Middle Jurassic (Bajocian and Bathonian) 

Ammonites From Northern Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 854
Middle Jurassic (Bajocian and Bathonian) 

Ammonites From Northern Alaska

By RALPH W. IMLAY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 854

An ammonite succession nearly identical ivith 

that in northern Canada is correlated with 

a more varied ammonite succession in 

southern Alaska

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976
UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Imlay, Ralph Willard, 1908-

Middle Jurassic (Bajocian and Bathonian) ammonites from northern Alaska. 

(Geological Survey professional paper; 854) 

Bibliography: p. 

Includes index.

Supt. of Docs. no. : I 19.16:854

1. Ammonoidea. 2. Paleontology Jurassic. 3. Paleontology Alaska. I. Title. II. Series: United States. Geological Survey. Professional paper; 854. 

QE807.A5I615 564'.53'097987 74-20556

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

Washington D.C. 20402 

Stock Number 024-001-027305
CONTENTS

Abstract __________________. 

Introduction ________________. 

Biologic analysis ____________.

Stratigraphic summary ________.

Stratigraphic distribution of ammonites 

Ages and correlations __________.

Bajocian ammonites ________.

Bathonian ammonites _______ 

Ammonite faunal setting _______.

Geographic distribution ______ __ _-

Systematic descriptions _________

References cited ___________ ____.

Index __________________.

Page 

1 

1

1

2

3

5

5

7

7

7

10

18

21

ILLUSTRATIONS

[Plates follow index]

PLATE 1. Pseudolioceras, Canavarella, Oppelia (Liroxyites), Arkellocerasl, and Arkelloceras.

2. Cranocephalites and Choffatial.

3. Arcticoceras, Arcticocerasl, and Erycitoides.

4. Arctocephalites and Choffatial.

FIGURE 1. Diagram showing occurrences and ages of fossils in Kingak Shale exposed on Canning River west of 

Shublik Island, northern Alaska ______-_ __________ 

2. Chart showing correlation of Bajocian and Bathonian faunas in northern Alaska _ 

3. Generalized index map of Bajocian ammonite localities in northern Alaska _ _ -______

4. Generalized index map of Bathonian ammonite localities in northern Alaska _______________________

5. Detailed index map of Middle Jurassic ammonite localities in central part of Mt. Michelson quadrangle 

between the Canning and Sadlerochit Rivers ____________ 

Page

4

6

11

12

13

TABLES

TABLE 1. Ammonite genera and subgenera of Bajocian and Bathonian Age in northern Alaska _______________

2. Stratigraphic position and age of fossils in Kingak Shale exposed on northwest slope of Ignek Mesa, 

northern Alaska ______________________ _ _ __- 

3. Geographic distribution of ammonites of Bajocian and Bathonian Age in northern Alaska ____ ____

4. Description of some Middle Jurassic fossil localities in northern Alaska -

Page 

1

III
MIDDLE JURASSIC (BAJOCIAN AND BATHONIAN) AMMONITES

FROM NORTHERN ALASKA

By RALPH W. IMLAY

ABSTRACT

Middle Jurassic ammonites of Bajocian and Bathonian 

Age occur in northern Alaska within the Kingak Shale 

throughout thicknesses ranging from 300 to 850 feet (90- 

255 m) or more. Bajocian ammonites have been identified as 

far west as the Point Barrow area. Bathonian ammonites 

have -been identified as far west as the Canning River and 

are possibly present on the Saviukviayak River.

The Bajocian ammonite succession from the base upward 

consists of (1) Pseudolioceras maclintoeki (Haughton); (2) 

P. whiteavesi (White) in association with Erycitoides 

howeUi (White) and Canavarella crassifalcata Imlay, n. sp.; 

and (3) ArkeUoceras cf. A. tozeri Frebold. P. maclintoeki in 

northern Canada occurs at or near the base of the lower 

Bajocian; P. whiteavesi and E. howelli in southern Alaska 

occur at the top of the lower Bajocian; and ArkeUoceras on 

the Alaska Peninsula occurs above ammonites representing 

the Sonninia sowerbyi zone and near the base of an ammonite sequence representing the Otoites sauzei zone. The 

lack of younger Bajocian ammonites anywhere in northern 

Alaska is indicative of an unconformity.

The Bathonian ammonite succession from the base upward 

consists of (1) Cranocephalites sp., (2) C. iguekensis Imlay, 

n. sp., (3) Arctocephalites cf. A. elegans Spath, and (4) 

Arcticoceras ishmae (Keyserling). These ammonites, in comparison with the Bathonian ammonite succession in East 

Greenland, do not represent the highest and lowest parts of 

the stage, as defined for Greenland, nor do they represent 

the zone of Arctocephalites greenlandicus just below the zone 

of Arcticoceras ishmae. Perhaps the lack of representation 

on Ignek Mesa and elsewhere may be partly due to poor 

exposures. Nonetheless, an unconformity at the top of the 

Bathonian sequence in northern Alaska is indicated by the 

nearness of Arcticoceras to the early Oxfordian ammonite 

Cardioceras on Ignek Mesa and by the scarcity of definite 

Callovian ammonites in northern Alaska.

The Bajocian and Bathonian ammonite faunules in northern Alaska are closely similar to those in northern Canada 

and lived in the same faunal province. The inclusion of 

some species in common with faunules of the same ages in 

southern Alaska shows that the northern and southern seas 

were connected, although specifically the northern Alaskan 

faunas are much less varied.

New species described herein include Canavarella crassifalcata Imlay and Cranocephalites ignekensis Imlay.

INTRODUCTION

Middle Jurassic ammonites, representing the Bajocian and Bathonian Stages, are described herein

in order to present the latest available evidence concerning the stratigraphic and geographic distribution of the taxa and to show that the Bathonian 

Stage is well developed in northern Alaska. Much of 

the discussion concerning the Bajocian ammonites 

is a reinterpretation of the fossils described by the 

writer in 1955, but the discussion also includes some 

new fossil and stratigraphic data. All these new 

data, as well as most of the data concerning Bathonian ammonites, are based on fossils collected since 

1955 by geologists of British Petroleum (Alaska), 

Inc., in 1964, by consulting geologist Marvin Mangus in 1963 and 1966, and by U.S. Geological Survey 

geologists R. L. Detterman in 1969-72 and H. N. 

Reiser in 1970. The author is grateful to all these 

geologists for collecting the fossils, for preparing 

accurate locality maps and descriptions, and for 

furnishing stratigraphic data.

BIOLOGIC ANALYSIS

Northern Alaska ammonites of Bajocian and 

Bathonian Age that are discussed herein number 

220 specimens. Their distribution by genus, subfamily, and family is shown in table 1. Among the

TABLE 1. Ammonite genera and subgenera of Bajocian and 

Bathonian Age in northern Alaska

Family

Hildoceratidae ____

Hammatoceratidae _ 

Oppeliidae ________

Perisphinctidae ___

Subfamily

Harpoceratinae _______

Hammatoceratinae ____ 

Oppeliinae __-----__--

Pseudoperisphinctinae _

Genus and Number of 

subgenus specimens

Pseudolioceras ___

Erycitoides? _____ 

Oppelia 

(Liroxyites) ___

Cranocephalites

Arctocephalites __ 

Arctocephalites? _ 

Arcticoceras _____

65 

2 

25 

7 

5

1 

46 

22 

16 

6 

24 

1

families, the Hildoceratidae composes two-fifths, the 

Cardioceratidae nearly one-third, and the Stephanoceratidae one-fifth of the total specimens. The Hildoceratidae is represented mostly by Pseudolioceras 

but also includes Tmetoceras and Canavarella. The
BAJOCIAN AND BATHONIAN AMMONITES FEOM NOETHEEN ALASKA

Cardioceratidae is represented by nearly equal numbers of Arcticoceras, Arctocephalites, and Cranocephalites.

The characteristics of most of the genera and subgenera present have been adequately discussed in 

fairly recent publications. Pseudolioceras, Tmetoceras, and Erycitoides have been discussed by Westermann (1964, p. 358-360, 426-432; 1969, p. 18, 

52) ; Liroxyites, by Imlay (1962b, p. A8) ; Arkelloceras, by Frebold (1958, p. 9; 1961, p. 8-10; Frebold and others, 1967, p. 18-20) ; Cranocephalites 

and Arctocephalites, by Spath (1932, p. 14-16, 32, 

33), Arkell and others (1957, p. L301), and Imlay 

(1962a, p. C2) ; Arcticoceras, by Spath (1932, p. 50- 

53), Callomon (1959, p. 508), and Arkell and others 

(1957, p. L302) ; and Choffatia, by Spath (1931, p. 

325), Arkell and others (1957, p. L317), and Arkell 

(1958, p. 211).

The ammonites Cranocephalites, Arctocephalites, 

and Arcticoceras represent a biological and stratigraphic succession. Cranocephalites is characterized 

by a compressed to stout shell, a very small umbilicus on its septate whorls, a contracted body chamber, a terminal constriction, and high sharp ribbing 

that persists to the aperture but may be reduced in 

strength or interrupted on the venter of the adult 

body chamber. Arctocephalites differs from Cranocephalites mainly by having a body chamber that 

remains involute or only slightly contracted and 

that becomes abruptly smooth at a fairly small diameter. Arctioceras differs from Arctocephalites by 

attaining a much larger size and by having a sharpened venter, ribs that become sharper, coarser, and 

more strongly projected on the venter, and a body 

chamber that becomes smooth, or nearly smooth, 

and more involute. The small inner whorls of Arcticoceras greatly resemble Pseudocadoceras at the 

same size, but the middle and outer whorls are more 

involute, and the body whorl is much larger and is 

generally smooth.

The genus Canavarella Buckman (1904, Supp. p. 

CXXIX), not previously recorded from Arctic 

North America, is characterized by a moderately 

involute compressed shell, a low keel, and strong 

simple falcate ribs that project strongly forward on 

the venter. It differs from Cyclicoceras Buckman 

(1899, Supp., p. XLIX, pi. 5, figs. 5, 6; Arkell and 

others, 1957, p. L262, L263), mainly by having simple instead of biplicate ribs that project forward 

much more strongly on the venter. It differs from 

Pseudolioceras, with which it is associated in Alaska, by having a wider umbilicus, stronger ribs on 

its inner whorls, and falcate instead of falcoid ribs.

Canavarella in England is recorded from the zone 

of Tmetoceras scissum (Arkell and others, 1957, p. 

L262) near the base of the Middle Jurassic. In 

northern Alaska, it is associated with Pseudolioceras whiteavesi (White) and Erycitoides cf. E. 

howelli (White).

STRATIGRAPHIC SUMMARY

Middle Jurassic beds in northern Alaska have 

been identified faunally in the subsurface of the 

Point Barrow-Cape Simpson area (Imlay, 1955, p. 

82, 89), in a few outcrops between the Killik and 

Itkillik Rivers in north-central Alaska (Patton and 

Tailleur, 1964, p. 444), and in extensive outcrops 

between the Sagavanirktok and Aichilik Rivers in 

northeastern Alaska (Imlay and Detterman, 1973, 

p. 9, 12). At most places they consist of siltstone, 

silty shale, and pyritic clay shale that contain ironstone concretions and are mostly noncalcareous. In 

the Killik-Itkillik area, however, the beds consist of 

interbedded tuffaceous graywacke, siltstone, claystone, chert, and silty limestone.

In northeastern Alaska, the Bathonian and Bajocian parts of the Middle Jurassic are readily distinguished lithologically. The Bajocian part is 

typically dark gray to black, weathers nearly the 

same color, and contains some limy concretions. 

The Bathonian part differs by being mostly grayish 

green on fresh surfaces, by commonly weathering 

reddish brown, and by containing more siltstone 

beds, more ironstone concretions, and less pyritic 

and limy material.

Thickness of the Middle Jurassic beds ranges 

from about 300 feet (90 m) or less in north-central 

Alaska to 850 feet (255 m) or more in northeastern 

Alaska. Beds of Bathonian Age attain a maximum 

thickness of nearly 500 feet (150 m), are highly 

variable in thickness locally, extend west at least as 

far as the Canning River, and possibly extend to 

the Saviukviayak River. Beds of Bajocian Age attain a greater thickness than overlying Bathonian 

beds, are likewise highly variable in thickness 

locally, and extend much farther west.

Within the Middle Jurassic sequence in northeastern Alaska, an unconformity is demonstrated by the 

complete lack of ammonites of late middle and late 

Bajocian Age, by the highly variable thickness of 

earlier Bajocian beds within short distances, and by 

the close proximity of dated lower Bathonian to 

lower or lower middle Bajocian beds. In the KillikItkillik area of north-central Alaska, an even 

greater unconformity is demonstrated by an absence
STRATIGRAPHIC DISTRIBUTION 3

of Jurassic ammonites and beds between the beds 

containing Arkellocerasl sp. juv. of probable middle Bajocian Age and beds containing Buchia fischeriana (d'Orbigny) of late Tithonian Age.

STRATIGRAPHIC DISTRIBUTION OF 

AMMONITES

The stratigraphic distribution of Middle Jurassic 

ammonites in northern Alaska has been difficult to 

determine because of poor exposures, structural 

complications, presence of erosional disconformities, 

and the rather similar appearance of dark siltstones 

and shales ranging in age from Late Triassic to 

Early Cretaceous.

The best and most continuous Middle Jurassic 

exposures found to date are in the cliffs along the 

southwest side of the Canning River from Shublik 

Island southeastward for about li/a miles (2.4 km). 

