Idiognathodus and Streptognathodus species from the Lost Branch to Dewey sequences (Middle‐Upper Pennsylvanian) of the Midcontinent Basin, North America
by
Steven J. Rosscoe B.A., M.S.
A Dissertation
In
GEOSCIENCES
Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Approved
Dr. James E. Barrick
Dr. Peter Holterhoff
Dr. Tom Lehman
Dr. Sankar Chatterjee
Dr. George Asquith
Fred Hartmeister Dean of the Graduate School
August, 2008
Copyright 2008, Steven Rosscoe
Texas Tech University, Steven J. Rosscoe, August 2008
ACKNOWLEDGEMENTS
I would like to thank the many people in my life, both personal and professional, for their support and help in completing this dissertation. Special thanks to Jim Barrick, as my dissertation committee chair and mentor, who has pushed me to become the paleontologist I am today. Thanks also to Peter Holterhoff, my guide to all things stratigraphic and the discoverer of localities. Thanks also to Tom Lehman, Sankar Chatterjee, and George Asquith for serving as committee members, providing valuable comments and critiques of my work, and for teaching me so much geology. Thanks to Mark Grimson and University Imaging Center for access and use of the Hitachi S570 SEM. I would like to extend thanks to the Department of Geosciences at Texas Tech University for supporting my work and providing me with opportunities to teach labs and lectures. I can’t forget the rest of the faculty of the department, or Barbara Graham and Allison Winton for keeping me on track. Thanks also to Provost Marcy and The IDEAL Program for financial support in the summer months and the opportunity to participate in a great outreach program. Special thanks to Phil Heckel, for sharing his valuable field knowledge and his assistance in reviewing papers. I would also like to thank Jeff Over, for sparking my interest in conodonts and helping me to choose the right path in my academic life. Thanks to Jacob Bilbo, for travelling the vast stretches of Oklahoma and Kansas with me and his valuable assistance in the field. Thanks should also be given to the office‐mates. These poor souls (Jim Lehane, Jeremy Bader, and Joseph Schubert) have listened to me rant, thinking out loud and suffered my musical tastes without complaint. Thanks to the graduate students who have shared both their academic aid and personal friendship throughout my time at Texas Tech. The following list is almost certainly incomplete: Lori Manship, Karen Waggoner, Holly Woodward, Jeremy Bader, Rissa Westerfield, Jeremiah Kokes, ReBecca Hunt, Jim Lehane, and anyone else I forgot. On a personal level, I would like to thank the following people. Michelle Sperbeck for coming with me on this Texas adventure and helping me reach this goal (and now for moving with me in the future). My family back in New York for their support even when I’ve been so lost in my research that I forget to call or even write. Without the support of family and friends, none of this would have been possible.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
ABSTRACT v
LIST OF FIGURES vi
CHAPTER ONE: INTRODUCTION 1 History of Middle‐Upper Pennsylvanian Conodont Taxonomy 2 Geologic Setting 4 Cyclic Deposition in the Middle and Late Pennsylvanian 4 Middle and Late Pennsylvanian Sequence Stratigraphy 5 The Lost Branch Sequence 6 The Hepler Sequence 7 The Shale Hill Sequence 8 The Hertha Sequence 9 The Swope Sequence 10 The Mound Valley Sequence 11 The Dennis Sequence 12 The Hogshooter Sequence 13 The Cherryvale Sequence 14 The Dewey Sequence 16
CHAPTER TWO: MATERIALS AND METHODS 23 Sample Collection, Preparation, and Presentation 23 Function‐Based Taxonomy 23 Function of P1 Elements in Idiognathodus 24 Selection of Significant Characters in Idiognathodus 25 Application to the Genus Streptognathodus 32
CHAPTER THREE: THE DIVERSIFICATION OF IDIOGNATHODUS AND THE RISE OF STREPTOGNATHODUS IN THE MIDCONTINENT BASIN, UNITED STATES 36 The Late Desmoinesian Extinction 36 The Swadei Lineage 37 The Turbatus Lineage 38 The Idiognathodus biliratus Problem 40 The Sulciferus Lineage 40 Origin of Streptognathodus 43 Model of Evolution in Idiognathodus and Streptognathodus 44
CHAPTER FOUR: IMPLICATIONS OF THE NEW TAXONOMY 53 A Revised Late Desmoinesian to Middle Missourian Conodont Zonation 53 Other Global Conodont Faunas 55 Moscow Basin 55 Donets Basin 56 China 57 Spain 58
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Potential for Global Correlation 58 Selection of Global Events 58 Boundary Definition 60
CHAPTER FIVE: CONCLUSIONS 68
REFERENCES 70
APPENDICES 77 Appendix A: Locality Register 77 Appendix B: Systematic Paleontology 107 Appendix C: Hydrogen Peroxide Method for the Breakdown of Black Shales 188
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ABSTRACT
A function‐based taxonomic method was developed to revise Idiognathodus and Streptognathodus species from the Lost Branch Sequence (latest Desmoinesian) to the Dewey Sequence (Middle Missourian). The new method relies on characters significant to the food‐ processing function of the P1 element. The chief controls over food processing efficiency are surface area and surface roughness. The two primary morphological features affecting surface area are the shape and size of the rostral lobe and the shape and size of the caudal lobe. Ornamentation of the ventral and dorsal platform affects surface roughness. Use of these three features as the major characters to discriminate species resulted in the description of twenty‐ four species of Idiognathodus and five species of Streptognathodus. A regional zonation for the Midcontinent Basin (North America; Barrick et al. 2004) was revised based on the new taxonomic scheme for Swadelina, Idiognathodus and Streptognathodus. Five zones and five subzones were erected within the study interval. The Swadelina nodocarinata zone of Barrick et al. (2004) includes the Lost Branch Sequence. The new Idiognathodus sulciferus zone includes the Hepler Sequence. The I. eccentricus zone comprises the Shale Hill and Hertha sequences. The revised I. cancellosus zone (two subzones) includes the Swope, Mound Valley, and Dennis sequences. The S. gracilis zone (three subzones) comprises the Hogshooter, Cherryvale, and Dewey sequences. The merit of three proposals for levels characteristic of the boundary between the global Moscovian and Kasimovian Stages are discussed. The first level is the traditional base of the Missourian (near the traditional base of the Kasimovian) based on the disappearance of the last species of Swadelina. The second level is based on the first appearance of I. sagittalis (not found in the Midcontinent Basin), which can be approximated using the appearance of distinctive forms of I. swadei, I. turbatus, or I. eccentricus (near the redefined base of the Missourian). The third level is at the highstand in the Swope Sequence and marks the first co‐occurrence of I. cancellosus and I. biliratus, two of the few species that may have had global distribution.
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LIST OF FIGURES
1. Paleogeography of the Laurasian portion of Pangaea during Middle and Late Pennsylvanian time at sea level highstand. 18
2. Regional geography of the Midcontinent Basin, North America. 19
3. Model of the typical Kansas‐type cyclothem for the Lost Branch Cyclothem (High Frequency Sequence). 20
4. Diagrammatic model of the Lower Missourian Composite Sequence. 21
5. Diagrammatic model of the Middle Missourian Composite Sequence. 22
6. Terminology used in the methodology and systematic paleontology section of this paper. 34
7. Diagrams representing each of the major variations observed in the conodont genera Idiognathodus and Streptognathodus in the study interval. 35
8. The lineage of Idiognathodus swadei. 47
9. The lineage of Idiognathodus turbatus. 48
10. The lineage of Idiognathodus sulciferus. 49
11. The potential origin of Streptognathodus from Idiognathodus cherryvalensis. 50
12. Composite range chart of conodonts within the uppermost Marmaton Composite Sequence, the Lower Missourian Composite Sequence, and the Middle Missourian Composite Sequence. 51
13. Variations in number of species of Idiognathodus and Streptognathodus from the Lost Branch Sequence to the Dewey Sequence. 52
14. Comparison of conodont zonations globally and regionally with the zones proposed in this dissertation. 65
15. Global and local controls on sea level and their effect on conodont‐based Correlations between North America (Midcontinent Basin) and Eurasia (Moscow Basin). 66
16. Conodont zonation for the Midcontinent Basin and proposals for the location of the Moscovian‐Kasimovian (Middle‐Upper Pennsylvanian) Boundary. 67
17. Key to measured sections (Appendix A) and diagrammatic cross sections (Figures 4 and 5). 83
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18. Measured section for Little River. 84
19. Measured section for the Roadditch South of Sasakwa. 85
20. Measured section for Uniontown K‐3. 86
21. Measured section for Tackett Mound I. 88
22. Measured section for Fort Calhoun Quarry. 89
23. Measured section for Jingo – Kansas 69. 91
24. Measured section for Mason Road. 93
25. Measured section for Clear Creek. 94
26. Measured section for Coffeyville Southwest. 95
27. Measured section for K‐39 at Big Creek. 96
28. Measured section for Ramona Railroad Crossing. 97
29. Measured section for Hogshooter South (Dennis Sequence) and New Harmony (Cherryvale Sequence) south of Hogshooter, Oklahoma. 98
30. Measured section for section East of Ochelata in stream along Northbound US 75 near Ochelata, Oklahoma. 99
31. Measured section for the Zink Ranch, near Sperry, Oklahoma. 100
32. Measured section for Hogshooter Quarry, operated by Belco. 101
33. Measured section for Bannister Road. 102
34. Measured section for the reference section for the Drum Limestone. 103
35. Measured section for Skiatook Dam west of Skiatook, Oklahoma. 104
36. Measured section for KAW Drive. 105
37. Selected photos from field work localities. 106
38. Idiognathodus expansus Stauffer and Plummer, 1932. 157
39. Idiognathodus swadei Rosscoe and Barrick, In Press. 159
40. Idiognathodus harkeyi Gunnell, 1933. Idiognathodus sulciferus Gunnell, 1933 Idiognathodus fusiformis Gunnell, 1933. 161
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41. Idiognathodus turbatus Rosscoe and Barrick, In Press. 163
42. Idiognathodus species 1 Rosscoe and Barrick, In Press. Idiognathodus eccentricus (Ellison, 1941). Idiognathodus vorax Rosscoe and Barrick, In Press. 165
43. Idiognathodus cancellosus (Gunnell, 1933). Idiognathodus aff. cancellosus. Idiognathodus biliratus Gunnell, 1933. 167
44. Idiognathodus folium Gunnell, 1933. Idiognathodus siculus Gunnell, 1933. 169
45. Idiognathodus cherryvalensis Gunnell, 1933. Idiognathodus confragus Gunnell, 1933. Idiognathodus lobatus Gunnell, 1933. 171
46. Idiognathodus clavatulus (Gunnell, 1933). Idiognathodus species 2. Idiognathodus corrugatus Gunnell, 1933. 173
47. Idiognathodus species 3. Idiognathodus fusiformis Gunnell, 1933. 175
48. Idiognathodus cherryvalensis Gunnell, 1933. Idiognathodus multinodosus Gunnell, 1933. Idiognathodus symmetricus Gunnell, 1933. 177
49. Idiognathodus folium Gunnell, 1933. Idiognathodus magnificus Stauffer and Plummer, 1932. 179
50. Idiognathodus magnificus Stauffer and Plummer, 1932. Idiognathodus species 4. 181
51. Streptognathodus sulcatus Gunnell, 1933. Streptognathodus elegantulus Stauffer and Plummer, 1932. Streptognathodus gracilis Stauffer and Plummer, 1932. 183
52. Streptognathodus excelsus Stauffer and Plummer, 1932. Streptognathodus increbescens Stauffer and Plummer, 1932. 185
53. Dorsal views of selected P1 elements of Idiognathodus and Streptognathodus from the study interval. 187
53. Flow chart showing the processing of materials using the hydrogen peroxide breakdown method. 191
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CHAPTER 1 INTRODUCTION
The interval from the latest Desmoinesian through the middle Missourian in the Midcontinent basin of North America is a key time for the diversification of the conodont genera Idiognathodus and Streptognathodus. Recovery from significant conodont extinction in the late Desmoinesian drove the fast‐paced diversification of Idiognathodus in the early Missourian and the rise of the descendent genus Streptognathodus in the middle Missourian. P1 elements have the most diverse morphologies in these genera and distinctive differences have been noted by a variety of authors (Grayson et al., 1990; Ritter, 1995; Barrick et al., 1996; Barrick et al., 2002), yet the systematic characterization of Idiognathodus and Streptognathodus species has been relatively untouched in the Midcontinent Basin. Several authors (Swade, 1985; Ritter et al., 2002; Barrick et al., 2004) have emphasized the importance of a systematic revision of species‐ level taxonomy in these genera. This stratigraphic interval is composed of ten fourth‐order high frequency sequences. These high‐frequency sequences can be grouped into the upper portion of one and two complete third‐order sequences (Holterhoff, 2007a; Holterhoff, 2007b). The Lost Branch Sequence is the last highstand sequence in the Marmaton Composite Sequence (MCS)(Holterhoff, 2007b). The Hepler, Shale Hill, Hertha, and Swope sequences make up the Lower Missourian Composite Sequence (LMCS). The Mound Valley, Dennis, Hogshooter, Cherryvale, and Dewey sequences make up the Middle Missourian Composite Sequence (MMCS)(Holterhoff, 2007a). The MCS is characterized by the extinction of all species of Neognathodus and Swadelina, as well as Idiognathodus expansus, in the Lost Branch Sequence. The LMCS is characterized by the rapid diversification of the genus Idiognathodus. The LMCS is particularly important on the global scale. The boundary between the Desmoinesian and Missourian North American Regional Stages is defined by the first occurrence of I. eccentricus at the base of the Exline Limestone in the Shale Hill Sequence (Heckel et al., 2002). In addition, work on the establishment of a Global Stratotype Section and Point (GSSP) for the international Moscovian‐Kasimovian Stage (Middle‐Upper Pennsylvanian Series) Boundary has focused on the Shale Hill and Hertha sequences in the Midcontinent. The use of conodonts as a biostratigraphic marker for this boundary has focused on species of Idiognathodus (Villa, et al. 2004, 2005,
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2006). The MMCS is characterized by the continued diversification of Idiognathodus and the derivation of species of Streptognathodus from Idiognathodus species. The purpose of this study is to revise the species‐level taxonomy of Idiognathodus and Streptognathodus in the interval spanning from the latest Desmoinesian Lost Branch Sequence to the middle Missourian Dewey Sequence. To accomplish this, a taxonomic methodology has been developed that places greater reliance on characters significant to element function, rather than on those reflecting environmental variation. This allows one to establish a revised taxonomy, a uniform terminology, and to better interpret the evolutionary relationships between the species of Idiognathodus and Streptognathodus. This revised taxonomy will allow for a detailed explanation of the origins of Streptognathodus species and evaluation of species in contention for use as the biostratigraphic marker of the Moscovian‐Kasimovian Boundary. Comparison of the new range and lineages of species of Idiognathodus and Streptognathodus in the Midcontinent to those from the Moscow and Donets basins will allow for the determination of the most likely levels of communication between basins and the presence of a correlateable cosmopolitan species of Idiognathodus. A portion of this dissertation has been submitted for publication by Rosscoe and Barrick (In Press).
History of Middle‐Upper Pennsylvanian Conodont Taxonomy The first works describing species of Idiognathodus from the Desmoinesian and Missourian of the Midcontinent were conservative in the number of species named (Gunnell, 1931 – Missouri; Stauffer and Plummer, 1932 – North‐central Texas; Harris and Hollingsworth, 1933 – Eastern Oklahoma). The species defined by these early workers were differentiated on gross morphological characters of the P1 element. Gunnell (1933) published the first work based on large collections from mostly Missourian strata in the Kansas City Region. The morphologically diverse collection resulted in 45 total species of Idiognathodus and 22 species of the closely related, troughed genus, Streptognathodus. The species in Gunnell’s (1933) work were based on small‐scale variations of the P1 element, a much finer level of detail than previous works. Although the description of variability in Idiognathodus was very detailed, the taxonomy presented was poorly designed and difficult to use. Ellison (1941) took on this morphologically diverse group and combined Gunnell’s numerous species into a few easily identifiable taxa: eight species of Idiognathodus and ten species of Streptognathodus. The simplicity of this taxonomy allowed it to remain the standard
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of nearly all of the subsequent works on Missourian Idiognathodus and Streptognathodus for the next 40 years. Despite the apparent success of the Ellison (1941) revision, the species were so broadly defined that they provided no biostratigraphic resolution or sense of an evolutionary history (Grayson et al., 1990). In nearly all cases, Ellison’s species range over long stratigraphic intervals and the Pennsylvanian appeared to be an interval of time when evolutionary change in ozarkodinid conodonts was stagnant. The designation “Idiognathodus/Streptognathodus plexus” (Merrill and von Bitter, 1984) was used to emphasize the apparent strong ecological control on the morphology of Idiognathodus and Streptognathodus (Merrill, 1971; Merrill and von Bitter, 1976). Paleoecological studies of conodonts in Midcontinent cyclothems during the 1970’s and 1980’s reduced the focus on the species, leading to the extreme interpretation that nearly all variations in P1 elements of Idiognathodus and Streptognathodus were a response to local environmental conditions, and that only one or two species were present during any interval of time (Merrill and von Bitter, 1984; Grayson et al., 1990). In his work on the multi‐element taxonomy of Missourian conodonts, Baesemann (1973) went one step further, and placed all Midcontinent Late Pennsylvanian idiognathodids in one species, I. delicatus Gunnell 1931. In contrast, Swade (1985) sampled successive core shales of Desmoinesian cyclothems and described morphological variability in such a way to enable the recognition of each cyclothem in the Midcontinent. His success started new investigations into the biostratigraphic utility of Pennsylvanian conodonts that focused on the distinctive morphotypes representative of each cyclothem and their potential for correlation of cycles (Barrick and Boardman 1989; Boardman and Heckel, 1989; Barrick et al., 1996). Ritter (1995) presented the first new conodont zonation for the Late Pennsylvanian and earliest Permian of the Midcontinent using morphotypic species of Idiognathodus and Streptognathodus. Barrick et al. (2004) presented a conodont zonation for the Pennsylvanian of the Midcontinent that utilized morphotypic species of Idiognathodus and Neognathodus for Lower and Middle Pennsylvanian Zones. This zonation used a morphotypic species of Idiognathodus and Streptognathodus for Late Pennsylvanian Zones. Extension of the Midcontinent morphotypic conodont Zones outside of the Midcontinent region has met with some success, as shown by Ritter et al. (2002), but additional research on sections in western North America is needed to evaluate their applicability.
