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VOLUME 98, NUMBER 333 JUNE 5, 1990

Latest Ordovician to Earliest Silurian

Solitary Rugose Corals of the

East-Central United States

Robert J. McAuley

and

Robert J. Elias

Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A. PALEONTOLOGICAL RESEARCH INSTITUTION

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'/^ LEGEND LITHOLOGIES LIMESTONE I I I

DOLOSTONE I / I

DOLOMITIC I ]/ I UNITED STATES! LIMESTONE

SHALE I I

-^ CALCAREOUS SHALE I I

-^ DOLOMITIC SHALE I I

^ CHERT OR SILICIFICATION

— ARGILLACEOUS 1 • • • CONGLOMERATIC o o o OOLITIC

xc:> ^=3 CORAL-RICH INTERVAL

/FACIES CONTACT DEFINITE

^^ FACIES CONTACT ' APPROXIMATE IOWA

REPORTED IN LITERATURE

FLOAT BLOCKS

CORRELATION DEFINITE CORRELATION APPROXIMATE LATERAL RELATIONSHIP UNCERTAIN

STRATIGRAPHIC POSITION -st. clair spr,ng OKLAHOMA .qualls KNOWN

POSITION IN ARKANSAS ^8 INTERVAL UNCERTAIN

ABUNDANT COMMON UNCOMMON RARE

Text-figure 1 - A. Index map showing study region . in east-central United States, and detail map showing outcrop areas (A-F) of uppermost Ordovician and lowermost Silurian strata within the Edgewood Province, and other localities mentioned in text; details of areas A-F are shown in Text-figures 2-5, 7, 8. B. Legend of symbols for Text-figures 2-5, 7. 8 )

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JUNE 5, 1990 VOLUME 98, NUMBER 333

Latest Ordovician to Earliest Silurian

Solitary Rugose Corals of the

East-Central United States

Robert J. McAuley

and

Robert J. Elias

Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A. Library- of Congress Card Number: 90-6 1316

Pnnted in the United States of America

Allen Press, Inc. Uwrence. KS 66044 U.S.A. CONTENTS

Page Abstract 5 Introduction 6 Acknowledgments 6 Stratigraphy and Solitary Rugose Corals South-Ccnlral Oklahoma 7 North-Central Arkansas 9 Southern Illinois and Southeastern Missouri 10 Northeastern Missouri 12 Northeastern Illinois 18 Northwestern Illinois and Eastern Iowa 21 Solitary Rugose Coral Assemblages 23 Age of Units and Regional Correlation 24 Biogeography and Events 27 The Edgewood Solitary Rugose Corals Growth 29 Abrasion 29 Algal Coatings 30 Epizoans 30 Borings 30 Orientation 31 Paleoecology 32 Intraspecific Variation and Evolution 32 Systematic Paleontology Introduction 32 Abbreviations of Repositories 33 Abbreviations of Collections 33 Suborder Streptelasmatina Wedekind. 1927 Family Streptelasmatidae Nicholson in Nicholson and Lydekker, 1889 Subfamily Streptclasmatinac Nicholson in Nicholson and Lydekker, 1889 Genus Strepielasma Hall, 1847 33 Slreplelasma subregiilare (Savage, 1913b) 34

Strepielasma sp. cf. S. suhregulare (Savage, 1 9 1 3b) 42 Strepielasma amsdeni. n. sp 43

Strepielasma leemonense Elias, 1 982a 45

Strepielasma sp. cf 5. leemonense Elias, 1 982a 47 Strepielasma sp. A 47 Genus Grewingkia Dybowski, 1873 Grewingkia sp. A 48 Genus Rhegmaphyllum Wedekind, 1927 Rhegmaphyllum sp 49 Subfamily Dinophyllinae Wang, 1947 Genus Dinophytlum Lindstrom. 1882 Dinophylhim sp 49 Subfamily Dalmanophyllinae Lecompte, 1952 Genus Dalmanophyllum Lang and Smith, 1939 Datmanopliyllum sp 50 Genus Bodophyllum Neuman, 1969 Bodophyllum shorti Elias, 1982a 50

Suborder Cyathophyllina Nicholson in Nicholson and Lydekker, 1 889 Family Ptychophyllidae Dybowski. 1873

Genus Cyalhaclis Soshkina in Ivanova et ai, 1955 Cyatliactisl sp 51 Suborder Monacanthina Neuman, 1984 Family Lambelasmatidae Weyer, 1973 Subfamily Coelostylinae Weyer, 1973 Genus KeelophyUum. n. gen 51 Kcelophyllum oklahomense. n. sp 52 Appendi.x: Stratigraphic Sections 53 References Cited 55 Plates 61 Index 76 LIST OF ILLUSTRATIONS

Text-figure Page

1. Index map showing study region in east-central United Slates, and legend of symbols for Text-figs. 2-5. 7, 8 foldout inside front cover

2. Stratigraphic sections and locality map in south-central Oklahoma 7

3. Stratigraphic sections and locality maps m north-central Arkansas 9 4. Stratigraphic sections and locality map in southern Illmois and southeastern Missouri 11

5. Stratigraphic sections and locality map in northeastern Missouri 13

6. Contacts between Kissenger Limestone Member of the Bryant Knob Formation and underlying and overlying units at Section 17 (Clarksville) 16

7. Stratigraphic sections and locality map in northeastern Illinois 19

8. Stratigraphic sections and locality map in northwestern Illinois and eastern Iowa 22

'». Small, local channel within Mosalem Formation at Section 32 (Thomson East) 23 10. t ompositc stratigraphic sections showing age and correlation of uppermost Ordovician to lowermost Silurian units and distribution of solitar> rugose corals in the east-central United States foldout inside back cover

I I . Biogeography of North .American Late Ordovician to earliest Silurian solitary Rugosa 28

1 2. Rose diagrams show ing directional orientations of solitary rugosan coralla 31

1 3. Relationship between number of major septa and corallum diameter in Slreptelasma subregulare (Savage, 191 3b) 37 14. Relationship between length of major septa and corallum diameter in Slreptelasma subregiilare (Savage, 1913b) 39

1 5. Relationship between thickness of major septa and corallum diameter in Slreptelasma subregulare (Savage, 1 9 1 3b) 39 16. Relationship between width of cardinal fossula and corallum diameter in Slreptelasma subregulare (Savage, 1913b) 41

I 7. Number of tabulae per cm of corallum length in Slreptelasma subregulare (Savage, 1 9 1 3b) and Slreptelasma amsdeni. n. sp 42 18. Relationship between number of major septa and corallum diameter in Slreptelasma amsdeni. n. sp. 43

1 9. Relationship between length of major septa and corallum diameter in Slreptelasma amsdeni. n. sp 43 20. Relationship between thickness of major septa and corallum diameter in Slreptelasma amsdeni. n. sp 44 21. Relationship between width of cardinal fossula and corallum diameter in Slreptelasma amsdeni. n. sp 44 22. Relationship between number of major septa and corallum diameter in Slreptelasma leemonense Elias, 1982a, and Slreptelasma

sp. cf .v. leemonense Elias. 1 982a 46 23. Relationship between number of major septa and corallum diameter in Grewingkia sp. A, Bodophyllum shorn Elias, 1982a, and Keetophyllum oklahomense. n. gen., n. sp 48

LIST OF TABLES

Table Page

1. Latest Ordovician to earliest Silurian solitary rugose corals in the study region, east-central United States 24

2. Condition of corallum exterior, mainly for specimens of Slreptelasma subregulare (Savage, 1913b) 30

3. Morphologic characteristics of Slreptelasma subregulare (Savage, 1 9 1 3b) and the closely related species Slreptelasma amsdeni. n. sp 33 4. Growth form and cur\ature of Slreptelasma subregulare (Savage. 1913b), Slreptelasma amsdeni. n. sp., Slreptelasma leemonense

Elias, 1982a (and Slreptelasma sp. cf .S'. leemonense Elias. 1982a), and Keelophyllum oklahomense. n. gen., n. sp 36

5. Frequency of data points above, or on and below, arbitrary lines drawn in Text-figures 13-16 and 18-21, for characteristics of

major septa and cardinal fossula in Slreptelasma subregulare (Savage. 1 9 1 3b) and Slreptelasma amsdeni. n. sp 38

6. Length and thickness of cardinal septum in Slreptelasma subregulare (Savage. 1913b) and Slreptelasma amsdeni. n. sp 40 7. Frequency of each type of shape for the cardinal fossula in Slreptelasma subregulare (Savage. 1913b) and Slreptelasma amsdeni. n. sp 40 LATEST ORDOVICIAN TO EARLIEST SILURIAN SOLITARY RUGOSE CORALS OF THE EAST-C ENTRAL UNITED STATES

Robert J. McAuley' and Robert J. Elias^

Department of Geological Sciences, The University of Manitoba, Winnipeg, Manitoba R3T 2N2 CANADA

ABSTRACT

Four solitary rugosan assemblages are recognized within the uppermost Ordovician-lowermost Silurian sequence in the east-

central United States: ( 1 ) Late Ordovician "epicontinental" assemblage (Richmondian); (2) Late Ordovician "continental margin" assemblage (Gamachian); (3) Edgewood assemblage (Gamachian-early Early Llandovery); and (4) Silurian assemblage (post-

Edgewood Llandovery). A Late Ordovician "epicontinental" assemblage is present in the upper Maquoketa Group (Richmondian).

Salvadorca raiidi (Elias, 1 98 1 ) occurs in southern Illinois, northwestern Illinois, and eastern Iowa. Grewingkia canadensis (Billings. 1862) has been identified in eastern Wisconsin. These species represent the Red River-Stony Mountain and Richmond solitary rugose coral provinces, respectively. They became extinct when the epicontinental sea withdrew at the end of Richmondian time,

due to a major glacio-eustatic sea-level drop. A Late Ordovician "continental margin" assemblage is represented by Rhegma- phyltum sp. in the Cason oolite (Gamachian) of eastern north-central Arkansas.

This study is focused on the Edgewood assemblage, situated stratigraphically above the Late Ordovician "epicontinental" assemblage and geographically lateral to the "continental margin" assemblage. The Keel Formation of south-central Oklahoma contains Slreplelasma subregidare (Savage, 1913b), Streplelasma amsdeni. n. sp., Slreplelasma leemonense Elias. 1982a. Slrep-

tetasma sp. cf S. leemonense Elias, 1982a, Grewingkia sp. A, and Keelophyltum oklahomense. n. gen., n. sp. Streplelasma sp.

cf. 5. subregulare (Savage, 1913b) and S. leemonense occur in the Cason shale of western north-central Arkansas. In southern Illinois and southeastern Missouri, species within the Leemon Formation are 5. subregulare. S. leemonense. and Bodophyllum shorti Elias, 1982a. Slreplelasma sp. A is present in the Noix Limestone of northeastern Missouri. The overlying Bryant Kjiob Formation yields 5". subregulare from the unnamed member, and S. subregulare. S. leemonense. and Grewingkia sp. A from the Kissenger Limestone Member. The Cyrene Formation, which is the lateral equivalent of the Noix and Bryant Knob, contains

5. subregulare in the middle part. Streplelasma subregulare is present in the Schweizer and Birds members of the Wilhelmi Formation in northeastern Illinois, and has been identified from the middle portion of the Mosalem Formation in northwestern Illinois. These taxa comprise the Edgewood Solitary Rugose Coral Province. The overall assemblage, in which 97.8 percent of

specimens belong to S'. subregidare. S. amsdeni, and 5. leemonense. seems to be most similar to that in the Dalmanitina Beds (Himantian) or possibly earliest Llandovery beds of Ostergotland. Sweden, and the Guanyinqiao Beds (Dalmanitina Beds; Himantian) of Guizhou Province, China. The Keel Formation, Cason shale, Leemon Formation, Noix Limestone, and lower to middle Cyrene Formation are considered to be Late Ordovician (Gamachian) in age. The lower Schweizer Member of the Wilhelmi Formation and lower Mosalem Formation may also be Gamachian. The upper Schweizer Member and the Birds Member of the Wilhelmi Formation, and the middle Mosalem Formation are Early Silurian (early Early Llandovery). The Bryant Knob Formation and upper Cyrene Formation may also be early Early Llandovery. Thus, the Edgewood assemblage spans the time interval from Gamachian to early Early Llandovery, and solitary Rugosa cannot be used to delineate the Ordovician-Silurian boundary in the east-central United States. Gamachian units in the southern portion of the Edgewood Province mark the regressive phase corresponding to the glacial

maximum, but could have been deposited during minor transgressions if sea level fluctuated during that time interval. The Gamachian(?) to Early Llandovery sediments of northern Illinois were deposited during the major latest Gamachian-Early Llandovery transgression associated with deglaciation. The Edgewood solitary Rugosa were not derived from corals of the Late Ordovician "epicontinental" assemblage. Their resemblance to some taxa previously restricted to the continental margin suggests that they originated from such forms.

Stratigraphically above the Edgewood is an assemblage characterized by genera typical of the Early to Middle Silurian. Dinophyllum sp.. Dalmanophyllum sp.. Cyathactisi sp., and Rhegmaphyllum sp. are found in the Bowling Green Dolomite (late Early Llandovery) of northeastern Missouri, the Elwood Formation (late Early to Middle Llandovery) of northeastern Illinois,

and the upper Mosalem Formation (late Early Llandovery) in northwestern Illinois. Cyathactisl sp. is present in the Cochrane Formation (Llandovery) of south-central Oklahoma, and Dalmanophyllum sp. occurs in the Sexton Creek Limestone (Llandovery) of southeastern Missouri. These corals were not derived from Edgewood taxa, and must have been introduced from elsewhere. Rhegmaphyllum Wedekind, 1927. was confined to areas near the North American continental margin in the Richmondian and Gamachian. As water depth and temperature increased during the Early Llandovery transgression related to deglaciation. the Silurian assemblage succeeded the Edgewood assemblage, possibly after a minor regressive event.

' Present address: Esso Resources Canada, 605 5th Avenue S.W., Calgary, Alberia T2P 2P8, CANADA. - Address correspondence to this author. Bulletin 333

INTRODUCTION machian) to earliest Silurian (early Early Llandovery) Edgewood Province occur in six outcrop areas The uppermost Ordovician to lowermost Silurian (Text-

fig. 1 A). The 30 stratigraphic sections that sequence in the east-central United States (Text-fig. we selected for this study lA) comprises Late Ordovician. Maysvillian-Rich- provide representative geographic cov- erage in each area; all but one have been described in mondian strata that are primarily shales, succeeded by previous literature, and fossils have been listed dominantly carbonate units that are typically thin and from most (see .Appendl.x: Stratigraphic Sections). Every sec- of limited areal extent. The latter units were considered tion was thoroughly examined for solitary coralla, which to be Early Silurian and were assigned to the Alexan- were found at 26 of them. drian Series by Savage (papers from 1908a through All specimens seen were collected, except from a few intervals in which they 1926. inclusive) and Reeds (1911). More recently, it were so numerous that this was impractical. Additional has been recognized that they include latest Ordovician specimens from some of these as well as other as well as Early Silurian deposits, based on studies of sections were incorporated into our study from collections made conodonts (e.g., Craig, 1969; Thompson and Satter- by T. W. Amsden in south-central Oklahoma, W. W. field, 1975; Barrick. 1986) and brachiopods (Amsden. Craig in north-central Arkansas, and T. E. Savage in 1971b, 1974. 1986), and preliminary work on solitary southern and northeastern Illinois and northeastern rugose corals (Elias, 1982a; McAuley, Elias, and Mat- Missouri. A total of 709 Edgewood solitary coralla are tison, 1986). identified to the species level and described herein. Although there has been a renewal of interest in these Solitary rugosan coralla were also collected from a units and their biotas since the early 1970's, precise Gamachian unit at St. Clair Spring in eastern north- correlations and ages, as well as facies relationships central Arkansas (see Appendix: Stratigraphic Sec- and paleoenvironments, remain uncertain to varying tions), and from later Llandovery strata situated degrees within outcrop areas and on a regional scale. immediately above those containing the Edgewood The time interval represented by these deposits merits corals. However, these collections are not extensive, special attention. Climatic and sea-level changes dur- and most of the Silurian specimens are poorly pre- ing the Late Ordovician to earliest Silurian glacial ep- served. We identified the best material to the generic och (see Hambrey. 1985) have been related to major level. Twenty-two of these coralla are documented global changes in sedimentation and biotas (e.g., Berry herein because of their importance in delineating and Boucot, 1973; Brenchley and Newall, 1984; the geographic and stratigraphic limits of the Edgewood Brenchlcy, 1984; Sheehan, 1988). The changeover from assemblage, and in interpreting biogeography and Ordovician to Silurian coral faunas is poorly under- events. stood because those of latest Ordovician to earliest This monograph represents the culmination of a Silurian age are inadequately known (Hill, 1981, pp. project that began as part of a Ph.D. dissertation by 51, 53). Elias (1979). Following publication of those results Elias (1982a, pp. 47-52, fig. 24) studied Late Or- (Elias, 1982a), research continued with two B.Sc. thes- dovician solitary Rugosa from the upper, Richmond-

es (Mattison, 1983; McAuley, 1 983) and a M.Sc. thesis ian portion of the Maquoketa Group in the east-central (McAuley, 1985) directed by Elias. The present pub- United States. The corals from southern and north- lication is based largely on McAuley's M.Sc. thesis, western Illinois and eastern Iowa belong to the Red and on subsequent work by Elias and McAuley. River-Stony Mountain Province, and those from east- We share responsibility for all the contents. ern Wisconsin were assigned to the Richmond Prov- ince. The Edgewood Province was proposed for solitary Rugosa from units situated immediately above ACKNOWLEDGMENTS the Maquoketa in southeastern and northeastern Mis- This project was funded by grants to R.J.E. from the souri and northeastern Illinois. The province was ten- Natural Sciences and Engineering Research Council of tatively extended to include south-central Oklahoma. Canada, and a University of Manitoba Graduate Fel- In the present comprehensive study, we precisely doc- lowship and Canadian Society of Petroleum Geologists ument the full stratigraphic and geographic distribu- Graduate Student Scholarship to R.J.M. B. W. Mat- tion of the Edgewood corals, consider their biostrati- tison and R. G. Zeilstra (University of Manitoba, Win- graphic and biogcographic significance, investigate their nipeg, Manitoba) assisted in the field. They and L. M. paleobiology and paleoecology, and thereby contribute McFarland (University of Manitoba) prepared many to the solution of geologic problems and to our knowl- of the thin sections. R. G. Zeilstra and C. J. Buttler edge of corals in latest Ordovician to earliest Silurian (nee Knapp; University of Manitoba) photographed time. some of the specimens. Solitary rugose corals of the latest Ordovician (Ga- T. W. Amsden (Oklahoma Geological Survey, Nor- Ordovkian-Sii.urian Rugose Corals: M( Auley and Elias

man, Oklahoma), W. Kuntz (Louisiana, Missouri), and mitted manuscript by W. A. Oliver, Jr. (United States

D. R. Babb (Belvidcre, Illinois) provided assistance Cjeological Survey, Washington, DC) and J. E. Sorauf during field work in south-central Oklahoma, at Hig- (Slate University of New York at Binghamton, Bing- ginbotham Farm in northeastern Missouri, and at Bel- hamton. New York), and from the editorial work of vidcre South in northeastern Illinois, respectively. G. P. R. Hoover (Paleontological Research Institution, P. Wahlman (University of Cincinnati, Cincinnati, Ithaca, New York). Publication of this study was made Ohio), and D. S. Brandt and A.-M. Welchcr (Eastern possible by grants from the Department of Geological Michigan University, Ypsilanti, Michigan) contribut- Sciences and the Faculty of Science at The University ed to R.J.E.'s collections in Missouri and at Belvidere of Manitoba. South in Illinois, respectively. T. W. Amsden, W. W. Craig (University of New Orleans, New Orleans, Louisiana), and R. D. Norby STRATIGRAPHY AND SOLITARY (Illinois State Geological Survey, Champaign, Illinois) RUGOSE CORALS supplied information on stratigraphic sections in Okla- South-Central Oklahoma homa, Arkansas, and northeastern Illinois, respective- Lithostratigraphy ly. D. L. Meyer (LJniversity of Cincinnati, Cincinnati, Ohio) and D. B. Blake (University of Illinois at Ur- The lithostratigraphic terminology we use (Text-fig. bana-Champaign, Urbana, Illinois) arranged the loan 2) follows Amsden (1967), who summarized earlier of specimens from repositories in their charge. A. A. nomenclature (Amsden, 1957, pp. 3-7, figs. 2. 3). The Petryk (Ministere de TEnergie et des Ressources, Que- type section of the Keel Formation and Ideal Quarry bec, Quebec) and C. W. Stock (University of Alabama, Member is Section 23 (Lawrence Quarry) (Maxwell, University, Alabama) provided R.J.E. with collections 1936, p. 50; Amsden, 1957, pp. 9, 11). The areal dis- from Quebec, and Alabama and Georgia, respectively. tribution of the formation was shown by Amsden ( 1 960,

This publication benefitted greatly from comments fig. 12; 1974, fig. 19; 1986, fig. 4). The Keel has a on R.J.M.'s M.Sc. thesis by R. A. McLean (Amoco maximum thickness of 4.5 m, but is generally much

Canada Petroleum Company Limited, Calgary, Al- thinner (Amsden, 1960, p. 44, fig. 12). berta) and T. W. Amsden, from reviews of the sub- The Keel Formation includes three main lithologies.

a a a < jc

5 2 5 S '5. 2 • ••*££ w «- «# e Q. « a 0. a -J o «

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SECTION 24 SECTION 23 (COAL CREEK) (LAWRENCE QUARRY) Text-figure 2. — Stratigraphic sections (to scale) and locality map (A) in south-central Oklahoma (see Text-fig. lA). For legend, see Text- figure IB (foldout inside front cover). LQ. = Ideal Quarry; B. — Brevilammdella beds. For references and precise locations of sections, see Appendix. Bulletin 333

Most of the formation is an oolite, which is commonly S. leemonense Elias, 1982a, Grewingkia sp. A, and silicified (Amsden. 1960, pi. 10, figs. 4-6, pi. 11, figs. Keeloplniliim oklahomense. n. gen., n. sp., are de-

1-6; Amsden, 1986, pi. 1, figs. 1, 3, 5, 6, pi. 3, fig. 3, scribed herein from the Keel Formation. Cyathactisl pi. 6, figs. 1-3). Some pisolitic beds are present at Sec- sp. is present at the base of the overlying Cochrane tion 23 (Lawrence Quarr>). The second lithology is the Formation. The distribution of these corals is shown oolitic, bioclastic calcarenite of the Ideal Quarry Mem- in Text-figure 2. Solitary coralla were not observed in ber (Amsden, 1960, pi. 10, figs. 1-3; Amsden, 1986, the Keel Formation at Section 22 (Cedar Village), and pl. 3, fig. 1, pi. 6, fig. 3). It is situated at the base of are not known to occur in the Sylvan Shale. the Keel, and is present at most outcrops (Amsden. The Pettit Formation (Amsden, 1980, pp. 23, 24) is 1960, pp. 33. 35). The Brcvilamintlella beds between an oolite less than 0.6 m thick that is locally present the lower and upper oolites of the Keel Formation at in northeastern Oklahoma (Amsden and Rowland, Section 23 are also composed of oolitic, bioclastic cal- 1965, pp. 22-24, 26, 27, fig. 8, pl. 6, figs. 1-6). It has carenite (.Amsden, 1986. pl. 2, fig. 1, pl. 3, fig. 2). The been tentatively correlated with the Keel Formation third lithology is a laminated calcilutite unit situated on the basis of lithology, stratigraphic relations, and between oolites of the Keel at a few outcrops, including position. Fossil debris, including pelmatozoans, is Section 24 (Coal Creek) (Amsden, 1960, p. 40; Pl. 6, present in the Pettit, but no macrofossils have been fig. 9). recovered. Solitary coralla were not found in our study The Keel Formation overlies the Sylvan Shale with of this unit at section Ch4 of Amsden and Rowland apparent conformity (Amsden, 1986, p. 6), and is un- (1965, pp. 24, 95, 96, fig. 7, pl. B), located about 100 conformably overlain by glauconitic, bioclastic calca- m north of the type section near Quails (see Text-fig. renite of the Cochrane Formation. I A).

Biota Age

Fossils have been reported from the Keel Formation Amsden (1967, p. 943, fig. 1) summarized the his- by a number of previous workers: Reeds (1911, pp. tory of age assignments for the Keel Formation. The 259, 261, 267 [the oolitic member of the Chimneyhill brachiopods were considered to be Late Ordovician Limestone therein is the Keel]), Maxwell (1936, tables (Hirnantian; i.e., late Gamachian) by Amsden (1971b,

fig. Barrick 1 , 2 [the Hawkms Limestone therein is the Ideal Quar- p. 22, 1; 1974, p. 26; 1986, p. 18). (1986, ry Member]), Amsden (1957, pp. 10-12, 15; 1960, pp. pp. 64, 66) suggested that the Noi.xodontus conodont 30, 31, 35, 44; 1971b, p. 22; 1974; 1986, pp. 10, 11, fauna of the Keel may be Hirnantian. He cited the figs. 7, 1 2; 1 988, p. 24), Peel ( 1 977), and Barrick ( 1 986). association of Noi.xodontus girardeauensis (Satterfield, Present in the Ideal Quarry Member, Keel oolite, and 1971) with brachiopods considered to be Hirnantian Brevilamnulella beds are pelmatozoans, brachiopods, in the east-central United States, and the position of bryozoans, gastropods, pelecypods, trilobites, ostra- that species between the Paraorthograptus pacijicus and codes, tabulate corals, and solitary rugose corals. Pel- Glyptograptus persculptus (?) graptolite zones at the matozoans, brachiopods, trilobites, ostracodes, and Blackstone River section in the Yukon. He also stated solitary rugose corals occur in the laminated calcilutite that Decoriconus costulatus (Rexroad, 1967) of the unit. Algal-coaled grains have been recognized in the Noi.xodontus fauna is typical of the earliest Silurian Ideal Quarry Member. The Keel Formation, including (Early Llandovery), but ranges down into the late Ga- the Ideal Quarry Member and laminated calcilutite machian on Anticosti Island, Quebec. It must be noted, unit, has yielded conodonts. A monoplacophoran has however, that McCracken and Lenz (1987, pp. 648, been described from oolite of the Keel Formation. 649) and McCracken (1987, p. 1452) considered strata In addition to previously reported fossils, we identify bearing N. girardeauensis in the Blackstone River sec- the siphonous green alga Dimorphosiphon sp. in thin tion to be of pre-Gamachian, late Richmondian age. sections of samples from the Ideal Quarry Member at At Section 24 (Coal Creek) and one other locality, Section 21 (Rock Crossing). Colonial rugose corals were beds at the top of the Keel Formation (immediately observed in the Brevilamnulella beds of the Keel For- above the laminated calcilutite unit) yielded a con- mation at Section 23 (Lawrence Quarry). One solitary odont fauna almost identical to that in the overlying rugosan corallum from those beds has an incrustation Cochrane Formation (Barrick, 1986, p. 57). The pres- that was probably produced by an alga or stromatopo- ence of Walliserodus curvatus (Branson and Branson, roid. Comulitids occur in the laminated calcilutite unit 1947) and Distomodus elements was used to suggest a at Section 24 (Coal Creek). Llandovery (position uncertain) age for those beds The solitary rugose corals Streptelasma suhregulare (Barrick, 1986, p. 67). However, those taxa appear at (Savage, 1913b), Streptelasma amsdeni, n. sp., Strep- and just above the base, respectively, of the Oulodusl telasma leemonense Elias, 1982a, Streptelasma sp. cf. nathani Conodont Zone on Anticosti Island (Mc- Ordovician-Silmrian Rugose Corals: McAuley and Elias

Cracken and Barnes, 1981, p. 66, fig. 12), and the North-Central Arkansas boundary defined as the base of Ordovician-Silurian Lithostratigraphy the Farakidograplus aciiniiiwtus Graptolite Zone lithostraligraphic terminology we use (Text-fig. (Cocks, 1985) may be situated within the O.? nathani The 3) is adapted from the following workers, who sum- Zone (Lesperance, 1985, figs. 3, 4; McCracken and marized the history of nomenclature: Craig (1969, Nowlan, 1988, p. 77). 1975a, 1975b, 1984), Craig in Craig, Ethington, and Beneath the Keel Formation, the Sylvan Shale con- Rcpetski (1986), Lemastus (1979), Craig, Wise, and tains Late Ordovician (Maysvillian-Richmondian)

McFarland ( 1 984), and Amsden ( 1 986, 1 8-20, 22. graptoliles of the Dicellograptus complanatus Zone in pp. 23). the lower to middle portion of the unit (Decker, 1935, Cason strata of Ordovician age are exposed in sev- pp. 698-700), conodonts that probably represent the eral areas of north-central Arkansas between Jasper Amorphognathus ordovicicus Zone (Sweet and Berg- (about 40 km west of Gilbert) in the west and St. Clair strom, 1976, p. 146), and Late Ordovician chitino- Spring in the cast (Lemastus, 1979, pp. 14-28. 36, 37, zoans throughout (Jenkins, 1 970, pp. 284, 285). Above 39_43, 46, fig. 1; Craig, Wise, and McFarland, 1984, the Keel, the brachiopod Triplesia alata Ulrich and

1 1-13, fig. lA, Phosphaticshale, Cooper, 1936, apparently ranges through most of the pp. 3; see Text-figs. 3). siltstone, and sandstone (Craig, 1975b, pi. 3, figs, a-h) Cochrane Formation (Amsden. 1971a, p. 145). Ams- are overlain locally and with apparent conformity by den ( 1 986, p. 6) considered it to be Early Silurian (early limestone that is predominantly an oolite but also in- Late Llandovery, C,,,)- but noted that it could be youn- cludes bioclastic calcarenite and calcilutite (Craig, ger or older. The conodont fauna of the basal Cochrane was thought to be Llandovery (position uncertain) by Barrick (1986, pp. 57, 64, 67). Late Late Llandovery (Cj) species of the Ptewspathodus celloni Conodont St. Clair Zone were identified in the uppermost Cochrane by Spring • Sec. Barrick and Klapper (1976, p. 66). Age assignments we follow are shown in Text-figure 2. INDEPENDENCE CO. SEARCY CO. Paleoenvironment

Amsden ( 1 960, pp. 4 1 , 42, 1 60) considered the Keel oolite to have formed in warm, shallow, agitated but not strongly turbulent water within the zone of effective light penetration. It is inferred from the random orientation of solitary rugosan coralla in the Brevilam- nulella beds and upper Keel oolite at Section 23 (Law- rence Quarry) that the directions of fluid motion may have been variable (Elias, McAuley, and Mattison,

1987,p. 810). Amsden (1986, pp. 10, 1 1, 42, 43) noted that fossils in the Keel are not in growth position and do not show excessive breakage, although the brachiopods are mostly disarticulated. He suggested that the energy level was moderately high. The gradational contact between the Ideal Quarry calcarenite and Keel

oolite probably indicates shoaling (Amsden, 1960, p. 43). All or the vast majority of solitary coralla in collections from the Keel oolite, Brevilamnulella beds, and Ideal Quarry Member are nonabraded, suggesting rapid burial. The lithology, bedding, and presence of articulated FERNVALE LST. brachiopods in the laminated calcilutite unit indicate (MAYSVILLIAN-7RICHM0NDIAN) that it was deposited in lower energy conditions than SECTION 33 ST. CLAIR other facies of the Keel Formation (Amsden, 1 986, pp. (BUFFALO RIVER) SPRING SECTION 12, 13, 43). However, the parallel alignment of solitary Text-figure 3. — Stratigraphic sections (to scale) and locality maps rugosan coralla is likely a result of hydraulic action. (B and St. Clair Spring) in north-central Arkansas (see Text-fig. 1 A). The nonabraded condition of these coralla at Section For legend, see Text-figure IB (foldout inside front cover). For ref- 24 (Coal Creek) suggests a high sedimentation rate. erences and precise locations of sections, see Appendix. 10 Bulletin 333

1975b, pi. 4. figs. a. b. e, h). At the St. Clair Spring Section are Himantian. In the upper portion of the

Section, the entire interval is limestone (Craig, 1975b, underlying Fernvale Limestone, conodonts represent pi. 4, figs, c, d, f, g; PI. 12, fig. 11). The Ordovician upper Fauna 11 or 12 (Maysvillian-Richmondian) portion of the Cason is up to about 6 m thick. It un- (Craig in Craig, Ethington. and Repetski, 1986, p. 18). conformably overlies the Femvale Limestone, and is The brachiopod Lcpidocyclus cooperi Howe, 1966, in unconformably o\erlain by the Cason "Brassfield" the upper Femvale was considered to be Maysvillian limestone or Nounger strata. by Amsden (1983, pp. 40, 42).

It has been suggested that conodonts in the lower, Biota middle, and upper parts of the Cason "Brassfield" Fossils representing the following groups have been limestone are Llandovery and represent the Disto- reported from phosphatic. clastic strata in the Ordo- niodits kentuckyensis. Pterospathodus celloni, and vician portion of the Cason: pelmatozoans, articulate Pterospathodus amorphognathoides zones, respective- and inarticulate brachiopods, bryozoans, gastropods, ly (Craig, 1969, pp. 1625, 1626; Craig in Craig, Eth- pelecypods, cephalopods, trilobites, ostracodes, and ington, and Repetski, 1986, pp. 25, 29). Barrick (1986, conodonts (Craig, 1975b, pp. 73-75, 78; Lemastus, p. 67) assigned conodonts from the lowermost "Brass- 1979, pp. 15, 36, 41, 42, 46, 90; Amsden, 1986, p. 20: field" at the St. Clair Spring Section to the Llandovery Craig in Craig, Ethington. and Repetski, 1986, pp. 8, (position uncertain). The brachiopod Triplesia alata 18). Evidence indicating that these fossils were re- Ulrich and Cooper, 1936, in the "Brassfield" was con- worked from the Femvale Limestone was presented sidered to be Late Llandovery by Amsden (1971a). by Craig (1975b, pp. 74, 75) and Craig in Craig, Eth- Age assignments we follow are shown in Text-fig- ington, and Repetski ( 1 986, pp. 8, 1 8). Conodonts that ure 3. are likeh indigenous occur in dolomitic shale of a sec- Paleoenvironment tion at Gilbert (Craig, 1975b. p. 80: Craig in Craig, Phosphatic, clastic beds of the lower Cason are con- Ethington. and Repetski, 1986, p. 18). Lemastus (1979, sidered to record a transgression over the eroded Fem- pp. 42, 88) reported silicified coralla from the upper- vale surface (Craig, Wise, and McFarland, 1984, p. 12). most dolomitic beds at Section 33 (Buffalo River). The The mainly oolitic carbonate sediments were deposited following groups have been reported from limestone at the same time as elastics in shallow subtidal to in- in the Ordov ician portion of the Cason: pelmatozoans, tertidal environments, possibly primarily in tidal chan- brachiopods. brvozoans, gastropods, trilobites, ostra- nels (Lemastus, 1979, pp. 27, 28; Amsden, 1986, pp. codes, conodonts, and corals (Craig, 1969, pp. 1623- 23, 44). 1625; Craig, 1975b, pp. 75-77; Lemastus, 1979, pp.

