mosasauzidae: the Mosasaurinae, the Plioplatecarpinae, andthe Tylosauzinae Russell, 1967!. The Mosasaurinae is

composed of three tribes: the Mosasaur z , theGlobidensini, and the Plotosaurini Russell, 1967!. The

Plioplatecarpinae is composed of two trzbes: thePlioplatecarpini, and the Pzognathodontznz and theTylosaurznae has no tribes Russell, 1967!. Presently,there are approxzmately thirteen genera and thirty speciesof mosasaurs Russell, 1967!. The Tribe MosasauriniGervazs, 1653! Russell, 1967 has "Twelve or less pygal

vertebrae present. Radius and ulna widelv separated bybzicge or carp- za on distal border of az tebzachazlforamen," Pus e' , 1967, p. 124!. The Mosasaurini arecomposed oz the genera Clidastes Cope, LBBB, Mosasaurus


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11

Cc- -ease, 322, .aurpnekepuhis Mehl, 1930, and tzodon Owen,little is known about the osteology of the Trrbe

dansant Dollo, 1924! Russell, 1967. However, it rsbe eoarate from the Mosasaurinr due to itssp' erical teeth Russell, 1967!. This tribe is

c" prised of the genus Globidens Gilmore, 1912. Russellibes the Tribe Plotosaurini as having, "More than

'''elve pygal vertebrae present. Radius and ulna nearlycontact above carpalia on distal border of antebrachial

fora..cn," Russell, 1967, p. 145!. Based on differences in!.e ...anus, the Plotosaurini are separated in a unique trzbe

from the rest of the Mosasaurinae Russell, 1967!. The

Plotosaurrnr is composed of the generaPlotosaurus Camp,1951, Compressidens Dollo, 1924, and Taniwhasaurus Hector,1874.

Within the Plioplatecarpinae, the TribePlioplatecarpinr Dollo, 1884! Russell, 1967, has a "Canalthrough basrocczprtal and basisphenoid for basilar artery.Delrcately proportioned jaws, teeth striated and subcircularin cross-section. Chevrons free. These are generallymosasaurs of moderate size, with relatively short jaws andlong, slender teeth," Russell, 1967, p. 148!. This tribeis made cp of the genera Piatecarpus Cope, 1869,:ctenos urus Merrian, 1894, and Piiopiatecarpus Dollo, 1882Rus el', 1967!. The Prognathociontini Russell, 1967, has a

"Deep gros:e '..: oo of basroccrpital anc basrsphenoid forhastier artery. Ma sivelv proportior ed jaws, teeth faceted


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12='": -1 in crcaudal centra," Russell, 1967, p. 162!

the Prognatodontini appear plioplatecarpine butmore massive and have correspondingly larger

R"ssell, 1967!. The Prognathodontini is composedoenera Pzognathodon Dollo, 1889, and Plesdotylosaurus

1942 Russell, 1967!. There are some genera of thePlioplatecarprnae which have an uncertain tribal affiliation

specifically, Halisaurus Marsh, 1869, and Dollosauzus

Takovlev, 1901. The subfamily Tylosaurinae is its own tribeand is composed of the generaTylosauzus Marsh, !872, andHainosauzus Dollo, 1885 Russell, 1967!. Theze are many

species of mosasaurs which have uncertain taxonomicplacement Russell, 1967! and this information can causeconfusion when studying the literature.

The Maastzicht mosasaur went unnamed for quite sometime. party-two years after its discovery, the fossil wasgiven the generic name Mosasaurus Russell, 1967!. Over theyears, the trzvzal name belgicus, camperz, giganteus, andhoffmanni where also applied Russell, 1967!. Mantell, in1828, determined that Mosasaurus hoffmanni was the earliestname applied to the Maastricht mosasaur Russell, 1967!. Asa result, Mosasauzushofrmanni Mantell, 1828, became the

Mosasaurus genotype Pezsson, 1959!. in 1830, a mosasaurwas dzscovered zn the Missouri territory which was described

by Harlan and ".old uss and was named by Harlan asIchthyo eurus ...:ssourzensis Russell, 1967!. Later, t.hzs


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13

bechanged toMosasaurus missou iensis Russell,:: e species Mosasaurus dekayi was esrabli.shed from a

ie cro n of a tooth from New Jersey Russell, 1967! and

ge us Ciidasteswasestablished on a single dorsal

ebr-'868K!.Mosasaurs were interesting and fz gl teningcreatures.Often, zheirnature of appearancehas spawned i.deas ofseamonsters existing in the pzesent day. 'Take, for example

:his passaae:he sea serpents,or mosasaurs, grew to be as much as

40 feet long. They had scales like a s ake. Their jaws also had hingesor joints, one at the middle ofthe chin and two at eachside,which allowed themouthto gape very widely, and to swallo very largeanimals. On the other hand, unlike snakes, theypossessed small limbs in the form of ' ve f' ngeredflippers. It is interesting to note that theseseaserpents died outabout thesame tir:.e that thelivingcoelacanth was previously thought to have becomeextinct, so that it is hard to deny completelythai.r possible existence in the sea roc!ay. Smith,1956!

