from the Western 

of the United

GEOLOGICAL SURVEY P R® BES&lON AL PAPER 1057
Early Triassic 

Terebratulid Brachiopods 

from the Western Interior 

of the United States

By PETER R. HOOVER

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1057

Description and illustration of five species of 

terebratulid brachiopods, and discussion of their 

distribution and developmental and evolutionary history

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

Hoover, Peter R.

Early Triassic Terebratulid Brachiopods from the Western Interior of the United States

(Geological Survey Professional Paper 1057)

Bibliography: p. 19

Includes index

Supt. of Docs. No.: I 19:16:1057

1. Terebratulida, Fossil. 2. Paleontology Triassic. 3. Paleontology The West.

I. Title. II. Series: United States Geological Survey Professional Paper 1057

QE797.T29H66 564'.8 77-608314

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

Washington, D.C. 20402 

Stock Number 024-001-03182-5
CONTENTS

Abstract .......................

Introduction ....................

Previous work................

Present study ................

Acknowledgments ............

Fossil localities cited in this report. ....

Stratigraphic setting of the brachiopods 

Faunal relationships. ..............

Biostratigraphic implications........

Systematic paleontology............

Family Dielasmatidae..........

Subfamily Zugmayeriinae . . . 

Portneufia, n. gen. ....

Page

	Systematic paleontology Continued 

1 Family Dielasmatidae Continued 

1 Subfamily Dielasmatinae. . . .

1 Rhaetina Waagen .....

3 Family Terebratulidae .........

3 Subfamily Plectoconchiinae. .

3 Vex, n. gen. .........

4 Family Cryptonellidae .........

6 Subfamily Cryptacanthiinae .

6 Obnixia, n. gen. ......

7 Family Zeilleriidae ............

7 Periallus, n. gen. .........

7 References cited. .................

7 Index .........................

Page

9

9

9

11

11

11

17

17

19

21

ILLUSTRATIONS

	[Plates follow index]

PLATE 1. Portneufia, Rhaetina, and Vex.

2. Obnixia, Plectoconcha, and Vex.

3. Obnixia.

4. Periallus.

FIGURE 1. Index map showing locations of collections cited in this report ..................................................

2. Generalized correlation chart of Lower Triassic (Scythian) stratigraphic units in parts of the western interior of the United States.

3. Scattergram of dimensions of Obnixia thaynesiana (Girty) from southeastern Idaho and southeastern California . ............

4. Scattergram of dorsal valve length and loop length of Obnixia thaynesiana (Girty) from southeastern California .............

5. Scattergram of dorsal valve width and loop width of Obnixia thaynesiana (Girty) from southeastern California ..............

6. Scattergram of loop length and length of ascending lamellae of Obnixia thaynesiana (Girty) from southeastern California ......

7. Scattergram of loop length and distance to crural processes of Obnixia thaynesiana (Girty) from southeastern California .......

8. Thirty-five parallel serial sections of a paralectotype specimen of Obnixia thaynesiana (Girty) from southeastern Idaho ........

Page

2

5

12

13

13

14

14

16

TABLE

TABLE 1. Measurements of dorsal valve and loop parameters for a simulated ontogenetic series of Obnixia thaynesiana (Girty), from 

southeastern California ......................................................................

Page

13

EARLY TRIASSIC TEREBRATULID BRACHIOPODS FROM THE 

WESTERN INTERIOR OF THE UNITED STATES

By PETER R. HoovER1

ABSTRACT

This study of five species of terebratulid brachiopods from Lower 

Triassic marine rocks of the western interior of the United States is based 

entirely on existing museum collections. New genera and species described 

in this paper are: Portneufia episulcata, n. gen. and n. sp. (Dielasmatidae); Rhaetina incurvirostra, n. sp. (Dielasmatidae); Vex, n. gen. (type 

species: Terebratula semisimplex White) (Terebratulidae); Obnixia, 

n. gen. (type species: Terebratula thaynesiana Girty) (Cryptonellidae); and 

Periallus woodsidensis, n. gen. and n. sp. (Zeilleriidae). The developmental history of the cryptacanthiine Obnixia thaynesiana is discussed in 

detail on the basis of studies of exceptionally well preserved silicified material. The terebratulids here described are endemic elements of the poorly 

known Early Triassic shelly fauna. Although they clarify evolutionary 

changes across the eral boundary, their closest associations are with Mesozoic, rather than Paleozoic faunas. Although knowledge of the associated 

fauna is meager, the brachiopods themselves can be used as the basis of a 

crude biostratigraphic zonation suitable for correlation.

ABTOpeOepax

OriHcaHO H o6cy>KfleHO FIHTB BHHOB Tepe6paxy6paxHonofl HS MOPCKHX

sanaflHbix paftOHOB BHyxpeHHeft 

CoeflHHeHHbix QlTaTOB. K STHM xaKcoHaM OTHOCHTCH Portneufia episulcata, HOBblft pOfl H BHfl 

(Dielasmatidae), Rhaetina incurvirostra, HO- 

(Dielasmatidae), Vex, HOBbift pofl (THBHfl: Terebratula semisimplex White) 

(Terebratulidae), Obnixia, HOBHft pofl (THIIOBOft BHfl: Terebratula thaynesiana Girty)(Cryptonellidae), Periallus woodsidensis, HOBblft 

pofl H BHfl (Zeilleriidae). Ha ocHOBanHH H3yTJBHHH HCKJiK^jHTejiBHO xopouio coxpaHHBiiieroca 

OKpeMHeHHOro Maxepnajia flexajiBHO

HCTOpHH paSBHTHa KpHFITaKaHTHHH Obnixia

thaynesiana. OriHcaHHbie Tepe6paTyjiH»=i

co6OH SHfleMiTJHbie sjieMeHTbi niioxo HSHH)KHeTpHaCOBOft paKOBHHHOft 4>ayHbl. 

XOTH OHH paS'bHCHHIOT 3 B OJIIOU HO H Hfaie H3M6H6HHH

na rpaHHue sp, OHH 6ojiee SJIHSKH K 

KHM, ^IBM K najieosoftCKHM <|>opMaM.

OCHOBaHO TOJIBKO H3 KOJIJieKIJHH, HMGIOIUeftCH B

Mysenx. XOTH snaHHH o conyTCTByrciUHX $aynax 

caMH 6paxnonoflBi Moryx SBITB 

oSocHOBaHHa rpySoro SHOCTpaTHrpa$H^ecKoro pac^JteneHHa, roflnoro nun Kop-

'Director. Paleontological Research Institution, Ithaca. N. Y.

INTRODUCTION

This study was designed to enhance the meager biostratigraphic data base for the Triassic of the Western United 

States. Marine strata are uncommon in the Lower Triassic 

of the western interior of the United States, and well-preserved fossils are rare. This situation has led to a basically 

lithostratigraphic approach in most previous geologic reconnaissance studies. Ammonites were recognized early as 

potential biostratigraphic indices (White, 1880), and the 

distributions of other relatively common mollusks, particularly the pelecypods, were later brought to bear on the problem. Even the ammonites, biostratigraphically the most useful Early Triassic faunal elements, are quite provincial 

(Dagys, 1974), and correlations across the great distances 

separating their rare occurrences commonly have been quite 

subjective (Silberling and Tozer, 1968). During the last 20 

years, our knowledge of the stratigraphic range of the conodonts has been extended across the Permian-Triassic boundary, and conodonts now show great potential for Triassic 

biostratigraphic zonation. The contribution of this report to 

the knowledge of Early Triassic terebratulid brachiopods 

not only adds to our understanding of the organisms themselves, but also increases their usefulness in the Lower 

Triassic.

PREVIOUS WORK

Early Triassic terebratulid brachiopods, rare in the western interior of the United States, usually occur monospecifically in bands or zones. Thus, published descriptions rarely 

cover a diverse terebratulid assemblage. The first descriptions (White, 1880), from a section in southeastern Idaho 

(fig. 1, loc. 44), included no illustrations, but were repeated 

later with figures (White, 1883). Of the two forms discussed, 

only Terebratula semisimplex was illustrated. The other, 

cited as Terebratula augusta Hall and Whitfield, was 

neither described nor illustrated, and White was dubious 

about his identification. His specimens of T. augusta 

(USNM 8191) are preserved at the USNM (U.S. National 

Museum of Natural History, of the Smithsonian Institution) 

in Washington, D.C. Although they are too fragmentary 

and poorly preserved to identify with any terebratulids de-
TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

125° 120C 115° 110°

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FIGURE 1. — Index map showing locations of collections cited in this report.

scribed here, they may easily be distinguished from types of 

T. augusta Hall and Whitfield (USNM 12548a,b) by their 

weaker beak ridges, larger size, and lack of a prominent 

median septum. Nearly 50 years elapsed before publication 

of the next report describing Early Triassic terebratulids. 

Girty (1927) described a rhynchonellacean, two spiriferinaceans, and Terebratula thaynesiana. Types of T. 

thaynesiana also come from southeastern Idaho (fig. 1,

loc. 21). Newell and Kummell (1942) included brief descriptions and illustrations of a form, referred to Terebratula margaritowi Bittner, from the Dinwoody Formation 

at several localities in southeastern Idaho and southwestern 

Montana. Closely spaced serial sections of forms used by 

Newell in making this identification suggest they are identical with Periallus woodsidensis, n. gen., n. sp., and are not 

dielasmatids as heretofore supposed (Dagys, 1965, p. 137).
FOSSIL LOCALITIES CITED IN THIS REPORT

PRESENT STUDY

Collections of Triassic marine fossils housed at several institutions were examined, and all identifiable North American Early Triassic brachiopods were brought to the USNM 

for more intensive examination. Previous paleontological investigators did not examine the comparatively conservative 

terebratulids in detail, and internal characters now thought 

to be of primary taxonomic importance were rarely 

documented.

Most Early Triassic terebratulids are small (less than 

10 millimeters (mm) in maximum dimension) and are preserved as calcium carbonate. The only feasible accurate 

method of studying the internal details of such forms, other 

than laborious preparation with a needle, is to make threedimensional reconstructions based on closely spaced serial 

sections. The making of such sections is extremely time consuming and, unless considerable care is exercised in the 

maintenance of parallel sections, the results may be misleading. (See Westbroek, 1969, and Singeisen-Schneider, 1976.) 

Though this technique permits the use of calcareous specimens to document ontogenetic development and population 

variability of internal structures (for examples, see Baker, 

1972), it is not practical on a large scale when other methods 

can be used.

Many of the collections surveyed in this study include 

silicified specimens, which commonly may be removed from 

the calcitic matrix by etching with dilute acids. In the process, structures of extreme delicacy may be revealed, as 

shown in the specimens of Obnixia thaynesiana (Girty) from 

locality 37 (pi. 3, figs. 1-13).

Through the combined use of several preparation techniques, topotypic material of previously described North 

American Early Triassic terebratulids has been studied in 

detail. Both ontogenetic development and population variation have been documented for Obnixia thaynesiana 

(Girty). The study shows that, rather than two very 

generalized terebratulids in the North American Lower 

Triassic, there are at least five endemic species that have 

taxonomically and functionally distinctive internal skeletal 

elements. These fossils are not only diagnostic of the strata 

in which they occur, but they also illustrate, in a single organic group, the nature of evolutionary links across an era 

boundary of prime importance.

ACKNOWLEDGMENTS

The studies leading to this report were made during 

tenure of a National Research Council Postdoctoral Fellowship, held at the U.S.G.S. (U.S. Geological Survey) in Washington, B.C. The writer and this report have materially 

benefitted from discussions with and critical review byj. M. 

Berdan, G. A. Cooper, J. T. Dutro, Jr., R. E. Grant, N. J. 

Silberling, F. G. Stehli, and B. R. Wardlaw. Illustrations 

were in part drafted by Elinor Stromberg, of the U.S.G.S. 

Photographic services were provided by R. H. McKinney, 

H. E. Mochizuki, and Kenji Sakamoto of the U.S.G.S. and 

by G. A. Cooper of the Smithsonian Institution, Washington, D.C. Russian translation of the author's abstract was 

kindly provided by Dr. M. A. Semikhatov, of the Geological 

Institute of the Academy of Sciences, Moscow, U.S.S.R.

FOSSIL LOCALITIES CITED IN 

THIS REPORT

The material studied for this report comes from several 

different sources. Most specimens were collected by 

U.S.G.S. geologists during investigations of the phosphate 

reserves of the western interior of the United States, around 

the turn of the century. (See fig. 1 and the list of fossil localities below.) Because those phosphate deposits are of late 

Paleozoic age, many of the fossil collections bear that designation, despite their derivation from rocks now known to be 

of Triassic age.

Locality numbers having the suffix "PC" are from the 

U.S. Geological Survey's upper Paleozoic catalog, kept in 

Washington, D.C. Those having the suffix "(Green)" belong 

to G. H. Girty's old upper Paleozoic catalog at the U.S.G.S. 

in Washington, D.C. Numbers without prefix or suffix are 

from the Survey's Mesozoic catalog, also in Washington, 

D.C. Those having the prefix "M" come from a similar 

Mesozoic catalog at U.S.G.S. offices in Menlo Park, Calif. 

Those having the prefix "USNM" are held by the U.S. National Museum of Natural History, which also houses the 

Washington, D.C., collections of the U.S.G.S. All type, 

figured, and measured specimens from this report have been 

assigned USNM catalog numbers and are in the USNM 

Paleobiology Collections in Washington, D.C.

Locality information on specimen labels has been supplemented by information on original register file cards, field 

labels, maps and notebooks, and more recent geologic and 

topographic maps. Such additions appear in brackets.

Map index 

number

(see fig. 1)

Original

locality 

number

Description of locality, stratigraphic assignn 

of collection

collector, and ye

Idaho, Caribou County, Snowdrift 1:24.000 quad., SE corner of 

NEViSE'^NEW sec. 27, T 9 S., R. 45 E. [Peak at alt 8,640-8,660 

ft.] Woodside Formation. [G. R.] Mansfield and [G. H.] Girty, 

Aug. 31, 1911

Idaho [Caribou County, Lane's Creek 15-min quad ]; sec. 1, T. 7 S., 

R 44 E [Probably] Thaynes Formation. [G. R.] Mansfield, 1912.

