A Review of the Proteutheria 

and Insectivora of the 

Willwood Formation (lower Eocene), 

Bighorn Basin, Wyoming 

b 60 

r 

GEOLOGICAL SURVEY BULLETIN 1523 
A Review of the Proteutheria 

and Insectivora of the 

Willwood Formation (lower Eocene), 

Bighorn Basin, Wyoming 

By THOMAS M BOWN and DAVID SCHANKLER 

GEOLOGICAL SURVEY BULLETIN 152: 

The Wzllwood sample of proteutherzans and znsectwores 

zs the largest and most dwerse known for lower Eocene 

rocks of the world 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1982 
J 

UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Dzrector 

Library of Congress Catalogmg m Publication Data 

Bown, Thomas M 

A rev1ew of the Proteuthena and Insectlvora of the Willwood Formation (Lower Eocene), B1ghom Basm, Wyommg 

(Geolog•cal Survey Bulletm 1523) 

Bibliography p 73 

Supt ofDocs No I 19 3 1523 

I Proteuthena 2 Insecllvora, Foss1l Paleontology-Eocene 4 Paleontology-B1ghom R1ver 

water-shed, Wyo and Mont 

I Schankler, Dav1d M II T1tle III Senes 

QE75 B9 No 1523 [QE882 15] 557 3s 81-607068 [569' 12] AACR2 

For sale by the Branch of Dtstnbutton, U S Geologtcal Survey 

604 South Ptckett Street, Alexandna, VA 22304 
CONTENTS 

Absttact---------------------------------------------------

InttoductiOn -------------------------

History and purpose of mvestigation -----------------

Prehmmary faunal zonation of the Willwood Formation---------

Abbreviations -----------------------

Acknowledgments ----------------------

Systematic paleontology---------------------------

Class Mammalia------~--------------­

OrderProteuthena-----------------------

Fanuly Palaeoryctidae ------------------

FrunUyLeptictidae---------------------

Fanuly Pantolestidae ---------------------

Fanuly Apatemyidae --------------------

Order Insectivora, Suborder Ennaceomorpha --------------

FrunUyDonnaah!dae---------------------

Fwnlly Ennaceidae ---------------------

Order Insectivora, Suborder Soncomorpha --------------

Fwnlly Nyctitherudae ----------------------

Fanuly Geolabididae --------------------

Fanuly Aptemodontidae -------------------

Order Insectivora(?), mcertae sedis ----------------

Summary-----------------------------------------

References cited------------------------

Index---------------------------

ILLUSTRATIONS 

[Plates follow mdex] 

PLATE Duielphodus absarokae 

2 Duielphodus absarokae, Palaezctops bzcuspzs, Prodzacodon sp , 

andApatemys sp, cf A rodens 

3 Palaeosmopa vetemma, P lutreola, and P zncerta, sp nov 

4 Palaeosmopa vetemma, Apatemys chardzm, A kayz, A bellulus 

5 Macrocramon mtens. 

6 Macrocranwn mtens, Talpavozdes dartom, gen et sp nov , mdetermmate donnaalud, and Eo/estes szmpsom, gen nov 

7 Eo/estes szmpsom, gen nov , Entomolestes grangen, Plagwctenodon savagez, sp nov, and "Leptacodon" Jepsem 

8 Nyctzthenum velox, Centetodon patratus, sp nov , and Centetodon neashamz, sp nov 

9 Centetodon neashamz, sp nov, Paraptemodus antzquus, gen et 

sp nov , and msectivora(?) 

10 Palaeosmopa mcerta, sp nov 

III 

Page 

1 

2 

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3 

4 

4 

6 

6 

6 

6 

10 

20 

30 

41 

41 

52 

57 

57 

64 

67 

69 

71 

73 

77 
IV CONTENTS 

Page 

FIGURE 1 Stratigraplnc divisions of the Fort Uruon and Willwood Formations of the Bighorn Basm 5 

2 Stratigraplnc plots of loge (LXW)M2 m EoceneDulelphodus --- 8 

3 Stratigraplnc plots of loge (LXW)M1 m Eocene Dulelphodus --- 9 

4 Scatter chagram for M1 m some early Eocene leptictids 12 

5 Scatter chagram for M2 m some early Eocene leptictids 13 

6 Scatter chagram of tngorud Widths versus anteropostenor tooth 

lengths m M1 of some early Eocene leptictids 14 

7 Scatter chagram of tngorud Widths versus anteropostenor tooth 

lengths m M2 of some early Eocene leptictids 15 

8 Stratigraplnc plots of M2 m some early Eocene leptictids 17 

9 Scatter chagram of tngorud Widths versus anteropostenor tooth 

lengths of M1 m early Eocene Palaeosmopa 22 

10 Scatter chagram of tngorud widths versus anteropostenor tooth 

lengths of M2 m early Eocene Palaeosmopa 23 

11 Scatter chagram of talorud Widths versus anteropostenor tooth 

lengths of M1 m early Eocene Palaeosmopa 24 

12 Scatter chagram of talorud widths versus anteropostenor tooth 

lengths of M2 m early Eocene Palaeosmopa 25 

13 Histogram of loge (LXW)M1 m early Eocene Palaeosmopa 26 

14 Stratigraplnc plots of loge (LXW)M2 m early Eocene Palaeosmopa- 27 

15 Stratigraplnc plots of lo&! (LXM) M1 m early Eocene Palaeosmopa. - 28 

16 Histogram of M2 length of Bndgenan and Umtan sample of 

Apatemys 33 

17 Stratigraplnc plots of loge (LXW)M2 m late Paleocene through 

Bndgenan specrmens of Apatemys 36 

18 Chart showmg known stratigrapln~ ranges of proteuthenans and 

msectivores m the Willwood Formation 48 

TABLES 

Page 

TABLE 1 t values for parr-wise compansons of early Eocene samples of 

Prodzacodon and Palaezctops 18 

2 Cln-square analysis of the chstnbutwn of length measurements 

of M2 for the Bndgenan sample of Apatemys (ungrouped 

data) 33 

3 Cln-square analysis of the chstnbutwn of length measurements 

of M2 for the Bndgenan sample of Apatemys (grouped 

data) 34 

4-8 Measurements of teeth of 

4 Macrocranwn nztens 4 7 

5 Scenopagussp 50 

6 Talpavoules dartonz 53 

7 Plagwctenodon krausae 62 

8 W asatclnan Centetodon 66 
A REVIEW OF THE 

PROTEUTHERIA AND INSECTIVORA OF THE 

WILLWOOD FORMATION (LOWER EOCENE), 

BIGHORN BASIN, WYOMING 

By THOMAS M BOWN and DAVID SCHANKLER 

ABSTRACT 

The systematic paleontology of the Willwood Formation proteuthenans and msectivores IS revised, and new samples consistmg of approxunately 330 specunens are 

descnbed These are the largest samples of these anunals from lower Eocene rocks 

anywhere m the world, and therr occurrences mdlcate that they are of potential usefulness m b10stratigrapluc correlatiOns once they are known from more specunens and 

locahties 

The dldelphodontine palaeoryctid Dzdelphodus absarokae IS probably ancestral to 

the younger and smaller D oltulens The leptictids Produzcodon and Polaezctops are 

more closely related to each other than was recently suggested by M J Novacek Two 

Willwood specunens show crossmg characters between these genera Polaezctops 

matthewz Novacek IS probably conspecific w1th P multzcuspzs, and the type of 

Polaezctops pmeyenszs IS removed from synonymy with Produzcodon tauncmerez and 

IS placed m Polaezctops bzcuspzs Statistical studles mdlcate that there were five early 

Eocene species of Polaeosmopa. P vetemma, P dzdelphozdes, P lutreola, P mcerta, 

sp nov , and a large, undescnbed form from the Lost Cabm Member of the Wmd 

River Formation P lutreola IS restncted to Graybulhan faunas, and Student's t tests 

show that P dzdelphozdes dlffers statistically from P vetemma R M West's review 

of apatemyids IS cnticiZed from several viewpomts, four species of Apatemys are 

recogmzed m the Willwood fauna A chardmz, A bellulus, A kayz, and A sp , cf 

A rodens 

Earher concepts of the Adapisoncidae are revised Adapzsorex IS probably an 

Aphel,scus-hke condylarth, and the Dormaalunae IS elevated to family status to 

accomodate most other taxa earher grouped m the Adapisoncidae Dormaolzus and 

Macrocramon appear to be closely related, and both share slmllanties with late 

Paleocene Lztolestes Mckennathenum IS not a dormaahld, rather, both It and "Dzacodon" mmutus probably belong m Adunator Diagnostic characters of the Nyctitherndae are dlscussed m the hght of the recent review of tlus group by L B Knshtalka, both Plagwctenodon and Plagwctenozdes are probably nyctithernds 

New samples of msectivores mclude the earhest records of Centetodon and the 

Geolabidldae (two new species are descnbed), and the Apternodontidae (a new genus 

and species) Other new msectivore taxa mclude a Tolpavus-hke dormaailld, a Lezpsanolestes-hke ennaceid, and new species of Plagwctenodon and Scenopagus New 

specunens of Pontzfactor (Nyctitherndae) and "Leptacodon" ;epsem (Ennaceidae) 

occur m the Willwood fauna, "L " ;epsem IS an ennaceid, most closely related to 

Bndgenan Entomolestes grangen 

1 
2 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

INTRODUCTION 

HISTORY AND PURPOSE OF INVESTIGATION 

Cope (1881) frrst described a specimen of a proteuthenan from the 

Willwood Formation of the Bighorn Basin of northwest Wyoming 

(Deltathenum absarokae (Didelphodus Cope, 1882; Matthew, 1918, 

p. 579)). Since that time, at least 500 additional specimens have been 

recovered from these productive rocks. Matthew (1901, 1918) and 

Jepsen (1930a) described the best Willwood material in the American 

Museum and Princeton University collections, respectively, and a 

few additional Willwood specimens were recorded by West (1973), 

Krishtalka (1976a, b), and Novacek (1977). Until recently, however, 

the vast majonty of these fossils were undescribed. The largest single 

collection (about 215 specimens from the Sand Creek facies) exists in 

the University of Wyoming Geological Museum (No Water fauna) 

Most of these were discussed by Bown (1979), who named two new 

genera (Plagzoctenodon and Plagioctenmdes) and one new species 

(Leipsanolestes slmpsoni) of insectivores. The No Water fauna was, 

m addition to the Four Mile fauna of northwestern Colorado (McKenna, 1960a), only the second comprehensive record of early WasatchIan insectivores and proteutherians 

Another large sample (about 180 specimens) In the Yale Peabody 

Museum was collected by Yale field parties under the direction of 

E. L Simons (during 1961-65, 1968-72, 1974, 1975), and David 

Schankler (during 1976, 1977) This collection was obtained from 

numerous localities throughout the lower seven-eighths (660 m) of the 

Willwood Formation and contains both early (Graybullian age) and 

rmddle (Lysitian age) W asatcruan insectivores and proteuthenans 

These mammals have thus far not been found in Willwood rocks that 

yield Lambdothenum (Lostcabiruan age). 

This paper contains a documentation of the Willwood Proteuthena 

and Insectivora in the Yale Peabody Museum collection, a revisiOn of 

some of the forms in the No Water fauna, and discussions of possible 

phylogenetic mterpretations of these and related forms. The Willwood record of these animals is an impressive one and serves adequately to bndge the gap between known late Paleocene and 

Clarkforklan forms and those of the late early Eocene and rmddle 

Eocene. The Willwood sample compnses at least 18 genera, which are 

contained m at least 30 species, of which three new genera and seven 

new species are described here. It is the most diverse record of the 

Proteuthena and Insectivora in the North American Paleocene or 

Eocene. 
INTRODUCTION 3 

PRELIMINARY FAUNAL ZONATION OF THE WILLWOOD FORMATION 

A comprehensive picture of the vertebrate faunal zonation of the 

Willwood Formation is still In progress, however, several recent 

studies have already contributed to a clearer understanding of Willwood biostratigraphy (for example, Neasham and Vondra, 1972; 

Gingerich, 1974a, 1976, 1977; Gingerich and Rose, 1977, Gingerich 

and Simons, 1977; Rose, 1978, Bown, 1975, 1979) Schankler (1980) 

has related many of the 400-odd Yale Willwood localities in the central Bighorn Basin to a measured stratigraphic sectiOn Bown (1979, 

1980) has done the same for approximately 250 sites in the southern 

and southeastern Bighorn Basin, and ongoing studies of P. D 

Gingerich and K. D Rose at the Uruversity of Michigan have Incorporated data from another 250-odd localities In the Clark's Fork 

Basin Studies of Willwood mammals at each of these sites are in 

various stages of preparation, however, enough is now known to offer 

a prehmmary picture of the biOstratigraphic relationships of Willwood proteutherians and insectivores 

Traditionally, the Willwood Formation has been separated into 

three poorly defined uruts: the "Gray Bull Member" (faunal term: 

"Graybulhan"), a taxon-range zone typified by Homogalax protapznnus; the "Lysite equivalent" (faunal term: "Lysitian"), an as 

yet unsubstantiated faunal assemblage zone, presently characterized 

only by the range of overlap of the helaletid Heptodon and the adapid 

Pelycodus jarrovn, and by the absence of Homogalax, and the "Lost 

Cabm equivalent" (faunal term· "Lostcabmian"), which, in the Willwood Formation, IS presently distinguished only by the presence of 

the palaeothere Lambdothenum (Wood and others, 1941; Van 

Houten, 1945). Wood and others (1941) were apparently unaware that 

these divisions in the Bighorn Basm have no rock-stratigraphic 

meaning The designatiOn of "beds", "Member", or "equivalent" for 

the Gray Bull, Lysite, and Lost Cabin uruts m that basin is, therefore, inappropriate because they cannot be distinguished without an 

examination of their contained faunas. Indeed, the faunal distinctiveness of the lithologically distinguished Lysite and Lost Cabin Members of the Wmd River Formation is poorly understood in their type 

areas m spite of several recent studies, and Homogalax, the supposed 

index fossil of the Gray Bull, occurs in positively younger rocks in 

southern Wyoming and in association with Heptodon in at least 

twenty Willwood faunules. 

In this paper, the following faunal-stratigraphic divisions are 

recognized for Willwood rocks and faunas and have been superimposed on existing established nomenclature to avoid confusion 
4 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

that might arise if a new terminology were established without 

faunal documentation at this time These divisions, which are documented in unpubhshed data of Schankler and Bown, facilitate discussion of the relative faunal ages of the Willwood proteuthenans and insectivores, are based on unpublished faunal studies of more than 600 

Willwood localities, and will be revised as subsequent investigations 

warrant. Measurements (in meters) are from the base of the Willwood 

Formation in the Elk Creek section (Schankler, 1980), central 

Bighorn Basin. 

Lost Cabin biostratigraphic zone 

660-780 m, Lostcabinian fauna 

Lysite biostratigraphic zone: 530-660 m, 

Lysitian fauna 

Upper Gray Bull biostratigraphic 

zone: 380-530 m, late Graybullian fauna 

Middle Gray Bull biostratigraphic 

zone· 200-380 m, middle Graybullian 

fauna 

Lower Gray Bull biostratigraphic zone: 

0-200 m, early Graybullian fauna. 

The stratigraphic and biostratigraphic relations of these umts to 

rock units in the Bighorn Basin are depicted in figure 1 

ABBREVIATIONS 

Abbreviations used in this report are as follows: AMNH, American 

Museum of Natural History (New York); CM, Carnegie Museum 

(Pittsburgh); MCZ, Museum of Comparative Zoology, Harvard 

University (Cambridge); PU, Princeton University Museum 

(Princeton); TTU-P, Texas Tech University Museum (Lubbock); 

UCMP, University of California Museum of Paleontology (Berkeley); 

UMMP, University of Michigan Museum of Paleontology (Ann Arbor); USGSD, U.S. Geological Survey (Denver); UW, The Geological 

Museum, The Umversity of Wyoming (Laramie); YPM, Peabody 

Museum, Yale University (New Haven); n, sample size. 

ACKNOWLEDGMENTS 

We are grateful to J. A. Lillegraven (UW), D E. Russell (lnstitut 

de Paleontologie, Paris), and C. A. Repenmng (U.S. Geological 

Survey) for their comments on the manuscript; to David Archibald 
INTRODUCTION 5 

TERTIARY SYSTEM 

Paleocene Senes I Eocene Senes 

FortUmon / 

Formation W1llwood Formation 

Clarkfork1an provmc1al age I Wasatchian provmc1al age 

/ / 

/ 

// 

0 

Lower Gray Bull M1ddle Gray Bull Upper Gray Bull Lys1te b10-

b1ostrat1graph1c b1ostrat1graph1c b1ostrat1graph1c strat1graph1c 

zone zone zone zone 

Early Graybulllan M1ddle Graybulllan Late Graybulllan Lys1t1an 

fa una and age fauna and age fauna and age fauna and age 

100 200 300 400 500 600 

D1stance m meters above W1llwood FormationFort Umon contact m Elk Creek sect1on 

Lost Cabm 

b10strat1graph1c 

zone 

Lostcabm1an 

fauna and age 

700 

FIGURE 1 -RelatiOns of rock-stratJ.grapluc, tune-stratJ.grapluc, and biOstratigrapluc 

umts for the Fort Umon and Willwood Formations of the Bighorn Basm 

(YPM) and K D. Rose (Johns Hopkins University) for discussion, 

and toM. C. McKenna (AMNH), J. A. Lillegraven (UW), C C Black 

and M. R. Dawson (CM), P. D. Gingerich (UMMP), D. E. Savage 

(UCMP), Chuck Schaff (MCZ), J. H. Ostrom and M.A. Turner (YPM), 

Donald Baird (PU), Eileen Johnson (TTU-P), and D. E. Russell for 

the generous loan of specimens and casts in their care. The section on 

Proteuthena is largely the work of Schankler, and the section on Insectivora is largely the work of Bown; however, both authors bear 

responsibility for the paper as a whole. 

Robert O'Donnell (USGSD) skillfully prepared several of the specimens. Bown completed his research for this study while he was aNational Research Council postdoctoral fellow with the U.S. Geological 

Survey and thanks N J. Silberling, Robert Kosanke, and G. E. Lewis 

for access to Geological Survey facilities under their supervision 

Schankler was assisted by a Sigma Xi research grant and by N at10nal 

Science Foundation Doctoral Dissertation Improvement Grant 

DEB-76-22769. 

Most of the specimens described in this report were obtained 
6 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

through the support of grants from the John T. Doneghy Fund (Yale 

University) and Boise Fund (Oxford Uruversity) to E. L. Simons, and 

National Science Foundation Grant GA-35754 to P. 0. McGrew 

(UW). 

SYSTEMATIC PALEONTOLOGY 

Class MAMMALIA 

Order PROTEUTHERIA 

F&mlly PALAEORYCTIDAE 

Subf811llly PALAEORYCTINAE 

Palaeoryctes sp 

Referred spectmens -USGSD 1661, 2151, 3711. 

cf Panryctes sp 

Referred specimen - UW 7028. 

Discussion.-SIX specimens of palaeoryctmes are known from the 

Willwood Formation. In addition to the four teeth listed here, two 

superb skulls exist in the UMMP collections Willwood palaeoryctine 

materials are under study by M. C McKenna at the American Museum of Natural History. The Uruversity of Wyormng specimen of cf. 

Pararyctes was recovered from Yale locality 363 at the 190-m level of 

the Willwood Formation m the Elk Creek facies, the USGS materials 

are from Yale locality 363 (USGSD 2151), UW locahty V-73037 

(USGSD 3711), and UW locality V-73055 (USGSD 1661). The Uruversity of Wyoming localities are at the 34-m and 119-m levels of the 

Sand Creek facies of the Willwood Formation, respectively. 

Subf8Dllly DIDELPHODONTINAE 

Dulelphodus absarokae (Cope, 1881) 

Plate 1, plate 2, figures 1, 2, 4 

Referred spectmens.-YPM 17289a, 17297, 17305 (including 23730 

and 23731), 18971 (pl 2, figs 1, 4), 23071, 23100, 23105, 23120, 

23724,23725,23726,23729,23732,23733,25361 (pl 2,fig.2),25499, 

27802, 27877, 28208, 28221, 29285, 30591, 30608, 37184, 37186, 

USGSD 303 (pl. 1). 

Dtscusswn.-The type specimen of Dtdelphodus absarokae is from 

the Willwood Formation, but its exact locality and stratigraphic position are unknown. All the Yale specimens of Dtdelphodus are as-
SYSTEMATIC PALEONTOLOGY 7 

signed to this species, even though the Lysitian specimens are mtermediate in size between the types of D. absarokae and D alndens 

This intermediacy of size was also recorded by Guthne (1967a) for the 

Lysite Member (Wmd River Formation) sample, from the Wind River 

Basin. 

In the central Bighorn Basin, D absarokae is known from the lower 

Gray Bull to the upper part of the Lysite zones. Its absence from the 

Lost Cabin zone is probably due to relatively poor samples from these 

localities, as it is a rare species even in the faunally better represented 

lower horizons. The few specimens that are available tend to show a 

decrease in tooth size up section. 

The Willwood sample has been combined with other early and 

middle Eocene samples m a time versus size plot in figures 2 and 3. 

The measure of size IS adapted from that in Gingerich (1976). As can 

be seen from the figures, D absarokae and D alndens are clearly 

separated in size only at the end points of the temporal range This 

relationship was earlier observed by Van V alen (1966, p. 32) and 

Guthrie (1967a, p. 13). A specimen from the Lost Cabin Member of 

the Wind River Formation (MCZ 3461), assigned by Van Valen (1966) 

to D. alndens, is m the rmddle of the size range of the Lysite zone 

specimens found in the Willwood Formation and the Almagre faunal 

sample in the San Jose Formation of New Mexico. The latter sample, 

presumably of Lostcabinian age, was assigned by Van Valen (1966) 

to D absarokae and is interesting in that it contmns an Individual 

that is almost as large as the largest of the Graybullian specimens 

Van Valen's argument that D alndens is not an anagenetic descendant of D absarokae was based largely on the existence of both species 

in a smgle fauna, that of the Lost Cabin Member of the Wmd River 

Formation The presence of D absarokae in this fauna was indicated 

by a single specimen (US National Museum 18433), whose correct 

assignment has been properly questioned by Guthrie (1971). Whether 

it is a specimen of Dldelphodus or not, It is certmnly not separable 

from other Lostcabrman specimens of D alndens on the basis of size, 

which, according to Van Valen (1966), IS the only valid criterion for 

distinguishing lower molars of the two species. The differences in 

morphology are of degree rather than kind. Although we do not here 

recommend synonymy of the two species of Dldelphodus, we do 

observe that the two species are not very discrete entities and that D 

alndens, in all hkelihood, is a descendant of a population of D 

absarokae 

The Willwood sample adds virtually nothing to Van Valen's (1966) 

treatment of the morphology of the genus other than to record a few 

variatiOns. In the two Lysite zone specimens where P 1 IS known, it IS 

two rooted, with the an tenor root displaced labially. In the only other 
8 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

Ci> • () C> 

"'0 

~ 

• c 

700 

(/) • a: • w 

1-

w 

~ 

z 

-.. z 500 • ~ • 

0 

i= 

U5 

0 I a.. 

u 

J: 300 a.. e 

<( 

a: 

(.!) 

i= 

<( 

a: 

1- • (/) 

100 

1 7 1 9 2 1 23 25 

loge (LENGTH x BREADTH) OF M2 

EXPLANATION 

• YPM and UMMP central B1ghorn Basm specimens 

• AMNH Almagre spec1mens 

e AMNH central B1ghorn Basm spec1mens 

c USNM Lost Cabm Member spec1mens (referred to 

PaeneproiJmnocyon am1ssadomus by Guthne, 

1967b) 

• MCZ 3461, Lost Cabm Member 

• YPM 13516, type of D1de/phodus alt1dens 

() AMNH Bndgenan spec1mens 

FIGURE 2 -Stratigraphic plots of M2 m Dulelphodus specrmens from vanous 

Eocene locahties Measurements of stratigraphic position are from the base of the 

Willwood Formation Plots m the area labeled "Bndger" are grouped 
800 

CJ) 

a: 

w 

...... 

w 

~ 

z 

-~ 600 

z 

0 

E 

CJ) 

0 

a.. 

