Brontotheriidae (Perissodactyla) from the late early and middle Eocene (Bridgerian), Wasatch and Bridger formations, southern Green River Basin, southwestern Wyoming

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BRONTOTHERIIDAE (PERISSODACTYLA) FROM THE LATE EARLY ANDMIDDLE EOCENE (BRIDGERIAN) WASATCH AND BRIDGER FORMATIONSSOUTHERN GREEN RIVER BASIN SOUTHWESTERN WYOMINGAuthor(s) GREGG F GUNNELL and VICKI L YARBOROUGHSource Journal of Vertebrate Paleontology 20(2)349-368 2000Published By The Society of Vertebrate PaleontologyDOI httpdxdoiorg1016710272-4634(2000)020[0349BPFTLE]20CO2URL httpwwwbiooneorgdoifull1016710272-4634282000290205B03493ABPFTLE5D20CO3B2

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349

Journal of Vertebrate Paleontology 20(2)349ndash368 June 2000 2000 by the Society of Vertebrate Paleontology

BRONTOTHERIIDAE (PERISSODACTYLA) FROM THE LATE EARLY AND MIDDLE EOCENE(BRIDGERIAN) WASATCH AND BRIDGER FORMATIONS SOUTHERN GREEN RIVER BASIN

SOUTHWESTERN WYOMING

GREGG F GUNNELL1 and VICKI L YARBOROUGH2

1Museum of Paleontology University of Michigan Ann Arbor Michigan 48109-10792Yale Peabody Museum New Haven Connecticut 06520

ABSTRACTmdashThe perissodactyl family Brontotheriidae is represented by large numbers of specimens from latest earlyand middle Eocene sediments of the Western Interior of North America Species level taxonomy of brontotheres hasbeen confusing and the relationships of the earliest occurring species to those that occur later have not been welldocumented or understood Evidence based on new specimens from the earliest Bridgerian from the Green River Basinin particular from South Pass and Opal coupled with a reanalysis of previously existing specimens has led to thefollowing conclusions concerning the alpha taxonomy of Bridgerian North American brontotheres Four genera (Eoti-tanops Palaeosyops Mesatirhinus and Telmatherium) are recognizedEotitanops is represented by two speciesEborealis andE minimus andPalaeosyops by five speciesP paludosus P fontinalis P laevidens P robustus andP laticeps

A re-examination of the temporal distribution of brontotheres requires that the biochronologic framework of thelatest early to earliest middle Eocene be modified The earliest Bridgerian can be defined by the first appearance ofEotitanops borealis in the Wind River Basin and Wapiti Valley both in Wyoming and at Huerfano Park ColoradoThis interval has been termed theEotitanops borealis Assemblage Zone and is equivalent to the early GardnerbutteanBridgerian Biochronologic Zone Br0 The first appearances ofPalaeosyops fontinalis and Eotitanops minimus markthe onset of the second biochronologic interval of the Bridgerian Br1 here referred to informally as the rsquorsquoPalaeosyopsfontinalis Assemblage Zonersquorsquo This interval includes the late Gardnerbuttean (Br1a) and Bridger A (Br1b) Biochron-ologic Zones Br0 and Br1 are now included in the latest early Eocene while Br2 coincides with the beginning of themiddle Eocene

INTRODUCTION

Fossil mammals have been known from Eocene sediments inthe southern Green River Basin in southwestern Wyoming forover 150 years (Matthew 1909 West 1990) One of the earliestmammals described from this area wasPalaeosyops paludosus(Leidy 1870) a brontotheriid perissodactyl Since the initialdescription ofP paludosus no less than 11 additional generaand 28 species have been proposed for the Bridgerian radiationof brontotheres Revisions of various aspects of this radiationhave been attempted in the past (Earle 1891 1892 Wallace1980 Mader 1989 1998) but much confusion still remainsconcerning the species level taxonomy of brontotheresOsborn (1929) was the last authority to attempt a completespecies-level revision of all Eocene and Oligocene North Amer-ican brontotheres However due to his confusion over the na-ture of variability within and between species the nature offossil preservation and Osbornrsquos curious view of evolutionaryprocesses the resulting monograph created as many problemsas it solved In a sense the study of brontothere systematics iscursed by a wealth of information There are so many wellpreserved skulls and skeletal elements of Eocene brontotheresavailable that the task of sorting out their alpha taxonomy isdaunting requiring great amounts of time and travel

The results that follow are based on several years of inter-mittent travel to museums along with new specimens discov-ered over the past eight years of field work in the Green RiverBasin in southwestern Wyoming A joint University of Michi-gan-Albion College field project in the Wasatch and Bridgerformations has produced many new specimens of earliestBridgerian (Gardnerbuttean and Bridger A) brontotheres Thesespecimens along with some previously known material haveclarified the relationships among early bronotheres and form thebasis of this report

We have chosen to concentrate on dental evidence in this

study Much brontothere systematic work has been based oncranial morphology because of the availability of so manyskulls (Osborn 1929 Mader 1989) while tooth size and mor-phology have been relied upon less heavily Yet tooth size andmorphology have proven useful in sorting out species-level tax-onomy in many mammalian groups (Gingerich 1974 1976)and we feel that such is also the case for brontotheres We haveincluded cranial and postcranial features when they have ap-peared relevant but most of what follows is based on bron-tothere dental remains Most of the diagnostic features usefulfor sorting out brontothere taxonomy can be found in the upperdentition although a few features of the lower dentition haveproven useful The fact that most type specimens of previouslynamed Bridgerian brontotheres are either skulls or upper den-titions also makes careful study of upper teeth most profitable

Institutional AbbreviationsmdashAMNH American Museumof Natural History New YorkCM Carnegie Museum of Nat-ural History PittsburghMPM Milwaukee Public MuseumMilwaukee RAM Raymond M Alf Museum Webb SchoolClaremontUM University of Michigan Museum of Paleon-tology Ann Arbor USGS United States Geological SurveyDenver [specimens now housed at the USNM in WashingtonDC] USNM United States National Museum WashingtonDC YPM Yale Peabody Museum New HavenYPM-PUPrinceton University Yale Peabody Museum New Haven Allmeasurements are in millimeters (mm)

SYSTEMATIC PALEONTOLOGY

Order PERISSODACTYLA Owen 1848Suborder CERATOMORPHA Wood 1937Family BRONTOTHERIIDAE Marsh 1873

PALAEOSYOPS Leidy 1870

Limnohyus Marsh 1872124Limnohyops Marsh 1890525

350 JOURNAL OF VERTEBRATE PALEONTOLOGY VOL 20 NO 2 2000

FIGURE 1 Skull of Palaeosyops paludosus (UM 98890 neotype) in palatal view Scale equals 10 cm

Eometarhinus Osborn 1919568

Type SpeciesmdashPalaeosyops paludosusIncluded North American SpeciesmdashPalaeosyops paludo-

sus P laticeps P robustus P fontinalis and P laevidensDiagnosismdashPalaeosyops differs from Eotitanops in being

larger and having a relatively short C1ndashP1 diastema and lack-ing or having a very short P1ndash2 diastema a P1 with a buccallyinflated paracone and a short and broad posterior shelf oftenwith a distal cusplet a P2 with a metacone and a mesiobucallyinflated paracone a P3ndash4 with better developed more roundedprotocones and stronger buccal ridges often with incipient me-sostyles and upper molars with protocone and hypocone sep-arated by a deeply incised valley more acute and cuspate pro-

tocone and hypocone and more deeply excavated trigon basinsDiffers from Mesatirhinus in having upper premolars withparacone and metacone more buccally placed and less inclinedlingually P3ndash4 broader than long and with less deeply exca-vated lingual ectoflexus more square upper molars with lessdeeply excavated lingual ectoflexus and paracone and meta-cone more buccally placed Differs from Telmatherium in beingsmaller in lacking or having weakly incipient W-shaped ecto-lophs on P3ndash4 less robust and buccally projecting parastylesand mesostyles and lacking horn swellings on the frontonasalboundary

Known DistributionmdashLatest early to early middle Eocene(Bridgerian) of Wyoming Colorado and Montana

351GUNNELL AND YARBOROUGHmdashBRIDGERIAN BRONTOTHERES

FIGURE 2 Skull of Palaeosyops fontinalis (UM 102869) in palatal view Scale equals 10 cm

OccurrencemdashEarly through late Bridgerian Wasatch andBridger formations southern Green River Basin Wyomingearly Bridgerian Willwood Formation Wapiti Valley north-western Wyoming earliest Bridgerian Huerfano FormationHuerfano Park Colorado earliest Bridgerian Cathedral BluffsTongue Wasatch Formation Washakie Basin Wyoming Bridg-erian Sage Creek Formation Montana (Tabrum pers comm1997)

PALAEOSYOPS PALUDOSUS Leidy 1870(Fig 1)

Palaeosyops paludosus Leidy 1870113Palaeosyops major Leidy 1871229

Canis montanus Marsh 1871123Palaeosyops junius Leidy 1872277Palaeosyops minor Earle 1891112Palaeosyops longirostris Earle 1892338Canis marshii Hay 1899253Limnohyops matthewi Osborn 1908602

NeotypemdashUM 98890 (Fig 1) skull left and right dentariesskeletal elements

Type LocalitymdashUniversity of Michigan locality BB-83Uinta County Wyoming

Type HorizonmdashLower Bridger Formation earliest middleEocene Bridgerian Biochronologic Zone Br2 (Bridger B)

DiagnosismdashDiffers from Palaeosyops fontinalis in being


FIGURE 3 Upper and lower teeth and postcrania of Palaeosyops fontinalis A right maxilla with P1ndashM3 (UM 102869) in occlusal view Bright p2 (left) and left p4 (right) (UM 102898) in occlusal view C left m3 (UM 103417) in occlusal view D right humerus (a) in posteriorview left ulna (b) in anterior view left radius (c) in anterior view left and right scapular fragments (d) in posterior view left astragalus (e) indorsal view and right patella (f) in posterior view Figure Dandashd are from UM 100669 e is from UM 100414 and f is from UM 100904 Scalesin Figures AndashC equal 1 cm scale in D equals 10 cm

larger P2ndash3 with distinct metacones that are separated from theparacones and more centrally placed protocone shelves P4 withstronger buccal ridges and incipient mesostyles and upper mo-lars with better developed parastyles and mesostyles with themesostyles being buccally inflated throughout instead of justbasally as in P fontinalis Differs from P robustus in beingsmaller in some tooth dimensions less strongly developedmetacones on P2ndash3 lacking an incipient W-shaped ectoloph onP4 and less robust upper molar parastyles and mesostyles Dif-

fers from P laevidens in being larger with more molarized P2ndash4 Differs from P laticeps in being larger