Idaho [Caribou County, Lane's Creek 15-min quad.; section unknown] T 6 S , R. 44 E. [Probably] Thaynes Formation. [R. W.] 

Richards, 1912.

Idaho [Bingham County, Yandell Springs 15-min quad.; NW'/iSW'/i 

sec 31. T. 3 S.. R. 38 E.]. Portneuf Limestone [Member] of 

Thaynes Formation [G. R.] Mansfield and [G. H.] Girty, Aug. 27, 

1913.

Idaho [Bingham County, Higham Peak 7y2 -min quad., SWViSW'/i 

sec. 25, T. 3 S., R. 37 E.]. Portneuf Limestone [Member of 

Thaynes Formation]. [G. R ] Mansfield and [G. H.] Girty, Aug. 28, 

1913.

Idaho [Bingham County. Higham Peak 7V4-min quad.]; low spur, 

east 'scarp [SW'/iSW 1/* sec. 2, T. 3 S . R 37 E.]. Portneuf Limestone [Member of Thaynes Formation]. [G. R.] Mansfield and 

[G. H.]Girtv . Sept. 5, 1913.

Idaho [Bingham County, Yandell Springs 15-min quad , NW/4SW/4 

sec. 31, T. 3 S., R. 38 E.]. Portneuf Limestone [Member of 

Thaynes Formation]. [?] Merritt and [G H.]Girty, Sept. 1913.

Idaho, Bingham County, Higham Peak 7 l/2 -min quad.. SE^NW'/i 

sec. 24, T. 3 S., R. 37 E.]. Portneuf Limestone [Member of 

Thaynes Formation]. [G R.] Mansfield and [G H.] Girty, Aug. 29, 

1913.

Idaho [Bingham County, Yandell Springs 15-min quad.]; 775 ft 

southwest of top of hill, [SW'/iNW'/i sec. 1. T 4 S., R. 37 E. 

Probably Thaynes Formation. G. R.] Mansfield and [G. H.] Girty, 

Sept. 6, 1913.
TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

Map index Original

number locality

(see fig. 1) number

Description of locality, stratigraphic assignment, collector, and year 

of collection

10 1315-PC Idaho, Bingham County, Yandell Springs 15-min quad.]; SEViSE'/i 

sec. 36, T. 4 S., R. 37 E. [Probably Thaynes Formation.) (G. R.] 

Mansfield and [G. H.] Girty, Aug. 25, 1918.

11 13S6-PC Idaho [Caribou County, Jeff Cabin Creek 7'/2-min quad.]; sec. 24, 

T. 5 S., R. 37 E. "Ross Fork [Limestone Member" of Thaynes 

Formation]. G. R. Mansfield, July 26, 1913.

12 18017-PC Nevada, Elko County, Carlin [15-minJ quad.; NEV4 sec. 16, T. 31 

N., R. 52 E. [Railroad District]. Permian of J. F. Smith and 

K. B. Ketner. [J. F.] Smith and [K. B.] Ketner, 1958.

13 614a (Green) Utah [Washington County, probably La Verkin No. 4 NW 7'/amin quad.], canyon east of Toquerville on road to Virgin City. 

[Probably Moenkopi Formation.] J. E. Whitfield, Oct. 3, 1885.

14 961 (Green) Arizona [Mohave or Coconino County, Fredonia NE 7'/2-min 

quad.], 10 mi south-southwest of Kanab, Utah. [Probably Moenkopi Formation); thin limestones interbedded in reddish-brown 

arenaceous shales. C. D. Walcott and party, Sept. 6, 1882.

15 3769 (Green) Wyoming [Lincoln County, Cokeville 30-min quad.]; center of sec. 

32, T. 23 N., R. 118W. Fork of Rock Creek, 7 Vt mi north of Nugget. Thaynes Formation. A. C. Veatch, July 27, 1905.

16 731S (Green) Idaho [Bear Lake County, Montpelier Canyon 7V4-min quad., 

SWWNEVi] SE'/i sec. 6, T. 13 S., R. 45 E., Waterloo Mountain. 

Questionable basal [part of] Woodside Formation, but structurally 

very complex. C. L. Breger, June 16, 1909.

17 7376 (Green) Idaho [Bear Lake County, Montpelier 7 1/2-min quad.]; sec. 1, 

T. 13 S., R. 44 E.; [measured section in] Montpelier Canyon [just 

east of town of Montpelier]; Thaynes Formation [about 717 ft 

above the base and 1,565 ft below the top of the unit there 

exposed]. [C. L.] Breger, June 9, 1909.

18 7S90(Green) Idaho [Bear Lake County, Montpelier 7 1/2-min quad.; sec. 2, T. 13 

S., R. 44 E.; measured section in] Montpelier Canyon [just east 

of town of Montpelier]. Thaynes Formation (about 1,849 ft 

above the base and 433 ft below the top of the unit there exposed]. 

[C. L.] Breger and [G. H.] Girty, June 11, 1909.

19 7S95 (Green) [Same as 7390 (Green)]; about 3 mi east of the town of Montpelier, 

on the north side of the road. [About 418 ft above the base and 

1,864 ft below the top of the unit there exposed]. G. H. Girty, 

June 11, 1909.

20 7397 (Green) [Same as 7390 (Green). Same horizon as 7376 (Green).] C. L. Breger 

andG. H. Girty, June 11, 1909.

21 7406 (Green) [Same as 7390 (Green). About 2072 ft above the base and 210 ft 

below the top of the unit there exposed; probably equivalent of 

Portneuf Limestone Member of Thaynes Formation.] C. L. 

Breger, June 5, 1909.

22 7409 (Green) [Same as 7S90 (Green).]C. L. Breger, June 7, 1909.

23 7431 (Green) [Probably same as 7390 (Green).] Near base of Thaynes Formation. 

[C. L.] Breger and [G. H.] Girty, June 10, 1909.

24 7435 (Green) Idaho [Bear Lake County, Montpelier 7'/j-min quad.; approx. 

sec. 13, T. 15 S., R. 44 E.]. Thaynes Formation, [equivalent 

stratigraphically to 7397 (Green)]. C. L. Breger, Sept. 1909.

25 7444 (Green) Wyoming [Lincoln County, Montpelier, Idaho-Wyoming 30-min 

quad.; NE'/iSW'/iSE'/i sec. 30, T. 27 N., R. 119 W.]. Thaynes 

Formation. G. H. Girty, July 6, 1909.

26 7466 (Green) Wyoming [Lincoln County, Montpelier, Idaho-Wyoming 30-min 

quad.; SE'/iSW'/iSW'/i sec. SO, T. 27 N., R. 119 W.]; west 

face of Sublette Range, north of Raymond Canyon. Thaynes Formation. G. H. Girty, June 7, 1909.

27 7470 (Green) Wyoming [Lincoln County, Montpelier, Idaho-Wyoming 30-min 

quad.; NE corner of SE'/iNE'/iNE'/i sec. 6, T. 26 N., R. 119 

W.]; Thaynes Formation. G. H. Girty, July 2, 1909.

28 7478 (Green) Utah [Rich County, Woodruff 7 1/2-min quad.]; Woodruff, branch 

hollow of Twelve Mile Creek south of Road Hollow. Thaynes 

Formation. C. L. Breger, Aug. 24, 1907.

29 7717 (Green) Utah [Morgan County, Devil's Slide 7 1/2-min quad.]; north side of

Weber Canyon, 1 mi west of Devil's Slide. [Probably Moenkopi

Formation.]G. H. Girty, Sept. 15, 1911. 

SO 7758 (Green) Utah [Iron County, Kanarraville 7 1/2-min quad.]; Vi mi east of

Kanarra. [Probably Moenkopi Formation.] [H.] Graff, July 18,

1907.

31 7787 (Green) Utah [Washington County, La Verkin No. 4 NW 7'/2-min quad.], 

near center, sec. 18, T. 42 S., R. 12 W.; about 6 mi southwest of 

Virgin City. Lower limestone [part] of Moenkopi Formation, 

SCO ft above base of unit. [J. B.] Reeside, Oct. 3, 1919.

32 7813 (Green) Idaho [Bingham County,] Crane's Flat 15-min quad.; near S Vi corner 

[?], sec. 2, T. 4 S., R. 41 E.; about 13 mi north and 5'/2 mi west of 

Henry, Idaho. Thaynes Formation. [P. V.] Roundy and [G. R.] 

Mansfield, Aug. 1916.

33 7825 (Green) Idaho [Caribou County, Upper Valley 7'/2-min quad.]; SEViNE'/4 

sec. IS, T. 7 S., R. 44 E. [Probably Thaynes Formation.] R. W. 

Richards, 1912.

34 7835 (Green) Idaho [Caribou County,] Lane's Creek 15-min quad.; near SE corner, 

sec. 5, T. 6 S., R. 4S E.; about 5 mi east and a little north of 

Henry, on a little knob at base of the 7037 ft peak. Upper [part 

of the] Thaynes Formation. [G. R.J Mansfield and [P. V.] Roundy, 

July 10, 1915.

35 7879(Green) Idaho [Bingham County,] Crane's Flat 15-min quad.; SE'/i sec. 9, 

T. 4 S., R. 40 E. "Ross Fork Limestone [Member" of Thaynes 

Formation]. G. R. Mansfield, 1923.

Map index Original

number locality

(see fig. 1) number

Description of locality, stratigraphic assignment, collector, and year 

of collection

36 7885 (Green) Nevada [Clark County, probably in the Moapa 15-min quad.]; 

"Valley of Fire," Muddy Mtns., l/4 mi east of White Basin fault, 

l/4 mi south of Old Arrowhead Road. Moenkopi Formation in fault 

block. C. R. Longwell, JulyS, 1924.

37 7897 (Green) [California, San Bernardino County, Ivanpah and Mescal Range 

15-min quads., near center, sec. 32, T. 15V4 N., R. 14 E.]; 1 mi 

northwest of Kokoweef Peak. [Probably Moenkopi Formation.] 

D. F. Hewett, Oct. 28, 1926.

38 501S Idaho [Bear Lake County, Montpelier 7'/2-min quad.; approx. 

sec. 13, T. 15 S., R. 44 E.]; from slide on east side of gulch east 

of Hot Springs. [Probably Thaynes Formation.] F. B. Weeks, 

Sept. 27, 1907.

39 18595 Utah, Washington County, [probably in the Zion National Park 

SO-min quad.; Kolob Section S.;] Dry Creek Section. Virgin Limestone [Member of Moenkopi Formation]. H. E. Gregory, Sept. 

22, 1940.

40 M-108 Utah [Millard County, Cowboy Pass 15-min quad.]; sees. 18 and 

19, [T. 16 S., R. 16 W.]; Confusion Range. Measured section, 

about 870 ft above base of Triassic section [probably Moenkopi 

Formation]. [C. A.) Repenning and [R. K.] Hose, Oct. 19, 1955.

41 M-853 Idaho, Caribou County, Upper Valley 7'/2-min quad.; NE'/iNW'/4 

sec. 13, T. 7 S., R. 44 E.; on east side of drain between Bacon and 

Timothy Creeks. Upper [part of] Portneuf Limestone Member 

of Thaynes Formation, about 100 ft above the top of the Lanes 

Tongue [of Ankareh Formation] redbeds. R. Rioux and J. Dyni, 

1959.

42 USNM 9342 Utah [Washington County], 9 mi southwest of St. George. Virgin 

Limestone Member of Moenkopi Formation. A. A. Graffam, 

[Date unknown.]

43 USNM 9343 Utah, Kane County, Moenkopi Formation (?). [Probably collected 

by] Fawcett. [Date unknown.]

44 USNM9S44 Idaho, [Bingham County;] about 65 mi north of the Utah line, 

18 mi west of the Wyoming line, and 5 mi west of Gray's Lake. 

[Probably Portneuf Limestone Member of Thaynes Formation.] 

A. C. Peale, 1877.

STRATIGRAPHIC SETTING OF 

THE BRACHIOPODS

An inherent disadvantage in a study of museum collections is that the investigator must rely almost entirely upon 

the judgement of previous field workers for the geographic, 

stratigraphic, and temporal annotations of the collections. 

In an area of rapid lateral facies change and rare diagnostic 

Early Triassic fossil horizons, such as the North American 

western interior, the approach to stratigraphy is lithic. 

Facies and (or) formation boundaries are commonly diachronous in such a situation, so that it is not surprising that 

formation names have proliferated or that the formal applicability of these names is regionally restricted.

The brachiopods discussed here were collected from the 

Woodside, Dinwoody, Thaynes, and Moenkopi Formations 

and commonly occur in thin, monospecific bands or zones, 

isolated from one another and from most other diagnostic 

fossils. The age of these units and their regional interrelationships are unclear. McKee and others (1959) produced a 

generalized correlation chart for Triassic stratigraphic units 

in the United States. Pertinent parts of that chart appear 

here as figure 2. The Woodside Formation, originally defined (Boutwell, 1907) in the Park City district, northeastern 

Utah, was later extended to northern Utah, western Wyoming, and southwestern Montana (Kummel, 1954). Beds in 

the Confusion Range in west-central Utah, originally referred to the Woodside (Newell, 1948), were reassigned to 

the Thaynes Formation (Hose and Repenning, 1959). The 

so-called "Mackentire Tongue" of the Woodside Formation, 

defined in Duchesne County, Utah, is of demonstrable
IDAHO

Centraleastern

Portneuf Limestone 

Member of Thaynes 

Formation

Thaynes Formation

PortneufX^^ ~ 

Limestone N^

Unit E1 

Sandstone and 

limestone

Unit D2 

Black 

limestone

Unit C 2 

Tan silty 

limestone

Unit B 2 

Black 

limestone

Unit A2 

Lower 

limestone

Dinwoody 

Formation

Southeasternmost

Portneuf Limestone 

Member of Thaynes 

Formation

~- Lanes Tongue-^^ 

of Ankareh 

Formation

Thaynes 

Formation

Woodside 

Formation\

Dinwoody ^^" 

Formation

WYOMING

Centra I - 

western

Thaynes 

Limestone

Woodside 

Formation

Dinwoody 

Formation

MONTANA

Southwestern

?