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Geologic Setting During Pennsylvanian time, most of the present‐day United States was part of the Laurasian portion of the growing supercontinent Pangaea. Much of the region was intermittently submerged beneath the cratonic Midcontinent Sea, which connected to the Panthalassa Sea (the Protopacific Ocean) in the west (Figure 1). The Ancestral Rocky Mountains were to the northwest of the Midcontinent Basin during Pennsylvanian time. South and east of the Midcontinent Basin were the Appalachian‐Hercynian Highlands, the suture Zone between North America and Europe (Heckel, 2002a). The Midcontinent Basin is structurally complex, but is often discussed in the general terms of a basin in Oklahoma, a shelf margin near the Oklahoma‐Kansas border, and a shallow shelf from Kansas and northward (Heckel, 1999). The Bourbon Arch runs northwest to southeast through east‐central Kansas, while the Nemaha Uplift (bounded by high angle faults in the east) runs from north northeast to south southwest through eastern Kansas (Lee, 1943) (Figure 2). The Bourbon Arch and Nemaha Uplift act as regional topographic highs on the shelf and controlled deposition of Pennsylvanian rocks in the Oklahoma, Kansas, Nebraska, Iowa, and Missouri (Lee, 1943; Joeckel et al. 2007). East of the Nemaha Uplift and north of the Bourbon Arch is the Forest City Basin; west of the Nemaha Uplift is the Salina Basin. East of the Nemaha Uplift and south of the Bourbon Arch is the Cherokee Platform (as it is known in Oklahoma; Cherokee Basin in Kansas) (Lee, 1943; Joeckel, et al. 2007). The deposits of the Midcontinent Sea are exposed in a narrow swath from southern Oklahoma to Nebraska (Heckel, 1999). Surface exposures were investigated from eastern and central Oklahoma, eastern Kansas, eastern Nebraska, western Missouri, and western Iowa (Figure 2).
Cyclic Deposition in the Middle and Late Pennsylvanian Middle and Late Pennsylvanian time was characterized by a series of glacial advances and retreats centered on the Gondwanan portion of Pangaea. Gondwanan glaciations were likely occurring on a scale equivalent to the 100,000 year Milankovitch eccentricity cycle (Rasbury et al., 1998). Repeated high frequency advance and retreat of continental glaciers in Gondwana can be tied to high frequency changes in eustatic sea level. Sea level rise, associated with glacial retreat, resulted in transgression of the Midcontinent Sea. Sea level decline, associated with glacial advance, resulted in regression of the Midcontinent Sea. For each advance‐and‐retreat cycle, deposits in the Midcontinent Basin reflect deepening followed by
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shallowing of the Midcontinent Sea (Heckel, 1986; Blaine et al., 2003). Although the eustatic signal is the primary control of sea level, regional tectonics and climate will cause enough local variation in sea level that the relationship between sea level and Midcontinent high frequency sequences may not be correlated precisely one‐to‐one (Blaine et al., 2003). The most descriptive model for cyclic deposition in the Midcontinent Basin is the cyclothem model developed by Phil Heckel. The typical (Kansas‐type) Midcontinent cyclothem is an unconformity‐bounded package composed of a transgressive limestone, high‐stand core shale, regressive limestone, and a terrestrial outside shale (Heckel, 2002a) (Figure 3). Although the Kansas‐type cyclothem model worked well for the large packages on the shelf, smaller packages that do not fit the cyclothem model were also encountered. The model was modified to include three categories of Kansas‐type cyclothems; major, intermediate, and minor. Major cyclothems are recognized by the presence of widespread conodont‐rich black shale. Intermediate cyclothems are recognized by conodont‐rich gray shale that may be somewhat limited in extent. Minor cyclothems are thin intervals of marine deposits (lesser limestones and shales) that extend over short distances (Heckel, 1999). Lateral variation in cyclothems including basinal cyclothems (usually shale dominated and lacking limestones), mid‐shelf cyclothems (the Kansas‐type), and high‐shelf cyclothems (lacking transgressive deposits and having stronger evidence for subaerial exposure) was described to further explain geographical differences in lithology and unit thickness (Heckel, 1999). Biostratigraphic correlation was often used to determine the relationship between basinal and shelf cyclothems using conodonts and ammonoids from black shales that represented marine condensation during highstands (Boardman et al., 1995).
Middle and Late Pennsylvanian Sequence Stratigraphy Middle and Late Pennsylvanian deposits of the Midcontinent Basin are definitely cyclical in nature. Each unconformity bound cyclothem likely represents a high frequency sequence (fourth‐order cyclicity) (Rasbury et al., 1998). The development of each cyclothem from high shelf to basin can be modeled in terms of sequence stratigraphy rather than independent cyclothem models for the high shelf, mid shelf, and basin that depend on the aerial extent of the unit. Lower order cyclicity (potentially third‐order) is also apparent within the study interval. Diagrammatic models for the Lower Missourian Composite Sequence and the Middle Missourian Composite Sequence (including the high frequency sequences which make them up) can be
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found as Figures 4 and 5 respectively. Genetic Sequence Units (GSUs) of Watney et al. (1995) may imply even lower order cyclicity. This study interval falls within the Nuyaka Creek‐Muncie Creek GSU, but focus will remain on third‐ and fourth‐order cyclicity. The following is intended to be a brief overview of each of the high frequency sequences and their corresponding position within the lower order composite sequences of the study interval.
The Lost Branch Sequence The Lost Branch Sequence is a widespread deposit of limestones and shales recognized from the basin to the high‐shelf (Figure 3). The sequence is named after the Lost Branch Formation of Heckel (1991). The Lost Branch Sequence is the youngest sequence in the highstand sequence set of the Desmoinesian‐aged Marmaton Composite Sequence. The sequence boundary for the widespread Lost Branch Sequence is marked by the Dawson Coal and strong evidence of subaerial exposure where the coal is not present. The Dawson Coal is thickest in the Tulsa area of Oklahoma and thins to the north and south. Sections in Oklahoma reliably use the Dawson Coal as the base of the Lost Branch, but north into Kansas and Missouri it becomes discontinuous. Where the Dawson Coal is absent the blocky shale of the upper Memorial Shale is directly overlain by Lost Branch deposits. The contact between the upper Memorial Shale and the Lost Branch is distinguished by preserved underclays and well developed paleosols on the Kansas and Missouri shelves (Heckel, 1991). The lowest major marine unit is the Homer School limestone and its equivalents. In Oklahoma, the Homer School limestone caps a package of shale with a large terrestrial component likely representing the lowstand deposits of this sequence. The transgressive systems tract encompass the Homer School Limestone and the transition to the base of the dark gray to black facies of the Nuyaka Creek Shale. The Homer School Limestone south of Tulsa is roughly equivalent to the Sni Mills Limestone in northern Kansas and Missouri. At its thickest, the Homer School Limestone is about one meter thick and grades into calcareous shale to the north. On the shelf, the Sni Mills Limestone ranges from about 0.3 meters in thickness in northern Kansas to its eventual disappearance in Missouri and Iowa. The Sni Mills Limestone is more fossiliferous than the Homer School Limestone and bears a diverse open marine fauna (Heckel, 1991). The maximum flooding surface is the base of the dark gray to black facies of the Nuyaka Creek Shale. On the shelf, the base of the black facies is often marked by abundant phosphate
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nodules and a spike in conodont abundances. In the basin, this level is approximated using high conodont abundances, but is less recognizable lithologically. The highstand deposits include the dark gray to black Nuyaka Creek Shale, the overlying Upper Holdenville Shale and the Glenpool Limestone and its equivalents. The Glenpool Limestone varies in thickness throughout the Midcontinent Basin and is somewhat discontinuous owing to removal by the extreme erosional event that took place prior to deposition of the Hepler Sandstone on the shelf. The Glenpool Limestone is most continuous in Oklahoma. The Cooper Creek Limestone in northern Missouri and Iowa overlies the Nuyaka Creek Shale. At its thickest, the Cooper Creek Limestone is 2.4 meters thick, thinning to the south and east where it eventually grades into calcareous shale (Heckel, 1991).
The Hepler Sequence The Hepler (lower Pleasanton) Sequence (Figure 4) is a basinally restricted complex of sands, terrestrial shales and a thin section of marine limestones and shales (18 meters in its type region). The sequence is named after the Hepler Formation (Heckel and Watney, 2002) and includes the Hepler Sandstone, the Seminole Sandstone, the Checkerboard Limestone, and the South Mound Shale. The Hepler Sequence is restricted to the basin. The Hepler Sequence is the lowstand sequence set of the larger‐scale Lower Missourian Composite Sequence. Subaerial exposure at the top of the Lost Branch Sequence forms the lower sequence boundary of the Hepler Sequence. Lowstand deposits consist of the Seminole Sandstone in Oklahoma and the Hepler Sandstone in Kansas and states to the north. The transgressive surface, above these lowstand sandstones, is marked by the base of the Checkerboard Limestone. The Checkerboard Limestone splits into a lower and upper bed to the north. The lower bed represents the transgressive system tract of the cycle. The lower Checkerboard is typically a clean to shaly limestone approximately 0.3 meters in thickness (Heckel, 1992). The maximum flooding surface is recognized by a high concentration of conodonts formed by condensation in the lower portion the South Mound Shale. The South Mound Shale overlies the lower Checkerboard limestone and is marine shale up to 8.4 meters thick (Heckel and Watney, 2002). The portions of the South Mound Shale that underlie the conodont condensed horizon belong to the transgressive systems tract of this sequence. The highstand systems tract is composed of the portions of the South Mound Shale above the condensed horizon and the
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overlying upper bed of the Checkerboard Limestone. In its reference section the upper bed of the Checkerboard Limestone is 0.3 meters of skeletal limestone (Heckel and Watney, 2002).
The Shale Hill Sequence The Shale Hill (upper Pleasanton) Sequence is a widespread deposit of thin limestones and shale mapped from basin to high‐shelf that includes the Exline Limestone, the Mantey Shale, the Critzer Limestone, and the Guthrie Mountain Shale. The sequence is named after the Shale Hill Formation of Heckel and Watney (2002), also known as the Lower Tacket Formation of Oklahoma. The Shale Hill Sequence represents the transgressive sequence set of the Lower Missourian Composite Sequence. Subaerial exposure at the top of the underlying Hepler Sequence is the sequence boundary for the Shale Hill Sequence. The base of the Exline Limestone directly overlies this unconformity throughout most of the region and is an amalgamated sequence boundary and transgressive surface. The Exline Limestone is the first unit to successfully breach the shelf margin and extends from the basin in the south to the high shelf in the north. The transgressive systems tract includes the Exline Limestone and the overlying Mantey Shale. The Exline Limestone and Mantey Shale back‐step to the North and exhibit classic retrograde geometry. The Exline Limestone is an argillaceous fossiliferous limestone to calcareous crinoidal limestone that averages 0.3 meters in thickness. The Mantey Shale is sparsely fossiliferous, predominantly micaceous silty shale with localized sandstone at the top, and is up to 30 meters thick (Heckel and Watney, 2002). The base of the Critzer Limestone is the best candidate for the maximum flooding surface of the Shale Hill Sequence. The maximum flooding surface is recognized by a high concentration of conodonts when compared to the underlying Mantey and overlying Critzer Limestone and Guthrie Mountain Shales. The highstand systems tract of the Shale Hill Sequence consists of the Critzer Limestone and the overlying Guthrie Mountain Shale. The Critzer is a skeletal limestone to calcareous shale (ranging from a thin bed to nearly 2.7 meters thick) and is equivalent to the Bourbon Flags southeast of the type Critzer region. The Guthrie Mountain Shale is a gray, silty, micaceous shale that is up to 18 meters thick in its type region (Heckel and Watney, 2002).
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The Hertha Sequence The Hertha Sequence consists of the Mound City Shale (Lower Tacket Formation in Oklahoma) and the Sniabar Limestone (Middle Tacket Formation in Oklahoma). The sequence is named after the Hertha Limestone of Heckel and Watney (2002). The Hertha Sequence is the first sequence within the highstand sequence set of the Lower Missourian Composite Sequence. The sequence boundary is the exposure surface at the top of the Guthrie Mountain Shale. In Missouri, the Ovid Coal caps the Guthrie Mountain Shale. In Nebraska and Iowa, the blocky Guthrie Mountain exhibits red mottling along with localized coals indicative of subaerial exposure and paleosol development. In the southern portion of the study region, the Guthrie Mountain Shale exhibits sandy lenses that may be indicative of an exposure surface (Heckel and Watney, 2002). In many cases, the most distinctive horizon overlying the exposure surface is the highly phosphatic black facies of the Mound City Shale (Heckel and Watney, 2002). Throughout most of Kansas and Oklahoma, the base of the phosphatic black shale of the overlying Mound City Shale is an amalgamated sequence boundary‐transgressive surface‐maximum flooding surface. This surface is marked by a high concentration of conodonts (including the deeper water genus Gondolella). The black phosphatic facies of the Mound City Shale serves not only as the maximum flooding surface for the Hertha Sequence, but also for the Lower Missourian Composite Sequence. The Mound City Shale and the Sniabar Limestone make up the highstand systems tract for the Hertha Sequence. One probable explanation for the lack of lowstand and transgressive deposits and the overall aggradational geometry of the Hertha Sequence is the rapid sea level rise that would accompany a third‐order maximum flooding surface. The Mound City Shale consists of three members: a thin 0.1‐0.6 meter thick widespread black phosphatic shale, a thin 0.1 meter crinoidal limestone, and gray shale ranging from 0.6 to 8.4 meters thick (Heckel and Watney, 2002). The Sniabar Limestone is a skeletal to algal limestone ranging in thickness from 0.6‐6 meters. The base of the Sniabar Limestone near and around Uniontown Kansas exhibits characteristics of a minor flooding event indicated by the presence of a skeletal to oolitic calcarenite (Heckel and Watney, 2002). This localized flooding event is a parasequence within the overall Hertha Sequence.
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The Swope Sequence The Swope Sequence is the first sequence above the Lost Branch to exhibit the typical suite of limestones and shales associated with major cyclothems in the Midcontinent. The Swope Sequence is named after the Swope Limestone of Heckel and Watney (2002), and includes the Swope Limestone and the underlying Elm Branch Shale. The Swope Sequence is the uppermost portion of the highstand sequence set of the Lower Missourian Composite Sequence. The sequence boundary is the exposure surface on the top of the Sniabar Limestone of the underlying Hertha Sequence (Heckel and Watney, 2002). The lowstand systems tract for the Swope Sequence consists of the lower portions of the Elm Branch Shale. The lower Elm Branch Shale, at its type section, lacks fossils and is approximately 1.8 meters of gray mudstone containing small, irregular limestone nodules and includes an earthy limestone at its top (Heckel and Watney, 2002). The transgressive surface lies at the abrupt boundary between the non‐fossiliferous lower Elm Branch Shale and the fossiliferous upper Elm Branch Shale. The transgressive systems tract of the Swope Sequence is composed of the upper Elm Branch Shale and the Middle Creek Limestone. The upper Elm Branch, at its type section, is 0.75 meters of gray fossiliferous shale capped by the overlying Middle Creek Limestone (Heckel and Watney, 2002). The Middle Creek is a dark, dense limestone and ranges from 0.3 meters thick at its margin to 1.3 meters thick at the shelf edge (Heckel, 1992). Together these two units form a retrogradational geometry within the Swope Sequence. The maximum flooding surface is the base of the black Hushpuckney Shale Member of the Swope Limestone. The phosphate‐rich base of the Hushpuckney has an abundant conodont fauna indicative of condensation on the maximum flooding surface. The Hushpuckney Shale Member and Bethany Falls Limestone Member of the Swope Limestone compose the highstand system tract for the Swope Sequence. The Hushpuckney Shale ranges in thickness from 0.5 to 1.5 meters and varies in color from black to dark gray. The dark gray Hushpuckney Shale is found in southern Oklahoma as the Upper Tacket Formation of the Coffeyville Group (Heckel and Watney, 2002). On the shelf, condensation occurred within the Upper Hushpuckney prior to deposition of the Bethany Falls Limestone. This condensation horizon, marked by a dramatic increase in conodont concentration in the upper Hushpuckney, may be the result of decreased sedimentation during high accommodation conditions. The Bethany Falls Limestone ranges in
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thickness from 4.5 to 10.6 meters on the shelf and thins in its basinward extension as the top of the Upper Tacket Formation of Oklahoma. This exposure surface marks the upper sequence boundary of the Swope Sequence.