These exposures do not represent a continuous stratigraphic sequence, however, as shown by the presence of faults, contorted beds, and the repetition of 

some ammonite faunules. Nonetheless, in the northernmost mile of exposures is a sequence at least 

4,160 feet (1,248 m) thick in which ammonites of 

early Bajocian to early Kimmeridgian Age occur in 

normal succession. (See fig. 1.) Thus, within this 

sequence of 4,160 feet (1,248 m), early to early 

middle Bajocian ammonites occur throughout the 

lower 2,400 feet (720 m), and late Oxfordian to 

early Kimmeridgian ammonites occur in the upper 

1,040 feet (312 m). Between the Bajocian and Oxfordian occurrences are 720 feet (216 m) of beds 

from which the Bathonian ammonite Arctocephalites was collected about 120 feet (36 m) above the 

highest occurrence of the middle Baj ocian ammonite 

Arkelloceras.

In addition to the Bajocian and Bathonian fossils 

listed in figure 1, the same cliff exposures near their 

south end have furnished single specimens of the 

late Bathonian ammonite Arcticoceras ishmae 

(Keyserling), preserved in a hard-worn siltstone 

nodule, and of the early Bajocian ammonite (Pseudolioceras whiteavesi (White), preserved in a pyritic nodule. These were collected (USGS Mesozoic 

loc. 21023) along with 20 specimens of P. maclintocki (Haughton) preserved in grayish-black siltstone. Presumably the specimens of P. maclintocki 

were collected in place, whereas those of P. whiteavesi and Arcticoceras ishmae were derived from 

float either from higher beds exposed on the cliffs 

or from another Jurassic exposure about a mile 

(1.6 km) southeast of the south end of Shublik 

Island. On the basis of stratigraphic data from

other areas, P. whiteavesi should occur directly 

above P. maclintocki, and Arcticoceras ishmae 

should occur above Arctocephalites.

The next best exposure of Middle Jurassic rocks 

and the most complete Bathonian ammonite succession known in northern Alaska occur on Ignek 

Mesa about 22 miles (35.2 km) northeast of the 

sequence west of Shublik Island. On the northwest 

slope of that mesa, the entire Jurassic section, as 

measured and collected by R. L. Detterman, is about 

750 feet (225 m) thick. The section appears to be 

unfaulted, but contains covered intervals that are 

more common toward the base. Detterman collected 

fossils of early Bajocian to early Oxfordian Age 

from six different beds or units. His collections, 

listed stratigraphically from highest to lowest, are 

as follows:

Cardioceras (Scarburgiceras) sp. (USGS Mesozoic loc.

29856)

Arcticoceras sp. (USGS Mesozoic loc. 29877) 

Cranocephalites ignekensis Imlay, n. sp. (USGS Mesozoic

loc. 29855)

Cranocephalites sp. (USGS Mesozoic loc. 29875) 

Inoceramus cf. /. ambiguus Eichwald (USGS Mesozoic loc.

29854) 

/. Incifer Eichwald (USGS Mesozoic loc. 29853)

From the same sequence, at the northwest end of 

Ignek Mesa, the following fossils, listed stratigraphically from highest to lowest, were collected by 

geologists of British Petroleum (Alaska) Inc.:

Arctocephalites cf. A. elegans Spath (USGS Mesozoic loc. 

29144)

A. cf. A. elegans Spath and Cranocephalites ignekensis Imlay, n. sp. (USGS Mesozoic loc. 29143)

Inoceramus cf. /. Incifer Eichwald (USGS Mesozoic loc. 

29149)

/. Incifer Eichwald and Enjcitoidesl sp. (USGS Mesozoic 

loc. 29148)

From a nearby sequence 200 feet (60 m) below 

the base of the Ignek Formation at the southwest 

end of Ignek Mesa, Marvin Mangus collected Arctocephalites cf. A. elegans Spath and Cranocephalites 

ignekensis Imlay, n. sp. (USGS Mesozoic loc. 

29435). At the same stratigraphic position directly 

west of Ignek Mesa, he collected many specimens of 

C. ignekensis and Inoceramus cf. 7. ambiguus Eichwald but did not find Arctocephalites (USGS Mesozoic loc. 28817).

These records show that Arctocephalites definitely 

occurs above Cranocephalites at one locality and 

apparently with that genus at two localities. Their 

association does not seem natural, however. The 

fact that all the specimens of Arctocephalites are 

undeformed, whereas all the specimens of Cranocephalites are deformed or crushed, suggests that
BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

FEET 

6000-

 29142 (AG893) Arkelloceras 

Fault and contorted beds

Middle Bajocian

5000 

 29136 (AG887) Amoeboceras (Prionodoceras) and Buchia, concentrica Late Oxfordian to early 

Kimmeridgian

4000 

 29135 (AG882) Amoeboceras (Prionodoceras) and Buchia, concentrica,

3000 

 29146 (AG875) Arctocephalites

 29141 (AG873) Arkelloceras _

2000 29139 (AG868) Arkelloceras

Do.

Bathonian 

Middle Bajocian

Do.

1000-

 29138 (AG861) Arkelloceras

 29157 (AG857) Pseudolioceras maclintocki

Do.

Early Bajocian

FIGURE 1. Occurrences and ages of fossils in Kingak Shale exposed on Canning River west of Shublik Island, northern 

Alaska. Physical data furnished by British Petroleum (Alaska), Inc. Lower part of sequence probably duplicated by 

folding and faulting. USGS Mesozoic locality number is followed by collector's field number in parentheses.

the small round undeformed specimens of Arctocephalites have locally rolled down the slopes of 

Ignek Mesa onto older beds containing somewhat 

flattened specimens of Cranocephalites.

On the basis of these records, the Kingak Shale 

on Ignek Mesa includes a molluscan succession of 

Bajocian, Bathonian, and early Oxfordian Age, as 

shown in table 2. The Bajocian part of the lithologic sequence is probably 200-250 feet (60-75 m) 

thick, the Bathonian part at least 195 feet (58.5 m) 

thick, and the Oxfordian part at least 80 feet 

(24 m) thick. The sequence does not contain any 

ammonites of late middle and late Bajocian age or

of Callovian age. Their absence suggests that those 

times may be represented by disconformities.

The faunal succession of Bajocian Age found on 

the Canning River near Shublik Island is supplemented by a partial sequence of Kingak Shale exposed at the head of Katakturuk Canyon which is 

nearly 7 miles (11.2 km) west-northwest of the 

west end of Ignek Mesa. At this place the ammonite 

Canavarella, in association with Inoceramus lucifer 

Eichwald (USGS Mesozoic Iocs. 30267-30270), occurs 110-320 feet (33-96 m) above the base of the 

Kingak Shale. Previous collections, made by geologists of British Petroleum (Alaska), Inc., consist
AGES AND CORRELATIONS

of Pseudolioceras maclintocki (Haughton) (USGS 

Mesozoic loc. 29152) below beds containing Canavarella and Erycitoides (USGS Mesozoic loc. 

29153).

TABLE 2. Stratigraphic position and age of fossils in Kingak 

Shale in exposures on northivest slope of Ignek Mesa, 

northern Alaska

[Positions in feet determined by R. L. Detterman]

Cardioceras (Scarburgiceras) sp.

Arcticoceras sp. juv __

Arctocephalites cf. A.

elegans Spath.

Cranocephalites ignekensis Imlay, n. sp. 

Cranocephalites sp .__

Inoceramus cf. 7.

ambiguus Eichwald.

7. lucifer Eichwald ___

Feet below base of 

Ignek Formation 

(metres in 

parentheses)

80(24)

135(40.5)

Not known ___

275(82.5) 

310-330(93-99)

500(150)

600(180)

Age

Early Oxfordian.

Late Bathonian.

Middle or late

Bathonian.

[Early or middle 

f Bathonian.

Middle Bajocian

to Bathonian.

Early to early

middle

Bajocian.

Another partial Bajocian sequence, 150 feet (45 

m) thick, exposed on the west bank of Kaviak 

Creek, about 3 miles (4.8 km) southwest of its 

junction with the Sadlerochit River, is interesting 

stratigraphically because it contains the crinoid 

Pentacrinus siib angular is alaska Springer above, 

and probably al&o below, ammonites of early Bajocian Age. The evidence consists of Canavarella 

crassifalcata Imlay, n. sp., Pseudolioceras whiteavesi (White), and Inoceramus cf. /. lucifer Eichwald (USGS Mesozoic loc. 29884) in the lower 50 

feet (15 m), of the crinoid species in the middle 50 

feet, and of Pseudolioceras sp. and Erycitoides! sp. 

in the upper 50 feet (USGS Mesozoic loc. 29886).

This dating does not prove that all occurrences of 

P. subangularis alaska Springer are of early Bajocian Age. For example, an age as old as Pliensbachian is demonstrated by an occurrence near the 

Aichilik River of this crinoid species (USGS Mesozoic loc. 30073) at least 100 feet (30 m) below the 

ammonite Amaltheus (USGS Mesozoic loc. 30074). 

A similar age for the crinoid species at its type 

locality on the Canning River is supported by its 

association there with the same species of Plicatula 

that occurs with Amaltheus near the Aichilik River. 

In both localities the crinoid stems are much larger 

than those from lower Bajocian beds at Kaviak 

Creek (R. L. Detterman, written commun., 1973), 

a fact that may be of age significance.

This association of Pseudolioceras ivhiteavesi

(White) with Canavarella substantiates another 

such association (USGS Mesozoic loc. 29147). It 

also shows indirectly, by comparison with the ammonite sequence near Katakturuk Canyon that P. 

ivhiteavesi (White), as well as Canavarella, occurs 

higher stratigraphically than P. maclintocki 

(Haughton).

The exact stratigraphic position of Tmetoceras in 

northern Alaska, where it has been found only in 

well cores, has not been determined with respect to 

species of Pseudolioceras or of Canavarella. In 

southern Alaska, however, Tmetoceras occurs with 

Pseudolioceras whiteavesi (White) and Erycitoides 

howelli (White) as well as in directly underlying 

beds as much as 300 feet (90 m) thick (Westermann, 1964, p. 344-347, fig. 5). As its worldwide 

range probably corresponds to the entire lower Bajocian (Aalenian) (Westermann, 1964, p,, 432-435), 

its occurrences in northern Alaska could represent 

any part of that substage.

AGES AND CORRELATIONS 

BAJOCIAN AMMONITES

All three Bajocian ammonite faunules obtained 

from outcrops in northern Alaska (fig. 2) are associated with Inoceramus lucifer Eichwald, which in 

southern Alaska ranges through the Bajocian ais 

high as beds that correlate with the European Otoites sauzei zone (Imlay, 1964, p. 8-10, 18, 53). The 

lowest faunule, characterized by Pseudolioceras 

maclintocki Haughton, is tentatively correlated by 

Frebold (1960, p. 28) with the basal Bajocian zone 

of Leioceras opalinum, although it is not known 

from the same bed as that species. Apparently, P. 

maclintocki could represent either the lowest or the 

middle part of the lower Bajocian (Aalenian) or 

both. In southern Alaska, P. maclintocki and Leioceras opalinum are unknown, but the time that they 

represent probably corresponds in part to the development of an unconformity and the intrusion of 

the Aleutian Range batholith (Grantz and others, 

1963, p. B58; Detterman and Hartsock, 1966, p. 63, 

69, 71).

The second faunule above the base of the Jurassic 

is characterized by Pseudolioceras whiteavesi 

(White), by Canavarella crassifalcata Imlay, n. sp., 

and by Erycitoides similar to, or identical with, E. 

howelli (White). It is firmly dated as late early 

Bajocian because the same species of Pesudolioceras 

and Erycitoides occur in southern Alaska (Westermann, 1964, p. 345-352, fig. 5) directly below ammonite faunas characteristic of the Sonninia sower-
BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

st,

z 

<

z 

0

I

<

m

z 

< 

o

o 

<

m

age

0)

a 

a

D

 o 

 o

:?

Lower

0)

a 

a

D

 o

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L.

0)

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STANDARD ZONE 

IN NORTHWEST EUROPE

Clydoniceras discus

Oppelia aspidoides

Prohecticoceras retrocostatum

Morrisiceras morrisi

Tulites subcontracts

Procerites progracilis

Zigzagiceras zigzag

Parkinsonia parkinsoni

Garantiana garantiana

Strenoceras subfurcatum

Stephanoceras humphriesianum

Sonninia sowerbyi

Graphoceras concavum

Ludwigia murchisonae

Tmetoceras scissum

Leioceras opalinum

NORTHERN ALASKA 

(Imlay, 1955)

Arcticoceras ishmae

Arctocephalites cf. A. elegans

Cranocephalites ignekensis

Cranocephalites sp.

Inoceramus cf. 

I. ambiguus Eichwald

No fossil evidence

Arkelloceras

No fossil evidence

Erycitoides howelli, 

Pseudolioceras whiteavesi, and 

Canavarella cras&ifalcata

Tmetoceras 

(exact position unknown)

1« 

_s

«

nocerami

SOUTHERN ALASKA 

(Imlay, 1962a, b, 1964; 

Westermann, 1964, 1969)

Kepplerites 

 >

 >

Arctocephalites cf. A. elegans

 >

00

-o1

Cranocephalites costidensus

Angular unconformity on

Iniskin Peninsula

Megasphaeroceras rotundum, 

Leptosphinctes, and Sphaeroceras

Chondroceras allani, 

Normannites crickmayi, and

Teloceras itinsae

Stephanoceras kirschneri

Parabigotites eras sico status 

and Arkelloceras

No fossil evidence

Docidoceras widebayense

Erycitoides howelli, 

Pseudolioceras whiteavesi, 

and Tmetoceras scissum

Tmetoceras scissum

No fossil evidence

1

1

1

s

w

nocerami

FIGURE 2. Correlation of Bajocian and Bathonian faunas in northern Alaska.

byi zone (Westermann, 1969, p. 18, 22-30, figs. 6 

and 7) and with ammonite genera not known above 

the Graphoceras concavum zone (Westermann, 

1969, fig. 8 on p. 18).

