The Ammonite Metengonoceras Hyatt, l903, from the 

Mowry Shale (Cretaceous) of Montana and Wyoming 

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Chapter L 

The Ammonite Metengonoceras Hyatt,· 1903, from the 

Mowry Shale (Cretaceous) of Montana and Wyoming 

By WILLIAM A. COBBAN and W.J. KENNEDY 

A multidisciplinary approach to research studies of 

sedimentary rocks and their constituents and 

the evolution of sedimentary basins, both ancient and modern 

U.S. GEOLOGICAL SURVEY BULLETIN 1787 

EVOLUTION OF SEDIMENTARY BASINS-UINTA AND PICEANCE BASINS 
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1989 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

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Box 25425 

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Library of Congress Cataloging-in-Publication Data 

Cobban, William Aubrey, 1916-

The ammonite Metengonoceras Hyatt, 1903, from the Mowry Shale 

(Cretaceous) of Montana and Wyoming I by William A. Cobban and W.J. 

Kennedy. 

p. em. - (Evolution of sedimentary basins-Uinta and Piceance 

basins) (U.S. Geological Survey bulletin ; 1787-L) 

"A multidisciplinary approach to research studies of sedimentary rocks and 

their constituents and the evolution of sedimentary basins, both ancient and 

modern." 

Includes bibliographical references. 

1. Metengonoceras-Montana. 2. Metengonoceras-Wyoming. 

3. Paleontology-Cretaceous. 4. Paleontology-Montana. 5. PaleontologyWyoming. I. Kennedy, W. J. (William James) II. Title. Ill. Series. IV. Series: 

U.S. Geological Survey bulletin ; 1787-L 

QE75.B9 no. 1787-L 

[QE807.A5] 

557.3 s-dc20 89-600211 

[564'.53] CIP 
CONTENTS 

Abstract Ll 

Introduction Ll 

Localities of collections L2 

Systematic paleontology L2 

Family Engonoceratidae Hyatt, 1900 L2 

Genus Metengonoceras Hyatt, 1903 L2 

Metengonoceras aspenanum (Reeside and Weymouth) L2 

Metengonoceras teigenense, n. sp. L6 

Origin and age of the Mowry Metengonoceras L 7 

References cited LlO 

PLATES 

[Plates follow references cited] 

1-5. Metengonoceras 

FIGURES 

1. Map of part of Western Interior of United States showing localities of collections of Metengonoceras LJ 

2. Histogram showing range in size of base of body chambers of 

Metengonoceras aspenanum (Reeside and Weymouth) L4 

3. Drawing of external sutures of Metengonoceras aspenanum (Reeside and 

Weymouth) LS 

4. Histogram showing range in size of base of body chambers of 

Metengonoceras teigenense, n. sp. L 7 

5. Drawing of external sutures of Metengonoceras teigenense, n. sp. L8 

TABLE 

1. Localities at which Metengonoceras aspenanum (Reeside and Weymouth) and 

M. teigenense, n. sp., were collected L4 

Contents Ill 
IV Contents 

CONVERSION FACTORS FOR SOME Sl METRIC AND U.S. UNITS OF MEASURE 

To convert from 

Feet (ft) 

Miles (mi) 

Pounds (lb) 

Degrees Fahrenheit ("F) 

To 

Meters (m) 

Kilometers (km) 

Kilograms (kg) 

Degrees Celsius ( OC) 

0.3048 

1.609 

0.4536 

Multiply by 

Temp OC=(temp "F-32)/1.8 
EVOLUTION OF SEDIMENTARY BASINS-UINTA AND PICEANCE BASINS 

The Ammonite Metengonoceras Hyatt, 1903, from the 

Mowry Shale (Cretaceous) of Montana and Wyoming 

By William A. Cobban and W.j. Kennedy 

Abstract 

Pseudoceratitic ammonites of the family Engonoceratidae 

are locally common in the Mowry Shale in the central and 

northern parts of the Western Interior of the United States. Most 

occurrences are of crushed, specifically indeterminate specimens, but occasional collections from concretions have wellpreserved, uncrushed material. Metengonoceras aspenanum 

(Reesi':le and Weymouth) is revised on the basis of uncrushed 

speci;.1ens from a concretion in the Neogastroplites americanus 

zone in the Colorado Shale of Wheatland County, Montana. 

Metengonoceras teigenense, n. sp., is described from abundant 

material from a concretion in the Neogastroplites muelleri zone 

!n the Mowry Member of the Colorado Shale of Petroleum 

County, Montana. Metengonoceras aspenanum seems to be 

older than M. teigenense, n. sp., and both species are believed 

to be of early Cenomanian age. 

INTRODUCTION 

The Engonoceratidae is a Tethyan family that has 

abundant representatives in the upper Albian-lower 

Cenomanian Washita Group of Texas. Specimens are 

characterized by a compressed, highly involute shell with 

a very narrow venter that is flat at some growth stage. 

The unusual suture line has numerous auxiliary and 

adventive elements in which the saddles are usually entire and the lobes are subdivided in such a manner as to 

resemble the Triassic Ceratitidae; hence, the term pseudoceratite has been applied to them. 

Engonoceratids have a typically Tethyan distribution, and, therefore, their occurrence in large numbers 

as far north as Montana is in itself remarkable. During 

the Albian, engonoceratids were present in a broad belt 

from Iran through the Middle East and North Africa to 

Ecuador, Colombia, Peru, Venezuela, Mexico, and Texas 

(Basse, 1940; Kennedy and Cobban, 1976, fig. 13). In 

Manuscript approved for publication June 7, 1989. 

Europe, there are scattered records from the Iberian 

Peninsula, France as far north as Aube (Amedro and 

Destombes, 1984), and southern England (Spath, 1924, 

1931; Kennedy and Hancock, 1978). There is a single exotic Southern Hemisphere record from northern Australia 

(Wright, .1963). Aside from Neolobites, localities of 

engonoceratids from Cenomanian and Turonian rocks 

are much fewer, but there are records from France 

(Grossouvre, 1912; Kennedy and others, 1981), Tunisia 

(Pervinquiere, 1907), and Nigeria (Furon, 1935; 

Schneegans, 1943; Barber, 1957; Zaborski, 1987), as well 

as numerous records from Texas (for example, Adkins, 

1928). 

Engonoceratids have been known from the Aspen 

and Mowry Shales of the Western Interior region for the 

past 57 years, but only one paper dealt with their systematics when Reeside and Weymouth (1931) described 

Epengonoceras [Metengonoceras] aspenanum from the 

Aspen Shale of southwestern Wyoming. The specimens 

occurred flattened in hard, siliceous shale. Later, uncrushed engonoceratids were found in concretions in the 

Mowry Shale at several localities in Wyoming and Montana. These specimens were assigned to Metengonoceras, 

but none was described (Reeside and Cobban, 1960). The 

engonoceratids and the associated Neogastroplites were 

considered as latest Albian in age with the reservation that 

they could be of early Cenomanian age. 

