New and Little,-Known 

I I )~e~ Ammonites from thetfl u 

Upper Cretaceous 

(Cenomanian and Turonian) 

· of the Western Interior . 

of the United States 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 

New and Little-Known 

Ammonites from the 

Upper Cretaceous 

(Cenomanian and Turonian) 

of the Western Interior 

of the United States 

By WILLIAM A. COBBAN 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 

A species each of Anisoceras, Desmoceras, 

Tragodesmoceras, Cal ycoceras, N igericeras, 

and Paracompsoceras (new genus) is 

described and illustrated 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director 

Library of Congress catalog-card No. 71-612128 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402- Price $1.25 (paper cover) 
CONTENTS 

Page 

Abstract __________________________________________ _ 1 

1 

1 

4 

4 

4 

4 

5 

5 

5 

Systematic descriptions-Continued 

Family M uniericeratidae-Continued Introduction ______________________________________ _ 

Geographic distribution ____________________________ _ Genus Tragodesmoceras Spath _______________ _ 

Systematic descriptions _____________________________ _ Tragodesmoceras carlilense, n. sp _________ _ 

Family Anisocera tidae __________________________ _ Family Acanthoceratidae _______________________ _ 

Genus Anisoceras Pictet ____________________ _ Genus Paracompsoceras, n. gen ______________ _ 

A m·soceras plicaWe (J. Sower by) _________ _ Paracompsoceras landisi, n. sp ___________ _ 

Family Desmoceratidae ________________________ _ Genus Calycoceras Hyatt ___________________ _ 

Calycoceras naviculare (~antell) _________ _ Genus Desmoceras ZitteL ___________________ _ 

Subgenus Moremanoceras, n. subgen ______ _ 

Desmoceras (Moremanoceras) scotti 

Family V ascocera tidae _________________________ _ 

Genus Nigert"ceras Schneegans _______________ _ 

Nigericeras bCotti, n. sp _________________ _ ~oreman _______________________ _ References cited ___________________________________ -

Family. ~uniericeratidae ________________________ _ 

6 

8 Index ____________________________________________ _ 

ILLUSTRATIONS 

[Plates follow index] 

PLATE I. Calycoceras naviculare and Anisoceras plicatile. 

2. Desmoceras (Moremanoceras) scotti and Paracompsoceras landisi. 

3-5. Tragodesmoceras carWense. 

6-8. Paracompsoceras landisi. 

9. Nigericeras scotti and Paracompsoceras landisi. 

10-17. Calycoceras naviculare. 

18. Nigericeras scotti. 

FIGURE I. Index map of part of the western interior region of the United States ______________________________________ _ 

2. Cross sections of A,nisoceras plicatile _______________________________________________________ -------------

3. External suture of Desmoceras (M oremanoceras) scotti ________________________________________ -------------

4. Diagrammatic outlines of Desmoceras (Moremanoceras) scotti ______________________________________________ _ 

5. Whorl sections of Desmoceras (M oremanoceras ) scotti ____________________________________ -- _---------------

6. Scatter diagrams showing umbilical ratios and number of ventral ribs of Tragodesmoceras carlilense, n. sp __ - __ --

7. Section through holotype of Tragodesmoceras carlilense, n. sp _______________________ -----------------------

8. External suture of Tragodesmoceras carWense, n. sp _________________________________ -- ____ -- _-------------

9. Cross sections of holotype of Paracompsoceraslandisi, n. sp ______________________________________________ _ 

10. External suture of holotype of Paracompsoceraslandisi, n. sp _____________________________________________ _ 

11. Whorl sections of Paracompsoceras landisi, n. sp ________________________________________ - __ --------------

12. Scatter diagrams showing umbilical ratios and number of ribs of Calycoceras naviculare _____________________ --

13. Cross sections of Calycoceras naviculare __________________________________________ -----------------------

14. Lateral 1 abe of Calycoceras naviculare ____________________________________________ ---_---_-_-------------

15. Scatter diagram showing umbilical ratios of Nigericeras scotti, n. sp _________________ -----------------------

16. Whorl sections of holotype of Nigericeras scotti, n. SP-----------------------------------------------------

17. External sutures of Nigen·ceras scotti, n. sp ____________________________________ - __ -----------------------

TABLES 

Page 

8 

8 

10 

10 

10 

13 

13 

18 

18 

18 

20 

23 

Page 

2 

5 

6 

7 

7 

8 

9 

10 

11 

11 

12 

16 

17 

18 

19 

19 

20 

Page 

TABLE I. Localities at which fossils were collected _____________________________________________________ ----------- 3 

2. Dimensions, and rib counts of Calycoceras naviculare_____________________________________________________ 15 

3. Dimensions and tubercle counts of N1:gericeras scotti______________________________________________________ 17 

III 

421-990 0- 71 - 2 

NEW AND LITTLE-KNOWN AMMONITES FROM THE UPPER 

CRETACEOUS (CENOMANIAN AND TURONIAN) OF THE 

WESTERN INTERIOR OF THE UNITED STATES 

BY WILLIAM A. CoBBAN 

ABSTRACT 

An example of each of the genera Anisoceras, Desmoceras, 

Tragodesmoceras, Oalycoceras, Nigericeras, and the new genus 

Para.compsoceras is described from the western interior region. 

Anisoceras plicatile (.J. Sowerby) and Oalycoceras naviculare 

(Mantell), species described originally from England, are recorded from the Greenhorn Limestone of southeastern GoloTado. 

Desmoceras scotti (Moreman), known previously only from the 

Eagle Ford Formation of Texas, was discovered recently in the 

Greenhorn Limestone of southeastern Colorado and in the 

Mancos Shale of northeastern Arizona. JJloremanoceras, a new 

subgenus, is proposed for this species. The West African lower 

Turonian genus Nigericera8 is recorded for the first time in the 

western interior; it is represented by N. scotti, n. sp. The ne·w 

genus Paracompsoceras (type species, P. landisi, n. sp.) is proposed for a late Cenomanian ammonite from New Mexico that 

has juvenile whorls resembling those of Acanthoceras and adult 

whorls resembling those of Acompsoceras. Tragodesrnocera8 

ca1"lilense, n. sp., is described from the lower part of the Carlile 

Shale of the Black Hills area. 

INTRODUCTION 

Collections of fossil mollusks 1nade by members of the 

U.S. Geological Survey include many interesting ammonites that have potential value for the correlation of 

rocks in the "·estern interior region with those of the 

Gulf Coastal Plain and even with those of are1as as far 

away as Europe and Afriea. Among these ammonites 

are representatives of the genera Anisocera8·~ Desmoceras, Tragodestnocera8, Oalycocera8, 'and Nigericera8, 

as \Yell as a new genus, Paraconvpsocera8. Nigericera8 

and Parrzcmn:jJ80CeJ'a8 are new discoveries for the western 

interior. The presence of the other genera in the U.S. 

Geological Survey's collection has been known for m1any 

years although only one species ( Tra.gode8mocer~ ba8si 

Morrow) h1as been described. 

All fossils described in this report are stored in the 

U.S. National Muserun in Was:rrington, D.C. Plast.e.r 

casts of many of the specimens are kept in the, U.S. Geological Survey's Mesozoic invertebrate fossil collections 

at the Federal Center at Denver, Colo. All photogra,phs 

\Yere made by Robert E. Burkholder, of the U.S. Geological Survey, and some of the whorl sections were 

drawn by Charles C. Oapra,ro, also of the Geological 

Survey. Mr. C. "\¥. Wright, London, kindly loaned me 

English examples of Anisoceras plicatile for comparison with specimens from Colorado. 

GEOGRAPHIC DISTRIBUTION 

The ammonites described or recorded in this report 

were collecte.d at 35 localities in Wyoming, South 

Dakota, Colorado, I\:ansas, Arizona, and New Mexico. 

The general localities are sho,yn in figure 1, and data 

concerning the localities, stratigraphic position, and collectors are given in table 1. 

1 
2 

40° 

35° 

AMMONITE·S, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

YELLOWSTONE 

I I 

' I NATIONAL. 

LP.A~I 

w 

L ___ _ 

o Kayenta 

X31 

ARIZONA 

110° 

y 0 

X 32,33 

0 

M I 

c 0 L 

N E w 

Grants 

o x35 

x34 

Rapid City 0 

SOUTH DAKOTA 

14,15 X 

x12,13 

N G Xg x10,11 

I r-----------

' NEBRASKA 

I Pt"'tte 

I 

I ~heyenne1 

- - -- -- ---- ~ - - --E_:'Dil";( 

0 R 

M E X 

o Santa Fe 

106° 100 

..,>JO 

Solt'th 

~\,fj; 

1--

\ 

A D 0 

w 

< w 

z 

< 

Pueblo ~ 

x 17,18 x29 

X19-27 

Tri~flad l ---- ---T--- o Raton 

I c 0 TEXAS 

200 MILES 

40° 

}"'IGuRE 1.-Part of the western interior region of the United States showing localities of ammonite collections 

referred to in the text and in table 1. 
GEOGRAPHIC DISTRIBUTION 3 

TABLE !.-Localities at which fossils were collected 

U.S. Geol. 

Locality Survey Collector, year of collection, description of locality, and 

(fig. 1) Mesozoic stratigraphic assignment locality 

l_____ 21793 

2_____ D411 

3- - - -- 11199 

4_____ 21792 

5- - - - - 11190 

6_____ 12665 

7- - - - - 11192 

8_---- 26372 

9_ _ _ __ D3754 

10_ _ _ _ D3743 

1L _____ D1417 

12 ____ D1450 

13_ _ _ _ D1525 

14____ 12642 

15____ 18872 

16____ 15395 

17____ 1394 

18_ _ _ _ D6522 

J. B. Reeside, Jr., and W. A. Cobban, 1949. 

Eight miles southeast of Alzada, in the 

SW%SW% sec. 11, T. 57 N., R. 62 W., 

Crook County, Wyo. Carlile Shale, from 

limestone concretions near base of Pool 

Creek Shale Member. 

C. MacClintock, 1955. Sec. 19, T. 46 N., R. 

63 W., Weston County, Wyo. Carlile Shale, 

lower part. 

W. W. Rubey, 1922. About 17~ miles east of 

Pedro Siding, Weston County, Wyo. [Near common corner of sees. 4, 5, 8, and 9, T. 

45 N., R. 62 W.] Carlile Shale, near base. 

W. A. Cobban, 1948. One mile southwest of 

Newcastle in the NW~~ sec. 31, T. 45 N., 

R. 61 W., Weston County, Wyo. Carlile 

Shale, from light-gray-weathering limestone 

concretions 62 ft. above base. 

C. R. Longwell and W. W. Rubey, 1922. 

About 2% miles south of Newcastle, Wyo. 

Carlile Shale, near base. 

W. W. Rubey, 1924. One mile south of Newcastle, Wyo. Carlile Shale, lower part. 

C. R. Longwell and W. W. Rubey, 1922. Two 

miles northwest of LAK Ranch near Newcastle, Wyo. [sec. 2, T. 44 N., R. 61 W.]. 

Carlile Shale, lower part. 

D. A. Brobst, 1957. NW7~NW% sec. 18, T. 42 

N., R. 60 W., Weston County, Wyo. 

Carlile Shale, lower part. 

W. A. Cobban, 1961. SW7~SW7~SE7~ sec. 6 

T. 9 S., R. 2 E., Fall River County, S. Dak. 

Carlile Shale, from gray limestone concre- tions about 20 ft below base of Turner 

Sandy Member. 

W. A. Cobban, 1961. W%NW7~ sec. 34, 

T. 8 S., R. 6 E., Fall River County, S. Dak. 

Carlile Shale, from light-gray limestone con- cretions about 90 ft above base. 

G. R. Scott and W. A. Cobban, 1957. About 

5% miles southeast of Hot Springs, in the NW%SE~~NE~~ sec. 3, T. 8 S., R. 6 E., 

Fall River County, S. Dak. Carlile Shale, 

from the lower shale member. 

J. R. Gill, 1957. NW7~NE7~ sec. 26, T. 7 S., 

R. 6 E., Fall River County, S. Dak. Carlile 

Shale, lower part. 

D. E. Wolcott and C. E. Price, 1957. North 

of the center of the SW 7~ sec. 35, T. 7 S., 

R. b E., Fall River County, S. Dak. Carlile 

Shale, lower part. 

W. W. Rubey, 1924. Sec. 31, T. 4 S., R. 8 E., 

Custer County, S. Dak. Carlile Shale, lower 

part. 

N. H. Darton, 1898. Two miles southeast of 

Fairburn, Custer County, S. Dak. Carlile 

Shale, lower part. 

J. H. Johnson, 1930. Rock Canyon anticline 

just west of Pueblo, Colo. Greenhorn 

Limestone. 

G. K. Gilbert, 1894. About 7 miles east of 

Drip Springs, lat 37°33' N., long 104°4' W., 

Colo. [about 4% miles east of Thatcher, Las 

Animas County]. Greenhorn Limestone. 

G. R. Scott and W. A. Cobban, 1966. Three 

miles east of Thatcher, in the NW% sec. 6, 

T. 29 S., R. 59 W., Las Animas County, 

Colo. Greenhorn Limestone, near base of 

Bridge Creek Limestone Member. 

TABLE !.-Localities at which fossils were collected-Continued 

U.S. Geol. 

Locality Survey Collector, year of collection, description of locality, and 

(fig. 1) Mesozoic stratigraphic assignment locality 

19____ 18676 

20_--- 18678 

21____ 18683 

22____ 18684 

23_--- 18685 

24_--- 18686 

25_--- 18687 

26_--- 22899 

27 _ _ _ _ D6530 

28_ _ _ _ D7030 

29_ _ _ _ D6756 

30_ _ _ _ D4870 

3L ___ D7092 

32_ _ _ _ D6159 

33_ _ _ _ D6160 

N. W. Bass, 1941; G. R. Scott and W. A. 

Cobban, 1966. W% sec. 15, T. 30, S., R. 60 

W., Las Animas County, Colo. Greenhorn 

Limestone, basal bed of Bridge Creek 

Limestone Member. 

N. W. Bass, 1941; G. R. Scott and W. A. 

Cobban, 1966. SE% sec. 12 and NE7~ sec. 13, 

T. 30 S., R. 60 W., Las Animas County, 

Colo. Greenhorn Limestone, basal bed of 

Bridge Creek Limestone Member. 

N. W. Bass, 1941; G. R. Scott and W. A. 

Cobban, 1966. N7~ sec. 12, T. 30 S., R. 60 W., 

Las Animas County, Colo. Greenhorn 

Limestone, basal bed of Bridge Creek 

Limestone Member. 