~ 

5:: 400 

<( 

a: 

(!) 

i= 

<( 

a: 

...... 

CJ) 

200 

1 7 

ORDER PROTEUTHERIA 

• • 

• • • 

• 

• • 

• ·~ ~ 

• 

~ 

A 

1 9 2 1 2 3 

loge (LENGTH x BREADTH) OF M1 

EXPLANATION 

• YPM and UMMP central B1ghorn Basm spec1mens 

e AMNH Almagre spec1mens 

A USNM central B1ghorn Basm spec1mens 

0 UCMP Four M1le fauna spec1mens 

~ AMNH central B1ghorn Basm spec1mens 

-Q- AMNH Cathedral Bluffs Member spec1men 

• MCZ 3461, Lost Cabm Member 

25 

FIGURE 3 -Stratigraphic plots of M. m Dulelphodus specrmens from vanous 

Eocene localities Ordinate IS stratigraphic position (meter levels are for 

the Willwood Formation, other plots approXIIDate) 

9 

specimen that preserves this tooth (YPM 23729 from the upper Gray 

Bull zone), it appears to be single rooted. In the four specimens that 

preserve P 4, the development of the metaconid varies from very weak 

to very strong and in some specimens it IS almost equal to the protoconid in size. There is, however, no correlation of -this character 
10 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

with stratigraphic position. The pattern is as follows: lower Gray 

Bull zone, metaconid moderate; middle Gray Bull zone, metaconid 

very strong; upper Gray Bull zone, metaconid weak, Lysite zone, 

metaconid very weak. 

Upper teeth of Dzdelphodus are very rare, and the only vanatwn 

observed in the sample at hand is the absence of a parastyle on the 

P4 's of two middle Gray Bull zone specimens and the presence of a 

strong parastyle on one specimen from the upper Gray Bull zone 

Famlly LEPI'ICTIDAE 

Subfamlly Leptictinae 

Novacek (1977) listed the followmg as shared denved characters of 

the leptlctld Palaezctops that distinguished it from the more generalized Produreodon: 

1. P5

' s (traditionally P4

) and upper molars 

are more bunodont, being more anteroposteriorly elongate and transversely 

compressed, with lower, more bulbous 

paracones, metacones, and protocones. 

2. Parastylar spurs on M2- 3 are not promi 

nent, and ectoflexi are relatively 

shallow. 

3 Hypocones are well developed, being 

more than half the height of the 

protocones. 

4. Conules are situated labially at the base 

of the paracone and metacone. 

5 Molar trigonids are not greatly elevated. 

6. P 5 paraconids are well developed. 

7. The paracone on P4 is moderately to 

greatly enlarged 

With respect to these characters, the present reVIew of early Eocene 

leptlctids m the YPM collection and comparison of these specimens 

with type specimens and casts of the types and other specimens of 

Prodiacodon tauncznerez, Palaeictops bzcuspis, and Palaezctops multicuspzs leads to the following observations: 

1. The number of upper dentitions of either Produreodon or Palaezctops Is very small, and generalizations about the characteristics 

of the upper teeth of these taxa must be made with caution. 

Scatter diagrams (figs. 4, 5) of the length to width of the upper 

molars indicate that teeth m the type of Palaezctops bzcuspzs are 

only slightly less transversely broad than are those of the type 
ORDER PROTEUTHERIA 11 

or referred specimens of Prodwcodon tauncmerez, and that the 

type of Palaezctops matthewz has upper molars that are wider 

than in either of the latter Upper molars of Paleocene Prodzacodon are more transverse than any early Eocene species of 

Palaeictops. 

2. The ectoflexi of the type of Prodwcodon tauncznerez are deeper 

than in the type of Palaecztops bzcuspzs; however, a referred 

specimen of P bzcuspzs figured by Guthne (1971) has an M2 ectoflexus that IS intermediately deep between these types. 

3. A specimen from the Lysite biostratigraphic zone of the Willwood 

Formation combines several characters of both genera and is 

typified by its large tooth size in conJunction with transversely 

broad upper molars, twinned paraconules, and a large hypocone 

(nearly two-thirds the height of the protocone). 

4. The conules of the few specrmens of upper molars are situated 

more lingually in Prodwcodon tauncznerez, as observed by Novacek (1977). 

5 The type specimens of the three descnbed species of Palaezctops 

from the early Eocene are very worn, and it is difficult to accurately Judge the relative degree of elevation of the molar tngonids Guthrie's (1971) referred specimen of P. bicuspzs does 

not appear to have trigoruds that are relatively less elevated 

than in most specimens of Prodiacodon tauricznerez. 

6. The P 5 (traditionally P 4) paracorud is well developed In the type 

and referred specimens of Prodwcodon tauncznerez. The paracorud appears to be better developed In Palaezctops species 

because of the larger tooth size and because the anterior portion 

of the trigonid is slightly more elongate (relates more to P bzcuspzs than to other species) This feature also gives the tooth a 

relatively less elevated appearance with respect to Prodwcodon 

The conclusiOn reached from these observations is that the genus 

Palaezctops, although probably constitutmg a natural group, is not 

nearly so dentally distmct from early Eocene Prodiacodon as Novacek (1977) believed. In particular, Prodwcodon tauncmerez of the 

early Eocene seems to be at least as closely related fu Palaezctops 

bzcuspzs, in an ancestral-descendant way, as it is to Its probable 

ancestral and collateral cogeners of the Paleocene. Detailed understandmg of this lmeage, however, is hampered by the paucity of specimens from the critical upper Gray Bull and Lysite zones. It seems 

hkely that early Wasatchian P tauncznerez, persistmg Into Lysitian 

time, also may have given rise to a second lineage. This line led to 

Palaezctops 

Novacek's (1977) new species Palaezctops matthewz is probably 

conspecific with Palaeictops multicuspzs As Novacek noted, the two 
12 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

48 

en 

a: 

w 

I-

~ 44 

:::::; 

= 

~ 

~ 

::i 

IQ 40 

~ 

w 

en 

a: 

w 

> 

en 

z 

~ 3 6 

Ia: 

0 

a: 

w 

Iz 

<( 

32 

0 

• e 

0 

0 .() 

• • 

23 25 27 29 31 33 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS• 

EXPLANATION 

• Willwood Format1on Prod1acodon tauncmere1 

() Type of Prod1acodon tauncmere1 

0 W1llwood Format1on Palae1ctops b!cusp1s 

0 Prod1acodon puercens1s 

e Type of Pa/ae1ctops matthew! 

A Prod1acodon cnstu/um 

e Type of Palaelctops biSCUSPIS 

FIGURE 4 -Scatter diagram of measurements for M1 m some early Eocene leptictids 

species are closely similar in morphology, differing only shghtly in 

the construction of P 2• The 8-percent size difference, as judged by size 

variation in many living and fossil species of mammals, is not considered by us to be Significant. Both P "matthewz" and P 

multicuspzs fall within the size range for P bzcuspis (figs 6, 7), and a 
46 

en 

a: 

w 

1-

w 

~ 

:J 

:::! 

~ 42 

~ 

:i 

1-

0 

~ 

w 

en 

ffi 3 8 

> en 

z 

< 

a: 

1-

a: 

0 

a: 

w 

~ 34 

< 

ORDER PROTEUTHERIA 13 

0 

() 

e 

22 24 26 28 30 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e W1llwood Formation Prod1acodon tauncmere1 

() Type of Prod1acodon tauncmere1 

0 W1llwood Format1on Palae1ctops b1cusp1s 

• Type of Pa/ae1ctops matthew! 

e Type of Palaelctops biCUSPJS 

FIGURE 5 -Scatter diagram for measurements of M2 m some early Eocene leptictids 

better understanding of the variation and significance of the supernumerary cusps on the anterior premolars rmght eventually result in 

their inclusion in that species. 

Prodiacodon tauricinerei (Jepsen, 1930a) 

Referred specimens.-YPM 23073, 23081, 23090, 23093, 23115, 

23119, 27212, 30521, 30556, 30565, 30571, 30601, 30606, 30619, 

30621, 30633, 30638, 30640, 30650, 32098, 32104, 34256, 34259, 
14 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

2 2 24 26 28 30 32 34 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e Prod1acodon tauncmere1 (Gray Bull zone, Willwood Format1on) 

e Type of Prod1acodon tauncmere1 (measurements from Novacek, 1977) 

~ Mean of W1llwood Format1on Prod1acodon tauncmere1 

~ Prod1acodon sp , YPM locality 290 

() Pa/ae1ctops b1cusp1S (Lys1te zone, Willwood Format1on) 

0 Mean of W1llwood Formation Palae1ctops b1cusp1s 

• Type of Pa/ae1ctops matthew1 (measurements from Novacek, 1977) 

0 Range of Lys1te Member (Wmd R1ver Formation) Palae1ctops pmeyens1s 

(measurements from Guthne, 1967a) 

o Mean of Lys1te Member (Wmd R1ver Format1on) Palae1ctops pmeyens1s 

(from Guthne, 1967a) 

¢ Range of Lost Cabm Member Pa/ae1ctops b1cusp1s (from Guthne, 1971) 

& Mean of Lost Cabm Member Palae1ctops b1cusp1s (from Guthne, 1971) 

1:1. Type of Palae1ctops multlcusp1s 

e Type of Palaelctops biCUSplS 

FIGURE 6 -Scatter diagram of measurements for M1 of some early Eocene leptlctlds 
ORDERPROTEUTHERIA 15 

26 ¢ 

A 

() A 

() 0 

cn24 () 

• a: () w 

Iw 0() • ~ ()+ () () 

~ 2 2 () 

~ • c 

~ • () () 

:i ~ 

b 2 0 ~ • 0 ¢ 

• § • 

_Q •• ~ .. • z • 0 

g 1 8 

a: •• • 

I1 6 

22 24 26 28 30 32 34 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e Prodtacodon taurtcmeret (Gray Bull zone, W1llwood Format1on) 

e Type of Prodtacodon taurtcmeret (measurements from Novacek, 1977) 

0 Prodtacodon tauncmeret (Lys1te zone, W1llwood Format1on) 

~ Mean of W1llwood Format1on Prodtacodon tauncmeret 

~ Prodtacodon sp, YPM locality 290 

() Palaetctops btcuspts (Lys1te zone, W1llwood Format1on) 

• Type of Pa/aetctops pmeyensts (measurements from Novacek, 1977) 

0 Mean of W1llwood Format1on Palaetctops btcuspts 

• Type of Palaetctops matthewt (measurements from Novacek, 1977) 

0 Range of Lys1te Member (Wmd R1ver Formation) Palaetctops pmeyensts 

(measurements from Guthrie, 1967a) 

c Mean of Lys1te Member (Wmd R1ver Formation) Pa/aetctops pmeyensts 

(from Guthrie, 1967a) 

¢ Range of Lost Cabm Member Palaetctops btcuspts (from Guthrie, 1971) 

A Mean of Lost Cabm Member Palaetctops btcuspts (from Guthrie, 1971) 

A Type of Palaetctops multtcuspts 

FIGURE 7 -Scatter wagram of measurements of M2 of some early Eocene lepbctids 
16 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

35146, 35151, 35160, 37238, 37239, 37240, 37243, 37247, UMMP 

64482, MCZ 18958, USGSD 2566, possibly YPM 27931 

Discussion.-Prodzacodon tauncinerez is the second most common 

species of a proteutherian or an insectivore m the Gray Bull biostratigraphic zone of the Bighorn Basin. The type specimen (PU 13104) 

was recovered from a shale "pocket" south of Dorsey Creek in the 

central part of the Bighorn Basin (Jepsen, 1930a), and this locality is 

thought to be near YPM locality 295, in the middle Gray Bull zone. 

In the Bighorn Basin Lysite zone, P tauricznerez is represented by 

only one or possibly two specimens For the most part, it appears to 

be replaced in these beds by the larger and more abundant leptictid 

Palaeictops bicuspzs. 

Outside the Bighorn Basin, Prodzacodon tauncinerez is known from 

the Powder River local fauna, from rocks of early Wasatchian age at 

Bitter Creek, Wyo., and from the Four Mile fauna of northwestern 

Colorado. Meas-qrements given by Novacek for AMNH 80023 from 

the Four Mile fauna are either typographical errors or indicate a species other than P. tauncinerei. In this specimen, the talonid width of 

M1 and the trigonid width of M2 are anomalously small and large, 

respectively. 

Novacek (1977) synonymized the type of Palaezctops pzneyensis 

with Prodzacodon tauncznerei, notmg the larger size of the former but 

a general similarity of morphology. As discussed previously, the differences between Prodiacodon and Palaezctops are not great, and 

what differences do exist (for example, placement of conules on the 

upper molars and elongation of the P 5 trigonid) cannot be observed m 

the type of Palaezctops pzneyenszs because they are not preserved m 

that specimen. A scatter diagram of length versus trigonid width of 

M2 for early Eocene leptictids (fig. 7) shows that the type of P. pzneyenszs from the La Barge fauna (Lostcabinian age) is most closely 

associated in thls character with specimens from the Lysite Member 

of the Wind River Formation that were referred to P pineyenszs by 

Guthrie (1967a), and with specimens from the Lysite zone of the Willwood Formation. The two Lysite zone populations are significantly 

different from the largely Gray Bull sample of Prodzacodon tauncinerez in both length and width (Lysite zone: length t=7.92, n=24; 

p=0.0001, width t=8.12, n=24, p=0.0001; Lysite Member, Wind 

River Formation: length t=814, n=20, p=O 0001, width t=4.92, 

n=20; p=O 0001; see table 1). Similar results were obtained from 

analyses of the dimensions of M1, except for the length comparisons 

of specimens from the Lysite Member of the Wmd River Formation 

to P tauricznerez, in which case they do not differ significantly 

(t=l.18, n=10, p=0.25). Perhaps this lack of difference is due to the 

small sample size from the Wind River Formation, which appears to 

include only specimens in the lower end of the size range of M1 length. 
800 

700 (/) 

oc 

w 

1-

w 600 

:2 

~ 

z 500 

0 

i= 

en 400 0 

~ 

5:2 

:I: 300 ~ 

<( 

a: 

(!) 

200 ~ a: 

1-

(/) 100 

0 

ORDER PROTEUTHERIA 

c • -Q-e44C 

0§ • ~ ® 

0 m 

• 

• 

.. () 

••• • • • • 

1 3 15 17 19 

loge (LENGTH x BREADTH) OF M2 

EXPLANATION 

e W1llwood Format1on Prod1acodon tauncmere1 

() Type of Prod1acodon tauncmere1 

0 Willwood Format1on Palae1ctops b!cusp1s 

e Type of Palae1ctops matthew1 

• Type of Palae1ctops pmeyens1s 

2 1 

C Range of Wmd R1ver Format1on Palae1ctops b1cusp1s 

-¢- Mean of Wmd R1ver Formation Palae1ctops blcusp1s 

4 Type of Palae1ctops mult1cusp!s 

17 

FIGURE 8 -Stratigraphic plots of M2 m some early Eocene leptictids Measurements 

of stratigraphic position are from the base of the Willwood Formation Positions of 

non-Willwood specrmens are hypothesiZed 

The type specimen of P pzneyenszs also is closer in Size to the mean of 

the Lost Cabin Member sample of P bzcuspzs than it is to the mean 

of the Produu:odon tauricznerez sample, and it falls Within the 

loge(LXW) range of the former species (fig 8). 

For these reasons, Palaezctops pzneyensis is removed fFom synonymy with Produu:odon tauricznerez and is tentatively referred to 

Palaeictops bicuspis. (See following text.) This new appraisal re-
18 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO. 

TABLE 1.-t values for pair-wise comparisons of early Eocene samples of Prodiacodon 

and Palaeictops 

[Willwood sample of Prodiacodon tauricinerei is mostly Graybullian in age. Computation of t values used the 

standard deviation of sample. Where not given by Guthrie (1967b, 1971) for Wind River Formation samples, 

they were estimated using either S,=\4 range or s,=s,, where s, was the standard deviation of other sample. 

Estimate used in each case was chosen to maximize robustness of conclusion (that is, if it was desired to 

demonstrate that two samples were not significantly different, a minimum estimate of "s" was used. 

n=n,+n1-2=degrees of freedom). Probability values (p) were determined from a graph and are necessarily approximate. •, significant; ••, highly significant] 

Biostratigraphic unit and taxon M,L M,W M,L M.w 

Willwood Formation t: 6.4 6.8 7.9 8.1 

P. tauricinere~ Bighorn n: 14 13 24 24 

Basin Lysite zone. p: .0001 ** .0001** .0001** .0001** 

Willwood Formation t: 1.18 3.2 8.14 1.92 

P. tauricinere~ Wind River n: 10 9 20 20 

Formation, Lysite Member. p: .25 .01* .0001** .0001** 

Willwood Formation P. tauri- t: 9.75 6.2 10.2 7.23 

cinere~ Wind River Forma- n: 11 12 22 21 

tion, Lost Cabin Member. p: .0001** .0001** .0001 ** .0001** 

Bighorn Basin Lysite zone, t: 3.62 1.62 1.08 1.81 

Wind River Formation, n: 8 6 14 14 

Lysite Member. p: .01:" .15 .25 .08 

Bighorn Basin Lysite zone, t: .94 .42 1.7 .54 

Wind River Formation, n: 9 9 16 15 

Lost Cabin Member. p: .35 .70 .12 .65 

Wind River Formation Lysite t: 14.4 1.36 3.19 1.89 

Member, Wind River For- n: 5 5 12 11 

mation, Lost Cabin Member. p: .0001** .2 .01* .09 

stricts the known temporal range of Prodiacodon tauricinerei to early 

and middle Wasatchian time in the northern Rocky Mountains, 

though it is represented in a Lostcabinian fauna from the San Jose 

Formation of New Mexico (AMNH 48763 from Arroyo Blanco). 

Prodiacodon sp. 

Plate 2, figure 6 

Refe"ed specimens.-YPM 26013, 26040 (pl. 2, fig. 6), possibly 

26026. 
ORDER PROTEUTHERIA 19 

D'tscusswn.-Two specimens from the middle Gray Bull zone of the 

central Bighorn Basin Willwood Formation have a morphology distinct from that of contemporary Prodzacodon taunc'tnere't. The specimens fall Within the size range of that species (text figs 6, 7), though 

the M2's are shghtly more robust. The most distmctive characters, 

however, are the very large entoconulid on P4 (P5 of Novacek, 1977) 

through M8, and the colineanty of the remaining talonid cusps. These 

characters are contrasted with a weak to absent entoconulid and a 

hypoconulid that is more posterior than the entoconid and hypoconid 

in typical P taunc'tnerei. 

Both specimens are from a single locality (YPM loc. 290) where 

P taunc'tnere't is not known. A third specimen of a leptictid from tlus 

site (YPM 26026) is missing the lingual portion of the tooth, rendering specific identification impossible. Locality 290 has a number of 

unusual faunal elements; for example, there is a very lugh abundance 

of the otherwise rare dermopteran Plagiomene multwusp'ts. Presence 

of this fossil in abundance indicates the locality might represent an 

unusual Willwood ecology. This insulanty of occurrence, coupled 

With the possibility that Prodzacodon sp. might be geographically 

sympatric with, but ecologically distmct from, P tauncinere't, has 

here led to separation of the species on characters that otherwise 

might be attributed to intraspecific variation 

Palaeictops bicuspis (Cope, 1880) 

Plate 2, figures 3, 5 

Referred spec'tmens.-YPM 17508, 17521, 17522, 18584, 18588, 

18592, 23070, 23072, 23079, 23118, 23723 (pl. 2, figs 3, 5), 23805, 

24964, 27918 (including YPM 28783), 27937, 29638, 30618, 30652, 

possibly YPM 26852, 28111, U.S. National Museum 19204. 

D'tscusswn.-The type of Palaewtops bicusp'ts IS from the Lost 

Cabin Member of the Wmd River Formation, though all referred 

specimens from the Willwood Formation (Van Houten, 1945; 

Novacek, 1977) are from older rocks. Scatter diagrams of length versus trigorud width of M1 and M2 of the Lost Cabin Member of the 

Wind River sample and the sample from the Lysite zone in the Bighorn Basin overlap considerably (figs. 6, 7). The means for the Bighorn Basin sample are slightly smaller in most dimensions, but the 

differences are not significant (table 1). The means of the Willwood 

sample are intermediate between those of the Wind River Lost Cabin 

Member sample assigned toP bwusp'ts by Guthrie (1971) and m the 

Lysite Member sample assigned by the same author (1967 a) to P 

pmeyens'ts. The Willwood sample from the Lysite biostratigraphic 
20 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

zone is significantly different from the Lysite Member sample only in 

the dimension of M1 length (see text on previous page), though the 

Lysite Member sample is significantly different from that of the Lost 

Cabin Member in both M1 and M2 length. 

Retention of the name P ''p.,neyens'ts" for specimens from the 

Lysite Member of the Wind River Formation would imply that two 

hneages of leptictines were present in the middle and late Wasatchian; whereas, the combined stratigraphic and morphologic evidence 

points to the existence of a single lineage that showed an increase in 

indiVIdual size through time. Palae'tctops bndgeri, a probable middle 

Eocene member of this lineage, is larger than Lost Cabin Member P 

b'tcusp'ts. The type specimen of P ''p.,neyensis" from the La Barge 

fauna is an individual from the small end of this stratigraphically 

controlled size spectrum. 

If Palaeictops ''p'tneyensis" is distmct from P b'tcuspis, as suggested in 1977 by Novacek (although not a synonym of Prodwcodon 

tauncinerei), a southerly migration of these two species may have 

taken place. Palae'tctops bicuspis first appears in the Lysite zone of 

the Willwood Formation and occurs in the younger, more southerly 

Wind River Basin Lost Cabin Member, where it was apparently 

absent during Lysitian time. P ''pineyens'ts" first occurs in the Lysite Member of the Wind River Formation. The species disappears 

there in Lostcabinian time, but does occur in the Lostcabinian La 

Barge fauna of the northern Green River Basin. Alternatively, this 

same evidence could be interpreted as the southerly migration of a 

single species that had a north-to-south size cline 

Family PANTOLESTIDAE 

Palaeosinopa incerta, sp nov 

Plate 3, figures 3, 4, plate 10 

Synonyms.-Palaeos'tnopa d'tdelphoides Matthew (1918), In part; 

cf. Palaeos'tnopa d'tdelpho'tdes of McKenna (1960a); Palaeos'tnopa sp. 

of Gazin (1962); Palaeosinopa sp. E of Van Valen (1967); Palaeosinopa 

d'tdelpho'tdes of Delson (1971), in part, Palaeos'tnopa lutreola of 

Guthrie (1971). 

Etymology.-Latin incertus. uncertain, for the uncertain taxonomic status that specimens included in this species long held 

Holotype.-UMMP 69722, partial skull and lower jaws (pl. 10). 

Locality.-UMMP locality SC-211, lower part of Willwood Formation, sec. 3, T. 55 N., R. 101 W., Park County, Wyo 

Hypod'tgm: The type specimen and YPM 25506, 25648, 25892, 

30613 (pl. 3, fig. 3), 32258, 37246, AMNH 15701, 16239, 16823, 
ORDER PROTEUTHERIA 21 

94457, UCMP 44047, CM 22039, 22040, 22041, possibly AMNH 

39565 (pl. 3, fig. 4), 56226, 56227 

D'tstnbutwn.-Lower to upper Gray Bull zones, Bighorn Basin, 

Wyo.; Graybullian equivalents in Washakie and Powder River(?) 

basms, Wyo., and Sand Wash Basin, Colo ; Lost Cabin Member of 

Wind River Formation, Wind River Basin, Wyo.; San Jose Formation, N. Mex. 