The present investigation was undertaken to 

describe the species of Metengonoceras of the Mowry 

Shale and to relate them to the engonoceratid sequence 

of the Gulf coastal region with the object of more closely dating the Mowry. 

In the course of the present study, only two species 

of Metengonoceras were recognized-M. aspenanum 

(Reeside and Weymouth) and M. teigenense, n. sp. Both 

are well represented by uncrushed material from a few 

silty concretions. 

The erratic occurrences of Metengonoceras in the 

Western Interior present a problem. Aside from the local 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming L 1 
abundance of specimens in two zones of the Mowry 

Shale, occurrences of Metengonoceras are scarce. A single 

flattened specimen (Metengonoceras sp.) was found in 

the lower part of the Mancos Shale southeast of Socorro, 

N.Mex., at USGS Mesozoic locality D5777 in the SE1/4 

sec. 8, T. 5 S., R. 2 E., Socorro County. This specimen 

was found a little above beds that contain an Acanthoceras amphibolum fauna, and the age of the specimen 

is probably middle Cenomanian. A large, poorly preserved, flattened specimen, identified as Epengonoceras 

dumbli (Cragin)? by Cobban and Scott (1973, p. 59, pl. 

8), was collected 3.3 m above the middle Cenomanian 

Thatcher Limestone Member of the Graneros Shale near 

Pueblo, Colo. Sutures are not preserved, and it is possible that this specimen could even be a crushed nautiloid. 

Metengonoceras acutum Hyatt occurs along the east side 

of the ·Western Interior seaway in . northwestern Iowa 

(Cobban, 1983, 1987). Associated fossils include Dunveganoceras pondi Haas of earliest late Cenomanian age. 

Metengonoceras acutum also occurs a little higher in the 

late Cenomanian zone of Metoicoceras mosbyense in 

~orth-central Minnesota (Cobban, 1987). No trace of 

Metengonoceras has been found in these zones in the central and western parts of the seaway. Younger rocks of 

late Cenomanian age in the Western Interior have not 

yielded any specimens of this genus, although M. acutum 

is known from rocks as young as the zone of Sciponoceras 

gracile in north Texas. 

All specimens described in this report have USNM 

catalog numbers and are kept in the U.S. National 

Museum (USNM) of Natural History, Washington, D.C. 

(formerly U.S. National Museum). Plaster casts of a few 

of the specimens are in the reference collection of the U.S. 

Geological Survey at the Federal Center in Denver, Colo. 

R.E. Burkholder made the photographs. Kennedy 

acknowledges the financial support of the Natural Environment Research Council (U.K.), the Royal Society, 

and the Astor Fund (Oxford), and the technical assistance 

of the staff of the Geological Collection, Oxford University Museum, and the Department of Earth Sciences, Oxford (U.K.). 

LOCALITIES OF COLLECTIONS 

Localities at which Metengonoceras aspenanum 

(Reeside and Weymouth) and M. teigenense, n. sp., have 

been collected in the northern part of the Western Interior 

are shown in figure 1. The U.S. Geological Survey 

(USGS) Mesozoic locality number, names of collectors, 

year of collection, locality, and stratigraphic assignment 

are given in table 1. 

L2 Evolution of Sedimentary Basins-Uinta and Piceance Basins 

SYSTEMATIC PALEONTOLOGY 

Family ENGONOCERATIDAE Hyatt, 1900 

Genus METENGONOCERAS Hyatt, 1903 

Type species.-Metengonoceras inscriptum Hyatt, 

1903, p. 180, pl. 25, figs. 5-9; pl. 26, figs. 1-4, by subsequent designation, Roman, 1938, p. 491, from the middle Albian Fredericksburg Group, Wise County, Tex. 

Diagnosis.-The following concise diagnosis was 

given by Cobban (1987, p. C2). ''This genus includes very 

compressed, almost smooth ammonites that have tiny 

umbilici and narrow, flattened venters, which may round 

on the adult body chamber. Ornament consists of falcoid 

growth lines and, on some specimens, weak arcuate ribs 

a little above the middle of the flank and rarely faint umbilical bullae. Sutures are very closely spaced and have 

numerous auxiliary and adventive elements with most 

saddles undivided and the larger lobes moderately 

frilled.'' 

Hyatt (1903, p. 179) noted that internal molds may 

have an acute venter in the early adult growth stage. 

Metengonoceras aspenanum (Reeslde and Weymouth) 

(Plate 1, text figure 3) 

1931. Epengonoceras aspenanum Reeside and' 

Weymouth, p. 16, pl. 1, fig. 15; pl. 2, figs. 2-5; pl. 

3, figs. 5-7. 

1951. Metengonoceras aspenanum (Reeside and 

Weymouth). Cobban and Reeside, p. 1893. 

1960. Metengonoceras A. Reeside and Cobban, p. 26. 

Types.-Holotype USNM 73774; hypotypes 

USNM 420357-420369. 

Diagnosis.-A very involute species that has a flat 

venter on the inner whorls with a midventral threadlike 

ridge. Ornament consists of falcoid growth lines accentuated a little near the middle of the flank on the outer 

whorl. 

Description.-Reeside and Weymouth's types consist of eight flattened, somewhat distorted internal molds 

from the Aspen Shale of southwestern Wyoming. The 

holotype (USNM 73774), about 73 mm in diameter, has 

an umbilical ratio of 0.07. A flat venter is present at least 

to a diameter of 70 mm. Falcoid growth lines are the only 

ornament. The external suture has many narrow lobes 

separated by broader saddles of which the first four are 

bifid, the next three are undivided, and the next two are 

very wide and bifid (Reeside and Weymouth, 1931, pl. 

2, figs. 4, 5). 

Undistorted specimens that seem referable to 

Metengonoceras aspenanum have been found in a few 
0 Shelby 

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46° 

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-------------------------l __ _ 

100 200 KILOMETERS 

Figure 1. Part of the Western Interior of the United States showing localities of collections of Metengonoceras 

teigenense n. sp. (X) and M. aspenanum (Reeside and Weymouth) (solid circle) referred to in the text and 

in table 1. Base map from Reeside and Cobban (1960, fig. 1 ). 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming L3 
Table 1. Localities at which Metengonoceras aspcnanum (Recside and Weymouth) and M. teigenense, n. sp., were collected 

[Localities shown by number on figure 1; USGS numbers are Mesozoic locality numbers] 

Locality USGS 

number number 

24705 

2 24601 

3 26224 

4 24065 

5 24418 

6 D9004 

7 23042 

8 24608 

9 17934 

10 10415 

11 23465 

12 24565 

13 24554 

14 24567 

15 24568 

16 24561 

17 24564 

18 8535 

19 6735 

20 14718 

Collector, year of collection, description, and stratigraphic assignment 

W.A. Cobban, 1953. South side of Belt Butte in the NW1/4SE1/4 sec. 30, T. 19 N., R. 7 E., Cascade County, 

Mont. Mowry Member, 12m above top of Arrow Creek Member of the Colorado Shale. 

