Early Triassic (Smithian) Ammonites

C* T% 1 * 1 A f^T* *

or raleoequatorial Affinity 

from the Chulitna Terrane, 

South-central Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1121-B
Early Triassic (Smithian) Ammonites 

of Paleoequatorial Affinity 

from the Chulitna Terrane, 

South-Central Alaska

By K. M. NICHOLS and N. J. SILBERLING

GEOLOGIC FRAMEWORK OF THE UPPER CHULITNA DISTRICT, ALASKA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1121-B

Documentation of an equatorial fauna interpreted 

to have been tectonicatty displaced northward

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Nichols, Kathryn Marion, 1946-

Early Triassic (Smithian) ammonites of paleoequatorial affinity

from the Chulitna terrane, south-central Alaska.

(Geologic framework of the upper Chulitna district, Alaska)

(Geological Survey professional paper ; 1121-B)

Bibliography: p. 4-5.

Supt.ofDocs.no.: I 19.16:1121-B

1. Ammonoidea. 2. Paleontology Triassic. 3. Paleontology 

Alaska. I. Silberling, Norman John, 1928- joint author.

II. Title. III. Series: United States. Geological Survey.

Professional paper ; 1121-B. 

QE807.A5N5 564'.53 79-607988

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

Washington, D.C. 20402

Stock number 024-001-03253-8
CONTENTS

Abstract __________________________________________________Bl

Introduction________________________________________________ 1 

Occurrence __________________________________________________ 1

Nature of fauna ____________ ___________________________—————— 3 

Paleogeographic interpretation ________________________———————————— 3 

References cited ________________________________———__—————— 4

ILLUSTRATIONS

[Plates follow references]

PLATE 1. Meekoceras, Arctoceras, Dieneroceras, Aspenites, Owenites, Xenoceltites, and Wyomingites.

2. Paranannites, Metussuria, Lanceolites, and Juvenites.

3. Euflemingites.

Page

FIGURE 1. Location of documented Lower Smithian ammonite localities in North America________ _____———————————— B2 

2. Photomicrographs of limestone from USGS Mesozoic locality M5027, Upper Chulitna district, Alaska _____————— 5

TABLE

Page

TABLE 1. Comparison of the lower Smithian ammonoid fauna from the Chulitna terrane with ammonoid faunas of the same

age from other parts of North America _____________________________—————————————————— B4

III

EARLY TRIASSIC (SMITHIAN) AMMONITES OF PALEOEQUATORIAL 

AFFINITY FROM THE CHULITNA TERRANE, SOUTH-CENTRAL

ALASKA

By K. M. NICHOLS and N. J. SILBERLING

ABSTRACT

Lower Triassic limestone is part of the unique stratigraphic succession of the Chulitna terrane. This terrane is believed to be a 

greatly displaced lithosphere fragment whose exposures are limited 

to a 400 km2 area on the south flank of the central Alaska Range in 

Alaska. The nearest known correlative Lower Triassic marine strata 

are located hundreds of kilometers distant in northern Alaska and 

northwestern British Columbia; in general, they are not represented 

elsewhere among the oceanic-volcanic pre-Tertiary sequences of the 

entire circumpacific margin.

Ammonites are the dominant megafossils in the Lower Triassic 

limestone of the Chulitna terrane and are represented in a single bed 

by 13 identifiable species assigned to 13 genera, of which Meekoceras, 

Dieneroceras, Arctoceras, and Paranannites are the most abundant.

Ammonites in the Chulitna fauna are entirely of species previously described from the western conterminous United States from 

rocks of early Smithian age that were deposited along the margin of 

the North American craton at paleolatitudes of about 10° north. The 

Chulitna fauna is much less similar to faunas of this age from localities in western Canada and the North American arctic, representing paleolatitudes greater than 20° north. Moreover, remnants of 

the original marine carbonate cement in the ammonite-bearing rock 

are acicular and evidently formed in warm water; their presence may 

indicate that the Lower Triassic limestone and associated rocks of 

the Chulitna terrane were tectonically transported from a site much 

farther south than their present location.