24, 25, 36, 37, 42; Amsden, 1986, 20, 22, fig. 18; pp. Southern Illinois and Southeastern Missouri

Barrick, 1 986. p. 64, table 7; Craig in Craig, Ethington, Lithostratigraphy and Repetski, 1986, pp. 8, 9, 18, 19; Amsden, 1988, p. 24). The lithostratigraphic terminology we use (Text-fig. The solitary rugose corals Streplelasma sp. cf. S. 4) follows Thompson and Satterfield (1975, pp. 73, 74, suhregulare (Savage, 1913b) and Streptelasma lee- 77, 79, fig. 3). They summarized the history of no- monense Elias, 1982a. are described herein from menclature, as did Willman and Buschbach (1975, pp. the uppermost, dolomitic and cherty beds of the Cason 86, 87, fig. 0-27) and Willman and Atherton (1975, at Section 33 (Buffalo River), where a halysitid tabulate p. 99, fig. S-10). coral is also present. We found Rhegmaphylhim sp. in The Girardeau Limestone, which consists of irreg- the Cason limestone at the St. Clair Spring Section. ularly bedded limestone with shale partings, overlies The distribution of these corals is shown in Text-fig- the Orchard Creek Shale with apparent conformity

ure 3. (Satterfield, 1 97 1 , p. 266). It is overlain unconformably by the Sexton Creek Limestone or, locally, the Leemon Age Formation. The type section of the Leemon is Section

Conodonts in the Cason limestone and dolomitic 20 (Short Farm) (Thompson and Satterfield, 1975, p. shale that predate the "Brassfield" were considered to 77). The formation has a maximum exposed thickness be latest Ordovician by Craig (1969, pp. 1624, 1625; of 3.8 m at Section 31 (Thebes North), but is locally 1975b, pp. 77, 80) and Craig in Craig, Ethington, and absent. Repetski (1986, pp. 18, 19). Barrick (1986, pp. 64, 66) Lithologics within the Leemon Formation include suggested that this Noixodonius conodont fauna may oolite (Amsden, 1986, pi. 1, fig. 2, pi. 4, figs. 5, 6), be Himantian Ue., late Gamachian) in age. Amsden oolitic bioclastic calcarenite (PI. 8, figs. 1^), and cal- (1986. pp. 20, 22, 26) concluded that brachiopods in careous shale (Amsden, 1986, pi. 4, fig. 4). Small, bio- the lower 1 m of the Cason oolite at the St. Clair Spring hermal mounds up to 0.5 m high occur at the base at Ordovician-Sii.urian Rugose Corals: McAuley and Elias

Section 19 (New Wells), and were described by Ams- the following workers: Savage (1913a, pp. 365, 366:

tig. ). 1913b: 1917 [the Cyrcne Member of the Edgewood dcn ( 1 974, pp. 2 1 , 22: 1 986, p. 33, pi. 4, 1 Quart/ therein is the Leemon]), (1971b sand grains ( Amsden, 1 986, pi. 1 , fig. 4) are most com- Formation Amsden /one therein includes the Lee- mon in the Illinois sections (Amsden, 1 974, p. 24), and [the basal Edgewood clasts of the Girardeau Limestone are generally present mon]: 1974: 1986, p. 33, figs. 23, 24, 26, 27). and near the base. The Leemon Formation unconformably Thompson and Satterfield (1975, figs. 7-9). In addi- overlies the Orchard Creek Shale or, where present, tion, we recognize the siphonous green alga Dimorpho- the Girardeau. The Leemon is unconformably overlain siphon sp. in thin sections of samples from the for- by the Sexton Creek Limestone, which contains bands mation at Section 20 (Short Farm) (PI. 8, figs. 2. 3) of chert nodules. and a bioherm at Section 19 (New Wells). Several solitary rugosan coralla from Section 19 have algal coat- Biota ings, and one has a boring we identify as Trypaniles Fossils from the Girardeau Limestone, including cri- sp. that was probably produced by a polychaete an- noids and other echinoderms, brachiopods, bryozoans, nelid. Microborings of algal and/or fungal origin occur gastropods, pelecypods, trilobites, cornulitids, and in a few solitary coralla from Section 20 and in some conodonts, were reported by Savage (1913a, pp. 358, from Section 19. 359: 1913b: 1917), Satterfield (1971), Brower (1973), Elias (1982a) documented the solitary corals Strep- Thompson and Satterfield( 1975, figs. 6,8), and IColata lelasma leemonense Elias, \9S2a, Streptelasma sp. [re- and Guensburg (1979). Solitary Rugosa are not known ferred herein to Streptelasma subregulare (Savage, from the Girardeau. 1913b)], and Bodophylliiin shorli Elias, 1982a, from Pelmatozoans, brachiopods, bryozoans, gastropods, the Leemon Formation at Section 20 (Short Farm), pelecypods, trilobites, ostracodes, conodonts, stro- and S. subregulare from the Leemon bioherms at Sec- matoporoids, tabulate corals, and solitary rugose corals tion 19 (New Wells). During the present study, the have been reported from the Leemon Formation by latter species was also found at Section 20, and S.

— T A -- — mI

~-r- ~^ \

SECTION 31 GALE SECTION 20 SECTION 19 (THEBES NORTH) SECTION (SHORT FARM) (NEW WELLS)

Text-figure 4. — Stratigraphic sections (to scale) and locality map (C) in southern Illinois and southeastern Missouri (see Te.\t-fig. l.A). For

legend, see Text-figure I B (fi^ldout inside front cover). For references and precise locations of sections, see Appendix. 12 Bulletin 333

subregiilare and 5. leemonense were obtained at Sec- Late Llandovery, C,.,) brachiopod Stricklandia pro- tion 3 1 (Thebes North). We identify Streptelasma sub- triplesiana (Amsden, 1966) was identified by Amsden regiilare and S. leemonense in Savage's collections from (1974, p. 24; 1986, p. 26; 1988, p. 26). Within the

Section 3 1 and the Gale Section, respectively. Dal- lower Sexton Creek in Cape Girardeau County, Mis- manophyllum sp. occurs at the base of the Sexton Creek souri, Thompson and Satterfield (1975, p. 70, figs. 6, Limestone, which overlies the Leemon, at Section 20. 7, 9) reported conodonts of the Early Silurian Paltodus Sahadorea randi (Elias, 1981) was described from the dyscrirus fauna, which corresponds to the Icriodina Orchard Creek Shale beneath the Girardeau Limestone irregularis Zone of Nicoll and Rexroad (1968) and the at Section 31 by Elias (1982a. pp. 61, 62, pi. 6, fig. 9; Distoniodus kentuckyensis Zone of Cooper (1975). 1985. p. 45). The distribution of these corals is shown Age assignments we follow are shown in Text-fig- in Text-figure 4. ure 4.

Age Paleoenvironment

Age determinations of earlier workers were sum- Brower (1973, pp. 266, 268, 269) suggested that marized by Willman and Buschbach (1975, pp. 86, 87, limestone beds in the Girardeau Limestone were gen- fig. 0-27) and Willman and Atherton (1975, p. 94, fig. erally deposited in quiet water, with organisms pre- S-10). Liebe was evidently first to conclude that concluded by low levels of oxygen or unsuitable substrates. odonts in the Girardeau Limestone are Ordovician The fossiliferous shaly partings represent higher energy

(Liebe, oral commun., 1 96 1 , cited in Berry and Boucot, conditions with favorable oxygen levels and substrates.

1 970. p. 1 54: Liebe. 1 962. pp. 9, 35). Satterfield (1971) The Leemon Formation of southem Illinois was de- and Thompson and Satterfield (1975, pp. 69, 70) as- posited in a channel that was cut into the Girardeau signed that unit to the very late Ordovician on the Limestone during an earlier period of exposure, ac- basis of stratigraphic relations and conodonts repre- cording to Savage (1910, p. 331; 1913b, pp. 20, 21; senting the Prioniodus ferrarius fauna. Brower (1973, 1917, pp. 77, 79 [the Edgewood Formation therein]). p. 264) reported that the Girardeau brachiopods were Amsden (1974. p. 24) noted that the presence of quartz being studied by R. Parkinson, who was "inclined to- sand and silt in the Leemon of Illinois and Missouri ward a latest Ordovician grouping (Gamachian stage)." indicates deposition near a source area. He observed The crinoids suggested a Richmondian or younger Or- that brachiopods show little fragmentation and are dovician (Gamachian) age to Brower (1973, p. 265). commonly articulated, and inferred moderate energy On the basis of conspecific crinoids, Kolata and Guens- environments. The majority of solitary rugosan coralla burg (1979, p. 1 122) considered it probable that the at Sections 3 1 (Thebes North) and 19 (New Wells) are underlying Orchard Creek Shale is Richmondian. Ross nonabraded, whereas most at Section 20 (Short Farm) (in Prvor and Ross, 1962, p. 9) found the "character- are abraded. This could reflect a lower sedimentation istic Cincinnatian" graptolite Climacograptits putilliis rate and/or higher energy conditions at Section 20. The (Hall, 1865) in that unit. A late Maysvillian-Rich- development of small bioherms at Section 19 suggests mondian age for the Orchard Creek has been suggested open, normal marine conditions. A boring (Trypanites on the basis of conodonts and stratigraphic position sp.) we observed in one bioherm passes through the (Sweet and Bergstrom, 1976, p. 147). matrix before entering a solitary corallum, indicating Brachiopods of the Leemon Formation were con- that the substrate was hard. sidered to be Late Ordovician (Himantian; i.e., late

1 1 2 1 [the basal Gamachian) by Amsden ( 97 b, p. Edge- Northeastern Missouri wood zone therein includes the Leemon]; 1974, pp. Lithostratigraphy 19, 22, 24). He noted that the assemblage at Section 19 (New Wells) "comprises fairly typical pre-Hirnan- The lithostratigraphic terminology we use (Text-fig. tian genera, Himantian genera, and post-Hirnantian 5) largely follows Thompson and Satterfield (1975, pp.

Silurian genera" (Amsden, 1986, p. 34). Thompson 81-85, 87, 89, 93, 95-100, fig. 3; but see Correlation. and Satterfield (1975, p. 79) also considered the unit p. 1 5). They summarized the history of nomenclature. to be Late Ordovician, based on abundance of the The Noix Limestone and Bowling Green Dolomite conodont Amorphognathiis ordovicicus Branson and also occur across the Mississippi River in Illinois, where Mehl, 1933. Noixodontus girardeauensis (Satterfield, the Bryant Knob Formation is apparently absent (Sav- 1971), which occurs in the Leemon as well as the Gi- age, 1914, p. 29 [the upper part of the oolite therein rardeau, may be restricted to the Himantian (Barrick, is the Bryant Knob]; Rubey, 1 952, pp. 25, 27; Amsden, 1986, pp. 64, 66). 1974, p. 18). From the Sexton Creek Limestone at a section in The Noix Limestone of the Edgewood Group occurs Alexander County, Illinois, the Early Silurian (early in a northwest-trending outcrop belt that is about 75 Ordovician-Silurian Rugose Corals: McAuley and Elias 13 14 Bulletin 333

km long and at least 1 1 km wide (Thompson and Sat- overlies the Noix Limestone or Bryant Knob Forma- terfield, 1975, p. 89). The type section of the Noix is tion. To the west, it overlies the Cyrene Formation. Section 16 (Clinton Spring). This unit is up to about The Bowling Green Dolomite is overlain unconform- 2 m thick, and is thickest along the west bank of the ably by the Sexton Creek Limestone or younger strata. Mississippi River. It is typically a light gray oolite Biota (.Amsden, 1974. pi. 28. figs. 5, 6), and is cross-bedded in places. At a few localities, it is in part argillaceous, The following workers identified fossils from strata phosphatic, and conglomeratic (Thompson and Sat- in Missouri that probably represent the Noix Lime- terfield, 1975, p. 87. fig. 10). The Noix overlies the stone, Bryant Knob Formation, and Cyrene Forma-

Maquoketa Shale unconformably, and is overlain by tion: Rowley ( 1 904 (see Ausich, 1 987]; 1 908, p. 23 [the the Brvant Knob Formation or Bowling Green Dolo- oolitic limestone therein is probably the Noix and mite. It is a lateral equivalent of part of the Cyrene Bryant Knob, and the brown earthy limestone therein

Formation, which is located to the west (Thompson is probably the Cyrene]) and Savage (1913b, pp. 24, and Satterfield. 1975. pp. 85, 103). 25; 1917, pp. 82, 83 [the Noix oolite therein is the

Geographicalh . the distribution of the Bryant Knob Noix and Bryant Knob, and the Edgewood limestone

Formation coincides approximately with that of the near Edgewood therein is probably the Cyrene]). Those Noix (Thompson and Satterfield, 1975, p. 85). The authors recognized crinoids, brachiopods, gastropods, type section of this formation and the Kisscnger Lime- pelecypods, cephalopods, trilobites, stromatoporoids, stone Member is Section 18 (Kisscnger) (Thompson tabulate corals, and solitary rugose corals. In addition, and Satterfield, 1975, p. 98). An unnamed member cystoid plates and tentaculitids, and conularids and that occurs at the base of the Br\ant Knob at the type cornulitids, were reported from strata that probably section, and locally elsewhere, overlies the Noix with represent the Noix and Bryant Knob, respectively. apparent conformity (Thompson and Satterfield, 1975, Stromatoporoids from the coral-rich interval at the p. 103). This member consists ofup to 2 mofdolomitic base of the Kisscnger Limestone Member, Bryant Knob limestone and or shale. The Kisscnger Limestone Formation, were described by Birkhead ( 1 967 [the Cy-

Member, up to perhaps 5 m thick, is a light gray, me- rene Member of the Edgewood Formation at loc. I dium- to coarse-grained, massively bedded, bioclastic therein]). In Illinois, Rubey ( 1 952, p. 1 70) listed brach- calcarenite ( Amsden, 1 974. pi. 28, figs. 3. 4). It overlies iopods and solitary rugose corals from the Noix Lime- the unnamed member with apparent conformity where stone, and brachiopods, bryozoans, gastropods, pe- both members are present, and overlies the Noix un- lecypods, trilobites, tentaculitids, cornulitids, tabulate conformably where the unnamed member is absent. corals, and solitary rugose corals from the Bowling The Br\ant Knob Formation is overlain unconform- Green Dolomite. ably by the Bowling Green Dolomite. Amsden documented brachiopods from the Noix The Cyrene Formation occurs immediately west of Limestone, Bryant Knob Formation, and Cyrene For- the Noix and Brvant Knob. The type section is about mation of the Edgewood Group in Missouri and Illi- 4 km northeast of Edgewood, Missouri, and Section nois (Amsden, 1971b, pp. 21,22 [included in the basal

13 (Bowling Green) is an excellent reference section and younger Edgewood zones therein]; Amsden, 1974

(Thompson and Satterfield, 1 975, pp. 82. 96). This unit [the Bryant Knob at loc. D and lower Bowling Green is about 2 m thick. It is a brown to bluish gray, fine- at loc. C therein are considered to be Cyrene herein]; to medium-grained, dolomitic limestone (Amsden, Amsden, 1988. p. 24). In addition to brachiopods,

1974, pi. 27. figs, la, b, 2a, b). The Cyrene overlies Amsden (1974, fig. 9; 1986, figs. 29, 30) identified the Maquoketa Shale, and is overlain by the Bowling pelmatozoans, bryozoans, gastropods, trilobites, ostra-

Green Dolomite. The latter contact is inconspicuous codes. and corals from the Noix and Cyrene, as well in the vicinity of Section 13 (Savage, 1914, p. 29; Row- as pelecypods and tentaculitids from the Noix. Con- ley, 1916, p. 317; Amsden. 1974, p. 1 1). odonts have been reported from the Noix Limestone,

The Bowling Green Dolomite is the upper unit of both members of the Bryant Knob Formation, and the Edgewood Group. The type section is located about Cyrene Formation in Missouri by Thompson and Sat-

I km east-northeast of Section 13 (Bowling Green), terfield (1975, figs. 10-15) and McCracken and Barnes which is a principal reference section (Thompson and (1982). Graptolites occur in the unnamed member of

Satterfield, 1 975, p. 99). This unit has an average thick- the Bryant Knob (Thompson and Satterfield, 1975, pp. ness of 6 to 9 m in Pike County, Missouri (Krey, 1 924, 97, 98). p. 27). It consists of buff, earthy, massive dolostonc In addition to fossils reported previously from the

(Amsden, 1974, pi. 28, figs. 1, 2), locally with beds of Bryant Knob Formation, we recognize the siphonous chert nodules in the upper two-thirds. In the eastern green alga Dmwrphosiphon sp. in thin sections of sam- part of this area, the Bowling Green unconformably ples from the unnamed member at Section 18 (Kis- Ordovician-Silurian Rucjose Corals: McAuley and Elias 15

songer), and the coral-rich interval at the base of the Limestone and Bryant Knob Formation. The con-

Kissenger Limestone Member at Sections 1 7 (Clarks- odont Noixodonlus girardeaiiensis (Satterfield, 1971) ville) and 16 (Clinton Spring) (PI. 3, fig. 16). Algal is present in the upper middle portion of the Cyrene coatings arc rare on solitary rugosan coralla in the un- at Section 1 3 (Bowling Cireen) (see Thompson and Sat- named member, but are relatively common in the cor- terfield, 1975, fig. I 1) and in the Noix. The Paltodus al-rich interval of the Kissenger. Microborings that dyscritus conodont fauna first appears definitely in the were likely produced by algae occur in some coralla upper portion of the Cyrene (Thompson and Satter- from the coral-rich interval, but are rare in those from field, 1975, p. 101) and in the Bryant Knob. Slrepte- overlying strata. Borings we identify as Trypanites sp., lasma suhregulare (Savage, 1913b) occurs in the Cy- which were probably formed by polychaete annelids, rene Formation (just below and within the interval are rare in solitary coralla from the Kissenger Lime- containing N. girardeauensis) and in the Bryant Knob stone. Formation.

Elias ( 1 982a) described the holotype of Slreptelasma Strata overlying the Maquoketa Shale in a quarry subregiilarc {Savage, 1913b) from the Cyrene Forma- located 1 .5 km north-northwest of Section 1 3 (Bowling tion near Edgewood, Missouri. During the present Green) were assigned to the Bowling Green Dolomite study, S. siihregularc was found elsewhere in the Cy- by Amsden ( 1 974, p. 8). The lower 3 m were tentatively rene, as well as in both members of the Bryant Knob correlated with the Noix Limestone on the basis of Formation. Slreptelasma sp. A occurs in the Noix brachiopods (Amsden, 1974, pp. 15, 18). We suggest h\mQs\or\e, and Streptelasina leeDwnenseEWas, 1982a, that these beds, now covered by water, correspond to and Grcwingkia sp. A are present in the Kissenger the Cyrene Formation (see also Amsden, 1988, p. 36). Limestone. Diiiophyl/uni sp.. Daliuanophylhim sp., and Amsden (1974, pp. 16-18, figs. 12, 13) considered Cyathactisi sp. are identified from the Bowling Green two hypotheses for the relationship between the Bryant Dolomite, and Rhegmaphylluin sp., DinophyUiim sp., Knob Formation and Bowling Green Dolomite. On and Dahnanophyllum sp. are recognized in limestone the basis of lithostratigraphic data, he favored the in- patches of the Bowling Green. The distribution of these terpretation that these units are laterally and vertically corals is shown in Text-figure 5. intergrading facies, rather than discrete units having separate depositional histories (see also Amsden, 1986, Correlation pp. 36, 37, fig. 34). Amsden inferred that basal strata

Early workers reported that the Bryant Knob For- of the Bowling Green at Section 1 7 (Clarksville) are mation (upper part of the "oolite" in their terminology) equivalent to the unnamed member comprising the at exposures in eastern Pike County, Missouri, con- lower portion of the Bryant Knob at Section 18 (Kis- tained abundant solitary and colonial coralla, as did senger), and to the Kissenger Limestone Member of the upper portion of the Cyrene Formation (which in- the Bryant Knob at Section 16 (Clinton Spring). cludes the Watson Limestone of Rowley) at western At Section 18 (Kissenger), a thin interval containing sections in the vicinity of Edgewood (Rowley, 1908, abundant solitary rugosan coralla is present at the base pp. 20, 2 1 ; Rowley, 1 9 1 6, pp. 3 1 9. 320; Savage. 1913b, of the Kissenger Limestone Member, immediately p. 22; Savage, 1917, p. 80). Savage (19 13b, p. 25; 1917, above the unnamed member of the Bryant Knob For- p. 83) considered the "oolite" to correspond to the mation (see Text-fig. 5). This coral-rich interval also upper half or two-thirds of the Cyrene. Thompson and occurs in the Bryant Knob at Section 1 6 (Clinton Spring)

Satterfield (1975, pp. 85, 87, 103) interpreted the Noix (see Birkhead, 1967, fig. 7), immediately above a thin, Limestone (which underlies the Bryant Knob) as a fa- shale-bounded carbonate bed. The latter bed did not cies of the upper part of the Cyrene Formation, al- yield conodonts, but was included in the Noix Lime- though conodonts used to correlate the Cyrene with stone by Thompson and Satterfield ( 1 975, fig. 12, sam- the Maquoketa Shale also occur in one section of the ple 9), presumably because it contained some ooids.

Bryant Knob (Thompson and Satterfield, 1975, p. 96, Elias (1982a, p. 40, fig. 21) placed this bed in the Kis- figs. 10, 1 1). On thebasisof brachiopodsand lithologic senger because it contained the same solitary rugosan similarity, Amsden( 1974, pp. 9, 11, 14, 15) tentatively species as the overlying coral-rich interval, and con- considered the upper half of the Cyrene of Thompson sidered the ooids to be reworked from the Noix. On and Satterfield at Section 1 3 (Bowling Green), as well the basis of lithology and stratigraphic position, we as the Watson Limestone of Rowley, to be Bryant Knob. conclude that this bed represents the unnamed mem- However, subsequent collecting has reduced the dis- ber of the Bryant Knob, and the coral-rich interval tinction between Noix-Cyrene and Bryant Knob above it marks the base of the Kissenger. The coral- brachiopod assemblages (Amsden, 1986, p. 29). rich interval has been reported at a locality about 2 We follow the interpretation that the Cyrene For- km southeast of Section 16 (Rowley, 1908, p. 20). We mation is a facies equivalent of the combined Noix also found the interval containing abundant solitary 16 Bulletin 333

coralla at the extreme southern end of Section 17 same "mounds" reported by Thompson and Satter-

(Clarksville). There it occurs as a bed that is shale- field. In 1983, slumping along parts of Section 17 ex- bounded in places, overlies the Noix along an irregular posed fresh surfaces. Two irregular patches composed contact, is overlain by the Bowling Green Dolomite of soft, white limestone that was indistinguishable from along an undulator>' surface, and pinches out north- the "mounds" were observed within the Bowling Green ward along the exposure (Text-figs. 5. 6). This bed is Dolomite about 3 m above the Noix. One was situated assigned to the Kissenger. above, and separated from, the southern "mound". The coral-rich interval of the Kissenger Limestone The other, found farther north along part of an inclined contains solitary rugosan coralla that are abraded, have joint or fracture, contained chert nodules at the same algal coatmgs, and have microborings of probable algal stratigraphic positions as the surrounding dolostone. origin associated with micritized surfaces. We consider These observations suggest that areas of limestone at it to be a lag deposit that is likely isochronous. Slrep- the base of, and within, the Bowling Green represent telasnia suhregu/arc (Saxage. 1913b), the only solitary undolomitized portions of this unit, rather than a dis- rugosan species in the interval, also occurs in the un- crete stratigraphic interval. Dalnianophyllum sp. and named member as well as other strata included in the DinophyUiiiu sp. were found in both lithologies. Al- Kissenger Limestone Member of the Bryant Knob For- though Rhegiuaphyllum sp. is recognized only in the mation. The solitary coral assemblage in the basal limestone and Cyalhactisl sp. is known only from the Bowling Green Dolomite at Section 17 (Clarksville), dolostone, these apparent differences may be related both above and lateral to the coral-rich bed, is entirely to the overall rarity of solitary coralla in the Bowling different. We infer that the unnamed member of the Green, and the relatively poor preservation of fossils Bryant Knob is older than the Kissenger Limestone in the dolostone.

Member, which in turn is older than the Bowling Green Age Dolomite. This interpretation, based on the distribution of sol- Berry and Marshall (1971) identified graptolites of itary Rugosa, is consistent with the nature of contacts the Dicellograptus conip/anatus var. ornatus Zone from between the various units in this sequence. Where the an exposure of the Maquoketa Formation in eastern unnamed member of the Bryant Knob Formation is Missouri. The age of these Late Ordovician strata was present {e.g.. Section 18), it overlies the Noix Lime- considered to be within the late Maysvillian to Rich- stone with apparent conformity (Thompson and Sat- mondian interval. terfield, 1975, p. 103). Where the coral-rich interval at Before the 1970's, workers followed Savage's as- the base of the Kissenger Limestone Member of the signment of Edgewood strata in northeastern Missouri

Bryant Knob overlies the Noix, the contact is uncon- to the Early Silurian Alexandrian Series (Savage, 1 9 1 3a, formable (Section 17). The contact between the Kis- p. 352; Thompson and Satterfield, 1975, fig. 1). Liebe senger Limestone and Bowling Green Dolomite is un- (1962, pp. 10, 35) was evidently first to recognize that conformable at some sections {e.g.. Sections 17, 18; conodonts in the Noix Limestone are Ordovician. see Thompson and Satterfield, 1975, pp. 98, 103). We A nwrphognathusordovicicus Branson and Mehl, 1933, conclude that both members of the Bryant Knob For- mation as well as the Bowling Green Dolomite are discrete units, as recognized by Thompson and Sat- terfield (1975, p. 103). Thompson and Satterfield (1975, pp. 89, 100, figs. 13, 14) reported an unnamed unit composed of soft, white limestone present locally at the base of the Bowl- ing Green Dolomite. It was described as thin "lenses" on the Bryant Knob Formation at Section 18 (Kissen- ger), and as two low "mounds" on the Noix Limestone at Section 17 (Clarksville). Thompson and Satterfield noted that the "mound" at the north end of the latter section was associated with an irregularity along the upper surface of the Noix, and was enclosed by a thin shale seam. This unit was not exposed at Section 18 Tcxt-ligurc 6. — Contacts between Kissenger Limestone Member during the present study, but two "mounds" were ob- of the Bryant Knob Formation and underlying Noix Limestone served weathered faces of the exposure at Section on (thumb), and overlying Bowling Green Dolomite (forefinger), ex-

1 7. One was at the north end. and the other was located treme southern end of Section 17 (Clarksville), Pike County, Mis- toward the south. It is uncertain whether these are the souri (photographed m 1983). Ordovician-Silurian Rugose Corals: McAuley and Elias 17

and other laxa indicate a Late Ordovician age (Thomp- as recognized by us were tentatively assigned Late Or- son and Satterfield, 1975, p. 87). McCYackcn and Barnes dovician and Early Llandovery ages by Amsden ( 1 974,

(1982. p. 1477) considered the Noix conodont fauna pp. 14, 15 [Iocs. C and D therein]). to be late Richmondian (see also McCracken and Lenz, Thompson and Satterfield (1975, pp. 96, 97, 101, 1987. p. 649). However, Barrick (1986, pp. 64, 66) 103) identified the Paltodus dyscritus fauna in the suggested that Noixodontus i^irardeaiicnsis (Satterfield, Bowling Green Dolomite (including the unnamed unit

1971) may be restricted to the Hirnantian Stage (i.e.. of those authors), and concluded that this formation late Gamachian). is Early Silurian. They considered conodonts in eastern

Thompson and Satterfield ( 1 975, p. 93) reported the exposures to be younger than those in western sections Late Ordovician Prioniodiis fcnahus conodont fauna on the basis of three specimens identified as Neospath- from strata at Section 14 (Higginbotham Farm) that ognathodus celloni (Walliser, 1964). McCracken and were assigned to the Bryant Knob Formation by Ams- Barnes (1982, p. 1475) suggested that the latter con- den (1974, p. 83, loc. A) and by us. Conodonts in the odonts represent Oulodusi cf. O.l nathani McCracken unnamed member at the base of the Bryant Knob in- and Barnes, 1981, of which they found one specimen clude representatives of .A niorplwgnathus ordovicicus in the Bowling Green. They inferred that the fauna in Branson and Mehl. 1933, Icriodellal sp., and the Pal- this unit may represent the Early Llandovery Oulodus? todusdyscritiis fauna (Thompson and Satterfield, 1975, nathani or Distoniodus kentuckyensis conodont zones p. 97, figs. 10, 14). These conodonts, as well as grap- (McCracken and Barnes, 1982, pp. 1474. 1477). How- tolites (Berry, written commun., 1971, cited in Thomp- ever, the Ordovician-Silurian boundary defined as the son and Satterfield, 1975, pp. 97, 98), were considered base of the Parakidograptus acuminatus Graptolite to indicate an Early Silurian age (Thompson and Sat- Zone (Cocks, 1985) may be situated within the O.l terfield, 1975, pp. 72, 101). The overlying Kissenger nathani Tone (Lesperance, 1985, figs. 3, 4; McCracken Limestone Member of the Bryant Knob contains A. and Nowlan, 1988, p. 77). ordovicicus as well as the Phoniodus ferrariiis and Pal- The brachiopod Platymerella manniensis Foerste, todus dyscritus faunas, and was also assigned an Early 1 909, was reported at the base of the Sexton Creek Silurian age (Thompson and Satterfield, 1975, p. 101, Limestone (Kankakee Formation), which locally over- figs. 10, 12, 14, 15). However, Nowlan (//; Bolton and lies the Bowling Green Dolomite, by Savage (1913b, Nowlan, 1979, pp. 5, 21) suggested that mixed faunas p. 30; 1917.p.88),Willman(1973,p. 16).and Willman including .4. ordovicicus and P. dyscritus Rexroad, 1967, and Atherton (1975, p. 97). This zone was placed in might be Late Ordovician, based on an occurrence in the Middle Llandovery by Berry and Boucot (1970, pi. undoubtedly Ordovician strata in the District of Kee- 2). Specimens of Stricklandia triplesiana (Foerste, watin. The Bryant Knob Formation was tentatively 1890), with an interior similar to Stricklandia lens ul- assigned to the Early Silurian (Early Llandovery) by tima Williams, 1951, from the Sexton Creek in Illinois Amsden (1971b, pp. 21, 22 [the younger Edgewood were considered to be Late Llandovery (C4.5) by Ams- zone therein includes the Bryant Knob]; 1974, p. 14). den (1974, pp. 18, 24; 1986. p. 41). He based this primarily on stratigraphic position and Age assignments we follow are shown in Text-figure the absence of certain characteristic Noix brachiopods, 5, and discussed further on pp. 25, 26. but subsequent collecting demonstrated that some of Paleoenvironment the species previously thought to have been confined to the Bryant Knob are also present in Noix-Cyrene Savage (1914, p. 30) concluded from the lithostrat- strata (Amsden, 1986, p. 29). igraphic record that the sea in which the lower Edge-

Thompson and Satterfield (1975, p. 96, fig. 11) re- wood Group formed was deepest in the west, where ported Amorphognathus ordovicicus Branson and Mehl, the Cyrene Formation accumulated, and became pro- 1933, as well as the Prioniodus ferrarius and Paltodus gressively shallower toward the eastern margin, where dyscritus conodont faunas in the Cyrene Formation. the Noix Limestone and Bryant Knob Formation were They considered this unit to be Late Ordovician, but deposited. The shoreline gradually receded westward, we equate it with the combined Noix Limestone and reaching a position a few km west of Louisiana, Mis- Bryant Knob Formation. The conodont Noi.xodontus souri. Deposition of the Bowling Green Dolomite was girardeauensis (Satterfield, 1971) is present in the up- initiated by a slight uplift west of the basin, accom- per middle portion of the Cyrene at Section 13 (Bowl- panied by subsidence resulting in an eastward overlap ing Green) (see Thompson and Satterfield, 1975, fig. on the Noix and Bryant Knob surface. Sedimentation

1 1) and in the Noix. The Paltodus dyscritus fauna first was uninterrupted to the west, where the Bowling Green appears definitely in the upper portion of the Cyrene overlies the Cyrene.

(Thompson and Satterfield, 1975, p. 101) and in the Thompson and Satterfield (1975, pp. 93, 103. fig. Bryant Knob. Brachiopods in the Cyrene Formation 16) interpreted the coarse, bioclastic limestone at Sec- Bulletin 333

tion 14 (Higginbotham Farm) as a bioherm situated 4 and 5 (Schweizer North) (Willman, 1973, pp. 12- beneath the Br>ant Knob Formation. We consider these 14). The Wilhelmi is up to 30 m thick where it fills or strata to be a coquina and include them in the Br>ant nearly fills channels eroded into the underlying Maquo- Knob (see also Amsden. 1974, p. 83, loc. A). They keta Group, but is thin or absent elsewhere in the area. suggested that this deposit may have been a source of The Schweizer Member, which is up to 24 m thick, is nuclei for ooids that formed to the east, and acted as generally present only where the formation is relatively a barrier that separated Noix and Cyrene deposition. thick. The lower portion consists primarily of gray, Conodont assemblages indicate that the Noix Lime- dolomitic shale, whereas the upper part is very argil- stone formed in relatively shallow water, and the Bowl- laceous, silty, thinly bedded dolostone. This unit is ing Green Dolomite was deposited during a transgres- overlain conformably by the Birds Member, which is sion (McCracken and Barnes. 1982, p. 1477). On the up to 6 m thick. The Birds is a gray, slightly argilla- basis of conodont data, Thompson and Satterfield ceous, typically flaggy dolostone. At Section 3 (Garden

( 1 975. p. 97) concluded that deposition of the Bowling Prairie), the basal bed above the Maquoketa and the

Green began earlier at Section 1 3 (Bowling Green) in overlying flaggy dolostone were identified as the Wil- the west than at Section 1 7 (Clarksville) in the east. helmi Formation by Willman (1973, p. 12) and are However, McCracken and Barnes (1982, pp. 1475, assigned to the Birds Member by us. 1477) considered conodonts from the latter section to The Wilhelmi Formation unconformably overlies represent an earlier zone than that indicated by strata of the Maquoketa Group, ranging from the up- Thompson and Satterfield. Local structural move- permost unit, the Neda Formation, down to the top ments possibly contributed to the complex facies re- of the Fort Atkinson Limestone, which underlies the lations and unconformities in the Edgewood sequence Brainard Shale. The Wilhelmi is overlain conformably (Thompson and Satterfield, 1975, p. 103). by slightly argillaceous to pure dolostone of the Elwood Most solitary rugosan coralla in the Bryant Knob Formation, which contains numerous layers of chert Formation are abraded, suggesting relatively high en- (Willman, 1973, p. 14). Dolostone of the Kankakee ergy levels and comparatively low sedimentation rates. Formation overlies the Elwood conformably. The highest proportions of abraded specimens observed in this study are from the coral-rich interval at Biota the base of the Kissenger Limestone Member. Algal Fossils from the Wilhelmi Formation at exposures coatings are relatively on solitary coralla and common along Des Plaines River about 1.6 km, 3.2 km, and bioclastic grams in that interval, and some of the coral- 5.6 km to the south of Channahon were identified by la have probable algal microborings associated with Savage (1913b, pp. 26, 27; 1914, p. 31; 1917, pp. 84, micritized surfaces. These features suggest transpor- 85 [the Channahon Limestone therein]). He recognized tation and prolonged exposure before burial, and we brachiopods, gastropods, pelecypods, cephalopods, tri- interpret the coral-rich interval as a lag deposit. The lobites, ostracodes, tabulate corals, and solitary rugose directional orientation pattern for solitary coralla in corals. Fisher(1925, pp. 26, 27 [the Edgewood therein]) this interval at Section 16 (Clinton Spring) indicates reported brachiopods and trilobites from a section of perpendicular to water that they were rolled almost platy dolostone, which possibly represents the Birds or nearly parallel to wave crests, with currents flow Member of the Wilhelmi, along Du Page River about from the northwest (Elias, McAuley, and Mattison, 7 km north of Channahon. The section south of Bel- 1987, p. 810). The paleocurrent direction is parallel to videre that was described by Savage ( 1 926, p. 5 1 8 [the depositional strike of the Bryant Knob and to the in- Edgewood limestone therein]) is very similar to Sec- shoreline, suggesting longshore currents and per- ferred tions 34 (Belvidere South) and 3 (Garden Prairie). He waves. haps identified solitary rugose corals from unit 3 (his terminology), which we assign to the Birds Member. Northeastern Illinois The following groups have been listed from the Wil- Lithostratigraphy helmi Formation along Horse Creek about 2.4 km east The lithostratigraphic terminology we use (Text-fig. of Essex: brachiopods, gastropods, pelecypods, algae?,

7) follows Willman ( 1 973, pp. 6. 9. 1 2-1 7, fig. 6), who tentaculitids, cornulitids, conularids, tabulate corals, summarized the history ofnomenclaturc (see also Will- and solitary rugose corals (Savage, 1913b, p. 29; Sav-

man and Buschbach, 1975, p. 86, fig. 0-27; Willman age, 1917, p. 87; Athy, 1928, pp. 40, 41 [the Essex and Atherton. 1975, pp. 96, 97, fig. S-7). Limestone therein]). From the same unit along Horse The type section of the Wilhelmi Formation, as well Creek 0.4 km west of Custer Park, Athy (1928, p. 41) as the Schweizer Member, is Section 4 (Schweizer West), reported brachiopods, trilobites, algae?, and tentacu- and the type section of the Birds Member is Sections litids. Ordovician-Silurian Rucjose Corals: McAuley and Elias 19

Ross (1962 [the Edgcwood Formation therein]) de- Schwci/er Member at .Section 4 (Schwei/er West). Sco- scribed graptolitcs from a silty dolostone bed situated lecodont fragments were reported in the Wilhclmi-

7.6 ni (shown at 4.6 m in his fig. I ) above the base of Elwood sequence of northeastern IHinois by Buschbach the Wilhelmi Formation, in the upper part of the ( 1 964. p. 59 [the Edgewood Formation therein]). Liebe

io o "