The third faunule above the base of the Jurassic 

in northern Alaska is characterized by the ammonite 

Arkelloceras which has been recorded previously 

from the Canadian Arctic Islands (Frebold, 1957, p. 

9-11, pi. 9, figs. 1-3, pi. 10, figs. 1, 2, pi. 11, figs. 1, 

2; 1961, p. 8-10; 1964b, p. 18, pi. 4, fig. 4), Jasper 

Park in Alberta (Westermann, 1964, p. 405-409, fig. 

2), the northern Richardson Mountains in Yukon

Territory (Frebold and others, 1967, p. 10, 17-20, 

pi. 3, figs. 8a, b), and Wide Bay on the Alaska 

Peninsula (Imlay, 1964, p. B53, pi. 28, figs. 7-9). 

Most of these occurrences have not been dated 

closely because of lack of stratigraphic or faunal 

control. The specimen from Alberta, however, is 

associated with Stemmatoceras, which in Europe 

ranges from the Otoites sauzei zone into the lower 

part of the upper Bajocian and is most common in 

the middle Bajocian. The specimen from the Alaska 

Peninsula was found near the base of a sequence 

containing many ammonites indicative of the Oto-
FAUNAL SETTING

ites sauzei zone (Imlay, 1964, p. B18) and above a 

sequence containing ammonites indicative of the 

Sonninia sowerbyi zone (Westermann, 1969, p. 

17-22).

BATHONIAN AMMONITES

Bathonian ammonites have been collected from 

four different beds or units on Ignek Mesa, as shown 

in table 2. The lowest unit contains crushed fragments of a moderately ribbed species of Cranocephalites. The next higher unit, about 35 feet 

higher, contains many well-preserved but crushed 

specimens of a finely to moderately ribbed new species of Cranocephalites that differs appreciably from 

described species in the arctic region but shows 

considerable resemblance to one specimen from 

southern Alaska (Imlay, 1962a, pi. 1, figs. 9, 11-13). 

The third highest unit contains a finely ribbed species of Arctocephalites identical with a species in 

Canada described as A. elegans Spath by Frebold 

(1961, p. 10; 1964a, p. 3; 1964b, p. 4). The highest 

unit contains immature specimens of Arcticoceras 

that resemble the inner whorls of specimens of A. 

ishmae (Keyserling) that have been found much 

farther east in northeastern Alaska near the Aichilik River.

These ammonite taxa should represent most of 

the arctic Bathonian as defined by Callomon (1959, 

p. 505-512, table 1) for East Greenland. Thus, the 

species of Cranocephalites should correspond, at 

least in part, to the Cranocephalites pompeckji zone 

in East Greenland; the finely ribbed Arctocephalites 

cf. A. elegans Spath, to the Arctocephalites nudus 

zone; and Arcticoceras ishmae (Keyserling), clearly 

to the A. kochi zone. Correlation of these ammonites 

with the Bathonian seems reasonable, but precise 

correlation with its subdivisions must await future 

faunal discoveries.

AMMONITE FAUNAL SETTING

The Bajocian and Bathonian ammonites found in 

northern Alaska belong mostly to the same genera 

and species as those found in northern Canada except for the absence to date of Leioceras and the 

presence of Canavarella and of different species of 

Cranocephalites. In both regions, ammonites of these 

ages are few in numbers: only Arkelloceras represents the middle Bajocian, and no taxon is definitely 

of late Bajocian Age. Evidently the Bajocian and 

Bathonian ammonites of both regions lived in the 

same faunal province.

Bajocian ammonites in northern Alaska as compared with ammonites of that age in southern 

Alaska are much impoverished in numbers of individuals and of genera and species (compare table 

3 herein with lists in Imlay, 1964, p. B11-B30) and 

do not represent nearly as much of Bajocian time. 

Taxa not yet found in southern Alaska include Pseudolioceras maclintocki (Haughton) and Canavarella,. 

Taxa in common with southern Alaska include 

Arkelloceras, Tmetoceras, Erycitoides howetti 

(White), and Pseudolioceras whiteavesi (White). 

Apparently the seas in northern and southern 

Alaska were connected, but conditions in the southern seas were much more favorable for ammonite 

development.

Bathonian ammonites in northern Alaska are 

likewise less numerous and less varied than ammonites of that age in southern Alaska, but these 

differences are not nearly as great as during Bajocian time. Resemblances include a succession of at 

least two species of Cranocephalites followed by a 

finely ribbed species of Arctocephalites similar to 

A. cf. A. elegans Spath. Differences to date with 

southern Alaska include the presence of Arcticoceras and the absence of Kepplerites, Cobbanites, 

Parareineckeia, Macrophylloceras, Holcophylloceras, 

Siemiradzkiat, Xenocephalites, Oecotraustes, and 

Oppelia (Oxycerites).

These differences are too great to be explained 

entirely by collection failure, even should some 

genera now known only in one region be found 

eventually in the other. It seems evident that Bathonian ammonites in southern Alaska lived under 

more favorable conditions than the Bathonian ammonites in northern Alaska but that the seas were 

connected, as shown by the presence of a Cranoceiihalites-Arctocephalites succession in both regions.

Ammonites characteristic of the Boreal realm 

apparently include Kepplerites, Arcticoceras, Arctocephalites, and Cranocephalites, but no proof exists 

that they actually originated in arctic seas. Ammonites characteristic of the Pacific realm include 

Xenocephalites, Cobbanites, and Parareineckeia. 

Most of the other genera listed occur also in the 

Tethyan realm.

GEOGRAPHIC DISTRIBUTION

The geographic occurrences of the Bajocian and 

Bathonian ammonites from northern Alaska described herein are shown in table 3 and figures 3-5. 

Detailed descriptions of the occurrences are given 

in table. 4.
BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

TABLE Geographic 3. distribution of Bajocian Bathonian ammonites and Age northern Alaska in 

looalitiei fossil shown infig. ad 8Bathonian localities Detailed infig. 4. anre Middle positions of Jurassic fossil localities listed under numbrs11. 6

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GEOGRAPHIC DISTRIBUTION

TABLE 4. Description of some Middle Jurassic fossil 

localities in northern Alaska

Locality USGS

No. Mesozoic

(figs. 3, 4) loc. No.

Collector, year of collection, description 

Collector's of locality, and stratigraphic 

field No. assignment

21024 47AGr205

22595 50AGr9

1 South Barrow test well 2, lat 71°15'

51"N., long 156°37' 55"W. Kingak 

Shale at depth of 2,391 ft (717.3 m). 

Early Bajocian.

2 Topagoruk test well 1, lat 70°37'30"N.,

long 155°53'36"W. Kingak Shale at 

depth of 8,113 ft (2433.9m).

3 21552 49ATr352 I. L. Tailleur, 1949. Cutbank on Fortress Creek about 5 miles (8 km) 

south-southeast of Fortress Mountain, 

lat 68°31'N., long 153°03'W. Mediumdark-green fine-grained graywacke 

containing much volcanic material. 

Early Bajocian.

4 22591 50AKe263 A. S. Keller, 1956, Cutbank on Tiglukpuk (Creek, lat 68°20'N., long 

151°50'W. From tuffaceous graywacke. Probably middle Bajocian.

5 21023 47AGr202 George Gryc, 1947. Canning River, west 

(part) bank, opposite mouths of Eagle and 

Cache Creeks, lat 69°23'N., long 146° 

06'W. From base of exposure of 

pyritic black shale that contains 

nodules and lenses of ironstone. Early 

Bajocian and Bathonian. 

George Gryc, 1947. Canning River, west 

bank, lat 69°21'50"N., long 146°01' 

50"W. Black shale containing ironstone beds. Middle Bajocian. 

George Grye, R. W. Imlay, and Allan 

Kover, 1950. Canning River, west 

bank. Same place as USGS Mesozoic 

loc. 21023, but 150 ft (45m) above 

base of exposure. Early Bajocian.

22597 50AGr24 George Grye, R. W. Imlay, and Allan 

Koyer, 1950. Canning River, west 

bank. Same place as USGS Mesozoic 

loc. 21024. Black shale containing 

beds and nodules of ironstone about 

200 ft (60m) below top of exposed 

section. Middle Bajocian.

24033 52AKe37 A. S. Keller, 1952. Cutbank on west 

side of Canning River. Same as USGS 

Mesozoic loc. 21024. Shale and limy 

concretions. Middle Bajocian.

29138 AG861 British Petroleum (Alaska) Inc., 1964. 

West bank of Canning River west of 

Shublik Island, lat 69°24'N., long 

146°10'W. Middle Bajocian.

29139 AG868 British Petroleum (Alaska) Inc., 1964. 

Canning River west of Shublik Island, 

lat 69°24'N., long 146°10'W. Middle 

Bajocian.

29141 AG873 Same data as locality 29139 but about 

500 ft (150m) higher in sequence. 

Middle Bajocian.

29142 AG893 Same data as locality 29139 but about 

3,900 ft (1,170 m) higher in sequence 

above a fault. Middle Bajocian.

British Petroleum (Alaska) Inc., 1964. 

Canning River west of Shublik Island, 

lat 69°24'N., long 146°10'W. Early 

Bajocian.

R. L. Detterman, 1972. Canning River, 

west bank opposite Shublik Island, lat 

69°24'N., long 146°10'W. Siltstone and 

shale with limy concretions. Middle 

Bajocian.

A. S. Keller, 1952. Canning River, cutbank on west side, lat. 69°34'N., long 

146°23'W., Ironstone beds, concretions, 

and shales 1,000 1,500 ft (300-450m) 

below top of Kingak Shale. Early 

Bajocian.

British Petroleum (Alaska) Inc., 1964. 

West end of Ignek Valley near Katakuruk River, lat 69°35'N., long 

145°36'W., Early Bajocian.

7 29153 AG808 British Petroleum (Alaska) Inc., 1964.

Same description as USGS Mesozoic 

loc. 29152. Early Bajocian.

7 29154 AG812 British Petroleum (Alaska) Inc., 1964.

West end of Ignek Valley, lat 69° 

33'N., long 145°43'W. Early Bajocian.

7 29155 AG812A British Petroleum (Alaska) Inc., 1964.

Same description as USGS Mesozoic 

loc. 29154. Early Bajocian.

7 29156 AG812B British Petroleum (Alaska) Inc., 1964.

Same description as USGS loc. 29154. 

Early Bajocian.

29157 AG857

30266 72ADt377

24035 52AKe46

29152 AG807

TABLE 4. Description of some Middle Jurassic fossil 

localities in northern Alaska Continued

Collector, year of collection, description 

of locality, and stratigraphie 

assignment

Locality USGS

No. Mesozoic

(figs. 3, 4) loc. No.

Collector's 

field No.

7 30267 72ADt378 R. L. Detterman, 1972. Head of Ka-

#1 takturuk Canyon in Ignek Valley, lat 

69°35'N., long 145°36'30"W. Fissile 

silty shale containing ironstone concretions, 110 ft (33m) above base of 

Kingak Shale. Early Bajocian. 

7 30268 72ADt378 R. L. Detterman, 1972. Same place as;

#2 USGS Mesozoic loe. 30267, Siltstone

and shale containing ironstone beds,

240 ft (72m) above base of Kingak

Shale. Early Bajocian.

7 30269 72ADt378 R. L. Detterman, 1972. Same place ais

#3 USGS Mesozoic loc. 30267. Siltstone 

and shale containing ironstone beds, 

295 ft (88.5m) above base of Kingak 

Shale. Early Bajocian.

7 30270 72ADt378 R. L. Detterman, 1972. Same place as

#4 USGS Mesozoic loc. 30267. Siltstone 

and shale containing ironstone beds, 

320 ft (96m) above base of Kingak 

Shale. Early Bajocian.

8 29148 AG22 British Petroleum (Alaska) Inc., 1964.

Northwest side of Ignek Mesa in 

central part of Ignek Valley, lat 69° 

34'N., long 145°20"W. Slightly northwest and lower in sequence of Kingak 

Shale than USGS Mesozoic loc. 29143.. 

Early Bajocian.

9 29852 69ADtl44 R. L. Detterman, 1969. Marsh Creek,

4 miles north of Mt. Weller in 

Sadlerochit Mountains, lat 69°41'05" 

N., long 144°50'30"W. About 500 ft 

(150m) above base of Kingak Shale. 

Probably early Bajocian.

10 29150 AG25 British Petroleum (Alaska) Inc., 1964.

At Fire Creek in central part of 

Ignek Valley, lat 69°32'N., loni? 

145°09'W. Early Bajocian.

10 29880 70ADtl67 R. L. Detterman, 1970. Fire Creek, 5.(i

miles (9 km) northwest of junction 

with Sadleroehit River, lat 69°32'20" 

N., long 145°12'30"W. Black fissile 

clay shale containing siltstone beds 

and ironstone concretions. Kingak 

Shale, about 500 ft (150m) above 

base. Early Bajocian.

10 29884 70ARr414 H. N. Reiser, 1970. Kaviak Creek,

#3 about 0.7 (1.12 km) south-southwest 

of confluence with Sadleroehit River 

in Mt. Michelson B-2 quadrangle!, 

lat 69°29'N , long 145°03'W. From 

lower 50 ft (15m) of 150-ft (45-m) 

sequence within the Kingak Shale. 

Early Bajocian. 

10 29886 70ARr414 H. N. Reiser, 1970. Same place as

#1 USGS Mesozoic loc. 29884 but from 

upper 50 (15m) of 150-ft sequence. 