W.A. Cobban, 1953. SW1/4SW1/4 sec. 7, T. 16 N., R. 21 E., Fergus County, Mont. From 23m above base of 

Mowry Member. 

0.0. Mueller, 1956. Due north of Ayers Colony, sec. 15 or 16, T. 15 N., R. 22 E., Fergus County, Mont. From 23 

m above base of Mowry Member. 

0.0. Mueller, 1952. About 4 km southeast of Teigen, center sec. 4, T. 14 N., R. 25 E., Petroleum County, Mont. 

From a large concretion just below middle of Mowry Member. 

0.0. Mueller, 1952. Near center of sec. 3, T. 14 N., R. 25 E., Petroleum County, Mont. From a concretion just 

below middle of Mowry Member. 

E.A. Merewether and W.A. Cobban, 1973. NW1/4NW1/4 sec. 14, T. 7 N., R. 8 E., Meagher County, Mont. From 

concretion in Mowry Member. 

J.B. Reeside, Jr., and others, 1950. Timber Coulee in center SW1/4 sec. 14, T. 7 N., R. 16 E., Wheatland County, 

Mont. From unnamed shaly member 35 m below base of Big Elk Sandstone Member of Colorado Shale. 

0.0. Mueller, 1953. Timber Coulee in N1/2NE1/4 sec. 23, T. 7 N., R. 16 E., Wheatland County, Mont. Same 

stratigraphic position as 23042. 

R.P. Bryson, 1938. NE1/4SE1/4 sec. 34, T. 58 N., R. 103 W., Park County, Wyo. Mowry Shale. 

A.J. Collier, 1920. Raihoad cut in sec. 3, T. 48 N., R. 66 W., Crook County, Wyo. Mowry Shale. 

W.A. Cobban, 1951. Bank of Belle Fourche River in NE1/4 sec. 28, T. 57 N., R. 62 W., Crook County, Wyo. 

About 18 m below top of Mowry Shale. 

A. Calderon Garda and D.W. Taylor, 1953. NE1/4 sec. 3, T. 53 N., R. 102 W., Park County, Wyo. About 60 m 

above base of Mowry Shale. 

J.B. Reeside, Jr., and others, 1953. NE1/4 sec. 26, T. 53 N., R. 102 W., Park County, Wyo. About 62 m above 

base of Mowry Shale. 

J.B. Reeside, Jr., and others, 1953. SW1/4 sec. 17, T. 52 N., R. 101 W., Park County, Wyo. About 72 m below 

top of Mowry Shale. 

D.W. Taylor, 1953. West oflocality 24567. About 72 m below top of Mowry Shale. 

J.B. Reeside, Jr., and others, 1953. SW1/4 sec. 18, T. 52 N., R. 102 W., Park County, Wyo. About 56 m above 

base of Mowry Shale. 

J.B. Reeside, Jr., and others, 1953. NE1/4 sec. 19, T. 52 N., R. 102 W., Park County, Wyo. About 62 m above 

base of Mowry Shale. 

D.F. Hewett, 1913. Hamilton dome in NE1/4SW1/4NE1/4 sec. 14, T. 44 N., R. 98 W., Hot Springs County, Wyo. 

Near middle of Mowry Shale. 

William Mulholland, 1910. Salt Canyon in SE1/4NW1/4 sec. 5, T. 40 N., R. 81 W., Natrona County, Wyo. 

Middle part of Mowry Shale. 

A.A. Weymouth, 1929. About 4.8 km southeast of Kemmerer in NW1/4NW1/4 sec. 32, T. 21 N., R. 115 W., 

Lincoln County, Wyo. Upper part of Aspen Shale. 

highly fossiliferous limestone concretions in Montana and 

Wyoming. The largest collection is from a concretion at 

USGS Mesozoic locality 23042 near Winnecook in central Montana, where 230 specimens of M. aspenanum 

were found with 1,300 specimens of Neogastrop/ites 

american us (Reeside and Weymouth) (Reeside and Cobban, 1954). Diameters at the base of body chambers could 

be determined for 50 of the M. aspenanum from this 

locality. These measurements revealed a considerable 

span with most between 15 and 70 mm (fig. 2). Crowded 

sutures at the end of body chambers were observed on 

only a few of the larger specimens, and it has not proved 

possible to demonstrate dimorphism. 

10 20 30 40 50 60 70 80 90 

DIAMETER, IN MILLIMETERS 

Figure 2. Histogram showing range in size of base of body 

chambers of 50 specimens of Metengonoceras aspenanum 

(Reeside and Weymouth) from USGS Mesozoic locality 23042 

near Winnecook, Mont. (fig. 1). 

The earliest whorls of specimens from locality 

23042 are about as broad as high and have rounded flanks 

that grade evenly into the rounded venter. At some 

diameter between 2.0 and 2.5 mm, the whorls become 

higher than wide and the venter flattens. At slightly larger 

L4 Evolution of Sedimentary Basins-Uinta and Piceance Basins 

diameters, the whorls become very compressed and the 

flanks flatten; the greatest width is at the umbilical 

shoulder. On internal molds, the venter is either flat or 

slightly concave. On specimens that retain their shell 
material, a threadlike midventral rib arises at some 

diameter between 30 and 40 mm. This rib and flattened 

venter persist on the larger specimens. The largest 

specimen from locality 23042 is an adult about 94 mm 

in diameter that has traces of the mid ventral rib and flattening on the rounded, younger end of the body chamber 

(pl. 1, figs. 20, 21). Other ornament on the specimens 

from locality 23042 consists of falcoid growth lines and, 

5mm 

A 

) 

5mm 

B 

c 

on the body chamber and last septate whorl, faint 

to distinct arcuate ribs on the inner part of the outer 

half of the flank. These ribs, which usually number 

7 or 8 per half whorl, form where the growth lines curve 

back. 