INTRODUCTION

The Chulitna terrane (Jones and others, 1979) is 

characterized by a distinctive assemblage of depositionally or tectonically related Paleozoic and 

Mesozoic rocks. Its exposures are limited to a belt less 

than 10 km wide and 50 km long in the Upper Chulitna 

district on the south flank of the central Alaska Range, 

about 50-75 km east of Mt. McKinley. Despite the limited outcrop area of the terrane, pre-Cretaceous rocks 

included in it are in strong lithologic contrast with correlatives in adjacent and nearby terranes, and some 

parts of the Chulitna terrane have no parallel in 

Alaska. Jones and others (1979) infer that the 

Chulitna terrane is a tectonic fragment of a lithosphere 

plate that formed at a great distance from its present 

site and has been displaced generally northward.

One of the most unusual features of the Chulitna 

terrane is the occurence in it of fossiliferous marine 

Lower Triassic limestone. Other exposures of correlative marine rocks in North America are limited to settings well inland along the miogeoclinal western and 

northern edges of the craton. The closest known 

marine Lower Triassic strata are in northern Alaska 

and northeastern British Columbia (fig. 1). Both of 

these regions are at least hundreds of kilometers distant and are separated from the Upper Chulitna district by vast tracts whose complex and varied geology 

manifests large-scale tectonic displacements.

The purpose of this paper is to document the age of 

the marine Lower Triassic rocks of the Chulitna 

terrane on the basis of their ammonite fauna. In addition, the taxonomic character of this fauna is compared 

with that of other correlative faunas from North 

America to show that its affinities are with paleogeographically equatorial faunas.

OCCURRENCE

The ammonite-rich Lower Triassic limestone of the 

Chulitna terrane is known only from three small isolated exposures. One of these (USGS Mesozoic loc. 

M5027), which is locality 20 of Silberling and others 

(1978) and of Jones and others (1979, pi. 1), was discovered by Hawley and Clark (1974, pi. 1, loc. 6). Ammonites originally collected from this locality were discussed briefly by Silberling (in Hawley and Clark, 

1974, p. B4-B5). This report is based on extensive new 

collections made in 1976 from this locality, which is a 

single, steeply dipping bed about 20 cm thick that was 

exposed for 2-3 m along strike in a bulldozer cut before 

being quarried away at the surface during collecting. 

This bed is in the middle part of about 10 m of stratigraphic section represented by scattered, partly artificial exposures of limestone. Nearby outcrops are of 

basalt and conglomeratic red beds whose age is interpreted as Late Triassic, more Lower Triassic limestone, 

and fine-grained clastic rocks of probable Permian age.

Bl
B2

180

160

40

140

30

GEOLOGIC FRAMEWORK OF THE UPPER CHULITNA DISTRICT, ALASKA

180° 70° &0° 160° 140° 120° 100° 80°
EARLY TRIASSIC AMMONITES OF PALEOEQUATORIAL AFFINITY B3

Relations of these various rocks, which are cut by 

numerous faults, to the ammonite-bearing Lower 

Triassic limestone are obscured by poor exposure.

Another exposure of these Lower Triassic rocks, discovered in 1977, is about 2 km west-southwest, at locality 19 of Silberling and others (1978) and of Jones 

and others (1979, pi. 1). Here, several of the same distinctive species of Smithian ammonites were collected 

from limestone whose exposed thickness is only about 1 

m. A short distance uphill, across a covered interval, is 

a massive basalt flow about 10 m thick overlain by red 

conglomeratic sandstone lithologically similiar to that 

associated with fossiliferous Upper Triassic red beds 

elsewhere in the Chulitna terrane. On strike with this 

locality, about 200 m farther south, the Lower Triassic 

limestone reappears. Here, the Smithian ammonite 

fauna is poorly preserved, but the unconformable relation between the Lower Triassic and the overlying 

Upper Triassic red beds and associated basalt flows is 

better exhibited, as described in Jones and others 

(1979). None of the ammonites from these additional 

Lower Triassic localities represents any species different from those known previously from USGS Mesozoic 

locality M5027. Consequently, all of the ammonites 

treated in the present study are from locality M5027, a 

geographic description of which is:

FIGURE 1. Location of documented lower Smithian ammonite localities in North America. Localities marked by • denote faunas of 

equatorial paleolatitude affinity while those marked by x denote 

faunas of northern paleolatitude affinity. Faunal locality 13, 

marked by a triangle, is dominated by the pelecypod Posidonia 

mimer, which is interpreted by others to indicate northern 

paleolatitudes. The equator and the 20° N. latitude line of Early 

Triassic time are after Van der Voo and French (1974). Localities 

numbered on the map are as follows:

1. Upper Chulitna district, Alaska (Clark and others, 1972; Hawley and Clark, 1974; this report).

2. Atigun Gorge, Alaska (USGS Mesozoic loc. M2194).

3. Lupine River, Alaska (USGS Mesozoic loc. M2214).

4. Fire Creek, Alaska (USGS Mesozoic loc. M6050).

5. Inyo Mountains, California (Hyatt and Smith, 1905; Smith, 

1932).