Thaynes 

Formation

Woodside 

Formation

Dinwoody 

Formation

UTAH

Northwestern

Ankareh 

Formation 

(lower part)

Thaynes 

Limestone

Woodside 

Formation

SW SE

Moenkopi 

Formation 

(lower part)

Northeastern

Moenkopi 

Formation 

(lower part)

NEVADA

South NE

Moenkopi Formation 

(lower part)

Marine shal and limestone

1 ''Fort Hall Member" of Thaynes Formation.

2*v Ross Fork Limestone Member" of Thaynes Formation.

FIGURE 2. —Generalized correlation chart of Lower Triassic (Scythian) stratigraphic units in parts of the western interior of the United 
TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

Permian age (McKelvey and others, 1956; 1959), so that in 

places, the Permian-Triassic boundary is within the Woodside. The Woodside commonly overlies Permian units referable to the Phosphoria and Park City Formations and 

underlies the Triassic Thaynes Formation (or Limestone or 

Group). It tongues out westward in southeastern Idaho and 

southwestern Montana into the Dinwoody Formation 

(Kummel, 1954).

The Dinwoody Formation, originally defined (Condit, 

1917) in the Wind River Mountains, Wyo., commonly overlies various members of the Park City, Shedhorn, and Phosphoria Formations (Permian) and may be overlain by 

Woodside, Thaynes, or younger units. The Dinwoody 

generally appears to be a lateral equivalent of the Woodside 

in southeastern Idaho, southwestern Montana, and western 

Wyoming (Kummel, 1954).

The Thaynes Formation was originally defined in the 

Park City district, Uinta Mountains, Utah (Boutwell, 1907), 

where it overlies the Woodside and underlies the Ankareh 

Formation. In southeastern Idaho, the Thaynes was divided 

into three units (Mansfield, 1916; 1920), now recognized as 

members (Kummel, 1954): the basal "Ross Fork Limestone 

Member," 2 the middle "Fort Hall Member," 3 and the upper 

Portneuf Limestone Member. The Thaynes is recognized in 

southeastern Idaho, northeastern Utah, and western Wyoming and is apparently equivalent to a part of the Moenkopi 

Formation in parts of southern Utah, Arizona, Nevada, and 

California.

The Moenkopi Formation, defined in the Grand Canyon 

region, Arizona (Ward, 1901), is a unit of Early and 

Middle(?) Triassic age in Arizona, Colorado, California, 

Nevada, and southern Utah. It appears to be equivalent in 

age to all of the Thaynes and parts of the Woodside in 

Idaho, Wyoming, and Utah.

FAUNAL RELATIONSHIPS

Early Triassic brachiopods are rare worldwide. In 

North America, described terebratulids of Early Triassic 

age have been limited to the genus Terebratula [sensu lato], 

and have been formally assigned to but three species: 

T. margaritowi Bittner, T. semisimplex White, and 

T. thaynesiana Girty. Specimens assigned to T. augusta 

Hall and Whitfield (White, 1880; 1883) (USNM 8191)-but 

never described or figured—are too fragmentary to permit 

any taxonomic assignment other than "not T. augusta Hall 

and Whitfield." In the 35 years since the last of these descriptions was published, it has become better understood 

that the taxonomic position of such forms must be based on 

characteristics other than external form and size. Dagys 

(1974), in a summary of his extensive studies of the-world 

distribution of Triassic brachiopods, cited only a few genera 

of Early Triassic brachiopods, among which are three terebratulids: tSulcatmella Dagys, Fletcherithyris Campbell, 

and Plectoconcha Cooper, the last typically a Late Triassic 

genus. His generic identifications of North American forms

"Units A, B, C, and D of fig. 2. 

"Unit E of fig. 2.

suggest he has had no opportunity to study pertinent material firsthand but has had to rely heavily on the small body 

of extant literature.

In several Early Triassic brachiopod assemblages, which 

include rhynchonellaceans, spiriferinaceans, and athyridaceans, Dagys (1974, p. 292) identified the terebratulid 

Fletcherithyris margaritowi Bittner as a globally cosmopolitan element. He recognized it in collections from the upper 

Induan (Dienerian) of Idaho and the Olenekian (Smithian 

and most of the Spathian) of North America, from 

Primor'ye of the northeast U.S.S.R. just north of Vladivostok, from Japan, from Mangyshlak of the eastern shore of 

the Caspian Sea, Kazakhstan, U.S.S.R., and from the 

Balkans. Although comparative material from many of 

these areas was not available to me, Dagys' identifications of 

North American material, at least, are suspect. Specimens 

in the present study externally similar to Fletcherithyris 

Campbell may be assigned confidently either to Rhaetina 

Waagen, which lacks the characteristic dental plates of 

Fletcherithyris, or to Periallus, new genus, a zeilleriid, having the distinctive loop of that family. Similarly, internal 

characters of a form assigned by Dagys to Plectoconcha 

Cooper [T. semisimplex White] require erection of a new, 

albeit plectoconchiine, genus. A superficial cosmopolitanism may exist in Early Triassic terebratulids, in that morphologically similar, but not genetically identical forms, 

evolved in geographically separated areas. Our knowledge 

of the range of variation in suprageneric groups of terebratulids in the Early Triassic is so poor that I cannot state 

with confidence that homeomorphic pairs such as Fletcherithyris-Rhaetina, or Fletcherithyris-Periallus are not 

more closely related than at the generic level. Forms able to 

survive the mysterious rigors of the Permian-Triassic transition must have been generalized, so that they could exploit 

marginally favorable environments. The broad genetic base 

that made possible such extensive external homeomorphy 

may also have been responsible for the variety of internal 

skeletal arrangements that are considered of taxonomic significance at the generic level.

North American Early Triassic terebratulids occupy 

pivotal positions in several phyletic lineages. They include 

the oldest known representatives of the Family Zeilleriidae, 

the Subfamilies Zugmayeriinae and Plectoconchiinae, and 

the genus Rhaetina, and the youngest reported representatives of the Cryptacanthiinae. Paleozoic antecedents of most 

of the forms are difficult to determine, and the overall aspect of the brachiopod fauna is Mesozoic.

BIOSTRATIGRAPHIC IMPLICATIONS

Only a small number of the fossil localities covered by this 

report are well-defined stratigraphically—most collections 

were made more than 50 years ago when the regional 

stratigraphy was neither so well known nor so finely subdivided as it is today. Little matrix was collected with the 

macrofossils. Most commonly, only that rock adherent to 

individual fossil specimens was retained. Because of time 

limitations, no field investigations were possible in the
SYSTEMATIC PALEONTOLOGY

present study. Some conclusions of a biostratigraphic 

nature, however, are possible, on the basis of the distributions of the terebratulids themselves.

Three of the terebratulid species, Portneufia episulcata, 

n. gen., n. sp., Rhaetina incurvirostra, n. sp., andPeriallus 

woodsidensis, n. gen., n. sp., are quite rare. The first two 

were recovered from the Portneuf Limestone Member of the 

Thaynes Formation, but each is so uncommon, and our 

knowledge of the stratigraphic position of the collecting 

localities is so poor, that it is difficult to determine whether 

they are limited to that unit. Periallus woodsidensis has not 

been recognized in any of the collections from the upper 

part of the Thaynes Formation. It is probably limited to the 

Woodside and Dinwoody Formations and the "Ross Fork 

Limestone Member" 4 of the Thaynes Formation. Obnixia 

thaynesiana (Girty), the most widespread form here described, has been recovered from the Thaynes and Moenkopi Formations from southeastern Idaho to southeastern 

California (fig. 1), but, with one possible exception, it has 

not been recovered stratigraphically below the Meekoceras 

ammonite zone which defines the base of the Thaynes Formation. At locality 16, a form questionably referred to O. 

thaynesiana is associated with P. woodsidensis. This locality 

is in a structurally complex region, and the formation assignment made in the field (basal(?) part of the Woodside 

Formation) may be in error. On the basis of all other occurrences in this study, the only unit in which these terebratulids could occur is the "Ross Fork Limestone Member" of the 

Thaynes Formation. Girty (in Mansfield, 1916, p. 39; in 

Mansfield, 1920, p. 50) recognized Terebratula semisimplex White as an index of the Portneuf Limestone Member 

of the Thaynes Formation. The distribution of Vex semisimplex (White) revealed in this study bears out his conclusions.

SYSTEMATIC PALEONTOLOGY

The use of descriptive terms such as anterior, posterior, 

ventral, dorsal, mesial, distal, length, width, height, and 

thickness, follows that of Williams and Rowell (1965). 

Several other terms are introduced to denote morphologic 

features of potential taxonomic value.

Anterior separation is the horizontal distance between the 

anterior extremities of the loop, whether it be terebratuliform ("short") or terebratelliform ("long"). This measure 

has little application in early developmental stages. Loop 

length is measured from the most posterior point on the 

dorsal umbo to the most anterior point of the loop. Loop 

width and loop thickness are maxima and are measured in a 

plane normal to the longitudinal axis of the loop. Length of 

the ascending lamellae or length of the transverse band is 

measured from the most posterior part of the ascending 

lamellae or transverse band to the anterior extremities of the 

loop. Distance to crural processes is measured along the 

longitudinal axis of the loop, from the most posterior point 

on the dorsal umbo to an imaginary line connecting the two 

crural points.

•Units A, B, C, and D of fig. 2.

Several subscripts are used to qualify measurements. The 

subscript "e" indicates that the measurement was estimated 

and is probably correct only to the nearest millimeter. The 

subscript "c" indicates that the specimen was crushed in 

such as way as to render the measurement less than representative; if "e" is also present, the measurement was estimated, to correct this deficiency. The subscript "b" indicates that the specimen in question is broken, and it indicates that a part of the specimen necessary for the measurement is missing; this too may be accompanied by the subscript "e," indicating that the measurement was estimated. 

A measure across any structure having bilateral symmetry 

(for example, a measure of brachiopod hinge width), may 

be estimated by doubling the half measure, which equals the 

distance from the symmetry plane to the distal extremity. 

Use of this procedure is indicated by the subscript "h."

Order TEREBRATULIDA Waageii, 1883

Superfamily DIELASMATACEA Schuchert, 1913

Family DIELASMATIDAE Schuchert, 1913

Subfamily ZUGMAYERIINAE Dagys, 1963

Genus PORTNEUFIA, n. gen.

Etymology of name. — F. Portneuf = name of rock unit 

+ L. -ia = feminine suffix.

Diagnosis. — Dielasmatidae with falsifer crura and long 

loops, with inner hinge plates and convoluted anterior 

commissure.

Description.—Dielasmatids having subequally biconvex 

valves and suberect to erect ventral beak. Surface commonly 

smooth.

Ventral valve hinge area expanded in lateral view. Pedicle 

foramen medium sized, mesothyridid to permesothyridid. 

Subtriangular delthyrium closed apically by small, short, 

disjunct deltidial plates. Beak ridges faint; interarea curved, 

poorly defined.

Dorsal valve hinge region resected in lateral view, accommodating expanded part of opposite valve. Beak in lateral 

view thin, obtusely pointed in dorsal view.

Ventral interior has distinct pedicle collar and short 

dental plates. Hinge teeth short, tabular.

Dorsal interior with or without distinct cardinal process. 

Outer socket ridges very low; sockets shallow, roofed 

mesially by wide triangular outer hinge plates, which join 

ventral extremities of short inner socket ridges. Crura 

falsifer (sensu Dagys, 1974), with deep crural bases rising 

anteromesially of hinge plates as crural processes, descending anterodistally as keels, which may be supported apically 

by crural plates. Inner hinge plates present, variable. Low 

median myophragm developed. Loop with long descending 

and ascending lamellae, but anterior parts unknown.

Type species.—Portneufia episulcata, n. sp.

Occurrence. — Same as for species.

Comparison.—Portneufia is distinguished from both 

Adygelloides Dagys and Zugmayeria Waagen by the relatively complex convolution of its anterior commissure and its
TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

apparent terebratelliform loop and from Adygelloides, in 

particular, by its distinct inner hinge plates.

Discussion. —Portneufia represents the oldest known zugmayerine dielasmatid; the other two genera referable to the 

subfamily are known only from the Upper Triassic. The 

Paleozoic antecedents of Portneufia may have been forms 

like Dielasma King (s. s.), which are quite similar, but 

which bear septalial plates reaching the floor of the valve. A 

single specimen (USNM 242053; pi. 1, figs. 9, 10) best shows 

loop detail. It appears terebratelliform, but because the 

anterior parts are not preserved and because some forms (for 

example, Aulacothyroides Dagys and Anadyrella Dagys) 

that bear a glossothyropsiform mature loop are developmentally dielasmoid, it seems premature here to alter the 

above suprageneric designations.

Portneufia episulcata, n. sp.

Plate 1, figures 1-10

Etymology of name. — L. episulcata — episulcate.

Diagnosis. — Small episulcate Portneufia.

Description.— Medium-sized subequally biconvex shells, 

elongate oval to subtriangular in outline, having suberect to 

erect ventral beak. Anterior commissure episulcate to sulciplicate. Surface smooth, anteriorly marked by faint concentric growth lines.

Ventral valve symmetrically domed, posteriorly expanded 

in lateral view; steeply domed in anterior view. Mediumsized mesothyridid to permesothyridid pedicle foramen. 

Subtriangular delthyrium closed apically by small short disjunct deltidial plates. Beak ridges faint; interarea curved, 

poorly defined.

Dorsal valve in lateral view more steeply sloping anteriorly; having crescentic posteriorly resected hinge margins, 

accommodating expanded posterior part of opposite valve. 

Anteromesial slope faceted, only incipiently sulcate, produced anteroventrally as short curved tongue. Beak in 

lateral view thin, obtusely pointed in ventral view.

Ventral interior having distinct pedicle collar and short 

dental plates. Hinge teeth short, tabular, long axes oriented 

posteromesially, rounded points directed anteromesially; 

not markedly hooked. Muscle scars indistinct.

Dorsal interior has distinct bilobate cardinal process or 

simple apical pit. Outer socket ridges very low; sockets shallow, widely divergent anteriorly, roofed mesially by wide triangular outer hinge plates which join ventral extremities of 

short inner socket ridges; outer hinge plates sloping slightly 

dorsomesially. Crura falsifer (sensu Dagys, 1974): deep 

crural bases joined medially to outer hinge plates; crural 

bases rising anteromesially of hinge plates as high crural 

processes at about one-fourth valve length anterior to beak, 

descending anterodistally as keels, supported only apically 

by short crural plates. Narrow inner hinge plates present, 

variably oriented, separated mesially by thin gap. Long very 

low median myophragm extending anteriorly about onehalf valve length. Loop apparently about two-fifths width of

valve. Descending and ascending lamellae of loop slender: 

loop probably terebratelliform, but anterior parts not 

preserved.