N. W. Bass, 1941. NE~~ sec. 35, T. 29 S., R. 60 

W., Las Animas County, Colo. Greenhorn 

Limestone, basal bed of Bridge Creek Limestone Member. 

N. W. Bass, 1941. NE% sec. 35, T. 29 S., R. 60 

W., Las Animas County, Colo. Greenhorn 

Limestone, basal bed of Bridge Creek 

Limestone Member. 

N. W. Bass, 1941; G. R. Scott and W. A. 

Cobban, 1966. E7~ sec. 15, T. 30 S., R. 60 W., 

Las Animas County, Colo. Greenhorn 

Limestone, basal bed of Bridge Creek 

Limestone Member. 

N. W. Bass, 1941. Sec. 12, T. 30 S., R. 60 W., 

Las Animas County, Colo. Greenhorn Limestone, basal bed of Bridge Creek Limestone 

Member. 

J. B. Reeside, Jr., H. R. Christner, and W. A. 

Cobban, 1950; G. R. Scott and W. A. 

Cobban, 1966. SW% sec. 12, and NE~~NW7~ 

sec. 13, T. 30 S., R. 60 W., Las Animas 

County, Colo. Greenhorn Limestone, basal 

bed of Bridge Creek Limestone Member. 

W. A. Cobban, 1968. SE~~SE7~ sec. 3, T. 30 S., 

R. 60 W., Las Animas County, Colo. Greenhorn Limestone, basal bed of Bridge Creek 

Limestone Member. 

J. F. Clement, 195U. Sec. 23, T. 31 S., R. 60 W., 

Las Animas County, Colo. Greenhorn Limestone, basal bed of Bridge Creek Limestone 

Member. 

G. R. Scott, 1964; E. R. Landis and W. A 

Cobban, 1969. Spillway of check dam in the SE~~ sec. 14, T. 29 S., R. 49 W., Baca County, 

Colo. Greenhorn Limestone, from a 3-in. 

limestone bed in the lower part. 

G. R. Scott and W. A. Cobban, 1964. West 

bank of Bridge Creek in the E%NE7~ sec. 22, 

T. 23 S., R.. 42 W., Hamilton County, Kans. 

Greenhorn Limestone, 4 ft above base of 

Bridge Creek Limestone Member. 

W. A. Cobban, 1969. East side of Longhouse 

Valley, 13 2/ 10 miles south and 13 miles west of 

the northeast corner of the Kayenta 15-

minute quadrangle (Navajo planimetric 

No. 39), Navajo County, Ariz. Mancos 

Shale, from a limestone concretion at base. 

E. R.. Landis, 1967. East of State highway 32, 

in the southwest part ofT. 9 N., R.. 17 W., 

McKinley County, N. Mex. From a brownweathering sandstone concretion 12 ft above 

the top of the Dakota Sandstone. 

E. R.. Landis, 1967. Same locality as D6159. 

From sandstone 46 ft above top of Dakota 

Sandstone. 
4 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

TABLE 1.-Localities at which fossils were collected-Continued 

U.S. Geol. 

Locality Survey Collector, year of collection, description of locality, and 

(fig. 1) Mesozoic stratigraphic assignment 

locality 

34_ _ _ _ D6130 E. R. Landis, C. H. Dane, and W. A. Cobban, 

1967-69. North of Little Narrows, about 15 

miles south of Grants, in the S W)>~ sec. 6 

and NW% sec. 7, T. 8 N., R. 9 W., Valencia 

County, N. Mex. From brown-weathering 

sandstone concretions in basal part of 55-ft 

unnamed sandstone and 187ft above base of 

Dakota Sandstone. 

35_ _ _ _ D7084 E. R. Landis, C. H. Maxwell, and W. A. 

Cobban, 1969. Three miles north of Laguna, 

in the SE)>~SE)>~NE% sec. 20, T. 10 N., R. 5 

W., Valencia County, N. Mex. From brownweathering sandstone concretions just below 

the second sandstone member of the Mancos 

Shale (Moench, 1963). 

SYSTEMATIC DESCRIPTIONS 

Phylum :MOLLUSCA 

Class CEPHALOPODA 

Order AMMONOIDEA 

Family ANISOCERATIDAE 

Genus ANISOCERAS Pictet, 1854 

Type species.-Hamuites 8aussurr,eanus Pictet, lr847. 

Anisocera:s includes heteromorphic ammonites that 

have an open helicoid spire in the juvenile stage and a 

spire that is hooklike in the mature stage. Numerous 

transverse ribs encircle the limbs; these ribs are weakest 

on the dorsum. Most of the shells have a row of lateral 

tubercles and a row of ventral tubercles on each side. 

The genus is Inost common in rocks of late Albian and 

Cenomanian Age. 

Anisoceras plicatile (J. Sowerby) 

Pia te 1, figures 4-7, text figure 2 

1819. Hanlites plicatilis J. ISowerby, The 'Mineral Conchology 

of Great Britain, v. 3, p. 59, pl. 23'4, fig. 1. 

1822. Hanzites pUcatilis J. Sowerby. Mantell, The fossils of 

the South Downs or illustrations of the geology olf 

Sussex, p. 12'1, pl. 23, figs. 1, '2. 

1872. ?Anis·oceras plicaUle (J. Sowevby). SchlUter, Palaeontogra,phiea, v. 21, p. 114, pl. 34, fig,g, 6--8. 

1939. ~-inisocera:s plicatile ( J. Sowerlby). S.pa'th, A monograph 

of the Ammonoidea of the Gault, Palaeontograph. 1Soc., 

v. 92, p. 557, text figs. 196e-'h. 

1959. Anisoceras plicaUle ( J. Sower by). Cieslii1ski, In st. Geol. 

['Warsa'W] Prace, v. ·28, p. 3;6, pl. 4, fig. 2. 

1964. ?Anisoceras plicatile ( J. Sower:by). 'Collignon, Atlas des 

fossiles caracteristiques de Madaga,sca·r (Ammonites) : 

Republique Malgaehe, Service Geol., Part l'I (Oenomanien) , p. 8, 35, pl. 319, figs. 1363-1364 ; pl. 325, fig. 

1453'. 

Sowerby's original specimen, which apparently has 

been lost according to Spath (1939, p. 557), consisted 

of a uniformly curved limb with end diameters of about 

14 and 25 mm. Sowerby's illustration shows a moderately fine rihbed limb that has 11-13 rectiradiate ribs 

crossing the venter in a distance equal to the diameter. 

Two rows of flat-topped tubercles-a ventrolateral row 

and a midflank row-are present on each side. Sowerby 

observed that each tubercle extended over three ribs and 

that the space separating adjacent tubercles of a row 

was occupied by two ribs. 

Mantell (1822, p. 121, pl. 23, figs. 1, 2) presented 

drawings of two curved limbs of A. plicatile of which 

the smaller had preserved ventrolateral spines. The 

other specimen, about 58 mm long with a maximum 

whorl height of 18 mm, was later refigured by Spath 

( 1939, text fig. 196f). It has 10 ribs for the diameter 

and as many as three ribs between adjacent tubercles 

of a row. 

Schluter (1S7'2, p. 114, pl. 34, figs. 6-8) assigned 

Sowerby's Hamites plicatilis to Anisocera8 and figured 

a small fragment from the upper Cenomanian of northwestern Germany. His drawings show the tubercles on 

single ribs that are stronger than the untuberculated 

ones-a condition possibly exaggerated in the drawings. 

Spath (1939, text figs. l96g, h) illustrated an uncrushed specimen of A. plicatile from the Cenomanian 

of Dorset, England. It is about 46 mm long and has a 

"Thorl height of at least 15 mm. Spath presented a. perfectly circular eross-sectional drawing which showed 

rows of equally spaced tubercles. Rib density seems to be 

about 10 or 11 for the diameter. 

Ciesli{lski ( 1959, p. 36, pl. 4, fig. 2) described a small 

fragment of a curved limb from the lower Cenomanian 

of Poland. The specimen seems to be typical of A. 

plicatile. It has a nearly circular section, ribs number 

9 or 10 for the diameter, and tubercles cover two or 

three ribs. 

Collignon ( 1964, p. 8, 35, pl. 319, figs. 1363-1364; 

pl. 325, fig. 1453) illustrated three fragments of curved 

limbs that he assigned to A. plic:atile. They are from 

the lower Cenomanian of Madagascar. They have whorl 

heights from 12 to 19 mm and circular to stoutly elliptical sections. None closely resembles the specimens of 

Sowerby, Mantell, or Spath. Two have fewer ribs, and 

one has more ribs. One specimen that has a rather simple suture has the lateral tubercles nearer the dorsum 

than does typical A. plicatile. 

Two specimens that seem assignable to A. plicatile 

came from the basal bed of the Bridge Creek Limestone 

Member on the 1

Model anticline in southeastern Colorado 

(fig. 1, loc. 26). Each is a septate internal mold that 

consists of part of a straight limb and part of an 

elbow. 
SYSTEMATIC DESCRIPTIONS 5 

The smaller specimen, 97 mm long, is crushed laterally. It tapers rapidly from a whorl height of 22.5 mm to 

37 mm, both figures are about equally exaggerated owing to crushing. Ribs are rectiradial, narrowly rounded, 

narrower than the interspaces, and number 12 or 13 for 

the shell diameter. 'They cross the dorsum but they are 

weaker on the dorsum than on the flanks or venter. The 

lateral and ventrolateral tubercles are equal in size, are 

flat topped, and cover two or three ribs. The space separating adjacent lateral tubercles is occupied by two or 

three ribs. A rib, though not present on the flank between a lateral tubercle and the dorsum, may be present 

in the area separating that tubercle from the equivalent 

ventrolateral tubercle; this feature is visible on one of 

Mantell's specimens (Spath, 1939, text fig. 196f). 

The larger specimen, 163 mm long, has end-whorl 

heights of 35.5 and 56 mm. It shows evidence of some 

lateral crushing, which may account for the elliptical 

cross section (fig. 2). Ribs are very narrowly rounded, 

rectiradiate on the elbow, and rursiradiate on the shaft. 

They number 10 for the diameter. Tubercles are flat topped and lie on one or two ribs. The space between adjacent lateral tubercles contains two or three ribs. An 

extra rib may be present here and there on that part of 

the shell ventral from the lateral tubercles. 

Although both specimens seem to be entirely septate, 

the suture is barely visible and cannot be accurately reproduced. It appears to be highly complex with very 

narrow and lengthy branches. 

Types.-Hypotypes USNM 166337, 166338. 

Occurrence.-Both specimens are from the basal bed 

of the Bridge Creek Limestone Member of the Greenhorn Limestone at USGS Mesozoic locality 22899 near 

A 

B 

FIGURE 2.-Cross sections, natural size, of Anisoceras plicatile (J. Sowerby) from USGS Mesozoic locality 22899 (fig. 1, loc. 26). A, Hypotype 

USNM 166337 at diameter of 29 mm. B, Hypotype USNM 166338 at diameter of 56 mm. 

Model, Colo. (fig. 1, loc. 26). They were associated with 

Inoceramus pictus J. de C. Sowerby, Sciponoceras gracile (Shumard) , Desmoceras ( M oremanoceras) scotti 

(Moreman), Oalycoceras naviculare (Mantell), Pseudocalycoceras dentonense (Moreman), Kanabiceras septemseriatum (Cragin) , and M etoicoceras whitei Hyatt. 

A very late Cenomanian age is indicated by the presence 

of the species Oalycoceras naviculare and by the genus 

Pseudocalycoceras. 

Family DESMOCERATIDAE 

Genus DESMOCERAS Zittel, 1884 

Type species-A.mmoniteslatidorsatus Michelin, 1838. 

Desmoceras has been described by many authors. 

Wright (1957, p. L370) summarized the generic characters as 

Moderately to very involute, inflated with depressed rounded 

subquadrate or oval whorl section; sigmoid constrictions form 

strong rounded ribs on outside of test, with dense striae or weak 

rounded ribs between them on outer part of side and venter. 

Suture with finely frilled elements and auxilaries in regularly 

descending series. 

Matsumoto ( 1954, p. 105) noted also that the proportion 

of the umbilicus to the diamete,r (umbilical ratio) was 

20 percent or less, and measurements presented by him 

(Matsumoto, 1953, p. 249, 250) for D. latidorsat1Jlln_ 

(Michelin), as well as for many examples of D. kossmat~ 

Matsumoto, show tJhat the ratio ranges from 11 to 18 

percent. 

Subgenus MOREMANOCERAS Cobban, n. subgen. 

Type species-Tragodesmoceras scotti Moreman, 

1942. 

This new subgenus differs from Desmoceras chiefly hy 

having a simpler suture with broade~ l~terallo?e and 

shorter auxiliary lobes (fig. 3). Constrictions, whiCh are 

present by the juvenile stages, disappear and then a~e 

rejuvenated in the late adult stage. The ~ubg~nus IS 

known only by the type species, which I behe~e Is very 

late Cenomanian in age. It has been found 1n Texas, 

Colorado, and Arizona. . 

The generic assignment of the type speCimen has been 

controversial. Moreman (1927, p. 94; 1942, P· 208) assigned it first to Pachydiscus and then t? Trago.desmoceras. Matsumoto ( 1960, p. 46) considered It a 

possilJle Onitshoceras Reyment ( 1954, P· 248) · Reyment's genus resembles M oremamocer~s in its form and 

sculpture, but its suture is very different. The two 

suture drawings presented by Reyment (1954, text figs. 

1h e) obviously differ from the sutures of M oremanoce;as and Desmoceras s.s. by having broad saddles and 
6 AMMONITE<S, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

" \ 

J 

B 

FIGURE 3.-Parts of the external suture of Desmoceras (Moremanooeras) scotti (Moreman) from the Eagle Ford 

Formation at USGS Mesozoic locality 19716 near Bells, Tex. A, Hypotype USNM 166345, X 6, at diameter 

of 18.5 mm (pl. 2, figs. 15-17). B, Hypotype USNM 166346, X 6, at dilameter of about 28 mm (pl. 2, figs. 20, 

21). 

long narrow lobes with slender branches. The lateral 

lobe of 11/ oremanocera8 is larger, broader and more 

conspicuous than that of De8moceras latidorsatwm 

(Michelin), the type species of Desmoceras. Michelin 

(1838, p. 101) did not illustrate the suture of his Ammonites latidorsatu8, but Salfelid ( 1919, text fig. 6) 

showed the con1plete suture (reproduced by Spatlh, 

1923, text fig. 9k). 