•34 20 Bulletin 333

and Rexroad (1977, figs. 2. 4) listed conodonts from iisl sp. is present. At Section 7 (Kankakee River), sol- the Schweizer Member of the Wilhelmi Formation at itary coralla were not found in the 0.3-m-thick Wil- Section 4, and from the Birds Member at Sections 4 helmi Formation, or in the underlying Neda Formation and 5 (Schweizer North) and National Quarr>' on the of the Maquoketa Group. The Kankakee Formation south side of Joliet. Mikulic et al. (1985, pp. 10. 32, overlies the Wilhelmi at that location. The distribution 33) also reported conodonts from the Wilhelmi at Na- of solitary corals in northeastern Illinois is shown in tional Quarr>'. and noted inarticulate brachiopods, tri- Text-figure 7. lobites. and trace fossils in the basal, shaly strata, and In eastern Wisconsin at High Cliff Park (see Text- pelmatozoan debris, brachiopods, br>ozoans, gastro- fig. lA), Willman (1973, p. 13) noted that the lower 3 pods, cephalopods, and trilobites in the upper, dolo- m of the Mayville Dolomite, which overlies the mitic strata. Conodonts, brachiopods, gastropods, and Maquoketa Shale, resemble the Wilhelmi Formation, trilobites are present in the Wilhelmi at Section 29 and the overlying 6 m of Mayville are like the Elwood

(Sears Pit) (Mikulic et al.. 1985, p. 23). Formation. During the present study, solitary rugosan Elias (1982a) studied two collections of solitary ru- coralla were not observed in that basal 3-m-thick unit, gosan coralla made by Savage from the unit he termed or in immediately overlying strata, of the Mayville. Channahon Limestone. These included specimens that Willman (1973, p. 13) stated that the Mayville Do-

Savage (1913b) identified and illustrated as two new lomite at Katell Falls (see Text-fig. 1 A) consists largely species, Zaphrentis ainhigua and Zaphrentis siibregii- of Kankakee lithology, but that approximately the low-

larts. Elias concluded that they represent one species, er 1 m overlying the Neda Formation is similar to the Streplelasina siibregidare (Savage, 1913b). Savage Wilhelmi. Solitary coralla were not found in the lower

( 1 9 1 3b, p. 26; 191 7, p. 84) reported numerous solitary 1 m of the Mayville or in the Neda at that section coralla in unit 2 (his terminology) of the Channahon during the present study. Katell Falls is the only locality Limestone at a section located 1.6 km southeast of at which the Neda is known to contain fossils (Savage Channahon. He noted that corresponding strata are and Ross, 1916, p. 191; Mikulic and Kluessendorf,

exposed above Maquoketa shale 1.6 km farther south 1 983, p. 29), but solitary corals have not been reported. (Savage, 1914, p. 31; see also Savage, 1916, p. 306), Beneath the Mayville in the vicinity of Little Sturgeon suggesting a position near the base of the Wilhelmi Bay (see Text-fig. lA), E. O. Ulrich observed a coral-

Formation. Elias ( 1 982a, p. 40) assumed that Savage's rich dolostone unit up to 2 m thick that apparently fills specimens came from Wilhelmi beds that lie strati- a channel at the top of the Maquoketa shale and is in graphically above the graptolite bed of Ross, based on places overlain by a thin interval of the Neda (Mikulic

statements by Ross ( 1 962, p. 1 385) and Willman (1973, and Kluessendorf 1983, p. 36, figs. 27, 28). Elias pp. 12, 13). From collections made during the present (1982a, pp. 29, 67, fig. 18, pi. 10, fig. 8) identified the

study at Section 4 (Schweizer West), it is apparent that solitary rugosan species Grewingkia canadensis (Bil- S. suhregnlarc occurs in the Schweizer Member, below lings, 1862) in Ulrich's collection from the coral-rich and above the position of the graptolite bed. Brachio- unit. pods. bryozoans, gastropods, trilobites, cornulitids, co- Age lonial corals, and solitary corals were observed at the latter locality. The history of age assignments for Maquoketa strata During the present study, we examined additional in Illinois was summarized by Willman and Buschbach solitary coralla obtained by Savage in the vicinity of (1975, pp. 81, 83, 84, fig. 0-27). It is inferred that the Channahon. Slreptelasma siihregulare (Savage. 1913b) Maquoketa Group in northern Illinois is probably pri-

is the only taxon that is represented. The same species marily Maysvillian and Richmondian, based mainly occurs in his collections made along Horse Creek and on conodont data (Kolata and Graese, 1983, pp. 5, 6; near Belvidere, and is common in a bed of the Birds Mikulicz/ a/.. 1985, pp. 6, 8). Savage and Ross (1916,

Member. Wilhelmi Formation, exposed on the quarry p. 191) and Savage ( 1 9 1 6, p. 309) reported that fossils floor at Section 34 (Belvidere South; interval 34-1). from an undisturbed zone in the Neda Formation of Streptelasma sithregulare was also found in the Birds eastern Wisconsin show little evidence of wear, are Member at Section 3 (Garden Prairie) and at the base characteristic of the Maquoketa shale, and indicate a of the undivided Wilhelmi at Section 29 (Sears Pit). Richmondian age. Mikulic (1979; see Mikulic and Solitary coralla were not observed in the Birds Member Kluessendorf 1983, p. 3) found occurrences of Brain- at Section 5 (Schweizer North). Rhcgmaphylluin sp., ard-likc deposits overlying the Neda, suggesting a re- Dinophylliim sp., and Dalmanophyllum sp. appear at lation to Maquoketa sedimentation. the base of the Elwood Formation at Section 5, and The history of age assignments for strata overlying the latter two occur in the upper Elwood at Section 6 the Maquoketa Group in northeastern Illinois was (Plaines West). In the Elwood at Section 29, Cyathac- summarized by Willman (1973, pp. 3, 5, fig. 6) and Ordovician-Sii.urian Rucjose Corals: M( Aui.by and Elias 21

Willman and Alhcrton (1975, (ig. S-7). Ross (1962) the Wilhelmi is slightly argillaceous and the overlying considered graptolitcs from a bed in the upper part of Elwood Formation contains little or no clastic mate- the Schwei<^er Member, Wilhelmi Formation, to rep- rial. Liebe and Rexroad (1977, p. 844) reported that resent a subzone at the top of the Fanikich>,K'raplii.s reworked Ordovician conodonts decrease in abun- aciiniinatiis Zone in Wales or the basal part of the dance upward in the Schweizer, and occur sporadically

Orthograptiis vcsicu/osus Zone in Scotland. An Early above it. Silurian (Early Llandovery) age was confirmed by Ber- The lithologies and bedding in the Wilhelmi For- ry (/>; Berry and Boucot, 1970, p. 145). Conodonts of mation suggest deposition in relatively low energy con- the Schweizer have been assigned to the Faiulcrodus ditions. All solitary rugosan coralla from the Wilhelmi simplex Zone, inferred to be Early Llandovery, by Liebc in the vicinity of Channahon and at Section 34 (Bel- and Rexroad (1977, pp. 848, 849, fig. 5) and Rexroad videre South) are nonabraded, also suggesting a low and Droste (1982, pp. 10, 12, fig. 6). However, cor- energy environment and perhaps a high sedimentation relation and age assignments on the basis of these con- rate. odonts are unreliable because diagnostic, biostrati- Northwestern Illinois and Eastern Iowa graphically important taxa are not present (Liebe and

Rexroad, 1977, p. 848; Mikulic et ai. 1985, p. 16). Lithostratigraphy Conodonts in the Birds Member of the Wilhelmi For- The lithostratigraphic terminology we use (Text-fig. mation and the overlying Elwood Formation were as- 8) follows Willman (1973, pp. 26, 27, 29. 31-36, fig. signed to the Ozarkodina hassi interval, which was 9), who summarized the history of nomenclature (see included at the base of the Icnodina irregularis Zone also Willman and Atherton, 1975, pp. 98. 99, fig. S-8). (= Paltodus dyscritiis fauna of Thompson and Satter- The type section of the Mosalem Formation is Sec- field, 1975; = Dislomodus kentuckyensis Zone of Coo- tion 8 (King) (Willman, 1973, p. 32). The Mosalem is that O. per, 1975). Mikulic et al. (1985, p. 10) noted up to 30 m thick where it fills channels eroded into hassi (Pollock, Rexroad, and Nicoll, 1970) suggests a the underlying Maquoketa Group, but thins almost to Middle to early Late Llandovery age, but the range of absence above paleotopographic highs (Brown and that taxon may extend down into the latest Ordovician Whitlow, 1960, pp. 34, 36-39, figs. 9, 10; Whitlow and and Nowlan, 77). (McCracken 1988, p. Brown, 1963, pp. 1 1, 13, fig. 62.2; Willman, 1973, pp. The brachiopod Platymerella manniensis Foerste, 31-33). Where the Mosalem is relatively thick, the

1 909, has been reported from the upper Elwood For- lower part is composed of gray, dolomitic shale and mation and basal Kankakee Formation by Savage very argillaceous dolostone. The clastic content de-

( 1 9 1 3b, p. 3 1 ; 1 9 1 7, p. 89 [the Sexton Creek Limestone creases upward. The upper portion of the unit consists therein]), Willman (1973, pp. 14, 15), and Willman of slightly argillaceous dolostone with a few bands of

and Atherton (1975, p. 97). This zone was placed in chert. Where the Mosalem is comparatively thin, only

the Middle Llandovery by Berry and Boucot ( 1 970, pi. the upper, dolomitic portion is present. This formation 2). unconformably overlies strata of the Maquoketa Group Age assignments we follow are shown in Text-figure ranging from the Neda Formation, preserved on pa- 7, and discussed further on pp. 25, 26. leotopographic highs, down into the underlying Brain- ard Shale. Within channels, the base of the Mosalem Paleoenvironment is characterized by a thin, persistent conglomerate con- The Wilhelmi Formation was deposited during a taining clasts derived from the Maquoketa.

transgression that followed a period of erosion, as rec- The Mosalem Formation is overlain with apparent ognized by Savage (1913b, pp. 34, 35; 1916, p. 314; conformity by massive, vuggy, pure dolostone of the 1917, p. 92 [the Edgewood therein]). Willman (1973, Tete des Morts Formation in the northern part of this p. 12) noted that this unit occupies channels that had area, and by relatively pure, cherty dolostone of the been cut into the Maquoketa Group. The irregular sur- Blanding Formation in the south. face of the Maquoketa exhibits more than 30 m of Biota relief in places (Mikulic et ai. 1985, p. 9). The basal

bed of the Wilhelmi is conglomeratic at Section 4 Brachiopods and trilobites from the Mosalem For- (Schweizer West), and contains clasts of Maquoketa mation in the vicinity of Section 26 (Bellevue) were

shale at Section 3 (Garden Prairie). The Schweizer reported by Savage ( 1 906, p. 60 1 [the transition beds

Member, which is very argillaceous and silty. occurs therein]). From a locality near Section 9 (Winston), he only in the deeper parts of major channels (Willman, listed inarticulate and articulate brachiopods, and tri-

1973, p. 13). As the surface of the Maquoketa became lobites (Savage, 1914, p. 34 [the Winston Limestone covered, the amount of argillaceous material in the therein]). Brachiopods, trilobites, and solitary rugose overlying deposits decreased. The Birds Member of corals from near the base of the Mosalem in the vicinity 1

Bulletin 333

of Section 30 (Thomson Northeast) were listed by Sav- served for identification, as are specimens at Section age (1926. p. 527 [the lower part of the Edgewood 30 (Thomson Northeast). At Section 32 (Thomson

Limestone therein]). East), Streptelasma subregularc (Savage, 1 9 1 3b) is rare Brown and Whitlow (1960. pp. 37-39) stated that 0.65 to 0.70 m above the base of the Mosalem exposure brachiopods, br\ozoans. and trilobites are the domi- (interval 32- la). Lateral to those coralla are local chan- nant fossils in the Mosalem Formation of Dubuque nels that cut down from a position 0.8 m above the

County. Iowa. They noted minute objects that are base of the section (interval 32- 1 b). They are filled with probabh conodonts. especially in the basal 1.5 m where argillaceous dolostone, are shale-bounded, and contain burrow mottling is common. At localities where the uncommon specimens of 5'. siibregitlare and abundant Mosalem is thin, possible algal stromatolites were re- remains of fasciculate colonial rugose corals we iden- ported at the base. In the lowermost bed of the for- tify as Pycnostylus'? sp. (Text-fig. 9). Streptelasma sub- mation at one section, small phosphatic fossils resem- regulare is common with tabulate corals in a bed bling the "depauperate fauna" at the base of the exposed on the old quarry floor to the west (interval Maquoketa Group were observed. Comminuted fossil 32- Iz). That bed appears to be at about the same strati- fragments from the Cornulites zone in the upper Brain- graphic position as intervals 32- la and 32- lb. Dal- ard Shale were noted within the basal conglomerate of manophyllum sp. occurs at heights of 2.2 and 3.75 m the Mosalem. above the base of the exposure, RhegmaphyUum sp. is Ross (1964) documented graptolites from a horizon present at 3.95 m, and DinophyUum sp. was recovered situated about 3.4 m above the base of the Mosalem between 3.95 and 4.45 m. DahuanophyUiini sp. and Formation as currently recognized at Section 26 (Belle- Cyathactisl sp. were found near the top of the Mosalem vue)(see Rose. 1967, p. 45, fig. 21). He reported typical at Sections 10 (Lost Mound) and 9 (Winston), respec- Maquoketa fossils from the basal 0.6-m-thick con- tively. The distribution of these solitary corals is shown glomeratic, silty, dolomitic calcarenite of the Mosalem in Text-figure 8. One unidentifiable specimen was also at that locality (Ross, 1964, p. 1107), but it is not found in the upper 2 m of the Mosalem at Section 1 known if they were reworked. Whitlow and Brown (Schapville). Solitary coralla were not observed in this

(1963. p. 13) noted phosphatic fossil fragments in that formation at Sections 8 (King) and 12 (Stockton). Sal- bed. vadorea raiidi (Elias, 1981) was described from the During the present study, three solitary rugosan cor- Brainard Shale of the Maquoketa Group at Sterling, alla were collected from an interval situated 1.8 to 2.4 Illinois, and in Clayton County, Iowa, by Elias ( 1 982a, m above the base of the Mosalem Formation at Section pp. 61. 62, pi. 6. figs. 1-7; 1985. p. 45; see Text-fig. 26 (Bellevue). Unfortunately, they are too poorly pre- lA).

= ^ SECTION 32 ; uj U 5 (THOMSON EAST) ? •

3 and = ! " I SECTION 30 " (THOMSON NORTHEAST) Ordovician-Silurian Ruciosn Corals: McAuley and Elias 23

Age SOLITARY RUGOSE CORAL ASSEMBLAGES

The history of age assignments for Maquoketa strata Four solitary rugosan assemblages are recognized in in Illinois was summarized by Willman and Buschbach the uppermost Ordovician-lowermost Silurian se- lithostrat- in ( 1 975, pp. 8 1 , 83, 84, fig. 0-27). Faunal and quence within the study region the east-central igraphie eorrclation of the upper Brainard Shale and United States: (1) Late Ordovician "epicontinental" uppermost Cornu/iWs zone of the Brainard in Iowa and assemblage (Richmondian); (2) Late Ordovician "con- Illinois with the Late Ordovician (latest Richmondian) tinental margin" assemblage (Gamachian); (3) Edge- "Elkhorn" strata in the Cincinnati Arch region was wood assemblage (Gamachian-early Early Llandov- considered highly probable by Ladd (1929, pp. 369, ery); and (4) Silurian assemblage (post-Edgewood

370) and Templeton and Willman ( 1 963, pp. 1 32, 1 33). Llandovery) (Text-fig. 10, Table 1). The lowest is a On the basis of conodonts, Glenister (1957, pp. 720, Late Ordovician "epicontinental" assemblage in the 721) assigned the Maquoketa Group of eastern Iowa upper Maquoketa Group. Salvadorea randi (Elias, to the Maysvillian through Richmondian. Specimens 1981), a Maysvillian-Richmondian species (Elias,

of the Maysvillian-Richmondian solitary rugosan 1 985, p. 45), is present in the Orchard Creek and Brain- species Salvadorea raiidi (Elias, 1981) in the Brainard ard shales (Elias, 1982a, pp. 35, 36). Grewingkia can- Shale arc considered to be Richmondian on the basis adensis (Billings, 1862) occurs immediately below the of their position above the Fort Atkinson Formation, Neda Formation in eastern Wisconsin (Elias, 1982a, which contains the Richmondian species Bighornia p. 29). It is a Richmondian species (Elias, 1982a, p. palc/la {Wihon. 1926) (see Elias. 1987). 67). The history of age assignments for strata overlying The upper, Silurian assemblage includes Dinophyl- the Maquoketa Group in northwestern Illinois and the him sp., Dalmanophyllum sp., Cyalhactis'! sp., and adjacent area in Iowa was summarized by Willman Rhegmaphyllum sp. These genera are typical of the

(1973, pp. 29, 31, fig. 9) and Willman and Atherton Early to Middle Silurian (Hill, 1981, pp. 159-161, 163,

( 1 975, fig. S-8). Ross ( 1 964) noted that graptolites from 308), and are present in the late Early to Late(?) Llan- a bed about 3.4 m above the base of the Mosalem dovery Brassfield Formation of the Cincinnati Arch Formation apparently represent the same Early Silu- region in Kentucky-Indiana-Ohio (Laub, 1979). rian (Early Llandovery) zone as those in the Schweizer One of the genera in the Silurian assemblage has Member of the Wilhelmi Formation in northeastern recently been found in Late Ordovician deposits near Illinois. The age of units overlying the Mosalem For- the North American continental margin. At Pointe

mation is imprecisely known, because important bio- Laframboise on Anticosti Island, Quebec, Rhegma-

stratigraphic marker zones are absent. phyllum sp. appears in the basal 1 m of the Becscie Age assignments we follow are shown in Text-figure Formation (Elias and Petryk, unpublished data; see

8, and discussed further on pp. 25, 26. Petryk, 1981a, fig. 11), in beds considered to be late

Gamachian. The specimens occur about I m above the Ordovician-Silurian boundary of conodont workers (McCracken and Barnes, 1981). but strata equiv- Paleoenvironment

The Mosalem Formation was deposited during a transgression, as recognized by Savage (1914, p. 34

[the Winston Limestone therein]; 1926, p. 528 [the Edgewood Limestone therein]). Brown and Whitlow (1960, p. 36) concluded that the Mosalem was deposited in a shallow marine environment as a sea ad- vanced over the eroded Maquoketa surface. While sediment accumulated in low areas, topographic highs continued to be eroded, either above or below sea level. The detrital content of the Mosalem decreased as the summits became covered with marine deposits. Ero- sional relief on the Maquoketa is 41 m in Dubuque County, south of Dubuque, Iowa (Brown and Whitlow,

1960, p. 23; Whitlow and Brown. 1963, p. 11). Small, local channels in the upper Mosalem at Section 32 Text-figure 9. — Small, local channel wittiin Mosalem Formation (Thomson East) may record a minor regressive event at Section 32 (Thomson East), Carroll County, Illinois (assistant during the transgressive phase. pointing to base and top of channel, photographed in 1986). 24 Bulletin 333

alenl in age to the basal Silurian Parakidograptus Table 1. — Latest Ordovician to earliest Silunan solitar>' rugose corals in the study region, east-central United States. acuminatus Graptolite Zone may be much higher in

(Lesperance, 1985. fig. 3; the sequence McCracken and Silurian Assemblage Nowlan. 1988. p. 77). Coralla of Rhegmaplniluni sp. Suborder Streptelasmatina are associated with Greningkia pulchella (Billings. Family Streptelasmalidae Subfamily Streptelasmatinae 1865), a species that is also present in the Ellis Bay Rhegmaphyllum sp. Formation (Gamachian) and upper member of the Subfamily Dinophyllinae Vaureal Formation ( Richmondian) on Anticosti Island Dinophyllum sp.

(Elias. 1 982a. p. 45). In the southeastern United States, Subfamily Dalmanophyllinae Rhegmaphylluiu sp. occurs in strata considered to be Dalmanophyllum sp. Suborder Cyathophyllina Richmondian (Elias and Stock, unpublished data). It Family Ptychophyllidae has been found, together with Greningkia sp. cf G. Cyalhaclis"^ sp. pulchella (Billings, 1865). in the Sequatchie Formation Edgewood Assemblage [Edgewood Province] at Birmingham, Alabama (see Drahovzal and Neath- Suborder Streptelasmatina er>', in 1971, pp. 25, 237, stop 10). and the Shellmound Family Streptelasmatidae Formation at Pope Spring. Georgia (see Milici and Subfamily Streptelasmatinae Wedow. 1977. pp. 8, 9. 33, sec. 26b) (for age of strata. Streptelasma subregulare Streptelasma cf. subregulare see also Colbath, 1986, p. 945). In the Beaverfoot For- sp. 5. Streptelasma amsdeni mation of southeastern British Columbia, Rhegma- Streptelasma leemonense phylluni sp. and Streptelasiua sp. are present in latest Streptelasma sp. cf S. leemonense Ordovician or possibly earliest Silurian strata above Streptelasma sp. A the Bighornia-Thaerodonta Assemblage Zone, which Grewingkia sp. ,A Subfamily Dalmanophyllinae is probably entirely Richmondian (Bottler, Elias, and Bodophyllum shorti Norford, 1988. pp. 59, 60). At the St. Clair Spring Suborder Monacanthina Section in eastern north-central Arkansas, Rhegma- Family Lambclasmatidae phyllum sp. is the only solitary coral in the Cason Subfamily Coelostylinae oolite, which is considered to be Gamachian (Himan- Keelophyllum oklahomense tian) in age (Amsden. 1986, pp. 20, 22, 26; Barrick, Late Ordovician "Continental Margin" Assemblage 1986, pp. 64. 66). This occurrence represents the Late Suborder Streptelasmatina Ordovician "continental margin" assemblage within Family Streptelasmatidae Subfamily Streptelasmatinae the present study region. Rhegmaphyllum sp. Our study is focused on the assemblage that is here Late Ordovician 'Epicontinental" Assemblage termed the Edgewood. It is situated stratigraphically Suborder Streptelasmatina between the Late Ordovician "epicontinental" and the Family Streptelasmatidae Silurian assemblages, and geographically lateral to the Subfamily Streptelasmatinae "continental margin" assemblage. Of the 709 speci- Salvadorea randi [Red River-Stony Mountain mens identified at the species level, percentages rep- Province] Grewingkia canadensis [Richmond Province] resenting the various taxa are as follows: Streptelasma subregulare (Savage, 1913b), 83.1%; Streptelasma sp. cf S. subregulare (Savage. 1 9 1 3b), 0.1%; Streptelasma amsdeni. n. sp., 10.0%; Streptelasma leemonense Elias, marily to taxa from various Late Ordovician (Rich- 1982a, 4.7%; Streptelasma sp. cf S. leemonense Elias, mondian-Gamachian; Ashgill. including Hirnantian) 1982a, 0.4%; Keelophyllum oklahomense, n. gen., n. and Early Silurian (Llandovery) units in North Amer- sp., 0.9%; Streptelasma sp. A, 0.4%; Grewingkia sp. ica and Baltoscandia, and a latest Ordovician (Hir- A, 0.3%; and Bodophyllum shorti Elias, 1982a, 0.1%. nantian) unit in China (see pp. 40-49, 53). However,

Streptelasma subregulare is the most widely distrib- the overall assemblage, in which 97.8 percent of spec- uted species, followed by S. leemonense. imens belong to Streptelasma subregulare (Savage, 1913b), Streptelasma amsdeni. n. sp., and Streptelas- AGE OF UNITS REGIONAL AND ma leemonense Elias, 1982a, seems to be most similar CORRELATION to that in the Dalmanitina Beds (Hirnantian) or pos- The stratigraphic position of the Edgewood solitary sibly earliest Llandovery beds of Ostergotland, Swe- rugosan assemblage between Late Ordovician (Rich- den, and the Guanyinqiao Beds (Dalmanitina Beds; mondian) and typical Early to Middle Silurian assem- Hirnantian) of Guizhou Province, China. Of the four blages suggests an age in the range of latest Ordovician species comprising the Swedish assemblage (see Neu-

to earliest Silurian. The species are comparable pri- man, 1975, p. 336), three are similar to some speci- Ordovician-Silurian Rugose (orals: McAuley and Elias 25

mens ofS. suhregulaiciStrcptelastyia unicuni Ncuman, equivalent to the upper part of the Gamachian in the 1975, llclicelasina simplex Ncuman, 1969, and lior- North American succession (Cocks and Copper, 1981, clasma cras.sitangens Ncuman, 1969), one resembles p. 1033; Lesperance, 1985, p. 844, fig. 4; McCracken, S. umsdeni (S. unicuni), and one is comparable to S. 1987, p. 1454, fig. 2). assignment of Keel-Edgewood leemonense (Streptclasma ostrogothicuni Ncuman, strata to the Himantian implies an unconformable re- 1969). Many coralla from the Chinese assemblage, il- lationship with the underlying Sylvan-Maquoketa beds, lustrated by He (1978, 1985), resemble specimens of which are accepted as Richmondian. Although this

5'. subrci^itlarc and .S". amsdeni (see pp. 42, 45). contact is clearly unconformable in most areas, Ams-

1 1 1 indicated that deposition Amsden ( 1 97 1 b, pp. 2 1 , 22; 1 974, p. 26) considered den ( 980, p. 0; 986, p. 6) the Keel-Edgewood brachiopod assemblage in south- may have been continuous from the Sylvan to the Keel. central Oklahoma, southern Illinois and southeastern Therefore, use of the term Gamachian is followed herein Missouri, and northeastern Missouri and west-central for this North American sequence. Streptelasma sub- Illinois to be characteristic of the latest Ordovician regu/are (Savage, 1913b), Streptelasma leemonense (late Ashgill) to earliest Silurian (Early Llandovery). Elias, 1982a, Grewingkia sp. A, and other solitary cor- He noted that brachiopods in the Keel Formation, als in the Keel, Leemon, Noix, and middle Cyrene, are Leemon Formation, and Noix Limestone most closely considered to have first appeared in the east-central resemble the latest Ordovician Hirnantia fauna, but United States during Gamachian time. the species are different. It was suggested that this may Correlation of the Keel-Edgewood with strata in be due, at least in part, to ecologic factors. Amsden north-central Arkansas is indicated by the following: (1986. pp. 18, 20, 22, 41, 42) concluded that brachio- Ordovician (possibly Himantian) conodonts in the Ca- pods in the Keel, Cason oolite, Leemon, Noix, and son oolite and dolomitic shale (Craig, 1969; Craig. Cyrene formations indicate a latest Ordovician Hir- 1975b. pp. 77, 80, 85; Craig in Craig, Ethington. and

nantian {i.e.. late Gamachian) age. The brachiopod as- Repetski, 1986, pp. 18, 19; Barrick, 1986); brachio- semblage in the Bryant Knob Formation, which over- pods of Himantian aspect in the Cason oolite (Ams- lies the Noix in northeastern Missouri, was initially den, 1986, pp. 20, 22, 26); and the presence of Strep- thought to be different in some respects, and was ten- telasma leemonense Elias, 1982a, and Streptelasma sp. tatively assigned to the Early Llandovery almost en- cf. 5. subregulare (Savage, 1913b) in Cason dolomitic tirely on the basis of associated conodonts (Amsden, shale. The Cason oolite, which contains Rhegmaphyl- 1971b, p. 22; Amsden, 1974, p. 26). However, sub- liim sp., and dolomitic shale are considered Gama- sequent collecting demonstrated that some ofthe species chian in age (Text-fig. 10). previously thought to have been confined to the Bryant In northeastem Illinois, Streptelasma subregulare Knob are also present in Noix-Cyrene strata (Amsden, (Savage, 1913b) is present in the Schweizer and Birds 1986, p. 29). members of the Wilhelmi Formation. It occurs both Brachiopods of the lower Edgewood assemblage were below and above a bed in the upper Schweizer that provisionally considered to be post-Himantian by Les- contains Early Llandovery graptolites, which possibly perance (1974, p. 22). Lesperance and Sheehan (1976, represent the Parakidograptus acuminatus Zone (Ross. pp. 719, 720) noted that these brachiopods could rep- 1962. p. 1383; Berry in Berry and Boucot, 1970. p. resent a latest Ordovician endemic North American 145). Therefore, we conclude that the range of 5. sub- fauna, with species derived from the Hirnantia com- regulare extends into the Silurian. Neuman (1982, p. munity and other North European Province species. 34) noted that several solitary rugosan species in Nor-

However, they suggested that it was most likely a Si- way range from the Ashgill into the Early Llandovery. lurian fauna with a few holdovers from the Late Or- It remains a possibility that lower Schweizer strata dovician North American Province. A Himantian age infilling the deepest channels in the eroded Maquoketa, was accepted by Jaanusson (1979, p. 154), based on a below the position of the graptolite bed, may be Ga- trilobite and "other indications" from beds in Illinois. machian in age, as suggested by Elias (1982a, p. 40, In view of the presence of Ordovician (possibly Hir- fig. 21) (Text-fig. 10). nantian) conodonts in the lower Keel Formation, Lee- The lower part of the Wilhelmi Formation has been mon Formation, Noix Limestone, and middle Cyrene correlated with the lower portion of the Mosalem For- Formation (Thompson and Satterfield, 1975; Mc- mation in northwestern Illinois and eastern Iowa on Cracken and Barnes, 1982; Barrick, 1986), the Hir- the basis of graptolites (Ross, 1964, p. 1107) and li- nantian aspect of the brachiopods and solitary corals, thology (Willman, 1973, pp. 13, 31, fig. 2). Graptolites and the position of these beds above Late Ordovician near the base of the Mosalem apparently represent the (Richmondian) strata, we accept a latest Ordovician same zone as those in the Wilhelmi, and are Early

(Gamachian) age, as suggested and discussed by Elias Llandovery in age (Ross, 1 964). Streptelasma subregu- (1982a, pp. 38, 39) (Text-fig. 10). If the Himantian is lare (Savage, 1913b) occurs at a higher stratigraphic 26 Bulletin 333

position in the formation. We suggest that lower Mosa- monense occur in the Leemon Formation (Gamach- lem strata infilling the deepest channels eroded into ian). However, the range of 5. subregulare is known to the Maquoketa. below the position of the graptolite extend into Early Llandovery strata of the Wilhelmi bed. may be Gamachian in age (Text-fig. 10). and Mosalem formations, in which the other species In northeastern Illinois, corals of the Silurian assem- are not represented. The Bryant Knob is tentatively blage appear at the base of the Elwood Formation and considered to be Early Llandovery on the basis of con- occur with the brachiopod Platymerella luauuicnsis odonts (Thompson and Satterfield, 1975) and grap- Foerste. 1909. in the upper Elwood. The Platymerella tolites (Berry, written commun., 1971, cited in Thomp- zone includes the upper Elwood and base of the over- son and Satterfield, 1975). However, this remains lying Kankakee Formation (Savage, 1913b. p. 30: Sav- questionable because some of the conodont collections age. 1917. p. 88; Willman, 1973. pp. 14, 15; Willman could be Ordovician (Nowlan in Bolton and Nowlan, and Atherton. 1975, p. 97). It was considered to be 1 979, pp. 5,21) and the graptolites were not identified Middle Llandovery in age by Berry and Boucot (1970, to the species level. The upper portion of the Cyrene

pi. 2). In northwestern Illinois, this solitary rugosan Formation immediately to the west is equated with the assemblage appears in the upper part of the Mosalem Bryant Knob (Text-fig. 10). The evidence for this cor- Formation, just above the stratigraphic position of lo- relation, based on conodonts, brachiopods, and lith- cal channels at Section 32 (Thomson East) that contain ologic similarity, was discussed on p. 15.

Slreplelasina sitbregulare (Savage, 1 9 1 3b) and Silurian The lower part of the Sexton Creek Limestone in fasciculate rugose corals identified as Pycnostylusl sp. southeastern Missouri and southern Illinois could be (see Hill. 1981. p. 140). We consider the upper Mosa- as old as the Bowling Green Dolomite (Early Llan- lem to be younger than the upper part of the Wilhelmi dovery). Both units contain conodonts representing the Formation because 5'. suhregitlare occurs in the Birds Paltodus dyscritus fauna (Thompson and Satterfield, Member of the Wilhelmi. whereas the Silurian assem- 1975, figs. 6, 7, 9, 11-15) and solitary corals of the blage is present in the upper Mosalem. The Edgcwood Silurian assemblage. The Silurian solitary coral assem- and Silurian solitan, rugosan assemblages are not known blage is also represented in basal beds of the Cochrane to co-occur. Although Willman (1973, pp. 15-17, 35, Formation in south-central Oklahoma (Text-fig. 10). 36) tentatively correlated the Elwood with the Blanding Conodonts in the lower Cochrane were thought to be Formation of northwestern Illinois on the basis of li- Llandovery (position uncertain) by Barrick (1986, pp. thology, he noted that the Tete des Morts Formation 57, 67). Amsden (1986, p. 6) considered the brachio- as well as the Blanding could correlate with the lower pod Triplesia alata Ulrich and Cooper, 1936, which Kankakee. From the coral evidence, we infer that the apparently ranges through most of the Cochrane (Ams- upper Mosalem must be equivalent to at least the lower den, 1971a, p. 145), to indicate an early Late Llan-

part of the Elwood (Text-fig. 10). Johnson. Rong. and dovery C,,2 3ge. However, he noted that it could be

Yang ( 1 985. fig. 5) placed the Mosalem. Tete des Morts, younger or older. and lower Blanding in the Early Llandovery (Rhud- The Edgewood solitary coral assemblage is latest Or- danian) on the basis of correlations involving sea-level dovician (Gamachian) to earliest Silurian (early Early curves. Llandovery; early Rhuddanian) in age, and therefore In northeastern Missouri, the Silurian coral assem- these Rugosa cannot be used to delineate the Ordo- blage occurs in the Bowling Green Dolomite at an vician-Silurian boundary in the east-central United eastern exposure. The Platymerella manniensis zone, States. In Illinois and Missouri, they occur in strata considered to be Middle Llandovery, is present at the that were included within the Alexandrian Series by base of the Sexton Creek Limestone, which overlies Savage (papers from 1908a through 1926, inclusive).

the Bowling Green (Savage, 1 9 1 3b. p. 30; Savage, 1917, Reeds (191 1) extended the use of that term for cor-

p. 88; Willman. 1973. p. 16; Willman and Atherton. relative beds in Oklahoma. This series was proposed

1975. p. 97). Therefore, we correlate the Bowling Green by Savage (1908a, pp. 433,434; 1908b, pp. 110, 111) with the lower Elwood and upper Mosalem and con- to include strata, thought to be earliest Silurian in age,

sider it to be Early Llandovery in age (Text-fig. 10). situated between the Richmondian Stage of the Cin- Corals of the Edgewood assemblage in the Bryant cinnatian Series (Ordovician) and the Niagaran Series

Knob Formation, which overlies the Noix Limestone (Silurian). It has been recommended that Alexandrian and underlies the Bowling Green Dolomite in north- be discontinued as a series term because of synonymies eastern Missouri, could be Gamachian or Early Llan- (Fisher. 1954, pp. 1982, 1984), and because outcrops dovery in age. Streptelasma subregulare (Savage, in the type area are meager, the units are not especially 1913b), Streptelasma leemonense Elias, 1982a, and fossiliferous, and unconformities are present within the

Grewingkia sp. A are also known from the Keel For- sequence (Amsden, 1974. p. 5).

mation (Gamachian), and S. subregulare and .S". lee- Ordovician-Silurian Rugose Corals: McAuley and Elias 27

linois. Units containing the Edgewood assemblage re- BIOGEOGRAPHY EVENTS AND cord a succession of oscillatory transgressions that Two biogeographic provinces are represented by sol- reached progressively farther north, according to Sav- itary rugose corals of the Late Ordovician "epiconti- age (1913a, p. 374; 1913b, pp. 34, 35; 1917, p. 92). nental" asseinblage in the upper Maquoketa Group. Amsden (1986, pp. 2, 45) considered the Keel-Edge- Salvadorea randi (Elias, 1981) in Illinois and Iowa is wood oolitic deposits to represent a regressive sedi- also known from middle Maysvillian strata in the Sel- mentary cycle reflecting eustatic lowering of sea level kirk Member (see Elias, 1 985, p. 45) and middle Rich- due to glaciation. Both interpretations may be in part mondian beds in the Fort Garry Member of the Red correct. The Edgewood assemblage is Gamachian to River Formation in southern Manitoba (Elias, Now- earliest Llandovery in age. The major glacio-eustatic lan, and Bolton, 1988, pi. 1, figs. 4-7). It belongs to sea-level drop during Gamachian/Hirnantian time was the Red River-Stony Mountain Solitary Rugose Coral followed by a rapid rise in the latest Gamachian/Hir-

Province (Elias, 1982a, p. 48; Text-fig. 1 1). The dis- nantian {e.g.. Brenchley and Newall, 1980, fig. 22; tribution of this species indicates dispersion across the Johnson, Cocks, and Copper, 1981, fig. 3; Petryk,

Transcontinental Arch between the Williston Basin and 1981b, fig. 1 ; Woodcock and Smallwood, 1987, p. 393). the area of Maquoketa deposition. Grewingkia cana- The Keel-Edgewood oolites in Oklahoma and Mis- densis (Billings, 1862), which is present in the upper souri likely mark the regressive phase, but could have Maquoketa Group of eastern Wisconsin, is character- been deposited during minor transgressions if sea level istic of the Richmond Solitary Rugose Coral Province fluctuated during that time interval (see Brenchley and