Dwgnosis .-Intermediate in tooth siZe between its contemporanes 

P veterrima and P lutreola in early Wasatchian faunules; smaller 

than contemporary P didelphoides in late Wasatchian faunules. M1 

trigonid subequal in width to talonid and M1 relatively narrower than 

in P veterrima or P d'tdelphmdes. M2 talonid generally much narrower than trigonid (YPM 25506 and 25892), and trigonid relatively 

as wide as in P veterrima and P. d'tdelphoides 

D'tscusswn.-As early as 1918, Matthew observed that all the large 

Willwood specimens of Palaeosinopa could not be reasonably accomodated in P. veterrima. He assigned the smaller, less robust specimens to P. d'tdelphmdes and remarked that they might eventually 

prove to be variants of P veterrima. McKenna (1960a) and Gazin 

(1962) also recorded a medium-size species of Palaeos'tnopa in the 

Four Mile and Bitter Creek faunas, respectively. Van Valen (1967), in 

a discussion of Paleocene pantolestids, grouped these specimens together in a new species that he designated Palaeosinopa sp. E, 

distinct from P. d'tdelphmdes. Delson (1971), in his examination of the 

pantolestids in the Powder River local fauna, decided that the three 

species were merely populations of a single species that were dispersed over a wide geographic area. He referred both P vetemma 

and Palaeos'tnopa sp. E toP d'tdelphoides. 

After examining the Willwood collection of Palaeosinopa in the 

Peabody Museum and American Museum collections, the specimens 

referred toP. sp. E by Van V alen, and a few specimens from the Wind 

River Basin earlier referred toP. d'tdelphoides, we conclude that there 

are at least five Eocene species of Palaeos'tnopa. P. veterrima, P 

didelpho'tdes, P 'tncerta, sp. nov., P lutreola, and a new large species, 

incorrectly referred to P. veterrima (CM 24042) by Guthrie (1971) 

Evidence for this viewpoint is largely derived from scatter distnbutions and on statistical data on the ranges and coefficients of variation of these samples. 

A scatter diagram of length versus trigonid width of M1 (fig. 9) 

shows that the Willwood specimens represent three groups: P 

lutreola on the small end, P. veterrima on the large end, and P incerta 

in the rmddle. A snmlar plot for M2 (fig. 10) less clearly separates 

these groups, possibly owing to three specimens with very wide trigonids. When length is plotted against talonid width for M2 and M1 

(figs. 11, 12), the separation is more distinct for M2 but remains the 
22 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

44 

40 

en 

a: 

w 

1-

w 

~ 

j 3 6 

~ 

~ 

::i b 3 2 

~ 

0 

z 

0 

~ 2 8 a: 

1-

24 

• • • • • • ••• • 

• • c 

• ~ A 

•o • 

0 

• • 

• 

34 38 42 46 50 54 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e W1llwood Format1on spec1mens 

4 Pa/aeosmopa mcerta (AMNH 39565) 

c Type of Pa/aeosmopa dJdelpho1des 

0 Wmd R1ver Format1on spec1mens referred 

to Palaeosmopa lutreola by Guthne (1971) 

~ Four M1le fauna spec1men 

• • 

• 

FIGURE 9 -Scatter diagram of measurements of M1 m early Eocene Palaeosmopa 

• • 

• 

same for M1 The specimens referred to Palaeos~nopa sp. E by Van 

Valen (1967) from the Four Mile fauna and San Jose Formation lie 

clearly within the P incerta groupmg, as do specimens referred to P. 

lutreola by Guthrie (1971). If Delson's (1971) specimens are, in fact, 

M/ s, then they also belong in P ~ncerta. If, on the other hand, they 
48 

44 

(j) 

a: 

w 

1-

w 

:2 40 

:::i 

...J 

~ 

z 36 

:i 

1-

0 

~ 32 

Q 

z 

0 

~ 28 a: 

1-

24 

3 2 

• 

A 

D 

• 

• 

ORDER PROTEUTHERIA 

• 

• 

36 40 44 48 52 56 60 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

W1llwood Formation spec1mens 

Palaeosmopa mcerta (AMNH 39565) 

Type of Pa/aeosmopa d!delpho1des 

New Mex1co spec1men 

23 

Lost Cabm Member spec1mens, Palaeosmopa /utreola 1s at the 

bottom, Palaosmopa mcerta (m1ddle), and Palaosmopa 

veternma (top) 

Range of Wmd R1ver Format1on Palaeosmopa dldelpho!des 

Upper, Palaosmopa veternma, lower, Palaeosmopa mcerta 

FIGURE 10 -Scatter diagram of measurements of M2 m early Eocene Palaeosmopa. 

Dashed dotted lme 1s range of Wmd R1ver Formation P dulelphoules Upper 

dashed lme 1s P uetemma, lower dashed lme 1s P mcerta. Three specwens m lower 

left comer are P lutreola 

are M1's, they would, conversely, be more appropriately assigned to 

P veterrima. The type and two other specimens of P didelphoides 

from the Lost Cabin Member of the Wind River Formation were also 

plotted, and these occur between P mcerta and P veternma, 

evidence of the size overlap mentioned by Delson (1971). 

If the sample for all three species is combined, the coefficient of 
24 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

48 

44 

(/) 

0: 

~ 40 w 

~ 

~ _J 

~ 

~ 36 

J:. 

1-

0 

~ 

0 32 

2 

0 

_J 

< 1-

28 

24 

• • 

• 

• •• •• •• .! 

• • • ~ 0 • A 0 

• ~ • 

• 

34 38 42 46 50 54 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e Willwood Format1on spec1mens 

A Type of Palaeosmopa mcerta 

~ Four M1le fauna spec1mens 

c Type of Palaeosmopa dJdelphoJdes 

0 Wmd R1ver Format1on spec1mens (referred 

to Palaeosmopa lutreola by Guthne, 1971) 

• 

• 

• 

• • 

• 

FIGURE 11-Scatter diagram of measurements m M, of early Eocene Palaeosmopa. 

Lmes separate P lutreola (bottom), P mcerta (middle), and P vetemma (top, excludmg type of P dulelphoules) 

variation for the Willwood Gray Bull zone sample alone is 12.3 for 

M1W and 9.3 for M2W. These values are very large for a single species 

(for example, Gingerich, 1974b). Moreover, a plot of loge (LXW) of M1 

shows that 1t would require 0.75 natural log units (fig. 13) to encom-
46 

(/)42 

a: 

w 

tw 

~3 8 ....J 

....J 

32 

ORDERPROTEUTHERIA 

• 

I• • 

~~· a•• 

0 

• ~ 

• 4 • • 

• 

• 

36 40 44 48 52 56 

ANTEROPOSTERIOR LENGTH, IN MILLIMETERS 

EXPLANATION 

e W1llwood Format1on spec1mens 

4 Type of Palaeosmopa mcerta 

+ New Mex1co spec1mens 

~ Lost Cabm Member, Wmd R1ver Format1on, spec1mens 

o Type of Palaeosmopa d!delpho1des 

25 

• 

60 

FIGURE 12 -Scatter diagram of measurements of M2 m early Eocene Palaeosmopa. 

Lmes separate P lutreola (bottom), P mcerta (IDiddle), and P uetemma (top, excludmg type of P dulelphoules) 

pass the entire P. incerta-P vetemma complex (P dtdelphmdes was 

excluded from this histogram). Unpublished data of P D. Gingerich 

and D. A. Winkler and of David Schankler shows that the normal 

range for both extant and fossil species is between 0.35 and 0.45 

natural log units. This is approximately the range for each of the two 

included species, though that of P. tncerta Is somewhat less, possibly 

due to the small sample size. 

All the Wmd River Basin specimens (except CM 24042) could be 

assigned to P dtdelphoides without increasing the coefficient of variation (6.3 for M1W) beyond that probable for a single-species. The 

three smallest specimens have provisionally been referred to P in-
26 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

>-

6 

5 

~ 4 w 

::> 3 

d 

~ 2 u.. A 

20 22 

2 

B c 

I • I L I -, 

24 26 28 30 32 

loge (LENGTH x BREADTH) OF M1 

FIGURE 13 -Histogram of loge(LXW)M, m early Eocene Palaeosmopa. 1Is range of 

Wmd River Formation specrmens, mcludmg those referred toP lutreola by Guthne 

(1971) 2 1s range of Wmd River Formation specrmens, excludmg those referred to 

P lutreola by Guthne (1971) A, P lutreola, B, P mcerta, C, P vetemma. 

certa. The reinclusion of these specimens in P. duielphmdes would 

remove the record of P. incerta from the Lost Cabin Member of the 

Wind River Formation but not from all rocks of Lostcabinian age. 

The San Jose specimen still falls beyond the range for P. didelphoides. Whichever interpretation is correct, P. didelphmdes is not 

now known from early or middle Wasatchian faunas, and it is not 

identified as such in the present scheme because its size range 

overlaps the upper part of that for P incerta and the lower part of 

that for P. veterrima, without wholly encompassing either. 

Palaeosinopa didelphoides is probably a descendant of either P 

zncerta or P. veterrima. If the three small CM specimens are included 

in P. didelphoides, then that species is probably derived from P. incerta; if they are excluded, then derivation from P. veterrima is more 

plausible. 

Overall time versus size plots for M2 and M1 are presented in 

figures 14 and 15. The vagueness of these plots is related to the fact 

that the size measure (a modification of Gingerich, 197 4b) discriminates best when changes in size are unaccompanied by changes in 

shape. In this instance, there is a shape change between P incerta 

and P veterrima, and the latter also is more robust. 

Palaeosinopa veterrima Matthew,1901 

Plate 3, ngure 1, plate 4, f1gures 1, 2 

Referred specimens.-YPM 17032, 22253, 22867, 23469, 23475, 

23543, 23569, 23587' 23588, 23738, 237 43, 25223, 25849, 26087' 
(J) 800 a: 

UJ 

1-

UJ 

:2 

~ 600 

z 

0 

i= 

U5 

0 400 a.. 

~ 

:I: 

a.. 

<( 

a: 200 

t!) 

i= 

<( • a: 

1-

(J) 

ORDER PROTEUTHERIA 

() 

c 

• 

0 00 

I ' ' • • I 

A B I 

c.• c 01 

• I 

I 

' • • A :• • I 

22 24 26 28 30 32 1 loge (LENGTH X BREADTH) OF M2 

EXPLANATION 

• YPM W1llwood Format1on spec1mens 

0 AMNH W1llwood Formation spec1mens 

c New Mex1co spec1men 

A Type of Palaeosmopa mcerta 

() Type of Palaeosmopa dJde/pho1des 

27 

0 

0 

34 

FIGURE 14 -Stratigraphic plots of M, m early Eocene Palaeosmopa Measurements 

of stratigraphic position are from the base of the Willwood Formation Posltaons of 

non-Willwood specunens are hypothesiZed Dashed lmes separate (A) Palaeosmopa 

lutreoiD, (8) Palaeos£nopa mcerta, and (C) Palaeos£nopa vetemma and P drdelphordes 

26269, 26674 (pl. 4, fig. 1), 26913, 27063, 27168 (pl. 3, fig. 1), 27216, 

28969, 30569, 30576, 30629, 32100, 32173, 33916, 34255 (pl. 4, fig. 2), 

35307, 36921, 36925, 37249, YPM field numbers 63-596, 63-891, 

65-288, 70-693, 75-415, AMNH 95, 150a, 2849, 2851, 15092, 15095, 

15096, 15097, 16822, 16824, 56224, 56225, 94448, 94449, 94450, 

94451, possibly AMNH 16943. 

Dzscussion.-Palaeosinopa veterrima is the most common and temporally wide ranging of Willwood species of this genus. It is known 

from more than fifty specimens from localities in the lower Gray Bull 

through Lysite zones. The other two species of Willwood Palaeosznopa 

are, at present, known only from the Gray Bull zone. The absence of 

P veterrima from the richly fossiliferous level at 645 m probably 

means that this species became extinct in the Bighorn Basin towards 

the end of Lysitian time. Its absence in the Lost Cabin biOstratigraphic zone of that basin is, therefore, probably real and not merely 

due to the rarity of the species or to a paucity of fossils. Outside the 
28 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

(/) 800 0::: 

w 

1-

w 

:2 

~ 600 

z 

0 

E 

(/) 400 0 

Q.. 

~ 

:c 

Q.. 

<{ 200 0::: 

(!) 

i= 

<{ 

0::: 

1-

(/) 

~ ~ () 

B • 

0 0 0 

• 0 

•• • oe 

• 

A • • 0 A 

2 1 23 25 27 29 3 1 

loge (LENGTH x BREADTH) OF M1 

EXPLANATION 

e YPM W1llwood Format1on spec1mens 

0 AMNH Willwood Format1on spec1mens 

A Type of Palaeosmopa mcerta 

e Spec1mens from the Four Mile fauna 

() Type of Palaeosmopa d!de/pho1des 

~ Wmd R1ver Format1on spec1mens (referred 

to Palaeosmopa lutreola by Guthne, 1971) 

• 

• c 

0 

, 

0 

33 

FIGURE 15 -Stratigraphic plots of M, m early Eocene Palaeosmopa. Measurements 

of stratigraphic position are from the base of the Willwood Formation Positions of 

non-Willwood specrmens are hypothesiZed A, P lutreola, B, P mcerta, C, P veternma (excludmg type of P duielphouies), dashed lme separates Band C 

Bighorn Basin, P. veterrima, as defined in this paper, 1s known only 

from two isolated teeth from the Powder River local fauna (AMNH 

56224 and 56225) 

As mentioned earlier, P veterrima is considered distinct from P. 

duielphmdes, a species shown to occupy only the lower half of the size 

range of P. veterrima. The means of the lengths of M2 do not differ 

significantly (5.48 for P veternma; 5.34 for P duJ,elphmdes, from 

Guthrie, 1971). The mean for the w1dth of M2 of P dldelphoides (3.91) 

is, however, significantly smaller than that for P veternma (4.37), 

with a probability of less than 0.001 (t=5 91, n=28) that the two 

samples are from the same statistical population, and that the difference observed is entirely due to stochastic effects. Similar results are 

obtained from an analysis of M 1 The difference in tooth lengths is not 
ORDER PROTEUTHERIA 29 

significant, whereas the difference in width is (p=0.01, t=2.76, 

n=24). If the specrmens referred toP lutreola by Guthne (1971) are 

included in the P d1,delphozdes sample, the results are substantially 

the same, although the level of significance is more in line with that 

obtained for M2• This level of significance might indicate that the entire Wind River Formation sample belongs to a single species Whichever case is correct, P. didelphozdes has been demonstrated to differ 

significantly in some measures from P veternma when the species 

are considered as populations. P. d1,delphoides has been shown to be 

shghtly less robust than P veternma, as indicated by Matthew 

(1918), even though the measurements he gave for individual specimens mdicate the reverse (a point noted by Gazin, 1962). 

The specimen (CM 24042) referred to P veternma by Guthrie 

(1971) is here considered to be representative of a new, larger but less 

robust species. It falls well outside the boundary of P. veternma in 

a scatter diagram and is not encompassed in the range of the 

loge(LXW) size measure (0.17 natural log units larger than the 

largest specimen of P veterrima). Although there is considerable 

vanation in the shape of M1 in P veternma, the width-to-length ratio 

of CM 24042 of 0 58 lies more than 3.5 standard deviations from the 

mean of that for all Willwood specimens of P veternma (X=0.75, 

s=0.048, range=0.67 -0.84). 

The upper molars of P veternma also show considerable variation 

in shape. This variation can be seen in the condition of the cingulum 

on M1 and M2

• In most specimens, the cingulum is closely appressed 

to the body of the tooth with the precingula and postcingula being 

disJunct at the lingual margin. In one specimen (YPM 23475), 

however, the cingulum is nearly complete, although narrow, and in 

another (YPM 27216), the postcingulum is expanded with a slight 

median ridge and the precmgula and postcingula are completely confluent on the lingual side of M2

• 

Palaeosinopa lutreola Matthew, 1918 

Plate 3, figure 2 

Referred spec,mens.-YPM 23082, 25843, 26175 (pl. 3, fig. 2), 

26604, AMNH 15102, 16170, 56222, 56223, UW 7917, 8995, 9588. 

Discussion -Palaeosinopa lutreola is known from rocks of early 

Graybullian age in the Powder River Basm, the Clark's Fork Basin, 

and the Bighorn Basin (both No Water and Elk Creek section 

faunules). In the fauna of the Elk Creek section, it also occurs in the 

middle and upper Gray Bull biostratigraphic zones (the type is from 

the upper Gray Bull zone of the Elk Creek section). P. lutreola is the 

II 
30 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

smallest and least common of Palaeosinopa species, and its absence 

from rocks of the Lysite and Lost Cabin zones in the central Bighorn 

Basin may be due either to its absence or rarity. 

As mentioned earlier, the two specimens from the Lost Cabin 

Member of the Wind River Formation, referred by Guthrie (1971) to 

P lutreola, are well outside the range for this species and are more 

properly assigned to P lncerta or possibly P dldelphoides. YPM 

26604 and specimens referred by Bown (1979) to P cf. lutreola are 

considerably larger than the type specimen but still are within the 

possible range for this species and are provisionally referred to it 

here. 

Famlly APATEMYIDAE 

COMMENTS ON APA TEMYS MARSH, 1872 

Analysis of the genus Apatemys has been plagued by the paucity 

of specimens available for study. This shortage of specimens has not, 

however, precluded the publication of major reviews of Apatemys 

and the Apatemyidae in recent years, one from a pnncipally morphological viewpoint (McKenna, 1963), and another utilizing the biometric approach (West, 1973). The major emphasis in both of these 

and earlier works on apatemyids has been the attempt to identify 

consistent and useful characters that allow meaningful separation of 

this genus into species. McKenna (1960a) recorded two species of 

Apatemys in the early Wasatchian Four Mile fauna and divided the 

majority of early Eocene apatemyids into two groups. The first of 

these was believed to be characterized by '' * * * a reduced, singlerooted P4, a strongly developed fossa beneath P4, and two major 

mental foramina * * *," and the second group by "* * * an unreduced, semimolariform, double-rooted P 4, a generally weak or totally 

absent fossa beneath P4, and a single major mental foramen * * *." 

Guthrie (1967a), in discussing Apatemys whltaken, demonstrated 

that the taxonomic utility of the number of mental foramina breaks 

down within a single species. Robinson (1966), in reviewing the Huerfano fauna, suggested a possible synonymy between the smallest and 

largest Bridgerian species of Apatemys: A bellulus and A. rodens. 

The most recent and comprehensive review of the apatemyids was 

published by West (1973). Using the characters cited by McKenna 

(1960a, 1963) and tooth size distributions, West believed that no correlations could be made and that no unified groups exist within the 

genus. Consequently, West synonymized all Wasatchian and Bridgerian species of Apatemys with the earliest described species, A 

bellus. The present study is not as exhaustive in terms of the number 
ORDER PROTEUTHERIA 31 

of specimens studied as was West's, and so in a few instances West's 

analytical data was used. In using his data, West's-study was examined critically and the following notes were made. 

On page 12, West (1973) stated that 95 percent of the measurements of Apatemys specimens fall within one standard deviation of 

the mean, and that this '' * * * confirms the conclusion that all may 

be assigned to a single species.'' A recalculation shows that at least 

95 percent of the measurements fall withm two standard deviations 

of the mean and that whereas this is consistent with a normal distribution, it does not specify normality nor does it say anything 

about the number of spectes contained in the distribution. It should 

be noted that if it were true that 95 percent of the measurements 

occurred within one standard deviation, this would be a strong indication of non-normality (that is, a long-tailed distribution, with the 

specimen or specimens in the tail probably representing a second 

species). The distribution of Wasatchian M3 lengths in Apatemys 

(West, 1973, fig. 3) most closely approaches such a situation (82 percent fall Within one standard deviation), and it seems clear that the 

specimen that defines the tail, YPM 23476, represents a distinct 

species. 

After performing t tests on the Wasatchian and Bridgerian 

samples, West (1973, p. 13) concluded that at "* * * the 95 percent 

or higher level of confidence both early and middle Eocene samples 

could be drawn from the same statistical population.'' In fact, no 

probability statement about the populations being the same is 

Justified by the t test All that can be said is that values of t as large 

as those obtained would occur at least x percent of the time (where x 

is determined by t and the degrees of freedom), if the populations 

were the same. West is correct in noting that the t test is a statement 

about statistical populations and not about species (that is, two 

species could be present in both early and middle Eocene samples, 

but as long as there was no appreciable change in their means and 

variances, the t test would gtve the same result). 

West (1973) addressed this last point on page 15 where, m discussing the range of variation of the Wasatchian and Bridgerian samples 

indiVIdually, he concluded that only one species is present at each 

sampled interval. For the Wasatchian sample (including two 

specimens from the late Tiffanian), West observed that although 

both small-size and large-size groups exist, the bimodality 1s not sufficient to warrant recognition of two species and that this conclusion 

is confirmed by t tests. West did not state if the tested groups were 

determined by a cntenon other than size (for example, number of P 4 

roots), but 1t must be assumed that they were, for 1t is mconcetvable 

that a distribution solely on the basis of size would not show a significant difference between the two resulting groups if the t test were 
32 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

used. If one divides the Wasatchian sample in West's (1973) figure 2 

at an M1 length of 2.0 mm (millimeters) and compares the resulting 

two groups using the t test, they are shown to be significantly different (t=6.37, n=18), with a probability of less than 0.001 that this difference is due to chance. 

For the Bridgerian sample (including a few specimens from rocks of 

Uintan age), West (1973) observed only that there is less variation 

than in the Wasatchian sample, a fact he attributed to the smaller 

geograpluc and temporal range of this sample. However, a histogram 

of M2 lengths in the Bridgerian sample (fig. 16, tlus paper) shows that 

the sample separates into three groups. These groups correspond 

with the three earlier recognized Bridgerian species, A bellulus, A. 

bellus, and A. rodens, respectively. To test these two alternative 

schemes for grouping the samples, a chi-square test and a Bayesian 

analysis were employed. The only assumption made was that the 

underlying distributions are approximately normal. For West's 

(1973) one-species case, the null hypothesis is that the underlying 

distribution is a normal population with a single mean and standard 

deviation, as specified by the sample. For the three-species case, the 

null hypothesis is that there are three normally distributed populations, each having a mean and standard deviation specified by the 

sample, except for A rodens. The standard deviation for A. rodens 

was made equal to 0.12 and was determined by assuming that A 

rodens had a coefficient of variation equal to that of A. bellulus and 

A bellus. In the actual sample, A rodens has a standard deviation of 

zero. This figure is unrealistic and would bias the tests m favor of the 

three-species hypothesis. 

The expected values for the chi-square test (equal to np,) were 

calculated in the followmg manner. For the one-species hypothesis, 

n equals 27, and for the three-species hypothesis, n equals 12, 13, or 2, 

depending on whether the cell is in the subdistribution specified by 

A. bellulus, A bellus, or A rodens, respectively The probability of 

being in the cell (p) is determined from the integral of the Gaussian 

function defmed by the parameters of the hypothesis, that is, the ith 

cell (where " equals a length of M2 in millimeters) actually represents 

the interval i±0.05. Tlus interval specifies an area under the defined 

normal curve, which, when normalized, equals the probability of 

being in the l-th cell (pJ The results are given in table 2. As can be 

seen from this table, the chi-square test could reject the one-species 

hypothesis at the 0.025level of significance, but the three-species hypothesis could not be reJected at the 0.70 level of significance. In 

other words, one would expect to see a deviation as great as that 

observed in the one-species hypothesis only 2.5 percent of the time, 

whereas one would expect to see it 70 percent of the time in the threespecies hypothesis. 
> u 

6 

z 4 w 

::J 

5:: 2 a: 

LL 

0 

1.7 

ORDER PROTEUTHERIA 33 

1.9 2.1 2.3 2.5 2.7 2.9 

LENGTH OF M2, IN MILLIMETERS 

FIGURE 16.-Histogram of length of M2 for Bridgerian and Uintan sample of Apatemys (from West, 1973). 