Desmoceras (M:oremanoceras) scotti (Moreman) 

Plate 2, figures 1-23; text figures 3-5 

1927. Pachydiscus sp. A, Moreman, Jour. Paleontology, v. 1, 

no. 1, p. 94, pl. 15, fig. 4. 

1942. Tragodesmoceras scotti Moreman, Jour. Paleontology, 

v. 16, no. 2, p. 208, pl. 33, fig. 8; text fig. 2d. 

1960. Onitshocems? soott (Moreman). Matsumoto, Kyushu 

Univ. Fac. Sci. Repts., Geology, v. 5, no. 1, p. 46, text 

figs. lOA-C. 

The type specimen, from the Eagle Ford Formation 

of Texas, may be a nearly complete adult body chamber. !foreman gave its diameter as 66 mm, umbilical 

width as 7 mm ( 11 percent), and maximum whorl width 

as 26 mm. The whorl section is higher than wide and 

has a well-rounded venter, broadly rounded flanks, and 

sharply rounded umbilical shoulder. Conspicuous 

rounded ribs, numbering six per half whorl, begin at 

the umbilical shoulder, trend straight across the flank, 

and arch forward on crossing the venter. Numerous 

striae parallel the ribs. Only bits of the last suture are 

preserved. 

Inasmuch as Moreman described only the one specimen, presentation of additional specimens from the 

Eagle Ford Formation seems advisable. An excellent 

collection taken from a concretion was made by H. R. 

Bergquist of the U.S. Geological Survey about 2 miles 

northeast of the center of Bells in northeastern Texas 
SYSTEMAITIC DESCRIPTIONS 7 

(USGS Mesozoic loc. 19716). This collection consists 

of one specimen nearly the size of the holotype and 10 

smaller ones 6-35 mm in diameter. The earliest whorls 

of the small specimens are very depressed (fig. 4), a 

character recorded by Matsumoto ( 1953, p. 248) in 

his generic diagnosis of Desmoceras. Matsumoto also 

noted that the later whorls tended to increase in height 

more rapidly than in width-a feature also apparent 

in D. ( M.) scotti (fig. 5). Constrictions first appear at 

a diameter of 7-8 mm and number three to four per half 

whorl. At a diameter of 10-11 mm, a rib rises on the 

apical side of each constriction and parallels the constriction as it arches forward on crossing the venter. As 

the shell enlarges, the constrictions become weaker and, 

on some specimens, seem to disappear. The ribs, however, 

become stronger and persist to the adoral end of the largest specimens. They number three to four per half whorl 

on the smaller specimens and six on the only large 

specimen (at a diameter of 54.7 mm). Striae parallel 

the constrictions and ribs. Closely spaced broad weak 

ribs are present on three individuals at diameters between 25 and 35 mm. One of these individuals, consisting of half a whorl (pl. 2, figs 11-14), shows no evidence of constrictions or the conspicuous bordering ribs. 

Desmoceras ( 11/ oremanoceras) scotti is represented in 

the U.S. Geological Survey collections from the western interior region by only two specimens. The larger 

(pl. 2, figs. 22, 23), 71.5 mm in diameter, is from the 

Bridge Creek Limestone Member of the Greenhorn 

Limestone in southeastern Colorado. It is an internal 

mold somewhat compressed owing to lateral crushing. 

The earlier half of the outer whorl lacks constrictions 

and the associated strong ribs; it is ornamented instead 

by low closely spaced broad ribs like those on some of 

/ 

I 

I 

I 

I 

\ 

\ 

A 

B 

FIGURE 4.-Diagrammatic outlines, X 4, of front 

views of Desmoceras (Moremanoceras) scotti 

(Moreman) from USGS Mesozoic locality 19716. 

A, Hypotype USNM 166339 at diameter of 6.5 mm. 

B, Hypotype USNM 166340 at diameter of 13 mrn. 

421-990 0 - 71 - 3 

FIGURE 5.-Whorl sections, X 25, at diameter of 

3 mm of Desmoceras (.Jloremanoceras) scotti 

(Moreman) from USGS M·esozoic locality 

19716. Hypotype USNM 166339. 

the Texas examples. At the beginning of the body chamber (diameter of 48 mm), the constrictions are rejuvenated and bounded on their ada pi cal side by strong 

ribs. Five of these constrictions and associated ribs are 

present on the last half whorl. Sutures are barely visible. 

The other example of D. (AI.) scotti (pl. 2, figs. 18, 

19) is an internal 1nold 49 mm in diameter from the 

Mancos Shale in northeastern Arizona. It has weak constrictions and strong border ribs, and the area between 

these sets is crossed by weak ribs of irregular height. 

The specimen probably represents the older part of an 

adult body chamber. 

Types.-Hypotypes USNM 166339-166348. 

Occ·urrences.-One specimen was found in the basal 

bed of the Bridge Creek Limestone Member of the 

Greenhorn Limestone near Model in southeastern Colorado (fig. 1, loc. 26), where it was associated with 

lnocerarnus pictus (J. de C. Sowerby), Anz'socera.'5 

plicatile ( J. Sowerby), Soiponoceras gracile 

(Shumard) , 0 alycoceras naviculare ( M·antell), Pse·udocalycoceras dentonen8e (Moreman) , K (J;'fUlbiceras septernseriaturn (Cragin) , and M etoicoceras whitei Hyatt 

all of very late Cenomanian age. The other specimen 

came from a limestone concretion at the base of the 

Mancos Shale on the north·western side of Black Mesa 

near Kayenta, Ariz. (fig. 1, loc. 31). Other fossils in the 

concretion include bwceram'll-8 pictus ( J. de C. Sowerby), Pycrwdonte newberryi (Stanton), Sciponoceras 

gracile (Shumard), W orthoceras qibbosu·m Moreman, 

and AI etoicocera.'5 1ohitei Hyatt. 
8 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

Family MUNm,RICE:RATIDAE 

Genus TRAGO·DESM.OCERAS Spath, 1922 

Type species.-Desmoceras clypealoides Leonhard, 

1897. 

Spath ( 1922, p. 127) defined this genus for certain 

ammonites in the subfamily Puzosinae that have a narrow crenulated venter. He n1entioned Desnwceras 

clypea.loides Leonhard (1897, p. 57, pl. 6, figs. 2a, b), 

Ammonites clypealis SchHl.ter (1872, p. 51, pl. 15, figs. 

9-14), A, hernensis Schluter (1867, p. 35, pl. 6, fig. 4), 

and Pu.zosia 111JUelleri de Grossouvre ( 1893, p. 172) as 

representatives of it. Matsumoto ( 1954, p. 111) recommended that Amm.onites hernensis SchHl.ter (1967, not 

1872) be assigned to Puzosia, and he stated that Puzosia 

muelleri might be a Nowakites. The other species are 

characterized by compressed whorl sections, fastigate 

venters, constrictions, and flexuous ribs that increase in 

strength toward the venter, which they cross with conspicuous forward arching. The suture resembles that of 

De.g-moceras. 

Tragodes1nocera'8 has been recorded only from Germany, France, Sweden, Madagascar, and the United 

States. The genotype, T. clypealoides (Leonhard), seems 

to have come from the Turonian of Germany, and all 

American examples of the genus are Turonian in age. 

30 I- I I I T I I 

~ 0 .. 8S 

Q._ 20 I- .. ~ 

Q 

~ 

~ 101-

<t: 

0 

::::; 

ClJ 

3 0 I I I I I 

0 10 20 30 40 50 60 70 80 

SchHl.ter (1876, p. 252) assigned his Ammonites alypeali'8 

to the Unter-Senon (Coniacian or Santonian) of Gern1any. A Santonian age "\Yas also assigned to the specimen from Sweden that was identified as Trag·odesmoceras cf. T. hernense (Schh1ter) by 0dum (1953, 

p. 24, pl. 4, fig. 3), as well as to the specimen from 

Madagascar described by Collignon ( 1966, p. 86, pl. 490, 

fig.1974) as the new species T. bererense. 

Tragodesmoceras carlilense Cobban, n. sp. 

Plate 3, figures 1, 2; plate 4, figures 1-16; plate 5, figures 

1-5 ; text figures 6-8 

This species is represented by 43 very well preserved 

specimens from limestone concretions in the lower part 

of the Carlile Shale of the Black Hills region. The specimens range in diameter from 12 mm to 160 mm. 

The umbilicus is sharply defined, and the umbilical 

ratios of all the specimens but one range from 21 to 26 

percent (fig. 6A). The exception is an individual with 

an umbilical ratio of 19 percent at a dia1neter of 104 mm. 

On whorls less than 30 mm in diameter, the umbilical 

wall is vertical with sharply rounded shoulders. The 

umbilical wall begins to slope a little at diameters between 30 to 35 mm, and this slope gradually increases 

as the shell enlarges. On the largest specimen, the 

A I I I f I I 

-

I I I _j I I I 

90 100 llO 120 130 140 150 160 170 

DIAMETER, IN MILLIMETERS 

40 B I I I I I I T T T I I 

__J 30- a: 

0 . : I 

~ 

LL . . ;i 20- . . I 

a: 

w 

Q._ 

(/) 

~ 10- a: 

0 I I I I I I I I I I I I 

0 10 20 30 40 50 60 70 80 90 100 110 120 130 

DIAMETER, IN MILLIMETERS 

FIGURE 6.-Scatter diagrams showing umbHical ratios in percent (A.) and number of ventral ribs in half a whorl (B) of Tragotlesmoceras carZilense, n. sp., from the lower part of the Carlile Shale at USGS Mesozoic localities 2179·2, 11190, 1119·2, 26372, 

D3754, D3743, D14J17, D1450, 12642, and 18872 (fig. 1, Iocs. 4, 5, 7-12, 14, and 15) . 
SYSTEMA!TIC DESCRIPTIONS 9 

umbilical wall forms an angle of 130° with the flank of 

the next inner ·whorl. 

The early whorls have stout sections with broadly 

rounded flanks and arched venters; later septate whorls 

have flatter flanks and higher and more narrowly 

arched venters. On the body chamber, the venter 

broadens and becomes well rounded (fig. 7). 

Constrictions, numbering 10-12 per whorl, are conspicuous on the larger inte,rnal molds. They are prorsiradiate and slightly flexuous and are bent forward on 

crossing the venter. They begin at the umbilieal shoulder 

and increase in strength as they cross the flank. Each 

constriction is bounded on its adapical side by a conFIGURE 7.-Section, natural size, through the 

holotype of Tragodesmoeeras carlilense, 

n. sp., at a diameter of 149 mm. USNM 

166349. 

spicuous rib. These ribs (primaries) are present on the 

smallest specimens, but constrictions on most speeimens 

are not well defined at diameters less than 40 or 50 mm. 

Two or three orders of ribs are present, and all are 

strongest on the outer part of the flank and venter (fig. 

6B). Primary ribs are sigmoidal, begin at the umbilical 

shoulder, and number 14 or 15 per '"horl at diameters 

less than 15 mm and 16 to 20 per whorl at diameters of 

15 to 60 mm. On the outer part of the flank, the primaries 

of most speeimens are separated by two or three secondary ribs of equal lengths. The ribs are strongest at 

diameters between 10 and 60 mm, and the primaries and 

the most conspicuous of the secondaries rise into rounded 

tubercles on the middle of the venter. The ribs greatly 

weaken on the adult specimens, and the mid-ventral 

tubercles disappear before the beginning of the body 

cha.mber. 

The suture (fig. 8) is characterized by a broad, short 

external (ventral) lobe, a broad trifid lateral lobe, and 

several bifid or trifid auxiliary lobes progressively decreasing in size to,vard the umbilicus. It resembles the 

suture of T. ely peale figured by Schl liter ( 1872, pl. 15, 

fig. 14). 

The holotype (pl. 3, figs. 1, 2; pl. 5, fig. 5; text fig. 7) 

may be an adult. It is 165 mm in diameter and has a 

whorl thickness of 54 mm and an umbilical ratio of 26 

percent. A little more than half the last whorl is body 

ehamber. 

Tragode8mocera.'3 carlilen8e is not as densely ribbed as 

T. clypealoide8 (Leonhard, 1897, p. 57, pl. 6, figs. 2a, b), 

which has about 40 ribs per half whorl as compared to 

18-35 for the Carlile species. Pu.zo[)ia 1n.uelleri de Grossouvre ( 1893, p. 172, ne'v name for A nnnonite8 hernensis Schluter, 1872, p. 40, pl. 11, figs. 12-14, and placed 

in Tragodes?nocera.'3 by Spath, 1922, p. 128), likewise, is 

n1uch more densely ribbed. Tragode8mocera.s hernen8e 

(SchUlter, 1867, p. 35, pl. 6, fig. 4) from the Turonian of 

Germany, is possibly the same age as T. carlilense and 

is as sparsely ribbed, but the umbilicus is wider ( 32 

percent at a diameter of 68 mm) and umbilical tubercles 

are present. A1nmonites clypealis Schluter (1872, p. 51, 

pl. 15, figs. 9-14), assigned to Tragode8nwoeras by 

Spath (1922, p. 127) but considered to be a Haploceras 

by Brauns (1875, p. 342), a :tiumie7'icera.'3 by de Grossouvre (1893, p. 157), and a Hau,ericera8 by Wegner 

(1905, p. 207), Stolley (1916, p. 90), and Riedel (1931, 

p. 693), is also more densely ribbed, and its inner whorls 

are smooth. 

Tragode8nwceraR carlilense differiS f1~om the slightly 

older T. ba.'3s'i Morrow ( 1935, p. 468, pl. 52, figs. la-c; 

pl. 53, figs. 3-5; text figs. 1, 3), from the Greenhorn 

Limestone of Kansas and Colorado, by having a slightly 

narrower umbilicus, stou:ter whorls, and more ribs per 
10 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

FIGURE &-External Slllture, X 2, of Tragodesmoceras carlilense, n. sp., at diameter of 124 mm (pl. 5, figs. 3, 4). Para type 

USNM 166357. 

whorl. Specimens from the Turoni,an of Oregon, described by AndeDson (1902, p. 100, pl. 4, figs. 107-109; 

1958, p. 221, pl. 27, figs. 2, 2a) as the new species 

Desmoceras ashlandicurn and Pachydiscus oregonensis 

and regarded as the one species Tragodesmoceras ashlandimnn by MatBumoto (1959, spec. v. 1, p. 26), differ 

from T. carlilense by tending to have a slightly wider 

umbilicus and coarser and fewer ribs. 

Types.-Holotype USNM 166349, paratypeB USNM 

166350-166357. 