Referred SpecimensmdashAMNH numbers 11684 (holotype ofLimnohyops matthewi) 12182 14561 108084 108090108107 108114 108115 MPM numbers 3905 5248 52495255 5263 5272 5299 5308 MPM field numbers 80-210 80-227 80-251 88-140 UM 9800 95724 98808 98810 9881398816 98890 (neotype) 99764 99847 99886 100525101058 101316 USNM numbers 755 758 760 762 2521


FIGURE 4 Skull of Palaeosyops fontinalis (UM 94880) in dorsal (top) and palatal (bottom) views Scales equal 10 cm

12582 12835 13451ndash13453 16862 26109 26115 2612526126 26129ndash26131 26133 26141 26146 26147 2614926150 26152 26169 26170 26172 YPM numbers 1113716715 16881

DistributionmdashReferred specimens of Palaeosyops paludo-sus are all from the middle Bridgerian (Bridgerian Zone Br2Bridger B) lower Bridger Formation southern Green River Ba-sin Wyoming

DiscussionmdashLeidy based Palaeosyops paludosus on a seriesof isolated and broken teeth collected at or near Church Butteand sent to him by F V Hayden in 1870 (Leidy 1870) Noneof these teeth were designated as a type specimen so Osborn(1929) chose USNM 759 as the lectotype of the species It isunfortunate that Osborn chose a lower second molar as the lec-totype as Bridgerian brontothere lower molars differ little fromone species to another in morphology This has led some toquestion the validity of Palaeosyops (Mader 1989) and whether

or not it is possible to diagnose P paludosus based on thissingle m2

We believe as did Mader (1989 1998) that P paludosus isa valid taxon and that Palaeosyops should be maintained as thegeneric name for most Bridgerian brontotheres However wealso believe that the lectotype specimen of P paludosus is in-determinate (a nomen dubium) as none of the character statesdiagnostic of Palaeosyops are preserved in the lectotype Wehave chosen to designate UM 98890 as the neotype specimenof P paludosus The neotype was found near Church Buttelow in the middle Bridgerian (Bridger B Bridgerian Biochron-ologic Interval Br2) and near where the lectotype was originallyfound There are two different sized brontotheres from Br2 (seeFigs 9ndash12) a small taxon represented by only a few specimensand a larger taxon represented by many more specimens in-cluding the neotype The old lectotype m2 is the same size asthe m2 in the neotype and we believe that all specimens from


FIGURE 5 Left maxilla of Eotitanops minimus (UM 103216) in occlusal view A left P1ndashP4 B left M1ndash3 Scale equals 1 cm

Br2 that are similar in size and that share the neotype dentalmorphology should be assigned to Palaeosyops paludosus

If Palaeosyops is not accepted as a valid genus the nextavailable generic name would be Limnohyus Marsh 1872 (Os-born 1929 Mader 1989) Marsh (1872) originally describedLimnohyus for Bridgerian brontotheres that lacked M3 hypo-cones However Leidy (1872) pointed out that the original typesample of P paludosus teeth included an M3 lacking a hypo-cone thus Limnohyus could not be distinguished from Palaeo-syops based on this character state Therefore Marsh (1890)proposed yet a third genus Limnohyops to accommodate thoseBridgerian brontotheres that did have M3 hypocones As Mader(1989) has pointed out and as our studies have confirmed M3hypocone development appears variable throughout the Bridg-erian radiation of brontotheres and as such by itself is notparticularly useful as a taxonomic indicator especially at thegeneric level We believe that all three genera can be includedin Palaeosyops and see little reason to reject that genus in favorof either of the other two proposed genera Table 1 gives sum-mary tooth measurements for Palaeosyops paludosus

PALAEOSYOPS LATICEPS Marsh 1872

Palaeosyops laticeps Marsh 1872122Limnohyops laticeps Marsh 1890525

HolotypemdashYPM 11000 skull partial skeletonType LocalitymdashMarshrsquos Fork approximately 25 Km from

Fort Bridger precise locality unknownType HorizonmdashUpper Bridger Formation early middle Eo-

cene Bridgerian Biochronologic Zone Br3 (Bridger C)DiagnosismdashDiffers from contemporaneous Palaeosyops ro-

bustus and from earlier occurring P paludosus in being smaller

especially in upper premolar dimensions and with relativelydistinct hypocones on M3 Differs from P fontinalis in havingmuch more molarized upper premolars Differs from P laevi-dens in being somewhat smaller with more molarized upperpremolars

Referred SpecimensmdashMPM number 5298 USNM numbers763 6704 YPM number 11138 possibly AMNH number11678

DistributionmdashReferred specimens of Palaeosyops laticepsare from the late Bridgerian (Bridgerian Zone Br3 Bridger C)upper Bridger Formation southern Green River Basin Wyo-ming

DiscussionmdashMarsh (1872) originally described this taxon asa species of Palaeosyops but because of his confusion aboutthe variation and distribution of M3 hypocones among Bridg-erian brontotheres (see discussions above and below) he laterproposed a new genus Limnohyops to accommodate this spe-cies (Marsh 1890) Osborn (1929) felt that Limnohyops wasdistinct from Palaeosyops and maintained the former with Llaticeps as the type species of the genus As noted above thereis little to differentiate Limnohyops from Palaeosyops and noreason to recognize the former genus as valid Table 2 givessummary tooth measurements for Palaeosyops laticeps

PALAEOSYOPS ROBUSTUS (Marsh 1872)

Limnohyus robustus Marsh 1872124Palaeosyops humilis Leidy 1872168Palaeosyops diaconus Cope 18734Palaeosyops leidyi Osborn 1908604Palaeosyops grangeri Osborn 1908604Palaeosyops copei Osborn 1908606


TABLE 1 Summary tooth statistics for Palaeosyops paludosus Abbreviations x mean SD standard deviation N number of specimens CVcoefficient of variation L length W width

Tooth position x SD Range N CV

c1 LW

211195

134162

190ndash237180ndash221

88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967

TABLE 2 Summary tooth statistics for Palaeosyops laticeps Abbreviations as in Table 1


c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753


TABLE 3 Summary tooth statistics for Palaeosyops robustus Abbre-viations as in Table 1

Toothposition x SD Range N CV

c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156

HolotypemdashYPM 11122 palate with L amp R P2ndashM3 R den-tary p4 m3

Type LocalitymdashWest side of Henrys Fork Divide UintaCounty Wyoming precise locality unknown

Type HorizonmdashUpper Bridger Formation early middle Eo-cene Bridgerian Biochronologic Zone Br3 (Bridger C)

DiagnosismdashDiffers from P fontinalis in being larger withmuch more molarized P2ndash4 with well developed metacones andincipient mesostyles P4 with an incipient W-shaped ectolophand a robust centered protocone shelf upper molars with betterdeveloped parastyles and mesostyles with the mesostyles beingbuccally inflated throughout Differs from P paludosus in beingconsistently larger in some tooth dimensions (not all) in lack-ing a C1ndashP1 diastema with more molarized P2ndash4 and morerobust upper molar mesostyles and parastyles Differs from Plaevidens in being larger in all tooth dimensions with moremolarized P2ndash4 and more robust upper molar mesostyles andparastyles Differs from P laticeps in being larger in all toothdimensions and with more robust upper molar mesostyles andparastyles

Referred SpecimensmdashAMNH numbers 1516 1522 1544(holotype of Palaeosyops leidyi) 1565 5102 5106 (holotypeof Palaeosyops diaconus) 11683 11708 (holotype of Palaeo-syops copei) 11710 12185 12189 (holotype of Palaeosyopsgrangeri) 12196 12198 12201 91059 107955 107957108100 108116 MPM numbers 5273 5307 5309ndash5314 53165318 MPM accession numbers 24590 24670 MPM field num-bers 80-79 80-165 80-412 80-450 UM numbers 3075 308995771 USNM numbers 753 754 756 12694 13454 1345716660 16661 26112 26120 26139 26167 26306 (holotypeof Palaeosyops humilis) YPM numbers 11123 11124 1112611127 11133 16408 16708 YPM-PU numbers 1000910282(b)

DistributionmdashReferred specimens of Palaeosyops robustusare all from the late Bridgerian (Bridgerian Zone Br3 BridgerCndashD) upper Bridger Formation southern Green River BasinWyoming

DiscussionmdashThe sample of Palaeosyops robustus as definedby the referred specimens listed above is a morphologicallyvariable one Some specimens have stronger development ofupper premolar features such as W-shaped ectolophs and incip-ient mesostyles than other specimens Some specimens have ahypocone developed on P2 (two specimens of P paludosus alsoexhibit this character state AMNH 108084 USNM 26115)The character states cited by Osborn (1908) to justify recog-nition of three additional species of Palaeosyops (P leidyi Pgrangeri and P copei) in the later Bridgerian appear to us tobe simple variations in a relatively highly variable species Wewere unable to find any consistent differences that would war-rant separation of this sample into two or more species Table3 gives summary tooth measurements for Palaeosyops robus-tus

PALAEOSYOPS FONTINALIS (Cope 1873)(Figs 2ndash4)

Limnohyus fontinalis Cope 187335Eometarhinus huerfanensis Osborn 1919568Eotitanops sp Morris 1954197Brontotheriid near Palaeosyops fontinalis Gazin 196275Palaeosyops fontinalis (in part) Robinson 196664Palaeosyops fontinalis McGrew and Sullivan 197081 Gun-

nell et al 1992274 Gunnell 1998123Eotitanops borealis Bown1982A55 (in part)cf Eotitanops sp Bown1982A55cf Palaeosyops fontinalis Bown1982A55