Probably early Bajocian.

10 29887 70ARr240 H. N. Reiser, 1970. East side of Sadlerochit River. High cutbank exposin? 

more than 500 ft (150m) of black 

clay shale and minor amounts of 

silty ironstone beds. NWi/i NWft 

sec. 32, T. 2 N., R. 29 E. (unsurveyed) lat 145°04'25"N., long 69°2fi' 

30"W. Early Bajocian.

11 10307 110 E. de K. Leffingwell, 1911. Sadlerochit

River, cut on north side, probable 

lat 69°33'N., long 144°43'W. In friable black shale containing pyrite 

concretions about 3,000 ft (900m) 

above base of Kingak Shale. Early 

Bajocian.

11 10308 114a E. de K. Leffingwell, 1911. Sadlerochit

River, half a mile up Camp 263 Creek, 

lat 69°33'N., long 144°47'W. Fossils 

from concretions in black shale at 

foot of exposure and probablv ra 

lower 100 ft (30m) of Kingak Shale. 

Early Bajocian.

11 10309 114b E. de K. Lefflngwell, 1911. Sadlerochit

River, north side, about a quarter of 

a mile downstream from Camp 263 

Creek, lat 69°33'N., long 144°46'W., 

about 1,000 ft (300m) above base 

of Kingak Shale. Probably early 

Bajocian.

11 29147 AG 19 British Petroleum (Alaska) Inc., 1964.

At junction of Sadlerochit and Kekiktuk Rivers, lat 69°33'N., long 144° 

43'W. Early Bajocian.

11 29151 AG 538 British Petroleum (Alaska) Inc., 1964.

At junction of Sadlerochit and Kekiktuk Rivers, lat 69°3R'N., Ion:? 

144°43'W. Probably early Bajoeian.
10 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

TABLE 4. Description of some Middle Jurassic fossil 

localities in northern Alaska Continued

Locality USGS

No. Mesozoic Collector's

(figs. 3, 4) loc. No. field No.

Collector, year of collection, description 

of locality, and stratigraphic 

assignment

12

13

14

14

30135 71ADt368

22745 51ADUR4

21023 

(part)

15

16

16

16

16

16

29143

29144

16

16

17

29875

29877

47AGr202

22596 50AGrl8

29146 AG875

29145 AG60

28817 63AMg6

AG24

AG27

29435 66AMg29f

29855 69ADt41A

70ADt215, 

unit 4

70ADt215, 

unit 2

220S3 48AWH132

R. L. Detterman, 1971. On ridge west 

of Okerokovik River, 7.6 miles 

(12.16 km) S. 80°W. of (benchmark) 

VABM ATTE, lat 69°29'45"N., long 

143°26'W. Early Bajocian.

R. L. Detterman, 1951. Cutback on east 

side of Saviukviayak River, lat 

69°00'N., long 148°04'39"W. From 

concretion in hard splintery silty 

shale 160 ft (48 m) above base of 

Kingak Shale.

George Gryc, 1947. Canning River, 

west bank, opposite mouths of Eagle 

and Cache Creek, lat 69°23'N., long 

146°06'W. From base of exposure of 

pyritic black shale that contains 

nodules and lenses of ironstone. Early 

Bajocian and Bathonian.

George Gryc, R. W. Imlay, and Allan 

Kover, 1950. Canning River, west 

side, lat 69°22'10"N., long 146°02'W. 

Black shale containing ironstone 

lenses and nodules, about 2,300 ft 

(690 m) above base of exposed section. Bathonian.

British Petroleum (Alaska) Inc., 1964. 

West side of Canning River, near 

Shublik Island, lat 69°24'N., long 

146°10'W. Bathonian.

British Petroleum (Alaska) Inc., 1964. 

West end of Ignek Valley on northern base of Shublik Mountains, lat 

69°33'N., long 145°50'W. NE1^ sec. 

6, T. 2 N., R. 26 E. (unsurveyed). 

Bathonian.

Marvin Mangus, 1963. Central part of 

Ignek Valley, near middle of sec. 6, 

T. 2 N., R. 28 E. (unsurveyed), west 

end of Isrnek Mesa, lat 69°33'30"N., 

long 145°20'W. Kingak Shale, 200 ft 

(60 m) below base of Ignek Formation. Bathonian.

British Petroleum (Alaska) Inc., 1964. 

Central part of Ignek Valley, near 

west end of north side of Isrnek 

Mesa, lat 69°34'N., long 145°20'W. 

NEM, sec. 6, T. 2 N., R. 28 E. (unsurveyed). Kingak Shale. Bathonian.

British Petroleum (Alaska) Inc., 1964. 

Central part of Ignek Valley. Same 

place as USGS Mesozoic loc. 29143 

near northwest end of Ignek Mesa, 

but slightly higher in Kingak Shale. 

Bathonian.

Marvin Mangus, 1966. Central part of 

Ignek Valley south of Ignek Mesa, 

near USGS Mesozoic loc. 28817. SE^i 

sec. 6, T. 2 N., R. 28 E. (unsurveyed), 

lat 69°33'30"N., long 145°20'W., 

Kingak Shale, about 200 ft (60 m) 

below base of Ignek Formation. 

Bathonian.

R. L. Detterman, 1969. Central part 

of Ignek Valley, 6.5 miles (10.40 km) 

S.75°E. of Katakturuk Canyon at 

northwest end of mesa capped with 

Ignek Formation, lat 69°33'35"N., 

long 145°20'15"W. Near USGS Mesozoic loc. 29143. Kingak Shale, concretions in black clay shale about 

275 ft (82.5 m) below base of Ignek 

Formation. Bathonian.

R. L. Detterman, 1970. Central part 

of Ignek Valley, near USGS Mesozoic 

loc. 29855, lat 69°33'30"N., long 

145°20'W. Siltstone and silty shale 

containing clay ironstone nodules. 

Kingak Shale, about 310-330 ft (93- 

99 m) below base of Ignek Formation. Bathonian.

R. L. Detterman, 1970. Same place as 

USGS Mesozoic loc. 29875. From 

black fissile clay shale containing 

clay ironstone concretions. Kingak 

Shale, 135 ft (40.5 m) below base 

of Ignek Formation and 55 ft (16.5 

m) below Cardioceras at USGS Mesozoic loc. 29856. Bathonian.

C. L. Whittington, 1948. North bank 

of river between Gravel and Fire 

Creeks, lat 69°31'N., long 145°02'W. 

Dull black earthy shale. Bathonian.

TABLE 4. Description of some Middle Jurassic fossil 

localities in northern Alaska Continued

Locality USGS

No. Mesozoic

(figs. 3, 4) loc. No.

Collector, year of collection, description 

Collector's of locality, and stratigraphic 

field No. assignment

18 30075 71ADt330D R. L. Detterman, 1971. Cutbank on

west side of Aichilik River, about 2 

miles (3.2 km) N. 30° E. of VABM 

ATTE on northern front of Brooks 

Range, lat 69°33'N., long 143°05'W., 

Demarcation Point quad. From 1,200- 

1,400 ft (360-420 m) above base of 

Kingak Shale and about 200 ft (60 

m) higher than beds containing 

Amaltheus. Bathonian.

SYSTEMATIC DESCRIPTIONS

Family HILDOCERATIDAE Hyatt, 1867 

Genus TMETOCERAS Buckman, 1891

Tmetoceras sp.

Specimens of Tmetoceras have been found in 

northern Alaska only in the South Barrow test well 

2 at 2,391 feet and the Topagoruk test well 1 at 

8,113 feet (Imlay, 1955, p. 89, pi. 12, figs. 1-10).

Genus PSEUDOLIOCERAS Buckman, 1889 

Pseudolioceras maclintocki (Haughton)

Plate 1, figures 1-5, 7

Ammonites m'clintocki Haughton, 1858, Royal Dublin Soc.

Jour., v. 1, p. 244, pi. 9, figs. 2-4. 

Harpoceras m'clintocki Haughton. Neumayr, 1885, K. Akad.

Wiss. Wien Denkschr., Math.-naturh. Kl., v. 50, p. 85, pi.

1, figs. 5-8. 

Ludwigellal cf. L. rudis (Buckman). Imlay, 1955, U.S. Geol.

Survey Prof. Paper 274-D, pi. 11, figs. 1-3. 

Pseudolioceras whiteavesi (White). Imlay, 1955, U.S. Geol.

Survey Prof. Paper 274-D, p. 89, pi. 12, figs. 15, 16. 

Ludwigia m'clintocki (Haughton). Frebold, 1958, Canada

Geol. Survey Bull. 41, p. 7, pi. 5, figs. 3, 4. 

Pseudolioceras m'clintocki Haughton. Frebold, 1960, Canada

Geol. Survey Bull. 59, p. 20, pi. 8, pi. 9, figs. 2-4. 

Pseudolioceras m'clintocki Haughton. Frebold, 1964a, Canada

Geol. Survey Paper 63-4, p. 5, pi. 10, figs. 4a-8b, 9. 

Pseudo'lioceras m'clintocki (Haughton). Westermann, 1964,

Bulls. Am. Paleontology, v. 47, no. 216, p. 422-424. 

Pseudolioceras m'clintocki (Haughton). Dagis and Dagis,

1967, Akad. Nauk SSSR, Sibirskoye Otdel., Inst. Geologii

i Geofiziki, p. 56-58, pi. 3, figs, la, b. 

Pseudolioceras m'clintocki (Haughton). Westermann, 1969,

Bulls. Am. Paleontology, v. 47, no. 216, p. 52.

Pseudolioceras maclintocki (Haughton) is represented in northern Alaska by 50 specimens which 

show the same range of variation in rib coarseness 

and curvature described by Frebold (1960, p. 20) 

for specimens from northernmost Canada. These 

Alaska specimens are preserved in dark-gray to 

black claystone or in silty claystone; most have been 

crushed laterally, and none shows the complete adult 

body chamber. The species is characterized by a 

highly compressed involute shell, flattened flanks 

that converge gradually to the venter, a high hollow 

keel, a very steep umbilical wall that rounds
160° 156°

SYSTEMATIC DESCRIPTIONS

152° 148°

11

140°

68

50 0 50 100 150 MILES

 

50 0 50 100 150 KILOMETRES

FIGURE 3. Generalized index map of Bajocian ammonite localities in northern Alaska.

abruptly or sharply into the flanks, and variably 

weak to strong falcate ribs that become stronger 

ventrally but fade out before reaching the keel.

r?/pes. Hypotypes, USNM 192125-192130.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 21023, 22595, 24035, 30135, 29152, and 29157. 

The species is possibly represented also at USGS 

Mesozoic Iocs. 10307, 29880, and 29887. It is associated with Oxytoma jacksoni (Pompeckj) at USGS 

Mesozoic loc. 24035 and with Inoceramus lucifer 

Eichwald at USGS Mesozoic loc. 21023. In northernmost Canada, O. jacksoni has been found with, and 

a little below, Pseudolioceras maclintocki (Haughton) (Frebold, 1960, p. 28).

Pseudolioceras whiteavesi (White) 

Plate 1, figures 16-18

Ammonites (Amaltheus) whiteavesi White, 1889, U.S. Geol.

Survey Bull. 51, p. 69-90, pi. 13, figs. 1-5. 

Harpoceras whiteavesi (White). Kellum, Daviess, and Swinney, 1945, U.S. Geol. Survey Prelim. Kept, on geology and

oil possibilities of the southwestern part of the Wide Bay

anticline, figs. 4e, f.

Not Pseudolioceras whiteavesi (White). Imlay, 1955, U..S. 

Geol. Survey Prof. Paper 274-D, p. 89, pi. 12, figs. 15, 16.

Pseudolioceras m'clintocki whiteavesi (White). Westermann, 

1964, Bulls. Am. Paleontology, v. 47, p. 421-425, pi. 68, 

fig. 2, pi. 69, figs. 1-6, pi. 70, figs. 1-5, pi. 71, figs. 1, 2, 

text-figs. 30, 31.

Turgites whiteavesi (White). Kalacheva and Sey, 1970, 

Akad. Nauk SSSR Doklady, v. 193, no. 2, p. 450-451, pi. 

1, figs. 1-3.

This species, represented in northern Alaska by 

only four specimens, differs from P. maclintocki 

(Haughton) solely by having a narrow raised umbilical edge (Frebold, 1960, p. 21; Westermann, 

1964, p. 423). Associated mollusks include Inoceramus lucifer Eichwald and Canavarella crassifalcaia 

Imlay, n. sp.

ZVpes. Hypotypes, USNM 192131-192133.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 10307, 21023, 29147 and 29884. The species is 

associated with Inoceramus lucifer Eichwald at 

USGS Mesozoic Iocs. 10307 and 21023.
12

160°

BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

156° 152° 148° 144° 140°

50 0 50 

I

100 

I

150MILES

50 0 50 100 150 KILOMETRES

FIGURE 4. Generalized index map of Bathonian ammonite localities in northern Alaska.

Family GRAPHOCERATIDAE Buckman, 1905 

Genus CANAVARELLA Buckman, 1904

Canavarella crassifalcata Itnlay, n. sp. 

Plate 1, figures 6, 8-14

The species is represented by 25 laterally compressed internal molds that show various growth 

stages. It is characterized by a moderately involute, 

compressed shell; gently rounded flanks that pass 

gradually into the umbilical slope and the venter; a 

low keel; and strong simple falcate ribs. These ribs 

begin at the umbilical seam, become stronger ventrally, are strongest on the ventral margin, and 

then fade out before reaching the keel. Fairly strong 

falcate ribbing is visible on some specimens at diameters of only 8-10 mm. The body chamber is not 

completely preserved but occupies at least half a 

whorl.