(Elias, 1982a, pp. 49, 50; Text-fig. 11). Elias (1982a, Newall, 1980, pp. 29, 30, fig. 22). A number of oscil- p. 29) suggested that this occurrence, in an apparent lations are evidently recorded in the latest Richmon- channel-fill deposit at the top of the Maquoketa shale dian to latest Gamachian regressive phase on Anticosti but beneath the Neda Formation, represents a west- Island (Petryk, 1981b, fig. 1). Channel-fill sediments ward shift in the geographic range of this species as- of the Wilhelmi and Mosalem formations in northern sociated with the regression during late Richmondian Illinois and eastern Iowa were likely deposited during time. the major latest Gamachian/Himantian-earliest Silu- Solitary Rugosa of the Red River-Stony Mountain rian transgression associated with deglaciation. and Richmond provinces in east-central North Amer- The Edgewood solitary rugosan species were not de- ica became extinct during the terminal Richmondian rived from corals of the Late Ordovician "epiconti- regression of the epicontinental sea caused by a major nental" assemblage in this region. Their resemblance glacio-eustatic sea-level drop (Elias, 1 982a, pp. 48,51). to some taxa previously restricted to the continental In northern Illinois and eastern Iowa, the presence of margin of North America suggests that they originated 30-m-deep channels eroded into the upper, Richmon- from such forms. Within the Edgewood Province, di- dian portion of the Maquoketa Group and subsequent- versity is highest in Oklahoma, intermediate in south- ly filled with Gamachian(?) and Early Llandovery de- em Illinois and Missouri, and lowest in northern Illi- posits of the Wilhelmi and Mosalem formations nois (western north-central Arkansas is excluded suggests a period of post-Richmondian emergence, at because only two identifiable specimens are known) least in the northern portion of the study region. To (Text-fig. 10). This apparent northward decrease in the east, the Cincinnati Arch region likely remained diversity corresponds to an environmental gradient emergent until late Early Llandovery time (Grahn and from relatively open conditions near the continental Bergstrom, 1985, pp. 178, 179). On Anticosti Island, margin to increasingly restricted conditions in the con-

Quebec, where deposition near the continental margin tinental interior. It is noteworthy that specimens of was essentially continuous from Richmondian time RhegmaphyUiim sp., but no representatives of the into the Silurian, the Richmondian-Gamachian Edgewood solitary coral assemblage, are present in the boundary (placed at the contact of the Vaureal and Cason oolite at the St. Clair Spring Section in eastern Ellis Bay formations) appears to coincide with a major north-central Arkansas. The associated conodonts and regression (Johnson, Cocks, and Copper, 1981, fig. 3; brachiopods comprise a typical Keel-Edgewood as-

Petryk, 198 lb, fig. 1 ; Long and Copper, 1987, pp. 1829, semblage (Craig, 1969, pp. 1624, 1625; Craig, 1975b, 1830). p. 77; Craig in Craig, Ethington. and Repetski. 1986, Solitary Rugosa of the Edgewood assemblage rep- p. 19; Amsden, 1986, pp. 20, 22; Barrick, 1986, p. 64). resent the Edgewood Solitary Rugose Coral Province Streptelasma leemonense Elias, 1982a, and Streptelas- (Elias, 1982a, pp. 51, 52; Text-fig. 11). The inclusion nia sp. cf. S. siibregulare (Savage, 1913b), both Edge- of south-central Oklahoma in this province is con- wood solitary Rugosa, occur in the Cason about 100 firmed herein, and the boundary is extended to include km to the west at Section 33 (Buffalo River). Thus, it western north-central Arkansas and northwestern Il- is possible to place the boundary of the Edgewood 28 Bulletin 333

Solitan. Rugose Coral Province and the area inhabited known in pre-Brassfield strata of North America, but by the Late Ordovician "continental margin" solitary some occur in the Baltic area, the Siberian platform, rugosan assemblage between these two sections (Text- and possibly Venezuela. Recent work indicates that fig. 11). Rlicgniapliylluni Wedekind, 1927, was confined to areas Genera recognized in the Silurian assemblage were near the North American continental margin in the not derived from Edgewood taxa. They must have orig- Richmondian and Gamachian (see Solitary Rugose inated elsewhere and been introduced to this region. Coral Assemblages, pp. 23, 24). During Early Llan- Laub (1975. p. 280; 1979, p. 45) noted that rugosan dovery time, the Silurian assemblage, including Di- species in the late Early to Late(?) Llandovery Brass- nophyltiiin sp., Dalnianophyllum sp., Cyathactisi sp., field Formation of the Cincinnati Arch region are not and Rhegtnaphyllum sp., succeeded the Edgewood as-

400 N -

600 W

RED RIVER-

, STONY MOUNTAIN ^PROVINCE

RICHMOND PROVINCE

EDGEWOOD PROVINCE

"CONTINENTAL MARGIN' ASSEMBLAGE

lOQo W SO" W

Text-figure 1 L — Biogcography of North American L^te Ordovician to earliest .Silurian solitary Rugosa. Red River-Stony Mountain Province of Edenian to Gamachian age (Elias. 1981, pp. 2. 8, 10; Elias, 1982a, pp. 48, 49; Elias, 1983a. pp. 927-931; Elias, 1985, pp. 16-20; Elias, unpubl. data). Richmond Province of Richmondian age (Elias, 1982a, pp. 49-51). Edgewood Province of Gamachian to early Early Llandovery

age (Elias, 1 982a. pp. 5 1 . 52; present study). Late Ordovician "continental margin" assemblage of Richmondian-Gamachian age (for discussion of taxa in eastern Quebec and northern Maine, see Elias, 1982a, pp. 48, 49; present study). Solid and dashed lines show established and uncertain boundaries, respectively. Ordovician-Silurian Rugose Corals: McAuley and Elias 29

semblagc. This occurred as water depth (and temper- involving constrictions and dilated tabulae at intervals ature) increased during the Early Llandovery transgres- of 3 to 13 mm in Late Ordovician (Richmondian-

sion related to deglaciation (see Johnson, Rong, and Gamachian) taxa from Anticosti Island, Quebec. It is

Yang, 1985, fig. 5, eastern Iowa). However, the ap- possible that these figures represent annual growth rates pearance of the Silurian solitary rugosan assemblage (see Risk, Pagani, and Elias, 1987, pp. 328, 329). Elias

above local channels containing Edgewood corals with- ( 1 984b, p. 536) reported an unusually high growth rate in the Mosalem Formation at Section 32 (Thomson for three coralla identified as Streptelasma sp. [referred East), and the unconformity between the Bryant Knob herein to S. amsdeni], based on the relatively wide Formation and Bowling Green Dolomite at some sec- spacing of fine growth ridges. Following an examina- tions in northeastern Missouri, suggest that Silurian tion of additional material during the present study, solitary Rugosa were introduced after a minor regres- we conclude that all growth increments may not be sive event. preserved on those specimens.

Abrasion THE EDGEWOOD SOLITARY RUGOSE CORALS During life, these solitary Rugosa produced septal grooves and interseptal ridges covered by a very thin Growth epitheca with fine growth ridges on the outer wall (Elias,

A small minority of solitary rugose corals in the 1982a, pi. 4, figs. 10, 11, 14, 15, 19; PI. 1, fig. 17, PI. Edgewood Province were attached throughout ontog- 4, figs. 4, 10, PI. 5, fig. 2, PI. 6, figs. 1, 10, 11, PI. 9, eny to surfaces such as bryozoans, colonial corals, and figs. 1, 2, PI. 11, fig. 6). Nonweathered, well-preserved possibly other solitary coralla. These epizoans belong specimens lacking these features are considered to have to Streptelasma sp. A (PI. 9, figs. 8, 9, PI. 10, figs. 1- been abraded prior to burial. The degree of abrasion

5), Grewingkia sp. A (PI. 10, fig. 8), Bodophyllum shorti was related to the duration and intensity of this process.

Elias, 1982a (Elias, 1982a. pi. 13, fig. 10), Kectophyt- The length of time a corallum was exposed on the lum oklahomense. n. gen., n. sp. (PI. 12, figs. 4-6), and substrate was determined by the sedimentation rate. possibly Streptelasma leemonense Elias, 1982a (PI. 7, The intensity of abrasion prior to burial of the speci- fig. 9). The vast majority of individuals, belonging to men was determined by the energy level of the envi- Streptelasma subregtdare (Savage, 1913b) and Strep- ronment. telasma amsdeni, n. sp., behaved as unattached objects The proportion of nonabraded and abraded Edge- on the substrate. A few specimens representing the wood coralla in various stratigraphic units is shown in latter two species have right-angle bends, indicating Table 2. All or the majority of specimens in the Keel that the polyp had the ability to redirect its growth axis Formation, Leemon Formation at Sections 3 1 (Thebes after being fully overturned (Elias, 1 984b, pp. 534, 535; North) and 19 (New Wells), and Wilhelmi Formation

PI. 1 , fig. 1 7, PI. 6, fig. 1 1 ). These are the earliest North are nonabraded. Lithologies of the laminated calcilu- American species presently known that could do so. tite unit of the Keel, the Leemon at Section 19, and The ability to survive such events, which apparently the Wilhelmi suggest deposition in comparatively low resulted in the death of polyps belonging to other taxa, energy conditions. However, the other Keel facies and

must have been advantageous. Although specimens of the Leemon at Section 3 1 were apparently deposited 5. leemonense lack right-angle bends, this species was in higher energy environments, and a higher propor- able to produce offsets that diverged from the parent tion of abraded coralla might be expected. A relatively at a high angle (PI. 8, figs. 1-4). They could have per- high sedimentation rate could have resulted in quick formed a function analogous to redirection of the growth burial of these individuals, thus protecting them from axis. abrasion. Prominent constrictions of the coral at apparently Most coralla in the Bryant Knob Formation, and in regularly spaced intervals are known only from one the Leemon Formation at Section 20 (Short Farm), are

specimen of Streptelasma amsdeni. n. sp. (PI. 6, fig. abraded. The lithologies of these units suggest that en-

11; identified as Streptelasma sp. in Elias, 1984b, p. ergy levels were relatively high, but probably not sig- 535). Seven consecutive constrictions are 6 to 7 mm nificantly higher than those in which facies of the Keel apart (average, 6.8 mm). Apparent periodicity involv- Formation other than the laminated calcilutite unit ing tabulae was observed only in one specimen of were deposited. The high proportions of abraded spec- Streptelasma suhregidare (Savage, 1913b) (PI. 3, figs. imens in these strata are likely a reflection of compar- 2-4). Four thick tabulae, separated from one another atively low sedimentation rates. The coral-rich interval by one to three thin tabulae, occur at intervals of 4 to of the Kissenger Limestone Member, Bryant Knob 6 mm (average, 5.2 mm). Elias (1984b, pp. 535, 536) Formation, contains the highest observed proportions documented comparable examples of periodic growth of abraded specimens. 30 Bulletin 333

Algal Coatings

Coatings having micritic, oncolitic, and Girvanella- like appearances in thin section were observed on Streptelasma sithregii/are (Savage. 1913b) from bioherms in the Leemon Formation at Section 19 (New Wells), the unnamed member of the Brvant Knob For- mation at Section 18 (Kissenger). and the coral-rich interval at the base of the Kissenger Limestone Mem- ber. Br>ant Knob Formation, at Sections 18 (PI. 2, fig.

6). 17 (ClarksviUe). and 16 (Clinton Spring) (PI. 3, figs. 14-18). Such coatings, presumed to be of algal origin, are rare except in the coral-rich interval of the Kissen- ger. where they are relatively common on solitary rugosan coralla and bioclastic grains. The coating usually completely surrounds the corallum, although in some

cases it is thicker on one side. Coatings were observed

Table 2. — Condition of corallum exterior, for specimens o( Slrep- tetasma subrcgulare (Savage. 1913b) unless otherwise noted, determined from an examination of the corallum and or transverse thin seclion(s). Nonabraded if growth ridges, epitheca. and. or septal grooves and interseptal ridges are present; abraded if those features are absent on nonweathered. well-preserved material.

unit Ordovician-Silukian RuGost Corals: McAuley and Elias 31

but occurs in solitary rugosan coralla from many strati- of the Kissenger Limestone Member, Bryant Knob graphic units and localities in the Red River-Stony Formation, at Section 16 (Clinton Spring). These dis- Mountain and Richmond provinces (Elias, 1986b, ta- tributions were interpreted by Elias, McAulcy, and

ble 1). Mattison (1987, p. 810), and the results are summa- Microborings about 5 ^m in diameter were observed rized below. in the outer wall of some specimens of Strcplclasma Coralla at Section 23 are considered to be randomly subregiilare {Savage. 1913b) from bioherms in the Lee- oriented (Text-fig. 1 2A). Although the energy level was mon Formation at Section 19 (New Wells) (PI. 2, fig. probably high enough to transport these objects, the

4), and possibly in one or two from the Leemon at directions of fluid motion may have been sufficiently Section 20 (Short Farm). These small borings could be variable that a preferred orientation pattern did not initial algal or fungal (sec Bromley, 1 970, pp. 54, 55; Golubic, result. It seems unlikely that an pattern was Perkins, and Lukas, 1975, p. 243). They occur beneath subsequently obscured by the activity of burrowers. epizoic bryozoans in two coralla and beneath an algal because there is minimal evidence for bioturbation. coating in one, indicating that the borers became as- Coralla at Section 16 are preferentially oriented, and sociated with these hosts relatively early. Similar bor- the distribution is bimodal (Text-fig. 128). Peaks in ings have been reported in Richmondian solitary ru- the northeast and southwest are opposite one another gosan coralla from the Richmond and Red River-Stony but skewed slightly toward the southeast. These indi- Mountain provinces (e.g.. Elias. 1982a, pi. 9, fig. 20; viduals were rolled almost perpendicular to water flow

Elias, 1982b, fig. 4h). or nearly parallel to wave crests, with the apical end A second type of microborings, with branches hav- facing either way but directed slightly into currents ing highly variable diameters of up to 50 ^m, was from the northwest. The current direction is parallel probably produced by algae (PI. 4, figs. 1, 2). Such to depositional strike of the Bryant Knob and the in- borings were observed in a few coralla of Streptelasma ferred shoreline, suggesting that coralla were oriented subregiilare (Savage, 1913b) from the Leemon For- by longshore currents and perhaps waves. mation at Section 20 (Short Farm), and from the Kis- From an examination of loose slabs, it is apparent senger Limestone Member of the Bryant Knob For- that cylindrical coralla of Streptelasma amsdeni, n. sp.,

mation at Sections 1 8 (Kissenger), 1 7 (Clarksville), and in the laminated calcilutite unit of the Keel Formation 16 (Clinton Spring). All but one of the Kissenger spec- at Section 24 (Coal Creek) are generally aligned parallel imens are from the basal coral-rich interval, and most to one another (PI. 6, figs. 9, 10). This is considered are from Section 16. The exterior surface of the cor- to be a result of hydraulic action. Unfortunately, too allum was micritized in almost all cases, and the bor- few specimens were found in situ to conduct a paleo- ings occur beneath algal coatings in some individuals current analysis. and within the calice in two. Such borings and associated micritization have not been observed in Rich- mondian solitary rugosan coralla.

Orientation

Virtually all of the solitary rugosan coralla found during this study were lying sideways within the strata, in what would have been stable depositional orientations after being overturned and possibly transported. Several clusters representing colonies and/or pseudocolonies of Streptelasma leemonense Elias, 1982a, include corallites oriented with calices facing upward, as

they would have during life. These may have been preserved in growth position. The greater size and weight of the clusters likely made them more stable than individual coralla. Such specimens were found at Text-figure 12— Rose diagrams showing directional orientations Sections 23 (Lawrence Quarry), 20 (Short Farm), and ofsolitary rugosan coralla (A' = sample size). Orientation convention 15 (Calumet). is illustrated using the north arrow and a typical specimen (to scale). 23-2 Data sets large enough to permit statistical analysis A. Mostly Streptelasma subregiilare (Savage. 1 9 1 3b), intervals (Brevilamnulella beds), 23-2a. 23-3, Keel Formation. Section 23 of directional orientations were obtained for solitary (Lawrence Quarry). B, Streptelasma subregulare. interval 16-1 (cor- rugosan coralla in the upper half of the Keel Formation, al-rich interval). Kissenger Limestone Member, Bryant Knob For- including the Brevilamnulella beds, at Section 23 (Law- mation, Section 16 (Clinton Spring); thick line represents deposi- rence Quarry), and the coral-rich interval at the base tional strike of Bryant Knob Formation. 32 Bulletin 333

Paleoecology northern Illinois (Text-figs. 7, 8), where deposition evidently occurred in the most restricted conditions, far- Solitary rugose corals of the Edgewood Province are thest from the continental margin. Evidence indicating absent or rare in units representing the highest energy that the distribution of solitary rugosan species in the environments. They are absent in the cross-bedded Richmond and Red River-Stony Mountain provinces oolite at the base of the Leemon Formation at Section was related to water depth and/or the degree of envi- 20 (Short Farm). These fossils are generally absent or ronmental restriction was presented by Elias (1982a, rare in relatively pure oolitic portions of the Keel For- pp. 13,26; 1983b. pp. 2, 3; 1985, pp. 14-16) and Elias, mation, such as below and above the laminated cal- Zeilstra, and Bayer (1988, p. 33). cilutite unit at Section 24 (Coal Creek), in which Strep- tetasina amsdeni, n. sp., is abundant. Strcptelasma sp. Intraspecific Variation and Evolution A, the only ta.\on known from the oolite comprising Streptelasma subregulare (Savage, 1 9 1 3b) is a highly the Noix Limestone, is rare at Section 1 5 (Calumet). variable species. The continuous spectrum of values This small, epizoic species may have been protected for measurements of numerous characteristics indi- by its position on a larger br>ozoan colony. Edgewood cates that there are no morphologic discontinuities solitary Rugosa are also absent or rare in argillaceous among the 589 specimens assigned to the species. Those units considered to represent the lowest energy envi- characteristics exhibiting anomalous trends at certain ronments. They are absent in the Leemon Formation sections or in particular stratigraphic intervals (Table above the basal bioherms at Section 19 (New Wells), 3) fall within or overlap the range of values for coralla in which Streptelasiua subregnlare (Savage, 1 9 1 3b) is from elsewhere. Such features could reflect genetic dif- abundant. These corals are absent or rare in Wilhelmi ferences among populations and/or environmental dif- and Mosalem strata, except near the base of the Wil- ferences that are not understood at present, given the helmi at a few localities and on one bedding surface limited amount of detailed paleontologic and sedi- in the Mosalem at a single locality. Streptelasma sub- mentologic work that has been done on these units. regulare is the only Edgewood species known from the Morphologic characteristics of coralla from the lam- Wilhelmi and Mosalem formations. inated calcilutite unit of the Keel Formation at Section Edgewood solitary rugosan species generally occur 24 (Coal Creek), and a specimen from the underlying in relatively pure bioclastic calcarenite beds, such as Keel oolite, generally lie within the range of variability those in the Keel Formation at Sections 21 (Rock oi Streptelasma subregulare (Savage, 1 9 1 3b), but most Crossing) and 23 (Lawrence Quarry), the upper Lee- are not typical of that species (Table 3). The most mon Formation at Sections 31 (Thebes North) and 20 striking features are the long, cylindrical growth form (Short Farm), and the Bryant Knob Formation. This and thin septa. We consider these coralla to represent suggests that they favored clear water, moderate en- a distinct taxon, Streptelasma amsdeni. n. sp., because ergy, normal marine conditions. Streptelasma subregu- of the consistent differences. It is inferred that S. ams- lare (Savage, 1913b), by far the most common and deni was derived from S. subregulare by geographic widely distributed species (see Text-figs. 2-5, 7, 8), was speciation. This is the only evolutionary event recog- evidently able to inhabit a wider range of environments nized within the Edgewood Province. than the other taxa. Streptelasma leemonense Elias, 1982a, and Grewingkia sp. A are the second and third most widely distributed species, respectively. SYSTEMATIC PALEONTOLOGY Deposition of the Kissenger Limestone Member at Introduction Sections 18 (Kissenger), 17 (Clarksville). and 16 (Clin- ton Spring) occurred nearer to shore and possibly in Our morphologic terminology follows Hill (1981) shallower water than at Sections 15 (Calumet) and 14 and Elias (1981, p. 3). Most of the biometricand other

(Higginbotham Farm) (Text-fig. 5). This is inferred data used to prepare Text-figures 13-23 and Tables 4, from the southeast-northwest depositional strike of the 6, and 7 were presented by McAuley( 1985, appendixes Bryant Knob Formation, and the apparent position of 1-4). The synonymies include only forms considered a shoreline immediately to the northeast. Streptelasma identical to the one under discussion. subregulare (Savage, 1913b) is the only solitary coral The suprageneric classification followed herein is that at Sections 18, 17, and 16, but it occurs together with of Hill (1981) for Streptelasmatina Wedekind, 1927, Streptelasma leemonense Elias, 1982a, at Sections 15 and Cyathophyllina Nicholson in Nicholson and Ly- and 14, and also with Grewingkia sp. A at Section 14. dekker, 1889, and Neuman (1984) for Monacanthina

Perhaps the distribution of Edgewood taxa was deter- Neuman, 1 984. Generic treatments are included where mined by proximity to shore and/or water depth. our study increases understanding of an established

Streptelasma subregulare is the only species present in genus, or requires erection of a new one. Ordovician-Silurian Rugose Corals: McAuley and Elias 33

Tabic 3. — Morphologic characteristics o( Streptelasma suhregutare (Savage, 1913b) and the closely related species Slreptelasma amsdem. n. sp.. for sections with relatively large sample sizes, based on an inspection of corallum lengths and data in Tables 4-6 and Text-figure 17; unusually high frequency (H), typical frequency (T), unusually low frequency (L), insufficient data( — , fewer than 10 data points for comparison, except for "closely spaced tabulae," where all points were used). .

34 Bulletin 333

Streptelasnia corniculum Hall, 1847; lower Trenton considered independently. We therefore broaden the Limestone (upper Middle Ordovician), Middlevillc. diagnosis of Streptelasma to include all representatives New York. of 5'. suhregulare. Diagnosis. —SoMldiTy or with few offsets. Septa non- Neuman (1986, p. 352) stated that the only fossular dilated to completely dilated in early stage, dilation structures characteristic of Streptelasma Hall, 1847. usually decreases during ontogeny. Major septa straight are a pseudofossula (lacking tabular depression) or a or wavy, generally extend to axis in early stage and septofossula (shortened cardinal septum). The cardinal become shorter during intermediate to late stages. Ax- fossula in Streptelasma suhregulare (Savage, 191 3b) is ial structure, if present, typically simple, composed of highly variable, and the tabulae are markedly de- septal lobes and rareh lamellae in intermediate and/ pressed in some specimens (including the lectotype; or late stages. Cardinal septum and fossula inconspic- Elias, 1982a, pi. 4, fig. 7).

uous to prominent. Streptelasma suhregulare (Savage, 1 9 1 3b)

Discussion.— Neumans (1969. pp. 8-11) study of Plate 1, figures 1-19; Plate 2, figures 1-12;

the lectotype oi Streptelasnia corniculum Hall, 1847, Plate 3, figures 1-18; Plate 4, figures 1-13;

formed a basis for the generally accepted concept of Plate 5, figures 1-10 Streptelasnia Hall. 1847. This genus was considered Zaphrentis subregularis Savage. 1913b, p. 62. pi. .3. fig. 5. pi. 7. fig. to include streptelasmatids with major septa that are 1 ; Savage, 1 9 1 7. p. 1 1 3, pi. 5, fig. 5. pi. 9, fig. 1 long, thin to moderately thick, and usually joined to /.aphrcnlis anibigua Savage, 1913b, pp. 109, 1 10. pi. 7, fig. 2; Savage, form a simple axial structure during early to inter- 1917, p. 149. pi. 9, fig. 2. mediate stages. These septa become shorter and thin- Streptelasma sp. Elias, 1982a, pp. 56, 57, pi. 4, figs. 4—6. Streptelasma suhregulare (Sa\a%,e. 1913b). Elias. 1982a, pp. 57, 58, ner in late stages, when an axial structure is seldom pi. 4. figs. 7-22. present. However, because intraspecific variability of

the type species is unknown, Streptelasnia remains Holotype.— By original designation: Ul X-85 1 (Sav-

poorly understood. Furthermore, most species pres- age, 1 9 1 3b, pi. 3, fig. 5; Savage, 1 9 1 7, pi. 5, fig. 5; Elias,

ently included in the genus are based on small collec- 1 982a, pi. 4, figs. 7, 8), S coll., Cyrene Formation, near tions. Edgewood, Pike County, Missouri. McLean (1974. pp. 38-41) stated that Streptelasnia .ideational material. -VSNM 422831, 422832. in- Hall, 1847, Dinophylluni Lindstrom, 1882, and Por- terval 21-1, EMM coll., USNM 422833-422836, in- Jirieviella Ivanovskiy, 1963, may prove to be syno- terval 21- la, EM coll., USNM 422837-422842, inter- nymous. He also noted that many species resembling val 21-lb, EM coll., USNM 422843-422852, interval Streptelasnia in late stages are not well enough known 2I-lc, EM coll.. Ideal Quarry Member, Keel Forma- in earlier stages to be included in the genus with cer- tion, Section 21 (Rock Crossing), Carter County, Okla- tainty. Elias (1982a, p. 52) indicated that further study homa; USNM 422853-422856, interval 25-1, EMM may demonstrate the synonymy of Streptelasnia, He- coll.. Keel Formation, Section 25 (Hunton), Coal licelasma Neuman. 1969, Borelasnia Neuman, 1969, County, Oklahoma; USNM 422857, interval 23-1, and Grewingkia Dybowski, 1873. He showed that in EMM coll., USNM 422858-422909, interval 23-2 Streptelasnia divaricans (Nicholson, 1875) there is (Brevilamnulella beds), EMM coll., USNM 422910- complete gradation from coralla with open axial re- 422912, interval 23-2a, EM coll., USNM 422913, gions to those with axial structures similar to Gre- 422914, interval 23-3, EMM coll., USNM 422915- wingkia (Elias, 1982a, pp. 52, 55, 56, pi. 1, figs. 1-19). 422932, interval 23-3, EM coll., USNM 422933-

Neuman (1986, p. 352) considered the North Ameri- 422935, interval 23a- 1, EM coll.. Keel Formation, Sec- can fauna to show an extreme range of variation not tion 23 (Lawrence Quarry), Pontotoc County, Okla- representative of most other areas, including Balto- homa; UI X-6683, X-6684, S coll. [labelled "Edge- scandia. wood", "near Thebes"], USNM 422936-422952,

Streptelasma suhregulare (.Savage, 1 9 1 3b), described interval 31-1, EMZ coll., USNM 422953-422965, in- in this study on the basis of a large collection, is im- terval 31-la, EMZ coll., USNM 422966, interval 31- portant in establishing the range of variability in Strep- Ib, EMZ coll., Leemon Formation, Section 31 (Thebes

telasma Hall, 1 847. In this highly variable species there North), Alexander County, Illinois; USNM 365919, is continuous gradation from coralla that closely re- 422967-422978, interval 20-1, EMM coll., USNM semble Streptelasma corniculum Hall, 1847, to those 422979-422981, interval 20-1, EM coll.. USNM that arc similar to Helicelasma Neuman, 1969, Bor- 422982, 422983, interval 20-2, EMM coll., USNM elasma Neuman, 1969. and Ullernelasma Neuman, 422984^22992, interval 20-3, EM coll., USNM 1975. Within some individuals, different ontogenetic 422993, 422994, interval 20-4, EM coll., USNM stages would be assigned to different genera if they were 422995-423004, interval 20-5, EM coll., UCGM 3

Ordovician-Silhrian RuciosE Corals: McAuley and Elias 35

45616, same interval as 20-3, 20-4, 20-5, El coll., X-947 [type specimens of Zaphrenfis ambigua, one Leemon Formation, Section 20 (Short Farm), Cape specimen and a slab with five specimens, one figured Girardeau County, Missouri; UCGM 45618-45634, by Savage, 1913b, pi. 7, fig. 2, and Savage, 1917, pi. 9- E 1 coll., USNM 3659 1 8, 423005-4230 1 8, interval 1 9, fig. 2], S coll., Wilhelmi Formation [labelled "Edge-

1, EMM coll., USNM 423019-423041, interval 19-2, wood"], near C^hannahon, Will County, Illinois; UI EMM coll., USNM 423042-423083, interval 19-3, X-926 [two specimens labelled "Zaphrentis suhregu- EMM coll., Leemon Formation, Section 19 (New taris", one figured by Savage, 1913b, pi. 7, fig. 1, and

Wells), Cape Girardeau County, Missouri; USNM Savage, 1917, pi. 9, fig. 1], S coll., Wilhelmi Formation 423084-423103, interval 18-1, EMM coll., USNM [labelled "Edgewood", "Channahon"], Will County. 423104-423108, interval 18-1, EM coll., unnamed Illinois; USNM 423286^23291, interval 4-1. EMM member, Bryant Knob Formation, Section 18 (Kis- coll., Schweizer Member, Wilhelmi Formation, Sec- senger). Pike County, Missouri; USNM 423109- tion 4 (Schweizer West), Will County, Illinois; USNM 423126, interval 18-2, EMM coll., USNM 423127- 423292, interval 29-1, EMZ coll., Wilhelmi Forma- 423137, interval 18-3, EMM coll., USNM 423138- tion, Section 29 (Sears Pit), De Kalb County, Illinois; 423145, interval 18-3, EM coll., USNM 423146, in- USNM 423293-423296, interval 3-2, EMM coll., terval 18-4, EM coll., Kissenger Limestone Member, USNM 423297-423303, interval 3-3, EM coll.. Birds Bryant Knob Formation, Section 18 (Kissenger), Pike Member, Wilhelmi Formation, Section 3 (Garden County, Missouri; USNM 423147-423183, interval Prairie), McHenry County, Illinois; UI C-1619 [six 17-0, EM coll., Kissenger Limestone Member, Bryant specimens labelled "Zapfircnlis subregularis'']. S coll.. Knob Formation, Section 17 (Clarksville), Pike Coun- Birds Member, Wilhelmi Formation [labelled "Chan- ty, Missouri; UCGM 45643, USNM 423184, interval nahon"], near Belvidere, Boone County, Illinois; 16-0. El coll., unnamed member, Bryant Knob For- USNM 431 136^31 166, interval 34-1, E2 coll.. Birds

mation, Section 1 6 (Clinton Spring), Pike County, Mis- Member, Wilhelmi Formation, Section 34 (Belvidere

souri; UCGM 45644, 45645, USNM 423 1 85-423 1 87, South), Boone County, Illinois; USNM 423304, inter- interval 16-1, El coll., USNM 423188-423234, interval 32-Oa, EZ coll., USNM 431 167-431 173, interval val 16-1, EMM coll., Kissenger Limestone Member, 32-lz, E2 coll., USNM 423305, 423306, interval 32-la, Bryant Knob Formation, Section 16 (Clinton Spring), EZ coll., USNM 431 174-431 177, interval 32- lb, E2 Pike County, Missouri; USNM 423235^23241, in- coll., Mosalem Formation, Section 32 (Thomson East), terval 15-1, EMM coll., USNM 423242-423252, in- Carroll County, Illinois. terval 15-1, EM coll., Kissenger Limestone Member, Occurrences. —VppermosX Ordovician (Gamach- Bryant Knob Formation, Section 15 (Calumet), Pike ian): Keel Formation including Ideal Quarry Member, County, Missouri; USNM 423253-423280, interval south-central Oklahoma; Leemon Formation, south- 14-1, EM coll., Kissenger Limestone Member, Bryant eastern Missouri and southern Illinois; middle Cyrene Knob Formation, Section 14 (Higginbotham Farm), Formation, northeastern Missouri. Uppermost Or-

Pike County, Missouri; USNM 423281-423285, in- dovician (?) (Gamachian(?)) to lowermost Silurian terval 13-1, EMM coll., Cyrene Formation, Section 1 (lower Lower Llandovery): Schweizer Member. Wil- (Bowling Green), Pike County, Missouri; UI C-864 helmi Formation, northeastern Illinois. Lowermost Si-

[labelled "Zaphrentis^'], S coll., Cyrene Formation [la- lurian (?) (lower Lower Llandovery (?)): Bryant Knob belled "Edgewood"], Edgewood, Pike County, Mis- Formation including unnamed member and Kissenger souri; UI C-2258 [labelled "Zaphrentis cf. subregidar- Limestone Member, northeastern Missouri. Lower- m"], S coll., Wilhelmi Formation [labelled "Essex"], most Silurian (lower Lower Llandovery): Birds Mem- Horse Creek, about 2.4 km east of Essex, Kankakee ber, Wilhelmi Formation, northeastern Illinois; mid- County, Illinois; UI C-1581 [five specimens labelled dle Mosalem Formation, northwestern Illinois. "Zaphrentis siibregidaris''], S coll., Wilhelmi Forma- Diagnosis. —SohXary, usually ceratoid. In early stages, tion [labelled "Channahon"], southeast of Channahon, major septa generally moderately to greatly dilated and Will County, Illinois; UI C-1560 [seven specimens la- extend to axis, where distal ends join. During inter-

belled "Zaphrentis channahonensis"], UI C- 1 563 [one mediate to late stages, septal length and dilation de- specimen, a slab with one specimen, and a slab with crease, axial region opens. Cardinal septum commonly three specimens, labelled "Zaphrentis ambigiia"], S conspicuous in late stages. Cardinal fossula usually in- coll., Wilhelmi Formation [labelled "Edgewood" and conspicuous, less commonly very broad or distinc- "Channahon", respectively], Channahon, Will Coun- tively shaped. Minor septa typically extend a short ty, Illinois; UI C-1547 [slab with two specimens la- distance beyond relatively narrow stereozone. Tabulae belled "Zaphrentis channahonensis''], UI C-1561 [10 generally moderately to widely spaced, commonly de- specimens labelled "'Zaphrentis subregnlaris"']. UI pressed in cardinal fossula. 36 Bulletin 333

Description ofcorolla.— The largest specimen is 102 length, but varies from 30 percent to perhaps as much mm long and 44 mm in diameter at the calice rim as 90 percent in several individuals that have unusually (USNM 423146). Growth form is trochoid (PI. 4, fig. short major septa throughout ontogeny (USNM 10) to ceratoid (PI. 5. fig. 2) to rarely subcylindrical. 423006, 423009, 423025. 423034, 423075). and coralla vary from straight to moderately curved Ontogeny and Internal structures. —The relationship

(PI. 4. fig. 4) to gradually curved through 90 degrees between number of septa and corallum diameter is (Table 4). Among curved coralla. the cardinal side is shown in Text-figure 13 and Table 5. Major septa gen- typically convex, but there are irregular exceptions (PI. erally extend to or near the axis, where their distal ends

4, fig. 4). Several coralla have slight to moderate bends meet in small groups, during early ontogenetic stages in two different directions. A few individuals have sin- (PI. 1, figs. 1, 13, PI. 2, fig. 10, PI. 3, figs. 7, 10, 11, gle right-angle bends (PI. 1, fig. 17), but none have 16, PI. 4, fig. 5, PI. 5, figs. 3, 7, 9). Septa are shorter more than one such bend. Corallum shape in trans- in some specimens, but only rarely extend less than verse section is generally circular, but is irregular in a half the corallum radius. The septa usually decrease in few cases (PI. 2, fig. 6). Well-preserved specimens show length gradually during intermediate stages (PI. 1, figs. prominent septal grooves and interseptal ridges, as well 2, 4, 6-11, 14, 15. 18, PI. 2, figs. 1, 5, 11. PI. 3, figs. as growth lines. Coarse rugae are present on some in- 8,9, 12, 17, PI. 4, figs. 6, 8, II , 1 2, PI. 5, figs. 4, 5, 8) dividuals. Rejuvenations, if present on a corallum. are and late stages (PI. 1, figs. 3, 5, 12, 16, 19, PI. 2, figs. few in number and not pronounced. On the convex 2, 3, 6, 12, PI. 3, figs. 13. 18, PI. 4, figs. 3, 7, 9, 13, PI. cardinal side at the apex, two specimens have small 5, figs. 6, 10) (Text-fig. 14, Table 5). However, they grooves (USNM 422910. 422935) and one has a small remain long in some coralla, and rapidly decrease in expansion with a flat surface (USNM 422941). These length in others. Septa are relatively straight to wavy are interpreted as attachment structures. Depth of the in transverse sections. A few septal lobes are present calice is commonly about 50 percent of the corallum in some individuals (PI. 1, fig. 15, PI. 2, fig. 12), but

Table 4. — Growth form and cur^aVuTe of specimens of Slreplelasma subregulare {Savage, 1913b). Streplelasma amsdem, n. sp., Slreptelasma leemonense Elias, 1982a (and two specimens of Streplelasma sp. cf. S. leemonen.se Elias, 1982a. from Section 23), and Keelophyllum oklahomense. n. gen., n. sp. Ordovician-Silurian Rugose Corals: McAuley and Elias 37

paliform septal lamellae are rare (PI. 1, tig. 10). termediate stages of a few individuals, the cardinal and The degree of septal dilation is typieally moderate counter septa are longer than other major septa (PI. 4,

to great in early stages and decreases during ontogeny, fig. 12). The cardinal fossula is usually inconspicuous,

but the range among specimens is from nondilated to having the same width and shape as other pairs of

completely dilated in all stages. The actual thickness inlerseptal spaces. However, it becomes very broad in

of septa generally increases in early to intermediate some coralla (Text-fig. 16, Table 5). Five basic inter-

stages, and then decreases (Text-fig. 1 5, Table 5). How- gradational shapes are recognized in transverse sec- ever, in some coralla the septa decrease in thickness tions, as follows: (!) width decreases from periphery throughout ontogeny, and in others their thickness re- toward corallum axis; (2) width constant; (3) width mains about the same. increases toward axis; (4) biconvex with maximum The cardinal septum is most commonly inconspic- width midway between periphery and axial end; and uous, being the same length and thickness as other (5) hourglass-shaped with constriction midway be-

major septa (Table 6). However, this septum is distinct tween periphery and axial end (Table 7). Shapes (3) to

if it is relatively short or long, and/or thin or thick. Its (5) are especially distinctive in many cases. prominence varies among coralla, and from stage to Minor septa extend a short distance beyond the ste- stage within some individuals. In many specimens, the reozone in ontogenetic stages where major septa are cardinal septum becomes relatively short and thin in nondilated to slightly dilated. In a few individuals, the late stages near the base of the calice. In early to in- minor septa immediately adjacent to the counter sep-

Q. LU CO cc o 30

cc 11J20 00

Sections 21 and 19: 112 transverse sections from 57 coralla 10 Sections 31 and 20: 64 transverse sections from 42 coralla

All other sections: 295 transverse sections from 190 coralla

10 15 20 25 30 DIAMETER (mm) Text-figure 13. — Relationship between number of major septa and corallum diameter m Streptelastna subregiitare (Savage. 1913b). Data for "All other sections" are from Sections 25, 23, 13-18, 4. 3, 34. and 32. Numbers beside data points mdicate frequencies greater than one. Arbitrary line was used to derive proportions shown in part of Table 5. 38 Bulletin 333

Table 5. — Frequency of data points above (A), or on and below (B), arbitrary lines drawn in Text-figures 13- 16 and 18-21, for characteristics of major septa and cardinal fossula in Strcpuiusina suhregulure (Savage, 1913b) and Sireplelasina amsdem. n. sp. ORDOViriAN-SlLURIAN RuCiOSE CORALS: McAuLEY AND ElIAS 39

o.s

Section 18 (Intervals 3 and 4): 35 transverse sections from 14

DIAMETER (mm) Text-figure 14. — Relationship between length of major septa and corallum diameter in Sireplelasma suhregulare (Savage, 1913b), for specimens yielding more than one transverse thin section. The length of a typical septum was measured and divided by the corallum radius, yielding a ratio less than or equal to 1 .0. Data for "All other sections" are from Sections 21, 23, 31, 20, 19, 18 (intervals I and

2), 13-17, 4, 3, 34, and 32. Arbitrary line (dotted) was used to derive proportions shown in part of Table 5.