Occurrences.-Tragodesmoceras carlilense is known 

with certainty only from the lowest unit (Pool Creek 

Shale Member) of the Carlile Shale around the flanks 

of the Blaek Hills uplift in northeastern Wyoming and 

southwestern South Dakota (fig. 1, locs.1-15). It oceurs 

in gray limestone eoncretions that also eontain Oollignoniceras 1.ooollgari (Mantell), an ammonite usually 

assigned an early or middle Turonian age. T-ragodesnwceras carlilense is the species listed as Tragodesmoceras, n. sp., in many publications concerning the geology of the flanks of the Black Hills (Cobban, 1951, p. 

-2188; Brobst, 1961, p. 19; Brobst 'and Epstein, 1963, 

table 1; Mapel and Pillmore, 1963b, p. N46; a.nd Robinson, Mapel, and Bergendahl, 1964, p. 67). It has also 

been listed as Tragodesmocera8 sp. and "Puzosl'.a" n. sp. 

(Mapel and Pillmore, 1963a, p. M36). Sparse impressions of a Tragodesmoceras in the Fairport Chalky 

Shale Member of the Carlile Shale of l{ansas and in the 

equivalent calcareous shale near Boulder, Colo. suggest 

that T. carlilense may occur there too, but not one of the 

specimens is well-enough preserved for positive 

identification. 

Family ACANTHOCERATIDAE 

Genus PARACOMPSOCERAS Cobban, n. gen. 

Type species.-Paraeompsoceras 7andisi Cobban, n. 

sp. 

This genus is proposed for ammonit~s that have adult 

whorls similar to those of Acmnpsoceras Hyatt ( 1903, 

p. 111), whereas the juvenile whorls have tubercles like 

those on juveniles of Acanthoceras Neumayr (1875, p. 

929). Paracont.psoceras is moderately involute with umbilieal Datios ordinarily 25-30 percent. The umbilical 

shoulder is rounded but well defined, and the umbilical 

wall is very steeply sloping or even vertical. Early 

whorls are quadrangular and ornamented by conspicuour ribs and tubereles. Each rib has a lower and an 

upper ventrolateral tubercle, and every other rib rises 

from an umbilieal tubercle. On the early whorls a clavate 

siphonal tubercle is present for each rib. All tubercles 

and the shorter ribs disappear as the shell enlarges, but 

the longer ribs tend to persist to the last chambered 

whorl where the,y are strongest on the lowe,r (dorsal) 

half of the flank. Flanks and venter are flattened on the 

last ehambered whorl and on most of the body chamber, 

and the whorl section is higher than wide. Most or all of 

the adult body ehamber is smooth. The suture is about 

as incised as that of Acanthoceras, but the branches of 

the lobes are not quite as long and digitate as those of 

Acompsoce1'a8. The lateral lobe, which has a broad central stem, is about half as wide as the asymmetrically 

bifid first lateral saddle. Specimens representing this 

genus are scarce, and all collected to date are late 

Cenomanian in age. 

Paracompsoceras landisi Cobban, n. sp. 

Plate 2, figures 24----:26; plate 6; plate 7; plate 8; plate 9, figures 

5-8 ; text figures 9-11 

The type lot, from USGS Mesozoic loeality D6130 

(fig. 1, loc. 34), eonsists of only six specimens, and all 

represent complete adult shells or parts of adult shells. 

Early whorls and sutures were seen best in the holotype 

(pl. 6; pl. 9, figs. 5-8; text figs. 9, 10) which was taken 

apart; plaster casts, which are in the U.S. National 

Museum (Washington, D.C.) and in the U.S. Geological 
SYSTEMAJTIC DESCRIPTIONS 11 

Survey's collections of fossils at the Federal Center 

(Denver), were made of two of the inner whorls before 

the specimen was restored. 

Whorls less than 43 mm in diameter are not preserved 

in any of the specimens. At this diameter the intercostal 

section is very stoutly elliptical and only slightly higher 

than wide (text fig. 9A). The costal section is squarish 

and distinctly acanthoceratid with umbilical, lower and 

upper ventrolateral, and siphonal tubercles. Maximum 

width is at the umbilical tubercles. A half whorl 70 llllll 

A 

\ 

\ 

/ 

"'-, I ............ _-"' 

I 

I 

I 

I 

B 

c FIGURE 9.-Cross sections, natural size, of whorls of the bolotype of Paracompsoceras landisi, n. sp. USNM 16635-8. A, Section at a diameter of about 56 mm. B, Section at a diameter of 

about 120 mm. C, Section at a diameter of 202 mm. 

in diameter has 10 rectiradiate ribs of which every other 

one (the primary) originates frmn a strong nodate or 

bullate umbilical tubercle. The shorter ribs (the secondaries) rise near the middle of the flank and these, as well 

as the longer ribs, bear nodate lower ventrolateral tubercles and similarly sized clavate upper ventrolateral tubercles. The flattened venter has a low clavate siphonal 

tubercle for each rib. 

As the shell enlarges, all tubercles weaken and disappear, the flanks flatten, and the whorl section becomes 

rectangular to trapezoidal (text fig. 9B). On the holotype, the lower ventrolateral tubercles disappear at a 

diameter of about 70 m1n and the upper ventrolateral 

ones disappear at a diameter of 105 mm. The longer ribs 

remain strongest and bullate near the umbilical shoulder, whereas the shorter ones gradually "\Veaken. T·welve 

primary and secondary ribs are present on half a whorl 

of the holotype at a diameter of 135 mm (pl. 9, figs. 7, 8). 

The secondary ribs disappear near the beginning of the 

last septate whorl, but in some specimens the pri1nary 

ribs persist to the end of that whorl or even onto the 

older part of the body chamber. 

The body chamber begins at a diameter of about 220 

mm on the holotype, and at '217 a.nd 257 nun on the two 

figured paratypes ('p~s. 7, 8). The body chamber is 

largely or entirely smooth. None of the specimens has 

tlhe peristome preserved. The largest spe.cimen collected 

has a diameter of :no mm (par~atype USNM 166395). 

The holotype is a moderately stout shell of which the 

last quarter whorl is part of the body chamber. It has 

an umbilical ratio of 30 percent at a diameter of 135 mm 

and 29 percent at 1a dimneter of 236 mm. An external 

suture on the last septate whorl is shown in figure 10. 

Although the specimens are few in number, these few 

suggest a considerable range in stoutness; the holotype 

lies in the 1niddle of this range. The slenderest specimen 

(pl. 8), 275 mm in diameter, has a narro"\v rectangular 

section (text fig. 11A) with the greatest width in the 

middle of the flank. The stoutest individual (pl. 7), 

287 1111n in diameter, has a rounded body chamber section (text fig. 11B). 

FIGURE 10.-External suture, natural size, of the holotype of 

Paracompsoceras landisi, n. sp., at a diameter of 115 mm. 

USNM 166358. 
12 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

I 

I 

/ 

/ 

/ 

.... __ _ 

A 

I 

I 

I 

B 

' ' \ 

\ 

\ 

\ 

\ 

\ 

\ 

'-

/ 

/ 

/ 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

FIGURE 11.-,Vhorl sections, natural size, through the body chambers of sh:•nder and stoUJt specimens of Paracrnnpsoeeras landi.s·i, 

n. sp. A, P'aratype USNM 1663.61 (pl. 8). B, Para type USNM 166300 (pl. 7). 

The species was na·med for Edwin R. Landis, of the 

lT.S. Geologieal Survey, who colleeted most of the 

specimens. 

Adult specimens of P. landisi resemble some adult 

specimens of Acornpsoceras. The bullate ribs and the 

smooth body chamber of the robust form of P. landisi 

(pl. 7) reeall the adult speeimen described by Schluter 

(1871, p. 1, pl. 1, figs. 1-4; pl. 2, fig. 1) as Anunonites 

oochu/tnensis and later designated the type of Acornpsoceras by Hyatt (1903, p. 111). The slender form of 

P. landisi (pl. 8), with its smooth outer whorl, resembles that of the adult specimen of Aconupsoceras essendiense ( Shlilter) var. 1nadagruscarien8is Collignon 

( 1964, p. 108, pl. 356, fig. 1569). The acanthoceratid 

juvenile whorls and the smooth or nearly smooth adult 

body chamber of P. landisi are reminiscent of Nigericeras, but that genus lacks the flat-ventered stage and 

its suture is much simpler. 

Types-Holotype USNM 166358, paratypes USNM 

166359-166361, 166395. 

Occurrences-Pw'acompsoceras landisi has been 

found at four localities in nortlnvestern New Mexico 

(fig. 1, locs. 32-35). The best dated collection is from 

lTSGS Mesozoic. locality D7084 north 3 Iniles of Laguna (fig. 1, loc. 35), where the speeies occurs just below 

a sandstone mapped as the second sandstone mmnber 

of the Mancos Shale (Moench, 1963). Other ammonities 

found just below this sandstone include Acanthoceras 

ampldbolum Morrow and T'ltnilites acutws Passy subsp. 

americanu.s Cobban and Scott, which mark the A. amphibolum Zone of the upper Cenomanian of the western 

interior. 

Dr. J. Dan Powell, of the lTniversity of Idaho at 

Moscow, has shown me part of an am1nonite from Cerro 

de Muleros near El Paso, Tex., that may be P. land1'si. 

It was said to have come fron1 subdivision 10 of Bose 
SYSTEMATIC DESCRIPTIONS 13 

(1910, p. 29) or the Boquillas Formation (:Strain, 

1968). 

Genus CALYCOCERAS Hyatt in Zittel, 1900 

Type species.-Am;m.onites navioularis Mantell, 1822. 

'The characteristics of Oalycoceras have been summarized by M·atsumoto, Saito, and Fukada ( 19·57, p. 

8-9) as follows : 

Whorls are typicaUy depressed to sub-rounded, but sometimes 

not so inflated, having an arched venter. Ribs are elevated but 

relatively narrow and consist of alternating long and 'Short ones 

up to the full-grown ·stage. ·In the more or less young stage 

median-ventral, outer and inner ventrolateral and umbilical 

tU:bercle.s are well developed. As ·a general tell'dency the outer 

tubercles are sooner or la'ter weakened or nearly completely 

obsolete as the shell grows on, whi:le the ribs are prominent 

throughout life, crossing 'the external side without weakening. 

However in 'Some cases the peripheral tubercles persist to, or 

rejuvenate on, the full-grown, outer 'Whorl. E'ven in ~such case.s 

the ribs are still prominent. The suture is simila·r to that of 

Jlf antelliceras. 

0 alycoce1·as is widely distributed in rocks of Cenomanian age. 

Calycoceras naviculare (Mantell) 

Plate 1, figures 1-3; plate 10, figures '1-8; plate 11, figures 1...;5; 

plate 12, figures 1, 2; plate 13, figures 1-5; plate 14, figures 

1-3; plate 15, figures 1, 2; plate 16, figures 1, 2; plate 17; 

text figures 12-14 

1822. Ammonites navicularis Mantell, The fossils of the South 

Downs or i:Uustrations .of 'the geology of ·sussex, p. 198, 

pl. 22, fig. 5. 

1893. A_oanthoooras naviculare (ManteU). Sacco, 'Soc. Be'l.:ge 

Geologie, Paleontologie et Hydrologie Mem., v. 7, rp. 18, 

pl. '2, fig. 1. 

1898. Acwnthocera.s naviculare ('Mantell). Ohoffat, RecueH 

d'etudes paleontologique·s sur la faune cretacique du 

Portugal, v. 1, 2d ser .. p. 72, pl. 4, figs. 6a, b; pl. 6, 

figs. 1, 2a, b. 

1900. Oalycoceras (Ammonites) navicularis (1Sharp) (sic). 

Hyatt, in Zi'ttel, Text-book of palaeontology (Eastman 

translation), p. 589. 

1912. Fagesia. navicularis ('Mantell). De Orossouvre, ·Soc. Sci. 

Nat. l'Quest France Bull., ser. 3, v. 2, p. 28, text fig. 3, 

pl. 3, figs. la, b. 

1919. Ammonites naviculavis Mantell. Orick, Malacological Soc. 

London Proc., v. 13, p.154, pl. 4. 

1926. Metacalyooceras naviculare (1Mant~H). ·Spath, Geol. :M-ag., 

v.63,no. 740,p.83. 

1926. Metacalycoceras grossouvrei 'Spath, Geol. Assoc. [London] Proc., v. 37, pt. 4, p. 431. 

1931. Acanthoce1·as borgesi Douville, Lisboa Univ. Mus. e Lab. 

Min. e Geol. Bol., ser. 1, v. 1, no. 1, p. 32, text fig. 2, pl. 2, 

figs. 3a, b, 4. 

1931. M etacalycoceras borgesi (Douville). Spath, Palaeonto~ 

graph. Soc. Mon., v. 83, p. 316. 

1935. Acanthoceras ( Oalyooceras) nat,iculare (Mantell). Karren berg, Palaeontographica, v. 82, pt. A, p. 129, text 

fig. 1. 

1937. Oalycoceras (Metacalycoceras) naviculare (Mantell). 

Collignon, Madagascar S.ervice Mines Annales Geot, 

pt. 8, p. 44-49. 

1957. Oalycoceras naviculare (Mantell). Wright, in Moore, R. 

C., ed., Treatise on invertebrate paleontology, Part L, 

Mollusca 4, p. IA13, text figs. 531-6, 532. 

1957. Oalycoceras naviculare (Mantell). Matsumoto, Saito, 

and Fukada, Kyushu Univ. Fac. Sci. Mem., ser. D, 

Geology, v. 6, no. 1, p. 9, 10. 

1965. Oalycoceras grossouvrei Spa'th. Collignon, Annales 

Paleonrtologie, v. 51, p. 172, pl. B, figs. 2a, b. 

1968. Oalycoceras naviculare (Mantell). Sastry, Rao, and 

Mamgain, Geol. Soc. India Mem. 2, pl. 1, figS:. 5, 6. 

1969. Oalycoceras naviculare (Mantell). Kennedy, Geologists' 

Assoc. Proc., v. 80, pt. 4, pl. 21. 

The original description of the type specimen is inadequate (Mantell, 1822, p. 198). The specimen was 

illustrated by a simple drawing prepared by Mantell's 

wife and shows an oblique ventral view chiefly of the 

last half whorl (Mantell, 1822, pl. 22, fig. 5). It was said 

to have come from the "upper Chalk, Offham" 

(England). 