TABLE 2.-Chi-square analr,;is of the distribution of length 

measurements of M 2 for t Bridgerian sample of Apatemys 

(ungrouped data) 

(Data from West (1973). 0, number observed. E, expected] 

Length of M, Number Expected, (0-E)' Expected, (0-E)' 

Observed 1 species -E- 3 species -E-

~1.7 1 2.8 1.16 1.30 0.07 

1.8 5 1.9 5.06 4.85 .01 

'1.9 5 2.4 2.82 4.90 .00 

2.0 2 3.0 .33 1.75 .04 

2.1 0 3.4 3.40 .31 .31 

2.2 1 3.4 1.69 1.45 .14 

2.3 6 3.0 3.00 4.40 .58 

2.4 3 2.4 .15 4.40 .45 

2.5 2 1.9 .01 1.48 .18 

2.6 0 1.2 1.20 .30 .30 

2.7 0 .8 .80 .52 .52 

2.8 2 .8 1.80 1.34 .32 

Total 27 27.0 27.0 x2 ••• 0 •••• 0 0 0 

1

21.42 22.92 

p ............ 0.025 0.72 

1

9 degrees of freedom. 2

5 degrees of freedom. 

One of the assumptions of the chi-square test, however, is that npi 

is greater than or equal to 5. This assumption- was not met in the 

analysis, but the data can be grouped (table 3) for the one-species 

hypothesis such that the expected value is greater than 5. The results 

are unchanged, and the one-species null hypothesis can still be rejected at the 0.025 level of significance. Because it is i!llpossible to 

group data for the three-species hypothesis in similar fashion without 

reducing the degrees of freedom to less than zero, the results of this 

test are inconclusive, but they are strongly suggestive that the 

sample contains three species and not only one. 
34 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

TABLE 3 -Chz-square analyszs of the dzstnbutwn of length measurements of M 2 for the 

BndJenan 

dat 

sample of Apatemys (grouped 

[Data from West 11973) and grouped such that np1 1s greater 

than or equal to 5 0, number observed E, espected) 

Length of M, Number Expected, (0-E)' 

observed 1 spec1es -E-

~18 6 47 036 

19-2 0 7 54 47 

21-2 2 1 68 495 

23-2 4 9 54 2 40 ~25 4 47 10 

Total 27 270 

p 0025 x2 •8 28 

~19 11 71 214 

20-21 2 64 302 

22-23 7 64 06 ~24 7 71 00 

Total 27 270 

p 0025 x2 2

5 22 

1

2 degrees of freedom 2

1 degree of freedom 

The Bayesian analysis employs the ordinate values of the Gaussian 

function to determine the relative probability of two or more hypotheses. This method is described in Pilbeam and Vaisnys (1975). This 

analysis indicates that the three-species hypothesis is 40 times as 

likely as the one-species hypothesis, given equal a priori probabilities. 

Because the three-species hypothesis is a priori the more likely on the 

basis of coefficients of variation (see next page), tlus test strengthens 

the original conclusion. 

A third alternative is that A rodens is conspecific with A bellus 

and that only two species were present in the Bridgerian. The Bayesian analysis shows that this hypothesis is one-tlurd as hkely as the 

three-species hypothesis, a relatively inconclusive result. 

A fourth alternative, proposed by Robinson (1966), 1s that the 

smallest species (A. bellulus) and the largest (A rodens) are conspecific. This suggestion was not considered because it is countermtuitive The union of these species was presumably proposed because 

of the single-rooted P4 held in common, but such a union produces a 

bimodal distribution. Because there is no independent eVIdence suggesting sexual dimorphism in apatemy1ds, tlus synonymy is unfounded. If sexual or size dimorphism were postulated for the A 

bellulus-A rodens union, it would be expected also in the remainder 

of the sample with a two-rooted P 4, and it does not occur there. 
ORDERPROTEUTHERIA 35 

One objection that can be raised concerning the preceding analyses 

is that the pooling of temporally and spatially disJunct samples 

might invalidate the assumption that the underlying population is 

normally distributed. The majority of specimens in the Bndgerian 

sample comes from a relatively restricted geographic area and temporal range in southwestern Wyoming, and the three type specimens 

from this area span nearly the entire range of size vanation. The two 

or three specimens from other areas (one is from the Huerfano formation of Colorado, and two are from rocks of Umtan age of California and Wyoming) were not removed from the analyses because it 

was not possible to distinguish them in West's (1973) scatter 

diagram. It is not beheved that their inclusion appreciably altered 

the analytical results because they do not represent end points in the 

siZe spectra. 

West (1973, p. 13) pointed out that the coefficients of variation for 

his measurements are often greater than 10. In fact, all his coefficients of variation are greater than 10 and most are between 15 and 

20. In a list of coefficients of variation for 19 mammalian species compiled by Gingerich (197 4b), only two species show coefficients greater 

than 10, and these species are known to be sexually dimorphic (10.7 

for M1W in Papw anubis, and 10.4 for M2L in Pongo pygmaeus). 

West observed that his coefficients of variation are high for singlespecies populations but attributed it to the "* * * great range of 

temporal and geographic sources.'' He believed that ''* * * the coefficient of variation is therefore not considered as significant in the 

statistical interpretation of Apatemys as are the comparison of 

sample means.'' 

It has been seen earlier that a comparison of sample means tells us 

nothing about how many species are involved within a certain stratigraphic level if one is comparing means between different stratigraphic levels. Known ranges of variation translated into known 

ranges for coefficients of variation do have interpretive biological 

significance, and they are, therefore, considered by us to be more 

sigmficant. Furthermore, West (1973) observed that no significant 

change had taken place through time iri his samples, and nowhere has 

he demonstrated that populations from different geographic regions 

differ enough to result in the large coefficients of variation that occur 

when these samples are pooled. In the absence of this demonstration, 

it is neither justified nor convincing to assume that large coefficients 

of variation would result. For the Bridgerian sample of Apatemys 

studied by West, division into three species results in coefficients of 

variation that are between 4 and 5, well Within the range given for 

several mammals by Gingerich (1974b). 

Studies of apatemyids are hampered by the small available 
36 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

(.9 

Cl 

CI: 

en en 

CI: 

~ 800- w 

~ 

z 

-, 600-

z 

0 

i= 

U5 0 400- D.. 

~ 

I 

~ 200- CI: 

(.9 

i= 

<( 

CI: 0- ..... 

en LL 

u 

e. ~ _. -.i ~ _. 

Apatemys bellu/us Apatemys bel/us 

• 0 

c c 

• • • 

Apatemys sp , cf 

Apatemys rodens 

0 

• • .MA b. b. 

0 0 Apatemys 

chardmt 

() 

Apatemys kayt 

06 08 10 12 14 16 

loge (LENGTH x BREADTH) OF M2 

EXPLANATION 

• Elk Creek sect1on specimens (YPM, UMMP, MCZ) 

0 UMMP Sand Coulee area spec1mens 

b. UW No Water fauna spec1mens 

1 8 20 

c Lys1te Member of Wmd R1ver Format1on (from Guthne, 1967) 

() Type of Apatemys kayt 

• Type of Apatemys whttaken 

o Type of Apatemys hurzelen (from Gazm, 1962) 

-. Bndgenan spec1mens (YPM) 

• Type of Apatemys bel/ulus 

• Type of Apatemys bel/us 

FIGURE 17 -Stratigrapluc plot of M2 m late Paleocene through Bndgenan specrmens 

of Apatemys Measurements of stratigrapluc position are from the base of the Willwood Formation CF, ClarkforJnan Provmcial Age, LGB, MGB, and UGB, 

lower, nnddle and upper Gray Bull biOstratigrapluc zones, L YS, Lysite 

biostratigrapluc zone, LC, Lost Cabm b10stratigrapluc zone, BRDG, Bndgenan 

Provmcial Age Lmes separate possible lmeages 
ORDER PROTEUTHERIA 37 

samples and a lack of good stratigraphic control for these samples. 

Lumping of samples from stratigraphically disparate localities by 

earlier workers has, doubtlessly, contributed equally to the problem, 

because this procedure tends to obfuscate, rather than clarify, complex patterns. As observed by Bown (1979), the pooling of tooth 

measurements for specimens from different stratigraphic levels in 

scatter diagrams, histograms, and the like probably gives us no 

reliable information concerning which and how many species occur in 

these samples. This lack of information is especially true if tooth 

sizes have changed significantly through time m the various lineages 

sampled. Earlier attempts to fit all the Apatemys morphologies into 

one or the other of McKenna's (1963) lineages creates additional problems because, from our study, there appear to be at least three lineages of Apatemys in the early Eocene. In figure 17, size measurements for M2 are plotted against time. The central Bighorn Basin 

Willwood Formation specimens were plotted according to their positions on a measured section (Schankler, 1980). The remaining specimens were located approximately by faunal comparisons. 

As seen in figure 17, two species occur m the lower Gray Bull zone: 

Apatemys chardzm, and A kayz. A chardini is the smaller of the two 

and is characterized by a two-rooted P4• A. kayz is a larger, mediumsize species that is typified by a reduced, single-rooted P 4• Both species exist in the Four Mile and No Water faunas and in the lower 

Gray Bull zone of the Clark's Fork and central Bighorn Basins. In the 

Powder River local fauna, only A. chardini is known; in the central 

Bighorn Basin, A. kayi does not occur higher than the middle Gray 

Bull zone; whereas A chardini appears to have given nse to A. 

bellulus (mcluding both A whitakeri and A. hurzeleri). The mediumsize Bridgerian species A. bellus first occurs in rocks of Lostcabmian 

age (Guthrie, 1971). Because A bellus shows variable conditions of 

the P 4 roots, it does not seem to be a hkely descendant of A. kayz. 

The fourth and largest lineage of Apatemys is represented by three 

specimens from the central Bighorn Basin. They are all from upper 

Gray Bull levels, near the boundary of the Gray Bull and Lysite 

zones, and the specimens are slightly larger than the type specrmen 

of Apatemys rodens. From A. rodens, they differ in several respects 

but are here believed to be its Wasatchian precursor. 

Apatemys uzntenszs (as defined by West, 1973) probably contains 

both small and middle-size species, possibly the Uintan descendants 

of middle Eocene A bellulus and A. bellus, respectively. 
38 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

Apatemys chardin1 (Jepsen, 1930a) 

Plate 4, figures 3, 6 

Referred specimens.-YPM 26468, 30558, 31170, UW 8908, 8997, 

9571, 9599, 9630, 9632 (in part), 9633, 9634, 9725, 10243, 10415, 

10416, UMMP 64934, 66686 (pl. 4, fig. 3), 67040, 67310, 67380 (pl. 4, 

fig. 6), 68486, 68565, possibly UMMP 65150, 68592, YPM field 

numbers 72-1822, 76-132. 

Discusswn.-Apatemys chard"tm, is the most common and wide 

ranging of the Gray Bull zone apatemyids. As mentioned previously, 

it is known from localities of this age in other basins. The type specimen (PU 13236) is from either a middle or lower Gray Bull zone locality in the central Bighorn Basin. The only other specimens of A. 

chardznz from the Elk Creek section of the Willwood Formation occur 

in middle Gray Bull zone localities. 

A chardini is the smallest species of Apatemys; the No Water, 

Powder River, and Four Mile specimens are slightly smaller than the 

Clark's Fork Basin or central Bighorn Basin specimens. The species 

differs from coeval A. kayi in the possession of a double-rooted P 4 in 

the majority of specimens. UW 8908, from the No Water fauna, is an 

edentulous ramus that appears to have a single alveolus for P 4• The 

specimen is tentatively referred to A chardzni because of its relatively small size. Because A. chardini is considered to be ancestral to 

A. bellulus, and assuming only one species is represented in the A 

chardinz sample, it is not unreasonable to expect a small proportion 

of the A. chardinz sample to have a single-rooted P 4• 

Referral of the small apatemyid from the Four Mile fauna to A. 

whitakeri (Delson, 1971) seems unwarranted. Delson recommended 

this name because of the similarity in size and morphology of the M2 

between this specimen and the type of A whztakeri. McKenna 

(1960a), on the other hand, recorded the similarity between this 

specimen and the type specimen of A chardznz in the size and construction of M3• Because comparable elements are not preserved in 

the types (excluding P4, the tooth in which both types differ from 

each other) and because P4 is not known in the Four Mile specimen, 

there is no justification for assigning it to A whitaken. 

Apatemys bellulus Marsh, 1872 

Plate 4, figure 5 

Synonyms.-Tezlhardella whitakeri Simpson, 1954; Apatemys 

hurzelen Gazin, 1962. 
ORDER PROTEUTHERIA 39 

Referred specimens.-YPM 27783, YPM field number 71-132; 

UMMP 66092 (pl. 4, fig. 5), AMNH 48004. 

D"tscusswn.-Apatemys bellulus was first described from Bridgerian rocks, but the species is here taken to include the late Wasatchian A whitakeri and A hurzeleri Simpson (1954) noted 

similarities shared by "Te"tlhardella wh"ttaken" and A. bellulus, but 

he referred his new species to Jepsen's (1930a) Te"tlhardella because of 

his reluctance to carry a Bridgerian genus into the Wasatchian. A 

comparison of the two types and other specimens referred to "T 

whitakeri" and A bellulus has revealed no characters that indicate 

that they are distinct. The other small late Wasatchian species, A. 

hurzeleri, does have relatively narrower molars than in A. bellulus, 

but, until other specimens are found with this character, Gazin's 

species is here considered to represent normal variation within A 

bellulus 

Lysite and Lost Cabm zone A bellulus are intermediate in size between the smaller Graybullian A. chardin"t and the larger A bellulus 

specimens from Bridgerian rocks. Where this tooth is preserved, all 

known specimens of A bellulus possess a single-rooted P 4; however, 

this is the only apatemyid now known from deposits of Lysitian age; 

it occurs in both the Willwood Formation of the central Bighorn 

Basin and in the Wind River Formation of the Wmd River Basin. In 

Lostcabinian time, it was more widespread (present in the Largo and 

La Barge faunas and in the type Lost Cabin Member of the Wind 

River Formation), and it is associated with A bellus in the type Lost 

Cabm Member (Guthrie, 1971). 

Apatemys kayi (Simpson, 1929) 

Plate 4, figure 4 

Referred spec"tmens.-YPM 22846, 25990, 26042, 35090, MCZ 

19685, UW 8999, 9574, 9622, 9632 (in part), UMMP 65187, 67038, 

68588, 68589, 68590, 68591 (pl. 4, fig. 4), 69132, possibly UW 9631. 

Discusswn.-Apatemys kay, is the oldest known species of 

Apatemys. The type specrmen comes from the Clarkforlaan Bear 

Creek fauna of southern Montana A kayi persists into the Wasatchian, where it is known from the Four Mile, No Water, Clark's Fork 

Basin, and central Bighorn Basin faunas. In the Elk Creek section of 

the Willwood Formation, it is not known higher than the rmddle Gray 

Bull zone. Although this species agrees in size with Apatemys bellus, 

it is an unlikely ancestor for that taxon because it is doubtful that the 

trend for reduction of P 4 was reversed. The P 4 is single rooted m all 

specimens of A. kayi where it is preserved, whereas in A bellus the 
40 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

condition of the P 4 roots appears to be variable. It is also possible 

that A. kayi is ancestral to the much larger A rodens; however, there 

is currently no other evidence to suggest this relationship. 

Apatemys sp , cf. A. rodens Troxell, 1923 

Plate 2, f1gure 7 

Referred spec1-mens.-YPM 23476 (West, 1973, fig. 8), 30582 (pl. 2, 

fig. 7), AMNH 48999. 

Discusswn.-Three very large specimens of Apatemys are known 

from the Willwood Formation of the central Bighorn Basin. The two 

YPM specimens are from localities on the eastern side of Red Butte, 

and the AMNH specimen is from north of Sheep Mountain. None of 

these localities are tied to measured sections, but other evidence (geographic and topographic positions and associated faunas) indicates a 

late Graybullian age, near the Graybullian-Lysitian faunal boundary. 

As demonstrated previously, there is considerable evidence on the 

basis of M2 size that A rodens is a valid species, distinct from its 

penecontemporaries A. bellus and A. bellulus. It is further distinguished by its very robust mandible and the relatively larger anterior 

incisor. A. rodens is also characterized by a single-rooted P 4, a weak 

P4 fossa, and the presence of a single, large, double mental foramen. 

The referred specimens agree with the type of A rodens m size and in 

the single-rooted P 4, although the alveolus for P 4 in the referred 

specimens is larger than in the type. In the referred specimens, the 

two mental foramina are oblique to each other but are clearly distinct, and the size of the P4 fossa Is variable (moderate in YPM 23476, 

almost absent in YPM 30582). The enamel of the enlarged anterior 

tooth in the type specimen is confined to the ventral half of the 

crown, whereas in YPM 23476 the enamel is thin but not well 

delimited. In the type specimen, the paraconid of M3 IS more prominent and more lingually placed than in the referred specimens Also, 

the talonid of M3 is more elongate and the cusps are more distinct 

The basins of the talonids are deeper in the type, and a small ridge 

connects the entoconid and the hypoconid on M2• These differences 

indicate individual variation but are of doubtful taxonomic significance. The inclusion of the three referred specimens in A rodens extends the known range of this species into early Wasatchian time. 

The Uintan Apatemys downs1- may also be referable to A rodens; 

however, this possibility warrants separate investigation. 
PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 41 

Order INSECI'IVORA 

Suborder ERINACEOMORPHA 

Family DORMAALDDAE1 

Krishtalka (1976a) recently reviewed the North American early 

Tertiary so-called adap1soricid insectivores and concluded, as did 

Russell, Louis, and Savage (1975), that Adapisorex Lemoine (1883) 

(in Bown, 1979) could not naturally be grouped with the more typical 

of the so-called adapisoricids. Krishtalka recommended no solution to 

this abandoned family status, relegating Adap-,sorex to the 

Erinace1dae, yet continuing use of the name Adapisoricidae for mammals grouped by Quinet (1964) and by Russell, Louis, and Savage 

(1975) in the Dormaaliinae. We believe that Adap-,sorex and the dormaaliines are distinct at least at the family level, and we elevate the 

Dormaaliinae to family status. Adap-,sorex appears, m our opinion, 

to be closest structurally to the erinaceid-like condylarths 

Phenacodaptes and Apheliscus (Gazin, 1959), though some 

specimens of Adap-,sorex abundans (for example, W albeck 390) are 

also similar in the lower dentition to Tiffanian B-,sonalueus Dormaal-,us IS an unfortunate type for this family, partly because of its 

strong similarity to Macrocranwn nltens (also noted by Russell and 

others, 1975) and partly because of the paucity of materials of Dormaal-,us. Both Macrocranion nltens and Dormaal-,us share several 

characters not found in other members of the family, and 1t may eventually become necessary to create a new subfamily to accomodate 

Scenopagus, Ankylodon, Talpauus, Talpaumdes gen. nov. (discussed 

later), and some of the new later Eocene forms described by Novacek 

(1976) from California. 

Krishtalka (1976a) beheved the following insectivores to be valid 

North American so-called adapisoric1d genera: 

Mckennathenum Van V alen, 1965 

Scenopagus McKenna and Simpson, 1959 

Ankylodon Patterson and McGrew, 1937 

Macrocranion Weitzel, 1949 

Talpauus Marsh, 1872. 

Mckennatherium ladae was believed by him to be the earliest as well 

as the most generalized member of the family, and an enigmatical 

form, "Diacodon" minutus Jepsen (1930b), was tentatively transferred to Adunator, a middle to late Paleocene European genus 

1 A chagnosts of the Dormaalndae ts under mvestlgatlon by M J Novacek, T M Bown, and Davtd Schankler 

(unpub data, 1981) 
42 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

(Russell, 1964). "D." ml.nutus and Adunator were then contrasted 

with some Paleocene hyopsodontids, with which they certainly share 

many derived characters. Because of the pivotal position that Mckennatherium (as "Leptacodon" ladae) has played in both recent and 

early evaluations of the origins of early insectivores and because its 

status as perceived by Krishtalka (1976a) relegates the genus to 

either real or supposed ple1siomorphy for Eocene dormaaliids, a critical examination of this genus is now necessary. 

We have compared most of the best specimens relevant to this 

problem, including Mckennatherium (USNM 9640, type of Leptacodon ladae; AMNH 35437, type of Mckennatherium ll.bl.tum; 

AMNH 35954, 35955; PU 17722), and "Dl.acodon" minutus 

(PU 13360, 13360a, 13304, types; PU 19395) with the type specimen 

of Adunator lehmani (W albeck 368) and conclude, as did Krishtalka, 

that lower teeth of "D." minutus and Adunator are virtually identical. Krishtalka (1976a) also recorded similarities of "D" minutus to 

Mckennatherium but chose to retain these forms as distinct genera; 

in his view, the latter genus is the earliest of the so-called 

adapisoricids, and the former genus is probably a hyopsodontid 

condylarth. We believe that Mckennatherium ladae and "Dl.acodon" 

ml.nutus are very closely related, and that both probably represent 

North American species of Adunator. 

Krishtalka (1976a, p. 10) believed that the following are attributes of Adunator and "Diacodon" minutus that are not shared by 

Mckennatherium: 

1. The talonids of M1_2 are shghtly 

elongate. 

2. M2 is larger than M1. 

3. The paraconid on M2 is extremely 

compressed and is merged with 

the anterior part of the metaconid. 

4. The metaconid is greatly expanded 

antenorly in lingual view so that 

it is much larger and more bulbous than is the protoconid. 

5. P .. has a well-developed paraconid 

that is as high (tall) as the 

metaconid 

6. The paraconid is strong on P 3 in 

"D." ml.nutus but is absent in 

Mckennatherium. 

These alleged differences led Krishtalka (1976a, p. 10) to remark: 

"These exceptions to adapisoricid affinities in the lower molars of 
ORDER INSECTIVORA 43 

Adunator-"D." mznutus are features associated with some Tiffanian 

hyopsodontid condylarths like Haplaletes." 

With respect to these differences noted by Krishtalka, we have observed that: 

1 The talonids of M1_2 in Adunator 

lehman., and "DULCodon" mlnutus 

are not perceptibly longer than in 

Mckennathenum. 

2. M2 is about the same size as M1 m 

the type of Adunator lehmanz 

(both are approximately 1. 7 mm 

long), as also in Mckennathenum 

(Krishtalka, 1976a, table 1). 

3. The M2 paraconid IS also compressed 

and is closely appressed to the 

metaconid in Mckennathenum. 

4 The M1_

3 metaconids are also large 

and anteriorly expanded in 

Mckennathenum. 

5. The P4 paraconid is shorter (less tall) 

than the metaconid in Adunator, 

"Diacodon" mznutus, and Mckennatherium but does arise at a 

lower pomt on the paracnstid m 

the last genus. 

6. The P 3 paraconid appears to be absent in some M ladae (for example, PU 17722; this cusp may have 

been broken off-only a cast of 

this specimen was examined by 

us); a strong paraconid 1s, 

however, present on P 3 in at least 

some Mckennatherium (for example, AMNH 35954, Krishtalka, 

1976a, fig. 2A). 

In our oprmon, materials of Adunator, Mckennathenum, and 

''Diacodon" minutus are nearly inseparable on the six above criteria, 

and what slight differences do exist do not argue convincingly for 

generic distinction Upper molars referred to Adunator and to "Diacodon" minutus are more distinct (as Krishtalka recognized); however, in both, their association with the lower teeth is uncertain. 

Mckennathenum is known from lower jaws preserving, in composite, P 2-M3, "DULCodon" mznutus is known from nearly the entire 
44 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

lower dentition, and Adunator 1s known from P 2-M3• The comparable 

parts of these lower dentitions are so similar, even in several trivial 

respects, that these animals were almost certainly closely related. 