HolotypemdashAMNH 5107 R maxilla dP4ndashM1 M2 eruptingType LocalitymdashBluff on the Green River near the mouth

of the Big Sandy Sweetwater County Wyoming precise lo-cality unknown but probably from an area now known as Lom-bard Buttes

Type HorizonmdashLower Bridger Formation latest early Eo-cene Bridgerian Biochronologic Zone Br1b (Bridger A)

DiagnosismdashPalaeosyops fontinalis can be differentiatedfrom all other species of Bridgerian Palaeosyops except P lae-videns and P laticeps by its small size Further differs from alllater occurring species of Palaeosyops in having primitive P2ndash3 that lack or have very small metacones and low distallyplaced protocone shelves and upper molars with relativelyweaker mesostyles and parastyles mesostyles being mesiolin-gually compressed and rounded buccally but only basally in-flated not throughout their extent as in later occurring species

Referred SpecimensmdashAMNH numbers 17013 17411ndash17417 17425 17450 55282 56540 104772 UM numbers80642 92880 94880 95636 98623 99815 100414 100471100478 100660 100669 100904 100920 101692 102153102162 102163 102197 102206 102830 102869 102898102900 102912 103290 103380 103417 103452 103683USGS numbers 1994ndash1997 USNM 22766 YPM numbers16450 16451 16459 16463 51425 YPM-PU number 16110

DistributionmdashReferred specimens of Palaeosyops fontinaliscome from the earliest Bridgerian (Gardnerbuttean and BridgerA) upper Wasatch and lower Bridger formations southernGreen River Basin and South Pass earliest Bridgerian Will-wood Formation Wapiti Valley earliest Bridgerian HuerfanoFormation Huerfano Park Colorado earliest Bridgerian Ca-thedral Bluffs Tongue of the Wasatch Formation Washakie Ba-sin Wyoming early Bridgerian Aycross Formation southernAbsaroka Range Wyoming Wallace (1980) notes the presenceof P fontinalis from the Boysen Reservoir area Wind River


FIGURE 6 Eotitanops and Palaeosyops upper premolars demonstrating differences between the two genera and evolutionary changes APalaeosyops paludosus (MPM 3905) right maxilla with P2ndash4 from Bridgerian zone Br2 showing (a) P2 with a distinct laterally placed metacone(b) P2 with a distinct and anteriorly placed protocone and (c) P3ndash4 with strong buccal ridges and well developed buccal ectoloph expansion BPalaeosyops fontinalis (UM 102869) right maxilla with P2ndash4 from Bridgerian Zone Br1b showing (a) P3 with a low protocone positionedposterior of center (b) an indistinct low posteriorly placed P2 protocone (c) P4 with a moderate buccal ridge and weak buccal ectoloph expansionand (d) P2 with a strong postparacrista but no metacone developed C Eotitanops minimus (UM 103216) left maxilla with P1ndash4 from BridgerianZone Br1b showing (a) P2 with a weak postparacrista and no metacone (b) P2 with a very low posteriorly placed protocone that is only weaklyexpanded lingually (c) P4 with a weak buccal ridge and no buccal ectoloph expansion and (d) a large P1ndashP2 diastema Scales equal 2 cm

Basin Wyoming and its possible presence in the Sage Creekbeds of Montana

DescriptionmdashPalaeosyops fontinalis previously was poorlyrepresented in the fossil record Eight years of field work byUniversity of Michigan-Albion College expeditions has pro-duced a relatively large sample of P fontinalis including twopartial skulls and several partial skeletons We take this oppor-

tunity to describe more fully the osteology of this taxon in lightof the new specimens now available

Two skulls represent P fontinalis UM 94880 from the lowerBridger Formation Bridgerian Zone Br1b and UM 102869from the upper Wasatch Formation Bridgerian Zone Br1aHowever neither UM skull is perfectly preserved UM 102869only preserves the palate and parts of the basicranium (Fig 2)


FIGURE 7 Palaeosyops lower premolar size distribution from Bridg-erian Biostratigraphic zones Br1b through Br3 X axis represents naturallog of tooth area Y axis represents Biostratigraphic Zone

FIGURE 8 Palaeosyops lower molar size distribution from Bridger-ian Biostratigraphic zones Br1b through Br3 X axis represents naturallog of tooth area Y axis represents Biostratigraphic Zone

UM 94880 (Fig 4) is better preserved and most of the cranialroof is intact although crushed flat It appears to share mostderived character states noted by Mader (1989) for Palaeo-syops The skull is brachycephalic and has robust curving zy-gomatic arches The zygomatics have a very sharply definedcrest extending along their dorsal surfaces The nasals are verylarge and apparently curved ventrally at their anterior end Thenasals are broad throughout their extent and do not appear totaper anteriorly as was suggested by Mader (1989) as typicalof Palaeosyops There is a slight doming of the skull roof atthe frontoparietal contact The parietals form strong overhang-ing ledges laterally The sagittal crest is well formed very pos-teriorly placed and has a distinctive pit at its anterior end thatextends into a well developed narrow groove that extends thelength of the crest

On the dorsal aspect of UM 94880 only the palatal regionis well preserved The palatal fissures appear to be completelyenclosed within the premaxilla although this is difficult to becertain of because of breakage The fissures are separated bythe palatal bridge of the premaxilla that forms two parallel bonyplates These plates continue anteriorly as parallel ridges acrossthe premaxilla Anterior palatal foramina are found at about thelevel of the mesiolingual root of M1 There are at least sixaccessory palatal foramina located posteriorly on the maxillaryand palatine bones

The pterygoids are both broken but appear to have been ro-

bust and heavily built The basioccipital has a well developedridge extending anteroposteriorly across its dorsal surface Thisridge appears to extend onto the basisphenoid but this area isobscured by breakage The rest of the basicranium is eitherbroken or missing The glenoid fossae are broad and flat andthere are very strong postglenoid processes The glenoids arebounded medially by fairly strong protuberances but are openlaterally

The premaxilla of UM 94880 shows that P fontinalis likeother species of Palaeosyops had six upper incisors with thelateral pair being the largest There is a moderate (85 mm)diastema between I3 and the canine One upper incisor foundassociated with UM 102869 is preserved intact It is a left I1or I2 and measures 86 mm mesiodistally by 84 mm buccolin-gually

Both skulls preserve fragments of the right canine and rootsof the left canine The canines are rounded in cross-sectionmoderately robust and flare laterally but not as much as inother Palaeosyops species The canines are implanted buccal toP1 and are buccal to a line passing through the buccal cusps ofthe molars The C1ndashP1 diastema is very short in UM 94880(UM 102869 is too broken to tell about this diastema) butanother specimen (YPM 16450) has a relatively longer C1ndashP1diastema Neither UM 94880 nor YPM 16450 has a P1ndash2 di-astema but a short P1ndash2 diastema (44 mm) is present in UM102869


FIGURE 9 Palaeosyops upper premolar size distribution from Bridg-erian Biostratigraphic zones Br1b through Br3 X axis represents naturallog of tooth area Y axis represents Biostratigraphic Zone

FIGURE 10 Palaeosyops upper molar size distribution from Bridg-erian Biostratigraphic zones Br1b through Br3 X axis represents naturallog of tooth area Y axis represents Biostratigraphic Zone

The P1 (Fig 3A) paracone is inflated mesiobuccally and theposterior shelf is short and relatively broad with a central ridgeformed by the postparacrista There is no distal cusplet at theterminus of the postparacrista The preparacrista is more steeplysloping than the postparacrista and curves lingually at its baseto join a weak lingual cingulum

A P2 metacone is either absent or tiny and if present is lowand incorporated into the postparacrista as a small rise in theenamel along the distolingual face of the paracone The para-cone is mesiobucally inflated and positioned just mesial of cen-ter The preparacrista is steeply sloping and curves lingually tojoin a short mesiolingual cingulum The postparacrista is moreshallowly sloping and extends to the distal margin The proto-cone is low indistinct and rounded and pre- and postprotocris-tae are weak to moderately developed The protocone shelf isdistally placed such that the apex of the protocone is alwayswell distal of the paracone The protocone shelf is mesiodistallyshort but broader buccolingually The lingual margin of theshelf is separated from the lingual flank of the paracone by ashallow mesiodistally oriented valley

The metacone of P3 is either low small and lingual or higher(but still lower than paracone) more distinct less lingual andseparated from the posterior flank of the paracone The para-cone is mesiobucally inflated with a steep preparacrista thatextends to an expanded parastylar region There is no incipientmesostyle development and the buccal ridge extending from the

apex of the paracone is weak to moderately developed Theprotocone is low rounded and distal of center The preproto-crista is weak and there is no postprotocrista present There aredistinct mesial and buccal cingula present but neither extendsaround the lingual base of the tooth

The P4 is similar to P3 but there are some differences Themetacone is better developed and less lingually placed and isnearly as tall as the paracone The parastylar region is some-what more expanded compared to P3 The buccal ridge is betterdeveloped but as in P3 there is no incipient mesostyle Theprotocone is more robust but still low and rounded It is morecentrally placed on the lingual margin than is the protocone ofP3 There is a weak preprotocrista and no postprotocrista as inP3 The protocone shelf is broader and longer relative to P3Mesial and distal cingula are better developed compared to P3both extend lingually and wrap around the base of the proto-cone but do not meet

The upper first molar has a protocone and hypocone sepa-rated by a relatively deep buccolingually extended valley Bothof these cusps are sharply defined but are rounded and lowerthan the buccal cusps A small paraconule is present and thereis no metaconule The paracone and metacone are equal inheight taller than the lingual cusps and more sharply definedThe ectoloph is very sharp and high with the ectoflexus beingwidely open and not excavated The mesostyle is compressedmesiodistally at its apex but is rounded and inflated at its buccal