Meaningful measurement cannot be made because 

of deformation. The suture line is simple, has 

broader saddles than lobes, and its auxiliaries ascend to the umbilical seam.

This species of Canavarella from northern 

Alaska is similar in appearance to C. belophora 

Buckman (1904, Supp. p. CXXIX, pi. 22, figs. 22- 

24) from England, but has much stouter ribs on its 

body chamber and slightly broader saddles.

Canavarella differs from Pseudolioceras, with 

which it is associated in Alaska, by having a wider 

umbilicus, stronger ribs on its inner whorls, and 

more falcate ribs that project forward more 

strongly on the venter.

Types. Holotype, USNM 192134; paratypes, 

USNM 192135-192140.

Occurrences. Kingak Shale, USGS Mesozoic Iocs. 

29147, 29153-29156, 29884, and 30267-30270. The 

species ranges from 110 to 320 feet above the base 

of the Kingak Shale exposed near the head of 

Katakturuk Canyon in the western part of Ignek 

Valley. In that sequence it is associated throughout 

with Inoccramns lucifer Eichwald and locally with 

Erycitoides (Mesozoic loc. 29153).
SYSTEMATIC DESCRIPTIONS 13

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Cvl Cvl

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14 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

Family HAMMATOCERATIDAE Buckman, 1887 

Genns ERYCITOIDES Westermann, 1964

Erycitoides cf. E. howelli (White) 

Plate 3, figures 5, 6, 10

Erycitoides is definitely represented in northern 

Alaska by five fragments of outer septate whorls. Of 

these, the best preserved has been illustrated previously as E. howelli (White) Imlay, 1955, pi. 13, 

figs. 12, 13) because it closely resembles comparablesized specimens of that species from the Alaska 

Peninsula (White, 1889, pi. 12, figs. 1, 2, pi. 14, figs. 

1-3; Westermann, 1964, pis. 44-57). The other four 

specimens are more fragmentary and are, therefore, 

only compared herein with that species. One of 

these (pi. 3, figs. 5, 6) appears to be a typical representative of the species. The other (pi. 3, fig. 10) 

has long weak primary ribs and closely spaced secondary ribs as in a specimen figured by Westermann 

(1964, pi. 58, fig. 1).

Figured specimens. USNM 192141, 180730.

Occurrences. Kingak Shale at USGS Mesozoic 

loc. 10308. The species is probably represented also 

at Mesozoic Iocs. 29150, 29153, and 29880.

Family OPPELHDAE Bonarelli, 1894

Genus OPPEL1A Waagen, 1869 

Subgenus L1ROXY1TES Imlay, 1961

Oppelia (Liroxyites) n. sp. undet. 

Plate 1, figure 15

The subgenus is represented by one laterally compressed internal mold that bears some shelly material and represents an adult body whorl. It has a 

discoidal, highly involute compressed shell; a fairly 

sharp keel that is pinched basally; a body chamber 

that occupies about three-fifths of a whorl; an aperture that terminates abruptly in a forwardly inclined falcoid curve; falcoid ribs that arise near the 

middle of the flanks, are fairly strong on the last 

septate whorl, become lower and broader adorally, 

and persist almost to the aperture; fine f alcoid 

striae that cover the entire surface; and a faint 

spiral band that occurs at about three-fifths of the 

height of the whorl.

The preservation of the specimen is not sufficient 

to make accurate measurements or to trace the suture line. This species differs from O. (Liroxyites) 

kellumi Imlay (1962b, p. A8, pi. 2) in having somewhat coarser ribbing on its body chamber and much 

coarser ribbing on the septate part of its body 

whorl. In this respect it shows more resemblance to 

a specimen from Canada described by Frebold 

(1957, p. 54, pi. 28, fig. 2) as Oppelia (Oxycerites) 

ex. gr. fallax Gueranger.

Figured specimen. USNM 192142.

Occurrence. Kingak Shale at USGS Mesozoic 

loc. 29435 in association with Cranocephalites and 

rare Arctocephalites.

Family STEPHANOCERATIDAE Neumayr, 1875 

Genus ARKELLOCERAS Frebold, 1957

Arkelloceras cf. A. maclearni Frebold 

Plate 1, figures 21-26

Reineckeia (Reineckeites) cf. R. (R.) stuebeli Steinmann.

Imlay, 1955, U.S. Geol. Survey Prof. Paper 274-D, p. 91,

pi. 13, figs. 1-7.

This species, represented by 46 laterally crushed 

specimens from the banks of the Canning River, is 

nearly identical in side view with described species 

of that genus from northern Canada. Some finely 

ribbed specimens match very well in side view with 

A. tozeri Frebold (1958, p. 10, pi. 9, figs, la-d, 2a, 

b, 3a, b; pi. 10, figs, la-c, 2a, b; pi. 11, figs, la-c, 

2a, b; 1961, p. 8, pi. 3, fig. 1, pi. 4, figs. 1, 2a, b, 

pi 5, figs, la-c) and with A. elegans Frebold, in 

Frebold, Mountjoy, and Templeman-Kluit (1967, p. 

17. pi. 3, figs. 8a, b). Other coarsely ribbed specimens match closely in side view with A. maclearni 

Frebold (1958, p. 11, pi, 12, figs, la-c, 2a-g, 3a-c, 

pi. 13, figs, la-d, 2a-c, 3a, b; 1961, p. 8, pi. 4, figs. 

3a, b). As these specimens occur in the same collections and are associated with others bearing ribbing 

of intermediate coarseness, all are herein considered 

to represent a single species. On the whole they resemble A. maclearni more than A. tozeri in coiling, 

coarseness of ribbing, and in the presence of swelling or tubercles at the ventral ends of the primary 

ribs.

Definite identification of this species with any of 

the described species of Arkelloceras from Canada 

will not be possible until specimens are found that 

show the characteristics of the venter. A venter 

similar to that on Arkelloceras (Frebold, 1958, p. 9) 

is suggested, however, by the fact that the ribs on 

several small specimens pass ventrally into weak 

tubercles or into laterally compressed swellings.

One feature that may differentiate the species of 

Arkelloceras found near the Canning River, Alaska, 

from those found in northern Canada is the presence of lateral tubercles on the small septate whorls 

of the coarsely ribbed Alaskan specimens. These 

tubercles are conical on the innermost septate 

whorls, become radially elongate and weaker dorsally, and are absent at diameters greater than about 

50 mm. In contrast, on the described specimens 

from Canada, only slight or moderate swellings at 

the ventral ends of the primary ribs were reported 

by Frebold (1958, p. 12, pi. 12, figs. 2a, g; Frebold 

and others, 1967, p. 18, pi. 3, fig. 8a).
SYSTEMATIC DESCRIPTIONS 15

The present assignment of the specimens under 

discussion to Arkelloceras instead of Reineckeia 

(Reineckeites) is based on the lack of constrictions 

and on the presence of tubercles on the venters of 

several small specimens. The alternate arrangement 

of ribs on the venters of small specimens of Arkelloceras, as described by Frebold (1958, p. 9), is 

quite different from the arrangement on the venter 

of Reineckeia (Reineckeites) .

The presence of Arkelloceras implies an early 

middle Bajocian Age (Frebold, in Frebold and 

others, 1967, p. 20), which is in accord with its 

stratigraphic position above Pseudolioceras on the 

Canning River (fig. 1).

Figured specimens. USNM 192143-192148.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 21024, 22597, 24033, 29138, 29139, 29141, 

29142, and 30266.

Arkelloceras? sp. juv.

Plate 1, figures 19, 20

One small external mold shows one flank and part 

of the venter of a small immature ammonite. Its 

primary ribs are strong, trend radially and terminate ventrally in weak tubercles or swellings a little 

below the middle of the flanks. From the swellings 

pass pairs of slightly weaker secondary ribs, some 

of which are weakly connected with the primary 

ribs. All secondary ribs become fairly strong ventrally and then weaken abruptly along the margin 

of the venter. The midventral area is apparently 

nearly smooth.

The characteristics of this specimen suggest that 

it may be an immature form of Arkelloceras Frebold (1958, p. 9). It resembles the inner whorls of 

A. maclearni Frebold (1958, p. 11, pi. 12, figs. 2dg, 3a, b) rather than those of A. tozeri Frebold 

(1958, p. 10, pi. 9, figs. Ib, c, 3a) in having fairly 

strong primary ribs that terminate ventrally in 

swellings or tubercles. It also resembles A. elegans 

Frebold in Frebold, Mountjoy, and TempelmanKluit (1967, p. 17-20, pi. 3, figs. 8a, b) in strength 

of ribbing and in that its ribs fork below the middle of the flanks.

Figured specimen. USNM 192149.

Occurrence. Kingak Shale at USGS Mesozoic 

loc. 22591.

Family CARDIOCERATIDAE Siemiradzki, 1891 

Genus CRANOCEPHALITES Spath, 1932

Cranocephalites ignekensis Imlay, n. sp.

Plate 2, figures 1-9, 11, 12

This species is represented in collections from the 

central part of Ignek Valley by 22 internal and external molds, most of which are laterally compressed. It is characterized by a very small umbilicus on septate whorls, a contracted body chamber 

that occupies nearly three-fourths of a whorl, a 

fairly deep apertural constriction that inclines forward and is bordered adorally by a swelling, and 

distinct forwardly inclined ribs that become 

stronger adorally and persist to the apertural constriction without fading.

These ribs vary considerably in strength and 

density, incline adapically on the umbilical wall, incline adorally on the flanks, cross the venter transversely or with a gentle forward arching, and generally bifurcate at one-fourth to one-third the height 

of the flanks. Some primary ribs remain simple, and 

some secondary ribs arise freely a little below the 

middle of the flanks. The primary ribs are higher 

and sharper than the secondary ribs along the furcation zone. The secondary ribs, however, become 

broader and higher ventrally and adorally, are 

strongest on the venter, and near the aperture are 

wider than the interspaces on some specimens. 

Among the 22 specimens available, five have ribs 

that are fine and fairly closely spaced, five have ribs 

that are coarse and fairly widely spaced, and 14 

have ribs that are intermediate or moderate in 

coarseness and spacing.

The suture line has broad saddles and fairly short 

lobes, and its auxiliaries ascend toward the umbilical seam.

Meaningful measurements cannot be made because all specimens are deformed or crushed.

These specimens, in spite of appreciable differences in coarseness of ribbing, are herein considered 

to represent a single species because all three variants occur together at two localities (USGS Mesozoic Iocs. 28817 and 29143), two variants occur 

together at two other localities (USGS Mesozoic 

Iocs. 29435 and 29885), and both finely and moderately ribbed variants occur on opposite sides of a 

single slab (pi. 2, figs. 1, 7).

The most coarsely ribbed specimens (pi. 2, figs. 

11, 12) of Cranocephalites ignekensis Imlay, n. sp., 

show some resemblance to C. pompeckji (Madsen) 

(1904, p. 189, pi. 8, figs. 5, 6; Spath, 1932, p. 16, 

pi. 4, figs. 9a, b, 10, pi. 5, figs. 6a, 7, pi. 13, figs, la, 

b; Donovan, 1953, pi. 17, figs. 2, 3) except for having slightly broader ribs on their septate whorls, 

appreciably broader ribs on their body chambers, 

and a deeper apertural constriction. The moderately 

ribbed specimen (pi. 2, figs. 5-7, 9) has ribs that 

are much finer than on any described specimen of 

C. pompeckji (Madsen) but are similar to those on
16 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

one septate specimen of C. vulgaris Spath (1932, pi. 

4, figs. 3a, b) from East Greenland. The typical 

finely ribbed specimens (pi. 2, figs. 1-4) likewise 

resemble a Greenland variant of C. vulgaris Spath 

(1932, pi. 4, fig. 1) in fineness and density of ribbing 

on their septate whorls. All three variants from 

northern Alaska differ markedly from C. vulgaris 

in retaining distinct ribbing on all parts of the adult 

body whorl and in having stronger ribbing on the 

venter than on the flanks of the body whorl.

The moderate to coarsely ribbed variants of C. 

ignekensis Imlay, n. sp., also resemble a certain 

specimen of Cranocephalites from southern Alaska 

(Imlay, 1962a, pi. 1, figs. 9, 11-13) except that they 

attain a smaller adult size and have a more complicated suture line. They could represent the same 

species.

Type. Holotype, USNM 192151; paratypes, 

USNM 192152-192160.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 28817, 29143, 29435, and 29855. These were 

collected 200-275 feet below the top of the formation in the central part of Ignek Valley. The highest 

occurrences (Mesozoic Iocs. 29143, 29435) also contain Arctocephalites that are undeformed, whereas 

all the specimens of Cranocephalites are deformed 

or crushed.

Genus ARCTOCEPHALITES Spath, 1928

Arctocephalites cf. A. elegans Spath

Plate 4, figures 1-8

cf. Arctocephalites elegans Spath, 1932, Medd. Gr0nland, v.

87, no. 7, p. 37, pi. 10, figs. 4a, b. 

Arctocephalites elegans Spath. Frebold, 1961, Canada Geol.

Survey Bull. 74, p. 10, pi. 9, fig. 1, pi. 10, figs. 1, 2; pi. 11,

figs. 1-4. 

Arctocephalites elegans Spath. Frebold, 1964b, Canada Geol.

Survey Bull. 119, p. 3, pi. 1, figs. 1-3, pi. 2, figs. 1, 2. 

Arctocephalites elegans Spath. Frebold, 1964a, Canada Geol.

Survey Paper 63-4, p. 4, pi. 23, figs. 1, 2, 4. 

lArctocephalites aff. A. elegans Spath. Efimova and others,

1968, Polevoy atlas Yurshoy fauny i flory Severe-Vostoka

SSSR, p. 125, pi. 94, figs, la, b, 2a-c.