The dental evidence does not indicate that they are dentally convergent homeomorphs, because there is no good morphologic basis 

for separation at the generic level. Fairly well established convergent 

similarities between other groups of well-known early mammals (for 

example, molars of plesiadapid and notharctine primates) rarely, if 

ever, pervade both the premolar and molar teeth, and a complex of 

crossing specialized characters allows the reliable identification of 

even isolated teeth. 

The systematic positions of Adunator and its probable North 

American allies "Diacodon" mlnutus and Mckennathenum ladae remain in doubt, however, none are dormaaliids. The removal of the last 

two species leaves this family without any certain described Paleocene representatives but unifies Eocene forms in a more cohesive 

morphologic group. Even so, the Eocene dormaaliids may not make 

up a natural grouping. Macrocranion, in particular, deviates from 

Scenopagus, Talpavus, Talpavmdes, and Ankylodon in several 

erinaceid features, some of which it shares with Dormaalius. In 

Macrocranion, these characters include the reduction in size of P 1_

3, 

the relatively large size of P .. with respect toM., relatively low molar 

trigonids, broad molar talonids, relatively tall entoconids, and relatively short (flat) hypoconids. 

Macrocranwn nitens has a close morphologic counterpart in late 

Paleocene Litolestes and differs from that genus principally m having somewhat more shelflike molar paraconids, relatively broader 

molar talonids, a less compressed M2 trigonid, and in the greater exaggeration of the tall, lingually deflected molar entoconids. P s is 

variable in Litolestes In AMNH 33936, it-is nearly as tall asP .. , but 

in PU 19387 (L. ignotus) it is short and reduced relative to P4• P3 in 

Macrocranwn is, invariably, greatly reduced relative to P4• The 

molars typically decrease in size posteriorly in Litolestes, whereas 

they are more nearly equal in s1ze m Macrocranwn. None of these 

characters, however, constitute insurmountable obstacles to the possible familial association of these genera, particularly when one considers our rudimentary knowledge of what are generalized and what 

are derived characters in early erinaceids. From a cladistic rather 

than a phylogenetic viewpoint, the association of Litolestes and Macrocranion is, to us, even more apparent. 

An evaluation of the many similarities shared by early erinaceids 

and certain condylarths is beyond the scope of this paper, and, in 

itself, warrants a general review. 

Perhaps of auxiliary importance to the early history of the dormaaliids is PU 18688, a right P3-M2 of dormaaliid-like mammal from the 
ORDER INSECTIVORA 45 

Torrejonian Rock Bench quarry of the Fort Union Formation (Polecat Bench Formation of Jepsen, 1940). This specimen is now on loan 

from the Princeton University collections and will, presumably, be 

described by other workers. However, the teeth appear to be sufficiently generalized to be of potential importance to the origins of the 

dormaaliids, geolabidids, or both. 

Macrocranion nitens (Matthew, 1918) 

Plate 5, figures 1-5, plate 6, figures 1, 2 

Referred specimens.-YPM 23077 (pl. 5, fig. 1), 23087,24380 (pl. 5, 

figs. 2, 5), 27941, 30443, 30533, 30597 (pl. 6, fig. 2), 30622, 30651, 

30654, 30655 (pl. 5, figs. 3, 4; pl. 6, fig. 1), 30657, 35159; UW 7057, 

8996 (Bown 1979, f1g. 42d), 9640, 9641, 9690. 

Discusswn.-As mentioned previously, placement of Macrocranion 

and Dormaalius in the same subfamily as Scenopagus, Talpavus, Talpavmdes, gen. nov. (p. 50), and Ankylodon may not adequately reflect 

the morphologic disparity between these two groups. The former two 

genera may even be erinaceids, and their inclusion in the same family 

as the other four genera is tentative 

Krishtalka (1976a) transferred Matthew's (1918) Entomolestes 

nztens to Macrocranwn Weitzel (1949), a relationship that was hinted 

at but not fully endorsed by Russell, Lows, and Savage (1975). The 

species nitens is certainly more aptly placed in Macrocranwn than in 

Entomolestes, but Krishtalka's (1976a) belief that nztens "* * * IS 

virtually identical to Macrocranwn tenerum (=Messelzna) * * *" 

does not seem compelling to us after we compared a large number of 

casts, illustrations, and descnptions. What differences do exist, 

however, seem to be more significant at the specific rather than at the 

generic level, and we hesitantly accept the synonymy of Entomolestes nitens with Macrocranwn. 

Russell, Louis, and Savage (1975) allocated numerous teeth from 

the French early Eocene to Entomolestes cf. nztens. Casts of the several specimens of French E. cf. nztens available to us are also provisionally referable to Macrocranwn, but we agree with Russell, Louis, 

and Savage (1975) that the identity of some of this sample is questionable, principally because of the large amount of variation in P 4 

and the upper molars. In several respects, the French sample 

resembles specimens of M nztens from the San Jose Formation of 

New Mexico more than those from the Willwood or Wind River 

Formations. 

Willwood Macrocranwn nztens conforms well with the type of the 

species (also from the Willwood) and with most specimens from the 

Four Mile fauna (Graybullian) and the Lysite and Lost Cabin 
46 PROTEUTHERIAAND INSECTIVORA, WILLWOOD FORMATION, WYO 

Members of the Wind River Formation. The Almagre and other San 

Jose Formation specimens, however, show a number of consistent 

differences that suggest that they may belong to a separate species. 

The upper molars in AMNH 48177 (from the San Jose Formation) are 

relatively shorter and less squared, and they appear to have more 

acute cusps than in either of two upper dentitions from the Willwood 

Formation (YPM 23077 and 30655). Moreover, the Willwood specimens possess an M1 that is larger than M2

, a relatively smaller M1 

mesostyle, a straighter, less V-shaped M2 ectoflexus, and relatively 

shorter M1- 2 preprotocrista and postprotocrista. 

In the lower dentition, P 4 in Willwood M nitens generally has a less 

well basined talonid than in San Jose or Almagre specimens, though 

this feature is somewhat variable. This talonid construction is essentially the same as that seen in UCMP 44106 (McKenna, 1960a, fig. 

25) from the Four Mile fauna, and TTU-P 4211 from the Lysite Member of the Wind River Formation. 

YPM 30655 (pl. 5, figs. 3, 4; pl. 6, fig. 1) is an associated left P:-M~ 

(prepared from occlusion) that differs from typical Willwood, Wind 

River, and Four Mile M nztens in the greatly reduced, nearly absent, 

P 4 metaconid. The heel of P 4 is short and unbasined (no cristid obliqua) as in the type of the species, TTU-P 4211, AMNH 48174, and 

most of the other Willwood specimens, and the faint metaconid is 

probably an individual aberration. 

Teeth of Macrocranion nztens from low in the Willwood section (for 

example, YPM 30651, 30553, 30597; at the 145-, 180-, and 240-m 

levels) are smaller than teeth from higher stratigraphic levels (for example, YPM 23087,27941, 23077; at the 560-,590-, and 620-m levels). 

Measurements are given in table 4. 

In the Willwood Formation of the central Bighorn Basin, M nitens 

is known from the uppermost part of the lower Gray Bull zone to the 

upper part of the Lysite zone (fig. 18). In the No Water Creek area 

(Bown, 1979), the species occurs at localities between the 30- and 

120-m levels; all are early Graybullian in age. The stratigraphic position of the type specimen is uncertain, but it is probably from the 

middle or upper Gray Bull zones. 

Scenopagus hewettensis, sp. nov. 

Etymology.-For Donnel Foster Hewett, a pioneer geologist of the 

Bighorn Basin region. 

Holotype.-UW 8998 (adapisoricid indeterminate of Bown, 1979, 

fig. 43e), left PrM1• 

Locality.-UW locality V -73020, lower part of Willwood Forma-
ORDER INSECTIVORA 47 

tion (97-m level of Sand Creek facies), early Graybullian, sec. 9, 

T. 46 N., R. 91 W., Washakie County, Wyo. 

Hypodzgm.-The type and possibly UW 9738, 10450. 

Dwgnoszs.-Size of Scenopagus edenensis, larger than S curndens, 

S pnscus, and Talpaumdes dartoni, gen. et sp. nov. (Seep. 53.) P4 

relatively narrower than in S edenenszs, and talomd better developed 

with distinct hypoconid, entoconid, and cristid obliqua P4 paraconid 

arises high on anterior face of trigonid as in Scenopagus, not low as in 

Leptacodon (sensu stricto); and talonid of M1 broader than trigonid in 

contrast to last genus. 

Discusswn.-Bown (1979) referred the type of S. hewettenszs and 

five other specimens to an indeterminate adapisoricid species. Further comparisons convince us that this specimen represents a new, 

relatively generalized species of Scenopagus. Referral of the remainder of the proposed hyopdigm IS only tentative (especially for 

the upper teeth) and must be confirmed by the recovery of more comTABLE 4 -Measurements of teeth of Macrocramon mtens from the WUlwood Formatwn 

(Values m millrmeters x, tooth present but damaged Leaders ( ) md!cate no specrmen] 

Museum P.L P.w P,L P,W M,L M,W M1L M.w M1L M.w Nos 

Peabody Museum, Yale Uruver&Jty (YPM) 

23087 X 160 178 124 

24380 085 065 163 111 188 160 X 168 

27941 180 120 X X 195 165 

30443 X 174 185 176 X 147 

30553 X 132 150 127 

30622 190 135 

30651 152 142 159 150 155 112 

30654 175 155 175 160 

30655 168 109 217 160 2 01 160 195 124 

30657 160 105 X X X 155 

The Geological Museum, Uruver&Jty of WyoDUng (UW) 

7057 1.75 135 

8996 085 055 160 100 

9640 160 130 

9690 160 105 

P'L P'W M'L M•W M"L M"W 

Peabody Museum, Yale Uruver&Jty (YPM) 

23077 1 70 2 40 180 260 X 2 65 

30597 124 165 142 186 

30655 152 205 219 2 49 191 2 42 

The Geologtcal Museum, Uruver&Jty of WyoDUng (UW) 

9641 170 2 20 
48 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

0 

POSITION ABOVE WILLWOOD FORMATION-FORT UNION FORMATION 

CONTACT, IN METERS 0 

0 0 0 0 0 0 0 0 0 0 0 0 0 N M ~ ~ m ~ 

I I I I I _I ~ 

Lower I M1ddle I Upper Gray I Lys1te I Lost Cabm 

Gray Bull zone I Gray Bull zone I Bull zone I zone I zone 

• !Palaeoryctes sp I I ! 

Palaeoryctes sp • let Pararyctes sp, poss1bly new I I 

0 

0 

CXl 

I 1 I I 1 1 1

Dtde/phodus 

--- Dtdelpho~us absarokae I I I absarokae 

i I I Prodta~odon I I I taurtcmeret -------~ Prodtacodon taurtpmeret 1 1 

I + Prodtacodon sp I I 

I I +I__ IPaletctops 

I 1 1 1 btcuspts 

1 ?r- + Palaeostrropa mcerta, sp, nov 

1 1 1 Palaeosmopa 

' veterrtma 

I I I Palaeosmopa !i.ttreola I I I I - Pa/aeosmopa lu~reola 1 1 I 

1 IApatemys chardmt I 

I I I I -- Apatemys fhardmt I 1 

1 1

1 I 1

Apatemys 

I I bellu/us ~---------- Apatemys kaytl 

I 1 I I ---- Apate"?ys kayt 1 1 1 

\ 1 -t Apatemys rodens 

I I Matrocranton 

I 1 I lmtens ---- Macrocramon nttens I 1 1 

-- Scenopagus hewettensts, sp, nov I I 

-- Scenopagu1 sp I I I 

I I I I 

t Talpavus cf Talpavotdes ntttdus (Knshtalka, 1976a, p 24) I I I 

--1 Talpavotdes dartont, gen et sp nov I 

--------1 Talpavotdes dartoAt I I 

I I I I -- dormaalud, sp 1

A 1 1 I 

o Eo/estes stmpsonr, gen nov I I I 

0 cf Letpsa1olestes sp j : : 

-- Letpsanol~stes stegfrtedtt 1 1 1 

1 + cf ,"Leptacodon" Jepsent 1 

--Ponttfactor sp I I+ Ponttfactor ~p (AMNH 15103) 

I I I I ---- Plagtocten1

odon krausae I 1 1 

• PlagfOCtenodon savaget, sp nov I I 

---- Plagtoctenotdes mtcrolestes I I I 

I I I I • Centfodon patratus, sp1 

nov 1 I 

~ --------r---e Centrtodon neasha"!t, sp nov 

0 Parapternodus anttquus, gen et sp nov I I 

: • ?lnsect1vora, ;gen et sp md;etermmate J 

FIGURE 18 -Chart showmg stratigraphic ranges of msecttvores and proteuthenans 

from the Willwood Formation Sohd hnes denote ranges for Elk Creek facies, 

dashed hnes denote ranges for Sand Creek facies of Bown (1979) 
ORDER INSECTIVORA 49 

plete materials and associated upper and lower teeth. The distinctive 

characters of P 4 in the type specimen of S hewettensis are probably 

generalized with respect to Bridgerian species. 

Krishtalka (1976a) recognized Scenopagus curndens as the thenonly-known Wasatchian species of Scenopagus S hewettens~s differs 

from S. curndens in Its much larger siZe and more molarized P4• The 

only known P4 of S. curtidens (Bown, 1981) is premolariform and differs from that in a tentatively referred upper tooth of S hewettens~s 

in the absence of a metacone. Referred specimens of S hewettensis 

are known only from the early Graybullian Banjo quarry (70-m level, 

Sand Creek facies). 

Measurements.-Type specimen (mm): P .. L=1.70, P .. W=1.06, 

M1L=2.00, MtWTn=1.35, MtWTal=1.45. 

Scenopagus sp. 

Referred spec~mens.-YPM 26796, 30614, UW 9595, 9611, 9638 

(Bown, 1979, fig. 42c), 9662, 9695, 9699, 9713, 9720, 9729, 10422. 

D~scusswn.-This sample contains at least two species of 

Scenopagus, at least one of which is probably new; however, the 

material is not adequate to name them or to confidently assign them 

to known species. Two specimens of semimolariform P" belong to one 

of these species, and one of these (UW 9638) is associated with a ps 

and an M2 of unequivocal Scenopagus morphology. Bown (1979) 

referred UW 9638, among others, to cf. Scenopagus sp., probably 

new, and it is now relatively certam that P4 (m S hewettensis) and P4 

were semimolariform in at least some early Wasatchian species of 

Scenopagus, m contrast to all known Bridgerian species 

The molars closely resemble their size counterparts in Scenopagus 

edenens~s (for example, YPM 26796), S curtidens (for example, YPM 

30614), and S pnscus (for example, UW 9695) S edenens~s and S 

pnscus are elsewhere known only from rocks of late Wasatchian and 

Bridgerian age. However, Krishtalka (1976a) has reported S curndens from the early Wasatchian Four Mile fauna It is unlikely that 

any of these species are represented in the sample from the Willwood 

Formation. 

Scenopagus sp. is thus far known only from one locality in the central Bighorn Basin Elk Creek section, where it occurs in the lowest 

sampled level of the middle Gray Bull zone (200-m level). In the Sand 

Creek facies, Scenopagus sp. is known from eight localities, six of 

which occur between the 30- and 81-m levels; the other two sites are 

of uncertain stratigraphic position. The Sand Creek localities yield an 

early Graybullian fauna 

Measurements.-Given in table 5. 
50 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO. 

T ft.J3LE 5.-Measurements of teeth of Scenopagus sp. from the Willwood Formation 

[Values in millimeters. Leaders (-1 indicate no specimen] 

Museum M,L M,W M,L M,W M8L M.w P•L P•w M2

L M'W Nos. 

The Geological Museum, University of Wyoming (UWI 

9595 .... 1.60 1.25 1.60 1.10 

9611 .... 1.85 1.35 1.80 1.20 

9638. ' .. 1.65 1.95 1.55 1.95 

9662 .... 1.50 2.05 

9695 .... 1.40 1.15 

9699 .... 1.50 1.05 

9713 .... 1.55 1.20 

9720 .... 1.50 1.20 

9729 .... 1.40 1.50 

10422 ... 1.45 1.05 1.50 1.10 

Peabody Museum, Yale University (YPMI 

26796 ... 2.05 1.45 

30614 ... 1.65 1.10 

Talpavoides, gen. nov. 

Etymology.-Greek i?ides; like, having the form of; in allusion to 

superficial similarities to Talpauus. -

Type.-Talpauoides dartoni, sp. nov., and only known speCies. 

Diagnosis."P4 smaller with respect to M1 than in Scenopagus, 

Macrocranion, or Plagioctenodon but semimolariform iD contrast to 

former two genera and Talpauus. P4 talonid basin weak and with 

poorly formed cristid obliqua in contrast to Plagioctenodon, but both 

structures more strongly developed than in Talpauus. M1> M2> M3 

in contrast to all above genera, and M1_2 entoconids tall, acute, and 

slightly displaced lingually. Molar cristids obliqua join base of 

metaconid lingually, and molar entoconids situated at posterolingual 

talonid margins as in Plagioctenodon, not more anteriorly as in most 

other nyctitheriids. 

Talpavoides dartoni, sp. nov. 

Plate 6, figures 3, 4 

Etymology.-For Nelson Horatio Darton, a pioneer geologist of the 

Bighorn Basin region. 

Holotype.-UW 9624, fragment of right ramus with PrM2 (pl. 6, 

fig. 4), UW locality V -73022 (Slick Creek quarry), lower part of 

Willwood Formation, Sand Creek facies (46-m level), early Graybullian, sec. 1, T. 46 N., R. 92 W., Washakie County, Wyo. 
ORDER INSECTIVORA 51 

Hypodigm.-The type and UW 6974,6999,7005,8586,8993,9000, 

9597 (pl. 6, fig. 3), 9600, 9610, 9613, 9618, 9623, 9635, 9666, 967 4, 

9675, 9689, 9697, 9700, 9701, 9704, 9711, 9718, 9722, 9723, 9726, 

9728, 9752, 10423, 10448, possibly 9741, 10454, YPM 30544, 30617, 

30643, 31168. 

Dwgnoszs.-Only known species, same as for genus. 

Dzscusswn -The more premolariform P 4 (particularly the talorud 

reduction), the reduction of P4 relative to M1 m s1ze, the progressive 

size decrease of the molars from M1 to M3, and the position of the 

molar entoconids indicate placement of this form m the Erinaceomorpha. Though the M1_

3 size ratio is reminiscent of that in the 

erinaceids, the remainder of the morphology supports inclusiOn of 

Talpavoides in the Dormaaliidae. 

From Bridgerian and Wasatchian Talpavus, Talpavozdes IS distinguished by its better developed P 4 talonid basm, Its shorter P 4 

metaconid (the P4 metacorud and protocorud are equal in height in 

Talpavus nztulus), and by the M1 through M3 size ratio The cristid 

obliqua of M1_2 Is also more acute in Talpavoides, and the molars, correspondingly, appear to be more exodaenodont than in Talpavus 

Krishtalka (1976a) referred several specimens from the Huerfano, 

Green River, and lower Willwood Formations to Talpavus cf. nztulus 

The Willwood specimens (for example, CM 31180) differ from Talpavoules in most Talpavus-like features, including the taller P 4 metacorud, 

a less well defined heel on P 4, a shghtly more compressed M2 trigonid, 

and the lack of a well-defined molar size gradient. The former three of 

these characters are probably derived With respect to the teeth in 

Talpavoides, and the last character is probably generalized 

Talpavoides is the most suitable of the generahzed dormaaliids for 

possible Inclusion in the ancestry of Talpavus Selection favoring the 

relative increase in siZe of M2 relative to M1 or decrease in size of M1 

relative to M2, coupled with further reduction of the P4 talonid and increase in relative size of the P 4 metaconid, would be required to derive 

Talpavus nztidus directly from a population of Talpavozdes dartonz. 

Considerable premolarization of P 4 must have taken place at some 

point in the lineages of Scenopagus, Macrocranion, and Talpavus if 

PU 18688 (seep. 44) had anything to do w1th the later Wasatchian 

and Bridgerian radiation of dormaaliids. As indicated above for 

Scenopagus hewettenszs and Scenopagus sp., P: premolarization was 

a characteristic trend in the lineages of that genus. 

From Macrocranion, Talpavozdes differs in its much smaller siZe, 

its relatively narrower P4, taller trigoruds and taller, more acute 

molar cusps, greater exodaenodonty of the molars, and the molar-size 

gradient. The taller molar entoconids and sharper cusps are probably 

generalized features relative to Macrocranwn, whereas the exo-
52 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

daenodonty and posteriorly smaller molars are specializations that 

preclude this genus from a close relationship to Macrocranlon. 

Talpavoides dartonl is known from only two localities m the Elk 

Creek section of the Willwood Formation, where it occurs in the lower 

Gray Bull zone at the 140- and 180-m levels. In the Sand Creek facies, 

this taxon is found at 15 localities between the 24- and 180-m levels. 

The 180-m level m the Sand Creek facies is the lowest occurrence of 

the adapid primate Pelycodus tngonodus in these rocks (Bown, 

1979), whereas this animal first appears at the level of locahty 355 

(240-m level) in the Elk Creek section T dartonl, therefore, occurs in 

the lower Gray Bull zone of the Elk Creek section, but in the lower 

Gray Bull through the lowest part of the middle Gray Bull zones in 

the Sand Creek facies. 

Measurements.-Given in table 6. 

dormaaliid, sp A 

Plate 6, f1gure 5 

Referred specimens.-UW 7048, 9627 (pl. 6, fig. 5). 

Diagnostic characters.-Molars strongly exodaenodont, more so 

than in Scenopagus, Talpavus, or Macrocranwn. M2_

3 trigonids 

strongly compressed anteroposteriorly, and metaconid and entocorud 

markedly taller than protoconid and hypoconid, respectively. Hypoconulids large, close to entoconids. Entoconids trenchant and deflected lingually and talonid notch acute. Ms relatively unreduced in 

comparison to M2. 

Dlscussion.-This species is known from only two complete teeth, 

but the characters cited previously appear to be diagnostic. The 

trigonid structure is remiiliscent of that in Talpavus; however, the 

talonids are wholly dissimilar. Macrocranwn, conversely, has tall, lingual entoconids and large, somewhat lingual hypoconulids, but 

molars of M nitens are less exodaenodont and have less trenchant 

cusps and less compressed trigonids. Better material is needed to 

meaningfully assess the relations and significance of this animal. 

Dormaaliid sp. A is known only from the early Graybullian Sand 

Creek facies of the Willwood Formation, where it occurs at two localities at the 30- and 46-m levels. 

Measurements.-(mm): UW 7048: M2L=1.20, M2W=0.95. UW 

9627: M9L=1.17, M9W=O 77. 

Family ERINACEIDAE 

Eolestes, gen nov. 

Etymology.-Greek eos; dawn, and Greek lestes; robber. 
ORD~R INSECTIVORA 53 ~ ... : ., 

TABLE G.-Measurements of teeth ofTalpavoides dartoni from the Willwood Formation 

[Values in millimeters. Leaders(-) indicate no specimen) 

Museum P4L P.w M,L M,W M,L M,W M8L MaW Nos. 