FIGURE 11 Comparisons of mean upper molar area for Eotitanops minimus Eotitanops borealis and three Palaeosyops species P fontinalisP paludosus and P robustus Note that only in Eotitanops minimus does M2 size exceed M3 size

base This is unlike later occurring species of Palaeosyopswhere the mesostyle is rounded and inflated from its base to itsapex The parastyle is well developed and projects slightly morebuccally than the mesostyle The trigon basin is excavated andenclosed by the ectoloph and the protocone There are mesial(stronger) and distal (weaker) cingula M2 is very similar toM1 differing only in being larger with a better developed me-sostyle and parastyle in having the protocone and hypoconeseparated by a stronger and deeper valley and in having stron-ger mesial and distal cingula

M3 is also similar to other molars but differs in some im-portant ways There is no hypocone and the hypocone shelf isonly weakly expanded A small rugosity or crest often runsfrom the distal cingulum toward the trigon basin in the positionof the hypocone The parastyle is larger than in M1ndash2 and thepreparacrista is expanded taller and more sharply crested Theectoflexus is not as widely open as in the other molars and issomewhat more excavated as is the trigon basin Mesial anddistal cingula are better developed than in M1ndash2 M3 is as largeas or larger than M2

Lower teeth of Palaeosyops fontinalis are not as well rep-resented as the upper dentition UM 102898 (Fig 3B) includesa right p2 and a left p4 in association The p2 is relatively longand narrow (178 by 87 mm) The protoconid is tall with adistinct lingually curving paracristid extending from the apexto a very weak anterior cingulid No paraconid or metaconid ispresent The talonid consists of a single centered distal cuspwith a crest extending to the base of the protoconid where itjoins a relatively weak postprotocristid The talonid slopes awaysteeply both buccally and lingually from this crest There areno cingulids developed except mesially

P4 is about as long as but much broader than p2 (176 by114 mm) The protoconid and metaconid are of equal heightand connected to form a strong protolophid The paracristid isrelatively broad and curves lingually from the apex of the pro-toconid to the mesiolingual base of the tooth The talonid con-

tains only a single cusp a buccally placed hypoconid The cris-tid obliqua is strong and extends from the apex of the hypo-conid to join a short postmetacristid at the distolingual edge ofthe metaconid A sloping postcristid runs from the hypoconidto the lingual margin of the tooth The talonid basin slopeslingually and is open between the cristid obliqua and the post-cristid A very weak buccal cingulid is present

For the most part the few lower molars known of Palaeo-syops fontinalis do not differ much from later occurring Pa-laeosyops species except in size Lower molars of all Palaeo-syops species exhibit tall well-formed para- proto- meta- andhypolophids Proto- meta- hypo- and entoconids are well de-veloped but not distinct in the sense that they are incorporatedinto lophids as part of a continuous series of crests Paraconidsnormally are not as developed as the other cusps and are smallerand lower when present Trigonid fovea and talonid basins aremesiodistally broad and both are widely open lingually Thehypoflexid is deeply incised and cingulids are only weakly de-veloped buccally and distally if at all

There are a few slight differences between Palaeosyops fon-tinalis lower molars and those of other Palaeosyops speciesMetacristids and entocristids are often well developed in lateroccurring species of Palaeosyops but appear to be weak or ab-sent in P fontinalis The hypoconulid of m3 (Fig 3C) is alsosomewhat simpler in P fontinalis The hypoconulid lobe iswell-formed and extends distally to a well developed hypocon-ulid The hypoconulid is connected to the distolingual wall ofthe hypolophid below the top of the crest and just below theentoconid Lingual to this hypoconulid crest the hypoconulidslopes away and does not form a lingual shelf (UM 103417)In later occurring Palaeosyops species the lingual shelf tendsto be much better developed and often has a lingual ridge ex-tending along the margin to enclose the lingual shelf

Postcrania of Palaeosyops fontinalis have never been de-scribed Several specimens in the UM collections preserve post-cranial elements but none is very complete UM 100669 pre-


serves the most postcranial elements including left and righthumeri left radius and ulna fragments of left and right scap-ulae several broken cervical and thoracic vertebrae and nu-merous ribs and rib fragments UM 100414 includes a brokenleft astragalus and a patella while UM 100904 includes a com-plete left astragalus

The scapular fragments (Fig 3Dd) preserve only the glenoidcavity and a portion of the neck The glenoid is concave elon-gate superior-inferiorly and narrower dorsoventrally The cor-acoid is broken but it appears that it was moderate in devel-opment The spine of the scapula appears to have been ratherheavy judging from the small part of it that is present

UM 100669 includes the distal three-quarters of the righthumerus and the proximal third of the left humerus The lefthumerus is so poorly preserved that little can be said of itsmorphology other than the fact that the humeral head was ex-panded mediolaterally and constricted anteroposteriorly Thecurvature of the head wraps distally but not as far as in Pa-laeosyops robustus (MPM Accession number 24602)

The right humerus of UM 100669 is much better preserved(Fig 3Da) The deltopectoral crest and deltoid tuberosity arewell developed and extend distally below midshaft Medial andlateral epicondyles are relatively small and the trochlea is rel-atively shallow There is no entepicondylar foramen The olec-ranon fossa is deep but lacks a supratrochlear foramen Theradial capitulum is a simple parasagittal crest and the lateralepicondyle and supinator crest are poorly developed suggestingthat movement at the elbow was restricted to a parasagittalplane

In comparison with Palaeosyops robustus the humerus of Pfontinalis differs mostly in being less robust The deltoid tu-berosity deltopectoral crest and supinator crest are all relative-ly smaller and less well developed than in P robustus In Pfontinalis the radial capitulum is not as broad the medial andlateral epicondyles are not as strongly developed posteriorlyand the olecranon fossa is not as deep

The left ulna and radius of UM 100669 (Fig 3Dbndashc) arenearly complete The ulna is missing its distal epiphysis whilethe radius is missing its proximal epiphysis The ulna is bowedsomewhat posteriorly The olecranon process is anteroposteri-orly deep but proximodistally short The trochlear notch is rel-atively shallow and is angled proximolaterally to distomediallyThe anconeal process is mediolaterally broad The coronoidprocess is flat extends laterally beyond the shaft of the ulnaand is positioned just distal to the distal-most extent of thesemilunar notch The shaft of the ulna is triangular in cross-section being broad anteriorly and narrow posteriorly

The radial shaft is rounded proximally and anteroposteriorlycompressed distally The distal end of the radius exhibits typicalbrontothere morphology being mediolaterally broad and an-teroposteriorly narrow The styloid process does not extend fardistally The lateral carpal articular surface is concave the me-dial one is flat and angled These articular surfaces are separatedby a weak ridge

As with the humerus the ulna and radius of P fontinalisdiffer from those of P robustus mostly in degree of robustnessMorphologically the ulna of P fontinalis differs in having arelatively shorter olecranon process and a smaller less anteri-orly projecting anconeal process The radius of P fontinalisdiffers in having a weaker less distally extended anterior radialprocess and in having a shallower lateral carpal articular sur-face The shaft of the radius is less laterally bowed than in Probustus

The astragalus of Palaeosyops fontinalis (UM 100904 Fig3De) has a grooved trochlea with the lateral trochlear marginbeing slightly higher than the medial margin The surface forarticulation with the fibula is broken but an additional astrag-alar specimen (UM 103683) shows that a well developed fibular

articular surface was present There is no astragalar foramenThe astragalar neck is short and the head broad In distal viewthe head is trapezoidal being wider dorsally and narrower plan-tarly The calcaneal articular surface is concave and relativelybroad The sustentacular articular surface is elongate proximo-distally and very narrow mediolaterally It extends distally tothe plantar border of the astragalar head In this feature Pfontinalis differs from P robustus where the sustentacular ar-ticulation is broader and more restricted distally not reachingthe plantar border of the head

UM 100414 includes a patella (probably from the right side)The patella (Fig 3Df) is nearly as thick anteroposteriorly (371mm) as it is mediolaterally wide (380 mm) The articular sur-faces for the patellar groove of the femur are angled with themedial one being somewhat smaller than the lateral one Anextended patellar process was apparently present distally but isbroken so it is not possible to determine its full extent

DiscussionmdashMader (1989) expressed some doubt as towhether or not Palaeosyops fontinalis truly belonged in the ge-nus Palaeosyops We believe that the new material describedabove confirms that P fontinalis is properly placed at the ge-neric level In addition these new specimens clearly show thatP fontinalis the earliest know species of Palaeosyops is dis-tinct from Eotitanops Table 4 gives summary tooth measure-ments for Palaeosyops fontinalis

PALAEOSYOPS LAEVIDENS (Cope 1873)

Limnohyops laevidens Cope 187335Limnohyops priscus Osborn 1908601Limnohyops monoconus Osborn 1908603

HolotypemdashAMNH 5104 Skull with R I1ndashM3 L I1ndashM2Type LocalitymdashCottonwood Creek precise locality un-

knownType HorizonmdashLower Bridger Formation earliest middle

Eocene Bridgerian Biochronologic Zone Br2 (Bridger B)DiagnosismdashDiffers from contemporaneous Palaeosyops pal-

udosus and later occurring P robustus in being smaller in mosttooth dimensions especially in premolars and M1m1 and witha very small metacone and a small protocone shelf on P2 Dif-fers from P fontinalis in being slightly larger P2 with a morecentered protocone shelf and P3ndash4 with stronger metaconesDiffers from P laticeps in being somewhat smaller with lessmolarized upper premolars

Referred SpecimensmdashAMNH numbers 11679 (holotype ofLimnohyops monoconus) 11680 11687 (holotype of Limnoh-yops priscus) 11688 13032 13118 MPM numbers 52545293 5303 USNM number 26127 YPM numbers 1640916716 16817 YPM-PU number 10276

DistributionmdashReferred specimens of Palaeosyops laevidensare from the early middle Bridgerian (Bridgerian Zone Br2 lowBridger B) lower Bridger Formation southern Green River Ba-sin Wyoming

DiscussionmdashEven though we have stated above that M3 hy-pocone development is not a particularly useful character statethe development of M3 hypocones included in the hypodigmof P laevidens is often relatively strong The normal range ofvariation exhibited in Palaeosyops M3s does not include suchdistinct hypocones Some M3s have no hypocone shelf so thatthe tooth is triangular Others have a relatively wide shelf butno cuspules or crests are developed Still others have a smallcuspule developed mesial to the distal cingulum Often this cus-pule is incorporated into a small crest that extends from thedistal cingulum towards the lingual base of the metacone An-other variation is to have the distolingual corner of the toothelevated with development of a small hypocone cuspule incor-porated into the distal cingulum In the case of some of theupper dentitions here recognized as P laevidens the hypocone