Almost a century later, Crick ( 1919, p. 154-155) refigured the holotype and described it as follows: 

Mantell's figure of the type-specimen is, very misleading. The 

fossil, which is now in the British Museum collection (re,gister 

number 5681), is very depres~ed, having been diSitorted by pressure ; its longest diameter is 149 mm. ; many of the ribs are 

very much worn, but some that are well-preserved s:how that 

originally they were narrowly rounded and of the soame width 

as, or even a little narrower than, the intervening spaces; the 

ribs are straigh1t, and as a rule alternately longer and shorter, 

but towards the anterior end of the specimen there are irre,gularities in this respect. As a rule each longer rib commences· 

at the suture [umbilical seam] of the shell and, increasing in 

strength as it passes across the inner area of the whorl, is raised 

into a more or less prominent compressed tubercle on the umbilical margin, whence the rib passes straight across the broadlyrounded whorls without any indications of tubercles. 

Crick illustrated the specimen by rear and side views 

which reveal ventrodorsal crushing. Ribs number 17 for 

half a whorl at a diameter of about 149 mm. Tuhe·rcles 

other than umbilical ones are lacking. 

Sharpe (1856, p. 39, pl. 18, figs. 1-3, 5, 8) illustrated 

four specimens that he assigned to Ammonites nav-iculari"f. All had ventrolateral tubercles, and two had 

siphonal tubercles also. This assignment of tuberculated 

specimens to A. naviculari;.s led to much confusion for 

later authors because, in creating the generic name 

Oalycocera,s, Hyatt (in Zittel, 1900, p. 589) merely 

stated '"0. (A1nrn.) na,vic'1tlaris, Sharp sp." as the type. 

Spath (1921, p. 315), in commenting on the resemblance of the inner whorls of the Aptian Oheloniceras 

gottschei (Kilian) to Oalycoceras na·viculare, remarked 

that Mantell's type specimen 'vas "useless" and "too 

worn and scraped about to show any tubercles * * * 
14 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

some of the ribs being artificially carved, or at least 

scraped, and the original shrupe of the whorl is quite 

unrecognisable." Accordingly, Spath selected as a lectotype a specimen that had been illustrated by Sharpe 

(1856, pl. 18, figs. 1, 8) as an example of Ammonites 

navioularis. Sharpe's lateral view showed double umhilical tubercles, and Spath mentioned that the specimen 

had lower and upper ventrolateral tubercles. A few 

years later, Spath (1926a, p. 83) believed that the specimen he had selected as 1the lectotype was really a lJ/ antelliceras, and he created the name Jf. cantianum 

for it. He further stated that "Calycoceras is synonymous with M antellicer.as" and that "since it is also impossible to use the generic name Calycoceras * * * the 

new name Metacalycoceras gen. nov. is suggested, type 

to be the example figured by d'Orbigny." The specimen 

from Sarthe, France, described by d'Orbigny ( 1840, p. 

340, pl. 103, figs. 1-3) as Ammonites mantelli Sowerby 

and later referred by him ( d'Orbigny, 1850, p. 146) to 

A. navicularis, was subsequently refigured by Collignon 

(1937, p. 48, pl. 10, figs. 1, 1a, 1b), who named it lJ!etacalycoceras orbignyi. It resemble Mantell's Ammonites 

navicularis in that it lacks ventrolateral and siphonal 

tubercles, but it differs in that it has more slender 

whorls. 

The problem of Calycoceras and the species naviculare was reviewed again in 1937 by Spath (p. 278-

~80) and Collignon (p. 44-49). Spath concluded that 

his 111 etacalycoceras was a synonym of Calycoceras. 

Collignon, however, regarded lJ! etacalycoceras as a 

subgenus of Calycoceras that was characterized by 

swollen whorls with rounded or transversely ellipical 

sections, by rather numerous thick ribs tending to curve 

backward a little, and by only a few tubercles or an 

early disappearance of tubercles. Mantell's Ammonites 

navimtlaries was assigned to this subgenus. 

Wright and Wright (1951, p. 25) regarded Metacalycoceras as a synonym of Calycoceras. They pointed 

out that Hyatt's designation of Calycoceras 

(Ammonites) navicular·e Sharpe sp. was "nomenclatorially irregular" and that according to the International Code of Zoological Nomenclature "a nominal 

species once selected as type remains the type. Consequently the type species of this genus [ Calycoceras] 

is C. 'IW'l'iculare (Mantell)" and not one of Sharpe's 

specimens. Wright and Wright (1951, p. 26) also noted 

that C. naviculare was "a definite and distinct late form 

of the genus." 

Specimens resembling Mantell's type in their general 

appearance and by their lack of ventrolateral and 

siphonal tubercles have been illustrated from Portugal 

(Choffat, 1898), France (de Grossouvre, 1912; Sacco, 

1893), Angola (Douville, 1931), Algeria (Collignon, 

1965), and India (Sastry, Rao, and Mamgain, 1968). 

The species has also been recorded from Spain (Karrenberg, 1935, p. 129; ':Viedmann, 1959, p. 711, 720, and 

1964, p. 109), Tunisia (Pervinquiere, 1907, p. 281), and 

questionably recorded from Madagascar (Collignon, 

1964, p. 126, pl. 365, fig. 1596) and Japan (Matsumoto, 

1959, p. 64). 

Choffat ( 1898, p. 72, pl. 4, figs. 6a, b; pl. 6, figs. 1, 2a, b) 

figured as Acanthoceras naviculare a small dorsoventrally crushed specimen and a larger uncrushed specimen from the Cenomanian of Portugal. The smaller 

specimen, about 47 mm in diameter, has 18 ribs per half 

whorl. The larger specimen has 16 ribs per half whorl 

at a diameter of 125 1nm and an umbilical ratio of 25 

percent. Both specimens are very stout and have rectiradiate to slightly rursiradiate ribs that alternate in 

length. Ventral tubercles are absent on one specimen 

and probably absent on the other. I regard both as 

examples of Calycoceras naviculare, although Matsumoto (1959, spec. v. 1, p. 78) assigned them to C. stoliczkai Collignon. 

De Grossouvre (1912, p. 28, pl. 3, figs. 1a, b) figured 

a stout specimen 82 mn1 in diameter that has an umbilical ratio of 28 percent (1neasurements given by Collignon, 1965, p. 172). The slightly rursiradiate ribs 

alternate in length and they number 22 per half whorl. 

This specimen, designated F agesia navicuiaris by 

de Grossouvre, was said to have come from the lower 

Turonian (Salmurien) of Touvois, France (Loire 

Inferieure). It seems to be typical of Calycoceras naviculare, although Spath (1926b, p. 428, 431) regarded 

it to be a new species-111 etacalycoceras grossouvrei. 

Douville (1931, p. 32, pl. 2, figs. 3a, b, 4; text fig. 2) 

figured two very well preserved uncrushed specimens 

from Angola which he considered to be a new species---

Acanthoceras borgesi. One specimen, of which only the 

ventral view is shown, is 35 min in diameter. The other 

specimen, illustrated by two views, is 100 mm in diameter and has an umbilical ratio of 30 percent and 16 ribs 

per half whorl. Douville noted the close resemblance in 

form and ornamentation of his specimens to ~1ante1Ps 

specimen of Am1nonites navimdaris, but he believed his 

material should be con8idered a new species because of 

differences in the suture pattern. Mantell, however, did 

not illustrate a suture, and Douville regarded the suture 

drawing presented by d'Orbigny (1840, pl. 103, fig. 3) 

as representative of the species navimtlare. Wright 

(1957, text figs. 531-6, 532-1) considered Douville's 

Acanthoceras borgesi as a typical Calycoceras 11.-aviculare, and he reproduced Douville's photographs as an 

example of the species. I concur with Wright's interpretation and regard Douville's species as C. naviculare. 
SYSTEMA1

TIC DESCRIPTIONS 15 

Collignon ( 1965, p. 172, pl. B, figs. 2a., b) described a 

specimen from the upper Cenomanian of eastern Algeria and assigned it to 0. grossmrcrei (Spath). The 

dia1neter is 104 m1n and the umbilical ratio is 25 percent. Ribs alternate in length, and they number 19 on 

the last half whorl. The specimen was said to be ahnost 

identical to the one described from Touvois by de Grossouvre (1912, p. 28, pl. :3, figs. 1a, b) as Fagesia naviculaPis. Although de Grossouvre said his example ca1ne 

frmn the lmver Turonian ( Salmurien) , Collignon believed it n1ore likely came from the upper Cenmnanian. 

Collignon's specimen, 'Y hich apparently lacks tubercles 

on the ventral part, is interpreted herein as a 

0. navioulare. 

Several ammonites described and illustrated as examples of Oalycoceras na·viculare have been assigned 

to other species. The slender English specimen described 

as Ammonites naviculm·i8 by J. de C. Sowerby (1827, 

p. 105, pl. 555, fig. 2) has been assigned to Am.tnon£tes 

[ Oalycocera.~] gentmli Brongniart by Pictet (1863, p. 

52) and Crick (1919, p. 156). All four English specimens figured by Sharpe ( 1856, p. 39, pl. 18, figs. 1-3, 

5-8) as A. navicularis have been assigned to other 

species by Spath ( 1921, p. 315; 1926a, p. 82-83) and 

Wright and Wright (1951, p. 37). A tuberculated specimen from Bohemia, assigned to Acarntlwceras naviculm·e by Laube and Bruder (1887, p. 239) and closely 

compared to Sharpe's specimens, does not seem to be 

true Oalycocera.~ 1wviculare. Two robust specimens from 

India figured as A. 1woicularis by Stoliczka (1865, p. 

73, pl. 39, figs. 2-4) have been renamed Oalycoceras 

(ill etacalycoceras) stoliczkai by Collignon (1937, p. 

48). Boule, Lemoine, and Thevenin (1907, p. 30, pl. 8, 

figs. 1-2) figured two specimens from Madagascar as 

Acantlwceras navicnlare. but neither is that species 

according to Spath (1921, p. 315) and Collignon (1937, 

p. 48) . Another specimen from Madagascar described 

by Collignon (1931, p. 84, pl. 9, figs. 4, 4a, b) as Acantlwceras ( Oalycoceras) naviculare has ventrolateral 

tubercles, a feature which I believe excludes it from 

assignment to that speeies. 

An1monites closely resembling Mantell's holotype, as 

well as comparable specimens figured by Choffat (1898), 

de Grossouvre (1912), Douville (1931), and Collignon 

( 1965), are present in the basal bed of the Bridge Creek 

Limestone ~fember in the Model dome area of southeastern Colorado (fig. 1, locs. 17-28). They resemble 

the European and African specimens in their general 

form, density and arrangement of ribs, presence of 

umbilical tubercles, and lack of other clearly defined 

tubercles. Thirty-one specimens are suitable for rib 

counts and most are suitable also for umbilical ratio 

421-990 0- 71 - 4 

TABLE 2.-Dimensions and rib counts of Calycoceras naviculare 

(Mantell) 

U.S.N.M. No. Diameter Umbilical Umbilical Ribs per (mm) width (mm) ratio half whorl 

166362 ____________ 44. 6 12. 3 0. 28 20 

65. 3 17.3 . 26 21 

95. 4 27.0 . 28 ca. 25 

166363 ____________ 56. 7 13. 1 . 23 19 

72. 6 18. 6 . 26 20 

166372 ____________ 72. 1 18. 8 . 26 18 

94. 3 2.5. 7 . 27 18 

166378 ____________ 64. 8 -------------------- 21 

106. 0 32. 0 . 30 20 

166376 ____________ 68. 0 -------------------- 19 ca. 157. 0 -------------------- 15 

166381 ____________ 71. 3 20. 4 . 28 18 

160. 0 -------------------- 17 

166371 ____________ 71. 0 -------------------- 18 

166368 ____________ ca. 83. 0 -------------------- ca. 22 

166370 ____________ 86. 0 -------------------- 21 

166386 ____________ 93. 0 26. 0 . 28 20 

128. 5 -------------------- 16 

178. 0 -------------------- 16 

166369 ____________ 96. 0 -------------------- 17 

166382 ____________ 101. 0 27. 5 . 27 21 

138. 0 3.5. 8 . 26 20 

166390 ____________ 101. 5 29. 7 . 29 18 

166383 ____________ 102. 2 28. 4 . 28 19 

166367 ____________ 103. 8 29. 2 . 28 20 

148. 0 43. 0 . 29 18 

166388 ____________ 107. 0 -------------------- 22 

166375 ____________ 110. 0 32. 8 . 30 23 

158. 0 4.5. 4 . 29 22 

166384 ____________ 112. 0 30. 0 . 27 21 

166373 ____________ 112. 0 31. 5 . 28 19 

133 .. 5 39. 0 . 29 18 

166385 ____________ 113. 0 30. 3 . 27 18 

166364 ____________ 118. 0 33. 0 . 28 20 

166379 ____________ 123. 0 34. 6 . 28 15 

173. 0 .53. 6 . 31 13 

166387 ____________ 126. 0 38. 9 . 31 19 

166394 ____________ 127. 0 34. 6 . 27 16 

198. 0 61. 3 . 31 1.5 

166374 ____________ 128. 0 39. 0 . 30 18 

167. 0 .50 .. 5 . 30 17 

166365 ____________ 136. 0 43. 3 . 32 19 

173. 0 .54. 8 . 32 17 

166393 ____________ 146. 0 43 .. 5 . 30 17 

166377 ____________ 1.59. 0 46. 0 . 29 17 

166366 ____________ 166. 0 44. 3 . 27 19 

220. 0 68. 0 . 31 18 166389 ____________ 220 .. 5 64. 3 . 29 15 

166391 ____________ 239. 0 71. 7 . 30 12 

determinations. These measurements a.re given in table 

2 and shown in figure 12. 

The umbilical ratios, which range from 23 to 32 percent, gradually inorease as the shell enl:uges (fig. 12) . 

The umbilical wa.ll is steep and slightly rounded. The 

umbilical shoulder is well rounded and merges evenly 

into the broadly rounded flank. 

~fost whorl sections are wider than high (fig. 13B, 

D-H), but for a few inclivichrals they may be equal in 

size or a little higher than wide (fig. 13A, C). The 

venter is broadly rounded on juveniles; it tends to 

become very broadly rounded or even a little flattened 

on adults. 
16 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STAT'ES 

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= I 

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40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 

DIAMETER, IN MILLIMETERS 

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0 

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40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 

DIAMETER, IN MILLIMETERS 

FIGURE 12.-SJCatter diagrams showing umbilical ratios in percent (A) and number of ribs in half a whorl (B) of Oa.lycoceras 

naviculare (Mantell) from the basal bed of the Bridge Creek Limestone Member of the Greenhorn Limestone at USGS 

Mesozoic localities 18676, 18678, 18683, 18686, 22899, and D6530 (fig. 1, locs. 19-21, 24, 26, 27). Dots connected by lines 

represent meaSIUrements on sdngle specimens. 