Text-figure 15. — Relationship between thickness of major septa and corallum diameter in Sireplelasma suhregulare (Savage, 1 9 1 3b), for specimens yielding more than one transverse thin section. Septal thickness was measured in transverse thin sections halfway between the axial and peripheral ends of a typical septum on the counter side (usually the counter septum). Data for "All other sections" are from

Sections 21, 23, 15-17, 13, 4, 3, and 34. Arbitrary line (dotted) was used to derive proportions shown in part of Table 5. 40 Bulletin 333

Table 6. — Length and thickness of cardinal septum, compared with other typical major septa, in transverse thin sections oi Streptelasma subregiilare (Savage, 1913b) and Streplelasma ainsdcni. n. sp. Ordovician-Sii.urian Rugose Corals: McAuley and Elias 41

age, 1913b) wilh moderately dilated septa closely re- from the Vaurcal Formation (Richmondian) and Ellis semble the lectotypc of StrcpWlasma coniiciiliii)] Hall, Bay Formation (Gamachian) on Anticosti Island, Que- 1847, from the Trenton Limestone (upper Middle Or- bec (Bolton, 1981, pi. 3, figs. 3-8; Elias, 1982a. pp. 59, dovician) of New York (Neuman, 1969, pp. 10, 11, 60, pi. 5, figs. 4-\8); Streplc'/asnia primum (V^edckind, figs. 5, 6). The number of septa, width of the cardinal 1927) in Stage 5a (Ashgill) of Norway, the Boda Lime- fossula, and spacing of tabulae in the latter corallum stone (Ashgill; Hirnantian) of Sweden, and the Pirgu are about average for .S'. sitbregulare. However, the Stage (Ashgill) of the Estonian S.S.R. (Neuman, 1969, major septa are slightly longer than usual, and the de- pp. 11-17, figs. 7a-c, e-h, 8-10; sec also Neuman, gree of septal dilation is greater on the cardinal side 1975, pp. 357, 358); Streptelasma cf. primum (Wcdc- than on the counter side. Further comparison is not kind, 1927) from boulders (Upper Ordovician; sub- possible at this time because the range of variability Hirnantian, possibly Pirguan) in Sweden (Neuman. in S. corniculum is unknown. 1986, pp. 353, 355, 358, figs. 5-8); and Streptelasma Some representatives of Streptelasma subregiilare unicum Neuman, 1975, from the Dahnanitina Beds (Savage, 1913b) with thin, wavy septa are similar to (Ashgill; Hirnantian) or possibly the lowermost Llan- the following taxa: Streptelasma a^fiwe (Billings, 1865) dovery of Sweden (Neuman, 1975, pp. 353, 356-358,

Sections 19 and 18:

136 transverse sections from 70 coralla

Oj o 42 Bulletin 333

figs. 15. 16). However, in S. affine and S. primum the cardinal septum is always indistinct, and a cardinal

fossula is never de\eIoped. In S. iiniciini, the cardinal septum becomes short and the fossula is conspicuous in late stages, but early ontogenetic stages and intraspecific variability arc unknown. Minor septa are longer in S. affine than in the other three species. A few individuals of Strcplelasma subregiilare (Sav- age. 1913b) resemble Hclicelasma simplex Neuman, 1969. from the Dalnuuutinu Beds(Ashgill; Hirnantian) or possibly the lowermost Llandovery of Sweden (Neu- man, 1969. pp. 29-33. figs. 23-26; Neuman, 1975, pp. 335, 336). In H. simplex, major septa are greatly to completely dilated in early stages, and gradually become thinner during ontogeny. A simple axial structure

of fused septal tips is formed during the intermediate and late stages. The cardinal septum and fossula are inconspicuous in H. simplex, but are most commonly conspicuous in comparable coralla belonging to S. siih- regiilare. Like some specimens of Slreptelasma suhregulare (Savage, 1913b), Burelasma crassitangens Neuman,

1 969, from the Dalmanitina Beds (Ashgill; Hirnantian) or possibly the lowermost Llandovery of Sweden (Neu- man, 1975, pp. 335, 336) has thick major septa that are greatly to completely dilated in early stages and decrease in length during ontogeny (Neuman, 1969, pp. 66-69, figs. 57-59). A diagnostic characteristic of

this taxon is the long cardinal and counter septa in

I 1

ORDOVICIAN-SiLI IRIAN RtJOOSE CORALS! McAULEY AND ElIAS 43

open axial region possibly with several septal lobes. Diagnosis. —Solitary, slender ceratoid to cylindrical. The cardinal septum appears to be shorter than the Major septa thin, nondilated to slightly dilated and other major septa. extend to axis in early stages, gradually withdraw from

/)/.V(//.v.v/«/7. — The septal arrangement of this speci- axis during ontogeny. Cardinal septum indistinct to men appears to lie within the range of variability doc- relatively long and conspicuous. Cardinal fossula usu- umented herein for Streptclasnia suhregulare (Savage, ally inconspicuous, less commonly distinctively shaped.

1 9 1 3b). However, because it is incomplete, poorly pre- Minor septa typically extend a short distance beyond served, and the only corallum of this kind known from very narrow stereozone. Tabulae widely spaced. north-central Arkansas, it cannot be positively iden- Description ofcoralla.— The greatest observed length tified. We therefore refer to it as Slreptelasnia sp. cf and diameter are 1 55 mm (USNM 423319. incomplete

S. suhregulare (Savage, 1 9 1 3b). at both ends; PI. 6, fig. 10) and 23 mm (USNM 423377, incomplete calice), respectively. In early ontogenetic Streptelasma amsdeni, new species stages, the majority of coralla are slenderly ceratoid in Plate 5, figures 13-22; Plate 6, figures 1-1 form, with moderate or slight curvature. The cardinal

Derivation of name.— The species name honors side is not always convex (PI. 6, fig. 1). The typical Thomas W. Amsden of the Oklahoma Geological Sur- vey, collected some of the specimens described who 1.0 herein. Holotype. -VSNM 423308, interval 24-2, EMM coll.

Pararypes. -VSNM 423309, interval 24-1, EMM CO coll., USNM 365920, 423310-423312, interval 24-2, - 0.9 A coll., USNM 423313^23317, interval 24-2, EMM < coll. cr Additional material. -\JS^U 423318-423320 [three specimens on slab], 423321-423329, interval 24-2, A => 0.8 _l coll., USNM 423330-423377, interval 24-2, EMM coll. _l Occurrence. ~\J}px>trmo%\ Ordovician (Gamachian): < a. lower oolitic and middle laminated calcilutite units O (intervals 24-1 and 24-2, respectively) of the Keel For- O 0.7 mation, Section 24 (Coal Creek), Pontotoc County, •I- south-central Oklahoma.

Q. ^ 0.6

^30 0.5

O 120 I I- 0.4

•^ 10 m 0-3i-53 transverse sections from 26 coralla

54 transverse sections from 26 coralla z 5 10 15 20 DIAMETER (mm) 5 10 15 20 Text-figure 19. — Relationship between length of major septa and (mm) DIAMETER corallum diameter in Streptelasma amsdeni. n. sp. The length of a Text-figure 18. — Relationship between number of major septa and typical septum was measured and divided by the corallum radius, corallum diameter in Streptelasma amsdeni. n. sp. Numbers beside yielding a ratio less than or equal to 1 .0. Lines join data points from data pomts indicate frequencies greater than one. Arbitrary line [in individual specimens. Numbers beside data points indicate fre- same position as that for Streptelasma suhregulare (Savage. 1913b) quencies greater than one. Arbitrary line [dotted, in same position in Text-fig. 1 was 3] used to derive proportions shown in part of as that for Streptelasma suhregulare (Savage, 1 9 1 3b) in Text-fig. 1 4] Table 5. was used to derive proportions shown in part of Table 5. 44 Bulletin 333

adult form is long and cylindrical, but some remain cardinal fossula is about the same width as other pairs slenderly ceratoid (Table 4). Specimens are generally of interseptal chambers in most specimens, but is relatively straight, but have slight to moderate bends somewhat wider in intermediate and late stages of a as well as several constrictions and rejuvenations (PI. few (Text-fig. 2 1 ). Shapes of the fossula are as described

6. fig. 10). A few have right-angle bends. Periodicity for Streptelasma subregulare (Savage, 1913b) (Table of growth has been observed only in the straight por- 7). Minor septa generally project a short distance be- tion of one individual, where six successive constric- yond the very narrow stereozone. tions are spaced 6 to 7 mm apart (average, 6.8 mm; Throughout ontogeny, tabulae are usually complete,

PI. 6, fig. 1 1). Septal grooves and interseptal ridges, as very thin, and relatively widely spaced (PI. 5, fig. 13, well as growth lines, are preserved on all specimens. PI. 6, figs. 2-4; Text-fig. 1 7). They are most commonly Attachment structures are not present. Depth of the convex upward in the septal region, but some are flat. calice is estimated to be about 20 percent of the cor- In the axial region, they are flat to concave upward. allum length in small individuals, and is probably less Microstructure.— The microstructure in transverse than 10 percent in adults. and longitudinal thin sections is the same as described Ontogeny and internal structures. —The relationship for specimens of Streptelasma subregulare (Savage, between number of septa and corallum diameter is 1913b) having nondilated to slightly dilated septa. shown in Text-figure 18. In early ontogenetic stages Discussion. —There is relatively little variation among

(PI. 5, figs. 17-20. PI. 6. fig. 5), major septa extend to the 71 coralla described above. Morphologic charac- or almost to the axis, where they meet. The septa with- teristics generally lie within the range of variability in

draw from the axis, leaving an open axial region, during Streptelasma subregulare (Savage, 1 9 1 3b), but are not intermediate stages (PI. 5, figs. 14-16, 21, PI. 6, figs. typical of that species (Table 3). The most striking

6, 7). They shorten to half the corallum radius or less features are the long, cylindrical growth form and thin

in late stages (PI. 5, fig. 22, PI. 6, fig. 8; Text-fig. 19). septa. We consider these coralla to represent a distinct Major septa are generally straight to slightly curved in taxon, Streptelasma atusdeni. n. sp., because of these early stages, and become wavy by late stages in many consistent differences. In previous paleobiologic stud- individuals. They are thin throughout ontogeny (Text- ies, this species was referred to as Streptelasma sp.

fig. 20: PI. 6. fig. 9), but in some cases are slightly dilated (Elias, 1984a, tables 1.3-5; Elias, 1984b, pp. 535, 536). in early stages. Streptelasma ainsdeni. n. sp., resembles Streptelas- Compared with other major septa, the cardinal sep- ma primum (Wedekind, 1927), Streptelasma cf pri-

tum is the same length or longer, and almost always /?;;/;>; (Wedekind, 1927) of Neuman, \9^6, znd Strep- the same thickness, during all stages (Table 6). The telasma unicum Neuman, 1975, which were discussed

E 3 E wO.3 COw LU 02 i 0.2 O I

0.1-

O 52 transverse sections from 26 coralla I I- 5 10 15 20 9 ^ DIAMETER (mm) 5 5 10 15 Text-figure 20. — Relationship between thickness of major septa DIAMETER (mm) and corallum diameter in Streptelasma amsdeni, n. sp. Septal thick- Text-figure 21. — Relationship between width of cardinal fossula ness was measured in transverse thin sections halfway between the and corallum diameter in Streptelasma amsdeni. n. sp. Width of axial and peripheral ends of a typical septum on the counter side cardinal fossula was measured between median lines of septa im- (usually the counter septum). Changes in septal thickness within mediately adjacent to the fossula, midway between axial and pe- individual specimens are shown by lines joining data points. Num- ripheral ends of septa bounding the fossula. Numbers beside data bers beside data points indicate frequencies greater than one. Arbitrary points indicate frequencies greater than one. Arbitrary line [in same line [doited, in same position as that for .Streptelasma subregulare position as that for .Streptelasma subregulare (Savage. 1913b) in in of (Savage, 1 9 1 3b) in Text-fig. 1 5] was used to derive proportions shown Text-fig. 161 was used to derive proportions shown part in part of Table 5. Table 5. Ordovician-Sii.urian Rugose Corals: McAuley and Elias 45

under Sticptclasma sithrcgularc (Savage, 1913b). How- ian): Keel Formation, south-central C3klahoma; Cason

ever, the new species is distinct in having more widely shale, western north-central Arkansas; Leemon For- spaced tabulae. The cardinal septum does not become mation, southern Illinois and southeastern Missouri.

short, as in S. iinicuin. Lowermost Silurian (?) (lower Lower Llandovery (?)): The Following illustrated specimens from the Gua- Kissenger Limestone Member, Bryant Knob Forma- nyinqiao Beds (Dahuanitina Beds) (Ashgill; Hirnan- tion, northeastern Missouri. tian) in the northern Guizhou Province of China have Diai;nosis. SoVwary or with peripheral offsets, gen- a septal arrangement, tabulae, and thin stereozone that erally ceratoid. Major septa typically thin, extend to resemble Strcptelasma aiusdeni. n. sp., but the septa or almost to axis throughout ontogeny. Cardinal sep- are thicker than in the latter species: tum indistinct to relatively long, cardinal fossula usually inconspicuous. Minor septa at least half the length Brachyclasma'! simplnlabulatum He. 1978, pi. 2, figs. 5a. b. 6.

Paramplexoides cylindricus He, 1978, pi. 9, figs. la-g. 5. 6, pi. 10, of major septa, commonly contraclined to contratin-

figs, la-c, 2a, b, 3a, b, 4a-c, 5, 6. gent, extend beyond narrow to very broad stereozone. Paramplexoides atleniiatum He, 1978. pi. 9. figs. 7a-c, 8a, 9. Tabulae moderately to closely spaced. Description ofcoral/a.— The greatest observed length Streptelasma leemonense Elias, 1982a and diameter are 55 mm (USNM 423387, incomplete Plate 7, figures 1-14; Plate 8, figures 1^; at both ends) and 20 mm (USNM 423401, at base of

calice), respectively. Of 1 2 individuals, six are ceratoid, Plate 9, figures 1 , 2 three are trochoid, and three are cylindrical (PI. 7, fig. Streptelasma leemonense E\\^i, 1982a. p. 56, pi. 4, figs. 1-3. 1 ). Two are straight and ten are slightly to moderately

Holotype.-XJCGM 45614 (Elias, 1982a, pi. 4, figs. curved; the cardinal side is not always convex (PI. 7,

1, 2), same interval as 20-3, 20-4, 20-5, El coll., Lee- fig. 1 ). Corallum shape in transverse section is generally

mon Formation, Section 20 (Short Farm), Cape Gi- circular, but is irregular in some cases (PI. 8, fig. 4). rardeau County, Missouri. The presence of septal grooves and interseptal ridges

Paratype.-ViCGM 45615 (Elias, 1982a, pi. 4, fig. has been verified in transverse thin sections of speci-

3), same interval as 20-3, 20-4, 20-5, El coll., Leemon mens enclosed in matrix. The measured depth of the Formation, Section 20 (Short Farm), Cape Girardeau calice is approximately 10 percent of the corallum County, Missouri. length, but calice rims in those individuals are poorly Additional material. -\JS^U 423378, 423379, in- preserved and may be incomplete. terval 23-2 (Brevilamnulella beds), EMM coll., USNM Clusters of up to about 20 individuals were collected 423380, interval 23-2a, EM coll., USNM 423381- at Sections 23, 20, and 15 (USNM 423391, 423401, 423389, interval 23-3, EMM coll., USNM 423390, 423403). Smaller clusters were also found, consisting 423391, interval 23-3, EM coll., USNM 423392, of at least six coralla at Section 14 and five at Section

423393, interval 23a- 1 , EM coll.. Keel Formation, Sec- 20 (USNM 423405, 423400). Enclosure in matrix or tion 23 (Lawrence Quarry), Pontotoc County, Okla- poor preservation makes it difficult to establish wheth- homa; USNM 423394, interval 33-1, C coll., Cason er they represent true colonies or pseudocolonies. Evi- shale. Section 33 (Buffalo River), Searcy County, Ar- dence from one large cluster and several other coralla kansas; USNM 423395, interval 31-1, EMZ coll., indicates that budding did occur (USNM 423378, USNM 423396, interval 31-lb. EMZ coll., Leemon 423382, 423401; PI. 8, figs. 1-4). Definite peripheral Formation, Section 31 (Thebes North), Alexander offsets are located between the older and younger walls County, Illinois; UI C- 1448a, S coll., Leemon For- at constrictions, and are initially oriented approxi- mation [labelled "Edgewood"], Gale Section, Alex- mately parallel to the protocorallite. Some diverge out- ander County, Illinois; USNM 423397, 423398, in- ward in later stages. Offsets are found on alar, counter, terval 20-1, EMM coll., USNM 423399, 423400, and cardinal quadrants of the parents with about equal interval 20-1, EM coll., USNM 423401, interval 20- frequency. One specimen has at least seven at the same 3, EM coll., USNM 423402, interval 20-4, EM coll., height, and they are distributed over about 75 percent Leemon Formation, Section 20 (Short Farm), Cape of the circumference (USNM 423382). Some offsets Girardeau County, Missouri; USNM 423403, 423404, become quite large. In one cluster, several of the big interval 15-1, EM coll., Kissenger Limestone Member, individuals with numerous offsets began as buds them- Bryant Knob Formation, Section 15 (Calumet), Pike selves (PI. 8, figs. 1-4). County, Missouri; USNM 423405^23407, interval Other specimens could represent budding or a gre-

14-1, EM coll., Kissenger Limestone Member, Bryant garious, epizoic habit (PI. 7, fig. 9). In two clusters, Knob Formation, Section 14 (Higginbotham Farm), several relatively small coralla located on only one side Pike County, Missouri. of a larger individual are oriented approximately per-

Occurrences.— \JpptvmosX Ordovician (Gamach- pendicular to it (USNM 423400, 423403). They may 46 Bulletin 333

have used an exposed side as a substrate for attachment. In other cases, small coralla occur on the exterior of a large individual that lacks constrictions at those sites (e.g.. USNM 423384). They are usually oriented at high angles to the growth axis of the host or pro- locorallite. Peripheral offsets and or epizoic individuals are present in approximately 25 percent of the specimens studied herein. Ontogeny and internal structures. —The relationship between number of septa and corallum diameter is shown in Text-figure 22. Major septa extend to or almost to the axis, where they commonly meet in small groups, in early ontogenetic stages (PI. 7. figs. 11, 14,

PI. 8, figs. 1. 2), intermediate stages (PI. 7. figs. 3, 5-

7, 9, 12. PI. 8, fig. 3), and late stages (PI. 7, figs. 4, 10,

13, PI. 8, fig. 4). A counterclockwise axial whorl is present in some specimens. The septa are usually slightly curved to wavy. They are generally thin, but can be slightly to (rarely) greatly dilated in early stages. The cardinal septum is as long as or longer, and in some cases slightly thicker, than other major septa. The cardinal fossula is usually inconspicuous, having the same width and shape as other pairs of interseptal

chambers, but in some coralla it is slightly wider or biconvex in transverse section. The length of minor

septa is generally about 50 percent of the corallum radius, but varies from 30 to 70 percent. Minor septa are commonly contraclined to contratingent. They ex- Ordovician-Sii.urian Rugose Corals: McAuley and Elias 47

Llandovery orSwcdcn(Ncuman, 1969, pp. 21-23, figs. Microstructurc.— The microstructurc in transverse 13, 14; Neuman, 1975, pp. 335, 336). All have rela- and longitudinal thin sections appears to be the same tively long minor septa, thin major septa that com- as described for Streptelasma leemonense Elias. 1 982a. monly meet in groups axially and in some cases form Discussion.— The three specimens described above an axial whorl, a cardinal septum that is indistinct to are distinguished by their cardinal and counter septa, long, and a typically inconspicuous cardinal fossula. which form a median lamella during early to inter-

However, tabulae are convex upward in .V. elnaense mediate stages and remain longer than other major and S. ecccnlricum, offsets are intracalicular in .S'. el- septa in late stages. Other characteristics lie within the naense and S. ostrogothicum and lacking in S. eccen- range of variability documented herein for Strepte- tricum, septal lobes form a very small axial structure lasma leemonense Elias, 1982a, although the number in S. elnaense. and in S. eccentricum the axis is dis- of septa is comparatively high (Text-fig. 22) and the placed toward the counter side during late stages and minor septa are relatively short. These three incom- the stereozone is very thin. The maximum length of plete specimens were found together with S. leemo- minor septa in S. leemonense is greater than in the nense. but it is uncertain whether they are atypical other three species. coralla of that species, or represent a closely related new species that is rare in the Keel Formation at Sec- Elias, 1982a Streptelasma species cf S. leemonense tion 23 (Lawrence Quarry). We therefore identify them Plate 9, figures 3-7 as Streptelasma sp. cf .S. leemonense Elias, 1982a. Material. -ViSnU 423408, interval 23-2a, EM coll., USNM 423409, interval 23-3, EM coll., USNM Streptelasma species A 423410, interval 23a-l. EM coll. Plate 9, figures 8, 9; Plate 10, figures 1-5 OfCi//vc/;a'. —Uppermost Ordovician (Gamachian): Keel Formation, Section 23 (Lawrence Quarry), Pon- Material. -USNM 423411-423413, interval 15-0, totoc County, south-central Oklahoma. EM coll. Description ofcoralla.—The greatest length and di- Occurrence. —Vppermosl Ordovician (Gamachian): ameter are estimated to be 30 mm and 22 mm, re- Noix Limestone, Section 15 (Calumet), Pike County, spectively (USNM 423410, incomplete apex and calice northeastern Missouri. rim). Growth form is slenderly ceratoid and slightly Description ofcoralla.— AW three individuals are epi- curved (USNM 423409), to questionably trochoid zoic, less than 3 mm in diameter, and probably less (USNM 4234 10). Septal grooves and interseptal ridges than 5 mm in length. They are located on what is are present (USNM 423408). apparently the upper side of a single, horizontally ori- Ontogeny and internal structures.— The relationship ented bryozoan (PI. 9, figs. 8, 9, PI. 10, figs. 1-5). Two between number of septa and corallum diameter is are spaced about 1 1 mm apart, and the third is situated shown in Text-figure 22. Major septa extend to or near approximately 20 mm from the others on what is likely the axis, where some meet in pairs or small groups, in the same colony. The coralla grew subparallel and then early (PI. 9, fig. 6) to intermediate ontogenetic stages perpendicular to the surface of the bryozoan. They are

(PI. 9, fig. 4). All except the cardinal and counter septa probably attached by their cardinal sides. The apical withdraw from the axis during late stages (PI. 9, figs. part of the attached side is flattened and conforms to

5, 7). Major septa are straight to usually slightly curved. the shape of the host, whereas unattached portions are They are nondilated to slightly dilated during early to round in transverse section, with septal grooves and intermediate stages, and thin in late stages. interseptal ridges. The bryozoan colony eventually grew The cardinal and counter septa are longer than other around the sides of the epizoic coralla. major septa throughout ontogeny. They are joined to Ontogeny and internal structures.— Major septa form a median lamella during early to intermediate numbering 12 to 17 are present at diameters of 2 to 3 stages, and become disconnected and gradually with- mm. In early ontogenetic stages they can be as little as draw from the axis in late stages. Their axial ends are 50 percent of the corallum radius in length (PI. 10, fig. dilated. The cardinal fossula is inconspicuous. Minor 3), or extend to the axis (PI. 10, fig. 1). During inter- septa are long, but their length is less than half the mediate to late stages, they meet at the axis in one corallum radius. They are seldom contraclined or con- individual (PI. 10, figs. 4, 5). In another, a few fine tratingent. Minor septa extend beyond the stereozone, septal lobes at the axis occupy less than 10 percent of which has a thickness that is about 10 to 30 percent the corallum diameter (PI. 9, figs. 8, 9). The third has of the corallum radius. several coarse septal lobes occupying almost 20 percent Tabulae are convex upward in the septal region, and of the corallum diameter (PI. 10, fig. 2). Major septa

flat to concave upward in the axial region (PI. 9, fig. vary from relatively straight to wavy, and are thin

3). throughout ontogeny. 48 Bulletin 333

In one specimen, what ma> be the cardinal septum Streptelasma (?) parasiticum Ulrich in Winchell and is longer than other major septa (USNM 4234 1 2). The Schuchert, 1895, from the upper Middle Ordovician cardinal fossula is indistinct. Minor septa, where pres- 'Trenton limestone" (= Platteville Limestone; Black- ent, are ver>' short. Thickness of the stereozone varies riveran) and "Trenton shales" (= Decorah Shale; from less than 5 percent to about 8 percent of the Rocklandian) of Minnesota, forms pseudocolonies or corallum radius. colonies attached to bryozoans (Winchell and Schu- Tabulae appear to be present in the late stage of one chert, 1895, pp. 89, 90, fig. 6; see Bassler, 1950, pp. indi\idual(Pl. 10, fig. 5), but longitudinal sections could 14, 15). The coralla are only several mm long, but not be prepared for confirmation. internal structures are unknown. Alicroslructure.— The microstructure could not be We identify the specimens described herein as Slrep- distinguished in transverse thin sections of these small telasma sp. A because of the uncertainties stated above. coralla having ver\' thin septa and stereozones. Genus Dybowski, 1873 Discussion.— The epizoic habit and morphology of GREWINGKIA the three specimens described above are similar to Grewingkia species A Streptelasnia divaricans (Nicholson. 1875). The latter, Plate 10, figures 6-10 highly variable species is known from the Upham Do- Material. -\]S,^y[ 423414, interval 23-3, EM coll.. lomite of the Value (middle Member Second Dolomite Keel Formation, Section 23 (Lawrence Quarry), Pon- Edenian to lowermost Maysvillian), Montoya Group, 4- totoc County, Oklahoma; USNM 4234 1 5, interval 1 New Mexico and Texas (Elias, 1985, pp. 37, 38, 40, 2, EM coll., Kissenger Limestone Member, Bryant figs. 14.1-14.12), and the following Richmondian units: Knob Formation, Section 14 (Higginbotham Farm), Dillsboro Formation. Formation, Whitewater and Pike County. Missouri. Rowland, Bardstown, Saluda Dolomite, and Preach- Occurrences. — XJppermosX Ordovician (Gamachi- ersville members of the Drakes Formation. Cincinnati an): Keel Formation, south-central Oklahoma. Low- Arch region. Kentuck\-Indiana-Ohio: Bay de Noc ermost Silurian (?) (lower Lower Llandovery (?)): Kis- Stonington Formation, Michigan; and Mea- Member, senger Limestone Member, Bryant Knob Formation, ford and Kagawong beds, upper member, Georgian northeastern Missouri. Bay Formation, Ontario (Elias, 1982a, pp. 53-56, pi. Description of coralla.— The largest specimen is 25 1, figs. 1^1, pi. 2, figs. 1-16, pi. 3, figs. 1-23; Elias, mm long and 14 mm in diameter (LJSNM 423415, 1983b, pp. 9, 10, pi. 2, figs. 16-33). Although coralla apex and calice incomplete). Its growth form is tro- of 5. divaricans are small (Elias, 1982a, fig. 14), the choid and curved. An attachment structure is located individuals from the Noix Limestone are even smaller. on what is almost certainly a cardinal-alar quadrant However, it is uncertain whether they are mature be- (PI. 10, fig. 8). three are known, all are at- cause only and probably Ontogeny and internal structures.— The relationship tached to the same host. between number of septa and corallum diameter is D shown in Text-figure 23. In early ontogenetic stages, a O <30 few septal lobes are present at the axis (PI. 10, fig. 7). An axial structure of septal lobes and lamellae develops during intermediate stages (PI. 10, figs. 8, 9). In late stages, major septa become relatively short, and the moderately complex axial structure comprising long, 20 curved to contorted septal lobes and lamellae has a

radius that is 40 to 50 percent of the corallum radius O Qrtwingkia sp A (PI. 10, figs. 6, 10). The septa are straight to slightly 3 transverse sections from 1 coratlun curved and thin to moderately thick in all known stages. D Bodophyllum thorti 10 The cardinal septum and fossula are inconspicuous. 3 transverse sections from 1 corailurr In late stages, the length of minor septa is 40 percent • Kaelophyllum oklBhom»ns» of the corallum radius. Minor septa extend beyond the 14 transverse sections from 6 coralla stereozone, which has a thickness of 10 to 20 percent of the corallum radius. 5 10 15 20 Several tabulae are apparent in one transverse sec- DIAMETER (mm) tion (PI. 10, fig. 6). Texl-figurc 23. — Relationship between number ol'major septa and Microstructure.— The specimens are poorly pre- corallum diameter in OrewinKkta sp. A. Hadophylluin shurli Elias, served, but in transverse thin sections the septa appear 1 982a, and Keelophyllumoklahomen.se. n. gen., n. sp. Number beside datum point indicates frequency greater than one. to be fibrous. Ordovician-Silurian Rugose Corals: McAuley and Elias 49

Discussion. — Although the coralla described above cases, they form a slight counterclockwise whorl. Septal are poorly preserved, they clearly dificr from other dilation is great to complete in early ontogenetic stages, streptelasmatids documented herein in having a large and generally decreases in later stages. Septal carinae axial structure of septal lobes and lamellae. That struc- are apparent m a mold of the calice (PI. 13, fig. 6). The ture is characteristic of Grewingkia Dybowski, 1873 cardinal septum becomes thin and short near the base

(see Elias, 1981, pp. 11, 12; Elias, 1982a, pp. 65, 66). of the calice (PI. 12, fig. 9), and the fossula has parallel The nature and arrangement of major septa and sides. The counter septum is long in some sections (PI. length of minor septa in these specimens are similar 12, fig. 9, PI. 13, fig. 7). The minor septa are short. to those of the following species: Grewingkia penob- Tabulae are present in most specimens. scotensis Elias, 1982a, from Upper Ordovician (Ash- Discussion. —The features described above are char- gill) strata within an unnamed formation in Penobscot acteristic of Rhegniapliylluni Wedekind, 1927 (see County, Maine (Elias, 1982a, pp. 72, 73, pi. 12, figs. Weyer, 1974, pp. 159-162; Neuman, 1977, p. 73; Laub, 1-6), and within the Horseshoe Gulch unit in the east- 1979, pp. 92-95). A lengthened counter septum has ern Klamath Mountains ofCalifomia (Elias and Potter, been reported in R. daytonensis (FocTsle. 1890), from

1984, pp. 1209, 1210, fig. 2h-l); Grewingkia anguinea the Brassfield Formation (Llandovery) of Ohio and (Scheffen, 1933) from Stage 5a (Ashgill) in Norway Kentucky, by Laub (1979, p. 98). Of the two coralla (Neuman, 1969, pp. 48-50, figs. 39^1); and Grewing- from north-central Arkansas documented herein, one kia contexta Neuman, 1969, from the Boda Limestone is attached to grains of sediment (PI. 1 2, fig. 7) and the

(Ashgill; Hirnantian) of Sweden (Neuman, 1969, pp. other is an attachment site for several smaller individ- 43, 45-48, figs. 34-38). However, in late stages the uals that likely belong to the same species (PI. 12, fig.

axial structure is simpler with fewer lamellae in G. 1 1 ). Attachment structures have not been reported pre- penohscotensis, septal lamellae are typically shorter in viously in this genus (Laub, 1979, p. 93; see also Neu- G. anguinea, and lamellae are more numerous and the man, 1988, p. 101). axial structure is more complex in G. contexta. We Because of the small number of specimens, the range refer to them as Grewingkia sp. A because of the limited of variability at each locality is unknown. Therefore, amount of data available from the two coralla de- we are unable to determine the number of species rep- scribed above. resented in this collection, or to assign specimens to existing species. We refer to these coralla as Rheg- Genus RHEGMAPHYLLUM Wedekind, 1927 maphyllum sp. Rhegmaphyllum species Subfamily DINOPHYLLINAE Wang, 1947 Plate 12, figures 7-11; Plate 13, figures 1-9 Genus DINOPHYLLUM Lindstrom, 1882 A/<3/ma/. -USNM 423422, 423423, EMZ coll., basal 0.3 m, Cason oolite, St. Clair Spring Section, In- Dinophyllum species dependence County, Arkansas; USNM 423424, inter- Plate 13, figures 10-16 val 1 7- la, EM coll., USNM 423425, interval 17-3, EM Material. -VSNM 423430, interval 17-3, EM coll., coll., limestone facies at base of Bowling Green Do- limestone facies at base of Bowling Green Dolomite, lomite, Section 17 (Clarksville), Pike County, Mis- Section 1 7 (Clarksville), Pike County, Missouri; USNM souri; USNM 423426, interval 17-2b, EM coll., Hme- 423431, interval 17-2, EMM coll.. Bowling Green Do- stone facies within Bowling Green Dolomite, Section lomite, Section 17 (Clarksville), Pike County, Mis- 17 (Clarksville), Pike County, Missouri; USNM souri; USNM 423432, interval 5-2, EMZ coll., Elwood 423427, 423428, interval 5-2, EMZ coll., Elwood For- Formation, Section 5 (Schweizer North), Will County, mation, Section 5 (Schweizer North), Will County, Il- Illinois; USNM 423433, interval 32-2b, EZ coll., linois; USNM 423429, interval 32-2a, EZcoll., Mosa- Mosalem Formation, Section 32 (Thomson East), Car- lem Formation, Section 32 (Thomson East), Carroll roll County, Illinois. County, Illinois. Occurrences.— Lower Silurian (upper Lower Llan- Occurrences.— XJp^ermosX Ordovician (Gamachi- dovery): Bowling Green Dolomite, northeastern Mis- an): Cason oolite, eastern north-central Arkansas. souri; Elwood Formation, northeastern Illinois; upper Lower Silurian (upper Lower Llandovery): Bowling Mosalem Formation, northwestern Illinois. Green Dolomite, northeastern Missouri; Elwood For- Description.— These medium-sized solitary coralla mation, northeastern Illinois; upper Mosalem For- have a convex cardinal side. The major septa are non- mation, northwestern Illinois. dilated in late ontogenetic stages, and form a generally Description.— ThQst small solitary coralla have a conspicuous counterclockwise whorl near the axis. The convex cardinal side. The major septa extend to or cardinal fossula is distinct and moderately deep. The near the axis, where they meet in small groups. In some minor septa are short. Longitudinal sections of one 50 Bulletin 333

specimen reveal tabulae that are steeply convex up- cardinal septum throughout ontogeny (Neuman, 1969. ward (PI. 13. figs. 10. 11). pp. 54-56). However, it is not certain that recognition

Discussion. —The features described above are char- of two genera is warranted (McLean, 1 974. p. 43; Neu- acteristic of Dinophylluni Lindstrom. 1882 (see Laub, man. 1977. p. 74). With the generally poorly preserved

1979. pp. 63. 64). The number of specimens is small material examined herein, it is not possible to dem- and the ontogeny of some is incompletely known. onstrate that the cardinal septum becomes short below

Therefore, we are unable to determine the number of the calice. However, in one specimen it is short a small species represented, or assign them to existing species. distance above the base of the calice. Because the num- We refer to these coralla as Dinophylluni sp. ber of individuals is small and their ontogeny is incompletely known, we are unable to determine that Subfamily D.\LMANOPHYLLINAE they are conspecific or assign them to existing species. Lecompte. 1952 We refer to these coralla as Dalmanophyllum sp.