Sutures of the specimens from locality 23042 differ from the two illustrated by Reeside and Weymouth 

(1931, pl. 2, figs. 4, 5) in that the lobes tend to be longer 

Figure 3. External sutures of Metengonoceras aspenanum (Reeside and Wtymouth) from USGS Mesozoic locality 23042 near Winnecook, Mont. (fig. 1). A, Hypotype USNM 420358 at a whorl height 

of 18 mm (pl. 5, figs. 3, 4). 8, Hypotype USNM 420368 at a whorl height of 37 mm. C, Hypotype 

USNM 420369 at a whorl height of 30 mm. Heavy straight line marks the middle of the venter; 

curved dashed line marks the umbilical shoulder; solid curved line marks the umbilical seam. 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming LS 
and the saddles broader (fig. 3). Only one specimen (pl. 

1, figs. 22, 23) has bifid saddles on the outer part of the 

flank like those shown by Reeside and Weymouth. 

Discussion.-Inner whorls of M. aspenanum closely resemble those of the species described by Bose (1928, 

p. 229, pl. 7, figs. 37-41; pl. 8, figs. 1-8; pl. 12, fig. 8) 

as Engonoceras bravoense from the lower Cenomanian 

Del Rio Clay of north-central Texas. Inner whorls of both 

forms are slender with narrow venters and smooth flanks. 

Metengonoceras aspenanum differs chiefly in that it has 

a slightly smaller umbilicus and a slightly broader venter. 

The form described from the Cenomanian of Tunisia as 

Engonoceras thomasi by Pervinquiere (1907, p. 202, pl. 

9, fig. 6a, b; text fig. 77) also resembles M. aspenanum 

in its smooth shell, but the African species has a slightly 

wider umbilicus and a broader venter. Sutures of E. 

thomasi, E. bravoense, and M. aspenanum are much 

alike. All these species should probably be placed in the 

same genus-Metengonoceras. 

Occurrence.-Reeside and Weymouth's types are 

from 24.4 m below the top of the Aspen Shale at USGS 

Mesozoic locality 14718 in the NW1/4 sec. 32, T. 21 N., 

R. 115 W., Lincoln County, Wyo. (fig. 1), where they 

were associated with Neogastroplites americanus (Reeside 

and Weymouth). The specimens of Metengonoceras 

aspenanum described herein are from the same zone (N. 

americanus zone) 35 m below the base of the Big Elk 

Sandstone Member of the Colorado Shale at USGS 

Mesozoic locality 23042 in the SW1/4 sec. 14, T. 7 N., 

R. 16 E., Wheatland County, Mont. (fig. 1). Other occurrences in Montana and Wyoming are shown in figure 

1 and described in table 1. 

Metengonoceras teigenense, n. sp. 

Plates 2-5, text figure 4 

1960. Metengonoceras B. Reeside and Cobban, p. 26. 

Types.-Holotype USNM 420341, figured paratypes USNM 420342-420356, 33 unfigured paratypes 

USNM 420357, all from the Mowry Shale Member of the 

Colorado Shale at USGS Mesozoic locality 24065 in the 

center of sec. 4, T. 14 N., R. 25 E., Petroleum County, 

Mont., where they were associated with Neogastroplites 

muelleri Reeside and Cobban. 

Origin ofname.-From Teigen, Petroleum County, Mont., near which the types were found. 

Diagnosis.-A highly, involute, compressed species 

that has on internal molds a very narrow, flat to concave venter on the early whorls of the phragmocone and 

a sharp venter on the later whorls of the phragmocone 

and body chamber. The suture usually has undivided saddles and florid lobes between the external and lateral 

lobes. 

Description.-The holotype (pl. 2, figs. 5-7) is an 

internal mold of an adult 142 mm in diameter that has 

L6 Evolution of Sedimentary Basins-Uinta and Piceance Basins 

an umbilical diameter of 9.9 mm (0.07). The crushed body 

chamber occupies half a whorl and has a diameter of 103 

mm at its base. A sharp venter is present on the entire 

body chamber as well as on the phragmocone. The uncrushed phragmocone has a very compressed whorl section that is widest at the umbilical shoulder. Ornament 

other than falcoid growth lines seems to be lacking on 

the body chamber. A few faint, short, arcuate ribs are 

visible in oblique lighting on the outer part of the flank 

on the last quarter whorl of the phragmocone. Septa are 

closely spaced as in other species of Metengonoceras. The 

lateral lobe and the first four auxiliary lobes hetween it 

and the venter are florid, and the intervening f.; addles are 

rounded and undivided. Most of the saddles between the 

lateral lobe and the umbilicus are bifid. 

The holotype came from a large, silty, calcareous 

concretion at USGS Mesozoic locality 24065 near Teigen 

in central Montana (fig. 1). This concretion yielded 400 

specimens of M. teigenense, along with 3,800 specimens 

of Neogastroplites muelleri Reeside and Cobban (Reeside 

and Cobban, 1954). Most of the Metengonoceras consist of fragments of less than half a whorl. Only 28 specimens are complete enough for measurements of the 

diameter at the base of the body chamber. These show 

a wide range in size that probably indicates both immature and mature growth stages (fig. 4). We are unable 

to demonstrate dimorphism. The largest phragmocone 

has a diameter of 168 mm, which is probably also the 

diameter at the base of the body chamber (pl. 5, figs. 

1-3). The largest complete adult, an internal mold, has 

a diameter of 170 mm (pl. 4, figs. 7, 8). Slightly more 

than half of the outer whorl is a body chamber that has 

a diameter of 112 mm at its base. The venter of this internal mold is sharp to the aperture. On this individual, 

as well as on other adult body chambers, the aperture 

is normal and follows the shape of the growth lines. 

Whorls of specimens 2.0 to 2.5 mm in diameter 

from locality 24065 are about as high as wide with 

rounded flanks that grade evenly into rounded venters. 

At diameters from 2.5 to 3.0 mm, the whorls become 

higher than wide, and the venter flattens a little. Whorls 

become progressively higher with growth, and the flanks 

flatten. At a diameter of 4.5 mm, the height may be twice 

that of the width with the greatest width at the umbilical 

shoulder. The venter becomes very narrow and slightly 

concave on both shelled specimens and internal molds. 

At some diameter between 30 and 45 mm, the venter on 

internal molds becomes sharp. Specimens that retain shell 

material have very narrow flat venters at least to a 

diameter of about 100 mm. At larger diameters, the flattening may be lost. 

Ornament is inconspicuous and usually consists 

only of falcoid growth lines. Under oblique lighting, faint 

arcuate ribs that number 8 to 10 per half whorl are discernible just above midflank on some body chambers and 
6 

(/) 

z 5 UJ 

~ 

u 4 UJ 

a_ 

(/) 

u.. 3 0 

a: 

UJ 2 CD 

~ 

::::> 

z 

50 60 70 80 90 100 110 120 130 140 150 160 170 

DIAMETER, IN MILLIMETERS 

Figure 4. Histogram showing range in size of base of body chambers of 28 specimens of Metengonoceras teigenense , n. sp., 

from USGS Mesozoic locality 24065 near Teigen, Mont. (fig. 1 ). 

outer septate whorls. An occasional septate whorl may 

have faint prorsiradiate umbilical foldlike ribs that 

number about 5 per half whorl. 