Ribbing is conspicuous on all specimens. It is 

rectiradiate on juveniles and slightly rursiradiate on 

adults. The ribs are strong, rounded, and as wide as, or 

a little narrower than, the interspaces. They number 

12 to 25 per half whorl but the number tends to decrease 

as the shell enlarges (fig. 12B). Most specimens have rib 

counts between 15 and 22. The ribs are as strong on the 

venter as on the flank. Every other rib ordinarily begins 

at the umbilical se3Jm, rapidly increases in height on 

crossing the umbilical wall, and forms a sharply rounded 

tubercle on the um!bilical shoulder. This pri·ma.ry rib 

then continues straight across the flank and venter. At 

or near the beginning of the flank, a secondary rib 

arises !betwe•en adjacent primaries and becomes as strong 

as the prim'aries before crossing the venter. On a very 

few individuals, two secondaries may be present between a pair of primaries on some pa.rt of the shell (pl. 

12, fig. 1 ; pl. 13, fig. 2). More commonly, at some diameter between 100 ·and 120 m:m, a primary rib on one 

side will become a secondary rib on :the opposite side, 

and all subsequently formed ribs will behave in this 

rn3Jnner (pl. 16, fig. 1). A simiJ!ar rib arrangement is 

visible on the rear v~ew of Acanthoceras [Oalycoceras] 

borgesi Douville. ( 19~31, pl. 2, fig. 3h). 

Beginning at a diameter between 85 and 90 mm, each 

rib on some specimens becomes slightly raised at the 

ventrolateral ma.rgin as though a tubercle was albout to 

form. On these specimens the ribs flrutten a little on crossing the venter, and this cha,racter comrbined with the 

incipient tubercle produces a distinct angula.rity to the 

costa1l whorl section (pl. 11, fig. 5; text fig. 13E). A 

similar feature apparently was observed on some of the 

Euvopean examples of 0. na~oiculare by Matsumoto 

(1959, spec. v. 1, p. 81) who noted that "On the outer 

whorl of 0. naviculare * * * sometimes the ventrolateral tubercles are rejuvenated." 

Only one specimen (hypotype USNM 166394, diameter of 198 mm) reveals part of the adult aperture, 

buJt not enough of it remains to show its shape. The last 

three ri!bs are crowded a little, and each may have extended to the umbi1lical seam. 

Bits of the suture a:re preserved on very few specimens. Figure 14 shows the lateral lobe on one indi vid ua,l. 

It is broad and little incised and resembles the lateral 

lobe of the suture figured by l{arren!berg ( 19~35, text 

fig. 1). 

Types.-Hypotypes USNM 166362-166394. 

Occurrences.-0 alycoceras navimdare has been found 

in the western interior of the United States only in 

southeastern Colorado and south western Kansas (fig. 

1, J.ocs. 16-28, 30). It occurs at or near the base of the 

FIGURE 13.-Gross sections of whorls, natural size, of Oa.lyoocera.s naviculare (ManteU). A, USNM 166367 at diameter of 

about 13.9• mm (pl. 15, figs. 1, 2). B, USNM 166393 at diameter 

of 105 mm. 0, USNM 166378 at diameter of 86 mm (pl. 13, 

figs. 1-3). D, USNM 166373. at diameter of 128 mm (pl. 10, 

fig. 8; pl. 11, figs. 4, 5). E, USNM 1663891 at diameter of about 

1140 mm. F. USNM 166372 at diameter of 75 mm. G, USNM 

166380 (pl. 10, figs. 3, 5). H, USNM 166366 at diameter of 183 

mm (pl. 17). 
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SYSTEMATIC DESCRIPTIONS 

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18 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

' \ 

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FIGURE 14.-l.Jaterallobe, X 2, at a diameter of 73 mm of the specimen Olf 

Oalycoceras naviculare (Mantell) shown on plate 10, figure 6. Arrow 

marks the middle of the venter ; dashes mark the umbilical seam. HYIPOtype USNM 166372. 

Bridge Creek Limestone Member of the Greenhorn 

Limestone. Assooi·ated fossils, of very late Cenomani'an 

age, include Inoceramus pictus (J. de C. Sowerby), 

S ciponoceras gracile (Shumard), Pseudocalycoceras 

dentonense (Moreman) , K anabiceras septem-8e'riatum 

(Cragin), and JJJ etoicoceras whitei Hyatt. 

Family VASCOCERATIDAE 

Genus NIGERICERAS Schneegans, 1943 

Type species.-Nigericeras gignmaci Sehneegans, 

1943. 

There is some question regarding the date of Sohneegans' genus. Sehneegans (1943, p. 118) ga.ve the date ·as 

1939, but he did not list a referenee of that date in his 

bibliography. I have not suecee:ded in finding such a 

reference. Selmeegans' ( 1934) earlier work reported 

briefly on these fossils, but the new genus was not proposed at that time. Until the source of the 1939 date is 

determined, I am following Wright (19·57, p. L418) 

in assuming that Schneegans' 1943 report is the source 

of the name. 

Nigericera.rs was proposed for am1nonites tha,t seem 

transitional from Acantlwceras to V ascoceras. Inner 

whorls are riblbed and typically aeanthoceratid and have 

umbilioal, lower and upper ventrolateral, and siphorrral 

tubercles. On the adult body cha:ll1ber, the ribs beeome 

greatly weakened or disappear, and the ventrolateral 

and siphonal tube,rcles disappear. The suture resembles 

that of both Acanthoceras and Vascoceras. 

The genus is known only from lower Turonian strata., 

and most records are from Nigeria and Niger. Outside 

of Africa, the genus has been recorded from Israel 

(Freund and. Raab, 1969, p. 19) and Turkestan (Reyment, 19'55, p. 62). 

Nigericeras scotti Cobban, n. sp. 

Plate 9, figures 1-4; plate 18, figures1 1-9; text figures 15-17 

The type collection, from USGS Mesozoic locality 

D6756 (fig. 1, loo. 29), consists of 26 specimens suitab~e 

for measurrunent and as many more that are too crushed 

or d1istorted for measurem.ent. All are internal molds, 

and most ha.ve one side partially or eompletely dissolved. 

The innermost whorls are not preserved. Measurements 

of the best speeimens are given in table 3. 

TABLE 3.-Dimensions and tubercle counts of Nigericeras scotti, n. sp., from USGS Mesozoic local£ty D6756 

U.S.N.M. No. 

166397 _______ _ 166398 _______ _ 

166399_-- ·---- 166400 _______ _ 

166401.------- 166402 _______ _ 

166403 _______ _ 

166404_ ------- 166396_-- -----

166405 _______ _ 

166406_ - ------ 166407--------

166408_ - ------ 166409 _______ _ 

166410 _______ _ 

166411.-------

166412_-------

166413_------- 166414 _______ _ 166415 _______ _ 

166416_------- 166517 _______ _ 166518 _______ _ 166519 _______ _ 166520 _______ _ 

Diamete.r 

(mm) 

32.2 

39.6 

49.0 

54.2 

ca .56 

60.7 

75.0 

65.3 

69.0 

69.5 

89.4 

72.5 

75.6 

76.3 

77.4 

78.1 

98.4 

83.0 

83.8 

115.5 

92.3 

93.0 

94.3 

94.5 

95.0 

101.3 

109.0 

112.0 

115.7 

Umbilical 

width (mm) 

6. 7 13.2 

13.8 

15.8 

ca .14 

12.8 

22.4 

20.5 

23.5 

21.4 

28.2 

22.0 

25.8 

24.2 

23.8 

25.0 

35.8 

23.4 

25.9 

38.4 

29.4 

30.5 

32.3 

31.8 

32.7 

35.5 

38.0 

37.3 

39.2 

Umbilical ratio 

Diameter 

at base of body chamber 

(mm) 

Umbilical 

tubercles 

per half whorl 

0. 21 ---------------------------- .33 -------------- 5 .28 -------------- 5 .29 -------------- 6 ca .. 25 ______________ 5 

. 21 -------------- 4 

.30 ---------------------------- .M 63 3 .M ® 6 

. 31 -------------- 6 .32 -------------- 7 .W CLn 5 

.34 -------------- 5 .32 -------------- 4 .M ® 5 .32 -------------- 4 .36 ca. 69 _____________ _ 

.~ H 6 

.31 -------------- 6 .33 ---------------------------- .32 ----------------------------

.33 ---------------------------- .34 -------------- 5 . 34 ca. 70 _ _ ________ _ . ::!4 ca. 62 _________ - __ 

. 35 -------------------------- .35 -------------------------- .33 ca. 74 ___________ _ 

. 34 76 ------------
SYSTEMATIC DESCRIPTIONS 19 

40 I I I I I I I I 

Q 

~ 0:: 

----· --- --------- -· . ----!,-.:.::. ___ -.:;-::::_-::::::• ____ !.·--------------------, ___ .. ---' 30 <t: 

0 · ... ,, .. -• ::J 

Ill 

:;:;;: 

::::J 

20 I I I 

30 40 50 60 70 80 90 100 110 120 

DIAMETER, IN MILLIMETERS 

l!"'IGURE 15.-Scatter diagram showing umbilical ratios of Nigericeras scotti, n. sp., from USGS Mesozoic locality D6756. Dots 

connected by dashes represent measurements on single specimens. 

Umbilical ratios range :from 21 to 36 percent and show 

a gradual increase with growth of the shell up to the 

base of the body chamiber (fig. 15). The ratio then increases a little more rapidly owing to a slight scaphitoid 

development of the adult body chamber (pl. 18, fig. 9). 

Whorl sections are very stout; most are a little higher 

than wide, but some a.re as wide as high (fig. 16). 

Ornamenta.tion consists of rectiradiate ribs and 

l.Ultbilical tubercles, lower and upper. ventrolateral 

tubercles, and siphonaJ tubercles, all of which a,re 1nost 

conspicuous on the phragmocone. The ribs are rather 

widely spaced and consist of primaries and secondaries 

that tend to va.ry in size and strength. The prima.ries 

rise from umbilical tubercles, weaken on crossing the 

..,...------

FIGURE 16.-'Whorl sections, natural size, of the holotype of 

Nigericeras scotti, n. sp., at a diameter of 74 mm. USNM 

166396. 

flank, and become strong again on crossing the venter. 

On the sma.Hest specimen (diameters between 22 and 

33 mm), most adjacent primaries are sepa.rated by two 

seconda,ries. The seconda.ry ribs rise on the middle of the 

flank and on some individuals become 011 the venter as 

strong as the primaries. All ribs weaken on the body 

chamber, and some disappear from the flanks. Each 

primary rib on the phragmocone bears a strong nodate 

lower ventrolateral tubercle, a smaller nodate, bullate, 

or clavate upper ventrol'ateral tubercle, and a still 

smaller clavate siphonal tubercle. 

Most secondary ribs on the p:hragmocone have upper 

ventrola:teral tubercles and siphonal tuiberc:les; some 

seconda,ries rising lower on the flank have, in addition, 

nodate lower ventrol'a,teral tubercles. AH tubercles 

weaken near the end of the adult phragmocone and disappear well down on the 'body chamber. 

The body chamber begins at some dia.meter between 

62 and 76 mm ( talbJe 3). Its cross section is inflated with 

flattened to broadly rounded flanks and well-rounded 

venter. Most specimens show a little straightening of the 

older part of the body cha.mber which imparts to it a 

slight scaphitoid appearance (pl. 18, fig. 9). The aperture seems to be smooth, straight, and not constricted 

(pl. 18, fig. 8). The entire body chamber occupies a little 

more than half a whorl. 

A complete external suture is not preserved on any 

of the specimens. The few bits of visible sutures are 

poorly preserved. Parts of sutures of five individuals are 

sh:own in figure 17. These reveai a rather simple pattern 

with high and narrow first lateral saddle and broad 

deeply bifid lateral lobe. 

The holotype (pl. 9, figs. 1-4; text fig. 16) consists 

of 1nost of an adult; it is 90 mm in diameter and has 

umbilicai ratios of 31 and 32 percent. It is distorted a 
20 AMMONITES, UPPER CRETACEOUS, WESTERN INTERIOR OF THE UNITED STATES 

A 

c 

E 

FIGURE 17.-Parts of external sutures, X 3, of five specimens. of 

Nigericera:s scotti, n. sp. A, S.iphona,l lobe of parntype USNM 

166410 at diameter of 49 mm. B, Second lateral saddle and 

'second lateral lobe of paraty:pe USNIM 166416 at diameter of 

52 mm. 0, Part of lateral lobe, second lateral saddle, und second lateral lobe of paratype USNM 1665?1 at diameter of 

about 44 mm. D, Paratype USNM 166522. E, Lateral lobe of 

paratype USNM 166520 at diameter of 60 mm. 

little but shows the main features of the species. The 

last whorl has a maximum height of 3.S.5 mm and a 

width of 31 mm. 

The species is named for Glen111 R. Scott, of the U.S. 

Geological Survey, who made the original collection. 

N igericeras scotti more closely resembles the acanthoceratid forms of the-genus than the vascoceratid forms. 

It perhaps most closely resembles N. ogojaense Reyment 

( 19·55, p. 62, pl. 13, fig. 6 ; pl. 14, fig. 3; text fig. 28) in 

the persistence of acanthoceratid ornamenta,tion out to 

a l'arge dia.meter and in the deeply bifid lateral lobe, but 

the Nigerian species has the ventrolateral tubercles remaining at greater diameters, as well as occurring in 

pairs. Of the species from the Damergou area in Niger, 

the one most closely resembling N. scotti is N. gignouwi 

Schneegans (1943, p. 119, pl. 5, figs. 10-15; text figs. 1, 

2; Furon, 1935, p. 56, pl. 2, fig. 9 only) which has 

coarsely sculptured inner whorls, but that ornamentation disappears at a smaller diameter, the adult body 

chamber lacks the scaph1toid development, and the first 

lateral saddle is broaJder. Other species from Niger and 

Nigeria., such as N. gadeni ( Chudeau, 1909, p. 71, pl. 3, 

figs. 6a,, b; 1921, p. 468, text figs. 4, 5) and the species 

described by Barber (1957, p. 29-31), have the inner 

whorls more weakly sculptured and more rounded, and 

the sutures more simplified. 

Types.-Holotype USNM 166396; paratypes USNM 

1663·97-166416, 166517-166522, 164057. 