This species in northern Alaska is represented by 

seven specimens that closely re&emble and show the 

same range of variation as the specimens of A. elegans Spath described by Frebold (1961, p. 10; 

1964b, p. 3) from the Arctic region of Canada. One 

finely ribbed specimen (pi. 4, figs. 1-3) is nearly 

identical in ribbing with one Canadian specimen 

(Frebold, 1961, pi. 11, figs, la, b). The other six 

specimens from northern Alaska bear slightly 

coarser ribbing, similar to that on several Canadian 

specimens (Frebold, 1961, pi. 10, figs. 1, la, pi. 11, 

figs. 2, 3; 1964b, pi. 1, figs, la, b, 2a, b).

All these specimens from the Arctic region of 

Alaska are characterized by a medium size for the 

genus, a moderately compressed shell, a very narrow umbilicus, and sharp forwardly inclined ribs 

that bifurcate or trifurcate below the middle of the 

flanks and cross the venter nearly transversely. 

Also, in all specimens the adult body chamber becomes abruptly smooth or nearly smooth near its 

adapical end and then terminates adorally in a pronounced forwardly inclined constriction.

Assignment of these finely ribbed specimens to 

Arctocephalites elegans Spath seems reasonable 

when comparison is made with the monotypic holotype from East Greenland (Spath, 1932, pi. 10, figs. 

4a, b). Nonetheless, the validity of that assignment 

must await studies showing the range of variation 

within the species of Arctocephalites in Greenland. 

The possibility that A. elegans Spath may be a variant of some earlier named species is suggested by 

the fact that it was obtained from the same locality 

(Spath, 1932, p. 135) and ammonite zone (Callomon, 1959, p. 508) as several other described species 

of the genus.

Figured specimens. USNM. 192160-192162.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 29143, 29144, 29145, 29146, and 29435.

Arctocephalites cf. A. arcticus (Newton and Teall)

Plate 4, figure 10

One compressed fragment bears sharp fairly 

sparse ribbing like that on the outermost septate 

whorl of A. arcticus (Newton and Teall, 1897, pi. 

40, figs, la, b; Whitfield, 1906, pi. 18, fig. 2; Spath, 

1932, pi. 12, fig. 2). Its ribbing appears to be a 

little weaker and less sparse than that on A. pilaeformis Spath (1932, p. 33; Newton and Teall, 1897, 

pi. 40, figs. 2, 2a) and A. callomoni Frebold (1964b, 

pi. 5, fig. 3, pi. 7, fig. 3).

Figured specimen. USNM 192163.

Occurrence. Kingak Shale at USGS Mesozoic 

loc. 29146.

Genus ARCTICOCERAS Spath, 1924 

Arcticoceras ishmae (Keyserling) 

Plate 3, figures 7-9, 11-22

Ammonites ishmae Keyserling, 1846, Wissenschaftliche Beobachtungen auf einer Reise in das Petschora-Land im 

Jahre 1843, p. 331, pi. 20, figs. 8-10.

Macrocephalites ishmae Keyserling. Sokolov, 1912, Com. 

geol. St. Petersbourg Mem., new ser., v. 76, p. 15, 49, pi. 

1, fig. 1, pi. 3, fig. 12. 

Arcticoceras ishmae (Keyserling). Spath, 1932, Medd. Gr0nland, v. 87, no. 7, p. 50, pi. 15, figs. 7a, b. 

Arcticoceras sp. Imlay, 1955, U.S. Geol. Survey Prof. 

Paper 274-D, p. 90, pi. 12, figs. 11, 19.
SYSTEMATIC DESCRIPTIONS 17

Arcticoceras kochi Spath, 1932, Medd. Gr0nland, v. 87, no. 

7, p. 53-56, pi. 12, fig. 1, pi. 13, fig-s. 4, 5, pi. 14, figs. 1-3, 

pi. 15, figs. 1, 4-6.

Arcticoceras kochi Spath. Frebold, 1961, Canada Geol. Survey Bull. 74, p. 16, pi. 9, fig. 3, pi. 12, figs, la, b, pi. 13, 

figs. 4, 5, pi. 14, figs. 1-3, pi. 15, figs 1, 4-6.

Arcticoceras ishmae Keyserling. Frebold, 1961, Canada Geol. 

Survey Bull. 74, pi. 10, fig. 3, pi. 13, figs, la, b, pi. 14, figs. 

1, 3a, b.

Arcticoceras kochi Spath. Frebold, 1964a, Canada Geol. Survey Bull. 63-4, pi. 25, figs. 1, 2.

This species is represented by 22 specimens, of 

which 18 are from USGS Mesozoic locality 30075. 

Most of them are small and septate, and only one 

(Imlay, 1955, pi. 12, fig. 19) represents an adult 

body chamber. Among the septate specimens, six 

have fine closely spaced ribs (pi. 3, figs. 7-9, 11, 

12), eight have coarse broadly spaced ribs (pi. 3, 

figs. 19-22), and seven have ribs of intermediate 

coarseness and spacing (pi. 3, figs. 13-18). The ribs 

are sharp, trend radially or incline slightly backward on the umbilical wall, incline forward on the 

flanks, and project strongly forward on the venter. 

Most ribs bifurcate near or below the middle of the 

flanks, but some ribs remain simple and are separated by short ribs that arise near the middle of the 

flanks. The venter is narrowly arched on most of the 

septate specimens and apparently becomes less so 

during growth, except on the smallest whorls.

In comparisons with Arcticoceras in East Greenland, the finely ribbed variant from northern Alaska 

is similar to specimens that Spath (1932, p. 55, pi. 

14, figs. 2, 3, pi. 15, fig. 6) considered to be a variant 

of A. kochi Spath and named pseudolamberti. The 

moderately ribbed variant from Alaska greatly resembles certain Greenland specimens described as 

A. aff. A. kochi Spath (1932, p. 55, pi. 15, figs. 4a, 

b, 5). The most coarsely ribbed variant from Alaska 

bears ribbing comparable with that on the adapical 

part of the outer whorl of the holotype of A. kochi 

Spath (1932, pi. 15, fig. 1). In addition, the nearly 

smooth body chamber of one Alaska specimen (Imlay, 1955, pi. 12, fig. 19) resembles that of an adult 

of A. kochi Spath (1932, pi. 14, fig. 1) which that 

author suggested belonged to the variant pseudolamb erti.

The moderately ribbed variant from Alaska also 

resembles A. ishmae (Keyserling) (1846, p. 331, pi. 

20, figs. 8-10; Sokolov, 1912, p. 17, 49, pi. 1, fig. 1; 

Spath, 1932, pi. 15, figs. 7a, b) from Petchora-Land 

as well as ammonites from northern Canada that 

are assigned to that species by Frebold (1961, pi. 

10, fig. 3, pi. 13, figs, la, b, pi. 15, figs. 3a, b).

In summation, the specimens of Arcticoceras described herein show the same rib characteristics and

variations as A. kochi Spath from East Greenland 

but also closely resemble A. ishmae (Keyserling) 

from Petchora-Land and Canada. This agrees with 

the observations of John Callomon (written commun., 1972) that in East Greenland the topotypes of 

A. kochi Spath occur in the same bed as A. ishmae 

(Keyserling) and are within the range of variation 

of that species.

Hypotypes. USNM 192164-192176.

Occurrences. Kingak Shale at USGS Mesozoic 

Iocs. 21023, 22596, and 30075. The specimen of 

Arcticoceras from loc. 21023 is considered to be 

float because it is preserved in a hard brown siltstone, whereas most of the other specimens from 

that locality are preserved in a softer black shale 

and consist mostly of Pseudolioceras maclintocki 

(Haughton) and Inoceramus lucifer Eichwald of 

early Bajocian Age (Imlay, 1955, p. 80, 86).

Arcticoceras sp. juv. 

Plate 3, figures 1, 2

Two immature specimens of Arcticoceras from Ignek Mesa (see table 2) have ribbing and a sharpened venter identical with those on immature specimens of the moderately ribbed variant of Arcticoceras ishmae (Keyserling) as just described. These 

specimens also resemble an even smaller ammonite 

(pi. 3, figs. 3, 4) from the Saviukviayak River. That 

ammonite was once described as Pseudocadoceras 

grewingki (Pompeckj) because of its resemblance 

to immature specimens of that species in southern 

Alaska (Imlay, 1955, p. 90, pi. 12, fig. 1). It now 

appears, however, that small immature specimens of 

Pseudocadoceras and Arcticoceras are very much 

alike, a resemblance which was discussed by Spath 

(1932, p. 57) and confirmed by John Callomon 

(written commun., 1972). In contrast, adult specimens of Pseudocadoceras differ from adult specimens of Arcticoceras in the following ways: (1) 

they are much smaller and more evolute; (2) their 

ribs project forward less strongly on the venter; 

and (3) the adult body whorl remains strongly 

ribbed instead of becoming smooth.

The specimen in question from the Saviukviayak 

River probably belongs to Arcticoceras rather than 

Pseudocadoceras, but its certain generic identification will have to await the discovery of larger specimens. The specimens from Ignek Mesa, however, 

are large enough for their assignment to Arcticoceras to be certain.

These identifications, plus the reassignment to 

Arkelloceras of ammonites formerly identified as 

Reineckeia (Reineckeites) (Imlay, 1955, p. 91, pi.
18 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

13, figs. 1-7), show that the Callovian is poorly represented in northern Alaska. The only positive evidence consists of one worn Cadoceras found as float 

(USGS Mesozoic loc. 30136) near the Aichilik 

River in extreme northeastern Alaska.

Figured specimens. USNM 180732, 108781.

Occurrences. Kingak Shale at USGS Mesozoic 

loc. 29877 on Ignek Mesa. The genus is probably 

present at Mesozoic loc. 22745 on the Saviukviayak 

River.

Family PERISPHINCTIDAE Steinmann, 1890 

Genus CHOFFATIA Siemeradzki, 1898

Choffatia? sp. 

Plate 2, figure 10; plate 4, figures 9, 11

One internal mold shows parts of three corroded 

septate whorls of a perisphinctid ammonite. The 

outermost whorl is represented only by a small fragment, but its umbilical imprint is preserved slightly 

below the middle of the next smaller whorl. That 

whorl is subovate near its adoral end, has a whorl 

height of 31 mm, a whorl thickness of 24 mm, and 

an umbilical width of 39 mm. Its primary ribs trend 

radially, are widely spaced, are swollen near the 

umbilicus, and fade out ventrally below the middle 

of the flanks. Its secondary ribs are faint, closely 

spaced, arise near the middle of the flanks, incline 

slightly forward, cross the venter transversely 

where they become slightly stronger, and outnumber the primary ribs about 6 to 1. The next smaller 

whorl, as exposed in the umbilicus, has weak broad 

rather widely spaced primary ribs. Corrosion accounts in part for the weakness of the primary ribs.

This species is assigned to Choffatia rather than 

to Procerites because of its fairly evolute coiling 

and because its primary ribs are widely spaced and 

are swollen near the umbilicus. Its rib pattern is 

essentially the same as in Choffatia sakuntata Spath 

(1931, p. 351, pi. 68, figs. 4a, b) from India except 

for having shorter and less sharply defined primary 

ribs. C. balinensis (Neumayr) (Waagen, 1875, p. 

163, pi. 45, figs. 2a, b; Spath, 1931, p. 348, pi. 48, 

figs. 5a, b) is also similar but has even sharper primary ribs. These differences may in part reflect the 

poor preservation of the Alaskan specimen.

Figured specimen. USNM 180733.

Occurrence. Kingak Shale at USGS Mesozoic 

loc. 30075 in association with Arcticoceras.

REFERENCES CITED

Arkell, W. J., 1950-58, Monograph of the English Bathonian 

ammonites: London, Palaeontographical Soc., 8 v., 33 

pis., 83 figs.

Arkell, W. J., and others, 1957, Mesozoic Ammonidea, in

Moore, R. C., ed., Treatise on invertebrate paleontology, 

Part L, Mollusca 4, Cephalopoda, Ammonoidea: New 

York and Lawrence, Kans., Geol. Soc. America and 

Univ. Kansas Press, p. L80-L437.

Buckman, S. S., 1887-1907, Monograph of the ammonites of 

the Inferior Oolite Series: London, Palaeontographical 

Soc., 456 p., 103 pis. (1887-1894); Supplement, 262 p., 

24 pis. (1898-1907).

Callomon, J. H., 1959, The ammonite zones of the Middle 

Jurassic beds of East Greenland: Geol. Mag., v. 96, no. 

6, p. 505-513, pis. 17, 18.

Dagis, A. A., and Dagis, A. S., 1967, Stratigrafiya Toarskikh 

otlozheniy Vilyuyskoy sineklizy [Stratigraphy of Toarsk 

deposits from the Vilyuysk syncline], in Saks, V. N., 

ed., Problemy paleontologicheskogo obosnovaniya detal'- 

noy stratigrafii Mezozoya Sibiri i Dal'nego Vostoka 

[Problems of paleontological criteria for the detailed 

Mesozoic stratigraphy of Siberia and the Far East] : 

Leningrad, Akad. Nauk SSSR, Sibirskoye Otdel., Inst. 

Geologii i Geofiziki, p. 41-60, pis. 1, 2.

Detterman, R. L., and Hartsock, J. K., 1966, Geology of the 

Iniskin-Tuxedni region, Alaska: U.S. Geol. Survey Prof. 

Paper 512, 78 p., 6 pis., 7 figs.