The Geological Museum, University of Wyoming (UW) 

6974 0 0 0 0 0 0 0 1.09 0.65 

6999 0 0 0 0 0 0 0 1.05 0.59 1.37 0.90 1.21 0.96 

7005 •• 0. 0 •• 1.13 .68 

8586 0 0 0 0 0 0 0 1.35 .85 1.10 .55 

8993 ••• 0 0 •• 1.22 .92 

9000 0 0 0 0 .. 0 

i.oo~ ,- ---r.i.5 .71 

9597 0 0 0 0 0 0 0 1.30 1.14 .70 

9600 0 0 0 0. 0 0 1.10 .73 1.37 1.00 

9610 0 0 0 0 0 0 0 1.18 .90 

9613 0 0 0 0 0 0 0 1.22 .80 1.10 .60 

9618 0 0 0 0 0 0 0 1.10 .90 

9623 0 0 0 0 0 0 0 1.19 '.88 1.12 .66 

9635 0 0 0 0 0 0 0 1.28 .89 1.22 .82 

9666 0 0 0 0 0 0 0 1.22 .90 

9674• 0 0 0 0 0 0 0 1.20 .75 

9675 0 0 0 0 0 0 0 1.00 .68 0 0 0 

9689 0 0 0 0 •• 0 1.14 .65 1.24 .84 

9697 0 0 0 0 0 0 0 1.00 .60 

9700 0 0 0 0 0. 0 1.21 .81 

9704 0 0 0 0 0.0 0 1.10 .69 

97-11 ••••• 0 0 1.21 .94 

9718 0 0 0 0 0 0 0 1.07 .60 - 9722 0 0 •• 0 •• 1.15 .87 

9723 1.06 .56 

9726 0 0 0 0 0 0 0 1.00 .57 

9728 0 0 0 0 0 0 0 1.10 .80 i.3i 0

9752 0 0 0 0 0 0 0 1.05 .65 .76 

10423 •••• 0. 1.40 .95 1.20 .80 

10448 0 0 0 0 0 0 1.35 1.05 1

10454 0 0 0 0 0 0 

~ 

Peabody Museum, Yale University (YPM) 

30544 . 0 0 0 0 0 1.50 1.05 

30617 0 0. 0 0 0 1.20 0.95 

30643 0 0 0 0 0 0 1.20 0.75 

31168 0 0 0 0 0 0 1.10 .75 

1

UW number 10454: M'L=1.40-1.45 (N=2); M'W=l.S0-1.90 (N=2)o 

Type.-Eolestes simpsoni (Bown, 1979, p. 61), only known species. 

Diagnosis.-P4 talonid more reduced than in Leipsanolestes, "Leptacodon" jepseni, most Macrocranion, and Talpavus. P4 1arger with 

respect to M1 than in Entomolestes or Talpavus and with a. more 

lingual paraconid than in these species. P 4 trigonid longer relative to 

talonid than in Scenopagus, developed about as in M.acrocrtinion and 

Leipsanolestes. P4 metaconid smaller relative to protoconid than in 

Talpavus or Scenopagus, about same as in Leipsanolestes. Molar 

talonids narrower than in Macrocranion or Scenopagus, and molar 

entocristids tall, as in soricids (forming mure) as in Entomolestes, 

taller than in Talpavus, Leipsanolestes, Litolestes, Scenopagus, and 
54 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

"Leptacodon" jepseni. Molar paraconids more cuspidate (less shelflike) than in Macrocranion or Lezpsanolestes, and trigonids more 

anteroposteriorly compressed than in Macrocranion. M1 larger than 

M2 in contrast to many dormaaliids, and molars more exodaenodont 

than in Lztolestes, Leipsanolestes, Macrocranion, or Talpavus. 

Cristid obliqua JOins metaconid and metaconid twinned, in contrast 

to all above forms. 

Eolestes simpsoni (Bown, 1979) 

Plate 6, figure 6, plate 7, f1gure 1 

Synonym.-Lezpsanolestes szmpsonz Bown (1979, p 61). 

Holotype -UW 9616, right P..-M2 (Bown, 1979, fig. 42b), UW locality V-73041, lower part of Willwood Formation, Sand Creek facies 

(about 30-m level), early Graybullian, sec. 24, T. 46 N., R. 92 W., 

Washakie County, Wyo. 

Hypodigm -The type and YPM 35156 (pl. 6, fig. 6; pl. 7, fig. 1). 

Diagnosis. -Only known species; same as for genus. 

Measurements.-(mm): UW 9616 (type): P4L=1.18, P4W=0.81, 

M1L=1.43, M1W=O 97, M2L=1.19, M2W=0.91. YPM 35156: 

P4L=1.30, P4W=0.80, M1L=1.55, M1W=l.OO, M2L=1.38, 

M2W=l.OO. 

Dzscusswn.-Bown (1979) placed the type of Eolestes in Lezpsanolestes, the closest morphologic counterpart of the new genus. 

Restudy of the type specimen and YPM 35156 and comparisons with 

new and better materials of Leipsanolestes szegfnedn and Entomolestes grangen (Krishtalka, 1976a; Krishtalka and West, 1977) convince us that both Willwood specimens represent a new genus of 

erinaceid but one that is most closely related to these two mammals. 

Eolestes is retained in the Erinace1dae on the basis of (1) premolar 

construction, (2) the more cuspidate paraconid on M1 than on M2, (3) 

the rectangular molars, (4) the high molar entocnstids, (5) M1 larger 

than M2, and (6) very flat hypoconids. 

In contrast to Leipsanolestes siegfriedti, the molars are strongly 

exodaenodont, the hypoflexid is deep, the P 4 talonid is more reduced, 

the molar entocristids are taller, the paraconids are more cuspidate, 

and the cristids are more oblique and are connected to the metaconid. 

All these features, except the more cuspidate paraconids, are characters that are probably derived relative to the condition m Leipsanolestes, and all, with the exception of the connection of the cristid 

obhqua and metaconid, parallel the developments in Entomolestes 

grangeri. 

From Entomolestes, Eolestes is distinguished by the last feature, 

its larger P4 with respect to M19 its less oblique (more anteroposterior) 
ORDER INSECTIVORA 55 

alinement of the P 4 prevallid (because the paraconid is more anteriorly removed from the metaconid), the less well developed M2 entocristid, and the deeper hypoflexids. The relative size of the P 4 and 

the molar entocnstid development in Eolestes are probably generalized with respect to Entomolestes, and the P4 trigonid construction 

(similar to that in Leipsanolestes) may also be generalized for some 

early Tertiary erinaceids. The cristid obliqua-metaconid confluence 

and the resultant deep hypoflexid is unique among the early Tertiary 

erinaceids and is convergent to some extent With the conc:htion m 

some talpids (for example, the Desmaninae). This feature is doubtlessly derived with respect to both Leipsanolestes and Entomolestes 

and suggests that Eolestes is removed from the ancestry of the latter 

genus. 

cf. Leipsanolestes sp. 

Referred spec~men.-UW 9672, a left M3 

Discussion.-This tooth is related to Leipsanolestes and the erinaceids m the possession of bulbous cusps in conJunction with a short 

trigonid, by a shallow hypoflexid, by a strongly developed paraconid 

shelf without a cuspidate paraconid, by a low, flat hypoconid and 

taller entoconid, and by its general exodaenodont configuration. The 

tooth is distinguished from that in Le~psanolestes seigfriedti by its 

15-percent larger size, a less lingually deflected metaconid, a relatively deeper talonid basin, and a less anteriorly attenuated paraconid shelf. The tooth is less similar to M3 m L~tolestes and does not 

closely resemble molars of Eolestes, "Leptacodon" Jepsen~, or Entomolestes grangen. It is possible that the specimen represents a 

large, undescribed species of Letpsanolestes that was approXImately 

coeval with Willwood L siegfnedh; however, the material is inadequate to positively ascertain its affinities within the Erinaceidae. 

Cf. Le~psanolestes sp. is known from only one locality, at the 88-m 

level of the Sand Creek facies where the only specimen was found in 

association with an early Graybullian fauna 

Measurements -(mm): M3L=l.75, M3W=l 20. 

cf. "Leptacodon" Jepsen! McKenna, 1960a 

Plate 7, f1gure 5 

Referred spec~men -YPM 30559, fragment of left ramus w1th PrM1 

and trigonid of M2 (pl 7, fig. 5). 

2

M J Novacek, T M Bown, and Dav1d Schankler (unpub datal mclude "Leptacodon" 

Jepsem McKenna (1960a) m a new genus 
56 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

Dzscusswn.-This specimen appears to be a large variant of 

McKenna's (1960a) "Leptacodon" Jepsenz, from which It is nearly inseparable on morphologic grounds (YPM 30559 IS larger) M1 in the 

Yale specimen has a slightly more anteroposteriorly compressed 

trigonid than occurs in the type of "L "jepsenz. 

"Leptacodon" Jepsenz was established on the type lower Jaw with 

P2-M2 and two other damaged teeth from the Four Mile Creek area of 

northwestern Colorado. Delson (1971) referred four additional 

specimens to this enigmatical species and believed that it is probably 

more closely related to his concept of the adapisoricids than to Leptacodon. This conclusion was later endorsed by Krishtalka (1976a), 

who did not comment further on its affinities. 

Of Delson's referred matenals, only AMNH 56313 (an M3) is probably referable to "L " Jepsen" AMNH 56311 and 56312 are nyctitheriids and closely resemble Leptacodon tener and small specimens 

of Plagioctenodon krausae M3 is not preserved in the type of ''L '' 

Jepsenz, and the reference of AMNH 56313 to that taxon is provisional and is based on its having a lingual hypoconulid that is not 

expanded posteriorly as in Entomolestes grangeri. 

AMNH 56314 and 56315, also from the Powder River local fauna 

and With labels bearing "Leptacodon", most closely resemble 

Plagwctenodon savagez, sp. nov. (seep. 61), differing from it only in 

the following trivial respects: (1) the teeth are slightly larger, (2) the 

P4 talonid is relatively longer and somewhat more squared, (3) the 

molar talonids are more roundly basined, and (4) M1 has a more continuous entocristid. The M1 trigonid is not preserved in the type of 

Plagwctendon savage1, however, m P krausae the trigonid is more 

anteroposteriorly compressed than it is in AMNH 56314. 

We agree with Delson's (1971) suggestion that "L "jepsenz is in or 

near the ancestry of Bridgenan Entomolestes grangeri McKenna 

(1960a, p. 53) also observed that "Leptacodon" jepsenz is 

"Entomolestes-like." P4 is the most diagnostic tooth in both species 

and IS typified by a very large, anteriorly proJecting paraconid that 

arises very high on the face of the trigonid, m conjunction with a 

short, poorly basined talomd (pl. 7, fig. 5). The molars of "L "Jepsenz 

differ from those of E grangeri in size (type materials of "L "jepsenz 

are smaller), in having a smaller P3 to P4 size ratio, in the shorter, 

more curved prevallid, in the slightly larger and more linguolabially 

compressed entocristids in Entomolestes, and in the somewhat more 

exodaenodont configuration of the molars in the last genus. 

"L "jepsenz differs from Eolestes in (1) a smaller P4 with respect to 

M17 (2) the better developed talomd basin in "L "Jepsenz, (3) the more 

poorly developed molar entocristids, (4) the lack of connection of the 

cnstid obliqua to the metaconid, and (5) the presence of a more acute 

paracnstid notch m "L." jepsenz. These observations support our 
ORDER INSECTIVORA 57 

contention that "Leptacodon" jepsem, is morphologically closer to 

Entomolestes grangen than to either Eolestes or Lezpsanolestes 

Krishtalka and West (1977) described additional specimens of Entomolestes grangen (for 68 years, the type was the only published 

specrmen), and to the hypodigm we add AMNH 987 42 (pl. 7, figs. 2, 4) 

from rocks of late Bridgerian age near Tabernacle Butte. This specimen (identified by James Honey) preserves P r M3, and, aside from 

the type, is the most complete undamaged lower dentition. Interestingly, the highly distinctive P4 construction of both "L "jepseni and 

E. grangeri exists (in modified form) in AquitanianAmphechinus, living Erinaceus, and several other advanced ennaceines (see, for example, figures in Rich and Rich, 1971; Rich and Rasmussen, 1973). 

Measurements.-YPM 30559 (mm): P4L=1.20, P4W=0.80, 

M1L=1.40, M1W=l.05. 

Order INSECTIVORA 

Suborder SORICOMORPHA 

Famlly NYCTITHERIIDAE 

In his review of the early Tertiary nyctitheriids of North Amenca, 

Krishtalka (1975, 1976b) considered the following characters to be 

diagnostic of the family: (1) the presence of a vesp1form constriction 

between the molar trigomds and talonids, (2) presence of a 

semimolariform P4 with a low paraconid projecting out from the 

anterior part of the base of the protoconid, (3) relatively high (tall) 

molar hypoconids that did not become flat with wear, (4) unreduced 

molar hypoconulids, and (5) deep molar hypoflexids. In contrast, the 

sensu lato adapisoricids (dormaaliids of this report) were believed to 

be charactenzed by (1) progressive premolarization of P4, (2) rectangular molars with low, relatively bunodont cusps, (3) " * * * a 

compressed, lophid-like paraconid that never JOins the metaconid * * * " on M1_3, (4) wide molar talonids with a high entoconid 

and lower hypoconid, (5) median, or barely lingual and unreduced 

molar hypoconulids, and (6) a shallow hypoflexid with the cristid obliqua meeting the postvallid labial to the protocristid notch. In Ius 

discussion of "Leptacodon" jepseni, Krishtalka (1976b, p 17) also mferred that the position of the P 4 paraconid high on the anterior face 

of the trigonid was a more typical adapisoricid (sensu Krishtalka) 

than nyctitheriid character. From our comparisons of-early Tertiary 

dormaaliids, erinaceids, and nyctitheriids, we offer the following supplementary notes and qualifications. 

First, the P4 paraconid is relatively as large and arises equally low 

on the tngonid in Mckennathenum (Adapisoricidae, according to 

Krishtalka, 1976a; for example, AMNH 35955, PU 17722) as it does 
58 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

in any species of Leptacodon or Nycnthenum If Mckennatherium is 

to be retained m the Dormaaliidae (the diminished probability of this 

association is discussed on p. 42-44), the relative height of the P 4 

paraconid is of little diagnostic value. Indeed, the position of this 

cusp on P4 in at least some "Leptacodon" munusculum (for example, 

PU 20026), Nycnthenum velox (for example, YPM 14936), 

N. seronnum (for example, CM 13722), and Pontifactor (for example, 

AMNH 15103) is much higher on the trigonid than it is in Mckennatherium and most closely resembles the positions in the dormaallids Talpavus and Macrocranion. 

Second, other than the deep hypoflexid, we see no particularly 

overt vespiform constriction between the molar trigonids and 

talonids in "Leptacodon" munusculum, "Leptacodon" packz, or 

Nyctithenum velox. Among known nyctitheriids, tlus character is 

perhaps best developed in Ponnfactor; however, no nyctitheriid has 

this constriction so explicitly developed as m Macrocranwn or dormaallid sp. A. (p. 52). This constriction owes its visual properties to a 

deep hypoflexid in combination with a lingual leaning of the entoconid. We do not believe that the degree of constriction of the talonidtrigonid juncture is particularly diagnostic for nyctitheriids when 

compared to its development in both dormaaliid~ and erinaceids. 

Third, the relatively high hypoconids considered to be a diagnostic 

feature of trhe nyctitheriids by Krishtalka are more evident 1n Pontifactor and some Nycnthenum than they are in Leptacodon. In some 

instances, this feature results not from unusually tall hypoconids but 

from relatively short entoconids. Moreover, in all the forms believed 

to be nyctitheriids by Krishtalka (1976b), excluding Satuminia beata 

and Leptacodon tener, the entoconids are both relatively low and are 

situated slightly more anteriorly than in adapisoricids. This appears 

to be a significant shared and derived character uniting "Leptacodon" munusculum and at least some "Leptacodon" packz with 

Pontifactor and middle Eocene nyctitheriids. In "L "packi and in at 

least some specimens of "L" munusculum (for example, PU 20026), 

Ponnfactor sp. (see p. 59), Nycnthenum velox, and N seronnum, the 

entoconid is also somewhat linguolabially compressed and is connected to the base of the metaconid by a minor entocristid. The development of the entocristid is greater than m any of the dormaaliids 

and is convergent with that in some erinaceids and in some of the distant nyctitheriid relatives-the shrews. 

These differences suggest the division of the Nyctitheriidae into 

two groups: one containing Leptacodon tener, Plagioctenodon, Plagwctenoides, and Satuminia beata; the other with "Leptacodon" 

munusculum, "Leptacodon" packz, Saturninza gracilzs, Amphzdozotherium, Pontifactor, and Nyctitherium. A complex of apparent crossing characters, however, masks the significance of these 
ORDERINSECTIVORA 59 

shared attributes and indicates that these do not constitute two 

natural phylogenetic groups. 

Krishtalka (1976b) observed that "Leptacodon" munusculum 

might belong in Pontifactor and that "L." pack~ llllght more aptly be 

placed in Nyctitheriu m This concept independently recognizes the 

morphologic discrepancies between Leptacodon tener and other 

species referred to this genus; however, we do not recommend these 

synonymies. 

"Leptacodon" pack~ Jepsen (1930b) further differs from more 

typical nyctithenids in the extremely tall and trenchant P 3_

4, and in 

having a conspicuous labioinferior depression of the enamel beneath 

the P 4 hypoflexid, and differs from Nyctitherium in having the molar 

trigonids relatively long with respect to the talonids. P 3_4 are reminis· 

cent of the general morphology of those teeth in early geolabidids, 

such as Centetodon patratus, sp. nov. (p. 64), or C pulcher The 

molars of early Centetodon, however, do not particularly resemble 

those of "L" packi, but the premolar similarities suggest that the 

latter species may have had a more generalized, central position in 

the ancestry of early Tertiary soricoids, rather than a more special· 

ized position as a possible synonym of Nyctitherium. 

Pontifactor sp. (Krishtalka, 1978b, p. 23) 

Referred spec~mens.-UW 8584, 9621, 9649, 9681, 9683, 9710, 

9721, 9732, 9733, 10449, 10455, 10456, (see also Bown, 1979). 

D~scussion.-Krishtalka (1976b) transferred Matthew's (1918) 

referred Willwood specimen of Nyctithenum celatum (AMNH 15103) 

to Ponnfactor West (1974). Bown (1979) referred additional upper 

cheek teeth to this animal, under the designation Ponnfactor cf. 

bestiola. 'I'he four additional undescribed specimens at hand (from 

the original hypodigm of Plagioctenodon krausae, see Bown, 1979) 

are smaller but otherwise closely resemble molars in AMNH 15103 

and are here referred to Ponnfactor sp. 

In contrast to both Plagioctenodon and Talpavoides, these lower 

molars possess acute, deep talonid basins, a deep hypoflexid, more 

trenchant cusps, and unreduced hypoconulids, characters that 

Krishtalka (1976b) cited as diagnostic of nyctitheriids. The molars 

(only M1_2 are represented) have the anteroposteriorly compressed 

trigonids, lophid·like and anterolingually flaring paraconids, a large 

medial hypoconulid, and a tiny mesoconid, all typical of Krishtalka' s 

Pontifactor sp. Other than the presence of an eruptive M3, we are 

unable to ascertain by which criteria both Matthew (1918) and 

Krishtalka (1976b) presumed that P4 in AMNH 15103 is deciduous. 

The tooth is broken between the trigonid and talonid, and the talonid 
60 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

has been rotated posterolabially, but its morphology is consistent 

with that in permanent P 4 in other nyctithenids 

Measurements.-(mm), UW 8584: M2L=1.23, M2W=0.90. UW 

9649: M2L=1.12, M2W=0.87. UW 9683: M1L=1.30, M1W=O 92, 

M2L=1.19, M2W=0.85. UW 9721: M1L=1.30, M1W=0.92 UW 9621: 

M1L=1 60, M1W=1.10. UW 9710: M2L=1.35, M2W=0.95. 

COMMENTS ON PLAGIOCTENODON BOWN, 1979 

Bown (1979) erected the genus Plagioctenodon for approximately 

40 lower jaws and several individual teeth in the No Water collection 

from the Sand Creek facies of the Willwood Formation. Owmg to the 

current resurgence of interest in early Eocene faunas in general and 

early Eocene insectivores in particular, many useful comparative 

materials were not available for study at the time of the original 

description of the No Water msectivores, and those observations 

were based principally on comparisons of pubhshed figures, text 

descriptions, and a few casts. Bown (1979) recognized the large 

amount of morphologic variation in the sample referred to 

Plagwctenodon and named only the last genus for the most distinctive specimens. Virtually all of the best of the recently published 

specimens of Paleocene and early Eocene insectivores have now been 

examined and compared with specimens in the original hypodigm of 

Plagwctenodon, and it is now possible to give a more comprehensive 

account of the several mammals originally included in the latter 

genus. 

Bown (1979) believed Plagioctenodon to be an early adapisoricid 

(sensu lato), perhaps most closely allied to the enigmatical "Leptacodon'' jepseni but with several crossing specializations that are 

reminiscent of both early adapisoricids and early nyctitheriids. These 

conclusions are fundamentally changed by this study; "Leptacodon" 

jepsem, is an erinaceid mostly closely related to Entomolestes 

grangen (p. 56), Plagwctenodon (sensu stricto) is a nyctitheriid, and 

the origmal hypodigms ascribed to Plagioctenodon krausae and P cf. 

krausae contain representatives of five species. Four of these 

(Scenopagus sp., Talpavouies dartonz, dormaaliid sp. A., and some 

specimens of Pontifactor sp.) have already been discussed. 

Plagioctenodon krausae Bown, 1979 

Emended hypod"tgm.-UW 7047, 9572, 9587, 9592, 9608, 9620, 

9653, 9682 (holotype, Bown, 1979, fig. 43a), 9684, 9688, 9692, 9696, 

9698,9709,9712,9737, possibly UW 9715,9716,9730, 10377, 10451, 

YPM 31167, 32824. 
ORDER INSECTIVORA 61 

Emended diagnosls.-P2_

3 anteriorly inclined. P2 larger than P3, 

and no diastema separates these teeth. P 4 semimolariform, elongated 

anteroposteriorly, narrow transversely, with paraconid large and 

anteriorly projecting, and arising higher on the anterior face of the 

trigonid than in Leptacodon. P 4 talonid with two or three well-defined 

cusps and well-developed basin. P 4 relatively larger with respect to 

M1 than in Talpavoides. M1 and M2 about equal in size; M3 slightly 

smaller than M2. M1 _2 entoconids significantly taller than 

hypoconids; entoconids do not project lingually and are situated at 

posterolingual margms of molars, not more anteriorly as in some Leptacodon and all Nyctltherium. No vespiform constriction between 

trigonid and talonid of molars. 

Dlscussion.-Plagioctenodon krausae appears to share some of the 

characters discussed above with dormaaliids, as suggested by Bown 

(1979). Particularly relevant here are the shallow molar hypoflexids, 

tall, posterolingual molar entoconids, open talonid notch, and 

relatively minor molar hypoconulids. It appears to us more likely, 

however, that Plagioctenodon is a derivative of Paleocene Leptacodon tener. The P 2_3 constructiOn, P 4 molarizatlon, less compressed 

M1_2 trigonids, broader molar talonids, and acute molar cusps 

(especially the metaconid) argue for close affinity to L tener and the 

earliest nyctitheriids. L. tener, Plagioctenodon, Plagwctenoides 

mlcrolestes (p. 64), and Satuminia beata differ from "L." 

munusculum, Satuminw gracills, Amphldozothenum, and Nyctltherium m having tall entoconids that are situated at the far posterolingual margins of the molars (see previous discusson of the Nyctitheriidae). 

Plagioctenodon krausae is known only from the Sand Creek facies 

of the Willwood Formation where it occurs associated with an early 

Graybullian fauna between the 34- and 88-m levels, inclusive (fig. 18). 

Measurements.-G1ven in table 7. 

Plagloctenodon savage!. sp nov. 

Plate 7, figures 3, 6 

Etymology.-For D. E. Savage, in recognitiOn of his many contnbutions to Tertiary stratigraphy and paleontology. 

Holotype.-YPM 34257, right P3-M2 (pl. 7, figs. 3, 6); only known 

specimen. 