6. Confusion Range, Utah (Hose and Repenning, 1959).

7. Phelan Ranch, Elko County, Nevada (Smith, 1932).

8. Crittenden Spring, Nevada (Kummel and Steele, 1962).

9. Bear Lake County, Idaho (White, 1880; Smith, 1932).

10. Caribou County, Idaho (White, 1880; Smith, 1932).

11. Kelly Hill, Washington (Kuenzi, 1965).

12. Halfway River, British Columbia, Canada (Tozer, 1963, 1967, 

written commun., 1974).

13. Liard River, British Columbia, Canada (Tozer, 1967, written 

commun., 1974).

14. Smith Creek and Hare Fiord, Ellesmere Island, Arctic Canada 

(Tozer, 1961, 1967, written commun., 1974).

15. Lindstrom Creek, Ellesmere Island, Arctic Canada (Tozer, 

1961, 1967, written commun., 1974).

16. Bunde Fiord, Axel Heiberg Island (Tozer, 1965, 1967, written 

commun., 1974).

U.S. Geological Survey Healy A-6 quadrangle; 

south flank of Alaska Range; Upper Chulitna district; Golden Zone mine area, about 2Vz km south of 

West Fork of Chulitna River; 13.19 km N. 25.0° E. 

from VABM 5048 (Copeland); lat. 63° 13.2' N., long. 

149° 38.9' W.

NATURE OF FAUNA

Megafossils from locality M5027, as well as those in 

the small collections made from the two additional localities discussed above, are all cephalopods and 

bivalves. The exposures of Lower Triassic limestone in 

general contain only these kinds of megafossils except 

that some beds, other than the one containing the ammonite fauna, are largely composed of crinoid columnals. Within the ammonite-bearing bed the only abundant bivalve fossils are small shells of a Posidonia-\ike 

pectenacid (misidentified by Silberling in Hawley and 

Clark, 1974, p. B6, as P. mimer Oeberg). Mytilacid and 

aviculopectinid bivalves are represented by only a few 

specimens.

Aside from large orthoconic nautiloids, all the 

cephalopods are ammonites which are assigned to an 

indeterminate species of Pseudosageceras and to the 

following 13 nominal species:

Xenoceltites intermontanus (Smith)

Meekoceras gracilitatis White

Wyomingites aplanatus (White)

Dieneroceras knechti (Hyatt and Smith)

Euflemingites cirratus (White)

Arctoceras tuberculatum (Smith)

Juveniles septentrionalis Smith

Paranannites aspenensis Hyatt and Smith

P. slossi (Kummel and Steele)

Owenites cf. O. koeneni Hyatt and Smith

Metussuria waageni (Hyatt and Smith)

Lanceolites compactus Hyatt and Smith

Aspenites acutus Hyatt and Smith 

Of these ammonites, the species of Meekoceras, 

Dieneroceras, Euflemingites, Arctoceras, and Paranannites are most abundant; several of the other species 

listed are represented only by a single specimen. The 

total species diversity is about that to be expected from 

exhaustive sampling of ammonites from a single bed at 

one place (Tozer, 1971, p. 997).

All the ammonite species identified from locality 

M5027 are known only from strata of early Smithian 

age within the Lower Triassic.