The Mound Valley Sequence The Mound Valley Sequence (Figure 5) is a basinally restricted package of non‐marine to marine shales and limestone. The sequence is named after the Mound Valley Limestone (Heckel and Watney, 2002) and consists of the Ladore Shale and the Mound Valley Limestone. It is also known as the Upper Coffeyville Group in Oklahoma. The Ladore Shale and Mound Valley Limestone are the lowstand systems tract of the Middle Missourian Composite Sequence. An exposure surface on the Bethany Falls Limestone that is marked by mottling and a distinctive package of oomoldic limestones (Heckel and Watney, 2002) is the sequence boundary for the Mound Valley Sequence and the Middle Missourian Composite Sequence. During deposition of the Shale Hill, Hertha, and Swope Sequences the basin had been relatively starved of sedimentation and developed a large amount of available accommodation space at the close of Swope Sequence deposition (Heckel and Watney, 2002). The Ladore Shale, the lowstand systems tract, is restricted to the basin by the Bethany Falls Limestone on the shelf margin. Ladore sedimentation occurred during the exposure event separating the Bethany Falls Limestone and the overlying Mound Valley Limestone. Over 18 meters of Ladore fills the basin to the south. Sandstone is commonly found within the Ladore package (Heckel and Watney, 2002). The base of the Mound Valley Limestone is the transgressive surface of the Mound Valley Sequence. The Mound Valley laps out onto the exposure surface on the Bethany Falls Limestone on the southern shelf indicating shelf‐ward migration of deposition. The Mound Valley is both the transgressive and highstand systems tract of the Mound Valley Sequence. The Mound Valley is typically only a few meters thick, but gets as thick as 9 meters in an algal mound facies at some locations (Heckel and Watney, 2002). An exposure of the Mound Valley Limestone southwest of Coffeyville, Kansas (see Figure 26 in Appendix A), splits into a lower and upper bed with an intermediate clay shale and black shale filling the gap. The base of the gray clay shale marks the maximum flooding surface of the sequence, but is absent where the algal facies dominates. The gray clay shale is the most conodont‐rich unit within the Mound Valley Sequence. The lap out of the Mound Valley onto the Bethany Falls Limestone is distinguished
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using the oomoldic nature of the upper Bethany Falls compared to the well preserved oolite of the Mound Valley.
The Dennis Sequence The Dennis Sequence is an aggrading to prograding package of limestones and shales named after the Dennis Limestone (Heckel and Watney, 2002). It is composed of the Galesburg Shale, the Canville Limestone, the Stark Shale, and the Winterset Limestone (Figure 5). The Dennis Sequence represents several important parts of the Middle Missourian Composite Sequence. Everything below the phosphatic black shale of the Stark Shale (including the Galesburg Shale and Canville and Lost City Limestones) belongs to the transgressive sequence set of the Middle Missourian Composite Sequence. The base of the phosphatic black shale of the Stark Shale is the maximum flooding surface for the Middle Missourian Composite Sequence. The remainder of the Stark Shale and Winterset Limestone form a portion of the highstand sequence set of the Middle Missourian Composite Sequence. The sequence boundary is marked by an exposure surface on top of the Mound Valley Limestone (Heckel and Watney, 2002). The lowstand systems tract consists of the Galesburg Shale. The Galesburg is 0.6 to 3.6 meters of gray mudstone on the shelf, but thickens to as much as 39 meters basinally where it is the upper portion of the Coffeyville Group (Heckel and Watney, 2002). Within the Galesburg is the Cedar Bluff Coal. This coal unit is seated in the middle of the Galesburg with well developed underclay (Heckel, 1992). The Cedar Bluff Coal indicates subaerial exposure in this portion of the Galesburg Shale. The overlying Galesburg interval has localized sands near its top as well as the Davis City Coal in the northern portion of the study region (Heckel, 1992). The coals present within the Galesburg Shale may indicate the presence of several high frequency sequences or localized regression events. The base of the Canville Limestone is the transgressive surface for the Dennis Sequence. The Canville Limestone is typically less than a meter of dense, crinoid‐rich, phosphatic limestone. In some regions, the Canville reaches up to 6 meters in thickness where it is primarily algal in nature (Heckel and Watney, 2002). In the Tulsa area, the Canville is equivalent to a massive algal mound complex known as the Lost City Limestone. The Lost City is estimated to be near 20 meters in overall thickness (Heckel, 1992). The Canville Limestone and the lower non‐ black facies of the Stark Shale make up the transgressive system tract for the Dennis Sequence.
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The phosphatic base of the black Stark Shale or the equivalent base of the conodont‐rich clay shale overlying the Lost City Limestone is the maximum flooding surface of the Dennis Sequence. The highstand systems tract for the Dennis sequence is composed of the Stark Shale and overlying Winterset Limestone (Lower Winterset Limestone of Heckel and Watney, 2002). The Stark Shale ranges in thickness from 0.3 to 1.8 meters; in thicker sections it has lower clay shale and upper gray shale beds (Heckel and Watney, 2002). The condensed conodont‐rich horizon in the Stark Shale is at the base of the phosphatic black facies. The Winterset Limestone is a highly variable unit. In much of the region, it is eight to ten meters thick, but thickens up to an additional twenty meters in some localities on the shelf margin. The Winterset is primarily algal limestone and contains conodont‐rich gray shales in its lower portions (Heckel and Watney, 2002, Heckel, 1992). Within the Winterset several prograding parasequences have been recognized indicating that regression of the sea during highstand was interrupted at several times by flooding events (Felton and Heckel, 1996).
The Hogshooter Sequence The Hogshooter Sequence is an aggradational limestone with lesser included shales that sits on the exposure surface at the top of the underlying Dennis Sequence. The Hogshooter Sequence is named after the Hogshooter Limestone (Heckel, 1992). The Hogshooter Limestone is also referred to as the Upper Winterset Limestone in some literature (eg. Felton and Heckel, 1996). The Hogshooter Sequence represents an aggradational package that is a portion of the highstand sequence set of the Middle Missourian Composite Sequence. The outcrops on the northbound lanes of US 69 north of the exit for Jingo represent the best exposure of the Hogshooter Sequence (see Figure 23B in Appendix A). At Jingo, the sequence boundary is the exposure surface on top of the Winterset Limestone (the Mid Winterset Unconformity of Felton and Heckel, 1996). The lowstand systems tract is a thin interval (25 cm) of non‐fossiliferous gray and black shale. The predominantly algal limestone between this lower non‐fossiliferous shale and the overlying, informally named “Jingo Shale Bed” represents the transgressive system tract (105 cm). The transgressive surface is represented by the lower condensed portion of the limestone. The maximum flooding surface at Jingo is represented by the base of the fossiliferous gray Jingo Shale in most shelf localities. The
Jingo Shale is known for a concentration of Adetognathus P1 elements. The bulk of the Jingo
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Shale (20 cm) and the overlying algal limestone (180 cm) comprise the highstand system tract of the Hogshooter Sequence. In most basinal sections, the Hogshooter Sequence is characterized by an extremely condensed phosphatic limestone that overlies portions of the underlying Dennis Sequence and develops into a large algal mound nearly seven meters thick at its type section (Heckel, 1992). This condensed phosphatic interval marks the first appearance of the conodont genus Streptognathodus. At Ramona, the Hogshooter shows an onlapping relationship to the underlying Winterset mound. At Ochelata, the base of the Hogshooter is a part of a 20 cm ledge in which the lower ten centimeters has a conodont fauna similar to the Dennis Sequence and the upper ten centimeters has a conodont fauna characteristic of the Hogshooter Sequence, including Streptognathodus. South of Hogshooter, the base of the Hogshooter Sequence is a phosphatic lag at the top of the Stark Shale. In other localities, the Hogshooter may lie directly on the deposits of the Coffeyville Group. The erosional base of the Hogshooter in Oklahoma has not been completely characterized throughout the basin; the exact evolution and third order significance of this surface requires more detailed study of basinal sections in Oklahoma.
The Cherryvale Sequence The Cherryvale Sequence is a prograding package of shales and limestone that is named after the Cherryvale Formation (Heckel and Watney, 2002). The sequence consists of the Fontana Shale, Block Limestone, Wea Shale, and the Drum/Westerville Limestone. The Cherryvale Sequence is a progradational package within the highstand sequence set of the Middle Missourian Composite Sequence. Evidence suggests that the extent of the overlying Nellie Bly Formation and its erosion of the Cherryvale Sequence are indicative of low accommodation space. The exposure surface at the base of the overlying Fontana Shale marks the sequence boundary of the Cherryvale Sequence. Heckel and Felton (1996) indicate some paleosol development within the base of the overlying Fontana Shale at Jingo. The lowstand systems tract of the Cherryvale Sequence is composed of the Fontana Shale. The Fontana Shale ranges in thickness from 1.5 meters in the north to over 5 meters in southern Kansas, and up to over 22 meters near Cherryvale, Kansas. The lower package of the Fontana is commonly gray mudstone with small carbonate nodules. Near‐shore black facies occur as the shale becomes increasingly marine in nature to the top (Heckel and Watney, 2002).
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The base of the Block Limestone is the transgressive surface for the Cherryvale Sequence. Abundant conodonts are recovered from the Block Limestone throughout its type region. The Block Limestone represents the transgressive systems tract of the Cherryvale Sequence. The Block Limestone ranges from 0.3 to 1.5 meters in thickness, thinning to the north and south of its type area (Heckel and Watney, 2002). In the southern portions of the study region the Block Limestone is absent. The Lower Shale Member (undifferentiated Cherryvale) represents both Fontana and Block Deposition (Heckel and Watney, 2002). A Zone of high conodont abundance can be picked up in Oklahoma in the lower shale that is likely equivalent to the Block Limestone. Where the Block Limestone is absent in Oklahoma the Lower Shale Member is included in the New Harmony Shale of Bennison (1984). The basal fossiliferous portion of the Wea Shale is the maximum flooding surface for the Cherryvale Sequence. The basal Wea Shale overlies the Block Limestone with a similar conodont fauna and abundance. The Wea Shale and Westerville‐Drum Limestone make up the highstand systems tract of the Cherryvale Sequence. The Wea Shale ranges from 0.9 meters to over 8 meters in thickness (Heckel and Watney, 2002). In the southern portions of the study region, the conodont‐rich portion of the lower shale may be a combined transgressive and highstand package containing Block‐Wea conodonts. The bulk of the Wea Shale represents a portion of the highstand system tract of the Cherryvale Sequence. The Wea becomes a flaggy limestone‐shale interbedded unit in southern Kansas known as the Middle Flaggy Member (Heckel and Watney, 2002). In Oklahoma the Wea Shale is equivalent to the New Harmony Shale of Bennison (1984). The New Harmony Shale contains abundant conodonts and overlies an encrinite positionally equivalent to the Block Limestone. The major limestone making up the remainder of the highstand deposits for the Cherryvale Sequence includes two geographically distinct but positionally equivalent units. The Drum Limestone (southern Kansas) is as much as 18 meters in thickness and is predominantly oolitic in nature, but is only a little over one meter thick at its reference locality (Heckel and Watney, 2002). The Drum Limestone is known for a peculiar conodont fauna consisting of only small‐sized conodonts (Merrill and Powell, 1980). The Westerville Limestone (northern Kansas) is 2.4 meters thick near its reference locality in Kansas and thins to near two meters in the south. As with the Drum Limestone, the Westerville is known for well developed oolite facies near the middle of its exposure (Heckel and Watney, 2002). Erosion has removed the limestone
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member throughout most of central Kansas, leading to the two geographical names for limestones that are most likely equivalent.
The Dewey Sequence The Dewey Sequence is a widespread sequence named after the Dewey Limestone (Heckel and Watney, 2002) and includes the Dewey Limestone and the underlying Nellie Bly Formation. The Dewey Sequence is the last in the highstand sequence set of the Middle Missourian Composite Sequence and represents deposition in low accommodation conditions. The major unconformity at the base of the overlying Chanute Shale is the sequence boundary for the overlying Muncie Creek High Frequency Sequence and the Upper Missourian Composite Sequence. The sequence boundary for the Dewey Sequence is the erosional unconformity at the base of the Nellie Bly Formation. The Nellie Bly is a complex of sandstone to sandy shale extending from the shelf of Kansas (poorly exposed and often confused with the overlying Chanute Shale) to the basin of Oklahoma (35‐45 meters thick) (Heckel and Watney, 2002). Nellie Bly sediments fill much of the basin during this lowstand phase. The amalgamated transgressive and maximum flooding surface for the Dewey Sequence is the Quivira Shale. The phosphatic base of the Quivira has a diverse and abundant conodont fauna, including members of the genus Gondolella. Heckel and Watney (2002) report local limestone and clay between the Quivira and underlying Nellie Bly that could potentially preserve the transgressive deposits of the Dewey Sequence. This thin limestone is referred to as the Pammel Park Limestone by Heckel and Pope (1992) and was informally named the Wekiwa Limestone by A. P. Bennison (Heckel, 1992). The Quivira Shale and overlying Cement City Limestone make up the highstand system tract of the Dewey Sequence. The Quivira Shale overlies the Nellie Bly Formation where it has not been removed by Chanute erosion. The Quivira Shale is a gray to black marine shale that contains abundant conodonts. In Kansas, the Quivira Shale is 0.6 to 1.5 meters in thickness (Heckel and Watney, 2002). Thicknesses of over two meters are common in the basinal sections of Oklahoma. The Cement City Limestone ranges in thickness from 1.8 to 2.4 meters throughout most of the study region (Heckel and Watney, 2002). Near Dewey, in Oklahoma, the Cement City forms a large 9‐meter‐thick algal mound (Heckel, 1992).The Cement City is truncated by the overlying Chanute Shale. The Chanute Shale cuts down through the underlying Dewey and in
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some cases Cherryvale sequences in the basin and marks deposition above the erosional unconformity at the sequence boundary for the overlying Muncie Creek Sequence.
17
Panthalassa Sea Uralian Highlands
Russian Platform Midcontinent ea ehUiest,, University, Tech Texas MB 18 MdB AB DB Sea Carnic Alps
ApB Caledonian Highlands EQUATOR Tethys Sea tvnJ oso uut2008 August Rosscoe J. Steven
Appalachian-HercynianHighlands km 1000 0 mi 600
Figure 1: Paleogeography of the Laurasian portion of Pangaea during Middle and Late Pennsylvanian time at sea level highstand. Land is represented by the gray color with a black outline showing the current shape of the continents. AB=Anadarko Basin; MdB=Midland Basin; ApB=Appalachian Basin; DB=Donets Basin; MB=Moscow Basin. Modified from Heckel (1999). Texas Tech University,Steven J. Rosscoe , August 2008
Sioux Falls
IOWA Cedar Rapids Des Moines NEBRASKA FCQ* PWA* EP* Lincoln
Forest City Basin Salina Nemaha Uplift Basin Topeka Kansas City KAW * *BR Jefferson City KANSAS St Louis Bourbon Arch J69* UW* MISSOURI US69 Wichita Shelf UT * Basin BC * KM**MV DR *SM Springfield CSW *TM* LCC* HQ OCH *HS *NH SD * * Cherokee RR Basin/Plaform ZR* * 71-75* Tulsa SE***SSP TC Oklahoma City * *MR HFM ARKANSAS OKLAHOMA *LR * Little Rock CC* *SS
miles Wichita Falls 0 50 100
Figure 2: Regional geography of the Midcontinent Basin, North America. Localities are marked by an asterisk and the locality abbreviation. Exact locations (GPS or PLS) can be found in Appendix A, along with the locality abbreviations and selected measured sections. 19 Texas Tech University,Steven J. Rosscoe , August 2008
Lithology Cyclothems Sequences
Hepler - Lower Outside Lowstand System Seminole Shale/Sandstone Tract (LST) Sandstone
Sequence Boundary Upper Outside Shale
Glenpool Regressive Limestone Limestone
Highstand System Tract (HST)
Core Shale Nuyaka Creek Black Shale Max Flooding Surface
Trangressive System Homer Transgressive Tract (TST) School Limestone Limestone Trangressive Surface Lower Lowstand System Tract Dawson Coal Outside Shale Sequence Boundary
Figure 3: Model of the typical Kansas-type cyclothem for the Lost Branch Cyclothem (High Frequency Sequence). This model does not accurately portray the true thickness of units from the Lost Branch, measured sections from the Lost Branch can be found in Appendix A. Sequence stratigraphic terminology is found in italics on the diagram to aid in transition between cyclo- and sequence stratigraphy. See Appendix A, Figure 17 for lithology symbols. 20 South OK KS North SB Swope HFS HSS Bethany Falls LS Hertha HFS MFS Shale Hill HFS TSS Hushpuckney SH TS LSS Middle Creek LS SB SB HSS MFS Elm Branch SH TSS TS Sniabar LS Hepler HFS LSS Mound City SH SB Guthrie Mtn. SH Critzer LS Mantey SH Exline LS Hepler SS ea ehUiest,, University, Tech Texas 21
Bethany Falls LS Upper Checkerboard LS Hushpuckney SH South Mound SH Mound City SH Lower Checkerboard LS Exline LS 2008 August Rosscoe J. Steven
Seminole SS
Figure 4: Diagrammatic model of the Lower Missourian Composite Sequence. This is a general model that illustrates the relationships between different units in the study region. Actual truncations, thickness, and regional features may vary. For detailed subsurface maps of this interval see figure 2 of Heckel and Watney (2002). Inset shows the rough arrangement of the component high frequency sequences (HFS). Abbreviations are: Shale (SH), Sandstone (SS), Limestone (LS), Sequence Boundary (SB),Transgressive Surface (TS), Max Flooding Surface (MFS), Highstand Sequence Set (HSS), Transgressive Sequence Set (TSS), Lowstand Sequence Set (LSS). See Appendix A, Figure 17 for lithology symbols. South OK KS North
Drum LS Cement City LS Quivira SH Cement City LS Westerville LS Quivira SH Wea SH Block LS Nellie Bly SH Fontana SH Hogshooter LS Wea SH Winterset LS
Fontana SH Stark SH Canville LS Davis City Coal Galesburg SH
Hogshooter LS , University, Tech Texas
22 Stark SH Mound Valley Limestone Ladore SH Canville LS
Cedar Bluff Coal SB SB Dewey HFS Galesburg SH Cherryvale HFS HSS Hogshooter HFS
HSS 2008 August Rosscoe J. Steven Dennis HFS MFS TS TSS LSS MFS SB TSS TS LSS Mound Valley HFS SB
Figure 5: Diagrammatic model of the Middle Missourian Composite Sequence. This is a general model that illustrates the relationships between different units in the study region. Actual truncations, thickness, and regional features may vary. Detailed subsurface maps of this interval see figure 21b of Heckel and Watney (2002). Inset shows the rough arrangement of the component high frequency sequences (HFS). Abbreviations are: Shale (SH), Sandstone (SS), Limestone (LS), Sequence Boundary (SB),Transgressive Surface (TS), Max Flooding Surface (MFS), Highstand Sequence Set (HSS), Transgressive Sequence Set (TSS), Lowstand Sequence Set (LSS). See Appendix A, Figure 17 for lithology symbols. Texas Tech University, Steven J. Rosscoe, August 2008
CHAPTER 2 MATERIALS AND METHODS
Sample Collection, Preparation, and Presentation Samples from each of the localities shown in Figure 2 were collected and brought to Texas Tech University by Steven Rosscoe, Jim Barrick, Darwin Boardman, and Peter Holterhoff. Most samples were broken down by Steven Rosscoe, while previously recovered samples were processed by Jim Barrick and Darwin Boardman. Collections from Phil Heckel and John Pavlicek were also studied for comparison, but are not included in the data set for this study. Measured sections and sampling sites can be found in Appendix A. Carbonate samples were broken down using buffered formic acid. Clay shale samples were broken down using white kerosene. Black and gray shale samples were broken down using the traditional bleach method and the updated hydrogen peroxide method (see Appendix C). Large residues were further processed by use of tetrabromoethane heavy mineral separation. The conodont‐bearing residues were picked and representative conodonts were selected for imaging by scanning electron microscope. Conodonts exhibiting unique and common variations were selected for imaging to accurately document as much of the variability within the group as possible. Revised taxonomic descriptions have been completed using the anatomically referenced terminology presented by Purnell et al. (2000). This anatomical terminology is illustrated in Figure 6. Terminology specific to observed variation will be defined and illustrated later in this chapter. All specimens illustrated for taxonomic purposes will be oriented according to convention with the dorsal end of the element toward the page bottom and the ventral end toward the page top.