Donovan, D. T., 1953, The Jurassic and Cretaceous stratigraphy and paleontology of Traill 0, East Greenland: 

Medd. Gr0nland, v. Ill, no. 4, 150 p., 25 pis., 14 figs.

Efimova, A. F., Kinasov, V. P., Parakestov, K. V., Polubatko, 

I. V., Repin, Yu. S., and Dagis, A. S., 1968, Polevoy 

atlas Yurskoy fauny i flory Severe-Vostoka SSSR [Field 

atlas of Jurassic fauna and flora from northeast 

USSR] : Magadan, Knigoizdat, 382 p., 114 pis., 12 figs.

Frebold, Hans, 1957, The Jurassic Fernie group in the 

Canadian Rocky Mountains and foothills: Canada Geol. 

Survey Mem. 287, 197 p., 44 pis., 5 figs.

 1958, Fauna, age and correlation of the Jurassic 

rocks of Prince Patrick Island: Canada Geol. Survey 

Bull. 41, 69 p., 18 pis. 1 fig.

 1960, The Jurassic faunas of the Canadian Arctic 

Lower Jurassic and lowermost Middle Jurassic ammonites: Canada Geol. Survey Bull. 59, 33 p., 15 pis., 8 figs.

 1961, The Jurassic faunas of the Canadian Arctic 

Middle and Upper Jurassic ammonites: Canada Geol. 

Survey Bull. 74, 43 p., 21 pis., 3 figs.

 1964a, Illustrations of Canadian fossils Jurassic of 

western and Arctic Canada: Canada Geol. Survey Paper 

63-4, 107 p., 51 pis.

1964b, The Jurassic faunas of the Canadian Arctic 

Cadoceratinae: Canada Geol. Survey Bull. 119, 27 p., 

20 pis., 1 fig.

Frebold, Hans, Mountjoy, E. W., and Templeman-Kluit, 

D. J., 1967, New occurrences of Jurassic rocks and fossils in central and northern Yukon Territory: Canada 

Geol. Survey Paper 67-12, 35 p., 3 pis., 2 figs.

Grantz, Arthur, Thomas, Herman, Stern, T. W., and Sheffey, 

N. B., 1963, Potassium-argon and lead-alpha ages for 

stratigraphically bracketed plutonic rocks in the Talkeetna Mountains, Alaska: U.S. Geol. Survey Prof. 

Paper 475-B, p. B56-B59.

Haughton, Samuel, 1858, [Geological notes and illustrations 

in M'Clintock's reminiscences of Arctic ice travel]: 

Royal Dublin Soc., Jour., v. 1, p. 183-250, illus., map.
REFERENCES CITED 19

Imlay, R. W., 1955, Characteristic Jurassic mollusks from 

northern Alaska: U.S. Geol. Survey Prof. Paper 274-D, 

p. 69-96, pis. 8-13, 1 fig.

 1962a, Jurassic (Bathonian or early Callovian) ammonites from Alaska and Montana: U.S. Geol. Survey 

Prof. Paper 374-C, 32 p., 8 pis., 7 figs.

 1962b, Late Bajocian ammonites from the Cook Inlet 

region, Alaska: U.S. Geol. Survey Prof. Paper 418-A, 

15 p., 5 pis., 4 figs.

 1964, Middle Bajocian ammonites from the Cook

Inlet region, Alaska: U.S. Geol. Survey Prof. Paper

418-B, 61 p., 29 pis., 5 figs. 

Imlay, R. W., and Detterman, R. L., 1973, Jurassic paleobiogeography of Alaska: U.S. Geol. Survey Prof. Paper

801, 32 p., 15 figs. 

Kalacheva, E. D., and Sey, I. L, 1970, Tugurites novyy

pozdneaalenskiy Severotikhookeanskiy rod [Tugurites 

a new late Aalenian genus from the North Pacific

Ocean]: Akad. Nauk SSSR Doklady, v. 193, no. 2, p.

449-452, pi. 1. 

Kellum, L. B., Daviess, S. N., and Swinney, C. M., [1945?],

Geology and oil possibilities of the southwestern part

of the Wide Bay anticline, Alaska: U.S. Geol. Survey

17 p., 9 pis. 

Keyserling, Alexander, 1846, Wissenschaftliche Beobachtungen auf einer Reise in das Petschora-Land im Jahre

1843: St. Petersburg, Carl Krey, 465 p.

Madsen, Victor, 1904, On Jurassic fossils from East Greenland : Medd. Gr0nland, v. 29, no. 6, p. 157-210, pis. 6-10. 

Neumayr, Melchior, 1885, Die geographische Verbreitung

der Jura-formation: K. Akad. Wiss., Wien, Denkschr.

Math.-naturh. Kl., v. 50, p. 57-144, 1 pi. 

Newton, E. T., and Teal, J. J. H., 1897, Notes on a collection

of rocks and fossils from Franz Josef Land, made by

the Jackson-Harmsworth Expedition during 1894-96;

Geol. Soc. [London] Quart. Jour., v. 53, p. 477-519, pis.

37-41. 

Patton, W. W., Jr., and Tailleur, I. L., 1964, Geology of the

Killik-Itkillik region, Alaska: U.S. Geol. Survey Prof.

Paper 303-G, p. 409-500, pis. 50-51, figs. 66-91. 

Sokolov, D. N., 1912, Zur Ammonitenfauna des Petschoraschen Jura: Com. geol. St. Petersbourg Mem. new ser.,

Livr. 76, p. 1-65, 3 pis., 11 figs. 

Spath, L. F., 1927-33, Revision of the Jurassic cephalopod

fauna of Kachh (Cutch) : India Geol. Survey, Palaeontologia Indica, new ser., v. 9, 6 pts., 945 p., 130 pis.

 1932, The invertebrate faunas of the BathonianCallovian deposits of Jameson. Land (East Greenland): 

Medd. Gr0nland, v. 87, no. 7, 158 p., 26 pis., 14 figs.

Waagen, W. H., 1873-75, Jurassic fauna of Kutch. The 

Cephalopoda: India Geol. Survey, Palaeontologia Indica, 

vol. 1, pt. 1, p. 1-22, pis. 1-4 (1873) ; Pt. 2, p. 23-76, 

pis. 5-14 (1875) ; Pt. 3, p. 77-106, pis. 15-24 (1875) ; 

Pt. 4, p. 107-247, pis. 25-40 (1875).

Westermann, G. E. G., 1964, The ammonite fauna of the 

Kialagvik Formation at Wide Bay, Alaska Peninsula 

Part I, Lower Bajocian (Aalenian) : Bulls. Am. Paleontology, v. 47, no. 216, p. 327-503, pis. 44-76, 37 figs.

 1969, The ammonite fauna of the Kialagvik Formation at Wide Bay, Alaska Peninsula Part 2. Sonninia 

sowerbyi Zone (Bajocian) : Bulls. Am. Paleontology, v. 

57, no. 255, 226 p., 47 pis., 56 figs.

White, C. A., 1889, On invertebrate fossils from the Pacific 

coast: U.S. Geol. Survey Bull. 51, 102 p.

Whitfield, R. P., 1906, Notes on some Jurassic fossils from 

Franz Josef Land, brought back by a member of the 

Ziegler Exploring Expedition: Am. Mus. Nat. History 

Bull., v. 22, p. 131-134, pis. 18, 19.
INDEX

[Italic page numbers indicate major references and descriptions 1

Page

Aalenian (lower Bajocian) _----_-____- 5

Age of collection localities __-_------_- 9, 10

Aichilik River ________________________ 2, 7

collection locality _________________ 10

crinoid of Pliensbachian age ____-- 5

evidence for Callovian ----___----_ 18

Aleutian Range batholith ____________ 5

Amaltheus ------_----_-_-_____________ 5, 10

(Amaltheus) whiteavesi. Ammonites __ 11 

ambiguus, Inoceramus --___-_____.-__. 3, 5

Ammonites ishmae ___________________ 16

maclintocki _______________________ 10

(Amaltheus) whiteavesi __________ n

Arcticoceras _--_-__-________ 1, 2, 7, 16, 17, 18

ishmae _ _____... 3, 7, 16, 17; pi. 3

kochi _____________________________ 17

kochi zone -__-_--_--_____________ 7

pseudolambcrti -__-_----___________ 17

sp ------ _--__---_.._ 16

sp. juv ----_----_-___________ 8, 17; pi. 3

arcticus, Arctocephalites __-____.-- 8, 16; pi. 4

Arctocephalites -.-_________ 1, 2, 3, 4, 7, 14, 16

arcticus ___.----______________ 8, 16; pi. 4

callomoni _________________________ 16

elegans ______________ 3, 5, 7, 8, iff; pi. 4

nudus zone _______________________ 7

pilaeformis _______________________ 16

sp _. ._ --.._____________ 8

Arkelloceras __.-__-________ 1,2,3,6,7,14,15

elegans __----.________--__________ 14, 15

madearni _________________ 8, 14, 15; pi. 1

tozeri -_--_-__-____-_-_____________ 14, 15

sp. juv -----_-__--------__-___ 8, 15; pi. 1

B

balinensis, Choffatia __. 

belophora, Canavarella _ 

Biologic analysis _______

Boreal realm ammonites 

Brooks Range _________

Buchia fischeriana _____

C

Cache Creek ___________.________-_- 9, 10

Cadoceras ____________________________ 18

Cadoceratinae _-__---_________ _______ 1

callomoni, Arctocephalites --____-_____ 16

Camp 263 Creek, collection locality ____ 9

Canada, faunal comparisons with _ 6, 7, 14, 16

Canavarella _---___-.--__-_---_ 1,2,4,5,7,12

belophora _________________________ 12

crassifalcata ____________ 5, 8, 11, / '; pi. 1

sp ___----_______________-__-_-___ 8

Canning River ________________________ 14,15

collection localities ______________ 9,10,13

crinoid of Pliensbachian age ______ 5

extent and continuity of Middle

Jurassic beds ____________ 2,3,4

Cardioccras (Scarburgiccras) sp _______ 3,5

Cardioceratidae _____________________ 1,2,15

Page 

Choffatia _______________________ 1,2,18

balinensis ------------------------- 18

sakuntata __--_-_----_-_._______-- 18

sp -___----______-__.- 8, IS; pi. 2; pi. 4

Classificatory analysis _________________ 1

Cobbanites ----_-__-_--____---__-__-___ 7

Collection localities --__________-------- 9

Correlation with European, East

Greenland, Canadian, and 

southern Alaska faunas ___ 5, 14 

Cranoccphalites ______.. 1, 2, 4, 5, 7, 14, 15, 16

pompcckji -________-...._-.______ 15

pompcckji zone .___-----_------__ 7

vulgaris --._____________-__--._-- 16

sp -__-._________________ 3,8

crassifalcata, Canavarefla __._ 5, 8, 11, 12; pi. 1 

Cyclicoceras __________________________ 2

Disconformities ________________---__-- 3, 4

Duplication of sequences ______________ 4

E

Eagle Creek _____..___________-..._ 9,10

elegans, Arctocephalites ____ 3, 5, 7, 8, 16; pi. 4

Arkelloceras ________---__...._____ 14, 15

Enjcitoides _______________ 1,2,3,5,12,14

hoivelli ---_.._________- 2, 5, 7, 8, 14; pi. 3

sp --._______________.___. 8

European ammonite zone correlates __ 5, 6, 7 

Evolutionary lineage __________________ 2

fallax, Oppclia (Oxycerites) 

Faults ___-----__..-__._. 

Faunal settings ____--__.--.

._---._ 14 

3

._-____ 7

Fire Creek, collection localities __--_-.- 9, 10 

Folding, contorted beds _____-_-__------ 3

Fortress Creek, collection locality ______ 9

G

Geographic distribution of Bajocian and 

Bathonian ammonites in 

northern Alaska __-_._____ 7

Geographic location of collection

localities _________---_----_ 9

Graphoccras concavum zone ___________ 6

Graphoceratidae ______-___----_______-- 12

Gravel Creek, collection locality __--__- 10 

Greenland, ammonite sequence ------ 7, 16, 17

fireu-ingki, Pseitdocadoceras ________ 17; pi. 3

H

Hammatoceratidae _-________---------- 1,14

Hammatoceratinae -------------------- 1

Harpoccras maclintocki ________________ 10

u-hitcnvcsi ------------------------ 11

Harpoceratinae ______-_--_____--_----- 1

Hildoceratidae ____________--______---- 1,10

Holcophylloccras ---------------------- 7

Itou-clli, Enjcitoidcs ______ 2, 5, 7, 8, 14; pi. 3

Page

I

Ignek Mesa _______----------_-------- 17, 18

collection localities ________________ 9, 10

most complete Middle Jurassic

succession -------------- 3, 4, 5, 7

ignekensis, Cranoccphalites -..._ 3, 5, 8, 15; pi. 2 

Inoceramus ambiguus ________-----___.. 3, 5

lucifer ---------------- 3, 4, 5, 11, 12, 17

Interruptions in normal sequences __-_- 3 

Introduction ____-___-__--------------- 1

ishmae. Ammonites -------------------- 16

Arcticoceras ----------- 3, 7, iff, 17; pi. 3

Macroccphalites ------------------- 16

Itkillik River, Middle Jurassic outcrops _ 2

Jasper Park in Alberta

K

Katakturuk Canyon ___ ---------- 5,10,12

collection locality -_----..--_-_----- 9

partial sequence of Kingak Shale -- 4 

Katakturuk River ___---__-----_------- 9

Kaviak Creek, collection localities ----- 9

crinoids _______________-_-__--_--- 5

Kekiktuk River, co'.lection locality __._ 9 

kcllumi, Oppclia (Liroxyitcs) ---------- 14

Kepplcrites ---------------------------- 7

Killik River, Middle Jurassic outcrops . - 2 

Kimmeridgian ________________________ 3

Kingak Shale Sec in text under species

occurrence and locality

descriptions. 

kochi, Arcticoceras -------------------- 17

Leioccras --_-_--__--_---_------------ 7

opalinum ------------------------ 5

Leioceratinae ------------------------ 1

Liroxyitcs ---------------------------- 2,14

(Liroxyitcs), Oppclia ------------------ 1

(Liroxyitcs} kelhimi. Oppclia ---------- 14

Lithologry, collection sites ------------- 0

Middle Jurassic beds ____---_---..- 2, 3

lucifer, Inoceramus ___-____.- 3,4,5,11,12,17

LudwigcUa rudis ---------------------- 10

Ludirigia maclintocki ----------------- 10

M

madearni, Arkelloceras __.--_ 8, 14, 15; pi. 1 

madintocki, Ammonites -------------- 10

Harpoccras ---------------------- 10

Ludu-igia ------------------------- 10

Pscudolioccras _-__-_ 3, 5, 7, 8, 10, 17; pi. 1

wliitcarcsi, Pscudolioccras . 