Genus DALMANOPHYLLUM Genus BODOPHYLLUM Neuman, 1969 Lang and Smith. 1939 Bodophyllum shorti Elias. 1982a Dalmanophyllum species Bodopliyllum shorn Elias, 1982a, pp. 77, 78, pi. 13, figs. 10-14. Plate 14, figures 1-8 Holotype. — UCGM 45613. same interval as 20-3, Malerial. -VCGM 45639, El coll., basal 2 m of 20-4, 20-5, El coll. Sexton Creek Limestone, Section 20 (Short Farm). Cape Occurrence. -UppermosX Ordovician (Gamachian): Girardeau County. Missouri; USNM 423434, interval Leemon Formation, Section 20 (Short Farm), Cape 17-1, EMM coll., limestone facies at base of Bowling Girardeau County, southeastern Missouri. Green Dolomite, Section 1 7 (Clarksville). Pike Coun- Diagnosis. — ty. Missouri; USNM 423435. interval 17-2a. EM coll..

Bowling Green Dolomite. Section 1 7 (Clarksville). Pike Bodophyllum with solid axial structure in early stage and a County. Missouri; USNM 423436. interval 6-1. EMM prominent dilated median septal lamella in intermediate stage. In late stage a few septal lobes and lamellae are present in axial coll.. Elwood Formation, Section 6 (Plaines West). Will structure, and median lamella is slightly dilated, irregular, and Illinois; interval 32- Ic. County. USNM 423437. EZ not connected to cardinal or counter septa. Minor septa long, coll.. Mosalem Formation, Section 32 (Thomson East), extending well beyond stereo/one (Elias, 1982a, p. 78). Carroll County, Illinois; USNM 423438. interval 10-2, Description ofcorallum. — EMM coll.. Mosalem Formation, Section 10 (Lost The coral is about 15 long and has a diameter of 8 Mound). Jo Daviess County. Illinois. mm mm a short distance below the calice where 34 major septa are Occurrences. — Lower Silurian (Llandovery): Sexton present. It is straight. The base of attachment is on the cardinal southeastern Missouri. Lower Si- Creek Formation, side, and the specimen was attached to a bryozoan. Depth of lurian (upper Lower Llandovery): Bowling Green Do- the calice is about 40 percent of the coral length (Elias, 1982a, lomite, northeastern Missouri; upper Mosalem For- p. 78). mation, northwestern Illinois. Lower Silurian (upper Ontogeny and internal structures.— Lower to Middle Llandovery): Elwood Formation, The axial structure is solid in early stages. In intermediate northeastern Illinois. stages a prominent dilated median septal lamella is connected solitary coralla Description.— These small have a to the long cardinal and counter septa and a few dilated septal convex cardinal side. The major septa are long and lobes and rare septal lamellae are present. In late stages the relatively thick. The cardinal and counter septa are elements of the axial structure are slightly dilated. The median lamella is irregular and discontinuous, and is not connected to joined to a prominent median columella that is ellip- the cardinal or counter septa. A few other septal lamellae and tical in transverse sections. A few septal lobes arise septal lobes are present. The major septa are slightly dilated septa the columella. cardinal from major around The in early stages, and non-dilated in later stages. A cardinal fos- septum is much shorter than adjacent major septa a sula is not developed (Elias, 1982a. p. 78). small distance above the base of the calice in one spec- The cardinal septum is about the same length as ad- imen (UCGM 45639). The minor septa are short. Ta- jacent major septa well up in the calice. bulae are recognizable in several specimens. narrow Discussion. —The features described above are char- The minor septa are long, extending well beyond the stereozone. Tabulae are present (Elias, 1982a, p. 78). acteristic of Dalnianophylluni Lang and Smith. 1939 (see Neuman. 1977. p. 74; Laub, 1979. pp. 79-81). In Microstructure. — In transverse thin sections, the ma- this genus, the cardinal septum becomes short just be- jor septa are fibrous in all ontogenetic stages, although low and within the calice. Bodophyllum Neuman. 1969. fibers are difficult to discern because the septa are gen- was proposed to include similar coralla having a long erally thin. The fibers appear to originate at the median ORDOVICIAN-SiU IRIAN RUGOSE CORALS: M( Aul.rV AND Elias 51

line wilhin the septum, and extent outward in the di- That feature, and in particular the long, thin septa and rection tjfthe corallum axis. In the stcrco/one, major weakly developed axial structure, are characteristic of and minor septa are expanded into lateral contact along Cyathactis Soshkina //( Ivanova et a/.. 1955 (see Laub, a contorted suture. 1979, pp. 142, 143). However, the degree of septal D;.sr;/.v.v/o«.— Additional material was not found dilation in early stages of these incomplete, poorly pre- during the present study. This specimen was assigned served specimens is unknown. It is possible that more to Bodophylliini Ncuman, 1969, because it has a solid than one species is represented in this small collection. axial structure in early ontogenetic stages and a prom- Because of these uncertainties, we refer to the speci- inent dilated median septal lamella in intermediate mens as Cyathactis! sp. stages (Elias, 1 982a, p. 78). However, it was noted that, Suborder MONACANTHIN A Neuman, 1984 unlike BodophyUuni shorti Elias, 1982a, other species Family LAMBELASMATIDAE Weyer, 1973 of the genus have a solid axial structure in late stages Subfamily COELOSTYLINAE Weyer, 1973 as well. It is possible that this corallum represents a genus in the Subfamily Streptelasmatinae Nicholson Genus KEELOPHYLLUM, new genus 1889. The arrangement in Nicholson and Lydckker, Derivation of name. —The generic name refers to the septa are similar to Grew- of septa and length of minor landowner after whom the Keel Formation was named ingkia sp. A, but in B. shorti the number of septa is by Maxwell (1936, p. 50). tabulae are present in trans- greater (Text-fig. 23), more Type and only species. — Kcclophyllum oklahomense, sections, the axial structure differs in being verse and n. sp.; Keel Formation (uppermost Ordovician; Ga- solid in early stages, including a median lamella in machian), south-central Oklahoma. small in intermediate stages, and being comparatively Diagnosis. SoWlary, ceratoid to trochoid, cardinal late stages. side convex. Septa monacanthine, imperforate, radially arranged, taper axially, some with irregularly ar- Suborder CYATHOPHYLLINA Nicholson in ranged small carinae. Minor septa very long. Axial Nicholson and Lydekker, 1889 structure of moderate size and complexity, with septal Family PTYCHOPHYLLIDAE Dybowski, 1873 lobes and lamellae. Tabulae numerous. Keelophyllutn. n. gen., in Genus CYATHACTIS Soshkina Discussion.— We include the Suborder Monacanthina Neuman, 1984, because in Ivanova et ai, 1955 of its monacanthine microstructure. Placement within Cyathactis? species the Family Lambelasmatidae Weyer, 1973, is justified Plate 14, figures 9-14 by the ceratoid to trochoid growth form, and lack of Material. -\]Sny\. 423439, interval 23-4, EM coll., dissepiments (refer to Neuman, 1984, p. 125; Elias, Cochrane Formation, Section 23 (Lawrence Quarry), 1986a, p. 15). This family was originally intended to Pontotoc County, Oklahoma; USNM 423440, interval include corals with porous septa (Weyer, 1973, p. 33). 17-2, EMM coll.. Bowling Green Dolomite, Section However, the presence of perforations requires veri- 17 (Clarksville), Pike County, Missouri; USNM fication in most of the included genera (see Hill, 1981, 423441, interval 29-2, EMZ coll., Elwood Formation, pp. 183-185). Keelophyllum may be related to the Neo- Section 29 (Sears Pit), De Kalb County, Illinois; USNM tryplasmatidae Elias, 1986a. Its septal arrangement, similar to 423442, interval 9- 1 , EMM coll., Mosalem Formation, axial structure, and long minor septa are Section 9 (Winston), Jo Daviess County, Illinois. Neotryplasma Kaljo, 1957, but it differs in having im- Occurrences.— l.o'wer Silurian (Llandovery): Coch- perforate septa and lacking dissepiments. Neotryplas- rane Formation, south-central Oklahoma. Lower Si- ma is known from the upper Middle and LJpper Or- lurian (upper Lower Llandovery): Bowling Green Do- dovician of the Ural region, U.S.S.R., and the Upper lomite, northeastern Missouri; Elwood Formation, Ordovician of the Estonian S.S.R. and Texas (Elias, northeastern Illinois; upper Mosalem Formation, 1986a, p. 16). northwestern Illinois. The subfamilies of Lambelasmatidae Weyer, 1973. Description.— These moderately large solitary cor- were reviewed by Neuman (1984, p. 125). We place alla have a convex cardinal side. The numerous major Keelophyllum. n. gen., within the Coelostylinae Weyer, septa are long and thin in all known stages. A few septal 1973, because of its long, radially arranged septa, con- lobes are present at the axis. The minor septa are long, vex cardinal side, and tabulae. It most closely resem-

and generally contraclined to contratingent. Tabulae bles Rectigrewingkia Kaljo, 1 96 1 , known from the Up- and a dissepimentarium are present. per Ordovician of Baltoscandia (see Neuman, 1986, Discussion. —The coralla described above differ from pp. 358-364). However, the axial structure in Recti- all others documented herein in having dissepiments. grewingkia is larger than in Keelophyllum. Keelophyl- 52 Bulletin 333

lum oklahomense, n. gen., n. sp.. does not appear to Attachment by the cardinal side is confirmed in the have the "granular" axial structure seen in Swedish large corallum and in the uppermost epizoan. Another specimens of Rectigrewingkia anihelion (Dybowski, specimen has a sharp bend and possibly an attachment

1873), which is the type and only well-known species structure at the apex (PI. 1 1, fig. 6). Depth of the calice

of that genus (Neuman. 1986. figs. 1 la-1. 13c). How- could not be established accurately, but is likely less ever, monacanths seem to be somewhat less conspic- than 30 percent of the corallum length. A low calicular uous in a corallum from the type locality in the Es- boss is formed by elements comprising the axial struc-

tonian S.S.R. (Neuman, 1986, fig. 13e-g). The radial ture. arrangement of axially tapering septa is more pro- Ontogeny and internal structures. —The relationship nounced in Keelophyllum than in Recligrewingkia. In between number of septa and corallum diameter is transverse sections, some septa in Keelophyllum have shown in Text-figure 23. Major septa extend to or al- small, irregularly arranged carinae, whereas septa in most to the axis, where they meet in groups that are Recligrewingkia have relatively smooth sides. Tabulae commonly enclosed in sclerenchyme, in early onto-

are numerous in Keelophyllum. but sparse or absent genetic stages (PI. 11, fig. 10, PI. 12, fig. 4) to early

in Recligrewingkia (Neuman, 1986. p. 361, fig. 13d). intermediate stages (PI. 1 1, fig. 1 1, PI. 12, fig. 5). The major septa withdraw from the axis and an axial struc- Keelophyllum oklahomense, new species ture develops during late intermediate stages (PI. 1 1, Plate 1 1, figures 1-12; Plate 12, figures 1-6 fig. 1, PI. 12, fig. 2) to late stages (PI. 1 1, figs. 2, 12, PI.

Derivation ofname. —The specific name refers to the 1 2, figs. 3, 6). The axial structure comprises septal lobes state in which the specimens were found. and numerous paliform to long and contorted septal Holotype. -VSNM 423416, interval 23-3, EM coll.. lamellae in some cases thickened by sclerenchyme, and Section 23 (Lawrence Quarry), Pontotoc County, Okla- occupies about 30 percent of the corallum radius in homa. late stages. Major septa are curved and somewhat ir- Paratypes. -VSNM 423417, interval 25-1, EMM regularly oriented in early stages, but become straight coll.. Section 25 (Hunton), Coal County, Oklahoma: and radially arranged in later stages. They are thin to USNM 423418, interval 23-3, EMM coll., USNM moderately thick, and taper axially. Some have small, 423419, 423420, interval 23-3, EM coll., USNM irregularly arranged carinae.

423421, interval 23a- 1, EM coll.. Section 23 (Lawrence The cardinal septum is indistinct, but is slightly Quarry), Pontotoc County. Oklahoma. thicker than other major septa in one individual Occurrence. — Uppermosl Ordovician (Gamachian): (USNM 423417). The cardinal fossula is inconspic- Keel Formation, south-central Oklahoma. uous. Minor septa are about two-thirds as long as ma- Diagnosis. —Sepia thin to moderately thick, in lat- jor septa in early stages, and some are contraclined to eral contact at periphery to form moderately thick ste- contratingent. By late stages, they extend up to 95 per- reozone. Cardinal septum and fossula inconspicuous. cent of the length of major septa; very few are con- Minor septa more than two-thirds the length of major traclined and none are contratingent. Minor septa ex- septa. Axial structure in late stages consists of septal tend beyond the stereozone, and taper axially. lobes and numerous paliform to long and contorted Thickness of the stereozone decreases during ontogeny, septal lamellae in some cases thickened by scleren- from 25 percent of the corallum radius in early stages chyme: occupies about one-third of corallum radius. to 15 percent in late stages. Tabulae con\ ex upward in septal region, generally with The complete and incomplete tabulae are convex upturned peripheral edges; slightly concave to greatly upward in the septal region, and commonly have up- convex upward in axial region. turned peripheral edges (PI. 11, figs. 7-9, PI. 12, fig.

Descripiion ofcoralla. — The greatest observed length 1 ). In the axial region, they are slightly concave upward and diameter are 50 mm and 21 mm, respectively to greatly convex upward. The close spacing of tabulae (USNM 423418, apex and calice incomplete). Coralla within the cardinal fossula in one transverse section are generally trochoid (USNM 423416, 423420, two suggests that they are depressed within that structure

; , (PI. fig. individuals in USNM 42342 1 PI. 1 1 fig. 6) and curved 11, 1).

(USNM 423418, 423421), but some are ceratoid Microstructure. —\r\ transverse thin sections (PI. 1 1,

(USNM 423417-423419; PI. 12, fig. 1) and possibly fig. 3), adjacent septa are expanded into lateral contact straight (USNM 423417). Septal grooves, interseptal along a contorted suture in the stereozone. The septal ridges, and rugae are preserved on most specimens. microstructure is clearly different from the fibrous type

One corallum that is epi/oic on a halysitid colonial seen in associated specimens of St reptelas ma subregu- corallum has two small individuals attached to itself lare (Savage, 1913b) and Slreptelasma leemonense (PI. 12, figs. 4-6). They are possibly also epizoans; Elias, 1982a, and appears to be trabeculale (compare

evidence to suggest an origin as offsets was not seen. PI. 11, fig. 3, with Neotryplasma Jloweri Elias, 1986a Ordovician-Siiurian Rugosf. Corals: McAuley and Elias 53

1 1 panel I ; Barrick, 1 986, fig. 39, sec. Ca 1 1 ). Collecting intervals [Elias, 1986a, fig. 5.1]). Monacanthscan be rccogni/cd (a , 21-1, 21-la to 21-lc, each in a different lens of bioclastic limestone. in some longitudinal thin sections, and are inclined 22 (Cedar I'llluf^c).— Turner Falls, Oklahoma Quadrangle: 437 from the periphery of the corallum toward the axis at mm E, 326 mm N: SE'A NE'A NW'A sec. 30, T 1 S, R 2 E. Cut on an angle of about 40 degrees (PI. 1 1, figs. 4, 5). The west side of U.S. Route 77. 0.5 km south of junction with Interstate septa are imperforate, but the edges of some are acan- Route 35. just north of Cedar Village, Murray County. Oklahoma enlarged improved since description by Amsden, I960, thine(Pl. 12, fig. I). (section and 256-258, sec. Ml panel 1: Barrick, 1986, fig. 39, sec. Ml 7; Discussion. —The six specimens described above dif- pp. 7, see also Amsden in Ham, 1973. fig. 35). fer from all others documented herein in having mon- 25 (Hi)nlon). — Wapanucka North, Oklahoma Quadrangle: 14 mm niicrostructure, and we assign them to Kee- acanthine E, 519 mm N; NE'/t SE'A NE'/. sec. 7, T I S. R 8 E. Exposure 0.5 lophylluni oklafunuense. n. gen., n. sp. The two km south of northeast comer of section. Coal County, Oklahoma. 184- specimens of Grewingkia sp. A differ in having a larger Base oftype section of Hunton Group (Amsden, 1960, pp. 182. 188, sec. CI, panel 2, pi. B). axial structure, shorter minor septa, and apparently 24 (Coal Creek). — Harden City, Oklahoma Quadrangle: 253 mm fibrous microstructure. E, 208 mm N: NW'A SE'A NW'A sec. 22, T I N, R 7 E. Exposure The only previously described species having radi- on north bank of Coal Creek, 0.4 km east ofGobbler Knob, Pontotoc ally arranged wedge-shaped septa, very long minor sep- County. Oklahoma (Amsden, 1957, fig. 5: Amsden, 1960, pp. 279-

1: 1961, fig. 25; Amsden, 1986. fig. 13: ta, an axial structure of septal lobes and lamellae, and 282, sec. P9, panel Amsden, Bamck, 1986, fig. 39, sec. P9). numerous tabulae that resemble Keelophylluni okla- 23 I Lawrence Quarry).— M\\oio. Oklahoma Quadrangle: 93 mm homense. n. gen., n. sp., is Grewingkia cuneata Mc- E, 302 mm N to 98 mm E. 296 mm N: NW'A SE'A NE'A sec. 36, the Schu- Lean, 1977, based on a specimen from Cape T 3 N, R 5 E (northern site): and 92 mm E, 282 mm N: NW'A NE'A chert Formation (lower Upper Llandovery) of SE'A sec. 36, T 3 N, R 5 E (southern site). East side of Ideal Cement northwestern Greenland (McLean, 1977, pp. 11, 12, Company quarry at Lawrence, Pontotoc County, Oklahoma. Col- lecting intervals 23-1, 23-2. 23-2a, 23-3, 23-4 at northern site. 23a- pi. 1, figs. 8, 10, 12). Grewingkia cuneata differs in 1 at southern site. Type section of Keel Formation and Ideal Quarr\ having more septa and developing an axial structure Member (Amsden. 1960, pi. I, figs. 1, 2, panel 2, pi. A: Amsden. latest stage, its axial at smaller diameters. In the known 1974, p. 87, loc. P22: Amsden, 1986, figs. 5. 6. 15: Bamck, 1986, structure consists of fine septal lamellae concentrated fig. 39, sec. AQL). at the periphery and a few coarse lamellae at the axis. B. Western north-central Arkansas The microstructure of G. cuneata is not known, and

is therefore uncer- its relationship to K. oklahomense 33 (Buffalo /?;ver). — Marshall, Arkansas Quadrangle: 35 mm E, tain. 512 mm N: NE'A SWA and NW'A SE'A sec. 36, T 16 N, R 17 W. Exposure on north bank of Buffalo River, 0.5 km east of bridge on U.S. Route 65, Searcy County, Arkansas (Lemastus. 1979. pp. 86-

APPENDIX 88.pl. 1: Craig, 1984, p. II, fig. 2). Stratigraphic Sections C. Southern Illinois and southeastern Missouri Introduction 31 (Thebes North).— Thebes. Illinois-Missouri Quadrangle: 157 The locations of stratigraphic sections are designated mm E, 506 mm N: SE'A SE'A sec. 5, T 15 S, R 3 W. Exposure on States Geological Survey topographic using United cast bank of Mississippi River, 1.5 km southwest of Gale and 1.8 quadrangle maps (1:24,000 scale). Precise coordinates km north of Thebes, Alexander County. Illinois (Savage, 1910. pp.

fig. 20, 2 ; Savage, 1917, following the map name are measured first east and 331,332, pi. 36, a; Savage, 1913b, pp. 1 pp. 7-10, fig. then north from the southwest comer of the map. De- 77-79; Weller, 1940, pp. 8-10: Pryor and Ross, 1962, pp. 3: Satterfield, 1971. p. 266, fig. 1; Amsden, 1974, pp. 23, 24, 86, scriptions of the sections and lists of fossils are con- loc. M: Thompson and Satterfield, 1975. pp. 77, 78, sec. 1. fig. 8: tained in the references cited under each entry. Kolata and Guensburg, 1979, p. 1 121, loc. I, fig. 1; Amsden, 1986.

pp. 29, 30, fig. 22). Collecting interval 31-1 in m situ strata. 31-la Province Edgewood and 31-lb in loose blocks. Quadrangle: precise co- The six outcrop areas (A-F) are outlined in Text- Gale Section.— Thebes. Illinois-Missouri ordinates unknown: NE'A sec. 4. T 15 S, R 3 W. Abandoned quarry figure lA. All the numbered sections (but not Gale 0.4 km southeast of Gale, Alexander County, Illinois (Savage. 1910, Section) were examined during this study. Locations pp. 332. 333, pi. 37. fig. a: Savage, 1913b, pp. 21. 22: Savage. 1917. of sections, positions of collecting intervals, and strati- p. 79) (for cut along State Route 3 in same vicinity, see Weller. 1940, graphic and paleontologic data are shown in Text-fig- pp. 8-10: Pryor and Ross, 1962. pp. 7-10, fig. 3: Cote, Reinertsen. and Killey, 1968, 7-10, stop 1. figs. 6. 7: Amsden, 1974. pp. 23, ures 2-5, 7, and 8. pp. 24, 86, loc. L; Amsden, 1986, p. 30). A. South-central Oklahoma 20 (Short Farm). —Cape Girardeau NE. Missouri Quadrangle: 44

mm E, 276 mm N: SE'A NE'A SWA sec. 2 1 , T 32 N, R 1 3 E. Exposure 21 ('/?ocA:Croj.s/«^A — Overbrook, Oklahoma Quadrangle: 310mm along creek channel just east of bam, 0.25 km east of State Route interval 20-1 in in E, 348 mm N; SE'/a NE'A SWA sec. 35, T 5 S. R I E. Exposure on W, Cape Girardeau County, Missouri. Collecting west bank of Hickory Creek, east side of road, 0.15 km south of situ strata, 20-2 to 20-5 in loose blocks. Type section of Leemon

bridge. Carter County, Oklahoma (Amsden, 1 960, pp. 208-2 10, sec. Formation (Amsden, 1 974, pp. 19,85, 86, loc. K, fig. 16: Thompson 2

54 Bulletin 333

and Satterfield. 1975. sec. 3. fig, 7; Elias. 1982a. p. 39. fig. 21. loc. 401 mm N; NE'A NW'A SW'A sec. 36. T 32 N. R 10 E. Exposure

20a; Amsden. 1986. pp. 31. 32. fig. 25). on north bank of Kankakee River, just southwest of loop road in 19 (Xew H WfaA — Neely s Landing. Missoun-Illinois Quadrangle: Kankakee River State Park campground, 0.3 km south of State Route 24 mm E. 254 mm N: NW'^ SWA SW'i sec. 9. T 33 N, R 13 E. 102 (Willman. 1962. pp. 82, 83, stop 2; Willman, 1973, p. 48, sec. Exposure along channel and east bank of Blue Shawnee Creek, 0.5 8). km east of New Wells. Cape Girardeau County. Missoun (Amsden. 4 (Schweizer H«r). — Channahon. Illinois Quadrangle: 302 mm

1974. pp. 21.22. 87. loc. H. fig. 1 7: Thompson and Satterfield. 1975. E. 418 mm N; SW'/4 SE'A sec. 35. T 35 N. R 9 E. Cuts on both sides p. 79. sec. 4. fig. 9; Elias. 1982a, p. 39, fig. 21. loc. 20b; Amsden. of lower (western) railroad, southeast side of Des Plaines River val-

1986. pp. 32-34) (Note; coordinates of this section are incorrect in ley. Will County, Illinois, Collecting intervals 4- 1 . 4- 1 a, 4- 1 c on west previous publications). Collecting interval 19-1 in northern part of side of tracks. Type section of Wilhemi Formation, and Schweizer exposure. 19-2 in southern part. 19-3 in loose blocks. and Birds (lower part) members (Ross. 1962, fig. I; Willman, 1962,

p. 84, stop 4; Willman, 1973. pp. 50. 51. sec. 17; Liebe and Rexroad.

D. Northeastern Missouri 1977. p. 854, loc. 8, fig. 1; Elias. 1982a. fig. 21, Will Co. sec). 5 (Schweizer North).— C^&nnahon. Illinois Quadrangle: 354 mm 18 (Kissenger). — \nmAa. Missoun-lllmois Quadrangle: 15 mm E. 449 mm N; SW'A SW'A NE'A sec. 36. T 35 N, R 9 E. Cut on

1 west E, 312 mm N; SW'4 sec. 35 (projected), T 53 N, R E. Cut on southeast side of lower (western) railroad, and ravine from there to side of State Route 79, just west of ICissenger Hill and south of southeast side of upper (eastern) railroad, at new concrete culvert, spring. Type section of Bryant Kjiob Formation and Kissenger Lime- southeast side of Des Plaines River valley. Will County, Illinois. stone Member (.Amsden, 1974. pp. 84, 85. loc. F, fig. 4; Thompson Type section of Birds Member (upper part) of Wilhelmi Formation, 97-100, sec. 11, fig. 14; 1986, and Satterfield. 1975. pp. Amsden, and Elwood Formation (Ross, 1962. fig. I; Willman. 1973, p. 50. sec. F). figs. 32. 34, sec. 16; Liebe and Rexroad. 1977. p. 854. loc. 7. fig. 1; Elias, 1982a, Missouri-Illinois Hill 17 CC/arA-jnY/e;. — Clarksville, and Pleasant fig. 21, Will Co. sec). West, Illinois-Missouri quadrangles: 333 mm E, 564 mm N (Clarks- 6 (Flames Hc.s/y.— Channahon. Illinois Quadrangle: 405 mm E,

1 West); SW'/i 9. ville) to 313 mm E, mm N (Pleasant Hill sec. T 491 mm N; NW'/j SE'A SW'A sec. 30, T 35 N, R 10 E. Cut on 53 N. R 1 E. Cut on west side of State Route 79. northern edge of southeast side of lower (western) railroad, southeast side of Des Clarksville. Pike County. Missouri (Amsden. 1974. p. 84. loc. E. Plaines River valley. Will County, Illinois. Type section of Drum- figs. 4-6; Thompson and Satterfield. 1975, pp. 99, 100. sec. 6, fig. mond, Ofierman, and Troutman (lower part) members, Kankakee Elias. 40. loc. 21a; McCracken and Barnes. 1982. fig. 13; 1982a. p. Formation (Ross, 1962, fig. 1; Willman, 1973, pp. 49, 50, sec. 14; figs. 33, sec. E). Collecting interval 17-0 at 2; Amsden, 1986. 34. Liebe and Rexroad. 1977, p. 854, loc 6, fig. 1; Elias, 1982a, fig. 21. southern end of exposure. l7-2a from southern end to central por- Will Co. sec).

17-1. I 7-2 central portion. 17-2b. 17-3 from north- tion, 17- la. from 29 (Sears ftVy. —Sycamore, Illinois Quadrangle: 347 mm E, 336 end. em mm N; SE'A NW'A and SW'A NE'A sec 1 5. T 40 N, R 5 E. Northeast 16 (Clinton Spring). — Louisiana. Missoun-Illinois Quadrangle: 3 1 portion of quarry, southeast of intersection of Barber Greene Road mm E. 312 mm N; SW'A NE'/. NW'A sec. 20. T 54 N. R 1 W. and Airport Road, 4 km northeast of Cortland. De Kalb County. west of State Route 79. Exposure just west of Clinton Spring on side Illinois (Mikulicz a/., 1985. pp. 21-23. figs. 6. 7). Collecting interval southern edge of Louisiana. Pike County. Missouri. Type section of 29- 1 just below top of sump. 29-2. 29-3 in quarry wall along incline Noix Limestone (Laswell. 1957. pp. 18. 19. sec. 4; Koenig. Martin. near pump. and Collinson. 1961. p. 34. stop 8. figs. 21, 22; Birkhead. 1967. loc. 3 (Garden Prairie). — Riley. Illinois Quadrangle: 179 mm E, 566 .Satterfield. I. fig. 4; Amsden. 1 974. p. 83. loc. B. fig. 4; Thompson and mm N; NE'A SW'A sec. 31, T 44 N, R 5 E. Abandoned quarry, 0.5 1975. p. 89. sec. 7. fig. 12; Elias. 1982a, p. 40, fig. 21. loc. 21b; km south of U.S. Route 20. McHenry County. Illinois (Willman. Amsden. 1986. fig. 34, sec. B). 1973. pp. 12. 14). 15 (Calumet).— Cyrene. Missouri Quadrangle: 415 mm E. 432 34 (Belvidere South). — Qelwdeve South. Illinois Quadrangle: 63 mm N. to 404 mm E. 434 mm N; S'/; SE'/4 sec. 21, T 53 N, R I W. mm E. 367 mm N; SE'A SW'A NW'A sec. 14. T 43 N, R 3 E. Abandoned quarry east ofStark Cemetery, 0.5 km east of State Route Abandoned quarry 0.35 km east of Stone Quarry Road, 4 km south Satterfield. 1975, 93. D, Pike County. Missouri (Thompson and p. of Belvidere. Boone County. Illinois (vicinity of Savage, 1926. p. sec. 5, figs. 15, 16). Collecting interval 15-0 in loose blocks. 15-1 in 518). in situ strata. 14 iHiggmhotham FarnU.—Cyrene, Missouri Quadrangle: 391 mm E. 418 mm N. and 392 mm E. 424 mm N; WVj NW'/. NE'A sec. 28. F. Northwestern Illinois and eastern Iowa

T 53 N. R I W. Exposures south (collecting interval 14-2) and north Illinois Quadrangle: 270 E, (collecting interval 14-1) of abandoned housc.just east of State Route 32 (Thomson Caif).— Thomson. mm 377 N; SE'A NE'A NW'A sec. 28, T 23 N, R 4 E. Quarry on rise D, Pike County, Missouri (Laswell. 1957. p. 20. sec. 5; Amsden, mm cast of Johnson Creek. 4.5 km east of Thomson. Carroll County, 1974, p. 83, loc. A, fig. 4; Thompson and Satterfield, 1975, p. 93,

Illinois. Collecting interval 32-0 in loose blocks, 32- 1 z, 32- la to 32- fig. 16). Ic. 32-2b in situ strata. 13 (Bowling Green}. — Bowhng Green. Missouri Quadrangle: 197 32-2a. m 30 (Thomson Northeast). — Thomson, Illinois Quadrangle: 207 mm mm E, 497 mm N; NW'/i NW'A sec. 24, T 53 N. R 3 W. Cut on E. 452 N; NW'A NW'A NE'A sec. 20, 23 N, 4 E. Quarry at north side of U.S. Route 54. 1.5 km northeast ofjunction with U.S. mm T R west Creek, northeast Route 61. Pike County. Missouri. Reference section of Cyrene For- top of bluff of Johnson 3 km of Thomson. mation and Bowling Green Dolomite (Koenig. Martin, and Collin- Carroll County. Illinois (vicinity of Savage. 1926, p. 527). 10 (Lost Mound). — Green Island, Iowa-Illinois Quadrangle: 288 son, 1961, fig. 15; Amsden, 1974, p. 84, loc. D, figs. 4, 7; Thompson mm E, 412 mm N; SW'A NW'A SW'A sec. 28, T 26 N, R 2 E. East and Satterfield, 1975, pp. 96, 99, fig. 1 1, sec. 8; Elias, 1982a, fig. 21; side of quarry in east bluff of Mississippi River valley, 1.3 km north- Amsden, 1986. figs. 31, 34, sec. D). west of Lost Mound. Jo Daviess County, Illinois (Willman, 1973, E. Northeastern Illinois pp. 52. 53. sec. 24). 26 (Bellevue). —Springbrook. Iowa-Illinois Quadrangle: 288 mm 7 (Kankakee River). — Qonfie\i, Illinois Quadrangle: 340 mm E, E, 559 mm N, to 262 mm E, 572 mm N; NE'A sec. 19, T 86 N, Ordovician-Sii.urian Rugose Corals: McAuley and Emas 55

R 5 E. Exposure along west side of U.S. Route 52 and south side of R 3 E. Cut on east side of U. S. Route 52, just south of King, Dubuque road in Bcllcvue State Park, Jackson County. Iowa (Whitlow and County. Iowa. Type section of Mosalcm and Tete des Morts for-

Brown, 196.1, p. 13; Ross, 1964, p. I 107, fig. 1; Rose, 1967, pp. 44, mations (Willman. 1973, p. 52, sec. 22).

45, stop .I, figs. 20, 21; Anderson, 1983, fig. 5.6). 9 (H'inston). — Hanover, Illinois Quadrangle: 41 mm E, 461 mm Eastern north-central Arkansas

N; SE'A SWi/4 NE'A sec. 1 1, T 27 N, R I E. Quarry on east side of The location of the section examined during this road, 1.8 km north of eastern end of Winston railroad tunnel, Jo

Daviess County, Illinois (Willman, 1973, p. 55, sec. 34). study is shown in Text-figures 1 A and 3. .Stratigraphic // ('.5<7m/)\7//(';. -Elizabeth, Illinois Quadrangle: 92 mm E, 558 and paleontologic data are shown in Text-figure 3. mm N; NE'A NE'A sec. I, T 27 N, R 2 E. Cut on east side of road, 3.2 km southwest of Schapville, Jo Daviess County. Illinois (Will- Si. Clair Spring .S><7/o«. —Sulphur Rock, Arkansas Quadrangle: man, 1973, p. 54, sec. 30). 209 mm E, 469 mm N; -SE'A SW'A sec. 18, T 14 N, R 5 W. Exposure 12 (Slocklon). — Kent Illinois Quadrangle: 148 mm E, 359 mm 0.5 km northeast of St. Clair Spring, 0.4 km east of U.S. Route 167. N; SE'A SW'A SW'A sec. 17, T 27 N, R 5 E. Abandoned quarry at Independence County, Arkansas (Craig, 1975b, pp. 75, 77, fig. 2; north edge of ridge, just south of road, 4 km southeast of Stockton, Lcmastus, 1979, pp. 61-64, pi. I; Craig. 1984, p. 10, fig. 2; Craig, Jo Daviess County, Illinois (Willman, 1973, p. 54, sec. 32). Wise, and McFarland, 1984, p. 31, alternate stop A, fig. 7; Craig in iS'fAV/!,?A — Menominee, Illinois-Iowa Quadrangle: 120 mm E, 105 Craig. Ethington, and Repetski. 1986, p. 40, stop 2, fig. 7: Amsden, mm N, to 113 mm E, 133 mm N; E'h SE'A sec. 27, T 88 N, 1986, pp. 20, 22, fig, 19; Barrick, 1986, p. 64, table 7).