TABLE 4 Summary tooth statistics for Palaeosyops fontinalis Abbreviations as in Table 1


c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271

is a relatively distinct and distally projecting cusp that is nearlyas well developed as the protocone It is separated from theprotocone by a relatively wide and deep valley Later occurringPalaeosyops laticeps also has M3 hypocones that are betterdeveloped than is normally seen in the other three species ofPalaeosyops such that it is possible if not probable that Plaevidens and P laticeps represent an ancestor-descendant lin-eage

Most of the hypodigm of P laevidens comes from low inthe early middle Bridgerian (Br2) All of these specimens areeither from the lowest portion of Br2 (Church Buttes Millers-ville) or from the lower section at Grizzly Buttes (lower Br2)It is probable that P laevidens represents a species that resultedfrom a cladogenic speciation event that produced it and P pal-udosus from a Palaeosyops fontinalis ancestry Table 5 givessummary tooth measurements for Palaeosyops laevidens

EOTITANOPS Osborn 1907

Palaeosyops Cope 1880746Lambdotherium Cope 1881196lsquolsquo Telmatotheriumrsquorsquo Osborn 1897107Telmatherium Hay 1902631Eotitanops Osborn 1907242Eotitanops West 1973143 Bown 1982A55 Novacek et al

199152 Gunnell et al 1992273

Type SpeciesmdashEotitanops borealisIncluded SpeciesmdashEotitanops borealis E minimusDiagnosismdashEotitanops differs from Palaeosyops in being

smaller with relatively long C1ndashP1 and P1ndash2 diastemata a P1that lacks a buccally inflated paracone and either lacks or hasa very short posterior shelf lacking a P2 metacone and havingonly a weak mesiobucally inflated paracone P3ndash4 with poorlydeveloped more acute protocones and smaller protocone lobes

P3ndash4 with weak buccal ridges and no incipient mesostyle de-velopment upper molars with protocone and hypocone sepa-rated by a shallow depression more rounded and low protoconeand hypocone flattened trigon basins and relatively small me-sostyles and parastyles that do not project far buccally

Known DistributionmdashLatest early Eocene (Gardnerbuttean)of Wyoming and Colorado and latest early and earliest middleEocene (Bridger AB) Wyoming Also known from early Eo-cene sediments in Baja California although the age determi-nation is not certain (Novacek et al 1991)

OccurrencemdashEarliest Bridgerian upper Wasatch Formationsouthern and northern Green River Basin Wyoming earliestBridgerian Willwood Formation Wapiti Valley earliest Bridg-erian Wind River Formation Wind River Basin Wyomingearliest Bridgerian Huerfano Formation Huerfano Park Col-orado early Bridgerian Aycross Formation southeast Absa-roka Range Wyoming Wasatchian (early Eocene) Las Tetasde Cabra Formation Baja California Mexico

EOTITANOPS BOREALIS (Cope 1880)

Palaeosyops borealis Cope 1880746Lambdotherium brownianum Cope 1881196lsquolsquo Telmatotheriumrsquorsquo boreale Osborn 1897107Telmatherium boreale Hay 1902631Eotitanops borealis Osborn 1907242 Osborn 1908600 Os-

born 1913409 Osborn 1929292 Robinson 196666West 1973143 Gunnell et al 1992273

Eotitanops brownianus Osborn 1908601 Osborn 1913408Osborn 1919563 Osborn 1929292

Eotitanops gregoryi Osborn 1913408Eotitanops princeps Osborn 1913410 Osborn 1929295Eotitanops major Osborn 1913412 Osborn 1929296lsquolsquo Titanopsrsquorsquo borealis Peterson 191457


FIGURE 12 Natural log of upper canine length versus width for Pa-laeosyops paludosus and lower canine length versus width for Palaeo-syops robustus Note that in each case there is a single outlying pointsuggesting a bimodal distribution of canine size that may indicate thepresence of sexual dimorphism in Palaeosyops canine size

Eotitanops gregoryi (in part) Osborn 1919564Eotitanops cf E princeps Novacek et al 199152

HolotypemdashAMNH 4892 right maxilla P4ndashM3 (M2ndash3 bro-ken)

Type LocalitymdashBadlands in upper drainage basin of the BigHorn (Wind) River Wind River Basin precise locality un-known

Type HorizonmdashWind River Formation latest early EoceneBridgerian Biochronologic Zone Br0 (Gardnerbuttean)

DiagnosismdashDiffers from Eotitanops minimus in being largerwith a better developed and elongate m3 hypoconulid

Referred SpecimensmdashAMNH numbers 296 (holotype ofEotitanops princeps) 4885 (holotype of Eotitanops browni-anus) 4886 14887 14888 14889 (holotype of Eotitanops gre-goryi) 14890 14891 14894 (holotype of Eotitanops major)CM numbers 22440 22442ndash22444 22446 22447 2245022542 34771 34821 35867 36459 37334 42273 4349143619ndash43622 46340 46688 46690 47233 61766 6194162208 67793 68073 69390 69476 71554 UM numbers33381 80659 80627 107824 YPM-PU numbers 1611018109 18111 18122

DistributionmdashReferred specimens of Eotitanops borealisare from the earliest Bridgerian (Bridgerian Zone Br0 earliestGardnerbuttean) upper Wind River Formation Wind River Ba-

sin the Willwood Formation Wapiti Valley and the HuerfanoFormation Huerfano Park Colorado West (1973) refers twoupper molars to Eotitanops borealis from the upper WasatchFormation early Eocene northern Green River Basin and No-vacek et al (1991) refer an isolated lower molar to Eotitanopsfrom early Eocene sediments in Baja California (see below)

DiscussionmdashAs with Bridgerian Palaeosyops there havebeen several species of Eotitanops named in the past Based onthe dental evidence available we feel that only two species areworthy of recognition E borealis is by far the more commonof the two Eotitanops species recognized here However over-all Eotitanops is a relatively uncommon taxon never makingup more than a small percentage of the total mammalian faunafrom wherever it is found

A good deal of discussion in the literature concerns the va-lidity of Eotitanops (Osborn 1929 Wallace 1980 Mader1989) Eotitanops does resemble early species of Palaeosyopsespecially P fontinalis but as can be seen from the diagnosisprovided for Eotitanops there are substantial differences be-tween the two genera and we believe that there is no justifiablereason to synonymize the two forms

West (1973) described two upper molars of Eotitanops fromthe New Fork Tongue of the Wasatch Formation These twoteeth were found together with Lambdotherium and representthe first confirmed instance of co-occurrence of these two taxa(see discussion below) and the first well documented occur-rence of Eotitanops in the Lostcabinian (Lambdotherium is theindex taxon of the Lostcabinian subage of the Wasatchian LandMammal Age)

Guthrie (1971) described two lower premolars (RAM 3403)of Palaeosyops sp supposedly found north of the town of Em-blem Wyoming in the Willwood Formation from the Graybul-lian subage of the Wasatchian Wallace (1980) questioned thevalidity of the locality information associated with these teethnoting that RAM 3403 was in fact the locality number not thespecimen number and that the Alf Museum locality number forthe Emblem locality was instead RAM 4903 The teeth appearto represent a species of Palaeosyops near P paludosus but thequestionable locality information makes this Wasatchian occur-rence of Palaeosyops dubius

Novacek et al (1991) note the presence of single lower sec-ond molar of Eotitanops from the Lomas las Tetas de Cabrafauna from Baja California This fauna is correlated with Was-atchian (early Eocene) faunas from western North AmericaHowever Novacek et al (1991) were uncertain that the lowermolar in question actually came from the Wasatchian sedi-ments noting that it was possible that the specimen was derivedfrom younger sediments capping the Wasatchian unit

A search of brontothere specimens at the Peabody MuseumYale University turned up an additional Eotitanops tooth (YPM22090) from the Wasatchian YPM 22090 is a left lower thirdmolar from near Yale locality 8 Big Horn County WyomingYale locality 8 is at the 591 meter level of the local section asreported by Bown et al (1994) placing it in the lower part ofthe Lostcabinian The tooth matches morphologically well withEotitanops borealis and is of comparable size (length 209width 126) There is no apparent problem with the localityinformation so this tooth seems to represent the third occur-rence of Eotitanops in the Lostcabinian Table 6 gives sum-mary tooth measurements for Eotitanops borealis

EOTITANOPS MINIMUS Osborn 1919(Fig 5)

Eotitanops gregoryi (in part) Osborn 1919564Eotitanops minimus Osborn 1919564 Osborn 1929199 Rob-

inson 196667Palaeosyops fontinalis (in part) Robinson 196664


FIGURE 13 Summary of the newly proposed zonation of the earliest Bridgerian based on the distribution of brontotheriids AbbreviationsWRB Wind River Basin SGRB Southern Green River Basin Note that we consider the earliest Bridgerian to be part of the latest early Eocenebased on new paleomagnetic interpretations (Clyde pers comm)

TABLE 5 Summary tooth statistics for Palaeosyops laevidens Abbreviations as in Table 1


c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662


TABLE 6 Summary tooth statistics for Eotitanops borealis Abbreviations as in Table 1


p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100

Eotitanops borealis Bown 1982A55 (in part)

HolotypemdashAMNH 17439 Left dentary p4-m3Type LocalitymdashHuerfano Locality II Huerfano Park Col-

oradoType HorizonmdashUpper Huerfano Formation latest early Eo-

cene Bridgerian Biochronologic Zone Br1a (Gardnerbuttean)DiagnosismdashDiffers from Eotitanops borealis in being small-

er with a weaker less distally extended m3 hypoconulidReferred SpecimensmdashAMNH numbers 17418 56539

96281 104773 UM number 103216 USGS numbers 1990ndash1993 YPM-PU numbers 16439 16462