Length 

(mm)

Width 

(mm)

Thickness 

(mm)

Dorsal

valve 

length

(mm)

Distance

to crural 

processes

(mm)

Loop 

width

(mm)

Locality 4:

USNM 242049 7.9 7.6 

USNM 242050 ...... 11.4

USNM 242051 15.1 10.9 

(holotype)

USNM 242052 ...... 14.4h

4.6

8.5

6.5

11.8

13.2

16.0.

3.0 

3.3

3.4 5.6h

Types. —Holotype: USNM 242051; figured paratypes: 

USNM 242049, 242053; measured paratypes: USNM 

242049, 242050, 242052.

Occurrence.—Portneufia episulcata has been recovered 

only from locality 4, in the Portneuf Limestone Member of 

the Thaynes Formation, on the Fort Hall Indian Reservation, Bingham County, Idaho (fig. 1). The horizon from 

which this sample was collected was originally assigned to 

the basal part of the Ankareh Formation, a name now restricted to a sandstone overlying the Thaynes Formation.

Comparison. —Portneufia episulcata is monotypic. It may 

be distinguished from other North American Early Triassic 

terebratulids by its episulcate anterior commissure and its 

distinctive dorsal cardinalia.

Subfamily DIELASMATINAE Schuchert, 1913 

Genus RHAETINA Waagen, 1883

Diagnosis. —Small to large dielasmatids with sulciplicate 

to rectimarginate anterior commissure, suberect to incurved 

ventral beak and epithyridid pedicle foramen. Septalial 

plates present; dental plates absent; crura infulifer; dorsal 

median septum low or absent.

Type species. — Terebratula gregaria Suess, 1854, Akad. 

Wiss. Wien, Math.-naturwiss. Kl. Denkschrift, v. 7, p. 42, 

pi. 2, figs. 13-15.

Occurrence.—Rhaetina was first described (as T. 

gregaria Suess) from the Kossenerschichten (Rhaetian) of the 

Eastern Alps. Since then, specimens have been reported 

from rocks ranging in age from Permian (Gemmellaro, 

1899) to Jurassic (Moisseiev, 1938), in Western and Central 

Europe: the Permian form has since been shown to belong to 

a distinct dielasmatacean family. R. incuririrostra, n. sp., is 

the first reported occurrence of the genus in North America.

Comparison.—Rhaetina may be distinguished from Adygella Dagys, Adygelloides Dagys, Aspidothyris Diener, 

Dinarella Bittner, Fletcherithyris Campbell, and Sulcatinella Dagys by its lack of dental plates, and from Coenothyris Douville, Cruratula Bittner, and Dinarella Bittner by 

its epithyridid pedicle foramen. Propygope Bittner has a 

broadly sulcate dorsal valve and markedly triangular 

outline.

Discussion.— Although Rhaetina is unknown in the 

Permian of North America, closely homeomorphic species
SYSTEMATIC PALEONTOLOGY

of Dielasma King and Fletcherithyris Campbell are reported 

from the Permian and Triassic, respectively (Cooper and 

Grant, 1976; Dagys, 1974). Specimens originally reported as 

Rhaetina lepton Gemmellaro (1899), have been shown 

(Stehli, 1962; Cooper and Grant, 1976) to be more properly 

assigned to the Family Heterelasminidae, as they lack outer 

hinge plates connecting the inner socket ridges and crural 

bases.

Khaetina incurvirostra, n. sp.

Plate 1, figures 11 24

Etymology of name.—L. incurvo = incurved + L. 

rostrum — beak.

Diagnosis.—Rectimarginate to incipiently uniplicate 

Rhaetina having an extremely incurved ventral beak.

Description.— Medium- to large-sized terebratulids having subequally biconvex valves; elongate oval in outline, 

with long incurved ventral beak and apparent rectimarginate anterior commissure. Surface smooth or marked by 

faint growth lines.

Ventral valve having large long extremely incurved beak; 

beak commonly extending over dorsal umbo for distance of 

several millimeters. Large epithyridid, anteriorly labiate 

pedicle foramen. Disjunct deltidial plates apically filling 

delthyrium; deltidial plates not visible externally, but lying 

between pedicle collar and exterior of dorsal umbo. Long 

dorsal pedicle collar extension, semicircular in cross section, 

visible in dorsal and posterior views. Beak ridges poorly 

developed.

Dorsal valve has sharp beak covered by incurved ventral 

beak. Evenly domed in lateral and anterior views.

Ventral interior has anteriorly elongate pedicle collar 

pressed tightly against deltidial plates, acting as peduncular 

trough or channel; posterior and lateral parts of collar relatively normally proportioned. Dental plates and dental 

ridges not developed. Muscle scars indistinct. Hinge teeth 

small, short, tabular, arising anteromesially, hooked 

dorsomesially.

Dorsal interior has small transverse bilobate cardinal process. Hinge sockets long, narrow, shallow. Thin outer socket 

ridges differentiated from valve wall, forming narrow secondary articulatory furrow distally; thin low inner socket 

ridges not appreciably overhanging sockets. Elongate triangular, mesially convex, anterodistally concave outer hinge 

plates arising at dorsal margins of inner socket ridges; 

ventromesially directed crura arising at junction of outer 

and inner hinge plates, extending only ventrally therefrom. 

Inner hinge plates ventromesially convex, anterodistally 

concave, joining dorsal margins of crura to valve floor. 

Median ridge very low, extending about one-half valve 

length. Crura infulifer to lobothyroid; crural processes long, 

broad; points acute, located anterior to anterior ends of 

hinge plates, closely appressed mesially. Loop terebratuliform: short, extending less than one-half valve length; narrow, about one-fourth valve width at anterior extremities. 

Transverse band closely appressed and almost parallel to 

descending lamellae.

Total Total

length width

(mm) (mm)

Total

thickness

(mm)

Dorsal 

valve 

length 

(mm)

Locality 8:

USNM 242054

(holotype)

USNM 242055

22

28

Loop 

length

(mm)

18.5b

21

Loop 

width

(mm)

12. Oc

13. Oc

Loop 

depth

(mm)

20

25

Distance

to crural 

processes

(mm)

Length of

transverse 

band

(mm)

Locality 8:

USNM 242731 9.8 6.2 3.3e

Types.—Holotype: USNM 242054; figured specimens: 

USNM 242054, 242060, 242731; measured specimens: 

USNM 242054, 242055, 242731.

Occurrence.—R. incurvirostra has been recovered from 

localities 2 and 8, in eastern Idaho (fig. 1). The sampled 

horizon probably is within the Thaynes Formation.

Comparison. —R. incurvirostra is the oldest species of the 

genus. It may be distinguished from most species of Rhaetina by its rectimarginate to incipiently uniplicate anterior 

commissure. From those species having such a commissure, 

which include the Norian-Rhaetian R. taurica Moisseiev 

and the Carnian-Norian R. pyriformis (Suess), it may be 

distinguished by its extremely incurved ventral beak. Of 

these two, it is probably more closely related to R. pyriformis. It may readily be distinguished from other North 

American Early Triassic terebratulids by its larger size and 

strongly incurved ventral beak.

Superfamily TEREBRATULACEA Gray, 184O

Family TEREBRATULTOAE Gray, 184O

Subfamily PLECTOCONCIfflNAE Dagys, 1974

Genus VEX, n. gen.

Etymology of name. — L. vexo = vexation.

Diagnosis.— Incipiently uniplicate, secondarily multicostate terebratulaceans with narrow loop and long delicate 

descending lamellae, no inner hinge plates or dental plates, 

keeled crural bases, and crural process points anterior to 

hinge plates.

Type species. — Terebratula semisimplex White, 1879, 

U.S. Geol. and Geog. Survey Terr. (Hayden), Bull., v. 5, 

no. 1, p. 108.

Occurrence.—Specimens referable to Vex have been recovered from the Thaynes Formation in Bingham and Caribou Counties, southeastern Idaho.

Comparison. — Vex is easily distinguished from most other 

terebratulids by its incipiently uniplicate and secondarily 

multicostate anterior commissure. Its dorsal valve is rarely 

geniculate as are those in the Paleozoic dielasmataceans 

Hemiptychina Waagen and Dielasmina Waagen, and it 

lacks the septalial plates characteristic of those forms. The 

Paleozoic Notothyrididae, although similar externally, are 

long-looped forms having entire hinge plates. Of the de-
10 TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

scribed Mesozoic genera, Vex is most similar to Plectoconcha Cooper. The loops of both forms are not well known; 

and, although the latter genus is commonly larger than Vex, 

they are otherwise similar externally. Serial sections parallel 

to the commissural plane of a topotypic specimen of Vex 

semisimplex (White) (USNM 8190b) show a relatively long 

and narrow loop, compared to the short broad structure observed in specimens of Plectoconcha aequiplicata (Gabb) 

(USNM 242083; pi. 2, figs. 6, 7). In Plectoconcha the points 

of the crural processes are at or posterior to the ends of the 

hinge plates. In Vex they are anterior of that position.

Vex semisimplex (White)

Plate 1, figures 25-42; Plate 2, figures 1-5

Terebratula semisimplex White, 1879, U.S. Geol. and Geog. Survey Terr. 

(Hayden), Bull., v. 5, no. 1, p. 108; White, 1880, U.S. Geol. and 

Geog. Survey Terr., Ann. Rept. 12 (1878), p. 108, pi. 31, figs. 3a-c; 

Girty, 1927, U.S. Geol. Survey Prof. Paper 152, pi. 30, figs. 5-7.

Diagnosis. —Small variably costate Vex.

Description.—Small- to medium-sized terebratulids; 

ventral fold and dorsal sulcus incipient to weakly developed. 

Shells subtriangular to subpentagonal in dorsal outline; 

widest anterior to midlength; deepest at or slightly posterior 

to midlength. Anterior commissure rectimarginate to incipiently uniplicate, complicated by costal traces of variable 

height and amplitude. Costae distinct, originating at variable distances from umbo.

Ventral valve more convex, has erect to incurved beak 

and small- to medium-sized round pedicle foramen. Beak 

ridges poorly developed. Deltidial plates disjunct. Surface 

distally irregularly costate, mesially smooth or marked by 

faint growth lines.

Dorsal valve having slightly pointed beak produced to fill 

open delthyrium of opposite valve. Profile evenly domed in 

anterior and lateral views. Surface ornament as for opposite 

valve.

Ventral interior having distinct pedicle collar, but lacking 

dental plates. Teeth large, tabular, recurved.

Dorsal interior having well-developed bilobate cardinal 

process with raised rim. Sockets broad, deep, roofed by massive recurved socket ridges. Outer hinge plates broad, 

planar, arising from ventral margin of inner socket ritiges; 

inner hinge plates absent. Small triangular fossae bounded 

in anterior view by inner socket ridges, outer hinge plates, 

and dorsal keels of crura. Crural processes at anterior ends 

of outer hinge plates; crura somewhat keeled dorsally, but 

keels never extending to valve floor as septalial plates. 

Median septum absent; low myophragm separating paired 

elongate-oval anteriorly expanded adductor muscle scars 

which extend one-half valve length. Loop dielasmoid, delicate, with comparatively large crural processes, slender 

descending lamellae, and broad transverse band. Loop 

about two-fifths as wide as dorsal valve; from one-half to 

two-thirds as long. In serially sectioned paralectotype specimen (USNM 8190b), loop length = 7.0 mm, loop width 

= 3.5 mm, length of transverse band= 1.0 mm, distance to 

crural processes = 2.7 mm.

Length 

(mm)

Maximum 

width 

(mm)

Maximum

thickness

(mm)

Dorsal valve 

length 

(mm)

Locality 3: 

USNM 242061 

USNM 242062 

USNM 242063

Locality 6: 

USNM 242069

Locality 7:

USNM 242070 

USNM 242071 

USNM 242072 

USNM 242073 

USNM 242074

Locality 32: 

USNM 242075

Locality 33: 

USNM 242076 

USNM 242077 

USNM 242078 

USNM 242079 

USNM 242080

Locality 41: 

USNM 242064 

USNM 242065 

USNM 242066 

USNM 242067 

USNM 242068

Locality 44: 

USNM 8190a 

(lectotype) 

USNM8190b 

(sectioned 

paralectotype)

11.4 

12.7b 

12.9

14.9

6.2

7.0

8.6

10.7

11.7

16.0be

11.4

12.0

12.5b

13.0

14.3

7.4

9.2

10.8

13.6

16.9

13.9

14.0

10.5

12.6

12.6

13.4

5.4C 

6.2 

7.7 

9.5 

10.6

13.3

9.4 

12.4 

12.2b 

12.0 

13.4

7.5 

8.1 

9.5

11.1

14.0h

11.2

10. 5C

6.2

6.9C

7.5

10.2

3.5 

4.3 

5.0 

6.1 

6.6

10.Oe

7.0 

7.5 

7.5 

7.9 

10.0

3.7 

6.0 

6.5 

8.5C 

9.7

10.0

10.6b

11.4

13.2

5.4 

6.0 

7.2 

9.1 

10.2

9.6 

10.3 

11.Oe 

11.2 

12.7

6.4

7.8

9.5

11.1

15.4

12.0

12.1

Types.— Lectotype: USNM 8190a; measured specimens: 

USNM 8190a, 8190b, 242061-242080; figured specimens: 

USNM 8190a, 8190b, 242063, 242065, 242069, 

242071-242075, 242081, 242082.