Mosasaurs, which swam with axial sub-und ations of theposterior portion of the body usingtheir flippersandneck for equilibriumandsteering Lingham-Soli.ar,1991!,did look a lot like the sea serpents of lore but thereis no

doubt they became extinct like the dinosaurs.Although Marsh and Copearecredited with proving

mosasaurs had flippers, a man named Herma n Schlegel 804-1884! ','== he " : o make the d' cover; ..41 publish theresults ;N 'der .-.=' heunissen, lo86,'. Sc! egel,who was


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o" the Rijksmuseum van Maturli7ke Historic insade the discovery in 1854 Nulder and Theunissen,Rreviously, mosasaurs had been thought to have beenwalk on land. Schlegel proved this theory incorrect

xam. ning the mosasaur phalanges and noticing a lack ofattachments for muscles or tendons the opposite of what issee. in land animals Mulder and Theunissen, 1986!.

The cranium of a mosasaur is an interesting de~i.ce.Cver the coarse of their evolution, the mosasaurian cranium


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15

presence of calcified tympanrc membranes has beened as being an indrcatron of deep-sea divrng they

unco for submarine hearing and protection of the::.". annal ear from sudden pressure changes Vaughn andawson, 1956!. Many people believe calcified tympanic

membranes are a characteristic of Plioplatecarpus and thattneir presence is diagnostic of the monogeneric familyPl'oplatecarpidae Vaughn and Dawson, 1956!. Evidence ofcalcif'ed tympanic membranes can be seen in some specimens

Gr Platecarpus especially one specimen of Platecarpvsictericusl from the Niobrara of Kansas Vaughn and Dawson,19561. It is certain that Plioplarecarous nad calcifiedtympanic membranes and that Williston found tnem inI'ylosaurus but there is no further direc evidence of themoccurring in other mosasaurs Vaughn and Dawso , 1956!.

Perhaps, althoughrare!y preserved, a. calcifiedtympanic membrane was a structure commeven all mosasaurs! perhaps the membran

mosasaurs in which ituncalcified cartilage.have been a pathologage. Vaughn and DaMosasaurs, ir North America, lived 'n ihe

epicontinental sea which covered the interior of the

cor.trnent. "Mosasaurs inhabited


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informatics, the Smoky Hill MD rota was deposzted z

..nfav"rable conditions for bottom creatures Seven,

Cc-:.parazzve1y little rs known about immature.-..osasau s and, although only a few young mosasaurs are known

d Sheldon, 1986! they are known from approximatelyformations in the United States of America Sheldon,

1993!. It has been suggested that they lived in fresh waterspecifzcally, rivers! and this might have had an influence

on thezr preservation Camp, 1942!.Mosasaurs are known throughout the wozld. They are

known from Antarctica, Niger Lingham-Soliaz, 1991!,England, Belgium, Russia, France, New Jersey, Georgia,Alabama, Mississippi, Texas, New Mexico, Colorado, Kansas,

Nebraska, North Dakota, South Dakota, Nyomir g and otherlocalitres in the United States of America Williston, 1914,

Camp, 1942!. Unfortunately, most mosasaur material is notvery effective when used in a stratigraphic context duecrushed and fragmentary condrtion most are found in Camp,1942!. It is known, however, that they only occur in the

Upper Cretaceous and that, "The earliest occur in beds ofUpper Cenomzan aqe rn Kent, where only fragmentary specimensare known," Camp, 1942, p. 1!. Local genera of mosasaursare not wide-ranqing Camp, 1942! and this fact, no doubt,!' as an znfluet ca on their effectzveness as a stratigraphrctool. Mosasaur =- . ssouruensis was found in "a hard bluish

gray lzmestone, he " th junctron of he Yellow-stone and


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sess" Harlan, 1834, p. 440!. Mosasaurs are

tbe Nzobrara of Kansas, whne animals in the world, a

Sha = ' : aze not seen in the Niobrara of South Dakota

ozobab'y a result of poor exposures of the Niobrara in thesta'e Sevon, 1957!. In 1957, Clddastes tortor, wasrecovered from the South Dakota Niobrara approximately

een feet below the Niobrara/Pierre contact Sevon,

19 ;,!. A Platecazpus wasrecovered from the Upper Niobraranear inton, North Dakota ailliston, 1902!. An undescribed

spec es of Plioplatecazpus was discovered in the SharonSprr. gs Member of the Pierre Shale of Nyoming Burnham,1992!.


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AGES AND LOCATIONS

nresence of Mtooth, most likely isP. primaevus butlink between Newevidence of a waterwavdekayi provides

Jersey and North Dakota and an argument " n ne made that the

tooth belongs toP.depressus. At least, tI e presenthe ge:us .='icp'aecarpus is known in =.". Ti=-.ber Lakof the .ox Bi =-. .he rwo mosasauriar ::=-" ebrae recovered

IS

exa..inst on of the stratigraphic occurrences of thefossils examined in this paper reveals range extensions andan increase in geographic occurrences or all of the fossils.