PALEOGEOGRAPHIC INTERPRETATION

It is of particular importance for paleogeographic interpretation that the species of Lower Triassic ammo-
B4 GEOLOGIC FRAMEWORK OF THE UPPER CHULITNA DISTRICT, ALASKA

nites from the Chulitna terrane are entirely the same 

as those known from the western conterminous United 

States; few of them are known from correlative faunas 

at northern latitudes comparable to that of the Alaskan locality. These relations are detailed in table 1, 

wherein comparison is made with other lower Smithian ammonite faunas from localities scattered north 

and south along the western and arctic margin of the 

North American craton. These localities are grouped 

into those representing equatorial paleolatitudes (less 

than 20° north) and northern paleolatitudes (more 

than 20° north). For most of them, their geologic settings assure that they have not been tectonically 

transported beyond these groupings. The fauna of the 

Chulitna terrane is compared with the total number of 

seemingly valid early Smithian genera and species in 

each of these two latitudinally separate regions. This 

procedure is used because the actual diversity at all 

possible levels within the lower Smithian for the entire 

western and northern margin of the North American 

craton cannot be known, whereas the diversity of the 

Chulitna-terrane fauna is known from a single 20-cmthick bed.

The similarity of the ammonite fauna from the 

Chulitna terrane with that of the western conterminous United States and its lack of close affinity with that 

of northern North America are striking. An 

ammonite-bearing bed exactly like that at locality 

M5027 in its taxonomic makeup would not be out of 

place in northeastern Nevada or southeastern Idaho.

Assuming that the faunas on which figure 1 and 

table 1 are based represent, for both the high and low 

paleolatitude groups, a random sample for all different 

levels within the lower Smithian substage, the overall 

taxonomic diversity for the northern group seems to be 

significantly lower (by a factor of 0.5 or less) than that 

for the southern group. This finding matches that of

TABLE 1.—Comparison of the lower Smithian ammonoid fauna from 

the Chulitna terrane with ammonoid faunas of the same age from 

other parts of North America

Species Genera

Number of taxa identified 

in Chulitna terrane _ 13 13

Taxa from Chulitna also recognized 

elsewhere:

In equatorial faunas1

Total number of taxa recognized: 

In equatorial faunas 1

____ 13

2

____ 41

-___ 17

13

7

24

12

1 Faunas from localities near the paleoequator of Early Triassic time, shown as localities 

5-11 on fig. 1.

2 Faunas from localities north of paleolatitude 20° N. of Early Triassic time, shown as 

localities 2-4 and 12-16 on fig. 1.

Kummel (1973), who concludes that temperature is 

probably the primary controlling factor for this diversity pattern. The diversity of the Chulitna fauna from a 

single bed at one outcrop is about as great as the total 

known diversity for the entire early Smithian subage 

in high paleolatitudes of North America. This diversity 

alone is sufficient to suggest an origin at a relatively 

low paleolatitude.

Some extension of warm water temperatures into 

relatively high paleolatitudes in the Pacific basin may 

have resulted from the particular configuration of 

oceans and continents during Triassic time as modeled 

by Donn and Shaw (1977). However, in terms of its 

taxonomic composition and diversity, the Chulitnaterrane fauna is still more southern in its character 

than the correlative fauna from northeastern British 

Columbia, which represents a paleolatitude appreciably lower than that of the present site of the Chulitna 

terrane in Alaska.

Petrographic examination of the ammonite-bearing 

bed at locality M5027 in the Upper Chulitna district 

reveals a distinctive early diagenesis that also suggests an origin in the relatively warm marine waters of 

low paleogeographic latitudes. Although the original 

carbonate fabrics of these rocks have been altered to a 

neomorphic mosaic of medium-crystalline equant calcite, and some of the carbonate has been replaced by 

silica, local intracrystalline impurities preserve ghosts 

of an original isopachous acicular carbonate cement 

(fig. 2). Water from which this cement crystallized was 

evidently as rich in magnesium as normal marine 

water and sufficiently warm to have had a relatively 

high crystallization rate with respect to calcium carbonate. (For example, see Folk, 1973.) Geologically young 

examples of this kind of carbonate cement are found 

only at modern-day equatorial latitudes.

On the basis of (1) the overall diversity of its ammonite fauna, (2) the taxonomic comparison of its ammonite fauna with other correlative faunas from known 

paleolatitudes in North America, and (3) its petrographic character, the Lower Triassic limestone of the 

Chulitna terrane supports the interpretation that this 

terrane has been displaced from a site much farther 

south than its present location.

REFERENCES CITED

Clark, A. L., Clark, S. H. B., and Hawley, C. C., 1972, Significance of 

upper Paleozoic oceanic crust in the Upper Chulitna district, 

west-central Alaska Range; in Geological Survey research 1972: 

U.S. Geological Survey Professional Paper 80G-C, p. C95-C101.