DistributionmdashLatest early Eocene (late Gardnerbuttean) up-per Huerfano Formation Huerfano Park Colorado and UpperWasatch Formation South Pass Wyoming latest early to ear-liest middle Eocene (Bridger AB) Aycross Formation south-east Absaroka Range Wyoming

DiscussionmdashWallace (1980) in a highly regarded yet un-published masterrsquos thesis felt that two genera were representedby this sample of what we regard as the single species Eoti-tanops minimus Wallace argued that E gregoryi was sufficient-ly distinctive to be recognized as a species separate from Eborealis but felt that both of those species could be included inthe genus Palaeosyops This left a third taxon Eotitanops min-imus without a generic assignment as Wallace (1980) felt thatthis species could not be included in Palaeosyops He thereforeproposed a new genus for E minimus Our analysis of the rel-evant specimens suggests that E borealis and E gregoryi arethe same species (E borealis) and that E minimus is not suf-ficiently distinct from Eotitanops borealis to be recognized asa new genus Further both species of Eotitanops share the dis-tinctive dental characteristics that serve to separate them fromPalaeosyops

Bown (1982) described five specimens from three differentlocalities in the Aycross Formation in the southeast AbsarokaRange Wyoming as Eotitanops borealis Four of these speci-mens have teeth that are smaller than typical E borealis andof a similar size to the same teeth of E minimus The fifthspecimen (USGS 1994) is represented by several fragmentary

teeth that are much larger than either species of Eotitanops andare here assigned to Palaeosyops fontinalis The known faunafrom the Aycross Formation in the Absaroka Range suggestseither a late Br1b or early Br2 age (Bown 1982) As has beendiscussed elsewhere (Bown 1979 1982 Gunnell 1997 Gun-nell and Gingerich 1996) the faunal samples derived from thisarea are from basin margin sediments along the southern rimof the Bighorn Basin Evidence suggests that basin marginspreserve faunal assemblages different from those of equivalentaged basin center sediments so that the presence of Eotitanopsminimus may represent another example of faunal anachronisma not unexpected occurrence in these marginal habitats (Bartelsand Gunnell 1997 Gunnell and Bartels 1997 1998)

Tooth measurements of Eotitanops minimus are as followsYPM-PU 16439 m2 149 104 m3 166 102 YPM16462 M1 137 173 UM 103216 P1 72 47 P2 97 68 P3 92 117 P4 115 136 M1 148 175 M2 168 187 M3 160 166 USGS 1992P3 98 108 USGS 1993M1 148 177

BRIDGERIAN BRONTOTHERE DENTAL EVOLUTION

The presence of bunoselenodont upper molars is the unitingcharacter state of Brontotheriidae In this dental pattern theparastyle paracone mesostyle metacone and to a lesser extentthe metastyle are united by a well developed continuous set ofcrests to form a W-shaped ectoloph (see Figs 2ndash3) The pro-tocone and hypocone are always lower more rounded andmore bulbous than the buccal cusps The buccal and lingualcusps are never connected by proto- or metalophs Paraconulesand metaconules are variably developed but tend to be eithersmall or absent

There are evolutionary changes in the bunoselenodont patternthrough time In the earliest recognized North American bron-tothere (the earlier occurring Lambdotherium may or may notrepresent a brontothere) Eotitanops borealis the W-shaped ec-toloph is fairly well developed but the parastyle and mesostyleare not buccally expanded to the degree seen in later speciesThrough the brontothere lineage the ectoloph becomes en-


hanced by buccal expansion of the parastyle and mesostyle andby greater development of the metastyle The parastyle and me-sostyle become more bulbous from Eotitanops borealis throughPalaeosyops robustus the latest occurring Palaeosyops speciesin the Bridgerian

Changes also occur in the upper premolar series from Eoti-tanops through P paludosus (Fig 6) There is a trend towardsmolarization of premolars although none of them ever becomemolariform P2 metacones become better expressed through theBridgerian brontothere lineage They are absent in Eotitanopsweakly developed or absent in Palaeosyops fontinalis and Plaevidens better developed but still lingual in P paludosus andstrongly developed in P robustus and P laticeps Similartrends occur in the development of P2 protocone shelves withearly species having low narrow and very distal shelves whilederived species have more bulbous wide and more centeredshelves Concomitant changes occur in P3ndash4 with primitivespecies lacking the incipient mesostyles strong buccal ridgesincipient W-shaped ectolophs developed parastyles and robustcentered protocones of more derived species

Lower teeth also undergo changes although most are moresubtle Lower molar lophids become better expressed in derivedspecies and the m3 hypoconulid becomes more elongate andmore complex The lower premolars become more robust withp3ndash4 having wider talonids that often form talonid basins witha lingual cuspule (especially p4) in more derived species

Along with morphological changes are changes in tooth size(and by inference body size) that can be traced through theBridgerian In some cases there are differences in all toothproportions (as between Eotitanops and Palaeosyops fontinal-is) but in others only certain teeth or tooth dimensions seemto exhibit size differentiation from one species to another Aswith many other studies of mammalian tooth size changethrough time (Gingerich 1974 1976 for example) brontoth-eres exhibit a great deal of overlap between closely related spe-cies from successive time intervals As such a case could bemade for recognizing a single chronospecies of Palaeosyopsthrough the Bridgerian but we feel that the tooth size changesalong with the morphological differences noted above are suf-ficient to justify the arrangement of species recognized in thispaper

Figures 7 through 10 document tooth size changes in theBridgerian radiation of Palaeosyops In the earliest BridgerianPalaeosyops fontinalis is represented by a few specimens andit can be seen that except for overlap in the size of some Plaevidens and P laticeps specimens P fontinalis is smallerthan all other Bridgerian Palaeosyops In the middle Bridgerianthere is evidence for two contemporaneous species the smallerP laevidens and the larger P paludosus These two species dooverlap in size but combined with the morphological evidencethere seems to be little doubt that two species of Palaeosyopsexisted in the middle Bridgerian The same can be said for thelater Bridgerian where P robustus and P laticeps co-occurTooth size evidence from lower molars also supports the inter-pretations made based on lower premolars

The same pattern exists in upper premolar and molar toothsize distributions The upper premolars especially serve to dis-tinguish P laevidens and P paludosus in the middle Bridgerianand P laticeps and P robustus in the later Bridgerian It is alsoclear from the distributions of upper molar size (Fig 11) thatP paludosus and P robustus are not very different with onlyM1 suggesting a slight trend from smaller to larger tooth sizein this presumed lineage However combined with the morpho-logical attributes discussed above we believe that P paludosusand P robustus are different species

Figure 11 shows the size distribution for upper molars ofEotitanops compared with Palaeosyops fontinalis P paludo-sus and P robustus from the Bridgerian Tooth size combined

with the morphology of the lower third molar indicate that twospecies of Eotitanops are present As can be seen both of thesespecies are clearly distinct in size from P fontinalis

Mader (1989) suggested that brontotheres do not exhibit sex-ual dimorphism in canine size but later (Mader 1998) recantedthat statement suggesting that there is evidence of canine di-morphism in brontotheres We concur with Maderrsquos more recentview The evidence is not completely convincing because sam-ple sizes are quite small but we believe that the distribution ofcanine sizes exhibited within certain Palaeosyops species doesindicate some degree of canine dimorphism Figure 12 showsthe distribution of upper canine size for P paludosus and lowercanine size for P robustus In both cases there is evidence tosuggest that two canine size groups exist

BRONTOTHERES AND BRIDGERIANBIOCHRONOLOGY

Stucky (1984) recognized the utility of using brontotheres asbiochronologic index taxa He proposed the Palaeosyops(Eotitanops of this paper) borealis Assemblage Zone for thesequence in the Wind River Basin denoted by the first appear-ance of E borealis Stucky equated this with Robinsonrsquos (1966)Gardnerbuttean subage of the Bridgerian Land Mammal Age asdocumented in the Huerfano Formation Stucky (1984) notedthe possibility that an additional biochronologic interval mightbe indicated in the Wind River Basin stratigraphically abovethe Eotitanops borealis Assemblage Zone based on the isolatedoccurrences of Palaeosyops huerfanensis (Palaeosyops fon-tinalis) Hyrachyus sp and a distinctly large individual of Es-thonyx acutidens (Gazin 1953)

Further examination of the distribution of earliest Bridgerianbrontotheres confirms Stuckyrsquos suspicion that two biochrons arerepresented within the Gardnerbuttean The first interval (ear-liest) best represented in the Wind River Basin is defined byStuckyrsquos Eotitanops borealis Assemblage Zone It is based onthe first appearance of E borealis as Stucky indicated Thesecond interval here informally named the rsquorsquo Palaeosyops fon-tinalis Assemblage Zonersquorsquo is based on the first appearances ofPalaeosyops fontinalis and Eotitanops minimus

A careful examination of the three most relevant sequences(Green River Basin Huerfano Park Wind River Basin) revealsthe following facts concerning the distribution of earliest Bridg-erian brontotheres Eotitanops borealis is the earliest occurringbrontothere At Huerfano E borealis lsquolsquo occurs a few hundredfeet above Lambdotheriumrsquorsquo (Robinson 196665) but does notover-lap in distribution with either Eotitanops minimus or Pa-laeosyops fontinalis Lambdotherium is the index taxon of theLostcabinian the last subage of the Wasatchian Land MammalAge (early Eocene) thus E borealis occurs later than the lastappearance of Lambdotherium at Huerfano Eotitanops minimusand Palaeosyops fontinalis both occur together in the upperHuerfano Formation

In the Wind River Basin Eotitanops borealis AssemblageZone only Eotitanops borealis is known to occur There is asingle locality in the Wind River Basin where E borealis andLambdotherium might co-occur (Stucky 1984) but there issome doubt as to the co-occurrence of these two taxa at Locality48FR78 As noted above Palaeosyops fontinalis is known bythree isolated teeth from a later interval in the Wind River Basin(Wallace 1980) but no other brontothere material has been de-scribed from these beds

At South Pass Palaeosyops fontinalis and Eotitanops mini-mus co-occur in the same interval Beds below the lowest oc-currence of P fontinalis have produced specimens of Lamb-dotherium

In the northern part of the Green River Basin West (1973)has reported the co-occurrence of Eotitanops borealis and