Previously,Mosasaurus dekayi was known from theMaastrichti.an aged Dorf and Fox, 1957! Navesink Formation

of New Jersey Russell, 1967!. The discovery of the M.dekayi in this paper extended the geographic range to BowmanCounty, North Dakota and increases the sr atigraphic rangero the Timber Lake Member of the Fox Bills Formati.on alsoMaastrichtianl. The Plioplatecarpus sp. provides aninteresting questions. It could possibly be of twodifferent species Plioplatecarpus orimaevus Russell, 1967orP.depressus Cope, 1869.Pli oplatscarpus primaevus isknown from the DeGrey Member, Campania . aced Bunker, et.al, 1988!, of the Lower Pierre Shale or Souci' DakotaRussell, 1967!. Plioplatecarpusdepre s is known from

the Navesink of New Jersey Russell, 1967!. Unfortunately,

the incomplete nature of the tooth and . he lack of any other

material prevenrs proper identificatio" o the fossil. The


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19

" mber Lake Member support the presence cf :rs r he Fox Hills

e..:s Basilemys was first seen in the Judith Riverana and Canada Hay, 1908!. It has been

rec :e =-.' rc..: the Timber Lake Member of the Fox Hills:.-= ..aticn of South Dakota Bouchard, 1990!. Its presence in

Dakota represent.s a geographic link between theMor;sana/Canada and South Dakota localities. The speciesB.

sinuosa Riggs 1906, has been found in association with

Triceratops, Trachodon, and other Laramie fossils Hay,1908! providing further fossil evidence of themarine/deltaic transitional paleoenvironmental setting ofthe I'ox Hills Formation. The presence of the Tyrannosaurid

tooth, a terrestrial fossrl, further supports the notion theterrestrial link to the Fox Hills paleoenvironments.

Tyrannosaurs I'. rex! are known from the overlaying HellCreek Formation. The tooth's presence in the Timber LakeMember of the Fox Hills Formation provid s a stratigraphicrange extension down from the Hell Creek.

No signifrcant stratigraphic rnformation can be derivedfrom the fragmental and incomplete reptilran fossrls. Allare anterpreted as being marine faunas and they providecontinued evidence of the transitronal nature of the FoxHills. Perhaps, they will be identified and their exactvalue to the knowledge of the Fox Halls will be quantified.


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21

c.:s, maroonish shale approximately 1 footth clayier lzthologies hrgher

;appz ximately25 feet!

cement.ed, fine to medium grained, purplesandstone which thine laterally.

:nourated, brown weathering, fine, laminated,'azk brown, silty sandstone interpreted as

berng channel fall. Upper 1 footbentonitic/bentonite. Capped by Unit 6.

n'ndurated, buff weathering, fine to very fine,ferrugineous, slightly resistent lamir ated,

25'+

0'5"

1'10"

0 lignaceous salty sandstone.X3 Unrndurated, fine to very fine, uba..euler to

angular, buff weathering, orange-tan

1'0"

salty-clayey sandstone grading upward toI greenish gray, laminated, micaceous,

31'

a=icy sancsro e with la ge scale t ougn crossbed ' nc. Indurared un ts are lease' 5 in nature

silty-clayey sandstone. Pod of garosize ?lobserved 3 feet from top of the unit . arneOphiomorpha common on restricted hor'zona.Large Ophiomorpha observed 25 feet frc. case ofthe unrt. Topped by lignitic, laminated, siltysandstone. Large Ophiomorpha sugge t onditions

becoming estuarine upward.2* Indurated, frne to medium grained, suoangular,

b: =" weazherrng, micaceous, lamrnazed, an,


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22

:=- 'era lv ' o unindurated sands of a

co-,-osit'on. Occasional Ophiomorpha areindurated unrt. Lower contact

3'1"

rated, fine to very fine, subangular tobuff weathering, tan, laminated,

silty-clayey sandstone. Small tosmall Ophfomorpha are seen but are rare.

Un't g ades upward into Unit 2. 2'7"

65'total thickness

Note: The section bindurated ledge in tFormation. The basby valley fill. Therefore, the entire thHills has not been measured.

Section at Locality A1050

westward-facing gully on a large slump block with a small

stream incision, T. 130 N., R. 106H.,Sec. 24, Bowman


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23

feet andinches!

ake Member

rated upwardsUnrndurated, buff-tan weathering, brown clay

lenses of sandstone and dark black! clay.:o .er contact gradational.

Ur:ndurated, dark brown weatherina, da kbrown-black clay. Grades into Unrr 5.

3 Unrndurated, fine to very fine, angular tosubangular, buff weathering, tan, siltysandstone. Presence of Ophiomorpha sug estedby small piece of tunnel. Pods of 'arc ite ?!observed

2 Unindurated, dark gray wearherinc, gray to black

1'3"

0'2.5"

0'3.5"

clay with popcornesgue weatberirucharacteristics. Thine larerall 0'0.5"

1 Unindurated, fine to verv fire, anc:lar tosubangular, buff we-=bering, an, '=-=..:.":.=":ed,silty sandstone. 3'4.5"

5'9"total theet ess

Slump Block Mc. ". ;:- = = s 'a2!

rat-ci, buff weathering, dark gray clay 0'4"

incurs-ed, buff weathering, broone whfch becomes more cl


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Thickness

!feet andLaches!