Locallty.-YPM locality 104, lower part of Willwood Formation 

(140-m level of Elk Creek section), early Graybullian, sec. 18, T. 50 N., 

R. 93 W., Big Hom County, Wyo. 

Dwgnosls.-Teeth 35 percent larger than in Plagwctenodon 

krausae and M2 paraconid less cuspidate than in that species. t 
62 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO. _, ----: 

TABLE 1.-Measurements of teeth ---Q{ Plagioctenodon krausae from the Willwood 

FormatWn 

[Values in nilllimeters. ,x, damaged tooth. Leaders (.:...) indicate no specimen) 

Museum PaL P1W P4L P4W M,L M,W MaL MaW MaL M8W Nos. 

The Geological Museum, University of Wyoming (UWI 

7047 .... 1.35 0.70 1.35 0.85 1.40 0.85 1.30 0.85 

9572 .... 1.20 .80 1.50 .95 

9587 .... 1.12 .84 

9592 .... 1.37 .91 1.31 .89 1.29 .71 

9608 .. .. 1.50 .90 

9620 .... 1.18 .66 1.28 .87 

9653 .... 1.30 .85 

9682 .... 0.82 0.48 1.15 .82. 

9684 .... 1.14 .75 

9688 .... 1.23 .97 1.15 .97 

9692 .... 1.17 .66 1.24 .84 1.21 .86 

9696 .... 1.40 .75 X X 1.40 .90 

9698 .... 1.40 .85 

9709 .... 1.45 .80 

9712 .... 1.45 .85 

9737 .... 1.35 .80 1.50 1.10 1.50 1.10 

10377 ... 1.25 .75 

Peabody Museum, Yale University (YPMI 

31167 ... 1.35 .85 

32824 ... 0.95 0.50 1.35 .80 

Museum P'L P•W M'L M1

W M"L M"W Nos. 

The Geological Museum, University of Wyoming (UWI 

9715 ••• 0 ••• 0 0 0 •••••• 1.40 2.00 

9716 •• 0 •••••• 0 0 ••• 0. 2.00 2.30 X X 1.95 X ' 9730 ••••• 0 •••••••••• 1.90 2.60 

1

P2: L=0.95, W=0.42. 

Discussion.-The type specimen of P. savagei, with the exception 

of. its much larger size, is virtually identical to the specimens 

previously referred in this report to Plagioctenodon . krausae. 

Plagioctenodon does not closely resemble Scenopagus and the more 

derived dormaaliids or any erinaceid; and, as observed previously, it 

is probably most closely related to the Leptacodon tener group of 

nyctitheriids. To clarify the varying degrees of semblance of P. 

savagei to earlier described nyctitheriids, the results of our comparisons are abstracted on the following page. 
ORDER INSECTIVORA 63 

Leptacodon tener Matthew and Granger, 1921: 

P savage& P4 IS about 17 percent and M2 about 38 percent larger than m L tener, 

and the P 4 paracomd anses higher on the an tenor face of the tngomd than m that 

species The M2 paracomd IS less cuspidate m P savage&, and the protocnstid notch IS 

at the same level as the paracnstid notch (higher than m L tener) 

"Leptacodon" munusculum Simpson, 1935: 

P savage& IS about 45 percent larger than "L " munusculum, and the P 4 paracomd 

anses higher on the antenor face of the tngomd than m some specrmens of the latter 

species (about as m PU 20026 from Cedar Pomt Quarry, higher than m AMNH 35943 

from Gidley Quarry) The molar entocomds are anterolmgual to the hypoconuhds m 

"L " munusculum P 3 IS relatively lower With respect to P 4 m both P krausae and P 

savage& 

"Leptacodon" packi Jepsen, 1930b: 

P savage& IS about 25 percent larger than "L" pack& P3 IS tall and trenchant m 

"L "pack&, whereas, It IS shorter and tilted antenorly m Plagwctenodon The P4 paracomd Is relatively larger and anses higher on the antenor face of the tngomd m P 

savage& than m "L" pack&, and the M1_2 entocnstids are better developed m "L" 

pack& The M2 paracomd IS more cuspidate m "L "pack&, and the M1_2 entocomds are 

anterolmgual to the hypoconuhds, m contrast to the condition m Plagwctenodon 

Ponnfactor sp. (Knshtalka, 1976b, p. 23-25): 

P savagez IS about 20 percent larger than Pontzfactor sp and has more postenor 

molar entocomds The P 4 paracomd Is much larger and more antenorly situated, ansmg shghtly lower on the tngomd m Plagwctenodon The hypofleXId IS relatively 

deeper and the talomd basm IS relatively deeper and more acute m Pontzfactor sp 

Nycnthenum uelox Marsh, 1872 (pl. 8, figs. 1, 2, this paper): 

Teeth of Plagwctenodon savagez are about 20 percent larger than m N velox P 3 

has a longer paracnstid, a stronger paracomd, and a stronger posterobasal cusp m P 

savage&, and the P 4 paracomd IS much larger and more antenorly removed from the 

metacomd than m N velox The molar hypoconuhds appear to be relatively larger and 

closer to the entocomds m N velox, and the M1_2 entocomds are anterolmgual to the 

hypoconuhds, m contrast to P savagez 

Satummza grac-,l-,s Stehlin, 1940, and S beata (Crochet, 197 4): 

The P4 paracomd IS much stronger m Plagwctenodon than m S beata but IS 

developed much as m S graczlzs The talomds of M1_2 are less reduced with respect to 

the tngomds than m S beata, and the molars are less elongate than m that species 

The M1_

2 entocomds are very small and antenorly situated m Satummw grac&lzs (m 

contrast to both Plagwctenodon and S beata), but the mternal mure of the entocomd 

faces buccally m Plagwctenodon, not anterobuccally as m S beata. 

Amphidozotherium Filhol, 1877: 

The P4 paracomd IS much stronger and IS more antenorly placed m Plagwctenodon 

The P2_

3 constructions are dissimilar, the M1_2 paracomds are less cuspidate and less 

medial, and the entocomds are larger and less antenor m Plagwctenodon 
64 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

Plagwctenodon savagei is a possible derivative of P krausae. 

However, the stratigraphic evidence suggests that these two species 

may have been contemporanes even though they share no localities 

in common. Plagioctenodon is closest to Leptacodon tener among 

known nyctitheriids, as evidenced by the posterior molar entoconids. 

The less cuspidate M1_3 paraconids and the position of the P4 

paraconid are almost certainly derived characters, relative to 

L. tener 

Cf. Leptacodon of Krishtalka (1976b, p. 16) may belong in P 

savage,, but the referred specimens from the Sand Wash Basin of 

Colorado are somewhat larger. At any rate, M1_2 in that species appear to have relatively shallow hypoflexids, a highly molarized P 4, 

and posteriorly situated entoconids (Krishtalka, 1976b, fig. 4). 

Measurements.-Type of P. savagei (mm): P3L=1.25, P3W=0.70, 

P4L=1.70, P4W=l.OO, M~W=1.50, M2L=1.80, M2W=1.55. 

COMMENTS ON PLAGIOCTENOIDES BOWN, 1979 

Plagioctenoides microlestes was erected by Bown (1979, p. 65) to 

accomodate six mandibular specimens of a very small insectivore. At 

the time of its descnption, P mlcrolestes was believed to be a sensu 

lato adapisoricid, largely because of the morphology of P 4• The molar 

morphology, however, seems more consistent with our revised concept of the nyctitheriids .in (1) the trenchant cusps, (2) the deep 

hypoflexid and long cristid obliqua, (3) the unreduced hypoconulids, 

and (4) the relatively tall, piercing hypoconids. If this assessment is 

correct, Plagwctenmdes is the smallest known nyctitherhd and has 

an antemolar dentition most like that of late Ludian Amphldozothenum in the possession of reduced, single-rooted P1_

3 

(Crochet, 1974; Sige, 1977). 

F~Gmuwmm~M~~t~b 

Centetodon patratus, sp. nov. 

Plate 8, figure 3 

Etymology.-Latin patratus. accomplished, the first known early 

Wasatchian species of Centetodon 

Holotype.-UCMP 44954, left PrM2 (McKenna, 1960a, p. 61-63, 

fig. 29); east end of Alheit pocket, Four Mile fauna (early 

Wasatchian), Sand Wash Basm, Colo. 

Hypodigm.-The type and YPM 23088 (pl. 8, fig. 3); possibly also 

UCMP 44957, 44958, 44959 (McKenna, 1960a, p. 61). 
ORDER INSECT 1 VORA 65 

Distribution.-Early Wasatchian, northwestern Colorado, and 

Bighorn Basin, Wyo. 

Dzagnosis.-8ize of Centetodon pulcher and C magnus, much 

smaller than C. wolffi and C neashamz, sp. nov. (infra) and larger 

than other species of Centetodon. P 4 with much better developed 

talonid basin than in C. pulcher, C. new species B and C (of 

Lillegraven and McKenna, unpublished data, as designated by 

Krishtalka and Setoguchi, 1977), C marginalis, or C magnus. P4 

paraconid relatively larger than in C. pulcher or C. new species C, and 

P4 without posteriorly flaring protoconid as inC magnus. P4 longer 

with respect to M1 than in C pulcher, C marginalzs, and C new 

species B. 

Discusswn. -Gentetodon1patratus is the oldest known species currently assigned to this genus or to the Geolabididae. The type and 

other UCMP specimens and the referred Willwood material are all 

associated with undoubted early Wasatchian faunas and 

demonstrate that the peculiar morphology of the cheek teeth in 

Centetodon was established early and persisted in Its general form 

for about 15 million years. C patratus is closest in morphology to C. 

pulcher, a species reported from several localities in the Bridger Formation of southwestern Wyoming (J. A. Lillegraven and M. C. 

McKenna, unpub. data), and possibly from locality VI of the Huerfano Formation (Krishtalka, 1975, p. 98).' 

YPM 23088 differs from the type of C. patratus in having a slightly 

less exodaenodont M1 talonid; damage to several cusps gives the impression that the entoconids are not so lingually inflected as in the 

type. The general sculpture of the teeth in both specimens is quite 

similar, though, and it is highly probable that they represent the 

same species. 

C. patratus differs from C pule her principally in the structure of P 4 

(for example, better developed talonid basm and cristid obhqua, 

larger P4 paraconid, and P4 slightly larger with respect to M1 in C 

patratus). All these characters are probably generalized for the 

genus, if one assumes that there was either a dormaaliid-like or a 

Batodon-like mammal in the ancestry of Centetodon (the latter idea 

was suggested by M. C. McKenna, oral commun, 1974, and by 

McKenna zn Novacek, 1976, p. 33) The morphology of the cheek 

teeth in Centetodon is remarkably uniform in all species P 4 is the 

most diagnostic tooth, with the combination of the very tall, acute 

protoconid-metaconid moiety of the trigonid, the lower but distinct 

and anteriorly projecting paracomd moiety, the steep, flat postvallid, 

and the labial bulge of enamel beneath the hypoflexid being a unique 

construction. These characters appear to have been extremely long 

lived within the Centetodon lineage and have persisted with only rela-
66 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO. 

tively minor structural changes (ratio of P )M1 size, development of 

relatively taller, more acute cusps, overall tooth-size changes) from 

the early Wasatchian through the Chadronian. The occurrence of C. 

patratus is depicted in figure 18. 

Measurements.-Given below in table 8. 

TABLE B.-Measurements of teeth of Wasatchian Centetodon 

· [Values in millimeters. Leaders (-) indicate no specimen] 

Specimen No. P.w M,W M,L 

Centetodon patratus, sp. nov. 

UCMP 44954 (type) ...... 1.95 1.05 2.00 1.40 1.80 

YPM 23088 ............ 1.91 1.17 1.92 

Centetodon neashami, sp. nov. 

YPM 26626 (type) ....... 2.40 1.39 2.52 1.70 

YPM 27011 ............ 2.78 1.52 

YPM 25700 ............ 2.20 1.38 2.29 1.60 

Centetodon neashami, sp. nov. 

Plate 8, figures 4, 5; plate 9, figures 1, 2 

M,W 

1.25 

1.25 

Etymology.-For J. W. Neasham, in recognition of his contri· 

butions to the stratigraphy and sedimentology of the Willwood 

Formation. 

Holotype.-YPM 26626, left PrM1 (pl. 8, fig. 4; pl. 9, fig. 2), YPM 

locality 251, middle part of Willwood Formation (470-m level), late 

Graybullian, sec. 22, T. 50 N., R. 96 W., Big Horn County, Wyo. 

Hypodigm.-The type and YPM 27011 (pl. 8, fig. 5); possibly YPM 

25700 (pl. 9, fig. 1). 

Distribution.-Lower middle Gray Bull and upper Gray Bull zones, 

Willwood Formation, Bighorn Basin, Wyo. 

Diagnosis.-Largest Eocene species of genus; approximate size of 

Centetodon wolffi (J. A. Lillegraven and M. C. McKenna, unpub. 

data). P .larger with respect to M1 than in C. pulcher, C. new species B 

(mentioned in "C. patratus" section), and C. marginalis. P4 with good 

talonid basin, both basin and cristid obliqua better developed than in 

C. pulcher and all later species, about as in C. patratus. P4 paraconid 

relatively larger than in C. pulcher and with more obliquely oriented 

(less longitudinal) cristid obliqua than in C. patratus. P4 cusps less 

acute than in C. marginalis, C. new species B and C, and with more 

erect trigonid than in either C. marginalis or C. magnus. M1 prevallid 
ORDER INSECTIVORA 67 

more transverse (less oblique) than in C magnus. P4 relatively 

broader and M1 trigonid less compressed anteroposteriorly than m C 

new species C. 

n,scusswn.-Centetodon neasham" is closest in its known morphology to Graybullian C. patratus and might be included in that 

species were It not for the profound discrepancy m size (C neasham" 

is 13-42 percent larger m P4, 15-26 percent larger in M1) The type 

specimen and YPM 27011 are the largest specimens, and YPM 27500 

is approximately mtermediate in size and stratigraphic position between the types of C patratus and C neasham1,. If YPM 27 500 were 

eliminated from the hypodigm of C. neashami (its referral is provisional), the size discrepancy is even more marked (23-42 percent for 

P4, 20-26 percent for M1). Both the type of C. neasham" and YPM 

27011 are from relatively high levels of the Willwood Formation 

(4 70-m level and indetermmate upper Gray Bull zone level, respectively); whereas, YPM 23088 (C patratus) is from considerably lower 

(140-m level), and YPM locality 290N (provenance of YPM 25700) is 

almost certainly intermediate (indeterminate level, probably in lower 

part of middle Gray Bull zone). 

Centetodon neashami IS clearly distinct from other samples of 

Eocene and Oligocene Centetodon. Only the unique specimen of Brule 

Formation (middle Oligocene) C wolffi approaches the new species in 

size, and the PrM1 morphology of C neashami is, like that of C 

patratus, more generalized than in known Bridgerian, Uintan, or 

Chadronian species. 

Measurements.-G1ven in table 8. 

Family APrERNODONTIDAE (Matthew, 1910) Simpson, 1931 

Parapternodus, gen nov. 

Etymology.-Greek para: near, beside; in allusion to similarities to 

Aptemodus. 

Type.-Paraptemodus annquus, sp. nov, and only known species. 

Dwgnos,s.-Small aptemodontid, size of Oligoryctes cameronens"s M2 paracristid and postvalhd relatively narrower transversely 

than in Oligoryctes or Aptemodus and developed about as in P 4 of 

Aptemodus and M2 of "Eoryctes" nomen nudum. M2 trigorud less 

compressed anteroposteriorly than in Ol,goryctes and Aptemodus, 

developed about as in "Eoryctes." Postvallid oriented transversely 

on M2, not more anterolingually-posterolabially as in latter three 

forms. M3 postvallid oriented anterolabially-posterolmgually, not 

transversely as in Oligoryctes and Apternodus, or more 

anterolingually-posterolabially as in "Eoryctes." M2 talonid ex-
68 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

panded ventrolabially as in "Eoryctes" and m contrast to condition 

in Olzgoryctes and Aptemodus. M2_

3 lack precingulids, and M3 short, 

apparently without talonid cusp as occurs in Oligoryctes, Apternodus, and "Eoryctes." M2_3 crowns tall and hypertrophied as in 

Olzgoryctes and Aptemodus, not relatively low as in "Eoryctes." 

Prevallid shearing surface (number 2) more extensive than in 

"Eoryctes," less extensive than in Oligoryctes or Aptemodus. 

Parapternodus ant~quus, sp nov. 

Plate 9, figures 3, 4 

Etymology -Latin antzquus. old; tlns species is the oldest described member of the Apternodontidae 

Holotype.-YPM 31169, fragment of left ramus with M2_

3 (pl. 9, 

figs. 3, 4), only known specimen. 

Localzty.-YPM locality 370a (Banjo quarry, equals UW locality 

V-73016A of Bown, 1979), lower part of Willwood Formation (Sand 

Creek facies, 70-m level), early Graybullian, sec. 33, T. 4 7 N., R. 91 

W., Washakie County, Wyo. 

Dzagnoszs.-Only known species; same as for genus. 

Dzscusswn.-Most of the significant descriptive characters appear 

in the diagnosis. The talonid of M3 1s damaged; however, the contour 

and length of the tooth suggest that the M3 talonid was relatively 

short and did not possess a prominent posterobasal cusp. The buccal 

margin of the M2 talonid is slightly more expanded posteriorly than 

m Aptemodus and Olzgoryctes; but, as in these genera, the talonid 

shelf is relatively unbasined and has no distinct cusps. 

Paraptemodus, in addition to Aptemodus and Oligoryctes, is only 

the third apternodontid to be described; all are from lower Tertiary 

rocks. Hough (1956) reviewed the then-known apternodontids and 

recommended the resurrection of Simpson's (1931) family. G. G. 

Simpson (in McGrew and others, 1959, p. 151), West (1969, p. 88), and 

West and Atkins (1970, p. 20) have recorded the presence of a fourth, 

as yet undescribed apternodontid genus from rocks of late Bridgerian 

age at Tabernacle Butte, Sublette County, Wyo. (for example, 

AMNH 55689). AMNH 55689, CM 13627 (also from Tabernacle 

Butte, McKenna and others, 1962), and several other teeth of this 

animal from the Green River Formation of Utah (Powder Wash locality, early Bridgerian) are being studied by M C. McKenna (oral commun., 1979). Romer (1966, p. 381) and Novacek (1976, p. 34) have 

published McKenna's manuscript name for this animal as a nomen 

nudum (Eoryctes). Though Paraptemodus is considerably older than 

materials of "Eoryctes," the latter animal is much more generahzed 

in the known parts of the dentition. 
ORDER INSECTIVORA(?) 69 

Paraptemodus is clearly referable to the Apternodontidae by virtue of its transverse molar trigonids and greatly reduced talonids. 

The generic ties of the new genus are less clear, but the hypertrophied 

molars link it more closely to Oligoryctes and Aptemodus than to 

"Eoryctes", a form typified by its relatively short molar tngomds. 

Although Paraptemodus is the oldest documented representative of 

its family (but see Sloan, 1969, fig. 6), the possession of a relatively 

short Ms that lacks a talonid cusp is almost certainly derived relative 

to this tooth in all other apternodontids. The hypertrophied molar 

trigonids of Aptemodus, Paraptemodus, and Oligoryctes may be 

either generalized or derived, depending on whether one favors a 

palaeoryctid or dormaaliid (or other) antecedent for this family (Van 

Valen, 1967). The narrow trigomds with small prevallid and 

postvallid surfaces, the less anteroposteriorly compressed trigonids, 

and the expanded ventrolabial margin of the M2 talonid are characters shared by Paraptemodus and "Eoryctes" that are probably 

generalized with respect to Oligoryctes and Aptemodus. 

Aside from the apparently reduced Ms talomd in Paraptemodus, 

this early Wasatchian insectivore appears to be suitably generalized 

for inclusion in the ancestry of known Oligocene apternodontids. Unfortunately, the ascending ramus of the mandible is unknown for the 

new genus, and it is uncertain whether or not this insectivore possessed a soricid-like mandible like that m "Eoryctes" (AMNH 55689; 

G. G. Simpson, m McGrew and others, 1959) and Oll,goryctes (for example, slender Jaw with shallow external temporal fossa, deep 

triangular posterointernal ramal fossa, large angular process, condyle placement and configuration, deep inferior pterygoid fossa), or a 

more robust, divergently specialized mandible as in Aptemodus 

Measurements.-(mm): M2L=1.15, M2WTri=0.90, M2WTal=0.55, 

M3L=1.20 (estimated), M3WTri=0.75, M3WTal=0.30 (estimated). 

Order INSECTIVORA(?), incertae sedis 

lnsectivora, gen et sp indeterminate 

Plate 9, figure 5 

Referred spec-,men.-YPM 30860, fragment of right ramus with 

M1(?) and trigonid of M2(?) (pl. 9, fig. 5), YPM locality 355 

D-,scussion.-This specimen may be of an unusual insectivore or a 

microchiropteran; however, these two teeth do not closely resemble 

molars of any mammal known to us. At first glance, the teeth appear 

to have been distorted by linguolabial crushing of the trigonids. The 

trigomd of M.(?) has, mdeed, been damaged on the labial side. 

However, examination of the antenor and lmgual borders of the 

tooth and comparison with M2(?) indicate that the peculiar mor-
70 PROTEUTHERIAAND INSECTIVORA, WILLWOOD FORMATION, WYO 

phology probably does not result from postmortem damage. It is also 

conceivable that the teeth represent the deciduous P 3_

4 of a 

dormaaliid-like Macrocranwn, dormaaliid sp. A, or the erinaceid 

Eolestes. There is, however, no indication of an unerupted permanent 

dentition on the excavated labial side of the Jaw, and the preserved 

parts of the two teeth are identical-a feature that 1s unusual in dP3_

4 

of most primitive mammals. 

?M1_2 are characterized by extremely narrow trigonids, and ?M1 has 

a very broad, acute talonid. The paraconid is a large shelf that proJects anterolingually from the trigonid, and the protoconid is situated 

well anterior to the metaconid, resulting in a trigonid basin that is 

oriented anterolingually-posterolabially. Judging from ?M2, the 

metaconid appears to have been considerably taller than the protoconid. The cristid obliqua joins the base of the metaconid, and the 

labial part of the postcristid is of equal length as the cristid obliqua 

and is nearly straight, imparting a symmetrical, V-shaped configuration to the talonid. The hypocomd is very low, the hypoconuhd is 

large and medial, and the entoconid is tall, trenchant, and lingually 

deflected as it is in Macrocranwn and dormaaliid sp. A. 

YPM 30860 was recovered from a locality in the lower part of the 

middle Gray Bull zone (240-m level) 

Measurements.-(mm): ?M 1L=1.75, ?M 1WTri=0.95, 

?M.WTal=1.25, ?M2WTri=l.OO. 

Creotarsus lepidus Matthew and Granger, 1918 

Type specimen.-AMNH 16169, left ramus with PrM2, and 

associated tarsal bones. 

Localzty.-"lower Gray Bull beds, Coon Creek, Garland Road, Big 

Hom Basin, Wyoming." 

Discusswn.-Originally compared with the Artiodactyla, Creodonta, Condylarthra, and Insectivora by Matthew and Granger (1918), 

Creotarsus remains an animal of enigmatic affinities. Van V alen 

(1967) placed the genus in the sensu lato Adapisoricidae, along with 

such morphologically disparate forms as Lztolestes, Amphzlemur, 

Amphidozotherium, and Ictopidzum, but Creotarsus does not closely 

resemble any of the sensu stricto dormaaliids. P 4 is similar to that in 

the didelphodontine palaeoryctid Didelphodus, but the molars are 

wholly dissimilar. P4 also resembles that in several condylarths, for 

example, Bisonalveus, but again the molars are different, and are 

closer to Palaeosinopa. It seems likely that Creotarsus is most closely 

related to the Pantolestidae, but its affinities will remain uncertain 

until better material is available. 
PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 71 

SUMMARY 

The lower Eocene Willwood Formation of the Bighorn Basin in 

northwest Wyoming has the largest and most diverse representation 

of proteutherian and insectivore mammals in the Western Hemisphere. A new sample of about 330 specimens, collected from several 

different stratigraphic levels of the Willwood Formation, clarifies 

evolutionary patterns and variation in these animals when compared 

with specimens of similar age from elsewhere. 