Sutures are distinctive and fairly complex for the 

genus. Most sutures have narrow-necked lateral and 

adventitious lobes whose branches may touch one another 

(figs. 5C, D). Saddles that separate these lobes are usually 

round and undivided. Lobes between the lateral lobe and 

the umbilicus are generally narrow and bifid or undivided. 

Saddles that separate these lobes vary considerably; some 

may be undivided (fig. 5B), some may be bifid (fig. 5A), 

and some may be irregularly trifid (fig. 5B). In this part 

of the suture, a pair of lobes may be close together and 

are separated by a narrow, deep saddle (figs. 5B, C), 

similar to a pair on a suture of Engonoceras uddeni 

(Cragin) illustrated by Hyatt (1903, pl. 19, fig. 1), as well 

as a pair on a suture of Metengonoceras acutum Hyatt 

(1903, pl. 27, fig. 2). The short, bowtielike external lobe 

is centered on the middle of the venter on whorls less than 

15 mm in diameter, but, as the whorls enlarge, the lobe 

usually drifts off center either to the right (figs. 5C, D) 

or to the left (figs. 5A, B). This shifting of the lobe occurs at some diameter from 15 to 35 mm. Observations 

on 317 specimens larger than 35 mm diameter revealed 

that only 13 still had the lobe centered on the venter. Of 

the remainder, 158 had the lobe off to the right, and 146 

had it off to the left. 

Discussion.-Metengonoceras teigenense, n. sp., 

seems most closely related toM. dumbli (Cragin) of middle and late Cenomanian age and to M. acutum Hyatt 

of late Cenomanian age. All three species are of comparable size and have smooth or nearly smooth shells and 

similar sutures. Metengonoceras dumbli (Cragin, 1893, 

p. 243, pl. 44, fig. 6), which has been well illustrated from 

the Cenomanian Woodbine Formation of north Texas 

by Stephenson (1953, p. 206, pl. 55, figs. 1-4), Kennedy 

and others (1981, p. 32, pl. 3, figs. 1-5; pl. 7, figs. 4-6; 

text figs. 4a-g, 5b-f) and Cobban (1987, p. C2, pl. 1, 

figs. 3-6, 8; pl. 2, figs. 1-3, 9, 10; text fig. 1) differs from 

M. teigenense in that it has a stouter shell and the adventitious lobes of its suture have less deeply divided branches. Metengonoceras acutum Hyatt (1903, p. 184, pl. 

26, fig. 8; pl. 27, figs. 1, 2), which was described from 

the Cenomanian and Turonian Eagle Ford Group of 

north Texas, may differ from M. teigenense only in its 

more acute venter. Hyatt (1903, p. 184) mentioned the 

presence of broad, foldlike costae near the umbilical 

shoulder, but this ornament is not present on the few 

specimens at hand from the Eagle Ford. 

Occurrence.-The holotype and paratypes of M. 

teigenense are from a large silty concretion below the middle of the Mowry Member of the Colorado Shale at 

USGS Mesozoic locality 24065 in east-central Montana. 

The species is known only from a few localities in central and east-central Montana (fig. 1) in the zone of 

Neogastroplites muelleri Reeside and Cobban. 

ORIGIN AND AGE OF THE MOWRY 

METENGONOCERAS 

Reeside and Cobban (1960, p. 26, 27) recognized 

the following five biostratigraphic assemblages (zones) 

of the ammonite Neogastroplites McLearn, 1931, and 

their interpreted chronostratigraphic sequence in the 

Western Interior of the United States is: 

Neogastroplites mac/earni (youngest) 

N. americanus 

N. muelleri 

N. cornutus 

N. haasi (oldest) 

Metengonoceras was not found in the oldest zone, and 

only two fragments were observed in the next zone of N. 

cornutus. Only the zones of N. muelleri and N. 

americanus contain abundant Metengonoceras. 

Although Reeside and Cobban (1960, table 1) had 

124 collections of Mowry ammonites, specific names 

could be assigned only to about half of these owing to 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming L7 
A 

B 

c 

D 

5mm 

I 

\ 

( 

Figure 5. External sutures of Metengonoceras teigenense, n. sp., from USGS Mesozoic locality 24065 (fig. 1 ). A, Paratype USNM 

420352 at a whorl height of 38 mm. 8, Paratype USNM 420353 at a whorl height of 57 mm. C, Paratype USNM 420354 at a 

whorl height of 43 mm. 0, Paratype USNM 420355 at a whorl height of 62.5 mm. Heavy straight line marks middle of external 

(siphonal) lobe; light straight line marks middle of venter; dashed curve line marks umbilical shoulder; solid curved line marks 

umbilical seam. 

L8 Evolution of Sedimentary Basins-Uinta and Piceance Basins 
flattened or poorly preserved specimens. Those authors 

pointed out the difficulties in determining the stratigraphic succession of these geographically widely distributed 

collections. The present investigation suggests that the 

zones of N. muelleri and N. americanus should be reversed in their order. Metengonoceras aspenanum, which 

lies in the zone of N. americanus, is stouter and a little 

more ornamented than M. teigenense, n. sp., and in these 

features N. aspenanum more closely resembles the lower 

Cenomanian species of Metengonoceras from Texas than 

does M. teigenense from theN. muelleri zone. Metengonoceras teigenense, on the other hand, has the smoothflanked, sharp-ventered appearance of the younger M. 

dumbli and M. acutum of the middle and upper 

Cenomanian. 

The Tethyan family Engonoceratidae is well represented in the upper Albian-lower Cenomanian Washita 

Group of Texas. The presence of numerous specimens 

of Metengonoceras as far north as central Montana is 

remarkable. Inasmuch as only a few fragments of 

engonoceratids have been found farther north in central 

western Alberta (Thorsteinson, 1952, p. 30), the origin 

of the Mowry Metengonoceras seems to be in the Gulf 

region. 

Neither of the Mowry species is known in the Gulf 

faunas. Both M. aspenanum and M. teigenense are more 

involute than any of the Albian and lower Cenomanian 

species of Texas, which gives the Mowry species a postWashita Group aspect. The youngest engonoceratids in 

the USGS collections from the Washita Group are 

Engonoceras retardum Hyatt (1903, p. 160, pl. 19, 

figs. 15-17) and Metengonoceras bravoense (Bose), both 

found in the Grayson Formation in north Texas. 