Function‐Based Taxonomy Splitting into narrowly defined species with small‐scale variability or grouping into species with high variability can both be seen as valid morphological interpretations in conodont taxonomy. As with any extinct fossil group, splitting and grouping conflicts arise from the paleontological definition of species. To paleontologists, taxonomy is typically limited to unique morphological variations that can be easily distinguished from other morphological variations. With conodonts like Idiognathodus there is not only an understanding of the oral apparatus, but
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also an understanding of the function of the P1 elements that are most commonly used to define species. With Idiognathodus it is possible to rank the significance of variation and to better choose characters that will be used to define species and subspecies. The variation that is seen in Idiognathodus must work within a relatively small framework of characters. Each P1 element consists of a blade, a platform, and up to two accessory lobes (caudal and rostral). Despite the apparent morphological complexity of the group, it is the simple modification of these three to four component parts that gives rise to most variation. Factors affecting the variability of these elements can be split into two types; functional and environmental. Functional variation is driven by the modification of the function of the element, whereas environmental variation is attributed to local environmental regimes within the larger Midcontinent Basin. It is the combined effects of these two sources of variation that is responsible for the success of recognition of cycles by patterns in the distribution of Idiognathodus morphotypes.
Function of P1 Elements in Idiognathodus
Resolving the function of the P1 element in Idiognathodus is a robust area of research pioneered by conodont workers in the United Kingdom. The flat platform of Idiognathodus brought many inevitable comparisons to molar teeth in modern organisms. Purnell (1993, 1994) used growth rates to differentiate between the suspension feeding and grasping models of feeding that had been proposed. In both models the P1 element of Idiognathodus behaves as a crushing or bruising mechanism for food brought into the oral cavity. The comparison to molar teeth was enhanced by similarity in the positive allometric growth exhibited by both molar teeth and Idiognathodus P1 elements (Purnell, 1993; Purnell, 1994).
The role of the Idiognathodus P1 element as a crushing and bruising mechanism was further corroborated by the discovery of microwear facets on the platform similar to microwear facets in molar teeth (Purnell, 1995). Research into the function of the P1 element reached its conclusion with the publication of a natural pair of Idiognathodus P1 elements that were imaged in opposition, showing compatible wear patterns on opposing elements and the molar‐like occlusion of the elements (Donoghue and Purnell, 1999). P1 elements in Idiognathodus functioned in a manner similar to molar teeth. Opposed elements occlude and process food during a power‐stroke by crushing and bruising the food.
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Selection of Significant Characters in Idiognathodus
The typical P1 element in Idiognathodus is flat with a highly ornamented ventral platform and a dorsal platform ornamented with transverse ridges that tapers to a dorsal tip (Figure 6). The ventral platform is the side most expanded in the rostro‐caudal direction (also the direction of food flow through the oral cavity). The concentration of surface area and ornamentation suggests that the ventral platform is the most functionally significant portion of the P1 element. Accessory lobes are the most significant features of idiognathodids in this study. Changes in the size and shape of these lobes directly affect surface area of the element and can add length in the dorsal direction to the highly ornamented area of the lobe. Food flow from the rostral portion of the element to the caudal portion of the element places a higher significance of variation on the rostral lobe than on the caudal lobe.
Transverse ridges cross the dorsal platform of the typical Idiognathodus P1 element. When complete, the transverse ridges allow for a roughness that is relatively reduced from the roughness provided by the ornamentation on the ventral part of the platform. Modification of the transverse ridges can change the surface roughness of the dorsal platform. Modification to the central part of the dorsal platform, rather than its margins, will have a major effect on element function. Modification of surface roughness reduces the overall contact of the P1 element with the food, but focuses the energy of occlusion over a small specific area to increase the functional efficiency of the element (Donoghue and Purnell, 1999). The variations described above are ranked in order of functional significance from variations of the rostral lobe, then the caudal lobe, then platform ornamentation, and finally overall element size, shape and lesser characters (discussed later in this chapter). It is from this order of functional significance, that a hierarchical model of taxonomy for Idiognathodus has been constructed. The model of Idiognathodus taxonomy allows for the generation of species groups, species, subspecies, and morphotypes in a strict order that will allow for taxonomic stability to the level of species. Size and shape of the rostral lobe will directly affect the surface area of the functionally significant central platform and can be used to define species groups and species. Size and shape of the caudal lobe will also directly affect the functional surface area of the element, but the number of possible caudal lobe variations is much reduced when compared to the number of variations in the rostral lobe. Variation in the caudal lobe accounts for a secondary division into species.
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The number of possible ornamentation styles on the oral surface of the platform is quite high, but the frequency and occurrence of these variations is commonly erratic. These variations, when of significant frequency, can be used to define species. In addition, when significant within a species, they may be used to define subspecies. It has been suggested that some of this variation may be tied to geographic or depositional conditions (Rosscoe and Barrick, In Press). Better understanding of the mechanisms controlling these variations may enhance their usefulness in future work.
Functionally Significant Characters The following will provide a brief description of the major morphological features identified in the genus Idiognathodus in this study. The descriptions are intended to guide the reader to interpret the best placement of observed variation into this schematic. Over one thousand conodonts were imaged by scanning electron microscope and analyzed for variation. The following list represents the most significant morphologies gleaned from this data set. These variations are illustrated in Figure 7.
Restricted Rostral Lobe (Figure 7A): A small rostral lobe restricted to the ventral quarter of the platform by the ventral‐most transverse ridge.
Moderately Restricted Rostral Lobe (Figure 7B): A moderately sized rostral lobe that has a small dorsal extension beyond the first one, maximum two, transverse ridges.
Expanded Rostral Lobe (Figure 7C): A rostral lobe that is expanded in the dorsal direction up to one‐half the length of the platform.
Elongate Rostral Lobe (Figure 7D): The most elongate rostral lobe in the dorsal direction, extending between one‐half and the entire length of the platform. The lobe also expands in the rostral direction with at least two rows of nodes on the ventral portion of the lobe. Usually only a single row of nodes ornaments the dorsal portion of the lobe.
Reduced Rostral Lobe (Figure 7E): A narrow rostral lobe containing a single row of ornamenting nodes that extends up to one‐third the length of the platform in the dorsal direction.
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Reduced Elongate Rostral Lobe (Figure 7F): A narrow lobe containing a single row of ornamenting nodes extending beyond one‐third the length of the platform in the dorsal direction.
Inset Rostral Lobe (Figure 7G): A small rostral lobe with room for only one or two nodes that forms at the inflexion point where the rostral margin of the element joins the rostral adcarinal ridge.
Ghost Rostral Lobe (Figure 7H): A rostral unornamented lobe‐like extension that is distinctively separate from the main body of the platform.
Missing Rostral Lobe (Figure 7I): A rostral margin lacking any rostral or ghost rostral lobe.
Robust: A modifying term for expanded, moderately restricted, and restricted rostral lobes for highly developed lobes with a large amount of ornamentation that is expanded in the rostro‐ caudal direction.
Continuous: A modifying term for expanded, moderately restricted, and restricted rostral lobes for rostral lobes that do not expand in the rostro‐caudal direction and form a lobe margin that is continuous with the platform margin.
Protruding: A modifying term for expanded, moderately restricted, and restricted rostral lobes for rostral lobes that expand in the rostro‐caudal direction and form a lobe margin that protrudes from the platform margin.
Normal Caudal Lobe (Figures 7A‐7I): A caudal lobe that expands in the caudal direction so that it can hold more than two nodes along its rostro‐caudal axis. The lobe is nearly as rostro‐caudally expanded as it is in the dorso‐ventral direction.
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Reduced Caudal Lobe (Figure 7J): A caudal lobe that is elongate in the dorso‐ventral direction with room for a maximum of two nodes (typically as a part of fused node ridges) in the rostro‐ caudal direction.
Inset Caudal Lobe (Figure 7K): A small caudal lobe with room for only one or two nodes that forms at an inflection point between the caudal margin of the element and the caudal adcarinal ridge.
Ghost Caudal Lobe (Figure 7L): A caudal unornamented lobe‐like extension that is distinctively separate from the main body of the platform.
Missing Caudal Lobe (Figure 7M): A caudal margin lacking any caudal or ghost caudal lobe.
Ventrally Shifted Lobe (Figure 7N): A P1 element where the caudal lobe is shifted in the ventral direction, up to one‐half the length of the caudal lobe is ventral of the ventral termination of the rostral lobe.
Complete Transverse Ridges (Figures 7A‐7N): A platform that bears complete transverse ridges from the rostral to caudal margins. These ridges may be oriented along with the rostro‐caudal axis, at an angle to the rostro‐caudal axis, or show a deflection in the ventral direction on the caudal portion of the platform.
Marginal Grooves (Figure 7O): A disruption of all transverse ridges along the rostral or caudal margin of the platform in the form of a groove. The caudal marginal groove is most common, and can occur alone. The rostral marginal groove is less common and only occurs in specimens with a caudal marginal groove.
Rostral Eccentric Groove (Figure 7P): A disruption of all transverse ridges on the rostral portion of the platform from the rostral side of the medial carina to the dorsal margin of the platform. Only found when there is a caudal eccentric groove.
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Caudal Eccentric Groove (Figure 7Q): A disruption of the all transverse ridges on the caudal portion of the platform from the caudal side of the medial carina to the dorsal margin of the platform. May form independent of a rostral eccentric groove.
Medial Groove (Figure 7R): A disruption of transverse ridges from the dorsal tip of the medial carina to the dorsal tip of the platform. Will form as either a complete medial groove (disrupts all transverse ridges) or a partial medial groove (disrupts only the ventral‐most transverse ridges).
Medial Nodosity (Figure 7S): A row of nodes disrupting all transverse ridges from the dorsal tip of the medial carina to the dorsal tip of the platform. In cases where medial nodosity does not extend to the dorsal tip of the platform it may be referred to as partial medial nodosity (for uniform node diameters) or dribbling nodes (for decreasing node diameters dorsally).
Chaotic Disruption (Figure 7T): A platform exhibiting incomplete transverse ridges throughout the entirety of the platform. Raised features form along the trends of the transverse ridges but are expressed as individual short ridges or nodes.
Nodose Platform (Figure 7U): A platform that is completely ornamented with discrete nodes. Typically, the nodes do not show any preferred orientation.
Elongate Medial Carina (Figure 7V): The normal extension of medial carina is less than one‐ quarter the length of the platform. Any extension beyond one‐quarter the length of the platform is considered elongate. It is necessary that the degree of elongation is characterized by the portion of the platform length through which the carina extends.
Lesser Characters
Certain variability in Idiognathodus P1 elements in the study interval may not be easily explained as variations of pure function. Some of this variability may be tied to geographic and depositional environments at the time of deposition. At present, within the study interval, the variations discussed here have not been observed to be true species‐level indicators, but in
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some cases may serve some utility at the subspecies or morphotype level. As such, in the hierarchical model these variations have the lowest rank (Rosscoe and Barrick, In Press). Environmental variation is more difficult to explain than functional variation, but can be assessed by evaluating the functional value of the observed variation. Variation further away from the ventral platform and at the margins of the dorsal platform is less likely to affect the function of the typical P1 element of Idiognathodus. Environmental variation can also be observed by looking at small scale variations between lithologic units within a sequence and those tracking facies shifts within units in transects across the region. At present it has become clear that a true paleoecological study of these conodonts is necessary to understand the true distribution of these variations, and is too large an endeavor to fall into the scope of this study.
Overall Element Shape
The shape of the ventral portion of the P1 element is derived from the shape and size of rostral and caudal accessory lobes. The dorsal margins may be pointed (Figure 7b), subrounded (Figure 7a), and rounded (Figure 7Z). The shape of the dorsal margin exhibits at least some correlation with the style of accessory lobes present. Robust, protruding lobes often accompany pointed dorsal margins, while smaller rostral lobes and more elongate caudal lobes are associated with subrounded and rounded dorsal margins. Variation of the dorsal margin has a limited effect on element surface area and length, with no effect on surface roughness. There is some evidence that variation in the dorsal margin may be tied to environment of deposition. Lost Branch Sequence specimens of Idiognathodus expansus exhibit a predominantly pointed dorsal margin in the Homer School Limestone (transgressive limestone). Specimens of I. expansus develop a subrounded to rounded dorsal margin in the Nuyaka Creek Shale (highstand core shale). A return to dominance of the pointed dorsal margin occurs again in the Glenpool Limestone (regressive limestone). This pattern of variation suggests a relationship to depositional environment.
Element Size
There is an apparent relation of P1 element size in Idiognathodus to magnitude of cyclicity and environments of deposition. Shallow‐water limestone deposits are notorious for conodonts that are reduced in overall element size. The Drum Limestone in southern Kansas is the best example of this (Merrill and Powell, 1980). Deep‐water deposits (core shales, etc.) have
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an abundance of large forms. It can be observed that this difference is not purely an effect of sample size as the relative proportions of large to small elements are skewed in favor of deep water deposits. A similar relationship can be observed on the scale of Pennsylvanian cycles. The Hertha and Swope sequences of the Lower Missourian Composite Sequence all have a relative abundance of large forms and represent the most widespread high frequency sequences of the composite sequence. The least widespread high frequency sequences, the Hepler and Shale Hill, have a relative abundance of smaller forms. The cause for this observed variation in element size has not yet been investigated thoroughly, but Heckel (1999) believes that larger size may reflect the environmental stability and steady food supply in offshore regions relative to less environmentally stable near‐shore regions. Size differences could also be a result of taphonomic processes.
Number of Transverse Ridges In the past, the number of transverse ridges on the platform has been used to aid in species designation. This use needs to be carefully examined before it is employed within the functional hierarchy presented in this study. A simple relationship between element size and the number of transverse ridges can be recognized in many cases. Smaller elements tend to have fewer transverse ridges than their larger counter parts. The implication of an ontogenic increase in ridges removes the functional significance of this variation with respect to taxonomic work. Other examples have shown variation in the number of transverse ridges between specimens of similar size. In these cases, there is an implied functional value in that the more transverse ridges on a platform the more surface roughness is available to aid in food processing. The difficulty in separating ontogenic and functional variation in the number of transverse ridges places this variation on the low end of the taxonomic hierarchy established in this study.
Ornamentation Style During the course of this study it became apparent that the style of ornamentation on the ventral platform and accessory lobes is highly variable. Ornamentation is in the form of discrete hemispherical nodes in most cases. Nodes forming fused node rows and even lobes ornamented with crenulated ridges have also been observed. There is a potential relationship between depositional environment and the style of ornamentation. In some sequences, those conodonts found in limestones appear to have more discrete nodes than those found in shales.
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There may also be an ontogenic relationship, in that the smallest and largest conodonts tend to have the least discrete nodes while intermediate specimens appear to have the most discrete. Evaluation of ornamentation is also hampered by taphonomic processes. Taphonomic wear on the oral surface of the element may artificially reduce the discreteness of ornamentation. Other patterns of ornamentation include circular arrangements of nodes, alignment of nodes on accessory lobes with the transverse ridges of the central platform, and alignment of nodes with the margins of the accessory lobes. No discernable pattern in ornamentation has been uncovered that could directly link with differentiation of species. In each of these cases, the functional value is suspect. The link between change in surface area and surface roughness and the style or pattern of ornamentation has not been adequately studied.
Adcarinal Ridges The length of the ventral extensions and the flaring nature of adcarinal ridges are often noted in descriptions of conodont species, but their functional value is questionable. As the platform is the powerhouse of food processing anything ventral of the platform will have a significantly reduced functional value. The effect of these ventral extensions should have little effect on the efficiency of the platform to crush and bruise food particles. When adcarinal ridges extend as features onto the platform they may play a more significant role. In general, smaller caudal lobes are associated with the involvement of the adcarinal ridge in ornamenting the lobe. Larger rostral lobes often incorporate the adcarinal ridge into the ventral margin of the lobe as ornamentation and a major high‐elevation feature. From the Desmoinesian to the Missourian there is a trend in increased length and flaring of the adcarinal ridges that can be seen in the specimens illustrated in Appendix B.