Occurrence.-Nigericeras scotti has been found at only 

one locality in southeastern Cblorado (fig. 1, loc. 29'), 

where it occurs in a 1thin bed of limestone about 12 feet 

above the base of the Bridge Creek Limestone Member 

of the Greenhorn Limestone. It was associated with a 

few poorly preserved inocerams that could represent 

Inoceramus labiatus ( Schlotheim) at the base of the 

Turonian. 

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INDEX 

[Italic page numbers indicate both major references and descriptions] 

A Page 

Acanthoceras _____ _____________________________ 10, 18 

amphibolum_ __ _ _ __ _ _ __ __ ____ __ _ _ __ __ ____ _ 12 

Zone_________________________________ 12 

borgesL ___________________________________ 13,14 

naviculare _____________________________ 13, 14,15 

navicularis__ ___ __ _ __ _ __ __ _ ___ ____ __ __ __ __ _ 15 

[Calycoceras] borgesi_______________________ 16 

(Calycoceras) naviculare ___________________ 13,15 

Acanthoceratidae____ ___ ___ __ ____ __ ___ ___ __ _ _ _ 10 

Acompsoceras. ________________________________ 10, 12 

essendiense madagascariensis___ _ _ _ _ _ _ _ _ _ _ _ _ 12 

acutus americanus. Turrilites__________________ 12 

Algeria _______________________________________ 14, 15 

americanus. Turrilites acutus__________________ 12 

Ammonites bochumensis_ ---------------------- 12 clypealis_ ___ _ _ _ __ __ _ ___ __ ___ _ __ __ _ _ __ __ _ __ 8, 9 

hernensis_ _ _ _ _ _ ____ __ _ _ _ _ __ ___ _ __ __ _ _ _ _ __ _ 8, 9 

latidorsatus__ _ _ __ _ _ __ __ _ _ _____ ___ __ __ _ _ __ _ 5, 6 

mantellL __ _ _ __ _ ___ __ _ _ _ _ __ __ __ __ ___ _ __ ___ 14 

navicularis _____________________________ 13, 14,15 

[Calycoceras] gentonL _______ . __ _ _ _ _ _ _ __ _ __ 15 

(Ammonites) naviculare, Calycoceras___________ 14 

navicular is, Calycoceras. _ _ _ _ _ __ _ _ __ _ __ _ __ _ 13 

amphibolum, Acanthoceras_______________ ______ 12 

Angola_______________________________________ 14 

Anisoceras_ __ _ _ __ ___ ___ ___ ___ _ _ _ _ __ __ _ _ __ ___ __ 1, 4 

plicatile. ____________________________ 1, 4, 7; pl.1 

Anisoceratidae. ___________________________ . __ 4 

Arizona _____ . __ . ______________________________ 1, 5, 7 

ashlandicum, Desmoceras_________________ _____ 10 

Tragodesmoceras__ _ __ _ ___ ____ __ ___ ___ __ _ __ 10 

B 

bassi, Tragodesmoceras .. _ _ _ _ ___ __ _ _ __ __ _ ___ __ _ 1, 9 

bererense, Tragodesmoceras ___________ . _ __ __ _ _ _ 8 

Bergquist, H. R., cited_______________________ 6 

Black Hills ___________________________________ 8,10 

Black Mesa___________________________________ 7 

bochumensis, Ammonites______________________ 12 

Bohemia_____________________________________ 15 

Boquillas Formation ___ ---------------------- 13 borgesi, Acanthoceras ___ _______________________ 13, 14 

Acanthoceras [ Calycoceras]_ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 16 

Metacalycoceras_ _ _ _ _ _ __ __ ___ _ __ _ _ _ _ __ __ _ _ _ 13 

Biidge Creek Limestone Member of the Greenhorn Limestone _________ 4, 5, 7, 15, 18,20 

Burkholder. Robert E., cited_________________ 1 

c 

Calycoceras_ _ __ _ _ _ _ _ _ __ ___ __ _ __ __ _ _ __ _ __ _ __ _ _ _ 1, 13 

grossouvreL _______________________________ 13,15 

naviculare_________________________________ 5, 

7, 13; pls. 1, 10, 11, 12, 13, 14, 15, 16,17 

stoliczkaL_ _ __ ___ __ ___ ___ __ ____ __ ___ _ __ ___ 14 

(Ammonites) naviculare___________________ 14 

navicular is____________________________ 13 

(Metacalycoceras) naviculare_______________ 13 

stoliczkai_______________________ _______ 15 

[ Calycoceras] borgesi, Acanthoceras_ _ _ _ _ _ _ _ _ _ _ _ _ 16 

gentoni, Ammonites_______________________ 15 

(Calycoceras) naviculare, Acanthoceras _________ 13, 15 

cantianum, Mantelliceras_ _ _ __ __ ____ __ __ _ _ __ __ _ 14 

Capraro, Charles C., cited ___________________ _ 

Carlile Shale _________ ._______________________ 8, 10 

carlilense, Tragodesmoceras _____________ 8; pls. 3,4,5 

Cerro de Muleros_____________________________ 12 

421-990 0 - 71 - 5 

page 

Cheloniceras gottscheL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 

ctypeale, Tragodesmoceras __ __________________ _ 

clypealis, Ammonites__________________________ 8, 9 

clypealoides, Desmoceras ·-- _ ___ __ _ __ __ _ ___ __ _ _ _ 8 

Tragodesmoceras_ _ _ __ __ __ __ ___ _ __ __ __ _ _ _ _ _ 8, 9 

Collignoniceras woollgari. _ _ _ _ __ __ ___ __ __ _ ___ __ 10 

Colorado ________________________ 1, 4, 5, 7, 9, 10, 16,20 

Crick, G. C., quoted_________________________ 13 

D 

dentonense, Pseudocalycoceras ________________ 5, 7, 18 

Desmoceras ________ ____________________________ 1, 5, 8 

ashlandicum_ __ __ __ __ _ _ __ _ _ _ _ __ __ _ _ __ __ _ _ _ 10 

clypealoides _______________________ . __ __ _ _ _ 8 

kossmatL ______ -_- ___________ . _ -_________ _ 

latidorsatum_ _ _ _ _ __ _ __ ___ ___ _ _ _ __ __ _ _ __ __ _ 5, 6 

(Moremanoceras) scottL _______________ 5, 6; pl. 2 

Desmoceratidae_ _ ___ __ ___ _ __ __ __ __ ___ ___ ___ _ _ 5 

Dorset, England______________________________ 4 

E 

Eagle Ford Formation________________________ 6 

essendiense madagascariensis, Acompsoceras _. _ _ 12 

F 

Fagesia navicular is _________________________ 13, 14, 15 

Fairport Chalky Shale Member of the Carlile 

Shale _____________________ ._______ 10 

France_______________________________________ 8, 14 

Fukada, Atsuo, quoted_______________________ 13 

G 

gadeni, Nigericeras_ _ _ ___ _ _ _ __ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ 20 

gentoni, Ammonites [Calycoceras]______________ 15 

Geographic distribution_--------------------- 1 Germany _____________________________________ 4, 8, 9 

gibbosum, Worthoceras_ _ __ __ ____ __ __ _ _ __ __ __ __ _ 7 

gignouxi, Nigericeras __________________________ 18,20 

gottschei, Cheloniceras ________________________ . 13 

gracile, Sciponoceras __________________________ 5, 7,18 

Greenhorn Limestone________________________ 9 

grossouvrei, Calycoceras _______________________ 13,15 

Metacalycoceras ____________ . ______________ 13, H 

H 

Hamites plicatilis. _ _ _ __ __ _ _ _ _ __ _ __ _ __ _ _ _ _ __ __ _ 4 

saussureanus_ _ _ _ _ _ __ __ _ _ __ __ _ _ __ __ _ _ __ __ _ 4 

Haploceras_ _ _ _ _ _ __ __ _ _ __ __ _ _ __ _ ___ __ _ _ __ _ _ __ _ !l 

Hauerireras ____ ______________________ . _ __ __ __ _ 9 

hernense, Tragodesmoceras ___ _________ . _ __ _ __ _ _ 8, 9 

hernensis, Ammonites _________________ ._______ 8, 9 

India _________________________________________ 14,15 

Inoceramuslabiatus_ ___ __ _ ___ _ ___ __ _ _ __ __ _ _ __ _ 20 

pictus __ _________________________________ 5, 7, 18 

Introduction _____________________________ .____ 1 

IsraeL_______________________________________ 18 

J Japan _____________ . _______________________ .. _ 14 

K 

Kanabiceras septemuriatum __________________ 5, 7,18 

Kansas __ --------------------------------- 1, 9, 10,16 

koumati. Desmoceras __ _____________________ . __ 5 

L Page 

labiatus, Inoceramus__________________________ 20 

Landis, Edwin R., cited_____________________ 12 

landisi, Paracompsoceras _________ 10; pls. 2, 6, 7. 8, 9 

latidorsatum, Desmoceras_ __ __ _ ___ __ __ __ _ _ _ _ __ _ 5, 6 

latidorsatus, Ammonites ___ .___________________ 5, 6 

Localities, fossiL _____________________________ 1, 3, 4 

M 

Madagascar ______ ------------------------ 4, 8, 14,15 

madagascariensis, Acompsoceras essendiense____ 12 Mancos Shale ______________________________ .__ 7 

second sandstone member________________ 12 

mantelli, Ammonites _________________ . _____ .__ 14 

Mantelliceras __________ . _____ . _ _ _ __ __ _ _ __ __ _ _ _ 14 

cantianum___ ____ __ __ __ __ _ ___ __ _ __ _ __ _ _ _ _ _ 14 

Matsumoto, Tatsuro, quoted_________________ 16 

Metacalycoceras_ _ _ _ __ _ _ __ __ _ _ __ ___ __ _ __ __ _ _ ___ 14 

borgesi___ __ __ __ __ __ __ __ __ __ __ __ _ ___ ___ _ __ _ 13 

grossouvrei_ _____________ . _________________ 13, 14 

naviculare _________ . _________________ ---_- 13 

orbignyL __ ____________________ -___ --- ___ - 14 

(Metacalycoceras) naviculare, Calycoceras_ _ _ _ _ _ 13 

stoliczkai, Calycoceras ________________ ---- _ 15 

Metoicoceras whitei_ __________________________ 5, 7,18 

Model anticline ______________________________ - 4 

Moremanoceras ____ ____ . ____________ ----- _-. --- 5 

(Moremanoceras) scotti, Desmoceras ________ 5, 6; pl. 2 

muelleri, Puzosia ___ ___________________ ------- 8, 9 

Muniericeras __ ___ . _________________ ----------- 9 

Muniericeratidae __________ ------- _ ----------- 8 

N 

naviculare, Acanthoceras. __________________ 13, 14,15 

Acanthoceras (Calycoceras) _____ -----.----- 13, 15 

Calycoceras ___________________ ------------ 5, 

7, 13; pls. 1, 10, 11, 12, 13, 14, 15, 16,17 

(Ammonites)__________________________ 14 

(Metacalycoceras) ______ _____ ----------- 13 

Metacalycoceras ________________ ---. ------- 13 

navicular is, Acanthoceras ___ _____ . ------.------ 15 

Ammonites ____________________________ - 13, 14,15 

Calycoceras (Ammonites) _______ ----------- 13 

Fagesia ________________________________ 13, 14,15 

New Mexico _____________________ ---.-----.--- 1,12 

newberryi, Pycnodonte _____ --- ---------.------- 7 

Niger ________________________ ---_-.----------- 18,20 

Nigeria ____________ . _______________ -----.----- 18,20 

Nigericeras ____ ___________________ -_ --------- 1, 12,18 

gadenL ______________ . _ ------------------- 20 

gignouxL _________________________________ 18,20 

ogojaense ____ ___ --------------------------- 20 

scotti__ _____________________________ 18; pls. 9,18 

Nowakites _________ -- __ ---------- __ -----------

0 

ogojaense, Nigericeras ___ --- -------------------

Onitshoceras _____ ----------------------------- scotti_ ____________________________________ _ 

orbzgnyi, Metacalycoceras.- _-.-- ---------------

Oregon_--------------------------------------

oregonensis, Pachydiscus ____ ------------------

p 

Pachyaiscus _____ ___ --------------.------------

oreoonensill _____ --------.------------------ spA _____________________________________ _ 

23 

8 

20 

5 

6 

14 

10 

10 

5 

10 
24 INDEX 

Page Page Page 

Paracompsoceras___ __ __ _ _ __ __ __ __ ______ ____ __ _ 1,10 scotti, Desmoceras (Moremanoceras) ________ 5, B;pl. 2 Tragodesmocera&-Con tinued 

landisi__ _______________________ 10; pis. 2,6, 7,8, 9 Nigericeras _________________________ 18; pls. 9, 18 hernense. _ __ ___ __ ____ __ _ _ __ __ ___ ___ ___ ___ _ 8, 9 

pictus, Inoceramus ___________________________ 5, 7,18 Onitshoceras. _ ___ __ ____ ___ _ __ __ _ _ _ ___ ___ _ _ 6 scotti. _ _ _ _ _ ___ _ __ ____ __ ___ ___ __ ____ __ _____ 5, 6 

plicatile, Anisoceras ____________________ 1, 4, 7; pl. 1 Tragodesmoceras__ _ __ _ _ _ _ _ _ __ _ _ __ __ ___ _ __ _ 5, 6 sp_ _ _ ___ ___ __ ____ ____ _ _ __ ___ ___ __ __ __ __ ___ 10 

plicatilis, Hamites_____________________________ 4 septemseriatum, Kanabiceras __ ___ ------------ 5, 7,18 Tunisia._____________________________________ 14 

Poland_______________________________________ 4 South Dakota _________________________________ .1, 10 Turkestan____________________________________ 18 

Pool Creek Shale Member of the Carlile Shale._ 10 Spain ____ ·----------------------------------- 14 Turrilites acutus american us__________________ 12 

PortugaL____________________________________ 14 Spath, L. F., quoted ____________ ------------- 13,14 

Powell, J. Dan, cited_________________________ 12 stoliczkai, Calycoceras__ ___ ___ __ _ _ _ _ __ ___ _ __ __ _ 14 u 

Pseudocalycoceras. ___________________________ _ Calycoceras (Metacalycoceras) ___ __________ - 15 United States________________________________ 8 

dentonense ___ ______ ------ ____________ -___ 5, 7,18 Sweden ____ ---------------------_____________ 8 Upper Chalk, Offham. England______________ 13 

Puzosia______ __ ____ __ _ ___ __ __ __ __ _____ _ __ __ __ _ 8 Systematic descriptions _________ ------------- 4 

muelleri___________________________________ 8, 9 v n. sp ____ • _ __ __ __ _ _ __ ____ __ ___ ___ __ _ _ __ __ _ 10 T Vascoceras. _ ___ _ _ _ ___ __ __ _ _ __ __ _ _ _ _ __ __ _ _ __ __ _ 18 

Puzosinae. ______________________________ -- __ _ 8 Texas. ______________________________________ 5, 6,12 Vascoceratidae. _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ __ __ _ _ __ __ _ 18 

Pycnodonte newberryi________________ _________ 7 Touvois, France ______________________________ 14,15 

Tragodesmoceras __ _______________________ -- ___ 1, 5, 8 w 

s ashlandicum __ _______________________ -- __ - 10 whitei, Metoicoceras __________________________ 5, 7,18 

Saito, Rinji, quoted _____________________ -- __ • 13 bassi..____________________________________ 1, 9 woollgari, Collignoniceras_____ _ __ _ _ _ __ __ _ _ __ __ _ 10 

Sarthe, France .• ________________________ --___ 14 bererense____ _ __ ___ _ __ _ _ _ ___ _ _ _ __ _ _ _ __ _ _ __ _ 8 Worthoceras gibbosum _____ ________ --- ___ -_ ----- 7 

saussureanus, Hamites________________________ 4 carlilense ___________________________ 8, pis. 3, 4, 5 Wright, C. W., cited _________________________ 1,5, 14 

Sciponoceras gracile __________________________ .5, 7, 18 clypeale ____ ________________________ -_-- __ _ 9 Wright, E. V., quoted________________________ 14 

Scott, Glenn R., cited________________________ 20 clypealoides. _ __ ___ _ _ _ _ _ _ ___ ___ _ ____ ___ _ __ _ 8, 9 Wyoming _____________________________________ 1,10 
PLATES 1-18 

[Contact photographs of the plates in this report are available, at cost, from U.S. Geological Survey Library, Federal Center, 

Denver, Colorado 80225] 
PLATE 1 

[All figures natural size] 

FIGURES 1-3. Calycoceras naviculare (Mantell) (p. 13). 