Engonoceras retardum is an ornate species that has umbilical and mid-flank tubercles; there is nothing like it in 

the Mowry faunas. Metengonoceras bravoense, however, 

rather closely resembles M. aspenanum and could have 

given rise to it by becoming more involute and a little 

stouter. 

Metengonoceras may have migrated northwestward 

across northwestern Texas and eastern New Mexico soon 

after the close of Grayson time (earliest Cenomanian) and 

entered the Western Interior seaway in southeastern Colorado. There are no known records of this postulated 

event. The Grayson Formation of north Texas is overlain 

disconformably by the middle Cenomanian Woodbine 

Formation, and the Buda Limestone, of late Grayson age 

in southwestern Texas, is overlain disconformably by the 

Boquillas Formation of which the basal beds range in age 

from early to middle Cenomanian. Two lower Cenomanian ammonoid faunas have been described from strata 

above the Buda Limestone in southwestern Texas (Young, 

1958; Cobban and Kennedy, in press), but engonoceratids 

have not been recorded. The youngest marine rocks of 

Washita age in northeastern New Mexico are included in 

the Pajarito Shale Member of the Purgatoire Formation, 

where Lopha quadriplicata (Shumard) has been recorded 

(Dobrovolny and others, 1947). This bivalve has a range 

of upper Albian into lower Cenomanian (Fort Worth, 

Denton, Weno, and Main Street Formations in north 

Texas; Adkins, 1928, p. 105). At many places the Pajarito 

Member is overlain by a cross bedded sandstone unit that 

has been recently referred to as the Romeroville Sandstone (Kues and Lucas, 1987). The unit is possibly a nonmarine equivalent of the Grayson-Buda sequence. 

Overlying the Romeroville Sandstone of Kues and Lucas 

(1987, fig. 3) is the marine Graneros Shale, which consists of lower and upper unnamed shale members 

separated by the Thatcher Limestone Member. The Thatcher Member contains a middle Cenomanian Conlinoceras tarrantense fauna in southeastern Colorado 

(Cobban and Scott, 1973), but the lower unnamed shale 

member has not yielded diagnostic fossils. A marine connection between the Western Interior and Gulf coastal 

basins probably existed at sometime during deposition 

of the lower shale member, and during that time 

Metengonoceras may have entered the Western Interior 

basin. 

Although the relative stratigraphic position of the 

two Metengonoceras faunas cannot be proven without 

additional field work, both faunas have a post-Washita 

appearance, and both are herein considered of early 

Cenomanian age. The age of the few fragments of 

Metengonoceras in the older zone of Neogastroplites cornutus cannot be determined from the material at hand, 

but the age may well be early Cenomanian. 

The age of the Neogastroplites faunas has usually 

been considered as late Albian or late late Albian, but 

the endemic nature of the faunas has prevented a definite 

correlation with the type Albian faunas of Europe. 

Reeside and Cobban (1960), following the Albian 

assignments by Canadian and British paleontologists (for 

example, McLearn, 1931, 1932; Spath, 1937; Warren and 

Stelck, 1958), considered the faunas as latest Albian 

"with the reservation that they may possibly belong to 

the earliest Cenomanian" (Reeside and Cobban, 1960, 

p. 1). 

Neogastroplites has been said to occur on the 

Pacific side of the U.S.S.R., where specimens have been 

identified as N. americanus, N. cf. maclearni, and N. cf. 

muelleri (Pergament, 1977, p. 90). Other ammonites listed 

from this Neogastroplites zone are upper Albian forms. 

Pergament did not illustrate the Neogastroplites, but 

Avdeiko (1968) had earlier figured a few small specimens 

as N. cf. muelleri, N. cf. americanus, and N. cf. maclearni. Jeletzky (1980, p. 39), after thoroughly investigating 

Neogastroplites and related genera concluded that 

Neogastroplites is endemic to and confined to the Western 

Interior basin and that the Soviet records of the genus 

are questionable. 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming L9 
RE FE RE NCES CITED 

Adkins, W.S., 1928, Handbook of Texas Cretaceous fossils: 

Texas University Bulletin 2838, 385 p., 37 pis. 

Amedro, Francis, and Destombes, Pierre, 1984, Presence du 

genre Knemiceras (Ammonoidea, Engonoceratidae) dans I' Albien moyen de 1' Au be (France) [Occurrence of the genus 

Knemiceras (Ammonoidea, Engonoceratidae) in the middle 

Albian of the Aube (France)]: Bulletin d'Information des 

Geologues du Bassin de Paris, v. 21, no. 4, p. 21-25. 

Avdeiko, G.P., 1968, Nizhnemelovye otlozheniia severa 

Tikhookeanskogo Kolt'sa (Lower Cretaceous deposits in the 

northern part of the Pacific ring): Akademiia Nauk SSSR, 

Sibirskoye Otdelenie Instituta Volkanologii, Nauka Press, 

Moscow, 136 p. 

Barber, W.M., 1957, Lower Turonian ammonites from northeastern Nigeria: Nigeria Geological Survey Bulletin 26, 67 p., 

34 pis. 

Basse, Eliane, 1940, Les cephalopodes cretaces des massifs 

cotiers syriens [Cretaceous cephalopods of the Syrian coastal 

massifs], Part 2, of Etudes paleontologiques [Paleontologic 

studies]: Haut-Commissariat Republique Francaise, Syrie et 

Liban, Section Etudes Geologie, Notes et Memoires, v. 3, 

p. 411-471, 9 pis. 

Bose, Emil, 1928, Cretaceous ammonites from Texas and northern Mexico: University of Texas Bulletin 2748, p. 143-312, 

18 pis. [1927 imprint]. 

Cobban, W.A., 1983, Molluscan fossil record from the northeastern part of the Upper Cretaceous seaway, Western Interior, in Cobban, W .A., and Merewether, E.A., Stratigraphy 

and paleontology of mid-Cretaceous rocks in Minnesota and 

contiguous areas: U.S. Geological Survey Professional Paper 

1253-A, p. 1-23, pis. 1-15. 

___ 1987, The Upper Cretaceous (Cenomanian) ammonites 

Metengonoceras dumbli (Cragin) and M. acutum Hyatt: U.S. 

Geological Survey Bulletin 1690, p. C1-C7, 3 pis. 

Cobban, W.A., and Kennedy, W.J., in press, Acompsoceras 

inconstans zone, a lower Cenomanian marker horizon in 

Trans-Pecos Texas: Neues Jahrbuch fUr Geologie und 

Palaontologie Abhandlungen. 

Cobban, W.A., and Reeside, J.B., Jr., 1951, Lower Cretaceous 

ammonites in Colorado, Wyoming, and Montana: American 

Association of Petroleum Geologists Bulletin, v. 35, no. 8, 

p. 1892-1893. 