The Willwood fauna (including several new taxa) indicates that the 

radiation of the hpotyphian msectivores was well underway by 

Wasatchian trme and probably began much earlier. Two groups much 

better represented in younger rocks, the Apternodontidae and the 

Geolabididae, were already clearly differentiated by early Eocene 

time. They are represented by new taxa that record the earliest 

known occurrences of these families. 

The Dormaaliidae, originally described from the Sparnacian of 

Europe, are abundantly represented in the North American Wasatchian, and North American and European nyctitheriids show several similarities. These similarities indicate that the well-documented 

Clarkforkian through Wasatchian faunal interchange with Europe 

also included a variety of small lipotyphlan insectivores. Stratigraphic ranges of some of these animals in the Willwood FormatiOn 

suggest that proteutherians and insectivores have potential value as 

guide fossils when they are better known. Figure 18 on page 48 

depicts the known stratigraphic ranges of Willwood proteutherians 

and insectivores with reference to the biostratigraphic zones discussed in the text and illustrated in figure 1. The proteuthenans and 

insectivores now known from the Willwood Formation are summarized as follows: 

Order Proteuthena 

Fanuly Palaeorycbdae 

Subfanuly Palaeoryctmae 

Palaeoryctes sp 

cf Pararyctes sp 

Subfanuly D1delphodontmae 

Dulelphodus absarokae 

Fanuly Lepbcbdae 

Subfanuly Lepbctmae 

Prodzacodon tauncmerez 

Prodzacodon sp 

Palaezctops bzcuspzs 
72 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

Fa.nnly Pantolestidae 

Palaeosmopa mcerta, sp nov 

Palaeosmopa vetemma 

Palaeosmopa lutreola 

Fa.nnly Apatemytdae 

Apatemys chardm£ 

Apatemys bellulus 

Apatemys kay£ 

Apatemys sp, cf A rodens 

Order lnsectivora ( = Ltpotyphla, as used here) 

Suborder Ennaceomorpha 

Fa.nnly Dormaalndae 

Macrocranwn mtens 

Scenopagus hewettens£s, sp nov 

Scenopagus sp 

Talpavmdes dartom, gen et sp nov 

dormaalnd, sp A 

Fa.nnly Ennacetdae 

Eolestes s£mpsom, gen nov 

Le£psanolestes s£eg{nedtl.3 

cf Le£psanolestes sp 

cf "Leptacodon" ;epsem New genus of M J Novacek, T M 

Bown, and DaVId Schankler, unpub 

data, 1981) 

Suborder Soncomorpha 

Superfanuly Sonc01dea 

Fa.nnly Nyctitherudae 

Pontl.factor sp 

Plagwctenodon krausae 

Plagwctenodon savage£, sp nov 

Plagwctenowes m£crolestes 

cf Leptacodon packz, 4 

Fa.nnly Geolabtdldae 

Centetodon patratus, sp nov 

Centetodon neasham£, sp nov 

Fa.nnly Aptemodontidae 

Paraptemodus antl.quus, gen et sp nov 

Order lnsecttvora, mcertae sedls 

?lnsectivora, gen et sp mdetermmate 

Creotarsus lepwus 

'Discussed by Rose (1981) See also Bown (1979, p 60) 

•Discussed by Rose (1981) 
PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 73 

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7 4 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

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76 PROTEUTHERIA AND INSECTIVORA, WILLWOOD FORMATION, WYO 

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INDEX 

[ltahc page numbers md1cate mll.Jor references] 

A Page 

Abbrev1at10ns Cedar Pomt Quarry 

absarokae, Dulelphodus 6, 7, 71, pis 1, 2 Centetodon magnus 

Abstract 1 margznalts 

Acknowledgments 4 neashamt, sp nov 

Adaptsorex 41 patratus, sp nov 

abtmdans 41 pule her 

Adap1Sonc1dae 57, 58, 60, 70 wolffi 

Adunator lehmant 42, 43 new spec1es B 

Alhe1t pocket 64 new spec1es C 

Almagre faunal sample 7, 46 Chadroruan spec1es 

Amencan Museum collectiOn 2 chardtnt, Apatemys 

Amphechtnus 57 Clark's Fork Basm fauna 

Amphtdozothenum 58, 61, 63, 64, 70 Clarkforkmn forms 

Amphtlemur 70 Condylarthra 

Ankylodon 41, 44 Coon Creek 

anttquus, Parapternodus 67, 68, 72, pi 9 Creodonts 

ApatemyJdae so, 72 Creotarsus leptdus 

Apatemys so 

bellulus 30, 32, S8, 72, pi 4 

bell us 30, 32, 34, 39 

chardtnt 37, S8, 72, pi 4 Darton, Nelson Horat1o 

downst 40 dartont, Talpavotdes 

hurzelen 37, 38 DeUathenum absarokae 

kayt 37, S9, 72, pi 4 Desmarunae 

rodens 30, 32, 34, 40, 72, pi 2 "Dtacodon" mtnulus 

mntensts 37 D1delphodont1nae 

wht!aken 30, 37 Dtdelphodus 

Apheltscus 41 absarokae 

Apternodont1dae 67, 68, 69, 71 zone pattern 

Apternodus 67, 68 aUt dens 

Arroyo Blanco 18 dormaalud sp A 

Artiodactyla 70 Dormaah1dae 

Dormaaltus 

B Dorsey Creek 

BallJO quarry 49, 68 

Batodon 65 

Bear Creek fauna 39 

bellulus, Apatemys 30, 32, S8, 72, pi 4 early Graybulhan 

btcuspts, Palaetclops 10, 11, 16, 17, 19, 71, pi 2 Elk Creek section 

B1g Horn Basm 70 Entomolestes 

B1ghorn Basm 2, 3, 16, 19, 21, 29, 37, 38, 39, 65 grangen 

Bts01utlveus 41, 70 miens 

B1tter Creek, Wyo 16, !!1 Eolestes, gen nov 

Bown, Insectlvora 5 stmpsont 

Bndger Format1on 65 "Eoryctes" 

Bndgenan spec1es 67 Ennace1dae 

Brule Formation 67 Ennaceomorpha 

c 

D 

E 

Page 

63 

65,66 

65,66 

65, 66, 72, pis 8, 9 

59, 64, 66, 72, pi 8 

59, 65, 66 

65,66 

65,66 

65, 66 

66, 67 

37, S8, 72, pi 4 

3, 29, 37, 38, 39 

2, 71 

70 

70 

70 

70, 72 

50 

50, 60, 72, pi 6 

2 

55 

41, 42, 43 

6, 71 

2, 70 

6, 7, 71, pis 1, 2 

10 

7, 9 

5!!, 60, 70, 72, pi 6 

41, 51, 58, 71, 72 

41, 44 

16 

4, 46, 47, 49, 50, 52, 54 

4, 6, 29, 38, 39, 49, 52 

53 

54, 55, 56, 60, pi 7 

45 

5!!, 55, 70 

53, 54, 72, pis 6, 7 

67, 68 

5!!, 55, 72 

41, 51, 72 

77 
78 INDEX 

Fort Uruor Formation 

Four M1le fauna 

Garland Road 

F,G Page 

45 

2, 16, 21, 22, 30, 

37, 38, 39, 45, 46, 49, 56, 64 

70 

Geolab1d1dae 6~, 71, 72 

G1dley Quarry 63 

Graybulhan age 2, 3, 29 

"Gray Bull Member" 3 

Gray Bull zone 16 

See also lower, m1ddle, and upper Gray Bull zone 

Green R1ver Basm 20 

Green R1ver Format1on 

Heptodon 

Hewett, Donne! Foster 

hewettensts, ScenopaJJUB 

H1story 

Homogalax 

protaptnnus 

Huerfano Formation 

H 

I, J, K 

51, 68 

46 

~6. 72 

2 

3 

3 

30, 35, 51, 65 

Ictoptdtum 70 

mcerta, Palaeosmopa 20, 72, pis 3, 10 

Insect1vora 2, 5, 41, 57, 69, 70, 72 

lnsectlvora, gen et sp mdetermmate 69 

Jepsem, "Leptacodon" 

kayt, Apatemys 

krausae, Plagwctenodon 

La Barge fauna 

Lambdothenum 

Largo fauna 

late Graybul11an fauna 

Letpsanolestes 

stegfnedtt 

stmpsom 

sp 

leptdus, Creotarsus 

Leptacodon 

munusculum 

packt 

tener 

"Leptacodon" Jepsem 

ladae 

munusculum 

packt 

Lept1cttdae 

Ltpotyphla 

Lttolestes 

tgnotus 

Lost Cabm Member 

"Lost Cabm equivalent" 

L 

58, 55, 57, 60, 72, pi 7 

37, 89, 72, pi 4 

56, 59, 60, 64, 72 

16, 20, 39 

2, 3 

39 

4 

53 

54, 72 

2, 54 

55, 72 

70, 72 

58, 61 

61 

72 

56, 58, 61, 62, 68, 64 

53, 55, 57, 60, 72, pi 7 

42 

58, 68 

58, 68 

10, 71 

72 

44, 53, 55, 70 

44 

7, 19, 21, 39, 45 

3 

Lost Cabm b1ostratlgraph1c zone 

Lostcabm1an age 

4, 39 

2, 4, 18, 37 

Page 

lower Gray Bull zone 4, 7, 21, 27, 29, 37, 46, 

49, 52, 54, 55, 61, 67, 68, 70 

Lud1an age 64 

lutreola, Palaeostnopa 20, 21, 29, 30, 72, pi 3 

Lys1te Member, Wmd R1ver Format1on 7, 16, 45, 46 

Lys1te biOstratigraphic zone 4, 7, 11, 16, 19, 27, 39, 46 

"Lys1te eqmvalent" 3 

Lys1ttan age 2 

Macrocranwn 

mtens 

tenerum 

Mammalia 

Mckennathenum 

ladae 

ltbttum 

Messelma 

Mlcroch~ropteran 

m1ddle Gray Bull zone 

Neasham, J W 

neashamt, Centetodon 

mtens, Macrocramon 

No Water Creek area 

No Water fauna 

Nyct1therudae 

Nycttthenum 

celatum 

serotmum 

velox 

Oltgoryctes 

cameronensts 

Palaetctops 

btcuspts 

bndgen 

matthewt 

multtcuspts 

pmeyensts 

"ptneyensts" 

sp , charactensttcs 

Palaeoryctes sp 

Palaeorycttdae 

Palaeoryctlnae 

Palaeostnopa 

dtdelphmdes 

mcerta, sp nov 

lutreola 

veternma 

sp 

sp E 

Pantolesttdae 

Papto anubts 

Parapternodus, gen nov 

anttquus, sp nov 

Pararyctes sp 

M 

44, 51, 52, 53, 58, 70 

41, 44, ~5, 72, pis 5, 6 

45 

6 

41, 43, 57, 58 

41, 43 

42 

45 

69 

4, 7, 16, 19, 21, 27, 

29, 38, 39, 46, 49, 52, 66, 70 

N 

O,P 

66 

65, 66, 72, pis 8, 9 

41, 44, ~5, 72, pis 5, 6 

46 

2, 29, 37, 38, 39, 60 

57, 60, 71, 72 

58, 61 

59 

58 

58, 68, pi 8 

68 

67 

10 

10, 11, 16, 17, 19, 71, pi 2 

20 

11 

10 

16 

20 

10 

6, 71 

6, 71 

6, 71 

70 

20, 21, 25, 28 

20, 72, pis 3, 10 

20, 21, 29, 30, 72, pi 3 

21, 26, 72, pis 3, 4 

20 

21, 22 

20, 70, 72 

35 

67 

67, 68, 72, pi 9 

6, 71 
INDEX 79 

patratus, Centetodon 

Pelycodus Jarrovn 

tngonodus 

Phenacodaptes 

pweyensts, Patamctops 

Plagwctenodo11 

krausae 

savagm, Rp nov 

Plagwctenotdes 

mtcrolestes 

Plagtomene multtcuspts 

Polecat Bench Fonnat10n 

Pongo pygmaeus 

Pontifactor 

besttola 

sp 

Powder R1ver Basm 

Powder R1ver fauna 

Powder Wash locahty 

Prmceton Umvers1ty collectiOn 

Prodtacodon 

tauncweret 

sp 

Proteuthena 

Red Butte 

References C1ted 

roden.s, Apatemys 

R,S 

Page 

59, 6~, 66, 72, pi 8 

3 

52 

41 

16 

2, 50, 60 

56, 59, 60, 64, 72 

56, 61' 64, 72, pi 7 

2, 58, 64 

61, 64 

19 

45 

35 

58 

59 

59, 60, 63, 72 

21, 29 

16, 21, 28, 37, 38, 56 

68 

10 

10, 11, 13, 71 

18, 71, pi 2 

2, 5, 6, 71 

40 

73 

30, 32, 34, ~o. 72, pi 2 

San Jose Fonnat10n, N Mex 7, 18, 21, 22, 45, 46 

Sand Creek fac1es 2, 6, 47, 49, 50, 52, 55, 60, 61, 68 

Sand Wash Ba~m. Colo 21, 64 

Saturmma beata 58, 61, 63 

gractlts 58, 61, 63 

Savage, 0 E 61 

savaget, Plagwctenodon 56, 61, 64, 72, pi 7 

Scenopagus 41, 44, 52, 53, 62 

curttdens 47 

edenensts 

hewettensts, sp nov 

pnscu.s 

sp 

Schankler, Proteuthena 

47, 49 

~6. 72 

47, 49 

1,9, 51, 60 72 

Sheep Mountam 

shrews 

stmpsont, Eolestes 

Shck Creek quarry 

Soncmdea 

Soncomorpha 

Sparnacum 

Tabernacle Butte 

Talpavotdes, gen nov 

dartont, gen et sp nov 

Talpavus 

ntttdu.s 

tauncmeret, Prodtacodon 

Tetlhardella whttaken 

Telpavotdes dartont 

T 

TorreJoman Rock Bench quarry 

UW locahty V-73037 

UW locabty V-73055 

Umtan age 

upper Gray Bull zone 

velox, Nycttthenum 

veternma, Palaeosnwpa 

u,v 

W,Y 

Wasatch1an faunal mterchange 

Washak1e basm 

West, R M , study 

W1Uwood Fonnat10n 

faunal zonat10n 

Wmd R1ver Basm 

Wmd R1ver Fonnat10n 

Lost Cabm Member 

Lys1te Member 

Yale Peabody Museum collectwn 

Yale locahty 363 

Page 

40 

58 

5~ 

50 

72 

57, 72 

71 

57, 68 

41, 44, 50, 59, 61 

50, 60, 72, pi 6 

41, 44, 51, 52, 53, 58 

51 

10, 11' 13, 71 

38 

47 

45 

35, 67 

4 7 9, 21, 27, 

29, 37, 40, 46, 66, 67 

58, 63, pi 8 

21, 26, 72, pis 3, 4 

71 

21 

30 

2, 19, 51, 71 

3 

7, 21, 39 

3, 7, 39, 45 

7, 19, 21, 39, 45 

7, 16, 45, 46 

2 

6 

ttU 5 GOVERNMENT PRINTING OFFICE 1982-576 034/130 

PLATES 1-10 

Contact photographs of the plates m tlus report are available at cost, from the U S 

Geological Survey Photographic Library, Federal Center, Denver, Colorado 80225 
PLATE 1 

FIGURES 1, 2. Didelphodus absarokae (Cope, 1881) (p. 6.) 

Right P r M3, USGS 303, X 4.2. Both views are 

stereophotographs 

1 Occlusal view. 

2. Labial view. 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 1 

2 

DIDELPHODUS 
PLATE 2 

FIGURES 1-7. Proteutherians from the Willwood Formation. 

1, 2, 4. Didelphodus absarokae. (Cope, 1881) (p. 6.) 

1. Labial aspect of YPM 18971, right M1_

2, 

X 2.2. 

2. Occlusal view of YPM 25361, left P4-M1

, 

X 3 1. Stereophotograph. 

4. Occlusal view of YPM 18971, right M1_2, 

X3.6. 

3, 5. Palaezctops bzcuspis (Cope, 1880) (p. 19.) 

3. Occlusal view of YPM 23723, left P4- 5, 

M1- 3, X 3.0. Stereophotograph. 

5. Labial view of YPM 23723, left P 4_

5, 

M1_

3, X 3.5. 

6. Prodzacodon sp. (p. 18.) 

Labial aspect of YPM 26040, right P 4_

5, 

M1

_

2, X 3.4. 

7. Apatemys sp, cf A rodens Troxell, 1923 

(p 40) 

Labial view of YPM 30582, right ramus 

with /C and M3, X 3.6. 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 2 

4 

6 

DIDELPHODUS, PALAEICTOPS, PRODIACODON, AND APATEMYS 
PLATE 3 

FIGURES 1-4. Palaeosinopa 

Early Eocene 

1. P vetemma Matthew, 1901 (p. 26.) 

Occlusal aspect of YPM 27168, right 

P3-M2 and left P3-M3

, X 1.6, lower 

jaws unfigured. Stereophotograph 

2. P lutreola Matthew, 1918 (p. 29.) 

Occlusal view of YPM 26175, nght M1 

(damaged), M2_

3, X 4.8. Stereophotograph 

3, 4. P zncerta, sp. nov. (p. 20.) 

3. Occlusal aspect of YPM 30613, right 

M2- 3, X 3.2. Stereophotograph 

4. Labial aspect of AMNH 39565, left 

M1_

3, X 2. 7. Other broken teeth are 

unfigured. 
GEOLOGICAL SURVEY BULLETIN 152::3 PLATE 3 

2 

3 

PALAEOSINOPA 
PLATE 4 

FIGURES 1, 2. Palaeosinopa ueternma Matthew, 1901 (p 26.) 

From the Willwood FormatiOn Stereophotographs. 

1 Occlusal aspect of YPM 2667 4, right M1_

3, 

X 19. 

2. Occlusal view of YPM 34255, right M1_3, 

X 16 

3-6. Apatemys 

From the Willwood Formation. Stereophotographs. 

3, 6. A chardznz (Jepsen, 1930a) (p 38 ) 

3. Occlusal aspect of UMMP 66686, 

right M2- 3, X 6.4. 

6. Occlusal aspect of UMMP 67380, 

nght M1_2, X 6.3. 

4. A kayz (Simpson, 1929) (p. 38.) 

Occlusal aspect of UMMP 68591, right 

M1- 3, X 6.4. 

5. A bellulus Marsh, 1872 (p. 38.) 

Occlusal aspect of UMMP 66092, left 

M1_

3, X 6.3. 
GEOLOGICAL SURVEY 

5 

2 

r 

( 

BULLETIN 1523 PLATE 4 

PALAEOSINOPA AND APATEMYS 
PLATE 5 

FIGURES 1-5. Macrocranwn nitens (Matthew, 1918) (p. 45) 

From the Willwood Formation 

1. Occlusal aspect of YPM 23077, nght P4-M2

, 

X 10.0 Stereophotograph. 

2. Occlusal aspect of YPM 24380, nght P 3-M2, 

X 10 0. Stereophotograph 

3. Occlusal view of YPM 30655, left PrM3, 

X 6.8 Stereophotograph 

4. Occlusal view of YPM 30655, left P4-M2

, 

X 6 3. Stereophotograph 

5. Lab1al view of YPM 24380, nght P3-M2, 

X 100 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 5 

MACROCRANION 
PLATE 6 

FIGURES 1, 2 Macrocranwn nztens (p. 45.) 

1. Labial aspect of YPM 30655, left PrM3, X 7 7 

2. Occlusal view of YPM 30597, nght P4-M1

, X 12.3. 

Stereophotograph. 

3,4 Talpavozdes dartom, gen et sp nov. (p. 50) 

Stereophotographs 

3. Occlusal aspect of UW 9597, nght M2_

3, 

X 130. 

4. Occlusal aspect of UW 9624 (type specimen), 

nght PrM2, X 14.5. 

5. Dormaahid, sp. A (p 52.) 

Occlusal aspect of UW 9627, left M2 (damaged), 

M3, X 14.3 

6 Eolestes szmpsonz, gen. nov. (Bown, 1979) (p. 54) 

Labial viewofYPM 35156,leftPrM2, X 13 5 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 6 

3 

5 

MACROCRANION, TALPAVOIDES, DORMAALIID, AND EOLESTES 
PLATE 7 

[All from the Eocene of Wyommg] 

FIGURE 1. Eolestes simpson~ gen. nov (Bown, 1979) (p. 54.) 

OcclusalaspectofYPM 35156,leftPrM2, X 12.5. 

Stereophotograph. 

2, 4. Entomolestes grangen (p. 56.) 

2. Occlusal aspect of AMNH 98742, PrM3, X 9.6. 

Stereophotograph. 

4. Labial view of AMNH 98742, right PrM3, X 10.0. 

3, 6. Plagioctenodon savagez, sp. nov. (p. 61.) 

3 Labial aspect of YPM 34257 (type), right P3-M2, 

X 10.4. M1 damaged. 

6. Occlusal aspect of YPM 34257 (type), 

rightP3-M2, X 9.9 

M1 damaged Stereophotograph. 

5. "Leptacodon" jepseni (p. 55.) 

Labial view ofYPM 30559, right PrM2, X 11.5 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 7 

2 

4 

6 

EOLESTES, ENTOMOLESTES, PLAGIOCTENODON, AND "LEPTACODON" 
PLATE 8 

FIGURES 1,2. Nyctzthenum velox Marsh, 1872 (p. 63) 

From the middle Eocene of Wyoming. 

1. Labial aspect of UW 11386, left PrM3, 

X9.2. 

2. Occlusal view of UW 11386, left P r M3, 

X 9 2 Stereophotograph. 

3-5. Centetodon 

From the early Eocene of Wyoming. 

3. C patratus, sp. nov. (p. 64.) 

Occlusal aspect of YPM 23088, left P 4 

(damaged), M1_

2, X 8 9. Stereophotograph 

4, 5. C neashami, sp. nov (p 66.) 

4. Labial view of YPM 26626 (type), left 

PrM1, X 6.4. 

5. Labial view of YPM 27011, left P4, 

X6.8. 
GEOLOGICAL SURVEY BULLETIN 15~ PLATE 8 

3 

5 

4 

NYCTITHERIUM AND CENTETODON 
PLATE 9 

FIGURES 1, 2 Centetodon neashamz, sp. nov. (p 66) 

From the Willwood Formation 

Labial view of YPM 25700, right PrM1, 

X 7.7 

2. Occlusal aspect of YPM 26626 (type), left 

PrMh X 6.4 

3, 4. Paraptemodus antzquus, gen et. sp. nov. (p. 68.) 

From the Willwood Formation. 

3. Occlusal aspect of YPM 31169 (type), left 

M2_

3, X 10.7. Stereophotograph 

4. Labial view of YPM 31169 (type), left M2_

3, 

X 10.7 

5. ?lnsectivora, gen. et sp. indetermmate (p. 69 ) 

Occlusal view of YPM 30860, nght ?M1_2, X 11.6. 

From the Willwood Formation 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 9 

2 

3 

CENTETODON, PARAPTERNODUS, AND ?INSECTIVORE 
PLATE 10 

[Bar IS 10 0 mm long] 

FIGURES 1, 2. Palaeostnopa tncerta, sp. nov. (p. 20.) 

From the Willwood FormatiOn UMMP 69722, type 

specimen preserving upper and lower cheek teeth 

and fragments of the cranium and rostrum. Courtesy of P D. Gingerich; photograph by K Steelquist 

1. Left aspect. 

2. Right aspect. 
GEOLOGICAL SURVEY BULLETIN 1523 PLATE 10 

PALAEOSINOPA