Occurrence.—The type locality of V. semisimplex 

(White) is only approximately known. The syntype specimens collected by A. C. Peale of the Hayden Territorial 

Survey in 1877 were later described by White (1880). The 

section from which the specimens were collected probably is 

within the Crane's Flat 15-min quadrangle, in southeastern 

Idaho (fig. 1, loc. 44). White (1883, p. 106) placed the collecting horizon about 500 m stratigraphically above a 

bluish-gray limestone unit containing Meekoceras gracilitatis. Because the M. gracilitatis zone defines the base of the 

Thaynes Formation, barring structural complications 

within the section, the V. semisimplex horizon may be 

placed within the upper part of the Thaynes, probably in 

the Portneuf Limestone Member. Indeed, Girty (in Mansfield, 1916, p. 39; in Mansfield, 1920, p. 50) reported that 

the horizon of T. semisimplex was within that unit. Only 

five specimens collected by Peale could be located in the National Collections. One (USNM 8190b) has been serially sectioned (pi. 2, figs. 1-5) to show the internal details of the 

species, which have not been previously described. In the 

present study, V. semisimplex is recognized at localities 3, 

5-7,9, 32-34,41, and44.
SYSTEMATIC PALEONTOLOGY 11

Comparison. — Vex is monotypic. Its differentiation from 

other similar costate or plicate terebratulid genera is discussed under the genus. It is easily distinguished from the 

other North American Early Triassic terebratulids by its incipiently uniplicate and secondarily multicostate anterior 

commissure.

Discussion. — The simulated ontogenetic series (pi. 1, figs. 

25-32) shows the great variability in radial ornament. This 

variability led Girty to describe an additional (unpublished) 

subspecies, best represented here by plate 1, figure 30. He 

correctly recognized that this form was a manifestation of 

infraspecific variability.

Superfamily CRYPTONELLACEA Thomson, 1926

Family CRYPTONELLIDAE Stehli, 1965 

Subfamily CRYPTACANTHIINAE Stehli, 1965

Discussion.—Stehli (1965) placed this subfamily within 

the Family Mutationellidae Cloud and included within it the 

genera Cryptacanthia White and St. John, Gacina Stehli, 

and Glossothyropsis Girty. Since that time several authors 

(Dagys, 1968, 1974; Cooper and Grant, 1976) have recognized that the subfamily more properly belongs within the 

Cryptonellidae, on the basis of similarity of loop development in the cryptacanthiine and cryptonellid genera. The 

range of the subfamily is here extended upward into the 

Norian and is expanded to include Obnixia, n. gen., and 

Anadyrella Dagys.

Dagys (1974) placed the Ladinian and Norian genus Anadyrella with Aulacothyroides Dagys in the Aulacothyroideidae. Of the two, only the loop development of Aulacothyroides has been documented (Dagys, 1972). It has strong 

inner hinge plates and dorsal median septum, and in its loop 

development shows additional important differences from 

Obnixia. Although Obnixia reaches the glossothyropsiform 

stage very early in its development (dorsal valve length approximately 2.5 mm), this stage is attained much later in 

Aulacothyroides (dorsal valve length approximately 

5.6 mm). In addition, the ascending lamellae of Aulacothyroides derive from a median vertical plate in the centronelliform stage, whereas those of Obnixia grow directly from the 

echmidium. In contrast, Anadyrella lacks a median septum, 

and its septalial plates, only questionably homologous with 

the inner hinge plates of Aulacothyroides, are much reduced. Anadyrella has been associated with Aulacothyroides 

solely on the basis of its cardinalia and the character of its 

mature loop. But the progression of loop development in 

Anadyrella is unknown, and the genus at present is represented by only three individuals referred to one species. Although Anadyrella (Dagys, 1974, p. 186, fig. 129) clearly 

possesses more robust septalial plates than does O bnixia, the 

similarities between the two, and the differences between 

Aulacothyroides and Obnixia, are sufficiently compelling, 

in my opinion, to justify placing A nadyrella and Obnixia in 

the same subfamily; thus, A nadyrella is reassigned from the 

Aulacothyroideidae to the Cryptacanthiinae.

Genus OBNIXIA, n. gen.

Etymology of name. — L. obnixus= resolute.

Diagnosis.—Sulcate cryptacanthine terebratulids having 

no inner hinge plates; loop development entirely from primary elements, proceeding through precentronelliform, 

centronelliform, cryptacanthiform, and glossothyropsiform 

stages.

Description.—Cryptacanthine terebratulids having unequally biconvex valves bearing a variably developed dorsal 

sulcus and ventral fold. Surface smooth or with rare concentric lamellae. Radial ornament wanting.

Ventral valve more convex. Beak suberect to erect in 

lateral view. Beak ridges sharp, defining palintrope. Pedicle 

foramen small, mesothyridid. Deltidial plates thin, conjunct.

Dorsal valve less convex. Faint median sulcation evident 

early in ontogeny, more pronounced in mature specimens.

Interiors as for species.

Type species. — Terebratula thaynesiana Girty, 1927, 

U.S. Geol. Survey Prof. Paper 152, p. 435, pi. 30, figs. 5-7.

Occurrence.—Same as for species. If Anadyrella infrequent Dagys proves congeneric with Obnixia, the stratigraphic range of the combined genera will extend into the 

Upper Triassic (Norian) and the geographic range, into the 

northeastern part of the U.S.S.R. (approximately long 165° 

E.,lat60°N.).

Comparison. — Obnixia is easily distinguished from the 

late Paleozoic genus Cryptacanthia by its distinctive loop development and by its lack of inner hinge plates. The 

Devonian and early Carboniferous genus Gacina bears an 

entire, but perforate inner hinge plate, and in loop development attains only a modified centronelliform stage. The 

Permian genus Glossothyropsis bears a strong median septum and commonly is more markedly sulcate. Glossothyropsis juvenis Cooper and Grant, from the Upper Permian 

Hegler and Rader Limestone Members of the Bell Canyon 

Formation of west Texas, may be related to Obnixia more 

closely than at the generic level. It differs in bearing a distinct apical dorsal median septum and small, but disjunct, 

inner hinge plates.

Discussion.— Dagys (1974, fig. 163) suggested that the 

Aulacothyroideidae—represented by the genera Aulacothyroides and Anadyrella, of Ladinian through Norian age — 

arose from a basic dielasmatacean stock early in the 

Triassic; whereas the Cryptonellacea, including such forms 

as Cryptacanthia and Glossothyropsis, came to a suitably 

cryptic end in the Upper Permian. Examination of ontogenetic series of Obnixia thaynesiana suggests a rather different evolutionary scheme. The ontogenetic development 

of the loop of Obnixia closely parallels that of Glossothyropsis, from which it differs only in its reduced median septum, 

lack of inner hinge plates, and less markedly crenulate anterior commissure. Because the two best known late Paleozoic 

cryptacanthine genera (Cryptacanthia, Glossothyropsis) already show phenotypes combining these characters, it is 

plausible that cryptacanthines surviving into the Triassic 

might resemble O. thaynesiana. From O. thaynesiana it is a 

short morphologic step to Anadyrella, requiring only the
12 TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

total loss of an already vestigial median septum and the 

somewhat more distinctive development of apical (septalial) 

plates, which structures already appear in some specimens 

of O. thaynesiana. (See pi. 2, fig. 26.) The phylogenetic 

scheme that such a relationship implies warrants reconsideration of the evolutionary development within the Terebratulida as outlined by Dagys (1974).

Obnizia thaynesiana (Oirty)

Plate 2, figures 8-27; plate 3, figures 1-13

Terebratula thaynesiana Girty, 1927, U.S. Geol. Survey Prof. Paper 152, 

p. 435, pi. 30, figs. 5-7.

Diagnosis. —Small sulcate cryptacanthine terebratulids 

having no inner hinge plates; loop development entirely primary, proceeding through precentronelliform, centronelliform, very brief cryptacanthiform, and relatively long 

glossothyropsiform stages.

Description.—Small shells having unequally biconvex 

valves, subtrigonal to subpentagonal in outline, bearing 

variably developed dorsal sulcus and ventral fold. Length 

and width subequal; thickness commonly about one-half of 

either (fig. 3). Surface smooth or bearing rare concentric 

growth lamellae; lamellae more conspicuous anteriorly. 

Radial ornament wanting.

Ventral valve more convex, domed in anterior view, 

maximum convexity in lateral view posterior to midvalve. 

Beak broadly rounded in dorsal view, suberect to erect in 

lateral view. Beak ridges sharp, defining palintrope. Pedicle 

foramen small, mesothyridid. Deltidial plates thin, conjunct.

Dorsal valve less convex, has greatest convexity in lateral 

view at or posterior to midvalve. Faint sulcation initiated 

early in ontogenetic development, at a length of about 

4 mm, becoming angular and pronounced in mature individuals.

Ventral interior having blunt anteriorly divergent dorsoposteriorly recurved hinge teeth, supported by short dental 

plates of quite variable expression. Pedicle collar distinct, 

short, thin.

Dorsal interior lacking median septum; low myophragm 

developed in later stages of ontogeny. Socket ridges reflexed 

somewhat distally (laterally), fitting into insets of mesially 

recurved ventral valve hinge teeth. Outer hinge plates narrow, in mature ontogenetic stages surmounted by a slight 

swelling of shell material. Crural bases distinct, attached to 

hinge plates by their ventral edges, bearing no inner hinge 

plates on their mesial margins. Crural bases unsupported 

dorsally by crural plates, but tiny divergent axial plates preserved in some mature specimens. Low myophragm separating faint striate adductor muscle scars may be present: never 

a striking feature of shell interior and never entering into development of loop during ontogeny. Loop long, anteriorly

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EXPLANATION

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o Locality 21 (paralectotypes)

~ A Locality 21 (lectotype) ~

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SHELL LENGTH (mm)

FIGURE 3. — Scattergram of dimensions of Obnixia thaynesiana (Girty) from 

southeastern Idaho (loc. 21) and southeastern California (loc. 37).

and laterally variably spinose, spines directed distally. Spine 

bases appearing as conical cavities on proximal faces of 

descending branches of loop. Crural processes low, mesially 

curved. Spines most commonly directed anteriorly at junction of descending and ascending lamellae. Ascending 

branches of mature specimens meeting in smoothly curved 

posteromesially notched junction just anterior to crural processes. Loop development proceeding through precentronelliform, centronelliform, very brief cryptacanthiform, 

and relatively long glossothyropsiform stages (table 1). Loop 

length varying from about one-half that of dorsal valve in 

centronelliform stage to about two-thirds that of dorsal 

valve in mature glossothyropsiform stages (fig. 4). Loop 

width about one-half dorsal valve width in valves less than 

2.5 mm wide; this ratio about two-fifths in wider valves 

(fig. 5). Length of ascending lamellae varying from about 

one-third loop length in smallest cryptacanthiform specimens to about three-fifths in mature glossothyropsiform 

loop (fig. 6). Distance to crural processes about one-half 

loop length until end of cryptacanthiform stage; approximates one-third loop length in glossothyropsiform stage 

(fig- 7).
SYSTEMATIC PALEONTOLOGY 13

TABLE 1. —Measurements (in mm) of dorsal valve and loop parameters for a simulated ontogenetic series of 

Obnixia thaynesiana (Girty), from southeastern California (loc. 37)

[n'a = not applicable. The loop is not resected anteriorly until about midway through the cryptacanthiform developmental stage]

Catalogue 

No.

USNM242119 

242120 

242121 

242122 

242123

242124 

242125 

242126

242127

242128 

242129 

242130

242131

242132 

242133 

242134

Developmental 

stage

Precentronelliform 

Precentronelliform 

Precentronelliform 

Centronelliform

Cryptacanthiform 

Cryptacanthiform

Glossothyropsiform 

Glossothyropsiform 

Glossothyropsiform

Glossothyropsiform 

Glossothyropsiform 

Glossothyropsiform

Anterior 

separation

n/a 

n/a 

n/a 

n/a

0.1 

0.15 

0 25

0 3

0.45ce 

0.9 

0.6e

LObe

0.5 

1.4 

0.6e

Valve 

length

1.45 

1.9 

1.1 

1.5

2.0 

2.15

3.35

4 i. j5 e

5.1 

5.8 

6.6

Valve 

width

l-6be 

2.0be 

1.2e 

1.6

9 0

2.25' 

2-4h

3 0

4.1 

4.4h

4 5L

5.4 

6.7be 

7.2

Loop 

length

0.6 

0.9 

0.7 

0.9 

1.5

1.2 

1.4 

1 15

2.2

2.2 

3.0 

3.0

9 Q.

3.7 

4.0 

4.9

Loop 

width

0.45 

0.55 

0.45 

0.5 

0.6

0.55 

0.6 

0.7C

0.85

1.2 

1.5 

2.0e

1.9

1.7

2.5 

2.7

Loop 

depth

0.15

0.2 

0.2 

0.3 

0.4

0.5 

0.5 

0.4

0.55

0.7 

0.8 

1.3

1.2

1.1 

1.2 

1.5

Ascending 

lamellae 

length

n/a 

n/a 

n/a 

n/a 

n/a

0.3 

0.5 

0.4

0.8

1.1 

1.35 

1.5

1

0 

• 3b

1.5 

2.2 

2.9

Distance 

to crural 

processes

0.35 

0.45 

0.3 

0.3 

0 4

0.45 

0.6 

0.5

0.7

0.85 

1.3 

1.1

i-Sbe

1.2 

1.4 

1.5

> 

> 3

12345 

LOOP LENGTH (mm)

FIGURE 4.— Scattergram of dorsal valve length and loop length 

of Obnixia thaynesiana (Girty) from southeastern California 

(loc. 37).