Lambdotherium from the upper Wasatch Formation (Westrsquoslsquolsquo arkosic facies of the New Fork Tonguersquorsquo ) East Fork Rim lo-cality There seems little doubt as to the taxonomic assignmentof the specimens referred to both Lambdotherium and Eotitan-ops although Eotitanops is represented by a single specimenThe two upper molars of Eotitanops have W-shaped ectolophswith a moderately developed mesostyle and parastyle They arein the size range of E borealis

As at South Pass this co-occurrence may represent anothercase of anachronistic taxa The East Fork Rim locality of West(1973) is located at the base of the western flank of the WindRiver Mountain Range and the faunal sample may well bedrawn from an upland or marginal basin community The oc-currence of anachronistic taxa is one of the indicators of non-basin-center faunal samples (Bartels and Gunnell 1997 Gun-nell and Bartels 1997) In this case the precocious appearanceof Eotitanops with Lambdotherium may be of less biochron-ologic significance than it might at first appear if marginal areasare important centers of speciation (Gunnell and Bartels 19971998)

It appears that the Gardnerbuttean sequence at Huerfano canbe subdivided into an early portion represented by the first ap-pearance of Eotitanops borealis and a later portion representedby the first appearance of Eotitanops minimus and Palaeosyopsfontinalis The earlier part of the Huerfano Gardnerbuttean se-quence is poorly represented but is likely to correlate with theWind River Basin Eotitanops borealis Assemblage Zone Thelater part of the Huerfano sequence correlates with the sequenceat South Pass here termed the lsquolsquo Palaeosyops fontinalis Assem-blage Zonersquorsquo

The lsquolsquo Palaeosyops fontinalis Assemblage Zonersquorsquo encompass-es the later part of the Gardnerbuttean as defined at HuerfanoPark It also encompasses the earliest part of the Bridgeriansequence in the southern Green River Basin Bridger A Wehave chosen to subdivide Bridgerian Biochronologic Zone Br1into an early interval (Br1a) representing the latest Gardner-buttean and a later interval representing the earliest Blacksfor-kian (Br1b) or Bridger A The mammalian faunas from thelatest Gardnerbuttean (Br1a) and Bridger A (Br1b) are similarbut there are differences that suggest that these two intervalsare not contemporaneous (Gunnell 1998)

Figure 13 summarizes these new interpretations The co-oc-currence of the ancestor-descendant taxa Eotitanops and Pa-laeosyops at South Pass and Huerfano (both sampled from up-land communities) is viewed as an example of anachronistictaxa (Bartels and Gunnell 1997 Gunnell and Bartels 1997)suggesting that these upland areas were important centers ofspeciation

ACKNOWLEDGMENTS

The authors thank all participants in the University of Mich-igan-Albion College field work program at South Pass andOpal In particular we thank Drs W S Bartels G H JunneJr C G Childress John-Paul Zonneveld and E R Miller fortheir help and advice For allowing us to examine specimens intheir care we thank Dr Malcolm C McKenna and Mr John PAlexander at the American Museum of Natural History (NewYork) Drs Mary Dawson and K Christopher Beard and MrAlan Tabrum at the Carnegie Museum of Natural History (Pitts-burgh) Dr Robert J Emry at the United States National Mu-seum (Washington DC) Dr Peter Sheehan at the MilwaukeePublic Museum (Milwaukee) and Dr Jacques A Gauthier andMs Mary Ann Turner at the Peabody Museum of Natural His-tory Yale University (New Haven) We thank Dr Robert MWest for advice during the early phases of field work Dr Wil-liam J Sanders prepared many of the specimens used in thisstudy Field work at South Pass and Opal has been generously

supported by the National Science Foundation the NationalGeographic Society the Wenner-Gren Foundation and the fieldwork program at the Museum of Paleontology University ofMichigan We thank the staff of the Bureau of Land Manage-ment at the Wyoming State Office in Casper Wyoming espe-cially Dr Laurie Bryant and the staff of the District BLM Of-fice in Rock Springs Wyoming for their assistance in makingfield work possible

LITERATURE CITED

Bartels W S and G F Gunnell 1997 Basin margin faunas and theorigin of North American Land Mammal Age faunal turnover Jour-nal of Vertebrate Paleontology 17 (3 suppl)31A

Bown T M 1979 New omomyid primates (Haplorhini Tarsiiformes)from middle Eocene rocks of west-central Hot Springs CountyWyoming Folia Primatologica 3148ndash73

1982 Geology paleontology and correlation of Eocene vol-caniclastic rocks southeast Absaroka Range Hot Springs CountyWyoming Geological Survey Professional Paper 1201-AA1ndashA75

K D Rose E L Simons and S L Wing 1994 Distributionand stratigraphic correlation of Upper Paleocene and Lower Eocenefossil mammal and plant localities of the Fort Union Willwoodand Tatman formations southern Bighorn Basin Wyoming UnitedStates Geological Survey Professional Paper 15401ndash103

Earle C 1891 Palaeosyops and allied genera Proceedings of the Acad-emy of Natural Sciences Philadelphia 43106ndash117

1892 A memoir upon the genus Palaeosyops Leidy and itsallies Journal of the Academy of Natural Sciences of Philadelphia9267ndash388

Gazin C L 1953 The Tillodontia An early Tertiary order of mam-mals Smithsonian Miscellaneous Collections 1211ndash110

Gingerich P D 1974 Size variability of the teeth in living mammalsand the diagnosis of closely related sympatric fossil species Jour-nal of Paleontology 48895ndash903

1976 Paleontology and phylogeny patterns of evolution at thespecies level in early Tertiary mammals American Journal of Sci-ence 2761ndash28

Gunnell G F 1997 Wasatchian-Bridgerian (Eocene) paleoecology ofthe western interior of North America changing paleoenvironmentsand taxonomic composition of omomyid (Tarsiiformes) primatesJournal of Human Evolution 32 105ndash132

1998 Mammalian fauna from the lower Bridger Formation(Bridger A early middle Eocene) of the southern Green River Ba-sin Wyoming Contributions from the Museum of PaleontologyUniversity of Michigan 3083ndash130

and W S Bartels 1997 Basin-margin mammalian assemblagesfrom the Wasatch Formation (Bridgerian) of the northeastern GreenRiver Basin WyomingmdashAnachronistic taxa and the origin of newgenera Journal of Vertebrate Paleontology 17 (3 suppl)51A

and 1998 Basin margins and morphologic divergencePaleontologic documentation of cladogenesis and evolutionary in-novation Journal of Vertebrate Paleontology 18 (3 suppl)47A

and P D Gingerich 1996 New hapalodectid Hapaloresteslovei (Mammalia Mesonychia) from the early middle Eocene ofnorthwestern Wyoming Contributions from the Museum of Pale-ontology University of Michigan 29413ndash418

Guthrie D A 1971 A titanothere (Mammalia Perissodactyla) from theearly Eocene of Wyoming Journal of Mammalogy 52474ndash475

Leidy J 1870 On fossils from Church Buttes Wyoming TerritoryProceedings of the Academy of Natural Sciences Philadelphia 22113ndash114

1872 On some new species of Mammalia from Wyoming Pro-ceedings of the Academy of Natural Sciences Philadelphia 24167ndash169

Mader B J 1989 The Brontotheriidae a systematic revision and pre-liminary phylogeny of North American genera pp 458ndash484 in DR Prothero and R M Schoch (eds) The Evolution of Perisso-dactyls Clarendon Oxford U K

1998 Brontotheriidae pp 525ndash536 in C M Janis K M Scottand L L Jacobs (eds) Evolution of Tertiary Mammals of NorthAmerica Cambridge University Press Cambridge U K

Marsh O C 1872 Preliminary description of new Tertiary mammalsPart I American Journal of Science 4122ndash128 erratum p 504


1890 Notice of new Tertiary Mammalia American Journal ofScience 39523ndash525

Matthew W D 1909 The Carnivora and Insectivora of the BridgerBasin Middle Eocene Memoirs of the American Museum of Nat-ural History 9291ndash567

Novacek M J I Ferrusquia-Villafranca J J Flynn A R Wyss andM Norell 1991 Wasatchian (Early Eocene) mammals and othervertebrates from Baja California Mexico The Lomas las Tetas deCabra fauna Bulletin of the American Museum of Natural History2081ndash88

Osborn H F 1908 New or little known titanotheres from the Eoceneand Oligocene Bulletin of the American Museum of Natural His-tory 24599ndash617

1929 The titanotheres of ancient Wyoming Dakota and Ne-braska Volumes I and II United States Geological Survey Mono-graph 551ndash953

Robinson P 1966 Fossil Mammalia of the Huerfano Formation Eo-cene of Colorado Bulletin Peabody Museum of Natural HistoryYale University 211ndash95

Stucky R K 1984 Revision of the Wind River faunas Early Eoceneof central Wyoming Part 5 Geology and biostratigraphy of theupper part of the Wind River Formation northeastern Wind RiverBasin Annals of the Carnegie Museum 53231ndash294

Wallace S M 1980 A revision of North American Early Eocene Bron-totheriidae (Mammalia Perissodactyla) MSc thesis University ofColorado Boulder 157 pp

West R M 1973 Geology and mammalian paleontology of the NewFork-Big Sandy area Sublette County Wyoming Fieldiana Geol-ogy 291ndash193

1990 Vertebrate paleontology of the Green River Basin Wy-oming 1840ndash1910 Earth Sciences History 945ndash56

Received 20 November 1998 accepted 15 November 1999

349

Journal of Vertebrate Paleontology 20(2)349ndash368 June 2000 2000 by the Society of Vertebrate Paleontology

BRONTOTHERIIDAE (PERISSODACTYLA) FROM THE LATE EARLY AND MIDDLE EOCENE(BRIDGERIAN) WASATCH AND BRIDGER FORMATIONS SOUTHERN GREEN RIVER BASIN

SOUTHWESTERN WYOMING

GREGG F GUNNELL1 and VICKI L YARBOROUGH2

1Museum of Paleontology University of Michigan Ann Arbor Michigan 48109-10792Yale Peabody Museum New Haven Connecticut 06520