5:lls FormationTrmber Lake Member

' nit

23* Indurated, fine to very fine, buff weathering,tan, micaceous, silty sandstone withlaminations and trough crossbedding. Lensoidin nature and grading laterally into sandswith similar compositions and containingOphiomorpha no Ophiomorpha in indurated

portion!. Lower contact gradational.22 Unindurated, fine to very fine,buff

weatherrnq, angular to subangular stronglylaminated, tan, silty-clayey sandstone withlenses of light brown to dark brown clays,

grades upwards into unit 23.21 Indurated, fine, brown weathering, purple Mn02

0'9"

Bt3

0'2.5"cemented sandstone20 Unindurated, brown-buff weathering, dark brown

clay with lenses of silty sandstone.5"-I" thick!.

19 Unindurated, fine to very fine, angular tosubangular, buff weathering, tan, strongly

1 .inated, aritysandstone withthin lenses of

0'3"

clay.Possible microchannelfallsand5'ss le1'2"user =-= on inoles observed

IB U. ' =.=-:=== "', bro- n-* -ff weatne" nc, da k browncl=-, "= ='=. -': ==- :ate ally ,''ensoi"' .n nature!.0'1"


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Fegu e 1.-- St ratzgrap'nicCelur.e -: S te '= ".SST. 13

e 's Se". 2-'l


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2G

.=':.=ared, fine to very fine, buffweathering, ran, silty sandstone.:nincurated, buff-brown weathering, dark brown

0'2"

0'1,5"cl v15 Unindurated, fine to very fine, buff

weathering, laminated, angultan, silty sandstone.

14 Unindurated, gray weathering, dark gray clay

1'0"

13 Uz indurated, fine to very fine, laminated, buff0'1"weathering, tan, silty sandstone.

12 Unindurated, gray weathering, dark gray clay0'0.5"which thine laterally.

11 Unindurated, fine to very fine, subangulaz to

angular, laminated, buff weathering, ra.,silty sandstone.

10 Unindurated, buff-gray weathering, dark gray

0'10.5"

clay which thine laterally lensoid in nature. 0'2"9 Unindurated, fine to very fine, buff

weathering, tan, silty sandstone.

8 Uninduzated, buff-brown weathering, brown-darkbrown clay. Highest observed occurrence offossil reptile remains.

7 Un'ndurated, fine to very fine, angul r tosubangular, buff weathering, tan, siltysan" stone '" "'.-. ine 1am nations.

0'1.5"

0'2"

1'1"

6 Uninctrazed, - :: weathering, gray-dark gray

which thine laterally, lensoid in nature. 0'0.5"


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27

0'2"

rated, buff-brown weathering, brown-orange-:'"-stone grading upwards into uninduratedsilty clay. 0'5"

4 Unindurated, buff weathering,3 Unindurated, fine to very fine,

weathering, orange-tan, silty-clayey sandstone.0'2.5"2 Uz ndurated, fine to very fine, buff

weathering, dark gray clay. 0'l.5"

1 iJnindurated, fine to very fine, angular tosubangular, buff weathering, tan, siltysandstone. Pods of jarosite ?! observed. 0'10"

total t..'' c.cn ss 9'3.5"

composrte total hick. ess 13'2"

Section at Locality 2

Cut bank of Seven sil reekcr.:but ="; consists of aSs -sc loN., B. 106 N., Sec. 25Foot Block Fio: re 2l

Thickness

feet and


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rnches!

Sim'lar in texture and appearance to Unit 8 butnot indurated buff weathering, fine to veryfine, tan, silty sandstone, with lamrnations.Trough crossbedding present. Outcrop capped byvalley fill.

8 Similar in texture and appearance to Unit 6buzf-brown weathering, but sand/clayir terbedding appears to occur in closer

8' 10'

6'-7intervals.

14' 5"

tan-orange, laminated sandstone witlinterbeddings Mn08/clay layers. A possiblebentonite layer was observed. Grades upwardinto sandstone of similar lithology wh'ch isbioturbated and contains Ophi omorpha. Lo''ercontact gradatronal.

5 Unrnd rated, fane to very fine, buff weathering,

gr yish-tan, lamrnated, silty sandstone. Grades

0' ll"

1' 10"ento nrr 6.

7- Loosely indurated, fine to very fine, buffweathering, lensoid, tan, silty sandstone which

grades laterally into unindurated sar detune withthe same lithology. Ophdomorpha and ' argecrossbedding are present. Interfingers, in a

step-wise manne , with brown units Mn08 andclayl 10" to 1' thick.6 Unindurated, fine to very fine, buff weathering,


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29

:rated, fine to very fine, buff weathering,

;.: osseous, laminated, tan, silty sandstone whzch.:=-=beds wath dark brown fissile clay layers 1

4 inches thick. Pods of jarosite ?!obsezved. Capped by a 0.5" indurated, brownweathering, fine to very fine, brown, siltysandstone with Mn02.

3 Uninourated, fine to very fine, buff weathering,laminated, tan to brown., silty sandstone with

nodules of dazk brown clay. Interbeddings ofclay become more common towards the top of theunit.