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Geological Society of America, Bulletin, vol. 96, pp. 1 384- Lesperance, P. J., and Sheehan, P. M. 1397. 1976. Brachiopods from the Hirnantian Stage (Ordovician-Si- 719- Kaljo. D. L. lurian) at Perce. Quebec. Palaeontology, vol. 19, pp. 731. 1957. Codonophyllacea ordovika i llandoveri Pribaltiki. Eesti NSV Teaduste Akadeemia Juurves, Loodusuurujate Seltsi Liebe, R. M. the .Alexandrian Niagaran Se- Aastaraamat 1957, vol. 50, pp. 153-168. 1962. [MS] Conodonts from and 1961. Dopolnemya k izuchentyu streplelazmid ordovika Estonii. ries (Silurian) of the Illinois Basin. State University of City, dissertation, Eesti NSV Teaduste Akadeemia. Geoloogia Instituudi. Iowa, Iowa Iowa, Ph.D. 162 pp. Liebe, M., and Rexroad, C. B. Uunmused, vol. 6, pp. 51-67. R. 1977. Conodonts from .Alexandrian and early Niagaran rocks m koenig, J. W.. Martin, J. .4., and Collinson, C. W. the Joliet. Illinois, area. Journal of Paleontology, vol. 51. 1961. Guidebook, twenty-si.xth regionalfield conference, the Kan- 844-857. sas Geological Society, northeastern Missouri and west- pp. Lindstrom, G. central Illinois. Missouri Division of Geological Survey 1882. Siturische Korallen aus Nord-Russland und Sibirien. Bi- and Water Resources, Report of Investigations, No. 27, hang till Konglig Svenska Vetenskapsakadamiens, Han- 168 pp. dlingar, vol. 6, No. 18, 23 pp. Kolata, D. R., and Graese, A. M. Long. D. G. P., and Copper, P, 1983. Lithostratigraphy and depositwnal environments of the 1 987. Late Ordovician sand- wave complexes on .Anticosti Island. Maquoketa Group (Ordovician) in northern Illinois. Illi- Quebec: a marine tidal embayment? Canadian Journal of nois State Geological Survey, Circular 528, 49 pp. Earih Sciences, vol. 24, pp. 1821-1832. Kolata, D. R., and Guensburg, T. E. Mattison, B. W. 1979. Diamphidiocystis, a new mitrate "carpoid"from the Cin- 1983. [MS] Upper Ordovician and Lowermost Silurian Stratig- cinnalian (Upper Ordovician) Maquoketa Group in .south- raphy and Solitary Rugose Corals ofSouth-Central Okla- ern Illinois. Journal of Paleontology, vol. 53, pp. 1121- homa. Southeastern Missouri and Northeastern Illinois. 1135. Department of Earth Sciences, University of Manitoba, Krey, F. Winnipeg, Manitoba, B.Sc. thesis, 72 pp. Mississippi Valley area 1 924. Structural reconnaissance of the Maxwell. R. A. from Old Monroe. Missouri, to Nauvoo. Illinois. Missouri 1936. [MS] The Stratigraphy and .Areal Distribution ofthe "Hun- Bureau of Geology and Mines, ser. 2, vol. 18. 86 pp. Ion Formation". Oklahoma. Northwestern University, Ladd. H. S. Evanston, Illinois, Ph.D. dissertation, 120 pp.

1 929. The stratigraphy and paleontology ofthe Maquoketa Shale McAuley, R. J.

of Iowa: Part I. Iowa Geological Survey, vol. 34, Annual 1 983. [MS] Uppermost Ordovician and Lowermost Silurian Stra- Report (1928), pp. 305-448. tigraphy and Solitary Rugose Corals of Eastern Iowa. Lang, W. D., and Smith. S. Northwestern Illinois, and Northeastern Missouri. De- Win- 1 939. Some new generic namesfor Palaeozoic corals. Annals and partment of Earth Sciences, University of Manitoba,

Magazineof Natural History, ser. ll.vol. 3, pp. 152-156. nipeg, Manitoba, B.Sc. thesis, 145 pp. Ordovician-Sii.iirian RuciosE ("orals: Mc Auley and Elias 59

1985. [MS| ViipcnnosI Ordovician and Lowernwst Silurian Slni- 1974. ( 'ariations i Soko- L'nited Stales. University of Manitoba, Winnipeg, Man- lov, B. S. (ed.|, Drevnie Cnidana. vol. I. Akademiya Nauk

itoba, M.Sc. thesis, 243 pp. SSSR, Sibirskoe Otdelenic, Institut Gcologii i Geofiziki, McAuley, R. J., Elias, R. J., and Mattison. B. W. Trudy, vol. 201, 363 pp. Ordovician- 1975. lower Paleozoic streptelasmatid corals from .Scandi- 1 986. Succession ofsolitary rugose corals across the New Silurian boundary, east-central United States. Fourth North navia. Norsk Gcologisk Tidsskrift, vol. 55. pp. 335-359. American Paleontological Convention, University ofCol- 1977. On the ta.\onomy of lower Palaeozoic solitary streptelas- orado. Boulder, Colorado, August 12-15, 1986, Abstracts matids. Bureau dc recherchcs geologiques et minicres.

with Programs, p. A3 1. Memoires, No. 89, Second Symposium international sur McCracken, A. D. les coraux et recifs coralliens fossilcs; Paris, Septembre 69-77. 1 987. Description and correlation of Late Ordovician conodonts 1975, pp. from the D. omatus and P. pacificus graptolite zones. Road 1982. Early Silurian rugose corals of the Oslo region— a prelim-

River Group, northern Yukon Territory. Canadian Journal inary report, pp. 33-4 1 m Worsley, D. [ed.]. Field meeting, of Earth Sciences, vol. 24, pp. 1450-1464. Oslo region, 1982. Paleontological Contributions from the McCracken, A. D., and Barnes, C. R. University of Oslo, No. 278, 175 pp. 1981. Conodont hiostratigraphy and paleoecology ofthe Ellis Bay 1984. Origin and early evolution of rugose corals, pp. 1 19-126 Eormation. Aniicosli Island, Quebec, vfith special reference in Oliver, W. A., Jr., Sando, W. J., Cairns, S. D., Coates, to Late Ordovician-Early Silurian chronostratigraphy and A. G., Macintyre, I. G., Bayer, F. M., and Sorauf. J. E. the systemic boundary. Geological Survey of Canada, Bul- [eds.]. Recent advances m the paleobiology and geology of

letin 329, Part 2, pp. 51-134. the Cnidaria: Proceedings ofthe Fourth International Sym- 1982. Restudy ofconodonts (Late Ordovician-Early Silurian)from posium on Fossil Cnidaria Iand Archaeocyathids and Stro- the Edgewood Group, Clarksville. Missouri. Canadian matoporoids) held in Washington, DC, U.S.A., .August. Journal of Earth Sciences, vol. 19, pp. 1474-1485. 1983. Palaeontographica Americana, No. 54, 557 pp. McCracken, A. D., and Lenz, A. C. 1986. Rugose corals from the Upper Ordovician erratic boulders

Geologiska Foreningens i Stockholm Forhan- 1 987. .Middle and Late Ordovician conodont faunas and hiostra- of Oland. tigraphy of the Road River Group, northern Yukon Ter- dlingar, vol. 108, pp. 349-365. ritory. Canadian Journal of Earth Sciences, vol. 24, pp. 1988. Some aspects of life strategies of Early Palaeozoic rugose 643-653. corals. Lethaia, vol. 21, pp. 97-1 14. McCracken, A. D., and Nowlan, G. S. Nicholson, H. A. 1988. The Gamachian Stage and Fauna 13, pp. 7 1-79 ;« Land- 1875. Descriptions of the corals of the Silurian and Devonian ing, E. [ed.]. The Canadian Paleontology & Bioslraligraphy systet7is. Ohio Geological Survey, Report, vol. 2, part 2, Seminar. Proceedings ofMeeting, September 26-29, 1986. pp. 181-242. New York State Museum, Bulletin No. 462, 147 pp. Nicholson, H. A., and Lydekker, R. Students. 3rd McLean, R. A. 1889. A Manual of Palaeontology for the Use of 1-885, 1974. The rugose coral genera Streptelasma Hall. Grewingkia Edition. William Blackwood and Sons, vol. 1, pp. Dyhowski and Calostylis Lindstrom from the Lower Si- vol. 2. pp. 886-1624. lurian of New South Wales. Linnean Society of New South Nicoll. R. S., and Rexroad, C. B. paleontology the Salamonie Wales, Proceedings, vol. 99, pp. 36-53. 1968. Stratigraphy and conodont of Dolomite and Lee Creek Member of the Brassfield Litne- 1977. Early Silurian (Late Llandovery) rugose corals from west- stone (Silurian) in southeastern Indiana and adjacent Ken- ern North Greenland. Gronlands Geologiske Underso- tucky. Indiana Geological Survey. Bulletin 40, 73 pp. gelse. Bulletin, No. 121, 46 pp. Peel, J. S. Mikulic. D. G. 1977. Relationship and internal structure ofa new Pilina (Mono- 1 979. [MS] The Paleoecology ofSilurian Trilobites with a Section placophora) from the Late Ordovician ofOklahoma. Jour- on the Silurian Stratigraphy of Southeastern Wisconsin. nal of Paleontology, vol. 51, pp. 1 16-122. Oregon State University, Corvallis, Oregon, Ph.D. disser- Petryk, A. A. tation, 864 pp. 1981a. Stratigraphy, sedimentology and paleogeography of the Mikulic, D. G.. and Kluessendorf, J. Upper Ordovician-Lower Silurian of,4nticosti Island, Que-

1 983. The Oolitic Neda Iron Ore (Upper Ordovician?) ofEastern bec, pp. 1 1-39 in Lesperance, P. J. [ed.]. Field .Meeting, Wisconsin. Wisconsin Geological and Natural History Anticosti-Gaspe. Quebec, 1981, vol. 2. Stratigraphy and Survey, 54 pp. Paleontology. Departement de geologic. Universite de D. R. Mikulic, D. G., Sargent, M. L., Norby, R. D.. and Kolata, Montreal, 321 pp. valley, north- 1985. Silurian geology of the Des Flames River 1981b. Upper Ordovician glaciation: effects ofeustaticfluctuations eastern Illinois. Illinois State Geological Survey, Guide- on the .inticosti platform succession. Quebec, pp. 81-85 in

book 17, 56 pp. Lesperance, P. J. [ed.]. Field Meeting, .inticosti-Gaspe. Milici, R. C, and Wedow, H., Jr. Quebec, 1981, vol. 2, Stratigraphy and Paleontology. De- 1977. Upper Ordovician and Silurian stratigraphy m Sequatchie partement de geologic. Universite de Montreal, 321 pp. I'alley and parts ofadjacent I'alley and Ridge. Tennessee. Pollock, C. A., Rexroad, C. B., and Nicoll, R. S. United States Geological Survey, Professional Paper 996, 1970. Lower Silurian conodonts from northern Michigan and 38 pp. Ontario. Journal of Paleontology, vol. 44, pp. 743-764. Neuman, B. E. E. Pryor, W. A., and Ross, C. A. 1969. Upper Ordovician streptelasmatid corals from Scandina- 1962. Geology of the Illinois parts of the Cairo, La Center, and via. University of Uppsala, Geological Institutions, Bul- Thebes quadrangles. Illinois State Geological Survey, Cir-

letin, new ser., vol. 1, pp. 1-73. cular 332, 39 pp. 60 Bulletin 333

Reeds, C. A. 1913b. Stratigraphy and paleontology of the .-ilexandrian Series 1911. The Hunton Formation of Oklahoma. American Journal in Illinois and Missouri: Part I. Illinois State Geological of Science, ser. 4, vol. 32, pp. 256-268. Survey, Extract from Bulletin No. 23, 124 pp. Rexroad, C. B. 1914. The relations ofthe .ilexandrian Series in Illinois and Mis- 1967. Stratigraphy and conodont paleontology of the Brassfield souri to the Silurian .'section of Iowa. American Journal of (Silurianl in the Cincinnati Arch area. Indiana Geological Science, ser. 4, vol. 38, pp. 28-37.

Survey. Bulletin .16, 64 pp. 1916. .Alexandrian rocks ofnorlheaslern Illinois and eastern W 'is- Rexroad, C. B., and Droste, J. B. consm. Geological Society of America. Bulletin, vol. 27, 1982. Stratigraphy and conodont paleontology ofthe Se.xlon Creek pp. 305-324. Limestone and the Salamonie Dolomite (Silurian) in 1917. Stratigraphy and paleontology of the .Alexandrian Series

northwestern Indiana. Indiana Geological Survey, Special m Illinois and .Missouri: Part I. Illinois State Geological Report 25. 29 pp. Survey, Bulletin No. 23, Biennial Repori for 1911 and Risk, M. J., Pagani, S. E., and Elias, R. J. 1912, pp. 67-160. 1987. .Another internal clock: preliminary estimates of growth 1926. Silurian rocks of Illinois. Geological Society of America, rates based on cycles of algal boring activity. Palaios, vol. Bulletin, vol. 37, pp. 513-533.

2. pp. 323-331. Savage, T. E., and Ross, C. S. Roemer, C. F. 1916. The age of the iron ore in eastern Misconsm American 1861. Die fossile Fauna der silurischen Diluvial-Geschiebe von Journal of Science, ser. 4, vol. 41, pp. 187-193. Sadewitz hei Oels in Nieder-Schlesien. R. Nischkowsky, Scheffen, W. 81 pp. 1933. Die Zoanlhana Rugosa des Silurs auf Rmgerike im Os- Rose, J. N. logehiel. Norske Videnskaps-Akademi, Oslo, Matematisk- 1967. The fossils and rocks of eastern Iowa. Iowa Geological naturvidenskapelig Klasse. Schrifter, vol. 2, No. 5, 64 pp. Survey, Educational Series, Publication 1, 147 pp. Sheehan. P. M. Ross, C. A. 1988. Late Ordovician events and the terminal Ordovician ex-

1962. Early Llandoverian (Silurian) graptolites from the Edge- tinction, pp. 405-4 1 5 in Wolberg, D. L. [compiler]. Con- wood Formation, northeastern Illinois. Journal of Paleon- tributions to Paleozoic paleontology and stratigraphy in tology, vol. 36, pp. 1383-1386. honor ofRousseau H. Flower. New Mexico Bureau of Mines 1964. Early Silurian graptolites from the Edgewood Formation and Mineral Resources, Memoir 44, 415 pp.

of Iowa. Journal of Paleontology, vol. 38, pp. 1 107-1 108. Sweet, W. C, and Bergstrom, S. M. Rowley, R. R. 1976. Conodont hiostraligraphy of the Middle and Upper Or- 1904. The Echinodermata of the Missouri Silurian and a new dovician of the United States midcontinent. pp. 121-151 brachiopod. American Geologist, vol. 34, pp. 269-282. in Bassett, M. G. [ed.]. The Ordovician System: Proceed- Bir- 1 908. The geology of Pike County. Missouri Bureau of Geology ings of a Palaeontological .Association Symposium. and Mines, ser. 2, vol. 8, 122 pp. mingham. September 1974. University of Wales and Na- 1916. The Edgewood Limestone ofPike County. Missouri. Amer- tional Museum of Wales, 696 pp. ican Journal of Science, ser. 4, vol. 41, pp. 317-320. Templeton, J. S., and Willman, H. B. Rubey, W. W. 1963. Champlainian Series (Middle Ordovician) in Illinois. Il- 1952. Geology and mineral resources of the Hardin and Brussels linois State Geological Survey, Bulletin 89, 260 pp. quadrangles. United States Geological Survey. Profes- Thompson, T. L., and Satterfield, I, R. sional Paper 218. 179 pp. 1975. Stratigraphy and conodont biostratigraphy of strata con- eastern Sanerfield, I. R. tiguous to the Ordovician-Silurian boundary in 1971. Conodont s and stratigraphy of the Girardeau Limestone Missouri. Missouri Geological Survey, Report of Inves- (Ordovician) of southeast .Missouri and southwest Illinois. tigations No. 57, Studies in Stratigraphy, Pari 2, pp. 61- Journal of Paleontology, vol. 45, pp. 265-273. 108. Savage, T. E. Ulrich, E. O.. and Cooper, G. A. 1936. New .Silurian brachiopods ofthe Family Tnplesiidae. Jour- 1906. Geology ofJackson County. Iowa Geological Survey, vol. nal of Paleontology, vol. 331-347. 16, Annual Report (1905), pp. 563-648. 10, pp. Walliser, O. H. 1908a. On the lower Paleozoic stratigraphy of southwestern Illi- 1964. Conodonlen des Silurs. Hessischen Landesamtes fur Bo- nois. American Journal of Science, ser. 4, vol. 25, pp. 43 1- denforschung, Abhandlungen, vol. 41, 106 pp. 443. Wang, H. C. 1908b. Lower Paleozoic stratigraphy of southwestern Illinois. Il- 1947. New material ofSilurian rugose coralsfrom Yunnan. Geo- linois State Geological Survey, Bulletin No. 8. Year-Book logical Society of China, Bulletin, vol. 27, pp. 171-188. for 1907, pp. 103-116. Wedekind, R. 1909. Ordovician and Silurian formations in Alexander The 1927. Die Zoantharia Rugosa von Gotland (besonders Nordgot- County. Illinois. American Journal of Science, ser. 4, vol. land): Nebsl Bemerkungen zur Bioslratigraphie des Got- 28, 509-519. pp. landium. Sveriges Gcologiska Undcrsokning, ser. Ca, No. correlation the pre- De- 1910. The faunal succession and the of 19, 94 pp. vonian formations of southern Illinois. Illinois State Geo- Weller, J. M. logical Survey, Bulletin No. 16, Year-Book for 1909, pp. 1 940. Explanation and slratigraphic summary, pp. 1 -26 in Well- 302-341. er, J. M., and Ekblaw, G. E., Preliminary geologic map of 1912. The Channahon and Essex limestones m Illinois. Illinois parts ofthe Alio Pass. Jonesboro. and Thebes quadrangles. Academy of Science, Transactions, vol. 4, pp. 97-103. Union. Alexander, and Jackson Counties. Illinios State 1913a. Alexandrian Series in Missouri and Illinois. Geological Geological Survey, Report of Investigations. No. 70, 26 Society of America, Bulletin, vol. 24, pp. 351-376. pp. Ordovician-Silurian Rugose Corals: Mc Auley and Elias 61

Wcycr, D. E., Buschbach. T. C, C'ollinson, C, Frye, J. C, Hopkins,

197.1. Ohcrden Vrsprung der Calostylidae Zittel 1879 (Anthozoa M. E., Lineback, J. A., and Simon, J. A., Handbook of Rufiosa. Ordoviz-Silur). Freiberger Forschungshefte, vol. Illinois stratigraphy. Illinois State Geological Survey, Bul- C282. pp. 23-87. letin 95, 261 pp. 1974. /j/r /ic/in/«;.5 von Rhcgmaphyllum Wedekind. 1927 (An- Willman, H. B., and Buschbach, T. C. thi'zoa. Rugosa: baltoskandisches Silur). Zeitschrift fur 1975. Ordovician System, pp. 47-87 m Willman, H. B., Ather- Geologische Wissenschaften, Berlin, vol. 2, pp. 157-183. ton, E., Buschbach, T. C, C'ollinson, C., Frye, J. C Hop- Whitlow, J. W., and Brown, C. E. kins, M. E., Lineback, J. A., and Simon, J. A., Handbook 1963. The Ordovician-Silurian contact in Dubuque County. Iowa. of Illinois stratigraphy. Illinois State Geological Survey, United Slates Geological Survey, Professional Paper 475-(', Bulletin 95, 261 pp. pp. 11-13. Wilson, A. E. Williams, A. 1926. .4/1 Upper Ordovician fauna from the Rocky Mountains, 1951. Llandovery brachiopods from H 'ales with special reference British Columbia. Canada Department of Mines, Museum to the Llandovery district. Geological Society of London, Bulletin No. 44, Cieological Series No. 46, Contributions Quarterly Journal, vol. 107, pp. 85-136. to Canadian Palaeontology, pp. 1-34, 100-1 15. Willman, H. B. Winchell, N. H., and Schuchert, C".

1 962. The Silurian strata of northeastern Illinois, pp. 6 1-67 and 1895. Sponges, graptolites, and corals from the Lower Silurian Description of stops, second day. pp. 81-96 in Silurian of Minnesota. Chapter 3. pp. 55-95 in The Geology of

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PLATES

Exterior views are of specimens coated with ammonium chloride. Transverse and longitudinal sections are negative prints prepared using thin sections as negatives in a photographic enlarger. Transverse and longitudinal photomicrographs of thin sections are positive prints. Transverse prints are oriented as they appear looking down from the calice toward the apex of the corallum, with the cardinal side facing the bottom of the page unless otherwise indicated. Longitudinal prints are oriented with the calical end facing the top of the page. 62 Bulletin 333

Explanation of Plate 1

Figure Page

1-19. Streptelasma subregulare (Savage, 1 9 1 3b) 34

[1-3, Ideal Quarn' Mbr., Keel Fm., Sec. 21 (Rock Crossing); 4, 5, Keel Fm., Sec. 25 (Hunton); 6-9, Brevilamnulella beds. Keel Fm.. Sec. 23 (Lawrence Quarry); 10, Keel Fm., Sec. 23 (Lawrence Quarry); 11, 12, Leemon Fm., Sec. 31 (Thebes North); 13- 16, Leemon Fm., Sec. 20 (Short Farm); 17-19, Leemon Fm., Sec. 19 (New Wells).]

1. transverse section, x 3.

transverse sections, x 3.

transverse sections, x 3. transverse section, x3. transverse sections, x3.

transverse sections, x 3.

transverse section, x 3.

exterior view, cardinal side unknown, x 3. transverse sections, x3; arrow in figure 18 points to Trypanites sp. in matrix and corallum. Plate 1 Bulletins of Americ an Paleontology, Volume 98

JH 18 ^ Plate 2 Bulletins of American Paleontology. Volume 98 ORDOViriAN-SlI.tJRIAN RUGOSE CORALS: McAuLEY AND ELIAS 63

Explanation of Plate 2

Figure 1-12. Streptelasma subregulare (Savage. 1913b)

[1-4. Lecmon Fm.. Sec. 19 (New Wells); 5, unnamed mbr.. Bryant Knob Fm., Sec. 18 (Kissenger); 6-12, Kissenger Lst. Mbr.. Bryant Knob Fm., Sec. 18 (Kissenger).]

1-4. USNM 423018; 1-3, transverse sections, >: 3; arrows in figure 3 point to epizoic bryozoans on corallum; 4, transverse

photomicrograph showing microborings in outer wall of corallum, x 100 (position of fig. 4 shown by small numeral at

upper left of fig. 3).

5. USNM 423105; transverse section, x 3.

6. USNM 423123; transverse section of corallum in matrix, showing algal coating around corallum, x 3.

7-12. USNM 423140; 7-9, longitudinal sections, cardinal side on left, x3; 10-12, transverse sections, x3 (positions of figs.

10-12 shown by small numerals beside figs. 7-9). 64 Bulletin 333

Explanation of Plate 3

Figure 1-18. Streptelasma subregulare (Savage. 1913b) [I. Kisscngcr Lsl. Mbr.. Bnant Knob Fm.. Sec. 18 (Kissenger); 2-9. Kissenger Lst. Mbr.. Bryant Knob Fm., Sec. 17 (ClarksviUe);

10, unnamed mbr.. Br\ant Knob Fm., Sec. 16 (Clinton Spring); 1 1-18, Kissenger Lst. Mbr., Bryant Knob Fm., Sec. 16 (Clinton Spring).)

1. USNM 423141; transverse photomicrograph of wall and septa, x 20 (counter side of corallum near left alar septum). 2-4. USNM 423156; longitudmal sections, cardinal side on left, x3.

5-9. USNM 423152; 5. 6. longitudinal sections, cardinal side on left, x 3; 7-9, transverse sections, x3 (positions of figs. 7

and 9 shown by small numerals beside figs. 5 and 6). 10. UCGM 45643; transverse section, x3. 11-13. USNM 423216; transverse sections, x 3. 14-18. USNM 423192; 14, 15, longitudinal sections of corallum in matrix, showing algal coating on corallum wall and in calice

(left side), cardinal side unknown, x 3; arrow in figure 1 5 points to epizoic bryozoan on algal coating above calice rim; 16-18. transverse sections of corallum in matrix, showing algal coating around corallum, cardinal side unknown, x3;

two arrows in figure 16 point to transverse section of Dimorphosiphon sp. (positions of figs. 17 and 18 shown by small

numerals beside figs. 14 and 15). Bulletins of American Paleontology, Volume 98 Plate 3

V-^- •'•;, ^. . :v>-'^ 16 y/^- -

'^-i^ljl^i- 12

^.:^Tr:,.^:^!<=:^>i8 Bulletins of American Paleontology. Volume 98 Plate 4 Ordovkian-Smurian Rugose Corals: McAuley and Elias 65

Explanation of Plate 4

Figure Page

1-13. Streptelasma subregulare (Savage, 1 9 1 3b) 34 [1,2, Kissenger Lst. Mbr.. Bryant Knob Fm., Sec. 16 (Clinton Spring); 3, Kissenger Lst. Mbr., Bryant Kjiob Fm., Sec. 15 (Calumet), 4-7, Kissenger Lst. Mbr.. Bryant Knob Fm., Sec. 14 (Higginbotham Farm); 8, 9, Cyrene Fm., Sec. 13 (Bowling Green); 10-13, Wilhelmi Fm., southeast of Channahon.]

1. USNM 423192; transverse photomicrograph showing microborings in corallum beneath micritized exterior and algal coating (at top) and micritized interior of calice (at bottom), x32 (position of section shown in PI. 3, fig. 18). 2. USNM 423198; transverse photomicrograph showmg microborings in corallum beneath micritized exterior and algal coating (on right), x 32. 3. USNM 423246; transverse section, x 3. 4-6. USNM 423253; 4, exterior alar view, cardinal side on right, x 1; 5, 6, transverse sections, x3 (positions of figs. 5 and

6 shown by small numerals beside fig. 4). 7. USNM 423263; transverse section, x3. 8, 9. USNM 423282; transverse sections, x 3.

10-13. UI C-1581a; 10, exterior cardinal view, xl; 1 1-1 3, transverse sections, x 3 (positions of figs. 1 1-13 shown by small

numerals beside fig. 10). 66 Bulletin 333

Explanation of Plate 5

Figure Page l-IO. Streplelasma subregulare (Savage, 1913b) 34

(I. Wilhelmi Fm.. southeast of Channahon; 2-5. Wilhelmi Fm.. Channahon; 6, Schweizer Mbr.. Wilhelmi Fm., Sec. 4 (Schweizer

West); 7. 8. Birds Mbr.. Wilhelmi Fm.. Sec. 34 (Belvidere South); 9, 10, Mosalem Fm., Sec. 32 (Thomson East).]

1. UI C- 158 la; transverse photomicrograph of wall and septa, x 20 (position of section shown in PI. 4, fig. 12).

2-5. UI C- 1 560a: 2, exterior cardinal view, x 1; 3-5, transverse sections, x3 (positions of figs. 3-5 shown by small numerals

beside fig, 2), 6. USNM 423290; transverse section. x3. 7.8. USNM 431 140; transverse sections. x3. 9, 10. USNM 431 168; transverse sections. ^3. 11, 12. Streptelasma species cf S. subregulare (Savage. 1913b) 42 [II. 12. Cason sh.. Sec. 33 (Buffalo River).] II. 12. USNM 423307; transverse sections, orientation uncertain. x4.

1 3-22. Streptelasma amsdeni. new species 43 (13-16, lower oolitic unit. Keel Fm., Sec. 24 (Coal Creek); 17-22. middle laminated calcilutite unit. Keel Fm.. Sec. 24 (Coal Creek).] 13-16. USNM 423309 (paratype); 13. longitudinal section, cardinal side on right, x3; arrows point to ooid enclosed in

intertabular chamber (refer to Elias, 1984a, pp. 105. 107, 108, I 13. 1 14); 14-16, transverse sections, x3 (position of

fig. 16 shown by small numeral beside fig. 13). 17. 18. USNM 423315 (paratype); transverse sections, x6. 19,20. USNM 423310 (paratype); transverse sections, x6. 21. 22. USNM 423314 (paratype); transverse sections, x3. Bulletins of Amf.rkan Paleontology, Volume 98 Plate 5 Bulletins of American Paleontology. Volume 98 Plate 6 OrDOVK'IAN-SII.I IRIAN RUGOSE CORALS: M( AuLEY AN[) Elias 67

Explanation of Plate 6

Figure P^&e 1-11. Streptelasma amsdeni. new species 43 [1-11, middle laminated calcilutite unit. Keel Fm., Sec. 24 (Coal Creek).] x 5-8, 1-8. USNM 423308 (holotype); 1. exterior counter view, x 1; 2-4, longitudinal sections, cardinal side on right, 3; transverse sections, x3 (positions of figs. 2-8 shown by small numerals beside lig. 1). x 9. USNM 423377; transverse section of coralla in matrix, perpendicular to bedding, top of bed faces top of page, |.5. x 10. USNM 423318 (on left), 423319 (middle), 423320 (on right); exterior view of coralla on bedding surface, 1. x 1 1. USNM 423321; exterior view, cardinal side unknown, 1. 68 Bulletin 333

Explanation of Plate 7

Figure Page 1-14. Streptelasma leemonense Elias, 1982a 45

[1-4, Keel Fm., Sec. 23 (Lawrence Quarry); 5, Cason sh.. Sec. 33 (Buffalo River); 6. Leemon Fm., Sec. 31 (Thebes North); 7, Leemon Fm.. Gale Sec; 8-13. Leemon Fm., Sec. 20 (Short Farm); 14, Kissenger Lst. Mbr., Bryant Knob Fm., Sec. 14 (Higginbotham Farm).] x x 1-3. USNM 423387; 1 , exterior cardinal view, 1; 2, longitudinal section, cardinal side on right, 4; 3, transverse section,

x4 (positions of figs. 2 and 3 shown by small numerals beside fig. 1). 4. USNM 423382; transverse section, x4. 5. USNM 423394; transverse section, x4. 6. USNM 423396; transverse section, x4. 7. UI C- 1448a; transverse section, x4.

8-10. USNM 423397; 8, longitudinal section, cardinal side on left, x4; 9, 10, transverse sections, x4; arrow in figure 9 points

to small offset or epi/oic individual (positions of figs. 9 and 10 shown by small numerals beside fig. 8). 11-13. USNM 423399; transverse sections, x 4. 14. USNM 423405; transverse section, x4. Bulletins of American Paleontology, Volume 98 Plate 7

^^'11 Bulletins of American Paleontology. Volume 98 Plate ORDOVKIAN-Sll.t IRIAN RUGOSE CORALS: McAULEY AND ElIAS 69

Explanation of Plate 8

Page Figure 45 1 -4. Streptelasma leemonense Elias. 1 982a [1-4, Leemon Fm., Sec. 20 (Short Farm).] (a, x4; arrows m figures 1 and 4 point 1-4. USNM 423401; transverse sections of coralla in matrix, showing two offsets b), in figure 3 point to transverse sections of Di to epizoic bryozoans on coralla; two arrows in figure 2 and arrow morphosiphon sp. 70 Bulletin 333

Explanation of Plate 9

Figure Page

1.2. Sireplelasma leemonense Elias. 1 982a 45 [1,2. Leemon Fm.. Sec. 20 (Short Farm).]

1, 2. USNM 423401; 1. transverse photomicrograph of wall and septa where wall is ver>- thick, x20 (position of section

shown in PI. 8. fig. 3); 2. transverse photomicrograph of wall and septa where wall is of normal thickness, x20 (same

corallum as in fig. 1, but section is on opposite side and slightly closer to apex).

3-7. Streptelasma species cf S. leemonense Elias, 1 982a 47 (3-7, Keel Fm., Sec. 23 (Lawrence Quarr>).]

3-5. USNM 423408; 3, longitudinal section, cardinal side unknown, x 4; 4, 5, transverse sections. x4 (position of fig. 4

shown by small numeral beside fig. 3). 6. USNM 423409; transverse section. x6. 7. USNM 423410; transverse section, x4. 8. 9. Streptelasma species A 47

[8, 9, Noi,x Lst.. Sec. 15 (Calumet).]

8, 9. USNM 42341 1; transverse sections of corallum on host bryozoan in matrix, cardinal side unknown, x 12, Bulletins of American Paleontology, Volume 98 Plate 9 Bulletins of American Paleontology. Volume 98 Plate 10

» .^:.a^ !_** ^Sad

:^:^y- :•«•.

-•^ mtrr---r Ordovician-Silurian Rugose Corals: McAuley and Elias 71

Explanation of Plate 10

Figure Page 1-5. Streptelasma species A 47 [Noix Lst., Sec. 15 (Calumet).] x 1, 2. USNM 423412; transverse sections of corallum on host bryozoan in matrix, cardinal side unknown, 12. 3-5. USNM 423413; transverse sections of corallum on host bryozoan in matrix, cardinal side unknown, x 12. 6-10. Grewingkia species A 48

[6, Keel Fm., Sec. 23 (Lawrence Quarry); 7-10. Kissenger Lst. Mbr., Bryant Knob Fm., Sec. 14 (Higginbotham Farm).] 6. USNM 423414; transverse section, x4. 7-10. USNM 423415; transverse sections, x4. 1

72 Bulletin 333

Explanation of Plate 1

Figure Page 1-1 2 Keelophyllum oklahomense. new genus, new species 52 (1-5. Keel Fm.. Sec. 25 (Hunton); 6-12. Keel Fm.. Sec. 23 (Lawrence Quarr\').]

1-5. USNM 423417 (paratype); 1. 2. transverse sections. ' 4; 3. transverse photomicrograph of wall and septa, x 20 (position

of fig. 3 shown by small numeral beside fig. 2); 4. 5. longitudmal photomicrographs of wall at position of counter septum

(4) and cardinal septum (5), x20.

6-12. USNM 423416 (holotype); 6, exterior cardinal view, x i; 7-9, longitudinal alar-alar sections, x4; 10-12, transverse

sections, x6. x4. x4 (positions of figs. 7-12 shown by small numerals beside fig. 6). IJlIIXETINS OF AmF.RICAN PALEONTOLOGY, VOLUME 98 Plate 1 I Bulletins of American Paleontology, Volume 98 Plate 12 2

Ordovician-Sii.urian Rugose Corals: McAuley and Elias 73

Explanation of Plate 1

Figure P^g^ 1-6. Keelophyllum oklahomense, new genus, new species 52 [1-6, Keel Fm., Sec. 23 (Lawrence Quarry).] x4. 1. USNM 423418 (paratype); longitudinal section, cardinal side unknown, 2,3, USNM 423419 (paratype); transverse sections, x4. 4-6. USNM 423421 (paratype); transverse sections showing corallum attached to very thin encrusting epizoan and host halysitid corallum in matrix in figure 4, and small (possibly epizoic) individuals in figures 5 and 6, x 6, x 4, x 4; arrows in figure 6 point to epizoans on corallum. 7-11. Rhegmaphyllum species 49

[7-1 1, Cason oolite, St. Clair Spring Sec] 7-9. USNM 423422; transverse sections, x 6; arrows in figure 7 point to fisur grains of sediment to which corallum is attached.

10, 11. USNM 423423; transverse sections, x6; arrows in figure 1 1 point to three small, epizoic individuals on host corallum in matrix. 3

74 Bulletin 333

Explanation of Plate 1

Figure Page

I -9. Rhegmaphyllum species 49

[1^. 1st. facies at base of Bowling Green Dol., Sec. 17 (Clarksville); 5 1st. facies within Bowling Green Del., Sec. 17 (Clarksville);

6, 7, Elwood Fm., Sec. 5 (Schweizer North); 8, 9. Mosalem Fm.. Sec. 32 (Thomson East).] 1.2. USNM 423424; transverse sections, ^6. 3. 4. USNM 423425; transverse sections. x6. 5. USNM 423426; transverse section, x6. 6. USNM 423427; exterior lateral view, mold of calice, x6. 7. USNM 423428; transverse section. x6. 8, 9. USNM 423429; transverse sections, x 6. 10-16. Dinophyllum species 49

[10-13, 1st. facies at base of Bowling Green Del., Sec. 1 7 (Clarksville); 14, Bowling Green Dol., Sec. 1 7 (Clarksville); 15, Elwood Fm.. Sec. 5 (Schweizer North); 16. Mosalem Fm., Sec. 32 (Thomson East).] 10-13. USNM 423430; 10, 11, longitudinal sections, cardinal side on right, x4; 12, 13, transverse sections, x4 (positions of

figs. 12 and 13 shown by small numerals beside figs. 10 and 1 1). 14. USNM 423431; transverse section, x4. 15. USNM 423432; transverse section, x4. 16. USNM 423433; transverse section, x4. Bulletins of Amlkkan Paleontology, Volume 98 Plate 13

o*'''A.v ^< n »>il»* 2 '3 Plate 14 Bulletins of American Paleontology. Volume 98 4 1

Ordovician-Silurian Rugose Corals: McAuley and Elias 75

Explanation of Plate 1

Figure Page -8 1 . Dalmanophyllum species 50

[1, Sexton Creek Lst.. Sec. 20 (Short Farm); 2, 3, 1st. facies at base of Bowling Green Do!., Sec. 17 (Clarksville); 4, 5, Bowling Green Dol.. Sec. 17 (Clarksville); 6, Elwood Fm., Sec. 6 (Plaines West); 7, Mosalem Fm., Sec. 32 (Thomson East); 8, Mosalem Fm., Sec. 10 (Lost Mound).]