Application to the Genus Streptognathodus As originally defined by Stauffer and Plummer (1932) the genus Streptognathodus is characterized by presence of a “deep axial furrow,” more commonly known as a troughed platform. A trough is not a groove. A troughed platform must have high elevated margins and the platform must decrease in elevation to the central axis of the element. In most cases, a troughed platform is grooved along the central axis, but this is not necessary. If the overall platform is flat in elevation with a groove, it is still considered a member of the genus Idiognathodus.
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In the Idiognathodus model troughing of the platform will reduce the overall surface roughness of the platform causing a reduction in the functional efficiency of the central platform and focus functional processes on the rostral and caudal margins of the platform. Streptognathodus troughing is not just modification of an Idiognathodus platform, but is more likely an indicator of an entirely different feeding strategy. Troughing developed time and again in idiognathodid conodonts (ex: Swadelina and Streptognathodus) suggesting that a trough is not a negative adaptation as would be suggested by the Idiognathodus model. Troughing of the platform eliminates virtually all of the modifications of platform ornamentation seen in the Idiognathodus model. Streptognathodus exhibits similar variation in rostral and caudal lobes in the Idiognathodus model, so the hierarchy of lobe variation will remain the same as seen in the Idiognathodus model. The function of a trough is poorly understood and relatively unstudied, so a functional significance cannot be placed on the variability of a trough. However, because the trough is the diagnostic character of the genus the type of trough variation will be given the highest level in the taxonomic hierarchy. Variation of the trough is the primary character used in differentiating species of the similar genus Swadelina (Lambert et al., 2003).
Additional Characters for Streptognathodus
Weak Trough (Figure 7W): A platform that has elevated margins and decreases in elevation to center of the element. In this case transverse ridges remain complete across the platform.
Ridged Trough with Groove (Figure 7X): A platform with elevated margins that decreases in elevation to the center of the element. The central axis of the platform is marked by a deep, well‐defined groove. The sides of the platform retain transverse ridges.
Wide, Smooth Trough (Figure 7Y): A platform with elevated margins that decreases in elevation to the center of the element. Transverse ridges are present only at the very margins of the platform, while the central portion of the platform is dominated by a wide and smoothed trough basin.
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Sinistral Dextral Caudal Blade Adcarinal Ventral Ridge Rostral Adcarinal Ridge Medial Carina Rostral Lobe Caudal Lobe
Dorsal Platform with Rostral Caudal Rostral Transverse Ridges
Figure 6: Terminology used in the methodology and systematic paleontology section of this paper. Anatomically oriented terminology is taken from Purnell et al. (2000). Note: the conodont illustration is oriented according to convention with the dorsal point down and the ventral pointing up. 34 Texas Tech University,Steven J. Rosscoe , August 2008
ABC DEFG
HI J KLM N
O P Q R S T U
VWXYZa b Figure 7: Diagrams representing each of the major variations observed in the conodont genera Idiognathodusand Streptognathodus in the study interval. Each diagram represents a specific variation, suites of variation are more common than single variations. A-I = Rostral Lobe Variation, J-M = Caudal Lobe Variation, N-V = Platform Ornamentation Variation, W-Y = Platform Troughing and Z-b = Platform Shape Variation. 35 Texas Tech University, Steven J. Rosscoe, August 2008
CHAPTER 3 THE DIVERSIFICATION OF IDIOGNATHODUS AND THE RISE OF STREPTOGNATHODUS IN THE MIDCONTINENT BASIN, NORTH AMERICA
The interval of time spanning the Lost Branch to Dewey sequences in the Midcontinent basin of North America was one of extinction and diversification in conodonts. An extinction event in the latest Desmoinesian formed a “morphological bottleneck” through which species of Gondolella, Idioprioniodus, Hindeodus, Adetognathus, and Idiognathodus were forced to pass. Only one species of Idiognathodus survived, from which nearly all of the Missourian forms of Idiognathodus in the Midcontinent Basin were derived. The deposits of the Lower Missourian Composite Sequence record a diversification event amongst the idiognathodid conodonts that is expressed by a great number of variations in element morphology. The diversification of the idiognathodid conodonts reached its apex in the Swope Sequence. Another minor extinction event followed the Swope Sequence. Many of the survivors range into the Middle Missourian Composite Sequence. Species were lost and gained at a near constant rate throughout the Middle Missourian Composite Sequence, but most important, the new genus Streptognathodus diverged from an idiognathodid ancestor in the Hogshooter Sequence. In the Dewey Sequence, the conodont fauna appears to have become increasingly more stable in morphology than in prior sequences. Complete systematic paleontology and SEM photos of the conodonts discussed in this chapter can be found in Appendix B.
The Latest Desmoinesian Extinction Event The Lost Branch Sequence is the last of the highstand deposits of the Marmaton Composite Sequence. The Lost Branch conodont fauna is characterized by abundant specimens of Idiognathodus, Swadelina, Neognathodus, Idioprioniodus, Gondolella, Adetognathus, and Hindeodus. The latest Desmoinesian extinction event resulted in the loss of all species of Swadelina and Neognathodus, as well as Idiognathodus expansus Stauffer and Plummer 1932. The extinction of I. expansus is confirmed by the absence of its juvenile form (short medial carina, with complete transverse ridges) (Plate 1, figures 1, 2) in overlying strata. The remaining species of Idiognathodus, I. swadei Rosscoe and Barrick (In Press) is the root stock for nearly all Missourian Idiognathodus species in the Midcontinent Basin.
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The swadei Lineage The swadei lineage (Figure 8) traces changes in the protruding and robust nature of the rostral lobe in P1 elements that lack disruption of transverse ridges on the platform. A fairly constant rate of diversification occurred. Lobes grew larger and more protruding from the Lost Branch Sequence to the Hertha Sequence. By the time of the Swope Sequence, there was an explosion of continuous and non‐robust rostral lobe forms. The swadei lineage lost its dominance in Swope Sequence and the last species of the lineage went extinct at the end of the Dennis Sequence. Idiognathodus swadei is a robust form of Idiognathodus that is easily recognized by its expanded and robust rostral lobe. The juvenile form of I. swadei (Plate 2, Figures 1, 2) shows a distinctive elongate medial carina and weak trough (seen in specimens up to around 1 mm in full element length). These characters are commonly lost in larger specimens. The juvenile also exhibits development of both caudal and rostral lobes. Juveniles found above the level of the Lost Branch Sequence all exhibit a weak trough and a long medial carina. Idiognathodus swadei ranges from at least the Lost Branch Sequence to the end of the Swope Sequence. Idiognathodus swadei gave rise to two new species in the Hepler Sequence. Direct descendants in the swadei lineage exhibit expanded to elongate rostral lobes. The first two species, however, form a new lineage that diverged from of the swadei Lineage. Idiognathodus sulciferus Gunnell 1933 appears with I. harkeyi Gunnell 1933 in the South Mound Shale of the Hepler Sequence. Idiognathodus sulciferus exhibits a moderately restricted rostral lobe rather than the expanded rostral lobe of I. swadei. Idiognathodus harkeyi exhibits a restricted and protruding rostral lobe that gives its P1 elements an overall triangular appearance. The descendents of I. sulciferus and I. harkeyi are discussed later in this chapter as members of the sulciferus lineage. In the Shale Hill Sequence, Idiognathodus swadei gave rise to two new species: Idiognathodus turbatus Rosscoe and Barrick (In Press) and I. siculus Gunnell 1933. Idiognathodus turbatus is characterized by a medial groove that is filled with medial nodes. The platform of I. turbatus is commonly chaotic in nature, consisting of a series of randomly truncated ridges and nodes. Descendents of I. turbatus are discussed later in this chapter as members of the turbatus lineage. Idiognathodus siculus is characterized by a protruding and robust expanded rostral lobe. This species is rather rare and exhibits an ornamentation pattern where only the ventral
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portions of the lobe are ornamented. It persists through the Dennis Sequence of the Middle Missourian Composite Sequence. The swadei lineage undergoes further diversification in the Hertha Sequence. Idiognathodus vorax Rosscoe and Barrick (In Press) arose from I. swadei. Idiognathodus vorax is distinguished by its elongate and robust rostral accessory lobe. The elongation and rostral expansion of the rostral lobe gives the P1 element a lower dorso‐ventral to rostro‐caudal ratio than most other P1 elements in this study. The lack of a medial groove or medial nodosity suggests that I. swadei, not I. turbatus, is its ancestor. Idiognathodus vorax ranges to the end of the Swope Sequence. In the Swope Sequence, Idiognathodus confragus Gunnell 1933 and I. folium Gunnell 1933 descended from I. swadei. The new species I. lobatus Gunnell 1933 also appeared. Idiognathodus confragus is recognized by its robust and continuous (non‐protruding) rostral and caudal lobes and its elongate medial carina. Idiognathodus confragus has a ventrally shifted caudal lobe; up to one‐half the length of the caudal lobe is ventral of the ventral termination of the rostral lobe. Idiognathodus confragus is one of two species that does not exhibit the equal ventral termination of rostral and caudal lobes. The robust nature of the rostral lobe and undisrupted transverse ridges fits best with the swadei lineage and I. confragus likely developed from I. swadei. Idiognathodus confragus ranges to the end of the Dennis Sequence in the Middle Missourian Composite Sequence. Idiognathodus folium is recognized by its expanded and continuous rostral lobe. Idiognathodus folium likely arose as a result of reduction of the robust lobe of I. swadei. Idiognathodus folium ranges to the end of the Dennis Sequence in the Middle Missourian Composite Sequence. Idiognathodus lobatus is recognized by its robust expanded rostral lobe and robust caudal lobe. The more continuous nature of the lobe indicates that it could have arisen from I. folium or from I. swadei directly. Idiognathodus lobatus is a short ranging species that is present only in the Swope Sequence. The species Idiognathodus swadei, I. vorax, I. turbatus and I. lobatus are absent above the level of the Swope Sequence. Idiognathodus folium, I. siculus, and I. confragus pass through to the overlying Mound Valley Sequence. Within the Mound Valley Sequence, one new species is added to the lineage. Idiognathodus species 2 is recognized by its protruding expanded rostral lobe and a distinctive medial groove that bisects the dorsal platform. Small specimens of I. species 2 have rostral lobes ornamented only on the ventral portion, but in larger specimens this feature is not retained. The ventral only ornamentation of the rostral lobe in juveniles implies
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that I. species 2 arose from I. siculus. Idiognathodus species 2 is restricted to the Mound Valley Sequence, with no specimens found in underlying or overlying strata. All remaining species from the swadei lineage were lost at a faunal turnover event at the end of the Dennis Sequence.
The turbatus Lineage The turbatus lineage (Figure 9) traces changes in the rostral lobe and platform ornamentation in a group of idiognathodid conodonts characterized by varying degrees of disruption of transverse ridges. Through time this lineage shifted from robust and protruding rostral lobes to reduced and elongate rostral lobes. The style of disruption of the platform also varies with time. As discussed earlier, Idiognathodus swadei gave rise to I. turbatus in the Shale Hill Sequence. Idiognathodus turbatus ranges from the Shale Hill Sequence to the Swope Sequence of the Lower Missourian Composite Sequence. In the Hertha Sequence, Idiognathodus species 1 Rosscoe and Barrick (In Press) arose from I. turbatus. Idiognathodus species 1 is recognized by an elongate rostral lobe that is ornamented with large, rostro‐caudally elongate nodes. The chaotic platform is expressed as multiple grooves or multiple node rows. The species is relatively rare and ranges from the Hertha to the Swope Sequence. The Swope Sequence displays a major diversification in the turbatus lineage. Idiognathodus clavatulus (Gunnell, 1933) is characterized by its reduced elongate rostral lobe, reduced caudal lobe and medial groove. Idiognathodus clavatulus arose from I. species 1 by continued elongation of the rostral lobe and ornamentation of the lobe with a single row of nodes. The chaotic platform of I. species 1 is reformed into a series of closely‐spaced transverse ridges disrupted by a well‐developed medial groove. Idiognathodus clavatulus was originally classified as Streptognathodus. The platform of I. clavatulus is not troughed (the entire rostro‐ caudal width of the platform must be a part of the trough structure to be Streptognathodus), instead the platform has a deep medial groove that gives a superficial appearance of a trough. Idiognathodus clavatulus is found only in the Swope Sequence. Idiognathodus cancellosus (Ellison, 1941) first appears in the Swope Sequence and likely arose from either I. turbatus or I. clavatulus. The medial nodosity of I. cancellosus is similar to the medial nodosity in I. turbatus, but the elongate rostral lobe of I. cancellosus is more similar to the elongate rostral lobe of I. clavatulus. Idiognathodus aff. cancellosus is so similar to I. cancellosus that the two are most likely related. The rostral lobes in I. aff. cancellosus are
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ornamented with only one to three nodes. Idiognathodus cancellosus and I. aff. cancellosus range from the Swope Sequence to the Dennis Sequence in the Lower and Middle Missourian Composite sequences.
The Idiognathodus biliratus Problem Idiognathodus biliratus Gunnell, 1933 (Figure 9), is a species that until now has commonly been grouped with Idiognathodus cancellosus. At present, there seems to be no obvious ancestor in any lineage of Early Missourian, Midcontinent Idiognathodus that could have easily given rise to a species with no rostral or caudal lobes and an extremely elongate medial carina at the level of the Swope Sequence. The sulciferus lineage developed species without lobes, but not until the Dennis Sequence (two high frequency sequences later). The similarity to I. cancellosus is suggestive, but one cannot easily explain how the reduced lobes and medial nodosity of I. cancellosus are so quickly converted to a species with no lobes and a highly elongate medial carina. The range for I. biliratus is exactly the same as the ranges for I. cancellosus and I. aff. cancellosus (Swope to Dennis sequences). A remarkably similar species from Moscow Basin, I. neverovensis (Goreva and Alekseev, 2006), co‐occurs with I. cancellosus in some Eurasian strata. It is possible that I. biliratus is a relative of I. neverovensis that travelled to the Midcontinent Basin during the Swope Sequence deposition.
The sulciferus Lineage The sulciferus lineage (Figure 10) traces forms of Idiognathodus recognized by their small rostral lobes. Throughout the duration of the Lower Missourian Composite Sequence species develop smaller lobes. In the Swope Sequence, the first species lacking a rostral lobe rises. In the Middle Missourian Composite Sequence, two divergent trends can be recognized. In one trend, lobe reduction continues to the complete loss of both rostral and caudal lobes in the Dennis Sequence. In the other trend, lobes grow larger and more robust. In the Hepler Sequence, Idiognathodus sulciferus and I. harkeyi arose from I. swadei. It is certain that I. sulciferus is a direct descendent of I. swadei. A variety of intermediate forms between I. sulciferus and I. swadei can be observed in the Hepler Sequence. It is less certain from which species I. harkeyi most likely arose. Idiognathodus harkeyi may result from reduction of the accessory lobes and platform width of I. sulciferus. Both I. sulciferus and I. harkeyi range to the end of the Swope Sequence.
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Two more species of the sulciferus lineage appeared in the Shale Hill Sequence. Idiognathodus eccentricus (Ellison, 1941) arose from I. harkeyi and first appears in the base of the Exline Limestone. A restricted lobe and a complete eccentric groove that replaces the weak deflection of transverse ridges in I. harkeyi, resulted in the first true specimens of I. eccentricus. Initial specimens of I. eccentricus (Figures 42.9, 42.11, 42.14) retain the thin and pointed platform of I. harkeyi. In higher sequences, I. eccentricus became more rounded and broader, approaching the form shown by the holotype (Figure 42.15). Idiognathodus eccentricus ranges to the end of the Swope Sequence. Idiognathodus fusiformis Gunnell, 1933, arose from I. sulciferus. The platform of I. fusiformis is broader and carries a more protruding rostral lobe. Transverse ridges in I. fusiformis are disturbed along the caudal margin in those specimens recovered from the interval between the Shale Hill and Swope sequences. In specimens recovered above the level of the Swope this caudal disruption is lost and the protruding nature of the rostral lobe is better developed. Idiognathodus fusiformis ranges from the Shale Hill Sequence to the Dewey Sequence. No new species were added to the sulciferus lineage in the Hertha Sequence, but two additional species appeared in the overlying Swope Sequence. Idiognathodus fusiformis gave rise to I. corrugatus, a species resulting from the loss of the rostral lobe. In larger specimens it is common to see a single node just to the outside of the rostral margin of the element. This character likely reflects the protruding nature of the rostral lobe in its ancestor, I. fusiformis. Specimens of I. corrugatus retain disruption of the transverse ridges, as seen in I. fusiformis, in the form of a weak caudal marginal to caudal eccentric groove, but only in specimens collected from the Swope and Mound Valley sequences. Idiognathodus corrugatus ranges into the Dewey Sequence. Idiognathodus sulciferus gave rise to I. species 3 by further reduction of lobe size and development. A reduced to restricted rostral lobe and a caudal lobe ornamented with fewer than three nodes replaced the more robust lobes of I. sulciferus. This form ranges through to the end of the Hogshooter Sequence. Idiognathodus sulciferus, I. harkeyi, and I. eccentricus were lost at the end of the Swope Sequence. Study of the limited faunas recovered from the Mound Valley Sequence has yielded an abundance of Idiognathodus corrugatus and I. species 4 arose from I. species 3. Idiognathodus species 4 resulted from a decrease in platform length (dorso‐ventral shortening) and further reduction of the rostral lobe. Some redevelopment of the caudal lobe has been observed. The
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inset rostral lobe is almost completely lost in some specimens. Idiognathodus species 4 ranges through the Dewey Sequence. The Dennis Sequence contains the rise of two of the most important members of the sulciferus lineage. Idiognathodus cherryvalensis arose from I. species 4 by the complete loss of both rostral and caudal accessory lobes. While still relatively broad in shape, the platform lacks lobes, but may show one large node on the caudal margin of the element. This lobe‐less species exhibits a longer medial carina than other species of Idiognathodus, and is the likely ancestor to the genus Streptognathodus. Idiognathodus cherryvalensis ranges through to the end of the Dewey Sequence in this study interval. Idiognathodus magnificus Stauffer and Plummer, 1932, developed from I. fusiformis. The robust rostral lobes of I. magnificus replaced the protruding restricted lobes of I. fusiformis. Idiognathodus magnificus is the first species in the Missourian to exhibit obvious asymmetric element pairs. The dextral elements are very large and robust with a moderately expanded robust and protruding rostral lobe, whereas the sinstral elements are thinner and exhibit an expanded and robust rostral lobe. Asymmetry like this has been reported in younger specimens like Idiognathodus simulator (Barrick et al., In Press). Idiognathodus magnificus ranges through the end of the Dewey Sequence in this study interval. In the Hogshooter Sequence, no new species of Idiognathodus were added, but the last occurrence of Idiognathodus species 3 is recorded. In the Cherryvale Sequence I. cherryvalensis gave rise to I. symmetricus Gunnell, 1933 (Fig. 11). Idiognathodus symmetricus has ventrally shifted and reduced rostral and caudal lobes. The small lobes form robust parapets along the ventral portions of the caudal and rostral margins of the element. The longer medial carina from I. cherryvalensis was retained in I. symmetricus. Idiognathodus symmetricus ranges through the Dewey Sequence in this study interval. In the Dewey Sequence, one final species was added to the sulciferus lineage. Idiognathodus multinodosus Gunnell, 1933, evolved from I. corrugatus. Idiognathodus multinodosus modified the missing rostral lobe into a missing or ghost lobe and reduced the size of the caudal lobe to one with room for only one or two small nodes. The transverse ridges on the platform were modified by two marginal grooves that give the superficial appearance of troughing to the flat platform of the element. This is the last species to evolve in the sulciferus lineage within the study interval and it may range above the Dewey Sequence.