0I3 5

7' 1"

1 Unindurated, fine to very fine, b

laminated, tan, sandstone with idark clay. Small pods of jarosite ! present.Grades upward into a lensoid, indurared unitwith similar compositzon. Capped by Unit 2. 3' 8"

total thickness 53' 3.5"

Hanging Block Figure 2!Pie re Shaleand

Thickness

!feet andinches!

Fox Hills "or .atzo

Unit

2 Unindurated, brown weathering, dark brown clay. 0' 1"


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30

nd-rated, fine to very fane, buff weathering,d, tan, silty sandstone wrth >aroszte

gods and interbeddrngs of clay lenses.Capped by lensoid, indurated sandstones ofsrmilar composition which exhibit trough crossbecioing. Clay beds 1"-1.5" thick are seen.approximately 6-6.5 feet from the bottom of theunit. Ophfomozpha present below and lateral totne indurated .unit but are not very common. 8'5"

Unzndurated, light gray to gray weaihering, darkg ay to gray clayey siltstone with pods of

jarosite ?!, interbeddings of fine, lami atedsandstone and shale towards top. Sraoes intoUnzt 2. 30'3"

total thi kne s 38' 8"

composite total ti ckness 91' 3.5"

Specimens from site OY3 where take".. rom the IronLightnrng contact in the Fox Hills Format'on in EmmonsCounty T. 132 N., R. 75 W., Sec. 1 . H fer to Figure 3 fora generalized stratigraphic placement of he contact.


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33

Site 1

Site A1050

Figu e 2.--Stratrgrap33ic Correlation of S' es 1, A1050, & 2 Sr e 2


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32

HELL CREEK FM.

LiN ON MBR

m

0Ill

CL'

0u'X0

LUm

TRAIL CITY MBRPIERRE SHALE

Figure 3. Strat2.graphic Column showing ron Lightning/Fox

Ha.lls Ccntaci an ' s. atigraphrc level of si e OY3 T. 132N. R. 3 W. Sec. Emmons Count .'""=.-. Dakota .

00IL

0Z

Z cs'z I0 gZ~0


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SYSTEMATIC PALEONTOLOGY

CLASS ReptiliaSUBCLASS Lepidosauria

ORDER SquamataSUBORDER Lacertilia

FAMILY Mosasaridae Gervais 1853SUBFAMILY Mosasaurinae Williston 1897

GENUS Mosasaurus Conybeare 1822teat . usually prismatic with relatively flat

x. Da and ro:nded internal surfaces," Russell, 1967!SPECIES Mosasaurus dekayi Bronn 1838

Referred specimen. KS Specimen, single marginal tooth.Collected by R.M. Feldmannn at site OY3, T. 132 N., R. 75W., Sec. 1, Emmons County, North Dakota.

Diagnosis and Description. This tooth is 4.2 cm tall, 1.9cm wide, and 1.6 cm thick. The tooth is d'vided into

buccal Figure 4! and lingual Figure 5! sides by aprominent longi.rudinal carina Figure 6!. The buccal sideis nearly flat having a slight curvature! and is dividedinto four facets by fairly distinct carinae Figure 4!. Asone looks at the tooth as it seen in Figure 4, the widths oftie facets from left to right are: 0.3 cm, 0.4 cm, 0.6 cm,and 0.85 cm. The lingual side possesses a. strong curvatureand i.s divided into ten facets by fa'rlv cistinct carinaeFigure 5!. Referring to Figure 5, the widths of the facets

from left to right are: 0.65 cm, 0.4 cm, 0.3 cm, 0.3 cm,

33


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0.4 cm, 0.3 cm, 0.4 cm, 0.4 cm, and 0 .5 cm. Onhe buccal and lzngual sides, the facets are their

v szons begin to smooth closer to the tip untilapproxzmately one third to one quarter of the tooth issmooth and lacking facets.

Due to the size and curvatures of the lzngual andbuccal sides, the tooth is nearly triangular in crosssection. An examination of the base of the tooth Figure 4!reveals a nerve cavity which is approximately 1 cm deep.

Discussion. Based on the broken enamel and uneven naturec rhe base, the marginal tooth has been interpreted ashaving been lost before it could be replaced Figures 4,5 &6!. The tooth zs posterzorily recurved and the tip isbroken off most probably due to wear. Using the number offacets on the buccal and lingual side of the tooth and its

morphology and a diagram and description of a known74.

dekayf Figure 7! Russell, 1994!, the tcoth has beenidentified as Mosasaurus dekayi.Stratzgraphzc Ievel ard Age.-- Thzs toot!. was collectedfrom the Timber Lake/Iron Lightning Member boundry of theFox Hills Formation. It is Maastrichtian in age.

CLASS ReptiliaSUBCLASS Lepidosauria

ORDER Squamata


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Bigure -'..-- Mosasa "usdekayi,KS specznen, site OY3. ScaleA. :- seal sade. B. Base o= tooth


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Fig re . Mosasaosus dekayi,KSspeczm .,szte OY3.Scale ha"s cm. .'.:co=eel she. B. Tp of tooth.