1. UCGM 45639; transverse section, x5, 2,3. USNM 423434; transverse sections, x5.

4, 5. USNM 423435; 4, longitudinal section, cardinal side on right, x 5; 5, transverse section, x 5 (position of fig. 5 shown

by small numeral beside fig. 4). 6. USNM 423436; transverse section, x5. 7. USNM 423437; transverse section, x5. 8. USNM 423438; transverse section, x5. 9-14. Cyathactis? species 51

[9, Cochrane Fm., Sec. 23 (Lawrence Quarry); 10-12, Bowling Green Dol., Sec. 17 (Clarksville); 13, Elwood Fm., Sec. 29 (Sears Pit); 14, Mosalem Fm., Sec. 9 (Winston).] 9. USNM 423439; transverse section, x4.

10-12. USNM 423440; 10, longitudinal section, cardinal side on left, x4; 1 1, |2, transverse sections, x4 (positions of figs. 1

and 12 shown by small numerals beside fig. 10). 13. USNM 423441; transverse section, x4. 14. USNM 423442; transverse section, x4. 76 Bulletin 333

INDEX

Note: Page numbers are in light face; plate numbers are in bold face type; pages on which principal discussions occur are in italics; F and B indicate foldouts inside the front and back covers, respectively.

A coll 33.43 Berry and Boucot (1970) 12,17,21,25,26 affine. Slreptelasma 41,42 Berry and Boucot (1973) 6 Ahloso, Oklahoma Quadrangle 53 Berry and Marshall (1971) 16 Alabama 7 Bighornia pate/la {Wihon, 1926) 23 Birmingham 24 Bighornia-Thaerodonta Assemblage Zone 24 alata. Triplesia 9,10,26 Billings (1862) 5,20,23,27 Alexandrian Series 6,16,26 Billings (1865) 24,41 ambigua. Zaphrenlis 20,34.35,38 Birkhead (1967) 14,15.54

Amoco Canada Petroleum Company Limited, Calgary, Alberta .... Blackstone River section 8 7 Blake. D. B 7

Amorphognalhus ordovicicus Branson and Mehl. I9i3 .. 12,16,17 Blanding Formation 21,22,26,8 A morphognathus ordovicicus Zone 9 Boda Limestone 41.49 Amsden (1957) 7,8,53 Bodophylhini Neuman. 1969 50,51 Amsden (1960) 7-9,53 shorti Ehas. 1982a 5,11,24,29,48,50,51,8 Amsden (1961) 53 Bolton (1981) 41 Amsden (1966) 12 Bolton and Nowlan (1979) 17,26 Amsden (1967) 7,8 Bonfield, Illinois Quadrangle 54 Amsden (1971a) 9,10,26 Borelasma Neuman, 1969 34 Amsden (1971b) 6,8,11,12,14,17,25 cornicum He. 1978 42 Amsden (1974) 6-8,11,12,14,15,17,18,25,26,53,54 crassitangens Neuman. 1969 25.42 Amsden (1980) 8,25 sinensis He, 1978 42 Amsden (1983) 10 sp. a 42 Amsden (1986) 6,8-12,14,15,17,24-27,53-55 sp. b 42 Amsden (1988) 8,10.12,14.15 Bowling Green (Section 13) 13-15,17,18,35-42,5-/ Amsden and Rowland (1965) 8 Bowling Green Dolomite 5,12-18,26,29,49-51,54,8 Amsden. T. W 6.7.33,43 Bowling Green. Missouri Quadrangle 54 amsdeni, Slreptelasma 5,6 5,7,8,24,25, Brachyelasma 29-33,36,38,40,42,4i,44,45,B irregularis He. 1978 42 Anderson (1983) 55 lindstroemophylloides He. 1978 42 angmnea, Grewingkia 49 primum (VJedekind. 1927) 42 Annada, Missouri-Illinois Quadrangle 54 yentzekouense He. 1985 42 anthelion. Rectigreningkia 52 Brachyelasmal siinplotabulatum He. 1978 45 Arkansas 7 Brainard Shale 18-23,8 Batesville 9 Brandt, D. S 7 Buffalo River 53 Branson and Branson (1947) 8 Gilbert 9,10 Branson and Mehl (1933) 12,16,17 Independence Co 9,49,55 Brassfield Formation 23,28,49 Jasper 9 Brenchley (1984) 6 Marshall 9 Brenchley and Newall (1980) 27 north-central 6,9,25,43,49 Brenchley and Newall (1984) 6 eastern 5,24,27,49,55,8 Brevilamnulella beds 7-9,30.31.34,45 western 5,27,42,45,53,3 British Columbia, southeastern 24 Searcy Co 9,42,45,53 Bromley (1970) 31 St. Clair Spring F,6,9,55 Brower(1973) 11.12 Athy (1928) 18 Brown and Whitlow (1960) 21-23 altenuaium. Paramplexoides 45 Bryant Knob Formation 5,12-18.25,26,29,31,32,54,8

Ausich (1987) 14 Kissenger Limestone Member .... 5,13-18,29-32,35,45,48,54,8 unnamed member 5,13,16,30,35.8 Babb, D. R 7 Buffalo River (Section 33) 9,10,27,42,45,5J Baltic area 28 Buschbach (1964) 19

Baltoscandia 24,51 Buttler, C. J 6

Barrick (1986) 6,8-10,12,17,24-27,53,55 Buttler, Elias, and Norford ( 1 988) 24

Barrick and Klapper ( 1 976) 9 Sassier (1950) 48 Ccoll 33,42,45 Beaverfoot Formation 24 California, eastern KJamath Mountains 46,49 Becscie Formation 23 Calumet (Section 15) 13,30-32,35-42,45,47.5-/ Bellevue (Section 26) 21,22,54 canadensis. Grewingkia 5,20,23,24,27 Belviderc South (Section 34) 7,18,20,21,35-42,5-/ Canadian Society of Petroleum Geologists 6 Belvidcrc South, Illinois Quadrangle 54 Cape Girardeau NE, Missouri Quadrangle 53 Ordovician-Sii.urian Rugose Corals: McAuley and Elias 77

Cape Schuchert Formation 53 Dimorphosiphon sp 8,11,14 Cason Dinophvllum UndsWom, 1882 34,49,50 "Brassficld" limestone 9,10,B sp 13 5,13,15,16,19,20,22-24,28,49,50,8 dolomitic shale 25 dislincturn (cf), Streptelasma 42 limestone 10 Distomodus elements 8 oolite 5,9,10,24,25,27,49,8 Distomodus kentuckyensis Conodont Zone 10,12,17,21 shale 5,9,10,42,45,8 District of Keewatin 17 strata 9 divaricans. Streptelasma 34,48 Cedar Village (Section 22) 8,5i Drahovzal and Neathery (1971) 24 celloni. Ncospathognalhodus 17 Drakes Formation. Channahon Limestone 18,20,36 Bardstown Member 48 Channahon, Illinois Quadrangle 54 Preachersville Member 48 channalwnensis. Zaphrentis 35,38 Rowland Member 48 Chimneyhill Limestone, oolitic member 8 Saluda Dolomite Member 48 China 24 Dybowski (1873) 34,48,49,51.52 Guizhou Province 5,24,42,45 dyscritus, Paltodus 17 Cincinnati Arch region 23,27,28,48 Cincinnatian Series 26 El coll 33,35.45,50 Clarksville (Section 17) 13,15,16,18,30-32,35-42,49-51,54 E2coll 33,35 Clarksville, Missouri-Illinois Quadrangle 54 Eastern Michigan University, Ypsilanti, Michigan 7 Climacograptus putillus (HaW, 1865) 12 eccentricum, Streptelasma 46,47 Clinton Spring (Section 16) 13-15,18,30-32,35-42,54 Edgewood Coal Creek (Section 24) 7-9,3 l,32,36,38,40,42,43,5i assemblage 5,6,23-27,29,33,8 Coates(1984) 33 Formation 12,18,19,21,25,27,36,45

Cochrane Formation 5,7-9,26,51,8 Cyrene Member 1 1,14 Cocks (1985) 9,17 Group 12.14.17 Cocks and Copper(1981) 25 Limestone 14,22,23 Colbath (1986) 24 sequence 18 contexta, Grewingkia 49 Solitary Rugose Coral Province F,5,6,24,27-30,32.53 Cooper (1975) 12,21 strata 16 cooperi, Lepidocyclus 10 zone 11,12,14.17 corniculum, Streptelasma 34,41 Elias (1979) 6 cornicum. Borelasma 42 Elias (1981) 5,12,22,23,27,28,32,49 Cornulites zone 22,23 Elias (1982a) 5,6,8,10-12,15,20,22-34,36,38,41,45-52,54 costulatus. Decoriconus 8 Elias (1982b) 31 Cole, Reinertsen, and Killey (1968) 53 Elias (1983a) 28 Craig (1969) 6,9,10,25,27 Elias (1983b) 32,48 Craig (1975a) 9 Elias (1984a) 44 Craig (1975b) 9,10,25,27,55 Elias (1984b) 29,44,46 Craig (1984) 9,53.55 Elias (1985) 12,22,23,27,28,32,48 Craig, Ethington, and Repetski (1986) 9,10,25.27,55 Elias (1986a) 51-53 Craig, Wise, and McFarland (1984) 9,10,55 Elias (1986b) 30,31 Craig, W. W 6,7,33 Elias (1987) 23 Crassilasma polytabulatum He, 1985 42 Elias, McAuley, and Mattison (1987) 9,18,31 crassilangens. Borelasma 25,42 Elias, Nowlan, and Bolton (1988) 27 cuneala, Grewingkia 53 Elias and Potter (1984) 46,49 curvatus. WalHserodus 8 Elias. Zeilstra. and Bayer (1988) 32 Cyathactis Soshkina in Ivanova, Soshkina, Astrova, and Ivanova. Elias, R. J 6,7,33 1955 51 Elizabeth, Illinois Quadrangle 55 Cyathactis"} %v 14 5.7.8.13.15,16,19.20,22-24,28,5;,B "Elkhom" strata 23 cylindricus, Paramplexoides 45 Ellis Bay Formation 24,27,41 Cyrene Formation 5,13-15,17,18,25.26.34-36,54 Elwood Formation 5,18-21,26,49.50,51,54,8 Cyrene. Missouri Quadrangle 54 EM coll 33-35,45,47-52 EMM coll 33-35,43.45,49-52 Dalmanitina Beds 5,24,41,42,45,46 EMZ coll 33-35,45,49,51 Dalmanophyllum Lang and Smith, 1939 50 Essex Limestone 18 sp 14 5,11-13,15.16.19,20,22-24.28,50,8 Esso Resources Canada, Calgary, Alberta 5 daytonensis, Rhegmaphyllum 49 Estonian S. S. R 41.51.52 Decker (1935) 9 etnaense. Streptelasma 46,47 Decorah Shale 48 EZcoll 33.35.49,50 Decoriconus costulatus (RexToad, 1967) 8 Department of Geological Sciences, University of Manitoba, Win- Faculty of Science, University of Manitoba, Winnipeg. nipeg. Manitoba 7 Manitoba 7 Dicellograptus complanatus Zone 9 Fauna Dicellograptus complanatus var. ornatus Zone 16 11 10 Dillsboro Formation 48 12 10 B

78 Bulletin 333

Femvale Limestone 9,10,B Alexander Co 1 1,12,34,45.53 Fisher (1925) 18 Barber Greene Road 54 Fisher (1954) 26 Belvidere 7.18-20,35,54 Jloweh, Neotryplasma 52 Boone Co 19,35,54 Foerste (1890) 17,49 Carroll Co 22,23.35,49,50,54 Foerste (1909) 17,21,26 Channahon 18-21,30,35 Fort Atkinson Limestone 18,23 Chicago 19 Cortland 54

Gale Section 1 l,12,36,45,5i Custer Park 18,19 Garden Praine (Section 3) 18-21,35, 37-41,5-^ De Kalb Co 19,35,51,54 Georgia 7 Des Plaines River 18,54 Pope Spring 24 Du Page River 18 Georgian Bay Formation Essex 18,19,35 upper member Gale 53 Kagawong bed 48 Horse Creek 18,20,35 Meaford bed 48 Jo Daviess Co 22,50,51.54,55 Girardeau Limestone 10-12, Johnson Creek 54 girardeauensis. Noixodontus 8,12,15,17 Joliet 19,20 Ginanella 30 Kankakee Co 19,35 Glenister(1957) 23 Kankakee River 54

Glyptograptus persculplus (?) Graptolite Zone 8 Kankakee River State Park 54 Golubic, Perkins, and Lukas (1975) 31 Lost Mound 54 Grahnand Bergstrom (1985) 27 McHenry Co 19,35,54 Green Island, lowa-Illinois Quadrangle 54 northeastern 5-7, 18-20,23, 25.26,35,49-5 1,54,B Greenland, northwestern 53 northern 5,20,27,32 CrfH7>i.?A/fl Dybowski. 1873 24,48,49 northwestern 5,6,21-23,25-27,35,49-51,54,8 anguinea (Scheffen. 1933) 49 Schapville 55 canadensis {Bi\hng%. 1862) 5,20,23,24.27 Savanna 22 coniexia Neuman. 1969 49 southern 5,6,10-12,25-27,35,45,53,8 cuneaia McLean, 1977 53 State Route 102 54 penobscoiensis EUas, 1982a 49 State Route 3 53 p«/c/re//a (Billings, 1865) 24 Sterling F,22 sp. A 10 5,7,8,13,15,24-26,29.32,';5,49,51,53,B Stockton 55

sp. cf. G. pulchella (Billings, 1865) 24 Stone Quarry Road 54 Guanyinqiao Beds 5.24,42.45 Thebes 53 Thomson 54 Hall (1847) 33,34,38,41 west-central 25 Hall (1865) 12 Will Co 19,35,49,50,54 Ham (1973) 53 Winston railroad tunnel 55 Hambrey (1985) 6 Illinois State Geological Survey, Champaign, Illinois 7 Hanover, Illinois Quadrangle 55 Indiana 23,48 Harden City, Oklahoma Quadrangle 53 insolitum, Slreptelasma 42 hassi. Ozarkodina 21 Interstate Route 35 53 Hawkins Limestone 8 Iowa 23,27 He (1978) 25,42,45 Bellevue State Park 55 He (1985) 25,42 Bellevue 22 Helicelasma Neuman, 1969 34 Clayton Co F,22 simplex Seuman. 1969 25,42 Dubuque 22,23

Higginbotham Farm (Section 14) .. 7,13,17,18,32,35-42,45,48,54 Dubuque Co 22,23,55 Hill (1981) 6,23,26.32,51 eastern 5,6,21-23,25,27,29,54,8 Hirnantia Jackson Co 22,55 community 25 King 55 fauna 25 irregularis. Brachyelasma 42 Himantian Stage 17 Ivanova et al. (1955) 51 Hoover, P. R 7 Ivanovskiy (1963) 34 Horseshoe Gulch unit 46,49 Howe (1966) 10 Jaanusson (1979) 25 Hunton (Section 25) 7,34,36-38,41, 52,5i Jenkins (1970) 9 Hunton Group 53 Johnson, Cocks, and Copper (1981) 27 Johnson, Rong, and Yang (1985) 26,29 Icriodella"^ sp 17 Icriodina irregularis Zone 12,21 Kaljo (1957) 51 Ideal Cement Company quarry 53 Kaljo(1961) 51 Ideal Quarry calcarenite 9 Kankakee Formation 17-21,26,54 Illmois 7.11,12.14,17,23,25-27 Drummond Member 54 Airport Road 54 Offerman Member 54 Ordovician-Silurian Rugose Corals: McAuley and Elias 79

Troutman Member 54 McAuley (1985) 6,32 Kankakee River (Section 7) 20,54 McAuley, Elias, and Mattison (1986) 6 Keel Formation 5,7-9,25-27,29-32,34,35,40,45-48,51-53,8 McAuley, R. J 6,7,33 Ideal Quarry Member 7-9,30,34,35,53 McCracken (1987) 8,25 laminated calcilutite unit 7,8,30-32,43 McCracken and Barnes (1981) 8,17,23 Keel oolite 8,9,32,43 McCracken and Barnes (1982) 14,17,18,25,54 Keel-Edgewood brachiopod assemblage 25,27 McCracken and Lenz (1987) 8,17 Keel-Edgewood oolitic deposits 27 McCracken and Nowlan (1988) 9,17,21.24 Keelophyllum. n. gen 5/, 52 McFarland, L. M 6

oklahomense.n.^p. .. 11,12. 5,7,8,24,29,30,36,48,51.52,53,8 McLean (1974) 33,34,50 Kent, Illinois Quadrangle 55 McLean (1977) 53 Kentucky 23,48,49 McLean, R. A 7 King (Section 8) 21,22,55 Menominee, Illinois-Iowa Quadrangle 55 Kissenger (Section 18) 13-16,30-32,35-42,5'^ Meyer, D. L 7

Knapp, C. J 6 Michigan 48 Koenig, Martin, and Collinson (1961) 54 Mikuhc (1979) 20 Kolata and Graese (1983) 20 Mikuhc and KJuessendorf (1983) 20 Kolataand Guensburg (1979) 11,12,53 Mikulic et al. (1985) 20,21,54 Krey (1924) 14 Milici and Wedow (1977) 24 Kuntz, W 7 Mmistere de I'Energie et des Ressources, Quebec, Quebec 7 Minnesota 48 Ladd (1929) 23 Mississippi River 12,14,53.54 Lake Michigan 19 Missouri F,7, 12, 14,26,27 Ungand Smith (1939) 50 Blue Shawnee Creek 54 Laswell(1957) 54 Bowling Green 13 Late Ordovician "continental margin" assemblage 5,23,24, Cape Girardeau 11

28,33 Cape Girardeau Co 1 1,12,35,45,50,53,54 Late Ordovician "epicontinental" assemblage 5,23,24,27 Clarksville 13,54 Laub(1975) 28 Clinton Spring 54 Laub(1979) 23,28,33,49-51 Cyrene 13 Lawrence Quarry (Section 23) eastern 16 7-9,30-32,34,36-41,45-48,51, 52,5i Edgewood 13-15,34,35 Lecompte(1952) 50 Kissenger Hill 54 Leemon Formation 5,10-12,25.29-32,34,35,38,45,50,53,8 Louisiana 7,13,17,54 leemonense. Streptelasma 7.8,9 5,7-13,15,24-27, New Wells 54 29-32,36,45,46,47,52,8 northeastern 5-7,12,13,16,25,26,29,35,45,47-51,54,8 leemonense {sp. ci.), Streptelasma ... 9... 5,7,8,24,30,36,46,47,8 Pike Co 13-16,34,35,45,47-51,54 Lemastus(1979) 9,10,53,55 southeastern 5,6,10,1 1,25,26,35,45,50,53,3 lens ultima, Stricklandia 17 Stark Cemetery 54 Lepidocyclus cooperi Hov/e. 1966 10 State Route 79 54 Lesperance (1974) 25 State Route D 54 Lesperance (1985) 9,17,24,25 State Route W 53 Lesperance and Sheehan (1976) 25 Montoya Group 48 Liebe(1962) 12,16 Mosalem Formation 5,21-23,25-27,29,30,32,35,49-51,55,8 Liebe and Rexroad (1977) 19,21,54 lindstroemophylloides. Brachyelasma 42 nathani (ct), Oulodus'! 17 Lindstrom (1882) 34,49,50 National Quarry 20 Long and Copper(1987) 27 Natural Sciences and Engineering Research Council of Canada Lost Mound (Section 10) 22,50,54 6 Louisiana, Missouri-Illinois Quadrangle 54 Neda Formation 18,20,21,23,27,8 Neelys Landing, Missouri-Illinois Quadrangle 54

Maine, Neospathognathodus celloni (Walliser, 1 964) 17 northern 28 Neotryplasma Kaljo, 1957 51 Penobscot Co 49 ./7oHen Elias, 1986a 52 Manitoba, southern 27 Neuman (1969) 25,33,34,41,42,46,47,49-51 manniensis, Platymerella 17,21,26 Neuman (1974) 33 Maquoketa Neuman (1975) 24,34,41,42,44.47 Formation 16,25,26 Neuman (1977) 33.49.50 Group 5,6,18-23,27.8 Neuman (1982) 25,42 Shale 13-15,20,21,27,8 Neuman (1984) 32,51 Marshall. Arkansas Quadrangle 53 Neuman (1986) 34,41,44,51,52 Mattison (1983) 6 Neuman (1988) 49 Mattison. B. W 6,33 New Mexico 48 Maxwell (1936) 7,8,51 New Wells (Section 19) 11,12,29-32,35-42,54 Mayville Dolomite 20 New York 41 McAuley (1983) 6 MiddleviUe 34 80 Bulletin 333

Niagaran Series 26 Platymerella zone 2 Nicholson and Lydekker (1889) 32,33,51 Platymerella manniensis zone 19,26,B

'* NicoU and Rexroad (1968) 12 Platymerella'? sp 1 Noix Pleasant Hill West, Illinois-Missouri Quadrangle 54 Limestone 5,12-18,25,26,32,47,48,54,8 Pollock, Rexroad. and Nicoll (1970) 21 oolite 14 polytabulalum. Crassilasma 42 Noixodomus conodont fauna 8,10 Porfirieviella Ivanovskiy. 1963 34 Noixodontus girardeauensis (SaXXexfitXA. 1971) 8,12,15,17 primum. Norby, R. D 7 Brachyelasma 42 North American Province 25 Streptelasma 41,42,44 North European Province 25 primum (cf), Streptelasma 41,44 Norway 25,41,42,46,49 Prioniodiis ferrariiis conodoni fauna 12.17 protriplesiana. Slncklandia 12 Ohio 23,48,49 Pryorand Ross (1962) 12,5."? Oklahoma 7,26,27,46 Pterospathodus amorphognathoides zone Id Ardmore 7 Pterospathodus celloni Conodont Zone 9. Id Caner Co 7,34.53 pulchella. Grewingkia 24 Cedar Village 53 pulchella (sp. cf). Grewingkia 24 Coal Co 7,34,52,53 putillus. Climacograptus 12 Coal Creek 53 Pycnostylusl sp 22,26 Gobbler Knob 53 Hickory Creek 53 Quebec 7 LawTence 53 Anticosti Island 8,23,24,27,29,41 Murray Co 7,53 eastern 28 northeastern 8 Pointe Laframboise 23 Pontotoc Co 7.34,43,45,47,48,51-53 Quails F,8 randi. Sahadorea 5,11,12,22-24,27,8 south-central 5-7,25-27,35,43,45,47,48,51-53,8 Rectigrewingkia Y^aXjo. 1961 51,52 Oklahoma Geological Survey, Norman. Oklahoma 6,43 anthelion (Dybowski, 1873) 52 oklahomeme, Keelophyllum 11,12 5,7,8,24, Red River Formation 29,30,36,48,51,52,53,8 Fort Garry Member 27 Selkirk 27 Oliver, W. A., Jr 7 Member River-Stony Mountain Solitary Rugose Coral Province Ontario 48 Red 5,6,24,27,28,31,32 Orchard Creek Shale 10-12,23,8 6,8,26 Ordovician-Silurian boundary 5,9,17,23,26 Reeds (1911) 8,17 ordoviacus. Amorphognathus 12,16,17 Rexroad (1967) Rexroad and Droste (1982) 21 Orihograplus vesiculosus Zone 21 Rhegmaphyllum Wedekind, 1927 5,28,<^9 oslrogolhicum. Streptelasma 25,46,47 daytonensis {Foe.TsXe, 1890) 49 Oulodus"} nathani Conodont Zone 8,9,17 sp 12,13 5,9,10,13,15,16,19,20,22-25,27,28,-^9,3 1 Oulodus? cf. a? nalhani McCracken and Barnes, 1 98 1 17 Coral Province .... 5,6,24,27,28,31,32 Overbrook, Oklahoma Quadrangle 53 Richmond Solitary Rugose Richmondian Stage 26 Orar/toia /losi; (Pollock. Rexroad, and Nicoll. 1970) 21 Richmondian-Gamachian boundary 27 Ozarkodina hassi interval 21 Riley, Illinois Quadrangle 54 Risk, Pagani, and Elias (1987) 29 Paleontological Research Institution, Ithaca, New York 7 Crossing (Section 21) 7,8,32,34,36-42,5i Paltodus dyschtus RexToad, 1967 17 Rock 33 Pallodus dyscritus conodonl fauna 12.15.17.21,26 Roemer(186l) 22,55 Panderodus simplex Zone 21 Rose (1967) 19,20,25,54 Parakidograptus acuminatus Graptolite Zone 9,17,21,24,25 Ross (1962) 22,23,25,55 Paramplexoides Ross (1964) 14 atlenuatum He, 1978 45 Rowley (1904) Rowley (1908) 14,15 cylindncus He, 1978 45 14,15 Paraorihograplus pacifkus Graptolite Zone 8 Rowley (1916) Rubey (1952) 12,14 parasiUcum. Streptelasma (1) 48 Parkinson. R 12 patella, Bighornia 23 Scoll 33-35,45 Peel (1977) 8 Sahadorea randi (E\{a%, 1981) 5,11,12,22-24,27,8 penobscolensis, Grewingkia 49 Sattertield (1971) 8,10-12,15,17,53 Pctryk (1981a) 23 Savage (1906) 21 Pctryk (1981b) 27 Savage (1908a) 6,26 Pelryk, A. A 7 Savage (1908b) 6,26 Petlit Formation 8 Savage (1909) 6,26 Pirgu Stage 41 Savage (1910) 6,12,26,53 Plaines West (Section 6) 19,20,50,5-^ Savage (1912) 6,26,38 Platteville Limestone 48 Savage (1913a) 6,26,27,38 8

Ordovician-Silurian Rugose Corals: McAuley and Elias

Savage (1913b) 5,6,8,10-12,14-18,20-22,24-27, Dimorphosiphon 8,1 1,14 29-32,34-45,52,53 Dinophyllum 13 5,13,15,16,19,20,22-24,28,49,50,8 Savage (1914) 6,12,14,17,18,20,21,23,26 Icriodellal 17 Savage (1916) 6,20,21,26 Plalymercltal 19 Savage (1917) 6,11,12,14,15,17,18,20,21,26,27,34,35,38,53 I'ycnoslylus} 22,26 Savage (1926) 6,18,22,23,26,54 Rhcumaphyllum 12,13 5,9,10,13,15,16, Savage and Ross (1916) 20 19,20,22-25,27,28,49,8 Savage, T. E 6,12,33 Sireplelasma 11,24,29,34,38,42,44 Schapville (Section 11) 22,55 Trypamtes 11,12,15,30 Scheffen (1933) 49 Springbrook, Iowa-Illinois Quadrangle 54 Schweizer North (Section 5) 18-20,49,54 St. Clair Spring Section 9,10,24,27,49,55

Schweizer West (Section 4) 1 8-21, 35-4 1,.W Stage Scotland 21 5a 41,46,49 Sears Pit (Section 29) 19,20,35,51,54 5b 42 Second Value Dolomite, Upham Dolomite Member 48 6a 42 Section 6b 42 3 (Garden Prairie) 18-21,35,37-41,54 6c 42 4 (Schweizer West) 18-21,35-41,54 State University of New York, Binghamton, New York 7 5 (Schweizer North) 18-20,49,54 Stock, C. W 7 6 (Plaines West) 19,20,50,54 Stockton (Section 12) 22,55 7 (Kankakee River) 20,54 Stonington Formation, Bay de Noc Member 48

8 (King) 21,22,55 Sireplelasma \\?A\. 1847 ii,34,38 9 (Winston) 21,22,51,55 aifi«e (Billings, 1865) 41,42 22,50,54 10 (Lost Mound) amsdeni. n. %x> 5,6 5,7,8,24,25,29-33. 11 (Schapville) 22,55 36,38,40,42,4i,44,45,8 12 (Stockton) 22,55 corniculum Ha.\\. 1847 34,41 13 (Bowling Green) 13-15,17,18,35-42,54 cf dislinclum Wilson, 1926 42 14(Higginbotham Farm) 7,13,17,18,32,35-42,45,48,54 (//vanfaf!5 (Nicholson, 1875) 34,48 15 (Calumet) 13,30-32,35-42,45,47,54 eccenlricum 'Hsnmzn, 1969 46,47 16 (Clinton Spring) 13-15,18.30-32,35-42,54 elnaense Elias tn Elias and Potter, 1984 46,47 17 (Clarksville) 13,15,16,18,30-32,35-42,49-51,54 insolitumHe. 1978 42 18 (Kissenger) 13-16,30-32,35-42,54 leemonense Elias, 1982a 7,8,9 5,7-13,15,24-27, 19 (New Wells) 11,12,29-32,35-42,54 29-32,36,45,46,47,52,8

20 (Short Farm) 10-12,29-32,35-42,45.50,5i sp. cf. S. leemonense Elias, l9S2a 9 5,7,8,24,30,36,46,47,8 21 (Rock Crossing) 7,8,32,34,36-42,5J ostrogothicum 'Neuman, 1969 25,46,47 22 (Cedar Village) 8,5i primum (Wedekind, 1927) 41,42,44

23 (Lawrence Quarry) 7-9,30-32,34,36-4 1,45-48, 5 l,52,5i cf. primum (Wedekind. 1927) 41,44 24 (Coal Creek) 7-9,3 l,32.36,38,40,42,43,5i sp 11,24,29,34.38,42,44 25 (Hunton) 7,34,36-38,41, 52,5i sp. A 9,10 5,13,15,24,29.32,47.48,8 26 (Bellevue) 21,22,54 subregulare (Savage, 1913b) 1,2,3,4,5 5.7,8, 29 (Sears Pit) 19,20,35,51,54 ll-13,15,16,19,20,22,24-26,29-33,i4,36^5.52,B 30 (Thomson Northeast) 22,54 sp.cf. S. subregulare [Savage, I9l3b) 5 5,9,10,24, 31 (Thebes North) 10-12,29,32,34,36-42,45,5i 25,27,42,43,8 32 (Thomson East) 22,23,26,29,30,35-42,49,50,54 unicum Neuman, 1975 25,41,42,44,45

33 (Buffalo River) 9,10,27,42,45,5i Sireplelasma (?)parasilicum Ulrich in Winchell and Schuchert, 1 895 34 (Belvidere South) 7,18,20,21,35-42,54 48 Sequatchie Formation 24 Slreploplasma Hall 1847 33 Sexton Creek Limestone 5,10-12,14,17,21,26,50,8 Slhcklandia Sheehan(1988) 6 lens utlima Williams. 1951 17 Shellmound Formation 24 prolriplesiana {Amsden, 1966) 12 Short Farm (Section 20) 10-12,29-32,35-42,45, 50,5i triplesiana (Foersie, 1890) 17 shorn. Bodophyllum 5,11,24,29,48,50,51,8 subregulare, Sireplelasma 1,2,3,4,5 5.7,8,11-13,15, Siberian platform 28 16, 19,20,22,24-26,29-33, i4,36^5.52.B

Silurian assemblage 5,23,24,26,28,29 subregulare (sp. d.), Sireplelasma .. 5 .. 5,9,10,24,25,27,42,43,8 simplex. Helicelasma 25,42 subregularis, Zaphrenlis 20,34,35,38

simplotabulalum, Brachyelasma"} 45 subregularis (cf.), Zaphrenlis 35 sinensis. Borelasma 42 Sulphur Rock, Arkansas Quadrangle 55

Sorauf, J. E 1 svarloeyensis. Vllernelasma 42 sp. A, Sweden 41,42,47,49,52 Grewingkia 10 5, 7,8, 13, 15,24-26,29,32,45,49, 51,53,8 Ostergotland 5,24 Sireplelasma 9,10 5,13,15,24,29,32,47,48,8 Sweet and Bergstrom (1976) 9,12 sp. a, Borelasma 42 Sycamore, Illinois Quadrangle 54 sp. b, Borelasma 42 Sylvan Shale 7-9,25.8

sp., Cyathaclisn 14 5, 7,8, 13,15, 16,19,20,22-24,28,5/, Templeton and Willman (1963) 23 Dalmanophyllum ... 14 ... 5,11-13,15,16,19,20,22-24,28,50,8 Tete des Morts Formation 21,22,26,55,8 82 Bulletin 333

Texas 48,51 Wahlman. G. P 7 Thebes North (Section 31) 10-1 2,29,32,34,36-42,45,5i Wales 21 Thebes. Illinois-Missouri Quadrangle 53 Walliser (1964) 17

Thompson and Sanerfield( 1975) . 6.10-12,14-18,21,25,26,53.54 H 'alliserodus curvatus (Branson and Branson, 1 947) 8 Thomson East (Section 32) 22,23,26,29,30,35-42,49,50.54 Wang (1947) 49 Northeast (Section 30) 22.54 Thomson Wapanucka North. Oklahoma Quadrangle 53 Thomson. Illinois Quadrangle 54 Watson Limestone 15 Transcontinental Arch 27 Wedekind (1927) 5,28,32,33,41,44,49 Trenton Limestone 34,41 Welcher. A.-M 7 "Trenton limestone" 48 Weller(1940) 53 "Trenton shales" 48 Weyer(1973) rnp/wia atoa Ulrich and Cooper. 1936 9,10.26 51 thplesiana. Stricklandia 17 Weyer(1974) 49 Trypanitessp 11.12.15,30 Whitewater Formation 48 Turner Falls. Oklahoma Quadrangle 53 Whitlow and Brown (1963) 21-23,55 Wilhelmi Formation 18-21.25-27.29,32,35.54.8 U. S. Route Birds Member 5.18-21.25.26.30.35,54,3 167 55 Schweizer Member 5.18-21.23.25.30,35,54,3 20. 54 Williams (1951) 17 52. 55 Williston Basin 27 54. 54 Willman (1962) 54 54 61 . Willman (1973) 17,18,20,21,23,25,26,54,55 65 53 Willman and Atherton (1975) 10,12,17,18,21,23.26 77 53 Willman and Buschbach (1975) 10,12,18,20,23 U. S. S. R.. Ural region 51 Wilson (1926) 23,42 UCGM [L'niversily of Cincinnati Geological Museum, Cincinnati, Winchell and Schuchert (1895) 48 OH, U. S. A.)' 33-35,45.50 Winston (Section UI [University of Illinois at Urbana-Champaign, Urbana. IL, U. S. A.] 9) 21,22,51,55 33-35.45 Winston Limestone 21,23 Ullernelasma 'Neuman, 1975 34 Wisconsin. svartoeyensis Neuman. 1975 42 eastern 5,6,20,23,27 Ulrich and Cooper (1936) 9,10,26 High CliffPark F,20 Ulrich, E. 20 Katell Falls F,20 unicum. Sneptetasma 25.41,42,44,45 Little Sturgeon Bay F,20 United States Geological Survey. Washington. DC 7,53 Woodcock and Smallwood (1987) 27 University of Alabama. University. Alabama 7 University of Cincinnati. Cincinnati. Ohio 7 yentzekouense, Brachyelasma 42

University of Illinois at Urbana-Champaign. LIrbana. Illinois .. 7 Yukon 8 University of Manitoba. Winnipeg. Manitoba 6 University of New Orleans. New Orleans. Louisiana 7 Zaphrentis 35 USNM [National Museum of Natural History. Smithsonian Insti- amWgiM Savage, 1913b 20,34,35,38 tution. Washington. DC, U. S. A.] 33-36,42,43.45-52 channahonensis 35,38 subregidans Savage. 1913b 20,34,35,38 Vaureal Formation 24,27.41 cf subregidans 35 Venezuela 28 Zeilstra, R. G 6,33

^ « i '^ » i S I " ~ 1 1 1 M

a Q. 'BRASSFIELO' •bhassfield' ? i i in VI

I I

I 1

FERNVALE LST. (MAYSVILLIAN- 7RICHMONDIAN)

SOUTH-CENTRAL (WEST) (EAST) SOUTHERN ILLINOIS AND OKLAHOMA NORTH-CENTRAL ARKANSAS SOUTHEASTERN MISSOURI

^ BLANDING AND TETE DES -V-^^i^^^^^i^ ^- MORTS FMS. ELWOOD

SCHWEIZER

(WEST) (EAST) NORTHEASTERN NORTHWESTERN ILLINOIS NORTHEASTERN MISSOURI ILLINOIS AND EASTERN IOWA

Text-figure lO.-Composite stratigraphic sections showing age and correlation of uppermost Ordovician to lowermost Silurian units and of taxa distribution of solitary rugose corals in the east-central United States. Thicknesses of units are not to scale. Lines depicting ranges containing the above the Richmondian show relative positions within the units, based on inspection of data in Text-figures 2-5, 7, 8. Units Edgewood solitary coral assemblage (Gamachian to early Early Llandovery in age) are stippled. Hachures indicate the Plalymerella manmensis zone.

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Collinson, J. 1962. Size of lettering for text-figures. Journal of Paleontology, vol. 36, p. 1402. Gilbert Dennison Harris (1864 - 1952)

Founder of the Bulletins of American Paleontology (1895)

ISBN 0-877 10-414-X

3 2044 072 271 950

Date Due jytH-^-^Z