Cobban, W.A., and Scott, G.R., 1973, Stratigraphy and ammonite fauna of the Graneros Shale and Greenhorn 

Limestone near Pueblo, Colorado: U.S. Geological Survey 

Professional Paper 645, 108 p., 41 pis. [1972 imprint]. 

Cragin, F.W., 1893, A contribution to the invertebrate paleontology of the Texas Cretaceous: Texas Geological Survey 4th 

Annual Report, pt. 2, p. 139-246, pis. 24-46. 

Dobrovolny, Ernest, Summerson, C.H .. , and Bates, R.L., 1947, 

Geology of northwestern Quay County, New Mexico: U.S. 

Geological Survey Oil and Gas Investigations Preliminary 

Map 62, text and map, scale 1 inch to 1 mile. 

Furon, Raymond, 1935, Le Cretace et le Tertiaire du Sahara 

soudanais (Soudan, Niger, Tchad) [The Cretaceous and Tertiary of the Sudanese Sahara (Sudan, Niger, and Chad)]: 

Museum National Histoire Naturelle Archives, 6th ser., v. 

13, p. 1-96, pis. 1-7. 

L10 Evolution of Sedimentary Basins-Uinta and Piceance Basins 

Grossouvre, Albert de, 1912, Le Cretace de Ia Loire-Inferieure 

et de Ia Vendee [The Cretaceous of the lower Loire and the 

Vendee]: Societe des Sciences Naturelles de !'Ouest de Ia 

France Bulletin, 3d ser., v. 2, p. 1-38, pls. 1-3. 

Hyatt, Alpheus, 1900, Cephalopoda, in Zittel, K.A., von, 

1896-1900, Textbook of palaeontology: London, MacMillan, 

p. 502-604. 

___ 1903, Pseudoceratites of the Cretaceous, edited by T.W. 

Stanton: U.S. Geological Survey Monograph 44, 351 p., 47 

pis. 

Jeletzky, J.A., 1980, New or formerly poorly known, 

biochronologically and paleobiogeographically important 

gastroplitinid and cleoniceratinid (Ammonitida) taxa from 

middle Albian rocks of mid-western and Arctic Canada: 

Geological Survey of Canada Paper 79-22, 63 p., 10 pis. 

Kennedy, W.J., and Cobban, W.A., 1976, Aspects of ammonite 

biology, biogeography, and biostratigraphy: Palaeontological 

Association of London Special Papers in Palaeontology 17, 

94 p., 11 pis. 

Kennedy, W.J., and Hancock, J.M., 1978, The mid-Cretaceous 

of the United Kingdom, in Mid-Cretaceous events, UppsalaNice symposium, 1975-1976: Annales du Museum d'Histoire 

Naturelle de Nice, v. 4, p. v. 1-v. 72, 30 pis. [1976 imprint]. 

Kennedy, W.J., Juignet, Pierre, and Hancock, J.M., 1981, Upper Cenomanian ammonites from Anjou and the Vendee, 

western France: Palaeontology, v. 24, pt. 1, p. 25-84, pis. 

3-17. 

Kues, B.S., and Lucas, S.G., 1987, Cretaceous stratigraphy and 

paleontology in the Dry Cimarron Valley, New Mexico, Colorado and Oklahoma: New Mexico Geological Society Field 

Conference, 38th, Northeastern New Mexico, Guidebook, 

p. 167-198. 

McLearn, F.H., 1931, The Gastroplites and other Lower 

Cretaceous faunas of the northern Great Plains: Royal Society 

of Canada Transactions, 3rd ser., v. 25, sec. 4, p. 1-7,2 pis. 

___ 1932, Problems of the Lower Cretaceous of the Canadian Interior: Transactions of the Royal Society of Canada, 

3rd ser., v. 26, sec. 4, p. 157-175. 

Pergament, M.A., 1977, Stratigraphy and correlation of midCretaceous of the USSR Pacific regions, in Mid-Cretaceous 

Events, Hokkaido Symposium, 1976: Palaeontological Society of Japan Special Paper 21, p. 85-95. 

Pervinquiere, Leon, 1907, Etudes de paleontologie tunisienne, 

Part 1, Cephalopodes des terrains secondaires [Studies of 

Tunisian paleontology, part 1, Cephalopods of secondary terrains]: Carte Geologique Tunisie, 438 p., 27 pis. 

Reeside, J.B., Jr., and Cobban, W.A., 1954, Ammonite accumulations in the Cretaceous Mowry and Aspen shales: 

Science, v. 119, no. 3089, p. 355. 

__ 1960, Studies of the Mowry shale (Cretaceous) and 

contemporary formations in the United States and Canada: 

U.S. Geological Survey Professional Paper 355, 126 p., 

58 pis. 

Reeside, J.B., Jr., and Weymouth, A.A., 1931, Mollusks from 

the Aspen shale (Cretaceous) of southwestern Wyoming: U.S. 

National Museum Proceedings, v. 78, art. 17, 24 p., 4 pis. 

Roman, Frederic, 1938, Les ammonites jurassiques et cretacees; 

Essai de genera [Jurassic and Cretaceous ammonites; essays 

on genera]: Paris, Masson et Cie, 554 p., 53 pis. 
Schneegans, Daniel, 1943, Invertebres du cretace superieur du 

Damergou (Thrritoire du Niger); avec une Note sur les 

echinides de Marma par J. Lambert [Upper Cretaceous invertebrates of Damergou (Niger); with a note on the echinoids 

of Marma by J. Lambert]: French West Africa, Direction des 

Mines, Bulletin 7, p. 87-166, 8 pis. 

Spath, L.F., 1924, On a new ammonite (Engonoceras iris, sp. 

n.) from the Gault of Folkestone: Annals and Magazine of 

Natural History, 9th ser., v. 14, no. 82, p. 504-508. 

___ 1931, A monograph of the Ammonoidea of the Gault, 

Part 8: Palaeontographical Society [Monograph], p. 313-378, 

pis. 31-36. 

___ 1937, The Canadian ammonite genus Gastroplites in the 

English Gault: Annals and Magazine of Natural History, ser. 

10, v. 19, p. 257-260. 

Stephenson, LW., 1953, Larger invertebrate fossils of the Woodbine formation (Cenomanian) of Thxas: U.S. Geological Survey 

Professional Paper 242, 211 p., 58 pis. [1952 imprint]. 

Thorsteinson, Raymond, 1952, Grande Cache map area, 

Alberta: Geological Survey of Canada Paper 52-26, 44 p., 

map. 

Warren, P.S., and Stelck, C.R., 1958, Lower Cenomanian Ammonoidea and Pelecypoda from Peace River area, western 

Canada: Research Council of Alberta, Geological Division, 

Bulletin 2, p. 36-51, pis. 5-16. 