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:rgure 6. Mosasaurus deka',

BS specrmea, sate OY3. Scale bar-s cru S de vre..s of the tooths..o' l..c 'o .o t"dr:al carrnaeA. B' ca t 'ot.B. Bucc 1to left


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38

/

nisei ~ *5'- 8

Fsgure 7. Yc ese "us ceksyz, illustsu ' - . c: knownspec nen !tecec Fccc gussell, 1994!.


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SUBORDER Lac rtiliaFAMILYMosasari dae Gervais 1853

SUBFAMILY Plioplatecarpinae Dollo 1884TRIBE Plioplatecarpini Dollo 1884GENUS Plioplatecarpus Dollo 1882

"Mandibular teeth bicarinate ?!, vertically striated andmedially recurved Dollo, 1882, p. 64; 1889b, pl. 10 fig.14" Russell, 1967!.

Referred Specimen.-- NDGS specimen, szngle fragment of atooth collected by Dr. John Hoganson approximately one milenorth of site A1050.

Diagnosis and Description. The tooth fragment is 1.4 cmtall, 0.7 cm wide, and 0.5 cm thick Figures 8 & 9!. Twolongrtudznal carinae are faintly visible ',Figure 10!. The

tzp and base of the have been broken of probably due toloss before replacement.Discusszon. The very small size of ti.e tooth makesidentzfzcation dzfficult. After rt was ciiscovered by JohnHoganson, it was taken to Dr. Gorden Be 1, Jr. whoidentified it as belonging to the Genus " iopiatecazpusDollo 1882. It may belong to the species Plzopiatecarpusprimaveus Russell, 1967 which is known from the DeGreyMember of the lower Pierre Shale of South Dakota Russell,1967!. The rooth is nterpreted to have been broken, andsubsequently lost, d e to wear based on: he strarght break


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40

Figure B.--P1ioplatecarpus sp., DGSspecime., recovered approximately 1 mile from siteAltg.. Sca'e bar is1 cm.A. Buccal srde. B. Frp of too


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Figure 9. Blioplatecarpus sp., NDGS specimen,recovered approximately 1 mile from site A1050. Scalebar is 1 cm.A. Langual s de. B. Base of tooth.


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Figure 10.-- Pdropi.atecarpus sp., NDGS specimen, recoveredapproximately 1 mrle from site A1050. Scale bar is 1 cm.Side vre. s of rocth showing very faint longitudinal carinae.A. Buccal to = cht. B. Buccal to left.


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seen on the base of the specimen, the missing tap, and theex namely worn longrtudanal carrnae.Stratigraphic level and Acre.-- This tooth was recovered:rom the Timber Lake Member of the Fox Hills Formation, Itis Maastrichtian in age.

ORDER SguamataSUBORDER Lacertilia

FAMILY Mosasauridae Gervaas 1853

Re ar ed spacemen.-- SLU No. 1833, single vertebra.Collected by J. Mark Erickson at A131, T. 128 N., R. 80 N.,Sec. 6, Sroux County, North Dakota.

Diagnosis and Description. -- The vertebra is 2 cm wide 3 1cm tall, and 2.3 cm thick. Both articu sting surfaces aresmooth and a slaghtly raised ridge may be seen on the upper

portion of the fossil fpz.gare ll!Discussion.-- This vertebra was recovered from a

Dosiniopsis pod by J. Mark Erickson and 'dentified by Dr.Gorden Bell Jr. as belongrng to some kind of a mosasaur.

Stratigraphic level and Age. -- The vertebra is from theTimber Lake Member of the Fox Hills Formation and is

Maastrrchtian an age.

ORDER SguamataSUBORDER LacertrlzaFAMILYMosasauradae


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I',g 'op.Figure j'. ."..""= =': eertecra, S'g Yo. 1B33, srte A131Scale bar


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Figure 2. Nosasaur vertebra, SLU No. 1834, T. 132 N., R.78 W., Sec 3, :-. .=,.=-.. Cou. ty, North Dakcta. Scale bar is 1cm.


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46

specimen. SLU No. 1B34, single vertebra.llected by J. Mark Erickson at the northeast corner ofi32 N., R. 78 W., Sec. 3, 9 miles west and I/2 mile north

of Linton, Emmons County, North Dakota.Diagnosis andDescription.-- The vertebra is 4.5 cm tall,3.4 cm wide, and 3.9 cm thick fpigure 12!. It has asomewhat pear-shaped cross section and has a raised edgeimilar to the previous vertebra.'acus i on.-- This fossil has been identified as a mosasaur

based on its similar morphology with the previous vertebraidentified by Dr. Gorden Bell Jr. Unfortunately, thisvertebra is in not as good condition as the other because itwas damaged when the concretion it was in was cracked open.The bone also appears to have been fairly worn previous toits incorporation as the core for the concretion.

Apparently, the vertebra was free to roll around on theocean bottom for some time.

Stratigraphic Level and Age. This vertebra was collectedfrom the upper Timber Lake Member of the Fox HillsFormatron. It is Maastrrchtian in age.

INFRACIASS ArchosauromorphaSUPERORDER Archosauria

ORDER CrocodyliaSUBORDER Eosuchia

FAMILY CrocodylidaeSUBFAMILY Crocodylinae


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Figure 13.--Zl edpos" caus sp., KS spec'.-.. =, site OY3. Scalebar is 1 cre A. -=- rae .. B. Base c: Got?.