Rear, side, and front views of the inner whorls of a specimen from the base of the Bridge Creek Limestone Member 

of the Greenhorn Limestone at USGS loc. 18686 (text fig. 1, loc. 24). See plate 13, figures 4 and 5 for rest of the 

specimen. Hypotype USNM 166362. 

4-7. Anisoceras plicatile (J. Sowerby) (p. 4). 

From the base of the Bridge Creek Limestone Member of the Greenhorn Limestone at USGS loc. 22899 (text fig. 1 

loc. 26). 

4, 5. Rear and side views of a large limb. Hypotype USNM 166338. 

6, 7. Side and rear views of a smaller limb. Hypotype USNM 166337. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 1 

1 

4 5 7 

CALYCOCERAS NAVICULARE AND ANISOCERAS PLICATILE 
PLATE 2 

[All figures natural size] 

FIGURES 1-23. Desmoceras (Moremanoceras) scotti (Moreman) (p. 6). 

1-4. Front, side, rear, and bottom views of a small specimen showing constrictions. From the Eagle Ford Formation at USGS Joe . 19716, 2 miles northeast of Bells, Tex. Hypotype USNM 166340. 

5, 6. Rear and side views of a slightly larger specimen from the same locality. Hypotype USNM 166341. 

7, 8. Upper rear and side views of a larger specimen from the same locality showing a thickened rib on one side 

of a constriction. Hypotype USNM 166342. 

9, 10. Side and rear views of a similar-sized specimen from t he same locality showing several ribs. Hypotype USNM 

166343. 

11- 14. Front, side, rear, and top views of a stout specimen from the same locality showing fine ribbing. Hypotype 

USNM 166344. 

15-17. Front, side, and rear views of a specimen from the same locality showing two orders of ribbing. Hypotype 

USNM 166345. 

18, 19. Side and rear views of a specimen from the base of the Mancos Shale at USGS loc. D7092 (text fig. 1, 

loc. 31). Hypotype USNM 166347. 

20, 21. Rear and side views of the largest specimen from the same locality as figures 1-4. Hypotype USNM 166346. 

22, 23. Front and side views of a large specimen from the base of the Bridge Creek Limestone Member of the 

Greenhorn Limestone at USGS loc. 22899 (text fig. 1, loc. 26). Hypotype USNM 166348. 

24-26. Paracompsoceras landisi Cobban, n. sp. (p. 10). 

Side, rear, and bottom views of the inner whorls of a paratype from USGS loc. D6130 (text fig. 1, loc. 34). USNM 

166359. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 2 

2 3 4 

5 6 

7 8 9 10 

11 12 13 14 15 16 17 

18 19 

20 21 

22 

23 24 25 26 

DESMOCERAS (MOREMANOCERAS) SCOTTI AND PARACOMPSOCERAS LANDIS! 
PLATE 3 

(Both figures natural si ze] 

FIGURES 1, 2. Tragodesmoceras carlilense Cobban, n. sp. (p. 8). 

Rear and side views of t he holotype from the lower part of the Carlile Shale 

at USGS loc. 21792 (text fig. 1, loc. 4). See plate 5, figure 5 for front view. 

USNM 166349. 
GEOLOGICAL SURVEY 

' 

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~~ .... y . "- ... , ~. 

PROFESSIONAL PAPER 699 PLATE 3 

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TRAGODESMOCERAS CARLILENSE 
PLATE 4 

[All figures natural size] 

FIGURES 1-16. Tragodesmoceras carlilense Cobban, n. sp. (p. 8). 

From limestone concretions in the lower part of the Carlile Shale at localities along the flanks of the Black Hills. 

1,2. Side and front views of a very small specimen from USGS loc . D3754 (text fig. 1, loc. 9). Paratype USNM 

166350. 

3-5. Front, side, and rear views of a juvenile from USGS loc. D411 (text fig. 1, loc. 2). Paratype USNM 166351. 

6-8. Front, side, and rear views of a juvenile from USGS Joe . D1450 (text fig. 1, loc . 12). Paratype USNM 166352. 

9, 10. Rear and side views of a larger juvenile from USGS Joe. 11190 (text fig. 1, Joe . 5). Paratype USNM 166353. 

11-13. Front, side, and rear views of a specimen from USGS Joe. 21792 (text fig. 1, Joe. 4) . Paratype USNM 

166354. 

14-16. Front, side, and rear views of the phragmocone of an adult from the same locality as figures 11-13. Paratype 

USNM 166355. 
GEOLOGICAL SURVEY 

1 

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_., l 

:) 3 

2 

9 10 

14 

4 

PROFESSIONAL PAPER 699 PLATE 4 

5 

6 

11 

15 

TRAGODESMOCERAS CARLILENSE 

12 

7 8 

13 

16 
PLATE 5 

[All figures natural size] 

FIGUREs 1-5. Tragodesmoceras carlilense Cobban, n. sp. (p. 8). 

From limestone concretions in the lower part of the Carlile Shale at localities along the flanks of the Black Hills. 

1, 2. Side and front views of a slender specimen from USGS loc. 12642 (text fig. 1, loc. 14). Paratype USNM 166356. 

3, 4. Front and side views of a septate specimen from USGS loc. 11192 (text fig. 1, loc. 7). The suture is shown in 

text figure 8. Paratype USNM 166357. 

5. Front view of the holotype from USGS loc. 21792 (text fig. 1, loc. 4). An impression of Collignoniceras woollgari 

(Mantell) is visible in the matrix that fills the body chamber. Rear and side views are shown in plate 3. USNM 

166349. 
GEOLOGICAL SURVEY 

~~ ,.,. 

r'-f.... :2~ p 

3 

PROFESSIONAL PAPER 699 PLATE 5 

2 

4 

TRAGODESMOCERAS CARLILENSE 

5 
PLATE 6 

[Figure seven-eighths natural size] 

Paracompsoceras landisi Cobban, n. gen. and n. sp. (p. 10). 

Side view of the holotype from USGS Joe. D6130 (text fig. 1, Joe . 34). USNM 1663.58. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 6 

PARACOMPSOCERAS LANDIS! 
PLATE 7 

[Figure eight-tenths natural size] 

Paracompsoceras landisi Cobban, n. gen . and n. sp. (p. 10). 

Side view of a large stout paratype from USGS loc . D7084 (text fig. 1, loc. 3.5). See text 

figure llB for whorl section. USNM 166360. 
GEOLOGICAL SURVEY 

(; 

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. ~·).,. 

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PARACOMPSOCERAS LANDIS! 

PROFESSIONAL PAPER 699 PLATE 7 
PLATE 8 

[Figure eight-tenths natural size] 

Paracompsoceras landisi Cobban, n. gen. and n. sp. (p. 10) . 

Side view of a slender paratype from USGS Joe. D7084 (text fig. 1, Joe. 35). See text 

figure llA for whorl section. USNM 166361. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 8 

\ 

PARACOMPSOCERAS LANDIS/ 
PLATE 9 

[All ligures natural size] 

FIGURES 1-4. Nigericeras scotti Cobban, n. sp. 18). 

Rear, side, front, and top views of the holotype from near the base of the Bridge Creek Limestone Member of the 

Greenhorn Limestone at USGS loc . D6756 (text fig. 1, loc. 29). USNM 166396. 

5-8. Paracompsoceras landisi Cobban, n. gen. and n . sp. (p. 10). 

Rear and side views of the inner whorls of the holotype from USGS loc . D6130 (text fig. 1, loc . 34). See plate 6 

for the adult shell. USNM 166358. 
GEOLOGICAL SURVEY 

1 

5 

6 

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7 

PROFESSIONAL PAPER 699 PLATE 9 

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4 

3 

8 

NJGERICERAS SCOTTI AND PARACOMPSOCERAS LANDIS! 
PLATE 10 

[All figures natural size] 

FIGURES 1- 8. Calycoceras naviculare (Mantell) (p. 13). 

From the basal bed of the Bridge Creek Limestone Member of the Greenhorn Limestone on the Model anticline 

in southeast Colorado. 

1, 2. Front and side views of the smallest specimen studied, a distorted internal mold from USGS Joe. 18683 (text 

fig. 1, Joe . 21). Hypotype USNM 166392. 

3, 5. Rear and side views of a fragment of a stout specimen that has depressed whorls from USGS loc. 22899 (text 

fig. 1, Joe. 26). See text figure 13G for whorl section. Hypotype USNM 166380. 

4, 7. Rear and side views of a specimen from USGS loc. 18686 (text fig. 1, Joe . 24) that developed a ventrolateral 

angularity on the ribs at an unusually small diameter. Hypotype USNM 166368. 

6. Side view of a specimen from USGS loc. 22899 (text fig. 1, loc. 26). The lateral lobe is shown in text figure 14 

and the whorl section in text figure 13F. Hypotype USNM 166372. 

8. Side view of a moderate-sized specimen from the same locality as that of figure 6. See plate 11, figures 4 and 5 

for other views and text figure 13D for the whorl section. Hypotype USNM 166373. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 10 

2 

5 

4 

7 8 

CALYCOCERAS NAVICULARE 
PLATE 11 

[All figures natural size] 

FIGURES 1-5. Calycoceras naviculare (Mantell) (p. 13). 

From the basal bed of the Bridge Creek Limestone Member of the Greenhorn Limestone on the Model anticline 

in southeast Colorado . 

1-3. Rear, side, and front views of a small specimen from USGS loc. 18686 (text fig. 1, loc. 24). Hypotype USNM 

166363. 

4, .5. Front and rear view:; of a larger specimen from USGS loc. 22899 (text fig. 1, loc. 26) showing a faint ventrolateral angularity. See plate 10, figure 8 for the side view and text figure 13D for the whorl section. Hypotype 

USNM 166373. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE I I 

1 

2 3 

4 5 

CALYCOCERAS NAVICULARE 
PLATE 12 

[Both figures natural size] 

FIGURES 1, 2. Calycoceras naviculare (Mantell) (p. 13). 

Side and front views of a specimen from the basal bed of the Bridge Creek 

Limestone Member of the Greenhorn Limestone at USGS Joe. 18686 

(text fig. 1, Joe. 24). Hypotype USNM 166364. 
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PLATE 13 

[All figures natural size] 

FIGURES 1-5. Calycoceras naviculare (Mantell) (p. 13). 

From the basal bed of the Bridge Creek Limestone Member of the Greenhorn Limestone at localities on the Model 

anticline in southeast Colorado. 

1-3. Front, side, and rear views of an unusually slender specimen from USGS Joe. 22899 (text fig. 1, loc. 26). See 

text figure 13C for the whorl section. Hypotype USNM 166378 

4, 5. Side and rear views of a very stout specimen from USGS Joe. 18686 (text fig. 1, Joe. 24). Sec plate 1. figures 

1-3 for views of the inner whorls. Hypotype USNM 166362. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 13 

J.' J . 

3 

1 

2 

4 5 

CALYCOCERAS NAVICULARE 
PLATE 14 

[All figures natural size] 

FIGURES 1- 3. Calycoceras naviculare (Mantell) (p. 13) . 

Front, side, and rear views of a moderately slender specimen from the 

basal bed of the Bridge Creek Limestone Member of the Greenhorn 

Limestone at USGS Joe . 22899 (text fig. 1, Joe. 26). Hypo type USNM. 

166375. 
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PLATE 15 

[Both figures natural size] 

FIGURES 1, 2. Calycoceras naviculare (Mantell) (p. 13). 

Side and rear views of a sparsely ribbed slender specimen from the basal 

bed of the Bridge Creek Limestone Member of the Greenhorn Limestone 

at USGS Joe. 18686 (text fig. 1, Joe. 24). See text figure 13A for the whorl 

section. Hypotype USNM 166367. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 15 

1 2 

CALYCOCERAS NAVICULARE 
PLATE 16 

(Both figures natural size] 

FIGURES 1, 2. Calycoceras naviculare (Mantell) (p. 13). 

Rear and side views of a specimen from the basal bed of the Bridge Creek 

Limestone Member of the Greenhorn Limestone at USGS Joe. 18686 

(text fig. 1, Joe. 24) showing a slight ventrolateral angularity. Hypotype 

USNM 166365. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 16 

,- # 

. - .....----

--· ---- ---- \ , 

1 2 

CALYCOCERAS NAVICULARE 
PLATE 17 

[Figure natural size] 

Calycoceras naviculare (Mantell) (p. 13). 

Side view of a large specimen from the basal bed of the Bridge Creek Limestone Member 

of the Greenhorn Limestone at USGS loc. 18686 (text fig. 1, loc. 24). See text figure 

13H for the whorl section. Hypotype USNM 166366. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 699 PLATE 17 

\ 

CALYCOCERAS NA VJCULARE