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Origin of Streptognathodus (Figure 11) The oldest species of Streptognathodus appear in the Hogshooter Sequence. At the base of the Hogshooter Sequence is a sequence boundary above which is a conodont‐rich lag. In outcrops where good faunas can be collected from the Hogshooter Sequence (Southern Kansas and Oklahoma) this lag bed marks the first appearance of five species of Streptognathodus. The order in which these species radiated cannot be reliably determined due to the extreme condensation of first appearances in the lag bed. The most likely ancestor to these early species of Streptognathodus is Idiognathodus cherryvalensis. Previous to this study the best ancestors for species of Streptognathodus were considered I. cancellosus or I. clavatulus (Barrick et al., 2004; Rosscoe and Barrick, In Press). The margins of Idiognathodus cherryvalensis are slightly elevated, but the platform is flat with no evidence of troughing. Idiognathodus cherryvalensis has no rostral or caudal accessory lobes. The species of Streptognathodus most similar to I. cherryvalensis is S. elegantulus. Streptognathodus elegantulus Stauffer and Plummer, 1932, is most likely the first species of Streptognathodus to evolve from I. cherryvalensis. The platform became troughed, the elongate medial carina reduced to medial nodosity, and the lobes remain absent or form ghost lobes. Streptognathodus gracilis Stauffer and Plummer, 1932, simply added a small caudal lobe with one small node to the form exhibited by S. elegantulus. Streptognathodus sulcatus Gunnell, 1933, developed a better trough and continued to grow its caudal lobe. These three species are all closely related and while the author has presented them evolving in a chain (I. cherryvalensis – S. elegantulus – S. gracilis – S. sulcatus) it is equally justified to assume that all three species radiated from I. cherryvalensis. The first species to have rostral lobes are Streptognathodus increbescens Stauffer and Plummer, 1932, and S. excelsus Stauffer and Plummer, 1932. Streptognathodus increbescens has a reduced rostral lobe (ornamented only on the ventral margin) and a robust caudal lobe. Streptognathodus excelsus has the most robust and expanded rostral and caudal lobes of the early species of Streptognathodus. Of the previously discussed Streptognathodus species they are most similar to S. sulcatus. These species of Streptognathodus may have developed from S. sulcatus or radiated directly from I. cherryvalensis. These two species have an appearance very similar to that of I. cancellosus or I. clavatulus. If the similarity between I. cancellosus or I. clavatulus is considered to be most important, then the argument could be made that S. increbescens and S. excelsus were independently derived from the other species of
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Streptognathodus. If this is correct, because S. excelsus is the type species of Streptognathodus the three species more closely tied to I. cherryvalensis belong to an entirely different genus of troughed conodonts.
Model of Evolution in Idiognathodus and Streptognathodus This model summarizes the changes observed in Idiognathodus and Streptognathodus populations throughout the study interval. It places the lineages discussed previously into a context reflecting changing selective pressures and sequence imprinting on the natural path of evolution in these conodonts. Further research and data collection will be required to provide the support necessary for publication of the following observations and interpretations. Figure 12 shows the composite range chart for the study interval. Figure 13 shows the changes in species diversity throughout the study interval. The extinction at the end of the Lost Branch Sequence, where all species of Swadelina and Neognathodus along with Idiognathodus expansus are lost, is likely in response to a very large global lowstand event that forms the composite sequence boundary between the Marmaton Composite Sequence and the Lower Missourian Composite Sequence. Widespread deposits of sandstone (Hepler and Seminole sandstones) in the basin of Oklahoma and a large unconformity capping the Lost Branch Sequence indicate that this boundary is more significant than the typical boundary between high frequency sequences. Throughout most of the Lower Missourian Composite Sequence Idiognathodus responded to the loss of competition by rapidly diversifying to fill the eco‐ and morphospace vacated by the species of Swadelina and Neognathodus that had been lost in the Lost Branch Sequence. In the Hepler Sequence, the robust lobes of Idiognathodus swadei were likely favored for their efficiency in food processing. Large, well ornamented lobes would have dramatically increased the surface area available for processing food. Despite this advantage (which likely allowed it to survive the latest Desmoinesian extinction event), the first new species formed have reduced lobe‐sizes. Idiognathodus sulciferus and I. harkeyi have lobes reminiscent of the restricted rostral lobe of the extinct I. expansus. The sulciferus lineage likely originated by filling the niche vacated by I. expansus. In the Shale Hill Sequence, three of the four new species (I. fusiformis, I. eccentricus, and I. turbatus) all develop disrupted transverse ridges. This implies that there may have been an advantage during the deposition of this sequence for specimens with increased functional
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surface area without the modification of platform shape. Disruption of transverse ridges will increase surface roughness of the platform and increase food processing efficiency without having to dramatically alter the shape of the platform. The switch to creating efficiency by ornamentation rather than size provides the first indications that robust lobes are falling out of favor. The only robust‐lobed specimen added in the Shale Hill Sequence (I. siculus) is unique in that the ornamentation of its rostral lobe is on the ventral surface only, also suggesting the end of dominance for large‐lobed specimens. The Hertha Sequence was the peak for large‐lobed idiognathodids. Continued domination of the Idiognathodus fauna by the swadei and turbatus lineages was expressed with the development of I. vorax, a species known for its elongate and expanded robust rostral lobe. The great size of the rostral lobe on I. vorax is not seen in any other species in this interval. The growing selective pressure for increased surface roughness and decreased surface area was becoming stronger. The development of I. species 1 brought the first member of the swadei lineage that reduced the size of its rostral lobe and developed a chaotic style of platform ornamentation. No new species were added to the sulciferus lineage at this time. The trend in maximizing the surface roughness and reducing overall surface area peaked in the Swope Sequence. Two new species were added to the sulciferus lineage, both with loss or reduction of the rostral lobes (I. corrugatus and I. species 3). There was a flurry of diversification in the swadei and turbatus lineages in response to the new focus on reduced surface area. Three new species were added to the swadei lineage (I. lobatus, I. confragus, and I. folium). Three new species are added to the turbatus lineage (I. clavatulus, I. cancellosus, I. aff. cancellosus). All new species added to the turbatus and swadei lineages have reduced lobe‐ sizes. In addition, I. biliratus appeared and lacked both rostral and caudal lobes. Idiognathodus biliratus has a similar appearance to species of Neognathodus and may represent an attempt at the redevelopment of the Neognathodus form. Species that once dominated in all lithologies and geographic locations (I. swadei and I. turbatus) became restricted to the shallow shelf environments of Nebraska (Fort Calhoun and PWA Quarries) and Iowa (East Peru, Iowa). Selective extinction at the end of the Swope Sequence shows an advantage for reduced lobes and disrupted platforms. The swadei and turbatus lineages go from 11 species at the beginning of the Swope to 6 species at the end of the Swope (45% loss). The loss of species in the swadei and turbatus lineages accounts for 66% of the entire species loss in Idiognathodus at the end of the Swope Sequence. The surviving species of the swadei and turbatus lineages are
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those that exhibited some reduction of rostral lobe size or disruption of the transverse ridges. The sulciferus lineage goes from 6 species at the start of the Swope to 3 species at the end of the Swope (50% loss). Overall diversity of Idiognathodus decreases by 50% at the boundary between the Lower Missourian Composite Sequence (Swope Sequence) and Upper Missourian Composite Sequence (Mound Valley Sequence). The only species to survive are those with most effective functional surface area (greatest surface roughness) for the smallest overall element surface area. The swadei and turbatus lineages see almost no development in the Middle Missourian Composite Sequence. One new species is added in the Mound Valley Sequence (Idiognathodus species 2), but it is lost at the end of the Mound Valley Sequence. All remaining species of the swadei and turbatus lineages (I. folium, I. confragus, I. cancellosus, and I. aff. cancellosus) as well as I. biliratus go extinct at the boundary between the Dennis and Hogshooter sequences. During this time period, three new species are added to the sulciferus lineage. Idiognathodus species 4, and I. cherryvalensis continue in the trend of lobe reduction, while I. magnificus begins to redevelop robust lobes and element asymmetry. No species are lost from the sulciferus lineage at this time. The boundary between the Dennis and Hogshooter sequences marks a major faunal turn‐over event. The extinction of the swadei and turbatus lineages at the same level as the appearance of species from the genus Streptognathodus may not be coincidental. Extinction of the swadei and turbatus lineages may have freed the ecospace required for species of Streptognathodus to evolve or competition with Streptognathodus may have resulted in the extinction of the swadei and turbatus lineages. The answer to this question is locked in the large unconformity and lag separating the Dennis and Hogshooter sequences. This faunal shift also marks a transition to slower rates of diversification and extinction for the remainder of the study interval. The remainder of the Middle Missourian Composite Sequence is more stable than any other interval in this study. In the Cherryvale and Dewey Sequences a total of two species are lost (Idiognathodus species 3 and Streptognathodus sulcatus), and a total of two species are gained (I. symmetricus and I. multinodosus). The rapid diversification of the Lower Missourian Composite Sequence resulted in relatively unstable conodont populations that did not recover to a stable number of species until the faunal turnover at the end of the Dennis Sequence.
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Dewey
Cherryvale
Hogshooter
Dennis
Mound Valley
I. species 2
Swope ? I. confragus I. folium I. lobatus
Hertha
I. vorax
Shale Hill I. siculus I. turbatus (Fig. 9) Hepler
I. sulciferus (Fig. 10) Lost Branch
I. swadei Figure 8: The lineage ofIdiognathodus swadei . Line drawings represent the general morphological characters of each species. The horizontal lines indicate marine rocks of each sequence. The non-marine intervals would be in between. Each horizontal line is a snap shot of diversity at the maximum flooding surface for the sequence. Dashed lines indicate alternative relationships. 47 Texas Tech University,Steven J. Rosscoe , August 2008
Dewey
Cherryvale
Hogshooter
Dennis
Mound Valley
Swope
I. clavatulus I. cancellosus I.aff. cancellosus I. biliratus (Fig. 11) ? Hertha
I. species 1
Shale Hill
I. turbatus
Hepler
Lost Branch I. swadei (Fig. 8) Figure 9: The lineage ofIdiognathodus turbatus. Line drawings represent the general morphological characters of each species. The horizontal lines indicate marine rocks of each sequence. The non-marine intervals would be in between. Each horizontal line is a snap shot of diversity at the maximum flooding surface for the sequence. Dashed lines indicate potential, but unconfirmed relationships. 48 Texas Tech University,Steven J. Rosscoe , August 2008
Dewey
I. multinodosus Cherryvale
Hogshooter
Dennis I. cherryvalensis I. magnificus (Fig. 11)
Mound Valley I. species 4
Swope
I. species 3 I. corrugatus
Hertha
Shale Hill
I. eccentricus I. fusiformis
? Hepler I. harkeyi I. sulciferus ?
I. swadei Lost Branch (Fig. 8) Figure 10: The lineage ofIdiognathodus sulciferus. Line drawings represent the general morphological characters of each species. The horizontal lines indicate marine rocks of each sequence. The non-marine intervals would be in between. Each horizontal line is a snap shot of diversity at the maximum flooding surface for the sequence. Dashed lines indicate alternative relationships. 49 Texas Tech University,Steven J. Rosscoe , August 2008
Dewey
Cherryvale
I. symmetricus
Hogshooter
S. excelsus S. increbescens S. sulcatus S. gracilis S. elegantulus
Dennis
I. cherryvalensis (Fig. 10) Mound Valley
Swope
I. clavatulus (Fig. 9) Hertha
Shale Hill
Hepler
Lost Branch
Figure 11: The potential origin ofStreptognathodus from Idiognathodus cherryvalensis . Line drawings represent the general morphological characters of each species. The horizontal lines indicate marine rocks of each sequence. The non-marine intervals would be in between. Each horizontal line is a snap shot of diversity at the maximum flooding surface for the sequence.
50 Texas Tech University,Steven J. Rosscoe , August 2008
Dewey Sequence ideMsora opst Sequence Composite Missourian Middle
Cherryvale Sequence
I. multinodosus
Hogshooter Sequence
aff.
I. biliratus
I. cancellosus
I. cancellosus
I. symmetricus
Dennis Sequence
S. gracilis
S. sulcatus
S. excelsus
S. elegantulus
S. increbescens
Mound Valley
alensis Sequence
species 1
I. magnificus
I. eccentricus
I. sulciferus
I. harkeyi
I. swadei I. vorax I. turbatus I. I. clavatulus
I. cherryv
Swope oe isuinCmoieSequence Composite Missourian Lower
species 2
species 4 Sequence
I.
I.
Hertha
I. folium species 3 Sequence
I. lobatus
I.
I. confragus
I. corrugatus
Shale Hill Sequence
is Hepler
I. siculus Sequence
I. fusiform
I. expansus Marmaton Lost Branch Sequence
Figure 12: Composite Range Chart of conodonts within the uppermost Marmaton Composite Sequence, the Lower Missourian Composite Sequence, and the Middle Missourian Composite Sequence. Dashed vertical lines indicate range through, solid vertical lines represent confirmed appearances. Those lines truncated at top and bottom of the figure may continue. Horizontal lines indicate sequence boundaries. 51 20 0
18 2
16 4 ubro Species of Number 14 6
Species
12 8 Streptognathodus
10 10 ea ehUiest,, University, Tech Texas
Idiognathodus 52 8 12
Number of 6 14
4 16 2008 August Rosscoe J. Steven
2 18
0 20 Lost Branch Hepler Shale Hill Hertha Swope Mound Valley Dennis Hogshooter Cherryvale Dewey Figure 13: Variations in number of species ofIdiognathodus and Streptognathodus from the Lost Branch Sequence to the Dewey Sequence. Gray bars represent total number of species found in each sequence. The black bars represent the total number of species that are lost at the end of each sequence. The white bars represent the number of new species added to each sequence. Species ofIdiognathodus are charted from the bottom up. Species ofStreptognathodus are charted from the top down. Texas Tech University, Steven J. Rosscoe, August 2008
CHAPTER 4
IMPLICATIONS OF THE NEW TAXONOMY
From the initial work of Swade (1985), the goal to recognize specific high frequency sequences (cyclothems) has spurred much of the research on conodonts of the Middle and Upper Pennsylvanian. The characterization of high frequency sequences by specific, short‐ ranging morphotypes resulted in attempts at developing a biostratigraphic framework for the Midcontinent (Ritter et al., 2002; Barrick et al., 2004)(Figure 14). The focus on morphotypes allowed for biostratigraphic advances to occur independently of taxonomic revision. With the emphasis on each high frequency sequence, the potential exists for an over‐exaggeration of characters that does not reflect the actual evolutionary patterns in Idiognathodus and Streptognathodus. Each unconformity‐bounded sequence is a window into the pattern of evolution in Idiognathodus and Streptognathodus. Evolution of these conodonts was likely independent of the regional stratigraphy and evolution continued through the time represented by unconformities. Each high frequency sequence represents distinctive environmental conditions that imprint ecological variation upon the pattern of species origin and extinction throughout the Pennsylvanian. High‐frequency sequences vary in magnitude in response to local, regional, and global conditions. Each sequence likely developed unique geochemical conditions, depositional conditions, and climatic conditions. These unique conditions may cause the pattern of evolution to be over‐printed with variation that does not follow the path of evolution. The function‐based taxonomy used in this dissertation focuses on variation more closely linked with the pattern of evolution, rather than sequence specific variation. Careful use of diagnostic Idiognathodus and Streptognathodus species can aid in local, regional, and even global high frequency sequence correlation (Heckel et al., 2007).