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Frgure 14.-- ieoyosuchus sp., KS spec me , ite QY3. Scalebar is cr... '. .=.re or ried,. B. Tip o-. oath.


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50

SUBCLASS TestudinataORDER Chelonia

SUBORDERCryptodi ra SUPERFAMILY TrionychozdaeFAMILY Dezmatemydzdae

GENUS Basiiemys Hay, 1902

"Shell highly sculptured. Epiplasrra much thickened.Bridge wade. Intergular scutes present. Pectorals greatlyex assed at the midline, narrowed laterally. An axillarya c an ngu0nal scute but no other ir. ra,arginals....Thisgenu cif ers from other known genera o De matemydidiae inhavi a no inframarginals, except the axi lary and theinguinal, " IHay, 1908! .Referzed specimen.-- KS Specimen, cern scute collected by

R.M. Feldmannn at site OY3, T. 132 N., R. 78 N., Sec. 1,Emmons County, North Dakota

Dzagnosis and Desc iption. -- The fr- c:e t is approximately4.3 cm long, 2 cm wide, and 2 cm tall. It . ss a veryconvoluted, bumpy surface and has twc ta 1, cone-shapeduprazszngs with well defined tips IFzgu Sl. The bone isfairly solid zn appearance and sturdy zn s zucture.Di scr ss ~ on. This piece was identizzed by Dz . JohnHoganson as bezng a dermal scute f o,. the e bow or knee ofsasi le...ys sp. based on direct compari on ', th a speczmenfrom the vzell '-''seu.... The two cone-1' ze sr zres with theturtle's carapace, = astzon, and other scares, no doubt


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Sl

Figure 13.-- Basilemys sp. dermal scute, KS specimen, siteQY3. Scale bar s - cm. A. Side view. B. Top view.


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some: har efzective defense and protection fromthe wears and rears of daily life.* evel and Age. This fragment was collectedz Lake/Iron Lightning Member contact in the

.ation. It is Maastrichtian in age.

CLASS ReptiliaSUBCLASS Archosauria

ORDER Saurischia

SUBORDER TheropodiaINFRAORDER CarnosauriaFAMILY Tyrannosauridae

Referred specimen.-- KS Specimen, tooth rragment collectedby R.M. Feldmann at site OY3, T. 132 N., R. 75N.,Sec. 1,

Emmons County, North Dakota.Diagnosis and Description.-- The piece is approximately 2.6cm tall, .8 cm wide, and .7 cm thick. Fart of the lateral

carina i.s present Figure 16!. The enamel i smooth andlacks any indication of longitudinal o :azeral division.Discussior.-- The tooth was identified by Phil Curry of the

Tyrell Museum as a Tyrannosaurid based on he serration onzhe carina. The piece appears to be fro., near the tip ofthe tooth. Unfortunately, the incomp'eze .. ure of thetooth preve zs its f..rther identification.


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Figure 16.-- TYrannosaurid tooth fragment, KS specimen, siteQY3. Scaie bar 3.s 1 cm. A. Side view carina is to theleft!. B. Base of ragment.


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graphic Level and Age.-- This specrmen was recovered:","=.. ear the Timber Lake/Iron Lightnrng Member boundry of

."ox Bills Formation. It is Maastrichtian in age.

CLASS Reptilia

Referred Speczmens.-- SLU No. 1832 fragmentary material,fragment of metacarpal ?!, and larger, thinner fragmentpossibly skull material! collected. from T. 130 N., R. 106

W., Sec. 25, Bowman County, North Dakota.Diagnosis and Description.-- The larger, thin fragment isapproximately 9.9 cm long, 9.5 cm wide, and ranges inthickness from 1.1 cm on the left side Figure 18! to a

thin, knife-like edge on the curved and right hand edgesI'igure 18!. The piece is very porous and is perforated by

several nerve canals which intersect the surf~ca of the boneat approximately 45 degrees. The bone has a curvature whichslightly flattens towards the knife-lake curved edge.

The metacarpal ?! has a maximum hefoht o" 3.3 cm, amaximum width of 1.6 cm which thine to .55 c.-. and a maximum

depth of 1.5 cm Frgure 17!. The piece has been broken andonly approximately one half of the tot.al none rs present.

The numerous fragments of bone rarge in length fromapproximately I cm to approximately 6 cm and range in widthfrom apprcx':..ately I cm to approximately 6 cm. Most of thepieces are rectangular in general sha e a..d - e composed ofcompac , struts 'r ' bone


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Figure 17.-- Reptilran metacarpal fragment, SLU No. 1S32,sate ATGSG. Scale bar as 1 cm. A. Sade r ew. B. "Top"iew look ..o =" =-=- culatang surface


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Figure 18. Rept'lian Turtle ?!! skull ?! fragment, SLUNo. 1832, site '1050. Scale bar is 1 cr..