Donn, W. L., and Shaw, D. M., 1977, Model of climate evolution 

based on continental drift and polar wandering: Geological Society of America Bulletin, v. 88, p.390-396.
EARLY TRIASSIC AMMONITES OF PALEOEQUATORIAL AFFINITY B5

J B

FIGURE 2.—Photomicrographs of limestone from USGS Mesozoic locality M5027, Chulitna district, Alaska. Bar scale = 0.50 mm. 

A, Neomorphosed skeletal grainstone with geopetal patches of pelletal micrite. Skeletal fragments are thin-shelled bivalves and 

ammonites, the outlines of which are preserved as very thin lines of impurities. Shells have been rimmed by two or more generations of 

intergranular acicular carbonate cement. B, Magnification of A showing two or more generations of fibrous calcite cement. A thin band 

of first-generation cement is adjacent to the shell fragments. This cement is separated by a fuzzy line of dark impurities from a 

subsequent thicker band of cement. C, Neomorphosed skeletal grainstone with very thin molluscan shell fragments cemented by 

intergranular acicular carbonate cement. The calcite cement has been partially replaced by length-fast fibrous chalcedony.

Folk, R. L., 1973, Carbonate petrograpy in the post-Sorbian age, in 

Ginsburg, R. N., ed., Evolving concepts in sedimentology: Johns 

Hopkins Univ. Press, p. 118-158.

Hawley, C. C., and Clark, A. L., 1974, Geology and mineral deposits 

of the Upper Chulitna district, Alaska: U.S. Geological Survey 

Professional Paper 758-B, p. B1-B47.

Hose, R. K., and Repenning, C. A., 1959, Stratigraphy of Pennsylvanian, Permian, and Lower Triassic rocks of Confusion Range, 

west-central Utah: American Association of Petroleum 

Geologists Bulletin, v. 43, p. 2167-2196.

Hyatt, Alpheus, and Smith, J. P., 1905, The Triassic cephalopod genera of North America: U.S. Geological Survey Professional 

Paper 40, 394 p.

Jones, D. L., Silberling, N. J., Csejtey, Bela, Jr., Nelson, W. H., and 

Blome, C. D., 1979, Age and structural significance of ophiolite 

and adjoining rocks in the Upper Chulitna district, south-central 

Alaska: U.S. Geological Survey Professional Paper 1121-A, 

21 p.

Kuenzi, W. D., 1965, Early Triassic (Scythian) ammonoids from 

northeastern Washington: Journal of Paleontology, v. 39, p. 

365-378; pi. 53.

Kummel, Bernhard, 1973, Lower Triassic (Scythian) molluscs, in 

Hallam, A., ed., Atlas of palaeobiogeography: Amsterdam, 

Elsevier, p. 225-233.

Kummel, Bernhard, and Steele, Grant, 1962, Ammonites from the 

Meekoceras gracilitatus Zone at Crittenden Spring, Elko County,

Nevada: Journal of Paleontology, v. 36, p. 638-703, pis. 99-104.

Silberling, N. J., Jones, D. L., Csejtey, Bela, Jr., and Nelson, W. H., 

1978, Interpretive bedrock geologic map of part of the Upper 

Chulitna district (Healy A-6 quadrangle), Alaska Range, 

Alaska: U.S. Geological Survey Open-File Rept. 78-545.

Smith, J. P., 1932, Lower Triassic ammonoids of North America: U.S. 

Geological Survey Professional Paper 167, 199 p.

Tozer, E. T., 1961, Triassic stratigraphy and faunas, Queen 

Elizabeth Islands, Arctic Archipelago: Canada Geological Survey Memoir 316, 116 p., 30 pis.

————1963, Lower Triassic ammonoids from Tuchodi Lakes and 

Halfway River areas, northeastern British Columbia: Canada 

Geological Survey Bulletin, v. 96, p 1-28.

————1965, Lower Triassic stages and ammonoid zones of arctic 

Canada: Canada Geological Survey Paper 65-12, 14 p.

————1967, A standard for Triassic time: Canada Geological Survey 

Bulletin 156, 103 p., 10 pis. 

-1971, Triassic time and ammonoids: problems and proposals:

Canadian Journal of Earth Science, v. 8, p. 989-1031.