ABSTRACTmdashThe perissodactyl family Brontotheriidae is represented by large numbers of specimens from latest earlyand middle Eocene sediments of the Western Interior of North America Species level taxonomy of brontotheres hasbeen confusing and the relationships of the earliest occurring species to those that occur later have not been welldocumented or understood Evidence based on new specimens from the earliest Bridgerian from the Green River Basinin particular from South Pass and Opal coupled with a reanalysis of previously existing specimens has led to thefollowing conclusions concerning the alpha taxonomy of Bridgerian North American brontotheres Four genera (Eoti-tanops Palaeosyops Mesatirhinus and Telmatherium) are recognizedEotitanops is represented by two speciesEborealis andE minimus andPalaeosyops by five speciesP paludosus P fontinalis P laevidens P robustus andP laticeps

A re-examination of the temporal distribution of brontotheres requires that the biochronologic framework of thelatest early to earliest middle Eocene be modified The earliest Bridgerian can be defined by the first appearance ofEotitanops borealis in the Wind River Basin and Wapiti Valley both in Wyoming and at Huerfano Park ColoradoThis interval has been termed theEotitanops borealis Assemblage Zone and is equivalent to the early GardnerbutteanBridgerian Biochronologic Zone Br0 The first appearances ofPalaeosyops fontinalis and Eotitanops minimus markthe onset of the second biochronologic interval of the Bridgerian Br1 here referred to informally as the rsquorsquoPalaeosyopsfontinalis Assemblage Zonersquorsquo This interval includes the late Gardnerbuttean (Br1a) and Bridger A (Br1b) Biochron-ologic Zones Br0 and Br1 are now included in the latest early Eocene while Br2 coincides with the beginning of themiddle Eocene

INTRODUCTION

Fossil mammals have been known from Eocene sediments inthe southern Green River Basin in southwestern Wyoming forover 150 years (Matthew 1909 West 1990) One of the earliestmammals described from this area wasPalaeosyops paludosus(Leidy 1870) a brontotheriid perissodactyl Since the initialdescription ofP paludosus no less than 11 additional generaand 28 species have been proposed for the Bridgerian radiationof brontotheres Revisions of various aspects of this radiationhave been attempted in the past (Earle 1891 1892 Wallace1980 Mader 1989 1998) but much confusion still remainsconcerning the species level taxonomy of brontotheresOsborn (1929) was the last authority to attempt a completespecies-level revision of all Eocene and Oligocene North Amer-ican brontotheres However due to his confusion over the na-ture of variability within and between species the nature offossil preservation and Osbornrsquos curious view of evolutionaryprocesses the resulting monograph created as many problemsas it solved In a sense the study of brontothere systematics iscursed by a wealth of information There are so many wellpreserved skulls and skeletal elements of Eocene brontotheresavailable that the task of sorting out their alpha taxonomy isdaunting requiring great amounts of time and travel

The results that follow are based on several years of inter-mittent travel to museums along with new specimens discov-ered over the past eight years of field work in the Green RiverBasin in southwestern Wyoming A joint University of Michi-gan-Albion College field project in the Wasatch and Bridgerformations has produced many new specimens of earliestBridgerian (Gardnerbuttean and Bridger A) brontotheres Thesespecimens along with some previously known material haveclarified the relationships among early bronotheres and form thebasis of this report

We have chosen to concentrate on dental evidence in this

study Much brontothere systematic work has been based oncranial morphology because of the availability of so manyskulls (Osborn 1929 Mader 1989) while tooth size and mor-phology have been relied upon less heavily Yet tooth size andmorphology have proven useful in sorting out species-level tax-onomy in many mammalian groups (Gingerich 1974 1976)and we feel that such is also the case for brontotheres We haveincluded cranial and postcranial features when they have ap-peared relevant but most of what follows is based on bron-tothere dental remains Most of the diagnostic features usefulfor sorting out brontothere taxonomy can be found in the upperdentition although a few features of the lower dentition haveproven useful The fact that most type specimens of previouslynamed Bridgerian brontotheres are either skulls or upper den-titions also makes careful study of upper teeth most profitable

Institutional AbbreviationsmdashAMNH American Museumof Natural History New YorkCM Carnegie Museum of Nat-ural History PittsburghMPM Milwaukee Public MuseumMilwaukee RAM Raymond M Alf Museum Webb SchoolClaremontUM University of Michigan Museum of Paleon-tology Ann Arbor USGS United States Geological SurveyDenver [specimens now housed at the USNM in WashingtonDC] USNM United States National Museum WashingtonDC YPM Yale Peabody Museum New HavenYPM-PUPrinceton University Yale Peabody Museum New Haven Allmeasurements are in millimeters (mm)

SYSTEMATIC PALEONTOLOGY

Order PERISSODACTYLA Owen 1848Suborder CERATOMORPHA Wood 1937Family BRONTOTHERIIDAE Marsh 1873

PALAEOSYOPS Leidy 1870

Limnohyus Marsh 1872124Limnohyops Marsh 1890525


















































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED


















































































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED










































































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED
































































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED



























































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




















































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




































c1 LW

211195

134162


88

6483

p1 LW

10076

056031

93ndash10571ndash78

44

5641

p2 LW

185104

106064


1414

5762

p3 LW

179118

112085


2020

6272

p4 LW

197142

103100


2121

5270

m1 LW

264180

157130


2020

6072

m2 LW

336226

183147


2323

5565

m3 L 455 286 401ndash514 24 63W 242 163 210ndash274 24 67

C1 LW

217205

285242


66

131118

P1 LW

13185

094079


88

7193

P2 LW

166169

076123


1111

4673

P3 LW

184210

123157


1111

6775

P4 LW

198247

131125


1818

6651

M1 LW

282298

175170


1717

6257

M2 LW

374374

190175


1515

5147

M3 LW

389392

228264


1515

5967



c1 LW

221207

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

173102

mdashmdash


22

mdashmdash

p3 LW

173111

mdashmdash


22

mdashmdash

p4 LW

199140

mdashmdash


22

mdashmdash

m1 LW

270185

mdashmdash


22

mdashmdash

m2 LW

295204

mdashmdash

mdashmdash

11

mdashmdash

m3 LW

400218

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

207181

mdashmdash


22

mdashmdash

P1 LW

13593

151110


44

112118

P2 LW

156143

104093


44

6765

P3 LW

171199

113100


66

6650

P4 LW

183240

154194


66

8481

M1 LW

276297

084223


55

3075

M2 LW

363366

255261


44

7071

M3 LW

365379

207203


55

5753




c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




































c1 LW

200182

138169


99

6993

p1 LW

11684

123079


66

10694

p2 LW

196110

166062


1313

8556

p3 LW

193125

112094


1919

5875

p4 LW

212153

127115


2424

6075

m1 LW

287193

153151


2626

5378

m2 LW

351236

156148


2020

4563

m3 LW

478248

257152


1919

5461

C1 LW

209195

162209


55

77107

P1 LW

13484

142013


44

10615

P2 LW

173181

146142


1212

8478

P3 LW

194222

090102


1212

4646

P4 LW

200257

123153


2323

6260

M1 LW

299327

141116


1818

4736

M2 LW

389396

179194


1313

4649

M3 LW

388413

430230


2222

11156












































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




























































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED






















































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED













































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




































































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED


























































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




































c1 LW

151156

mdashmdash

mdashmdash

11

mdashmdash

p1 LW

13585

mdashmdash

mdashmdash

11

mdashmdash

p2 LW

15989

mdashmdash

156ndash16289

22

mdashmdash

p3 LW

155100

mdashmdash


22

mdashmdash

p4 LW

155114

mdashmdash

mdashmdash

11

mdashmdash

m1 LW

216143

mdashmdash


33

mdashmdash

m2 LW

272180

mdashmdash


33

mdashmdash

m3 LW

380193

mdashmdash

mdashmdash

11

mdashmdash

C1 LW

152151

mdashmdash

mdashmdash

11

mdashmdash

P1 LW

14981

mdashmdash


33

mdashmdash

P2 LW

150150

mdashmdash


33

mdashmdash

P3 LW

157179

082053


55

5230

P4 LW

177216

111083


55

6338

M1 LW

255248

142102


66

5641

M2 LW

308288

mdashmdash


22

mdashmdash

M3 LW

344322

283230


66

8271





199152 Gunnell et al 1992273


































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED
























































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED





































c1 LW

211197

mdashmdash


33

mdashmdash

p2 LW

18199

077033


44

4333

p3 LW

167110

095034


44

5731

p4 LW

186129

102039


66

5530

m1 LW

244161

139050


66

5731

m2 LW

299199

080082


55

2741

m3 LW

410217

101137


55

2563

C1 LW

249210

mdashmdash


22

mdashmdash

P1 LW

115124

mdashmdash

mdashmdash

11

mdashmdash

P2 LW

162137

mdashmdash


33

mdashmdash

P3 LW

168180

067105


55

4058

P4 LW

183229

162144


88

8863

M1 LW

258276

192114


66

7541

M2 LW

351347

mdashmdash


33

mdashmdash

M3 LW

354373

375233


88

10662




p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED




































p2 LW

12165

210052

80ndash13760ndash72

66

17480

p3 LW

12170

099077

96ndash13358ndash82

1212

82110

p4 LW

12683

043029


1111

3435

m1 LW

161108

115088


1212

7281

m2 LW

193125

153102


1414

8082

m3 LW

231122

173103


1212

7584

C1 LW

131102

mdashmdash


22

mdashmdash

P2 LW

11096

mdashmdash


22

mdashmdash

P3 LW

121136

057109


55

4780

P4 LW

121152

126142


77

10494

M1 LW

188201

224194


88

11996

M2 LW

186210

mdashmdash


33

mdashmdash

M3 LW

192205

211204


88

110100






































ACKNOWLEDGMENTS



LITERATURE CITED
























































ACKNOWLEDGMENTS



LITERATURE CITED







































ACKNOWLEDGMENTS



LITERATURE CITED













































Documents

Brontotheriidae (Perissodactyla) from the late early and middle Eocene (Bridgerian), Wasatch and Bridger formations, southern Green River Basin, southwestern Wyoming