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Due to the extreme fragmentary nature of theficat on is extremely difficult. The

pcr-"'-'= bone appears to be skull material and themay be rib material. The metacarpal

cesar"les '.-. -' seen in Protostega sp.. However,cation is impossible without a definite

of the thin bone's identity.Level and Age. The material was collected-" oi' c

:amber Lake Member of the Fox Hills Formation

31 feet above the Pierre Shale boundry. It isprcximatelyas =.'chi an in Age

CLASS Reptilia

Referred Specimen.-- NDGS specimen, metacarpal collected by

John Hoganson approximately one mile north of s'te A1050.Diagnosis and Description.-- The metacarpal is 3 cm tall,has a maximum wrdth of 1.4 cm, and has a maximum thicknessof 1.3 cm Figure 19!. The shaft of the bone 's fairlysmooth and the articulatrng surfaces are rein' ively flat.D 'scussion. -- This bone is too small to oe identified by

self.Based entirely on conjecture, o e can state that it.:.ost likely belongs to a mosasaur or turtle.

Szratagraphic Level and Age. -- This bone was collected intie 'amber Lake Member of the Fox Hills For=.,ation. It isMaas richt.=."


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P' gure 9.-- 5 11'a . metacarpal, NDGS pecimen, recoveredapprox -... el: mile : om sate A1050. Scale bar is 1 cm.A. Sr e ; . B. ": p" v ew lookino o. to articulatingsurfac


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SUMMARY

of r.-e fossils represent either a stratrgraphic orrange extensron. The presence of Mosasaurus

and the Plloplatecarpus provide evidence of a lrnkbetween the Maastrichitian deposits of New Jersey and theNaastrichtian deposits of North Dakota. However, the exactspecies of thePlfoplatecarpus is unknown and it mayrepresent a stratigraphic and geographic range extensionzrom the Campanran of South Dakota. The mosasaur vertebrae,

even though they can not be effectively identified, providefurther evidence to the presence of mosasaurs in the FoxHills Formatron of North Dakota. The discovery of theBasi lemys sp. scute provides a geographic link to theBasilemys sp. seen in the Fox Hills of South Dakota andthose seen rn the JudithRiver beds of Montana and Canada.

The presence of the tyrannosaur tooth fragment in the FoxHills represents a stratigraphic range extension from theoverlaying Hell Creek Formation. The unidentified reptilianfossil remains nrovide material support to the reptilianpresence of the Fox Hills but, until they are identified,wrll not provrde anv clues to any range or geographic rangeextens'ons.

The fossils, when vzewed individually, provide evidence

of stratrgraphrc and geographic range extensrons. However,when tl ev a e vrewed as a whole we see a combinatron ofterresrrial --., ma ine faunas. This faunal evidence further


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60

the deltaic environmental interpretation of the Fox:-.'lls sediments


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REFERENCES

1890. On the characters and Systematic

positron of the large sea lizards, Mosasauridae.e, 16:2orden L. Jr. and Sheldon, Mary Amy. 1986.

esc zptzon of a very Young Mosasaur from GreensCounty, Alabama. Journal of the Alabama Academy ofScience, 57 !:76-82.

Bcuchard, T. R. 1990. The Lowez Veztebrates of the FoxHills Formation in Meade County, South Dakota. SouthDakota School of Mines and Technology, Rapid City, S.D.82p.

Bunker, B. J., Witzke, B. J., Watney, W. L., and Ludvigson,G. A. 1988. Phaneroroic History of tie CentalMidcontinent, United States, In: Sloss, L. L., ed.The Geology of North America, Sedimentary Cover NorthAmerican Craton: U.S. The Geological Society ofAmerica, 0-2:243-260.

Sauamata, Mosasauridae! from the Sharon Springs Membezof the Pzerre Fo nation Campanian of Wyoming [abstrl.Journal of Vertebrate Paleontology, p. 20A.

Camp, C.L. 1962. Cal fornza Mosasaurs. Be keley:.vers of Cal fornza Press, 66p

Carper ter, S. :., Er ckson J. M., Lohmann, K. C., and Owenrageneszs of Fossilzfero s Concretzons

61


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6 7

" e" Cretaceous Fox Hzlls Formation, North

ournal of Sedimentary Petrology, 58 !:706-

1864. On the Characters of the Higher Groups of. = =dinge of the Academy of Natural Science of

'adelphia: 224-231,1868. On Some Cretaceous Reptilia. Proceedings

of the Academy of Natural Science of Philadelphia: 233

-282C- er, G. C. F. 1808. Sur le grand animal fossile des

arriere de Maastricht. Mus. Hist. Nat. Paris Ann.12:185-176 not seen!.

Dorf, Erling and Fox, S. K. 1957. Czetaceous and Cenozoicof the New Jezsey Coastal Plain, ln: Dorf, Erling,

ed. Guidebook for Field Trips, Atlantic City Meeting,1957. The Geological Society of Ame ' ca: 1-27.

Erickson, J. M. 1992. Subsurface Saran graphy,Lithofacies, and Paleoenvironments o he Fox HillsFormation Maastrichtian: Late Cretaceous! Adjacent tothe Type Area, North Dakota and So: akota Toward aMore Holistic View. North Dakota Ceolocical SurveyMiscellaneous Series, 76:199-241.

Gregczy, J. ~ . '951. Convergent evolution the jaws ofMHar =-;, . " '.. Not ce of the discovery -" the remains of


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