E

- 5h

f

3-

\ \

End of cryptacanthiform stage

0.5 1.0 1.5 2.0 

LOOP WIDTH (mm)

2.5 3.0

FIGURE 5.—Scattergram of dorsal valve width and loop width of 

Obnixia thaynesiana (Girty) from southeastern California (loc. 37).
14 TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

Locality 21:

USNM 121558

(lectotype)

USNM 121559a

USNM 121559b

USNM 121559c

USNM 121559d

USNM 242084

USNM 242085

USNM 242086

USNM 242087

USNM 242088

USNM 242089

USNM 242090

USNM 242091

USNM 242092

USNM 242093

Locality 37: 

USNM 242094

USNM 242095

USNM 242096

USNM 242097

USNM 242098

USNM 242099

USNM 242100

USNM 242101

USNM 242102

USNM 242103

USNM 242 104

USNM 242105

USNM 242106

USNM 242107

USNM 242 108

USNM 242109

USNM 2421 10

USNM 2421 11

USNM 2421 12

USNM 2421 13

USNM 2421 14

USNM 2421 15

USNM 2421 16

USNM 2421 17

USNM 2421 18

Total 

length 

(mm)

12.3

8.8

10.6

12.2

12.3

6.0

8.6

8.1

9.0

8.4

9.0

10.0

10. 3e

10.6e

10.2

1 8

1 .8

1.8

2.2

2.5

3.1

3.9

4.1

5.0

5.7

5.7

6.2

6.5

6.8

7.1

7.1

7.7

8.0

8.3

8.6

8.8

9.0

9.0

9.3

9.5

11.0

Total 

width 

(mm)

9.7

7.5

9.7

10.3

11.7

5.4

7.8

7.6e

7.8e

8.7

8.8

8.4e

9.6e

9.2

11.4

1.7 

1.8

2.1

2.2

3.2

3.6

3.6

5.3

5.6

5.6

5.6

6.3

5.9

7.1

7.2

7.8

7.5

8.4

9.3

8.7

9.0

9.2

9.2

8.8

10.8

Total 

thickness 

(mm)

7.3

4.7

5.3

6.8

6.3

3.0

4.0

4.5e

5.0

4.8

4.9

5.0e

5.1e

5.3e

6.0e

0.9

1.3

1.3

1.6

3.1

2.0

1.7

3.1

3.2

3.5

3.3

3.9

3.7

3.7

4.5

4.9

4.3

4.8

4.8

5.5

4.7

5.3

5.0

6.1

Dorsal valve 

length 

(mm)

10.8

7.8

9.2

10. 5 e

11.8

5.2

7.7

7.2e

7.9

7.1

7.5

8.9

9.1e

9.3

9.0

1.5 

L4

1.9

2.0

2.7

3.2

3.5

4.3

4.9

4.8

5.3

5.7

6.0

6.4

6.2

6.9

6.9

7.4

7.8

7.7

8.2

8.2

8.4

8.6

9.8

5

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LENGTH OF ASCENDING LAMELLAE (mm)

FIGURE 6.— Scattergram of loop length and

length of ascending lamellae of Obnixia

thaynesiana (Girty) from southeastern California (loc. 37).

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5 LOOP LENGTH (mm)

Types.—Lectotype: USNM 121558; figured specimens: 

USNM 121558, 242095, 242098, 242100, 242101, 242104, 

242105, 242108, 242111, 242115, 242116, 242119-242125, 

242128, 242129, 242131-242139; measured specimens: 

USNM 121558, 121559a-d, 242084-242134.

Occurrence. — O. thaynesiana has been confidently identified from the Thaynes Formation and from its stratigraphic equivalents from southeastern Idaho to southeastern California (Iocs. 10, 12-31, 36-40, 42, 43). (See fig. 1 

and "Fossil Localities Cited in this Report.") Its morphology 

changes very little over this broad geographic range, though 

more southern examples are somewhat more transverse.

Comparison.—The genus Obnixia is monotypic. O. 

thaynesiana may be distinguished from its most similar apparent relative, A nadyrella infrequens Dagys, by its smaller 

size, less robust septalial plates, and distinctive loop development scheme. It may easily be distinguished from other

FIGURE 7. —Scattergram of loop length and distance to crural processes of Obnixia thaynesiana (Girty) from southeastern California (loc. 37).

North American Early Triassic terebratulid brachiopods by 

its sulcate anterior commissure.

Loop development in Obnixia thaynesiana (Girty).— 

Terebratulid classification is made difficult by extensive 

homeomorphy. Shell form and outline not only may vary 

considerably within a single small genetic unit, but also they 

may appear similar in genetically distantly related forms. 

Until recently, however, it was less well understood that such 

presumably conservative structures as the terebratulid loop 

might also be subject to the vagaries of homeomorphy 

(Dagys, 1974; Cooper and Grant, 1976). Recent studies of 

loop development in late Paleozoic and Mesozoic terebratulids (Cooper, 1957; Dagys, 1968, 1972, 1974; Baker, 1972) 

have shown that many different genetic stocks may achieve
SYSTEMATIC PALEONTOLOGY 15

similar mature brachial support (loop) structures and that 

the previous simplistic terebratulid classification on the basis 

of "short" or "long" loops needs reevaluation. The difference between forms having similar mature loop designs 

often can only be discerned, for many species, if a relatively 

complete developmental series is available for study.

In calcareous specimens, loop detail can rarely be observed directly and commonly is reconstructed on the basis 

of serial sections or acetate peels. Pearson (1977) has reviewed serial grinding as applied to brachiopodl. This technique has the advantage in that it reveals the successive 

laminae, laid down during the growth of an individual, that 

are preserved in many calcareous specimens. These laminar 

traces may then be used to reconstruct ontogenetic stages. 

Cooper (1959) was justifiably critical of serial grinding techniques as used at that time. His main criticisms were the difficulty of maintaining parallel sections and the difficulty in 

making the intervals between successive sections sufficiently 

small that minute structures of taxonomic significance could 

be seen.

Silicified specimens, such as those used by Cooper (1957) 

in his study of loop development in Cryptacanthia, are 

much more easily prepared, as one need only remove the 

surrounding calcareous matrix and shell infilling by etching 

in a weak acid. However, disadvantages are inherent in the 

use of silicified specimens. Silicification is a poorly understood phenomenon, but we do know that structures so preserved need not be replaced in their entirety. In addition, 

detail of ontogenetic significance within the shell is commonly lost during silicification. As time was short during 

this study and as the equipment available was not specifically designed for serial grinding, I have used that technique 

only where necessary to show the internal structures of unsilicified type specimens of taxonomic importance (for 

example, Obnixia thaynesiana (Girty) and Vex semisimplex 

(White)).

Calcified paralectotype specimens of Obnixia thaynesiana 

from southeastern Idaho were serially sectioned at intervals 

of 0.15 mm, and acetate peel impressions were taken at 

each interval. Selected diagnostic sections normal to the 

longitudinal axis of one such specimen (USNM 242139) are 

shown in figure 8. Sections of another paralectotype specimen (USNM 242135), oriented in the commissural plane, 

were projected onto plexiglass sheets and stacked to form a 

three-dimensional replica of the valve interiors. A stereopair photograph of this reconstruction appears on plate 2, 

figure 24. These figures illustrate the characteristic lack of 

inner hinge plates, the weak dorsal median myophragm, 

and the long anteriorly spinose glossothyropsiform loop of 

the mature Obnixia thaynesiana. Unfortunately, topotypic 

specimens were not silicified, and serial sectioning of a representative sample to document loop development would 

not have been feasible.

Finely preserved specimens from locality 37 (San Bernardino County, Calif.) were, however, judged conspecific with 

the syntypic suite. Etched from the surrounding limy 

matrix, these silicified specimens provide a good sampling of 

representative postembryonic stages in the development of

the loop of O. thaynesiana. Loop terminology in the following discussion is used in the sense of Cooper (1957).

The precentronelliform stage of O. thaynesiana is represented here by three specimens, all between 1 and 2 mm in 

length. In the most paedomorphic of these (USNM 242119; 

pi. 3, fig. 1), the loop consists only of the descending 

branches. These are oriented normal to the commissural 

plane, except at the anterodorsal tips, which are deflected 

slightly dorsomesially. The descending lamellae diverge 

anteriorly to about one-fourth valve width, terminating at 

about two-fifths valve length. There is no anteromedian 

ridge on the valve floor at this or any subsequent developmental stage. The next precentronelliform specimen 

(USNM 242120; pi. 3, fig. 2) is more coarsely silicified, but 

it shows broad descending lamellae, the tips of which have 

turned not only mesially but ventrally. In lateral view, their 

growing anterior margins are inclined anteroventrally at 

about 45°, the same attitude at which the echmidium of the 

centronelliform stage lies. The entire loop at this stage is 

concave in ventral view, although the tips of the descending 

lamellae do not yet meet to form a complete bowl. In the 

most advanced of the three precentronelliform individuals 

(USNM 242121; pi. 3, fig. 3), the tips of the descending 

lamellae are almost in contact. Spines are developed on the 

dorsal surfaces of the loop even at this early stage. Within 

this stage no correlation between valve size and level of loop 

development was discerned, but the precentronelliform 

stage commonly is completed by the time the dorsal valve 

has attained a length of 2 mm.

The centronelliform stage is reached very quickly, with 

little change in the length of the shell, but it is accompanied 

by a deepening of the ventral valve. A single specimen 

(USNM 242122; pi. 3, fig. 4) represents this extremely brief 

developmental stage. No median ventral plate is present; 

rather the two branches are simply fused. They do not butt 

squarely but are directed ventromesially, and their ends are 

broadened anteroventrally to form the echmidium — the tip 

of which projects ventrally beyond the commissural plane.

The cryptacanthiform stage is represented by three specimens (USNM 242123, 242124, 242125; pi. 3, figs. 5-7) having valve lengths of about 2 mm. In this stage a typical 

cryptacanthid "ring" or "hood," closed both anteriorly and 

posteriorly, is not developed. Instead, the growing edges, in 

the median line, quickly shift from the anteroventrally directed oblique position of the centronelliform stage to a 

ventrally directed orientation by means of more rapid 

growth of the dorsal parts of the ascending lamellae. As this 

growth progresses, the two branches of the loop are joined 

only proximally, and the distal (anterior) extremities remain 

separated. At the close of this stage (USNM 242125; pi. 3, 

fig. 7), the mesial parts of the ventral margin of the ascending lamellae begin to grow anteriorly, subparallel to the 

commissural plane, and the proximal junction of the 

descending lamellae is resorbed. At this point the cryptacanthiform stage ends, and the glossothyropsiform stage 

begins.

The glossothyropsiform stage, present during most of the 

postembryonic development of O. thaynesiana, is initiated
16

0.10

u

0.15

O

0.25

O

0.15

O

0.10

O

0.10

O

0.15

0.15

0.15

0.15

TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

0.20 o.15

V ^* 

«, /

r" ^i

0.10

POSTERIOR

0.15

0.15

0.15

0.20

0.10

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.90

0.60

0.45

0.60

0.30

2.00 

ANTERIOR

FIGURE 8.—Thirty-five parallel serial sections of a paralectotype specimen (USNM 242139) of 

Obnixia thaynesiana (Girty) from southeastern Idaho (loc. 21). Section planes are oriented 

normal to the longitudinal axis of the shell. Numbers indicate distance (in millimeters) 

between successive sections. All sections X 4.0.
SYSTEMATIC PALEONTOLOGY 17

at a valve length of about 2.5 mm. It is represented in the 

present collection by nine specimens, of which six are 

figured (USNM 242128, 242129, 242131-242134; pi. 3, 

figs. 8-13). The anterior growth of the ascending lamellae is 

not so rapid in this stage as that of the descending lamellae, 

which continue to broaden and grow anteriorly. The junction of the two sets of lamellae becomes increasingly 

marked, through anterior growth and posterior resorption, 

so that in the mature glossothyropsiform loop, dorsoventrally oriented elements in the posteromesial parts of the 

ascending branches are totally resorbed, and only those 

parallel to the commissural plane and to the shell's longitudinal axis remain. During this stage the loop grows distally, but the flat surfaces of the descending and ascending 

lamellae remain essentially parallel. In the adult loop the 

planar surfaces of all parts of the loop and the crural processes are oriented anteroventrally and (or) laterally 

(distally).

Superfamily DALLINACEA Beecher, 1893

Family ZEILLERIIDAE Rollier, 1915

Genus PERIALLUS, n. gen.

Etymology of name. —Gr. periallos = before all others.

Diagnosis. —Rectimarginate to uniplicate or paraplicate 

zeilleriids having a distinct pedicle collar, inner hinge plates 

and (or) septalial plates, and profusely spinose descending 

lamellae.

Description.—Zeilleriids having smooth unequally biconvex valves, wide ventral umbo, and semierect beak. Anterior 

commissure variable; rectimarginate in smaller specimens to 

uniplicate or paraplicate in larger.

Ventral valve having large mesothyridid pedicle foramen 

and prominent disjunct deltidial plates. Beak broad; beak 

ridges prominent, sharp, in dorsal view defining large interarea.

Dorsal valve markedly transverse, has small beak and low 

umbo.

Ventral interior having distinct pedicle collar and strong 

dental plates. Hinge teeth strong. Muscle scars elongate triangular, commonly extending about one-half valve length.

Dorsal interior having broadly divergent sockets and posterodistally hooked inner socket ridges. Narrow outer hinge 

plates arising at about midheight of inner socket ridges, 

directed approximately in plane of commissure. Crural 

bases with short crural processes; arising from midwidth of 

hinge plates. Inner hinge plates present or absent; septalial 

plates variably disposed—vertical, joining valve floor, or 

dorsomesially directed, forming small septalium. Median 

septum of variable strength, extending about one-half valve 

length, present in all observed growth stages. Septal pillar 

and (or) median septum involvement in loop development 

not observed. Mature zeilleriiform loop long, commonly 

about two-thirds valve length; wide, commonly about onehalf valve width; composed entirely of primary elements.

Dorsal surface of descending lamellae profusely spinose. 

Cardinal area not well developed, commonly expressed as 

low shelf, overhanging umbo.

Type species.—Periallus woodsidensis, n. sp.

Occurrence. —P. woodsidensis, n. sp., has been recovered 

from the Woodside Formation in Caribou and Bear Lake 

Counties, southeastern Idaho, and from the Dinwoody Formation in nearby Wyoming and Montana. A larger form, 

less confidently assigned to that species, but definitely referable to the genus, comes from the "Ross Fork Limestone 

Member" of the Thaynes Formation in Caribou County, 

Idaho.

Comparison.—Periallus is easily distinguished from the 

four known Triassic zeilleriid genera by its rectimarginate to 

uniplicate or paraplicate anterior commissure. In addition, 

it differs from Zeilleria Rollier, Aulacothyris Douville, and 

Kolymithyris Dagys, in bearing a distinct pedicle collar. It 

differs from both Zeilleria and Woroboviella Dagys in its 

long dorsal median septum. Kolymithyris is easily distinguished by its thickened cardinalia.

Discussion.—The Zeilleriidae, placed within the Dallinacea following the usage of Dagys (1974), includes those 

forms in which the loop is not connected to any anteromesial 

structure in the dorsal valve during ontogeny. Although not 

even a relatively complete loop development series is available for Periallus, the smallest specimens examined (about 

2 mm long) show no evidence of such an anteromesial 

structure.