A Revised Late Desmoinesian to Middle Missourian Conodont Zonation To fully reflect the changes of the new taxonomy on the ability to recognize high frequency sequences, it is necessary to revise the zonation of Barrick et al. (2004). Both the old and revised versions of the Midcontinent Conodont Zonation appear in Figure 15. Where possible, the designations of Barrick et al. (2004) were preserved and composite sequence
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lowstands are indicated to show periods of potentially large gaps in the sedimentary record of the Midcontinent. The Neognathodus roundyi Zone (includes the Swadelina nodocarinata Zone) includes the Lost Branch Sequence in the Midcontinent Basin. The roundyi Zone is defined by the first appearance of N. roundyi at its base and its extinction at the top. The roundyi Zone is large, but compares well with use of the roundyi Zone in the Appalachian and Moscow Basins, implying some level of global correlation. The Sw. nodocarinata Zone is defined by the first appearance of Sw. nodocarinata at its base (Norfleet Sequence, below the Lost Branch Sequence) and its extinction at the top. The Idiognathodus fauna of these Zones is composed of I. expansus and I. swadei during the Lost Branch Sequence. Following the Neognathodus roundyi Zone, a substantial lowstand event occurred in the Midcontinent Basin. Upon recovery from the lowstand, initial populations of Idiognathodus were limited to I. swadei, I. sulciferus, and I. harkeyi. Both I. sulciferus and I. harkeyi arose from I. swadei in the Hepler Sequence. At the base of the Exline Limestone in the Shale Hill Sequence I. eccentricus arose from I. harkeyi. Barrick et al. (2004) placed the deposits of the Hepler Sequence with the Lost Branch Sequence. It is proposed, that the Hepler Sequence belongs to the new sulciferus Zone. As now defined, the sulciferus Zone has its base at the first occurrence of I. sulciferus (following the extinction of all species Swadelina and Neognathodus) and its top at the first appearance of I. eccentricus. The eccentricus Zone is defined at the base by the appearance of I. eccentricus and at the top by the first appearance of I. cancellosus and includes the Shale Hill and Hertha Sequences. The Hertha Sequence may be recognized by the first appearance of I. vorax, but the relative rarity of the species is too limiting to be formally recognized as a Subzone. The cancellosus Zone (Barrick et al., 2004) spans the interval from the base of the Swope Sequence to the top of the Dennis Sequence. This Zone is defined at its base by the first appearance of I. cancellosus and at its top by the first appearance of Streptognathodus gracilis. In the Midcontinent basin, the extinction of I. cancellosus occurs at the unconformity between the Dennis and Hogshooter Sequences as does the first appearance of S. gracilis. The cancellosus Zone spans three sequences, including the major lowstand in the Mound Valley Sequence. The I. cancellosus Zone can be split into two Subzones. The base of the lower, the clavatulus Subzone, is defined by the first appearance of I. clavatulus in the Swope Sequence and the top is defined by the first appearance of I. cherryvalensis at the base of the Dennis
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Sequence. No formally named species is restricted to the Mound Valley Sequence. If named, I. species 2 could form a Subzone specific to the Mound Valley Sequence. The base of the upper cherryvalensis Subzone is defined by the first appearance of I. cherryvalensis and the top is defined by the first appearance of S. gracilis. The cherryvalensis Subzone is restricted to the Dennis Sequence. The last Zone of the study interval is the Streptognathodus gracilis Zone. It is marked at its base by the first appearance of S. gracilis. The upper boundary of this Zone, the first appearance of Idiognathodus aff. simulator, does not fall within the study interval and corresponds to the extinction of S. gracilis. Within the study interval, three Subzones can be established. Each Subzone corresponds to one high frequency sequence. The lowest, the gracilis Subzone, is defined at the base by the first appearance of S. gracilis and is defined at the top by the first appearance of I. symmetricus and includes the Hogshooter. The second, the symmetricus Subzone, is defined at the base by the first appearance of I. symmetricus and at the top by the first appearance of I. multinodosus and includes the Cherryvale Sequence. The highest Subzone, the multinodosus Subzone, is defined at its base by the first appearance of I. multinodosus, but the upper bound likely falls outside of the study constraints. It includes the Dewey Sequence. The Dewey Sequence has previously been identified by the acme of I. magnificus (Heckel, 1999), but the recognition of abundant sinistral and dextral elements from lower intervals (this study) may restrict this use. When used in conjunction with other conodonts the acme of I. magnificus may prove useful in the absence of specimens of I. multinodosus.
Other Global Conodont Faunas
Moscow Basin Goreva and Alekseev (2001) established a revised conodont zonation for the Moscovian of the Moscow Basin and published ten plates of conodonts to illustrate significant taxa. Streptognathodus subexcelsus Goreva & Alekseev 2001, from the lowest unit in the Kasimovian, the Krevyakian Substage, is similar to I. swadei, but S. subexcelsus has a distinctive narrow and elongate rostral lobe that does not protrude outward as does the rostral lobe in I. swadei. Idiognathodus trigonolobatus Barskov & Alekseev 1976, which appears near the top of the regional Krevyakian Substage, is similar in form to I. expansus of the Midcontinent, but I.
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trigonolobatus lacks a well defined rostral lobe restricted to the ventral quarter of the platform and its rostral lobe often protrudes from the rostral margin. Marginal grooving is common in specimens of I. trigonolobatus as in specimens of I. expansus. Goreva and Alekseev (2006) recently named three new species from lower Kasimovian beds of the Moscow Basin. Streptognathodus isakovae and S. neverovensis, both based on material from the basal regional Khamovnikian Substage of the Kasimovian, are forms with extremely long carinas, unlike most species from the lower Missourian of the Midcontinent. Idiognathodus mestsherensis, from the overlying regional Dorogomilovian Substage, is similar in form to S. subexcelsus but has poorly developed rostral and caudal lobes. It is also unlike any lower Missourian, Midcontinent Idiognathodus species. Alekseev and Goreva (2007) updated the conodont zonation for the Kasimovian and Gzehlian stages in Russia, where they inserted the Idiognathodus sagittalis Zone, based on the first occurrence of this species at the base of the Khamovnikian. Heckel et al. (2007) reported that a “grooved form that closely resembles I. eccentricus” is present in the basal Neverovo Formation, which lies just above the base of the Khamovnikian. Goreva et al. (2007) proposed that the Afanasievo section, southeast of Moscow, serve as a neostratotype for the Kasimovian Stage and presented range charts of conodont and fusulinid species from the Afanasievo section. Idiognathodus sagittalis appears two meters above the base of the Neverovo Formation, about one meter above where I. aff. eccentricus occurs in a single sample near the base of the formation.
Donets Basin Idiognathodus sagittalis Kozitskaya 1978, is the only species commonly reported from
1 the lower Kasimovian interval in the Donets Basin (limestones N5 ‐O1) (Kozitskaya et al., 1978).
The holotype of Idiognathodus sagittalis is from limestone O1 (Figure 41.14). The holotype has an elongate rostral lobe that protrudes from the rostral margin. The rostral adcarinal ridge forms the ventral margin of the element on the rostral side, effectively separating the lower elevation rostral lobe from the central platform. It exhibits a marginal groove and weak medial nodosity. Juvenile specimens are shown with complete medial nodosity and no evident lobes at such a reduced size. Other illustrated elements (Kozitskaya, et al., 1978, pl. XXIII) range from triangular with poorly developed lobes to more rounded elements with well developed lobes at equivalent magnification. Nemyrovska et al. (1999) illustrated additional specimens of I.
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sagittalis from limestone O1 that are of the more rounded type with well developed accessory lobes and weak medial nodosity. Other species from Donets Basin (Kozitskaya et al., 1978) found in strata potentially correlateable with the Midcontinent include Idiognathodus toretzianus Kozitskaya, 1978 and I. bachmuticus Kozitskaya, 1978. Both species are not found in the Midcontinent. Idiognathodus
toretzianus ranges from limestone O2 to limestone P2 in Donets Basin (approximately Dennis Sequence and higher in the Midcontinent (Heckel et al., 2007)). The moderately restricted and continuous rostral lobe and reduced caudal lobe of I. toretzianus have no equivalent in the Midcontinent. Idiognathodus toretzianus is most similar to I. species 3 in the Midcontinent, but distinguished by the inset rostral lobe ornamented by a single node of I. species 3.
1 Idiognathodus bachmuticus is found in limestone O4 (approximately the Dewey Sequence, Heckel et al., 2007) and is very similar to specimens of I. corrugatus from the Midcontinent. The rostral lobe of I. bachmuticus is either highly reduced or missing as seen in I. corrugatus. Species similar to I. cancellosus and S. neverovensis (potentially I. biliratus) are also reported in Kozitskaya et al. (1978).
China Zhihao and Yuping (2003) presented a zonation of Chinese strata (Figure 15) containing numerous species potentially tying to North America. The clavatulus Zone contains species of Neognathodus, but marks the last occurrence of species of Neognathodus. Illustrated specimens of I. clavatulus (pl. 4, figs. 8, 10) are more similar to Swadelina neoshoensis Lambert et al. 2002 than I. clavatulus. The clavatulus Zone of Zhihao and Yuping (2003) likely represents the latest Desmoinesian (Moscovian) strata in China. The cancellosus Zone has only one illustrated specimen that appears to be a juvenile specimen similar to I. swadei. The gracilis‐excelsus Zone appears to contain the last occurrence of Swadelina at its base with Sw. nodocarinata (illustrated as S. excelsus, pl. 3, no. 1). The only other identifiable illustrated specimens from this Zone are specimens similar to I. trigonolobatus (illustrated as S. subexcelsus, pl. 3, figs. 10, 11, as S. oppletus pl. 3, fig. 20) and a specimen of I. turbatus (illustrated as S. cancellosus, pl. 4, fig. 21) that indicate most of the gracilis‐excelsus Zone of Zhihao and Yuping (2003) belongs to the interval prior to the first appearance of true Streptognathodus. The remaining fauna has species of true Streptognathodus but none illustrated have Midcontinent equivalents in the study interval.
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Spain Of the specimens illustrated by Méndez (2006) from the Cantabrian region of Spain, several specimens are similar to Midcontinent species and Eurasian species present within the study interval. A transitional specimen of I. eccentricus (fig. 5.14), a specimen of I. swadei (fig. 5.5), and a specimen similar to I. swadei or I. vorax (fig. 5.11) constitute specimens found both in Spain and the Midcontinent. A Streptognathodus species similar to S. neverovensis (figs. 5.8, 5.9) is found in the interval along with specimens similar to I. sagittalis (figs. 5.15, 5.16) and represent species found both in Spain and Moscow Basin. There are no species in this interval in Spain unique to the Cantabrian region.
Potential for Global Correlation Global correlation of Middle and Upper Pennsylvanian strata using species of Idiognathodus has been the focus of much attention in recent years. The push to define a GSSP and microfossil marker for the base of the Kasimovian Stage (base of the Upper Pennsylvanian Series) has led to a great deal of research in Eurasian sections. Correlation to the Midcontinent Basin from the Moscow Basin and Donets Basin (Figure 1) has been difficult due to the large number of endemic species in each region.
Selection of Global Events As discussed in the introduction, numerous scales of cyclicity are preserved in rocks from the Midcontinent Basin, and while the climatic drivers of sea level change are important, basin geometry and tectonic activity may alter the signal enough to create an offset from the global signature. The timing of highstands and lowstands, and the duration of these events, may vary from basin to basin despite a eustatic signal (Blaine et al., 2003). Studies of Pennsylvanian conodont faunas have indicated a high degree of provincialism during this time period (Charpentier, 1984; Barrick et al., 2000). Similar conclusions have been reached by workers in the fusulinid community (Groves et al., 2007; Groves, 2008). Most workers agree that there are few time intervals when North American faunas could communicate with Eurasian faunas. Groves et al. (2007) explains that the most likely reason for increased provincialism in the Middle and Late Pennsylvanian stems from the closing of a circumequatorial marine belt that separated Laurasia from Gondwana. This belt had allowed for relatively easy communication between global basins. Once the marine belt was closed, there
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was no effective way for shelf faunas to navigate the land mass except in time of extreme highstand. In comparing the faunas of the Midcontinent Basin (this study) with the faunas of the Moscow Basin (Alekseev and Goreva, 2007; Figure 15), South Ghizhou of China (Zhihao and Yuping, 2003; Figure 15), the Carnic Alps (Forke and Samankassou, 2000), and Northern Spain (Méndez, 2006), it is possible to recognize three distinct levels at which communication between basins was most likely. The three levels of communication are the Lost Branch Sequence (Nuyaka Creek Shale), the Swope Sequence (Hushpuckney Shale), and the Dewey Sequence (Quivira Shale). Figure 16 shows the possible levels of faunal communication and the relationship to the global sea level signature and the midcontinent sea level signature. The Lost Branch Sequence (Level A in Figure 16) can be compared to Moscow Basin, China, and Spain based on the last occurrence of species of Swadelina (approximated by the last occurrence of species of Neognathodus when Swadelina is absent). The loss of species of Swadelina is followed by the appearance of I. sulciferus in North America, the first appearance of I. sagittalis (Alekseev and Goreva, 2007, fig. 2) in Moscow Basin, the last appearance of Sw. nodocarinata in China (Zhihao and Yuping, 2003, pl. 3, no. 1), and is approximated by the last occurrence of N. aff. inaequalis (Méndez, 2006, fig. 5.7) in Spain. The Swope Sequence (Level B in Figure 16) can be compared to Moscow Basin, Spain and the Carnic Alps by I. cancellosus, I. biliratus, and S. neverovensis. The co‐appearance of I. cancellosus and I. biliratus in North America is correlated by the first co‐appearance of I. cancellosus (Alekseev and Goreva, 2007, pl. 1, figs. 19,20), and I. biliratus (Alekseev and Goreva, 2007, pl. 1, fig. 7) (approximated by the co‐occurrence of I. cancellosus and S. neverovensis) in Moscow Basin, approximated by the appearance of I. swadei (Méndez, 2006, fig. 5.5) and I. eccentricus (Méndez, 2006, fig. 5.14) along with S. neverovensis (Méndez, 2006, fig. 5.8, 5.9) in Spain, and the appearance of I. biliratus (Forke and Samankassou, 2000, pl. 37,fig. 13) with S. neverovensis in the Carnic Alps (Forke and Samankassou, 2000, pl. 37,figs. 14‐16). The Dewey Sequence (Level C in Figure 16) likely compares to the brief appearance of I. magnificus in the Moscow Basin following the extinctions of S. neverovensis and I. cancellosus and prior to the rise of I. aff simulator (Alekseev and Goreva, 2007, fig. 2). Stratigraphically these three levels of communication represent global highstand of the sea. The black shales of the Midcontinent high frequency sequences (Nuyaka Creek Shale, Hushpuckney Shale, and Dewey Shale) all appear to represent the maximum flooding surface for the global signature of the three composite sequences in this study. Interestingly, this conflicts
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with the selection of the maximum flooding surfaces for at least the Lower Missourian and Middle Missourian Composite Sequences. The sequences with high abundances of Gondolella species have been interpreted to represent the deepest waters in the composite sequence. The Hertha and Dennis Sequences are each one or more sequences below the level suggested by faunal communication above. The Midcontinent Basin’s early onset of maximum flood, highstand, and lowstand and long duration of highstand and lowstand does not allow for a one‐to‐one relationship between the midcontinent sea level curve and the global sea level curve. This relationship is best expressed by the extinctions at the end of the Lost Branch Sequence. In the Midcontinent Basin species of both Swadelina and Neognathodus went extinct at the sequence boundary for the overlying Middle Missourian Composite Sequence. In Moscow Basin, this extinction is staged. Species of Neognathodus went extinct prior to the extinction of species of Swadelina. The extinction of Sw. makhlinae was followed by a major unconformity. The subexcelsus Zone and makhlinae Zone in Moscow Basin likely occurred during the time period when the Midcontinent Basin was at lowstand; undergoing erosion on the shelf and deposition of sands in the basin. The preservation of the staged extinction in Moscow Basin but coeval extinction in the Midcontinent supports the idea that the Midcontinent is offset so that its maximum floods, highstands, and lowstands are earlier than the global signature. The Lost Branch Sequence (Nuyaka Creek Shale), Swope Sequence (Hushpuckney Shale), and Dewey Sequence (Quivira Shale) represent the three levels at which there is a high probability of faunal communication between basins. Faunal similarity in time periods between each of the three levels above is very low. Each basin develops its own unique fauna along independent lineages during these times. The levels with increased faunal communication allow for a higher probability of finding a truly cosmopolitan conodont species to indicate the global Moscovian‐Kasimovian Stage Boundary. The proximity of these sequences to potentially global composite sequence boundaries (and lowstand events) places greater event significance on these levels as choices for the global Moscovian‐Kasimovian Stage boundary.
Boundary Definition Three proposals for the conodont marker and level of the GSSP for the Moscovian‐ Kasimovian Global Stage Boundary will be discussed and evaluated in terms of probability of faunal communication, likely candidates for a cosmopolitan species of conodont to mark the
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boundary, and the nature of the global event being marked. Proposal A is the base of Lower Missourian Composite Sequence as marked by the last occurrence of species of Swadelina. Proposal B is at the current Desmoinesian‐Missourian Regional Stage Boundary using as markers a complex combination of Idiognathodus sagittalis, I. eccentricus, I. turbatus, and I. swadei. Proposal C is the base of the Swope Sequence marked by co‐occurrence of I. cancellosus and I. biliratus.
Moscovian‐Kasimovian Boundary – Proposal A This proposal is the closest to the current regionally accepted base of the Kasimovian in Russia and Ukraine. The base of the Lower Missourian Composite Sequence, base of the Hepler high frequency sequence is a major lowstand event that is global in significance (Heckel, 2008). In the Midcontinent Basin, species of both Neognathodus and Swadelina are lost at this unconformity. In the Moscow Basin, species of Swadelina are the last to be lost, and they are lost at an unconformity. The connection of the loss of species of Swadelina with a major unconformity associated with a global lowstand event makes the last occurrence of species of Swadelina an attractive choice for the Moscovian‐Kasimovian Boundary. Although last occurrences are notoriously difficult to recognize globally, the proximity to the major lowstand and explosion of diversification of distinctive faunas following the lowstand make this an easily identifiable level. One potential problem is the current placement of the Desmoinesian‐Missourian Regional Stage Boundary. Assuming both regional stages should be tracking the same global event, the two boundaries would be offset and of differing significance. While the placement of the Desmoinesian‐Missourian Boundary at the first occurrence of Idiognathodus eccentricus is an easy pick because of the uniqueness of I. eccentricus, the development of true Missourian species of Idiognathodus begins one sequence lower. The base of the truly Missourian Idiognathodus lineage is at the base of the Hepler Sequence with the first appearance of I. sulciferus. Prior to Heckel et al. (2002) the traditional base of the Missourian had been at the base of the Hepler Sandstone. If the Moscovian‐Kasimovian Boundary was selected to be at the level proposed here, the Desmoinesian‐Missourian Boundary should be redefined to correctly mark the development of the Missourian lineage of Idiognathodus and to co‐exist with the Moscovian‐Kasimovian Boundary.