Wright, C.W., 1963, Cretaceous ammonites from Bathurst 

Island, Northern Australia: Palaeontology, v. 6, pt. 4, p. 

597-614, pis. 81-89. 

Young, Keith, 1958, Cenomanian (Cretaceous) ammonites from 

Trans-Pecos Texas: Journal of Paleontology, v. 32, no. 2, 

p. 286-294, pis. 39, 40. 

Zaborski, P.M.P., 1987, Lower Turonian (Cretaceous) ammonites from south-east Nigeria: Bulletin of the British 

Museum of Natural History (Geology), v. 41, no. 2, 

p. 31-66. 

Ammonite Metengonoceras Hyatt, Mowry Shale, Montana and Wyoming L 11 

Y:r U.S. GOVERNMENT PRINTING OFFICE: 1989-773-047/06,014 REGION NO.8 
PLATES 1-5 

Contact photographs of the plate in this report are available, 

at cost, from U.S. Geological Survey P~otographic Library, 

Federal Center, Denver, CO 80225 
PLATE 1 

[All figures natural size. Locality shown on text figure 1] 

Metengonoceras aspenanum (Reeside and Weymouth). From the Colorado Shale at USGS Mesozoic locality 23042 

near Winnecook, Meagher County, Mont. 

Figures 1 ,2. Hypotype USNM 420357. 

3,4. Hypotype USNM 420358. See text figure 5A for the suture. 

5,6. Hypotype USNM 420359. 

7-9. Hypotype USNM 420360. 

10. Hypotype USNM 420361. 

11, 16, 17. Hypotype USNM 420362. 

12, 13. Hypotype USNM 420363. 

14, 15. Hypotype USNM 420364. 

18, 19. Hypotype USNM 420365. 

20, 21. Hypotype USNM 420366. 

22, 23. Hypotype USNM 420367. 
U.S . GEOLOGICAL SURVEY BULLETIN 1787- L PLATE 1 

9 

METENGONOCERAS 
PLATE 2 

[All figures natural size. Locality shown on text figure 1] 

Metengonoceras teigenense n. sp. From the Mowry Member of the Colorado Shale at USGS Mesozoic locality 24065 

near Teigen, Petroleum County, Mont. 

Figure 1. Para type USNM 420342. See plate 3, figures 1 ,2, for rear and front views. 

2-4. Paratype USNM 420343. 

5-7. Holotype USNM 420341. 
BULLETIN1787- L PLATE2 

U.S . GEOLOGICAL SURVEY 

4 

2 3 

7 

5 6 

METENGONOCERAS 
PLATE 3 

[All figures natural size. Locality shown on text figure 1] 

Metengonoceras teigenense n. sp. From the Mowry Member of the Colorado Shale at USGS Mesozoic locality 24065 

near Teigen, Petroleum County, Mont. 

Figures 1 ,2. Paratype USNM 420332. See plate 2, figure 1, for side view. 

3-5. Paratype USNM 420344. 

6-8. Paratype USNM 420345. 
U.S. GEOLOGICAL SURVEY BULLETIN 1787 - L PLATE 3 

2 

6 7 8 

METENGONOCERAS 
PLATE 4 

[All figures natural size. Locality shown on text figure 1] 

Metengonoceras teigenense n. sp. From the Mowry Member of the Colorado Shale at USGS Mesozoic locality 24065 

near Teigen, Petroleum County, Mont. 

Figures 1,5,6. Paratype USNM 420349. 

2. Paratype USNM 420346. 

3. Paratype USNM 420347. 

4. Paratype USNM 420348. 

7 ,8. Paratype USNM 420350. 
U.S. GEOLOGICAL SURVEY 

7 

METENGONOCERAS 

BULLETIN 1787-L PLATE 4 

8 
PLATE 5 

[All figures natural size. Locality shown on text figure I] 

Metengonoceras teigenense n. sp. From the Mowry Member of the Colorado Shale at USGS Mesozoic locality 24065 

near Teigen, Petroleum County, Mont. Paratype USNM 420351. 
U.S. GEOLOGICAL SURVEY 

3 

2 

METENGONOCERAS 
f?®lr~©cdl~~~~~ 

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and other material that are made available for public consultation at 

depositories. They are a nonpermanent form of publication that may be 

cited in other publications as sources of information. 

M~IP$ 

Geollo~ftc Qllll&dr&I!D.~lle M&ps are multicolor geologic maps on 

topographic bases in 7 1/2- or 15-minute quadrangle formats (scales mainly 1 :24,000 or 1 :62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only. 

GeojpllllyskSIH III!D.ves~ftg&ft!om Mm~ps are on topographic or planimetric 

bases at various scales; they show results of surveys using geophysical 

techniques, such as gravity, magnetic, seismic, ·or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology. 

Mlft~elln&I!D.eollll§ III!D.vesa.ftg&~ftoi!D.s §errftes Ml&ps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide vanety of format and subject matter. The series also includes 7 112-minute quadrangle photo geologic maps on planimetric bases 

which show geology as iitterpreted from aerial photographs. Series also 

includes maps of Mars and the Moon. 

Co&ll III!D.ves~lg&~!oi!D.s M!&ps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy, and structural relations in certain coal-resource areas. 

Oftll &Hlld G&s III!D.ves~lga~ftonus Ch&r~ show stratigraphic information 

for certain oil and gas fields and other areas having petroleum potential. 

Mft~eD.lS~Jmeollll§ !Fftelld §~lllldftes Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations. 

IHiydroll<VgA«: III!D.ves~ftgaa.ftoi!D.S A~BSISes are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; principal scale 

is 1:24,000 and regional studies are at 1:250,000 scale or smaller. 

c~~~~Olg]$ 

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List.) 99

1Pun!Ollftcm~ft!onus oUllne GeollogftcSIH §llllrrvey, JU~7~- Jl.~llill." may be purchased by mail and over the counter in paperbaek book form and as a 

set of microfiche. 

"lPnn!ORftc&a.ftollD.s orr ru!ne GeoRogAc&ll §llllrvey, R~152- D970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 91

lPunbHic&~ftonus oll'~llne lU.§. Geolloglcall Survey, D97Jl.o Jl.~3Jl." may be 

pmchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

SllllJPJPRemellD.~ for 1982, 1983, 1984, 1985, 1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form. 

§~&~e c<slllogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only 

"IFrrfice &nud Av&ftll&!OA.llftcy !Lfts~ oll' lU.§. GeoRogkSIH §W"vey lPubRftetno 

ft!Ollll.S," issued annually, is available free of charge in paperback booklet form only. 

§eRededcopftesolT& monnllllD.Ryc<slllog "New Publications of the U.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092. 

No~e.--Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications·.