Dagys (1974) stated that profusely spinose loops are common in Middle Jurassic and younger dallinids but are unusual in the older true zeilleriids. This trait, however representative, cannot be construed as an argument against the 

assignment of Periallus to the Zeilleriidae. That assignment 

is made on the basis of the basic loop character and diagnostic features of the dorsal cardinalia.

Periallus woodsidensis, n. sp.

Plate 4, figures 1-15.

Terebratula margarztozw Bittner, in Newell and Kummel, 1942, Geol. Soc. 

America, Bull., v. 53, p. 954, pi. 2, figs. 5a,b (non T. margaritowi 

Bittner, 1899, Comite Geol. St. Petersburg Mem., v. 7, p. 27, 28, 

pi. 4, figs. 9-15 = Fletcherithyris Campbell).

Etymology of name. — Woodside = Formation name + L. 

-ensis = at the place of.

Diagnosis. —Small Periallus.

Description.—Small smooth unequally biconvex zeilleriid, having a wide ventral umbo and semierect beak. Subtrigonal or oval to subpentagonal in outline; commonly 

widest slightly anterior to midlength; deepest at about midlength. Anterior commissure rectimarginate, uniplicate, or 

paraplicate. Outermost growth increments commonly imbricate or lamellose.

Ventral valve more convex, having large mesothyridid 

pedicle foramen and prominent disjunct deltidial plates.
18 TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

Beak ridges prominent, sharp, defining curved palintrope. 

Beak wide, large, in dorsal view producing large interarea.

Dorsal valve less convex, markedly transverse, has small 

beak and low umbo.

Ventral interior having distinct pedicle collar and strong 

dental plates. Hinge teeth strong, tabular, hooked dorsally, 

directed anteromesially. Growth traces of hinge teeth 

present as low ridges on dorsomesial surfaces of dental 

plates. Muscle scars elongate triangular, commonly extending about one-half valve length.

Dorsal interior having broadly divergent sockets and 

posterodistally hooked inner socket ridges. Narrow outer 

hinge plates arising at about midheight of inner socket 

ridges, directed approximately in plane of commissure. 

Crural bases have short crural processes directed ventromesially at about 45°, arising from midwidth of hinge 

plates. Disjunct, narrow, elongate triangular inner hinge 

plates present or absent, variably expressed, produced 

mesially in plane of commissure; parallel bordered posteriorly, margins diverging anteriorly. Septalial plates variably expressed: as short vertical apical plates connecting 

inner hinge plate and crural base to valve floor or as 

obliquely inclined plates uniting dorsally with low median 

septum to form septalium. Median septum commonly 

prominent, extending about one-half valve length, present 

in all observed growth stages. Neither septal pillar nor 

median septum involvement in loop development observed. 

Mature loop zeilleriiform: long, commonly about two-thirds 

valve length; wide, commonly about one-half valve width, 

composed entirely of primary elements; having broadly 

curved anteriorly convergent but widely separated descending lamellae and broad ascending lamellae. Entire dorsal 

surface of descending lamellae profusely spinose. Cardinal 

area not well developed, commonly expressed as low transverse bipartite smooth shelf overhanging umbo.

Holotype

USNM 

242140

Paratypes

USNM 

242141

USNM 

242142

USNM 

242143

Measured m millimeters

Width ...............

Loop width ...........

Distance to crural

Length of ascending

Anterior separation . . . . .

5.8 6.5b 7.0be ......

5

*7 *7 Q C. A .1 7.2h 6.4h ......

2.9 3.7 2.9C ......

5.0 5.4b 5.7be 7.1

6

0 

• 8h

. . ...... ...... ...... 4.8

. . ...... ...... ...... 3.6h

1 5

, . ...... ...... ...... 2.0

. . ...... ...... ...... 0.9

. . ...... ...... ...... 2.4h

Types.— Holotype: USNM 242140; figured paratypes: 

USNM 242143-242153; measured paratypes: USNM 

242141-242143.

Occurrence. —Periallus woodsidensis was recovered only 

from Caribou and Bear Lake Counties, southeastern Idaho, 

where it occurs in the Woodside Formation (Iocs. 1, 11; 

fig. 1; "Fossil Localities Cited in this Report"). Specimens described by Newell and Kummel (1942) as T. margaritowi

Bittner are here referred to Periallus on the basis of the 

broad ventral beak, rectimarginate to paraplicate commissure, zeilleriid loop, and characteristic septalial plates and 

median septum. Those specimens were collected from the 

Dinwoody Formation in the Salt River Range, Lincoln 

County, Wyo. Newell and Kummel cited the distribution of 

this form as including southeastern Idaho but did not 

specify other localities further.

Comparison.—The genus Periallus is monotypic. 

P. woodsidensis is easily distinguished from Obnixia thaynesiana (Girty) by its rectimarginate to paraplicate anterior 

commissure and persistent strong dorsal median septum, 

which commonly extends half the length of the valve. It is 

very similar to Fletcherithyris margaritowi (Bittner), reported from the Induan Stage (Proptychites zone) of eastern 

Siberia (Primor'ye) and from the Olenekian Stage of 

Mangyshlak, U.S.S.R. (Dagys, 1965). It differs from 

F. margaritowi in bearing a zeilleriiform ("long") rather 

than a dielasmatid ("short") loop. In view of the recent justified combination of long- and short-looped forms within the 

Dielasmatidae (Dagys, 1972, 1974), it may be that the zeilleriids and dielasmatids represent stocks more closely related 

than heretofore thought.

Discussion.—The terminology conventionally used (see 

Campbell, 1965) to describe terebratulid cardinalia is useless to describe P. woodsidensis because P. woodsidensis has 

two distinct forms that might logically be termed "inner 

hinge plates." In the above description, those structures 

mesial to the crural bases and approximately in the hinge 

plane are referred to as "inner hinge plates." Those mesial 

to the crural bases but dorsally joining either a median septum or the dorsal valve floor are termed "septalial plates," 

following the usage of Dagys (1974). A wide range of variation in dorsal cardinalia is observed in a single population 

sample of P. woodsidensis from locality 1. At the one extreme, apical straight septalial plates extend almost vertically from the crural bases to the valve floor, flanking the 

median septum, and distinct inner hinge plates are mesial to 

the growth traces of the crural bases (pi. 4, fig. 12). In contrast (pi. 4, figs. 11, 14), in some forms, inner hinge plates 

cannot be discerned, and curved septalial plates join either 

at the valve floor or atop the median septum, in the latter 

case forming a septalium.

Periallus aff. woodsidensis, n. sp.

Plate 4, figures 16 20.

Description. — One specimen has the following measurements (in millimeters):

Locality 35: USNM 242154

Total length .....

Total width ......

Total thickness . . . 

Dorsal valve length.

19.3 Fold height ............. 1.5

17.9 Distance to crural processes . 4.0

8.6be Loop length. ............ 12.4be

16.6 Loop width ............. 8.3be

Types. —Figured and measured specimen: USNM 

242154.

Discussion.—Several specimens of Periallus questionably 

assigned to P. woodsidensis were recovered from locality 35,
REFERENCES CITED 19

in the "Ross Fork Limestone Member" of the Thaynes Formation, Bingham County, Idaho. Although no complete 

loop is preserved intact in any of the specimens, one specimen (USNM 242154) contained fragments of the descending 

and ascending lamellae sufficiently complete to determine 

the spinose character of the former and the zeilleriid form of 

the latter. The uniplicate commissure of these forms seems a 

reasonable outgrowth of the shell form seen in P. woodsidensis. The dorsal median septum, however, is not well 

preserved. The variations in cardinal plate arrangements 

are similar to those in P. woodsidensis, and the larger specimen may represent an adult of that form. The absence of 

forms intermediate in size and development between the two 

at any examined locality is the rationale for excluding the 

above specimens from formal specific status.

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Beecher, C. E., 1895, Revision of the families of loop-bearing Brachiopoda: Connecticut Acad. Arts and Sci. Trans. (1893), v. 9, pt. 2, p.

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Bittner, Alexander, 1899, Versteinerungen aus den Trias-Ablagerunger

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Boutwell, J. M., 1907, Stratigraphy and structure of the Park City mining

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Campbell, K. S. W., 1965, Australian Permian terebratuloids: Australia

Bur. Mineral Resources, Geology and Geophysics Bull. 68, 146 p.,

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Condit, D. D., 1917, Relations of the Embar and Chugwater formations in

central Wyoming: U.S. Geol. Survey Prof. Paper 98-O, p. 263-270,

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Cooper, G. A., 1957, Loop development of the Pennsylvanian terebratulid

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——— 1959, Genera of Tertiary and Recent rhynchonelloid brachiopods: 

Smithsonian Misc. Colln., v. 139, no. 5, 90 p., 22 pis.

Cooper, G. A., and Grant, R. E., 1976, Permian brachiopods of west 

Texas, V: Smithsonian Contr. Paleobiology, no. 24, p. 26Q9-3159, 

pis. 663-780, fig. 42.

Dagys, A. S., 1963, Verkhnetriasovye brakhiopody yuga SSSR: Moscow, 

Akad. NaukSSSR, Sibirsk. Otdeleniye, 238 p., 31 pis., 106 figs.

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Sibirsk. Otdeleniye, Inst. Geologii i Geofiziki, 186 p., 26 pis., 67 figs.

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Nauk SSSR, Sibirsk. Otdeleniye, Inst. Geologii i Geofiziki, Trudy, 

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mesozoyskikh Terebratulida, in Morfologichyeskiye i filogyenyetichyeskiye voprosi palyeontologii: Akad. Nauk SSSR, Sibirsk. Otdeleniye, Inst. Geologii i Geofiziki, Trudy, no. 112, p. 22-58, 28 figs.

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stratigraficheskoye znacheniye i biogeografiya): Akad. Nauk SSSR, 

Sibirsk. Otdeleniye, Inst. Geologii i Geofiziki, Trudy, no. 214, 387 p., 

48 pis., 171 figs.

Gemmellaro, G. G., 1899, La fauna dei calcari conFusultna della Valle del 

Fiume Sosio nella provincia di Palermo: Gior. Sci. Nat. Econ. 

[Palermo], v. 22, p. 95 214, pis. 25 36, 46 figs.

Girty, G. H., 1927, New species of Lower Triassic fossils from the Woodside 

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of Carboniferous and Triassic fossils by G. H. Girty: U.S. Geol. Survey 

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Gray, J. E., 1840, Synopsis of the contents of the British Museum: 42d ed.,

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Hose, R. K., and Repenning, C. A., 1959, Stratigraphy of Pennsylvanian,

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McKee, E. D., and others, 1959, Paleotectonic maps, Triassic System: U.S.

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McKelvey, V. E., and others, 1956, Summary description of Phosphoria,

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western phosphate field: U.S. Geol. Survey Prof. Paper 313-A, 47 p.

Mansfield, G. R., 1916, Subdivisions of the Thaynes limestone and Nugget 

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Washington Acad. Sci. Jour., v. 6, no. 2, p. 31-42.

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4 figs.

Moisseiev, A. S., 1938, Otriasovykh i yurskikh brakhiopodakh Pamirya: 

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no. 2, p.220-237.

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20 TEREBRATULID BRACHIOPODS FROM THE WESTERN INTERIOR OF THE UNITED STATES

— 1883, Contributions to paleontology, no. 5, Triassic. Triassic fossils 

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INDEX

[Italic page numbers indicate major references]

	Page

AdygeUa ................................... 8

Adygelloides ............................... 7, 8

aequiplicata, Plectoconcha .................. 10; pi. 2

Anadyrella ................................. 8, 11

infrequens .............................. 11,14

Ankareh Formation ......................... 6

restriction .............................. 8

Aspidothyris ............................... 8

Athyridaceans ............................. 6

augusta, Terebratula ........................ 1, 6

Aulacothyris ............................... 17

Aulacothyroideidae ......................... 11

Aulacothyroides ............................ 8, 11

B, defined ..................................

Bell Canyon Formation, Anadyrella infrequens

C, defined .....................

Carnian Series .................

Coenothyris ...................

Confusion Range, Utah ........

Crane's Flat 15-min quadrangle . 

Crural processes, defined .......

Cruratula .....................

7

11

7

9

8

4

10

7

8 

Cryptacanthia .............................. 11,15

Cryptcanthiinae ............................ 6, 11

Cryptonetlidae ............................. 11

Descriptive terms .......................... 7

Dielasma .................................. 8, 9

Dielasmina ................................. 9

Dielasma tidae ............................... 2, 7, 18

Dielasmatinae .............................. 8

Dienerian .................................. 6

Dinarella .................................. 8

Dinwoody Formation ......................... 4, 6, 7

Periallus woodsidensis .................. 17, 18

Terebratula margaritowi ................. 2, 18

Duchesne County, Utah ..................... 4

E, defined .................................. 7

episulcata, Portneufia ...................... 7, 8; pi. 1

Fletcherithyris ............................... 6, 8, 9

margaritowi ............................ 6, 18

Fort Hall Indian Reservation, Portneufia episulcata ......................... 8

Fort Hall Member .......................... 6

Fossils, localities ........................... 3

Gacina .............................

Ghssothyropsis .....................

juvenis..........................

Girty, G. H., terebratulid brachiopods . 

gracilitatis, Meekoceras ..............

gregaria, Terebratula.................

Hegler Limestone Member, Anadyrella infrequens ..........................

Hemiptychina ...............................

Page

Heterelasminidae ,

incuruirostra, Rhaetina................... 7, 8, 9; pi. 1

infrequens, Anadyrella ...................... 11,14

Induan Stage .............................. 6, 18

juvenis, Ghssothyropsis

Kolymithyris...........

Kosseerschiehten Series.

Ladinian Series..............

lepton, Rhaetina .............

Localities, fossil.............

Loops, measurements defined.

11

Mackentire Tongue, Woodside Formation..... 4

margaritowi, Fletcherithyris ................. 6, 18

Terebratula .............................. 2, 6,17

Meekoceras ammonite zone .................. 7

gracilitatis ............................. 10

Moenkopi Formation .......................... 4, 6, 7

Morphologic features, defined ............... 7

Mutationellidae ............................ 11

Norian Series... 

Notothyrididae .