Van der Voo, R., and French, R. B., 1974, Apparent polar wandering 

for the Atlantic-bordering continents: Late Carboniferous to 

Eocene: Earth-Science Reviews, v. 10, p. 99-119.

White, C. A., 1880, Contributions to invertebrate paleontology, no. 5; 

Triassic fossils of southeastern Idaho: U.S. Geological and Geographical Survey of the Territories, 12th Annual Report, pt. 1, p. 

105-118, pis. 31-32.

PLATES 1-3

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

Library, Federal Center, Denver, Colorado 80225
PLATE 1

[All figures natural size unless otherwise indicated]

Lower Triassic (Smithian) ammonites from USGS Mesozoic locality M5027, Upper Chulitna

district, Alaska.

FIGURES 1-4. Meekoceras gracilitatis White. 

1-2. USNM 248596.

3. USNM 248597.

4. Suture line (x4) of USNM 248597. 

5-9. Arctoceras tuberculatum (Smith). 

5-6. USNM 248598.

7. Suture line (x5) of USNM 248598. 

8-9. USNM 248599.

10-11. Aspenites? cf. A. acutus Hyatt and Smith. USNM 248602. 

12-14. Aspenites acutus Hyatt and Smith. 

12-13. USNM 248603 (x2)

14. Suture line (xlO) of USNM 248603. 

15-16. Aspenites cf. A. acutus Hyatt and Smith. USNM 248604 (Fig. 16 is a broken cross

section). 

17-18. Owenites cf. O. koeneni Hyatt and Smith.

17. USNM 248605 (x2).

18. Suture line (x 10) of USNM 248605. 

19-21. Wyomingites aplanatus (White). 

19-20. USNM 248608.

21. Suture line (x 12) of USNM 248608. 

22-26. Dieneroceras knechti (Hyatt and Smith). 

22-23. USNM 248600.

24. Suture line (x5) of USNM 248600. 

25-26. USNM 248601. 

27-29. Xenoceltites sp.

27-28. USNM 248607.

29. Suture line (x8) of USNM 248607. 

30-32. Xenoceltites intermontanus (Smith). 

30-31. USNM 248606.

32. Suture line (x9) of USNM 248606.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1121-B PLATE 1

22 23

MEEKOCERAS, ARCTOCERAS, DIENEROCERAS, ASPENITES, OWENITES, XENOCELTITES.AND WYOMINGITES
PLATE 2

[All figures natural size]

Lower Triassic (Smithian) ammonites from USGS Mesozoic locality M5027, Upper Chulitna district, Alaska.

FIGURES 1-10. Parannannites aspenensis Hyatt and Smith. 

1-2. USNM 248612. 

3-4. USNM 248613. 

5-7. USNM 248614.

8. Suture line (x7) of USNM 248614. 

9-10. USNM 248615. 

11-13. Paranannites sp. USNM 248616. 

14-24. Juveniles septentrionalis Smith 

14-15. USNM 248621.

16. Suture line (x8) of USNM 248621. 

17-18. USNM 248617. 

19-20. USNM 248618. 

21-23. USNM 248620. 

24. USNM 248619. 

25-30. Juveniles sp.

25-27. USNM 248622. 

28-30. USNM 248623.

31-35. Paranannites slossi (Kummel and Steele). 

31-32. USNM 248624.

33. Suture line (x9) of USNM 248624. 

34-35. USNM 248625.

36-38. Metussuria waageni (Hyatt and Smith). 

36-37. USNM 248609.

38. Suture line (x6) of USNM 248609. 

39-42. Lanceolites compactus Hyatt and Smith. 

39-40. USNM 248611. 

41-42. USNM 248610

43. Suture line (x3) of USNM 248610.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1121-BPLATE2

41 42

PARANANNITES, METUSSURIA,LANCEOLITES,AND JUVENITES
PLATE 3

[All figures natural size]

Lower Triassic (Smithian) ammonites from USGS Mesozoic locality M5027, Upper Chulitna district, Alaska.

FIGURES 1-4. Euflemingites cirratus (White).

1. USNM 248628.

2. USNM 248627.

3. USNM 248626.

4. Suture line (xlO) of USNM 248626.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1121 -B PLATE3

EUFLEMINGITES

GPO689-143