Macroccphalites ishmae ___---. 

Macrophylloccras -------------

Marsh Creek, collection locality 

Mixed faunas _________-_._---.

Mount Weller _-_____----------

21
22 INDEX

O

Oecotraustes -- __ ---- __-_____-_--__

Okerokovik River, collection locality __ 

opalinum, Leioceras _ _ _____________ _

Oppelia --- _-- ____ _______ __

(Liroxyites) _______ ____ ___

kellumi _______________________

Page

7

10

5

14

1

14

n. sp ____________ 1, 14; pi. 1

(Oxycerites) _____________________ 7,14

fattax 14

Oppeliidae ___________________________ 1, 14

Oppeliinae ________

Otoites sauzei zone 

Oxfordian _____ __

______________ 1

____--_-___--- 5, 6

______________ 3,4

(Oxycerites), Oppelia _________-_--__-- 7, 14

fattax, Oppelia .--______-__ _ ______ 14

Oxytoma jacksoni ____________________ 11

Pacific realm ammonites _-_-______-___ 7

Paleobiogeographic differentiation _____ 7

Paraeineckeia ________________________ 7

Pentaerinus subangularis alaska ______ 5

Perisphinctidae _____________________ 1, 18

piaeformis, Arctocephalites ___________ 16

Plieatula _________________________ 5

Pliensbachian _______________________ 5

Point Barrow-Cape Simpson area

subsurface Middle Jurassic

beds ______________ 2

pompeckji, Cranocephalites ____________ 15

Previously unrecorded genera __________ 2

Procerites __________________________ 18

Pseudocadoeeras ______________________ 2, 17

grewingki ____________________ 17; pi. 3

pseudolamberti, Arcticoceras ___________ 17

Page 

Pseudolioceras ______ _ 1, 2, 5, 10, 12, 15

maclintocki _________ 3, 5, 7, 8, iO, 17; pi. 1

maclintocki whiteavesi ____________ 11

whiteavesi ________ 2, 3, 5, 7, 8, 10, 11; pi. 1

Pseudoperisphinctinae ___-----_- -____ 1

R

Reineckeia (Reineckeites) ___-__-_---_ 15, 17 

(Reineekeites) stuebeli ____________ 14

(Reineckeites), Reineckeia _____________ 15, 17

stuebeli, Reineckeia ______

Repetition of faunules _______

Richardson Mountains in Yukon 

Territory _________

rudis, Ludwigella ____________

6

10

Sadlerochit Mountains _--____-__--._ 9

Sadlerochit River __________ __ 5, 13 

collection localities ____-----------_ 9

Sagavanirktok River, Middle Jurassic

outcrops _-___--___-------_ 2

Saviukviayak River, probable Middle

Jurassic exposures __ 2, 10, 17, 18 

(Scarburgiceras) sp., Cardioceras _____ 3, 5

scissum, Tmetoceras _________ ______ 2

Seaway connections ______ __-__. 7

Shublik Island _________________ 3,4,9 

Siemiradzkia _________________________ 7

Sonninia sowerbyi zone ________________ 5, 7

Stemmatoceras _____--_____-_------_-_ 6

Stephanoceratidae _-_--__-------------_ 1, 14

Stratigraphic assignment of collection

localities __________________ 9

Page

Stratigraphic distribution of ammonites _ 

Stratigraphic summary of Middle

Jurassic beds in northern 

Alaska ____________ -- 

stuebeli, Reineckeia (Reineckeites) ___

Tethyan realm ammonites ______ 7

Tigulpuk Creek, collection locality __ 9

Tithonian __-_-_.__--______-----_----_-- 3

Tmetoceras ________________ 1,2,5,7,10

scissum _____________-__---_-___--- 2

sp ______________________ 8, 10

Tmetoceratinae _______________________ 1

tozeri, Arkelloceras -------------------- 14, 15

Turgites ivhiteavesi ------------------- 11

U 

Unconformities, Callovian _____________ 4

Callovian, only positive evidence

for _______--________--_-_ 18

late middle to late Bajocian age ___ 2, 4 

middle Bajocian-Tithonian _________ 3

southern Alaska _____ _________ 5

vulgaris, Cranocephalites _____________ 16

W

whiteavesi, Ammonites (Amaltheus) __ 11 

Harpoceras ____________________ 11

Pseudolioceras ____ 2,3, 5, 7, 8, 10, 11; pi. 1

Pseudolioceras maclintocki ________ 11

Turgites --------------------- ___ 11

Wide Bay, Alaska Peninsula __________ 6

X

Xenocephalites _______________________ 7

* U.S. GOVERNMENT PRINTING OFFICE: 1975 0-211-319/35
PLATES 1-4

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

[Figures natural size unless otherwise indicated]

FIGURES 1-5,7. Pseudolioceras maclintocki (Haughton) (p. 10).

1. Hypotype, USNM 192130 from USGS Mesozoic loc. 21023.

2. Hypotype, USNM 192129 from USGS Mesozoic loc. 22595.

3. Hypotype, USNM 192127 from USGS Mesozoic loc. 24035.

4. Rubber imprint of external mold of hypotype, USNM 192126 from USGS Mesozoic loc. 21023.

5. Hypotype, USNM 192125 from USGS Mesozoic loc. 29152. 

7. Hypotype, USNM 192128 from USGS Mesozoic loc. 21023. 

6,8-14. Canavarella crassifalcata Imlay, n. sp. (p. 12).

6. Paratype, USNM 192136 from USGS Mesozoic loc. 29153.

8,9. Lateral view and suture line (X 3) drawn at whorl height of 8 mm. Paratype, USNM 192138 

from USGS Mesozoic loc. 29884.

10. Paratype, USNM 192135 from USGS Mesozoic loc. 29153.

11. Holotype, USNM 192134 from USGS Mesozoic Iocs. 29154 and 29156. Shows nearly half a whorl 

of body chamber. Note that the two parts of the holotype were collected at two localities.

12. Rubber imprint of external mold of paratype, USNM 192137 from USGS Mesozoic loc. 30267.

13. Paratype, USNM 192139 from USGS Mesozoic loc. 29154.

14. Paratypes, USNM 192140 from USGS Mesozoic loc. 30268. Shows that falcate ribbing develops at

a small size. 

15. Oppelia (Liroxyites) n. sp. undet. (p. 14).

Adult body whorl of specimen USNM 192142 from USGS Mesozoic loc. 29435. 

16-18. Pseudolioceras whiteavesi (White) (p. 11).

16. Rubber imprint of external mold (X 2). Hypotype USNM 192131 from USGS Mesozoic loc. 29147.

17. Small pyritic hypotype, USNM 192133-from USGS Mesozoic loc. 21023.

18. Internal mold (X 2). Hypotype, USNM 192132 from USGS Mesozoic loc. 10307. Note sharp raised

umbilical edge in figures 16-18. 

19,20. Arkellocerast sp. juv. (p. 15).

Rubber imprint of external mold (X 2) of specimen, USNM 192149 from USGS Mesozoic loc. 22591. 

21-26. Arkelloceras cf. A. maclearni Frebold (p. 14).

21. Rubber imprint of external mold, specimen USNM 192147 from USGS Mesozoic loc. 29141.

22. Specimen, USNM 192148 from USGS Mesozoic loc. 24033. Shows prominent lateral tubercles at an 

early growth stage.

23. Specimen, USNM 192144 from USGS Mesozoic loc. 21024.

24. Specimen, USNM 192145 from USGS Mesozoic loc. 22597. Shows ventral tubercles or swellings.

25. Specimen, USNM 192146 from USGS Mesozoic loc. 22597.

26. Specimen, USNM 192143 from USGS Mesozoic loc. 24033. Two-fifths of outer whorl is nonseptate.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 1

PSEUDOLIOCERAS, CANAVARELLA, OPPELIA (LIROXYITES), ARKELLOCERAS?, AND ARKELLOCERAS
PLATE 2

[All figures except suture line are natural size]

FIGURES 1-9,11,12. Cranocephalites ignekensis Imlay, n. sp. (p. 15).

1,8. Complete adult body chamber and final suture line (X 2) of finely ribbed holotype, USNM 

192151 from USGS Mesozoic loc. 28817.

2. Finely ribbed paratype, USNM 192155 from USGS Mesozoic loc. 28817.

3. Finely ribbed paratype, USNM 192154 from USGS Mesozoic loc. 29435.

4. Finely ribbed paratype, USNM 192153 from USGS Mesozoic loc. 29143.

5. Moderately ribbed adult body chamber of paratype, USNM 192156 from USGS Mesozoic loc. 

28817.

6. Rubber imprint of external mold of moderately ribbed paratype, USNM 192157 from USGS 

Mesozoic loc. 28817.

7. Rubber imprint of external mold of moderately ribbed paratype, USNM 192152 from USGS 

Mesozoic loc. 28817. This specimen occurs on same slab as the finely ribbed holotype.

9. Fragment of inner whorl of moderately ribbed paratype, USNM 192158 from USGS Mesozoic 

loc. 29855.

11. Rubber imprint of external mold of coarsely ribbed paratype, USNM 192160 from USGS 

Mesozoic loc. 29435.

12. Rubber imprint of coarsely ribbed paratype, USNM 192159 from USGS Mesozoic loc. 29143. 

10. Choffatlat sp. (p. 18).

Internal mold of specimen, USNM 180733 from USGS Mesozoic loc. 30075. See other views on plate 

4, figures 9, 11.
GEOLOGICAL SURVEY

v>,

PROFESSIONAL PAPER 854 PLATE 2

CRANOCEPHALITES AND CHOFFATIA?
PLATE 3

[All figures are natural size]

FIGURES 1,2. Arcticoceras sp. juv. (p. 17).

Immature specimens, USNM 180732 from USGS Mesozoic loc. 29877. 

3,4. Arcticocerasl sp. juv. (p. 17).

Rubber imprint of external mold of specimen formerly described as Pseudocadoceras grewingki 

(Pompeckj) by Imlay (1955, p. 90, pi. 12, fig. 1). USNM 108781 from USGS Mesozoic loc. 22745. 

5,6,10. Erydtoides cf. E. howelli (White) (p. 14).

5, 6. Ventral and lateral views of specimen, USNM 192141 from USGS Mesozoic loc. 29153. 

10. Laterally crushed specimen, USNM 180730 from USGS Mesozoic loc. 29150. 

7-9,11-22. Arcticoceras ishmae (Keyserling) (p. 16).

All specimens from USGS Mesozoic loc. 30075 unless indicated otherwise.

7, 8. Lateral and ventral views of septate finely ribbed hypotype, USNM 192164.

9. Ventral view of finely ribbed body chamber. Hypotype, USNM 192167.

11. Laterally crushed finely ribbed hypotype, USNM 192165.

12. Immature finely ribbed hypotype, USNM 192166.

13. Moderately ribbed hypotype, USNM 192170.

14. Moderately ribbed hypotype, USNM 192168.

15. Moderately ribbed inner whorls. Hypotype, USNM 192172.

16. Moderately ribbed inner whorls. Hypotype, USNM 192171.

17,18. Moderately ribbed, lateral and ventral views of hypotype, USNM 192169.

19. Coarsely ribbed venter of hypotype, USNM 192173.

20. Coarsely ribbed laterally crushed hypotype, USNM 192174.

21. Coarsely ribbed laterally crushed hypotype, USNM 192175.

22. Coarsely ribbed, worn hypotype, USNM 192176 from USGS Mesozoic loc. 21023.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 3

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ARCTICOCERAS, ARCTICOCERAS?, AND ERYCITOIDES
PLATE 4

[All figures are natural size]

FIGURES 1-8. Arctocephalites cf. A. elegans Spath (p. 16).

1-3. Ventral and lateral views of adult specimen, USNM 192160 from USGS Mesozoic lac. 29145. Note

smoothness of body chamber.

4, 5. Adult smooth body chamber of specimen, USNM 192161 from USGS Mesozoic loc. 29143. 

6-8. Rubber imprint of ribbed inner whorl and ventral view of smooth outer whorl of same specimen,

USNM 192162 from USGS Mesozoic loc. 29435. 

9,11. Choffatiat sp. (p. 18).

Lateral and ventral views of septate whorls. Specimen, USNM 180733 from USGS Mesozoic loc. 30075.

Other view shown on plate 2, figure 10. 

10. Arctocephalites cf. A. arcticus (Newton and Teall) (p. 16).

Rubber imprint of laterally crushed specimen, USNM 192163 from USGS Mesozoic loc. 29146.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 4

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ARCTOCEPHALITES AND CHOFFATIA?