9, 11

9

Obnixia .................................... 11

thaynesiana............... 3, 7, 11,12,18; pis. 2, 3

serial grinding ...................... 15

Olenekian Stage ............................ 16, 18

Park City district........................... 4

Park City Formation ........................ 6

Periallus ................................... 6,17

aff. woodsidensis ....................... 18; pi. 4

woodsidensis ....................... 2, 7, 17; pi. 4

Phosphate deposits ......................... 3

Phosphoria Formation ...................... 6

Plectoconcha ............................... 6

aequiplicata ............................ 10; pi. 2

Plectoconchiinae ........................... 6, 9

Portneuf Limestone Member ................ 6

index fossil............................. 7

Portneufia episulcata.................... 8

Vex semisimplex ........................ 10

Portneufia ................................. 7

episulcata ............................. 7, $ pi. 1

Primor'ye .................................. 6, 18

Proptychites zone .......................... 18

Propygope ................................. 8

pyriformis, Rhaetina ........................ 9

Rader Limestone Member, Anadyrella infrequens ..........................

References .................................

Rhaetian Series.............................

Rhaetina.

Page

Rhaetina incurvirostra ................... 7, 8, 9; pi. 1

lepton ................................. 9

pyriformis.............................. 9

taurica ................................. 9

Rhychonellacean ........................... 2, 6

Ross Fork Limestone Member ............... 6, 7

Periallus woodsidensis .................. 17

Periallus aff. woodsidensis ............... 19

Salt River Range, Wyo., Terebratula margaritowi ............................ 18

semisimplex, Terebratula ................... 1, 6, 9, 10

Vex ............................... 7,JO; pis. 1,2

Serial grinding ............................. 15

Serial sections, method ...................... 3

Shedhorn Formation ........................ 6

Smithian................................... 6

Spathian................................... 6

Spiriferinacean ............................. 2, 6

Subscripts, defined ......................... 7

Sulcatinella ................................ 6, 8

taurica, Rhaetina ........................... 9

Terebratula augusta ........................ 1, 6

gregaria................................ 8

margaritowi ............................. 2, 6, 17

semisimplex ........................... 1, 6, 9,10

thaynesiana .......................... 2, 6, 11, 12

Terebratulid brachiopods, descriptive terms .. 7 

Terebratulidae ............................. 9

Thaynes Formation ......................... 4, 7

base, Meekoceras gracilitatis ............. 10

defined ................................ 6

middle, Vex semisimplex ................ 10

Obnixia thaynesiana .................... 14

Periallus woodsidensis .................. 17

Periallus aff. woodsidensis ............... 19

Portneufia episulcata .................... 8

Vex.................................... 9

Thaynes Group .............................. 6

Thaynes Limestone ......................... 6

thaynesiana, Obnixia .......... 3, 7, 11, 12, 18; pis. 2, 3

Terebratula .......................... 2, 6, 11, 12

Uinta Mountains, Utah ..................... 6

Vex ....................................... 9

semisimplex ....................... 7, 10; pis. 1, 2

serial grinding ...................... 15

White, C. A., terebratulid brachiopods........ 1

Wind River Mountains, Wyo. ................ 6

Woodside Formation ................... 4, 6, 7, 17, 18

woodsidensis, Periallus .................. 2, 7, 17; pi. 4

Periallus aff............................. 18; pi. 4

Woroboviella............................... 17

Zeilleria.......

Zeilleriidae ....

Zugmayeria ... 

Zugmayeriinae

17

6, 17

7

6, 7

21

PLATES 1-4

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

Photographic Library, Federal Center, Denver, Colorado 80225.
PLATE 1

[The object plane parallax for stereo views is 6°]

FIGURES 1-10. Portneufia episulcata, n. gen., n. sp. (p. 8).

1. Paratype, articulated valves, dorsal view, X 1; showing asymmetric apparent immature invididual; USNM 242049; USGS loc. 1271-PC. 

2-8. Holotype, separable dorsal and ventral valves;

2. Articulated valves, dorsal view, X 1, for scale.

3. Dorsal view, X 2, for comparison.

4. Dorsal valve, ventral (interior) view, X 3, showing median septum and 

character of cardinalia.

5. Ventral valve, dorsal (interior) view, X 3, showing pedicle foramen, 

deltidial plates, and character of hinge teeth.

6. Articulated valves, anterior view, X 2, showing episulcate commissure.

7. Dorsal valve, lateral view, X 2, showing resected beak area at left.

8. Ventral valve, lateral view, X 2, showing expanded beak area at left. 

Specimens shown in figs. 28: USNM 242051; USGS loc. 1271-PC. 

9, 10. Paratype, fragment containing loop elements, dorsal and ventral views, X 3,

showing long descending and ascending lamellae and anteromesially

directed crural processes; USNM 242053; USGS loc. 1271-PC. 

11-24. Rhaetina mcurvirostra, n. sp. (p. 9).

11-15. Holotype, articulated valves; dorsal, ventral, anterior, posterior, and

lateral views, X 1; USNM 242054; USGS loc. 1291-PC. 

16, 17. Paratype, fragment of ventral valve; ventral view, X 2, showing elongate

pedicle foramen; dorsal (interior) view, X 3, showing elongate tubular

pedicle collar, concave surface of disjunct deltidial plates, and lack of

dental plates; USNM 242058; USGS loc. 1291-PC. 

18, 19. Paratype, fragment of slightly crushed ventral valve; dorsal view (inverted),

X 3, showing relation of hinge tooth to deltidial plates; anterodorsolateral

view, X 2, showing relation of pedicle foramen and hinge tooth; USNM

242059; USGS loc. 1291-PC.

20. Paratype, fragment of slightly crushed articulated valves, oblique posterior 

view, X 1, showing relation of ventral beak to hinge; USNM 242060; 

USGS loc. 1291 PC.

21. Paratype, nearly complete articulated valves, ventral beak missing, dorsal 

view, X 1, showing small acute dorsal umbo; USNM 242055; USGS loc. 

1291-PC.

22. Paratype, fragment of dorsal valve of apparent immature individual, 

ventral (interior) view, X 8, showing descending lamella and transverse 

band; USNM 242056; USGS loc. 1291-PC.

23. Paratype, fragment of dorsal valve, ventral (interior) view (stereo), X 2, 

showing relation of crural processes, inner and outer hinge plates, and 

median septum; USNM 242057; USGS loc. 1291-PC.

24. Paratype, fragment of dorsal valve, ventral (interior) view (stereo), X 1.5, 

showing partial dielasmoid loop with broad descending lamellae and 

long slender transverse band; USNM 242731; USGS loc. 1291 -PC. 

25-42. Vex semisimplex (White) (p. 10).

25-32. Figured specimens, articulated valves, dorsal views, X 1, showing simulated growth series and variation in form and radial ornament; USNM 

242071, 242072, 242065, 242073, 242074, 242063, 242069, and 242075; 

figs. 25, 26, 28, and 29 from USGS loc. 1289 PC; fig. 27 from USGS loc. 

M-853; fig. 30 from USGS loc. 826-PC; fig. 31 from USGS loc. 1284-PC; 

fig. 32 from USGS loc. 7813-(Green).

33-36. Paralectotype, articulated valves. (This specimen was serially sectioned 

parallel to the commissural plane; selected sections appear on pi. 2, 

figs. 15.)

33. Dorsal view, X l.forscale.

34. Dorsal view, X 2, for comparison.

35. Anterior view, X 2, showing rectimarginate to incipiently uniplicate commissure.

36. Lateral view, X 2, showing equibiconvex profile and semierect ventral

beak.

Specimen shown in figs. 33 36: USNM 8190b; USNM loc. 9344.

37-40. Lectotype, articulated valves, views and magnifications as in figs. 33-36 

above, for comparison; USNM 8190a; USNM loc. 9344.

41. Figured specimen, Fragment of articulated valves, anteroventral (interior) 

view (inverted; stereo), X 3, showing pedicle collar, cardinal process, 

hinge structures, and nature of dorsal cardinalia; USNM 242081; USGS 

loc. 1284-PC.

42. Figured specimen, fragment of descending lamellae of dorsal valve, lateral 

view, X 8, showing elongate crural processes; USNM 242082; USGS loc. 

1284-PC.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1057 PLATE 1

PORTNEUFIA, RHAETINA, AND VEX
PLATE 2

[The object plane parallax for stereo views is 6°]

FIGURES 1 5. Vex semisimplex (White), (p. 10) paralectotype, articulated valves, serial peels parallel to 

commissural plane (peel interval 0.15 mm) X 3, showing ventral valve pedicle collar 

(p.c.), hinge teeth (h.t.), dorsal valve crural processes (c.p.), descending lamellae 

(d.l.), and transverse band (t.b.); sections proceed from dorsal to ventral; USNM 

8190b;USNMloc. 9344.

6 7. Plectoconcha aequiplicata (Gabb) (p. 10), fragment of dorsal valve, ventral (interior) 

and lateral views, X 3, showing short descending lamellae and wide transverse band 

of loop, for comparison with figs. 1-5, above; USNM 242083; Leland Stanford Junior 

University loc. 2532 (Pershing County, Nev., Sonoma Range 1° quad.; sec. 21, 

T. 28 N., R. 39 E.; Tobin Range, north wall of "Keyhole" Canyon, elev. 6,200 ft; 

Upper Triassic; Collector: S. W. Muller, August 1941). 

8-27. Obnixia thaynesiana (Girty) (p. 12).

8 17. Figured specimens, articulated valves, dorsal views, X 1, simulated partial 

ontogenetic series, showing size range and variation in shape and form: 

USNM 242095, 242098, 242100, 242101, 242104, 242105, 242108, 

242111, 242115, and 242116; all from USGS loc. 7897 (Green).

18 21. Figured specimens, articulated valves, dorsal, ventral, anterior, and lateral 

views, X 3, showing low beak, rounded beak angles and sulcate anterior 

commissure of a mature individual; USNM 242116 (same as fig. 17 

above); USGS loc. 7897 (Green).

22, 23. Lectotype, articulated valves, dorsal views, X 1, for scale, X 2, showing form 

and outline; USNM 121558; USGS loc. 7406 (Green).

24. Paralectotype, stacked, oriented projections of commissural plane serial 

peels (peel interval approx. 0.15 mm) of articulated valves, ventral (interior) view (stereo), X 5, showing long anteriorly spinose loop; USNM 

242135; USGS loc. 7406 (Green).

25. Figured specimen, fragment of articulated valves, ventral (interior) view 

(stereo), X 8, showing dental plates and pedicle collar in ventral valve, 

and lack of prominent median septum or inner hinge plates in dorsal 

valve; USNM 242136; USGS loc. 7897 (Green).

26. Figured specimen, fragment of articulated valves, anterior (interior) view 

(dorsal valve down; stereo), X 8, showing tight articulation of recurved 

hinge teeth and sockets, vestigial apical dorsal median septum, and rudimentary septalial plates; USNM 242137; USGS loc. 7897 (Green).

27. Figured specimen, fragment of articulated valves, anteroventrolateral view 

(stereo), X 8, showing anterior spines at junction of descending and ascending lamellae of loop; USNM 242138; USGS loc. 7897 (Green)."
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1057 PLATE 2

OBNIXIA, PLECTOCONCHA, AND VEX
PLATE 3

[The object plane parallax for stereo views is 6°]

FIGURES 1-13. Obnixia thaynesiana (Girty) (p. 12), figured specimens, fragments of articulated valves, 

dorsal views (stereo), X 8, showing development of glossothyropsiform loop through 

precentronelliform (figs. 13), centronelliform (fig. 4), cryptacanthiform (figs. 

57), and glossothyropsiform (figs. 8 13) stages; USNM 242119 242125, 242128, 

242129, 242131-242134; USGS loc. 7897 (Green).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1057 PLATE 3

OBNIXIA
PLATE 4

[Unless otherwise noted, the object plane parallax for stereo views is 6°]

FIGURES 1-15. Periallus woodsidensis, n. gen., n. sp. (p. 17).

1. Paratype, fragment of articulated valves, dorsal view, X 1, showing small 

pedicle foramen, wide beak, and well-defined beak ridges; USNM 

242144; USGS loc. 76 PC.

25. Holotype, articulated valves, dorsal views, X I, for scale, X 3, showing form 

and outline; lateral view, X 3, showing profile and form of commissure; 

anterior view, X 3, showing rectimarginate commissure; USNM 242140; 

USGS loc. 76 PC.

6. Paratype, fragment of ventral valve, anterodorsal view (stereo: object plane 

parallax 3°), X 3, showing dental plates; USNM 242145; USGS loc. 

76-PC.

7-9. Paratypes, fragments of articulated valves, anteroventral views (stereo), 

X 8, showing variation in relationship of septalial plates and median septum in dorsal valve; USNM 242146, 242147, 242149; USGS loc. 76 PC.

10. Paratype, fragment of articulated valves, anterior view (dorsal valve down), 

X 8, showing distinct pedicle collar, strong dental plates of ventral valve, 

and strong median septum in dorsal valve; USNM 242148; USGS loc. 

76 PC.

11. Paratype, dorsal valve, anteroventral view, X 8, showing individual in which 

septalial plates do not contact median septum; USNM 242153; USGS 

loc. 76 PC.

12. Paratype, dorsal valve, ventral view (stereo), X 8, showing differentiation 

of septalial plates and inner hinge plates; USNM 242150; USGS loc. 

76 PC.

13. Paratype, dorsal valve, ventral view (stereo), X 8, showing high crural processes of mature individual; USNM 242151; USGS loc. 76 PC.

14. Paratype, dorsal valve, ventral view, X 8, showing septalial plates joining 

median septum to form septalium; USNM 242152; USGS loc. 76 PC.

15. Paratype, partial dorsal valve, ventral view, X 8, showing dorsally spinose 

descending lamella and portion of ascending lamella; USNM 242143; 

USGS loc. 76 PC. 

16-20. Periallus aff. woodsidensis, n. sp. (p. 18).

16-19. Figured specimen, articulated valves, dorsal, ventral (interior), anterior 

and lateral views, X 1, showing form, outline, and incipient uniplicate 

commissure; USNM 242154; USGS loc. 7879 (Green).

20. Figured specimen, fragments of loop, recovered after etching from within 

the above specimen, various orientations, X 2.5, suggesting that the loop 

was zeilleriiform; USNM 242154; USGS loc. 7879 (Green).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1067 PLATE 4

PERIALLUS

OU.S. GOVERNMENT PRINTING OFFICE: 1979-677-026/44