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Moscovian‐Kasimovian Boundary – Proposal B The proposal to mark the Moscovian‐Kasimovian Boundary at the first appearance of Idiognathodus sagittalis has received the most attention from the Moscovian‐Kasimovian (Middle‐Upper Pennsylvanian) boundary task group (IUGS Subcommission on Carboniferous Stratigraphy) (Villa et al., 2004, 2005, 2006). Alekseev and Goreva (2006) stated that I. sagittalis is widely distributed in Eurasia, being reported from the Central Russian Platform, the Volga‐ Ural region, South Urals, northern Timan, northern Spain, and the Midcontinent Basin (Heckel et al., 2005, 2007). The completion of this study and Rosscoe and Barrick (In Press) indicate that no specimens of I. sagittalis have been found in the Midcontinent Basin. In the Midcontinent Basin, there are two species similar to, but distinct from, Idiognathodus sagittalis. Idiognathodus sagittalis has a distinctively bounded, lower‐elevation rostral lobe that can be used to distinguish it from I. swadei. Idiognathodus swadei does not have the weak medial disruption seen in many specimens of I. sagittalis. Several specimens of I. swadei beginning in the Hepler Sequence do have a distinctively bounded rostral lobe, but the lobe is at the same elevation, not a lower elevation as seen in I. sagittalis. Several differences distinguish I. turbatus from I. sagittalis. The rostral lobe of I. sagittalis is very robust but is separate and lower in elevation from the central platform of the element, whereas the rostral lobe in I. turbatus is level with and merges with the central platform. The rostral lobe of I. sagittalis protrudes more than the rostral lobe of I. turbatus. The caudal lobe of I. sagittalis is smaller and contains less discrete ornamentation than specimens of similar size from I. turbatus. The medial nodosity of I. turbatus is far more dramatic than the weak medial node row that can be seen in the holotype of I. sagittalis. Although the absence of true Idiognathodus sagittalis in the Midcontinent could derail this option, there are several other options to correlate a boundary that lies at the FAD of I. sagittalis. A distinctively bounded, but equal elevation lobe appears in specimens of I. swadei in the Hepler Sequence. Also, one level higher in the Shale Hill Sequence, I. turbatus, also similar to I. sagittalis appears. These two sagittalis‐like forms could be used to approximate the coeval development of sagittalis characters in both the Moscow and Midcontinent Basins. In addition, the first appearance of I. eccentricus is at Shale Hill Sequence. Heckel et al. (2007) reported the occurrence of specimens similar to I. eccentricus from beds in the Moscow Basin (I. aff. eccentricus of Goreva et al., 2007) interpreted to be equivalent to the Shale Hill Sequence and
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from beds in the Donets Basin equivalent to the Hertha Sequence. Idiognathodus eccentricus was also reported by Méndez (2006) in the Cantabrian Zone of Northern Spain. The first appearance of I. sagittalis in the Moscow Basin follows the extinction of species of Swadelina, which places the base of Kasimovian near the current base of the Kasimovian in Russia and Ukraine. The problem with the use of I. sagittalis as a marker for the Moscovian‐ Kasimovian Boundary is its approximation in Midcontinent Basin. If the appearance of distinctively bounded specimens of I. swadei is used to approximate the development of sagittalis‐like characteristics the placement of the boundary would be at or near the base of the Hepler Sequence. If the appearance of I. turbatus is used the boundary would be placed at the base of the Shale Hill Sequence. The base of the Hepler corresponds to the boundary proposed in proposal A. The base of the Exline Limestone in the Shale Hill Sequence corresponds with the current placement of the Desmoinesian‐Missourian Regional Stage Boundary at the first appearance of I. eccentricus.
Moscovian‐Kasimovian Boundary – Proposal C This proposal places the Moscovian‐Kasimovian Boundary at a global highstand event that occurs in the Swope Sequence of the Lower Missourian Composite Sequence. The species I. cancellosus, I. biliratus and S. neverovensis can be used to correlate this event globally. Idiognathodus cancellosus has been reported by Alekseev and Goreva (2007) in the Moscow Basin. In addition, one specimen of I. biliratus has been recognized in the Moscow Basin and occurs with a similar species S. neverovensis (Goreva and Alekseev, 2006). The similarity between I. biliratus and S. neverovensis is so striking and I. biliratus is so different from all other Midcontinent species of Idiognathodus it is possible that I. biliratus is a relative of S. neverovensis that travelled to the Midcontinent Basin at the same time that I. cancellosus travelled to the Moscow Basin. The first appearance of I. cancellosus and I. biliratus occurs at the base of the Swope Sequence. The appearance of I. cancellosus and I. biliratus in the Moscow Basin may be used to correlate this highstand event. The appearance of I. cancellosus and S. neverovensis can be used to approximate the highstand, but S. neverovensis appears before the first appearance of I. cancellosus. Specimens of I. biliratus have also been identified in the Carnic Alps (Forke and Samankassou, 2000). Specimens of I. cancellosus have been identified in China as well (Zhihao and Yuping 2003).
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Proposal C seems to be the best in achieving the goals of selecting an easily identifiable marker species (Idiognathodus cancellosus and I. biliratus). As with proposal A, this proposal does not match with the current placement of the Desmoinesian‐Missourian Regional Stage Boundary, but is tracking a significantly different event. The major drawback to this proposal is that it is significantly higher than the current base of the Missourian, and even higher than the traditional base of the Missourian and the traditional base of the Kasimovian. In addition, this event does not have the attractive faunal turnover that is seen at the traditional bases of the Missourian and Kasimovian.
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SEQUENCES ZONES/SUBZONES
Dewey I. multinodosus Sequence
I. multinodosus
Cherryvale Sequence I. symmetricus
e Sequence
S. gracilis
I. symmetricus
Hogshooter Sequence S. gracilis
I. magnificus
S. excelsus
S. gracilis
Dennis Sequence I. cherryvalensis
I. cherryvalensis
Middle Missourian Composit
Mound Valley Sequence
new species 2
I.
I. cancellosus I. clavatulus
Swope Sequence
I. clavatulus
I. biliratus
I. cancellosus MKB - Proposal C
e Sequence Hertha Sequence I. eccentricus
I. vorax
Shale Hill Sequence
I. turbatus I. eccentricus Current D-M Boundary MKB - Proposal B Hepler I. swadei Lower Missourian Composit Sequence
I. sulciferus Traditional D-M Boundary
distinctively bounded specimens MKB - Proposal A Lost Branch Sequence Sw. nodocarinata
N. roundyi
Marmaton
Swadelina
Neognathodus
I. swadei
Figure 14: Conodont zonation for the Midcontinent Basin and proposals for the location of the Moscovian-Kasimovian (Middle-Upper Pennsylvanian) Boundary. Sequences indicated with black boxes and white lettering are those formed during global highstand conditions. These sequences are most likely to contain a globally correlatable fauna. MKB = Moscovian-Kasimovian Boundary.
65 Zhihao & Yuping, 2003 Alekseev & Goreva, 2007 Merrill, 1971 Barricket al. , 2004 This Dissertation, 2008 China Moscow Basin Appalachian Basin Midcontinent Basin Midcontinent Basin S. firmus S. firmus I.aff. simulator Above Study Interval I.aff. simulator
S. excelsus - I. toretzianus S. gracilis S. guizhouensis S. gracilis S. gracilis I. multinodosus I. symmetricus
Dorogomilovian
Missourian S. gracilis
Kasimovian I. mestsherensis S. confragus Missourian S. cancellosus - I. cherryvalensis , University, Tech Texas S. oppletus 66 Lowstand I. cancellosus
Dalaan S. gracilis - S. excelsus S. cancellosus S. cancellosus I. clavatulus
I. delicatus - I. eccentricus I. sagittalis S. cancellosus 2002
Khamovnikian I. eccentricus I. sulciferus Sw. makhlinae 2008 August Rosscoe J. Steven S. cancellosus Hepler Sequence - Lowstand
Krevy- S. subexcelsus
akinian Sw. nodocarinata N. roundyi Sw. nodocarinata
N. roundyi o) S. clavatulus Sw. neoshoensis N. roundyi I. delicatus Below Study Interval
Below Desmoinesian
N. roundyi
(sensu lat
Myachkovian Sw. nodocarinatus Moscovian Study Interval Desmoinesian I. iowaensis Figure 15: Comparison of conodont zonations globally and regionally with the zones proposed in this dissertation. The current base of the Missourian is marked by “2002” in the Midcontinent Zonations (Heckelet al ., 2002). The traditional base is indicated in the Merrill Zonation. Texas Tech University,Steven J. Rosscoe , August 2008
Global Sea Level MidC. Sea Level Midcontinent Basin Moscow Basin - 0 + - 0 + Conodonts Conodonts
? Chanute S.S.
Middle Quivira Sh. C Missourian Composite Sequence
I. magnificus
I. sagittalis
I. neverovensis
I. multinodosus
Stark Sh.
St. gracilis
St. excelsus Ladore Sh.
I. magnificus
I. swadei
I. eccentricus
I. clavatulus
Lower Missourian Hushpuckney B Composite Sh. Sequence aff.
I. cancellosus
I. biliratus
I. biliratus
I. cancellosus
I. confragus Mound I. cancellosus City Sh.
Sw. makhlinae
I. trigonolobatus
Marmaton
Hepler S.S. N. roundyi
Composite Sw. nodocarinatus
N. roundyi Sequence Nuyaka Creek Sh. A Figure 16: Global and local controls on sea level and their effect on conodont based correlations between North America (Midcontinent Basin) and Eurasia (Moscow Basin). Major lowstands indicated by gray boxes. I =Idiognathodus , N = Neognathodus , St = Streptognathodus , Sw = Swadelina.Lettered boxes indicate the most correlatable levels. The Moscow Basin ranges have been interpreted from Alekseev and Goreva, 2007. 67 Texas Tech University, Steven J. Rosscoe, August 2008
CHAPTER 5 CONCLUSIONS
Large collections of Idiognathodus from the Desmoinesian (~ Moscovian/Middle Pennsylvanian) Lost Branch Sequence to the Missourian (~ Kasimovian/Upper Pennsylvanian) Dewey Sequence in Midcontinent North America allow revision of species‐level taxonomy.
Taxonomic characters that reflect the interpreted function of the P1 element of Idiognathodus, the rostral lobe and surface roughness of the platform, are emphasized in species definition and characterization. Idiognathodus swadei Rosscoe and Barrick (In Press) is the only Idiognathodus species to survive the extinction level near the end of the Desmoinesian. Idiognathodus expansus Stauffer and Plummer, 1932, disappears, and I. swadei becomes the stem form from which early Missourian species of Idiognathodus evolve in the Midcontinent Basin. The sulciferus Zone (Hepler Sequence) has been established to represent the period of time following the extinction of the genus Neognathodus and the first appearance of the distinctively grooved species Idiognathodus eccentricus (Ellison, 1941). During this interval the swadei lineage gave rise to the sulciferus lineage with the first appearances of I. sulciferus Gunnell, 1933, and I. harkeyi Gunnell, 1933. The eccentricus Zone (Shale Hill and Hertha sequences) constrains the period of time following the first appearance of I. eccentricus to the first appearance of I. cancellosus (Gunnell, 1933). It is during this interval that both lineages developed species with disrupted or chaotic platform ornamentation (I. turbatus and I. eccentricus). The cancellosus Zone (Swope, Mound Valley, and Dennis sequences) is split into two Subzones. The clavatulus Subzone (Swope and Mound Valley sequences) includes the interval between the first appearance of Idiognathodus clavatulus (Gunnell, 1933) and the first appearance of I. cherryvalensis Gunnell, 1933. During this time, there is a shift from expanded and robust to small and reduced rostral lobes. The early part of this Subzone is notable for its maximum diversity of Idiognathodus (18 species). It is in the Swope Sequence that there is recognizable communication between the Midcontinent Basin and other global basins with the species I. cancellosus and I. biliratus Gunnell, 1933. Nine species are lost from the Swope to the Mound Valley Sequence. The cherryvalensis Subzone (Dennis Sequence) constrains the interval between the first appearance of I. cherryvalensis and the first appearance of Streptognathodus gracilis Stauffer and Plummer, 1932. This Subzone is most notable for the last appearance of the
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all species from the swadei lineage. Only the sulciferus lineage of Idiognathodus lasts beyond the end of the cancellosus Zone. The gracilis Zone (Hogshooter, Cherryvale, and Dewey sequences) is split into at least three Subzones. The gracilis Subzone (Hogshooter Sequence) is defined as the interval between the first appearance of Streptognathodus gracilis and the first appearance of Idiognathodus symmetricus Gunnell, 1933. This Subzone marks the first appearance of species of Streptognathodus; five species at the start of this Subzone. The symmetricus Subzone (Cherryvale Sequence) is defined as the interval between the first appearance of I. symmetricus and the first appearance of I. multinodosus Gunnell, 1932. The only new species added in this Subzone is I. symmetricus. The multinodosus Subzone (Dewey Sequence) starts at the first appearance of I. multinodosus. The top of the S. gracilis Zone is the first appearance of I. aff. simulator. At present, the species S. sulcatus Gunnell, 1933, appears to go extinct in this Subzone. The Eurasian species Idiognathodus sagittalis Kozitskaya 1978, which has been proposed as the biostratigraphic index for the Moscovian‐Kasimovian boundary, is not recognized in our Midcontinent collections. It is most similar to species of the swadei lineage, but differs in several features. Idiognathodus turbatus is similar to I. sagittalis and may be used to informally correlate the base of the Kasimovian, along with distinctively bounded specimens of I. swadei. Idiognathodus eccentricus, a useful index for the base of the Missourian in the Midcontinent region, may be a good candidate for global correlation of the base of the Upper Pennsylvanian if its occurrence in Eurasian sections can be confirmed. Other proposals include a base of the Kasimovian at the extinction of species of Swadelina or the base of the Kasimovian at the first coeval occurrence of I. cancellosus and I. biliratus. Both of these proposals have the added benefit of being tied to a global lowstand or highstand, respectively.
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APPENDIX A
LOCALITY REGISTER
Introduction The conodont collections for this study include the existing collections of Dr. Jim Barrick and additional collections generated from new or recollected localities. Existing collections will be noted and their location described by PLS Coordinates, common amongst workers in the Midcontinent. New or recollected localities are illustrated with measured section (where substantial work was done) or by photo (when only grab samples were taken) and their location described using latitude‐longitude GPS coordinates. The sections are arranged in stratigraphic order and noted with their abbreviation for use in Figure 2. Figure 17 is a key to the symbols used in the measured sections and other figures throughout the paper.
Locality Register
LITTLE RIVER (LR) – Seminole County, OK (Heckel, 1991, p. 57, outcrop 34) PLS Coordinates: SW‐NE‐SE‐NW sec. 25, T. 6N, R. 7E, Sasakwa Quadrangle Notes: Lost Branch and Hepler sequences (Figure 18 – Lost Branch Sequence) Collected by: Jim Barrick and Darwin Boardman
SOUTH SASAKWA (SS) – Seminole County, OK (Heckel, 1991, p. 57, outcrop 35) PLS Coordinates: SE‐SW‐SE sec. 12, T. 5N, R. 7E, Sasakwa Quadrangle Notes: Lost Branch Sequence (Figure 19) Collected by: Jim Barrick and Darwin Boardman
LITTLE CALIFORNIA CREEK (LCC) – Nowata County, OK (Heckel and Watney, 2002, p. 58, sec. 21) PLS Coordinates: W1/2‐SE sec. 10, T. 27N, R. 15E, Delaware Quadrangle Notes: Hepler Sequence Collected by: Jim Barrick and Darwin Boardman, Phil Heckel and John Pavlicek
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SOUTH MOUND REFERENCE (SM) – Neosho County, KS (Heckel and Watney, 2002, p. 57, sec. 26) PLS Coordinates: NE‐NE‐NE‐NW sec. 15, T. 30S, R. 19E, South Mound Quadrangle Notes: Hepler Sequence Collected by: Phil Heckel
TYPE CHECKERBOARD (TC) – Okmulgee County, OK PLS Coordinates: E1/2 sec. 22, T. 15N, R. 11E, Kiefer SW and Lake Boren Quadrangles Notes: Hepler Sequence Collected by: Jim Barrick and Darwin Boardman
KIMBALL EAST (KM) – Neosho County, KS (Heckel and Watney, 2002, p. 58, sec. 21) PLS Coordinates: SW‐SW‐SE‐SW sec. 27, T. 27S, R. 21E, Porterville Quadrangle Notes: Shale Hill Sequence Collected by: Phil Heckel
SECTION 75/71 (75‐71) – Tulsa County, OK (Bennison et al., 1984, p. 45, fig. 36) PLS Coordinates: NW‐NE‐NW sec. 11, T. 18N, R. 12E, Sapulpa North Quadrangle Notes: Shale Hill Sequence Collected by: Jim Barrick and Darwin Boardman
US69 OUTCROPS – Linn County, KS (Heckel and Watney, 2002, p. 12, fig. 7) PLS Coordinates: NW‐NW‐SW sec. 19, T. 22S, R. 25E, Prescott Quadrangle Notes: Shale Hill Sequence Collected by: Phil Heckel
UNIONTOWN K‐3 (UT) – Bourbon County, KS (Heckel and Watney, 2002, p. 56, section 17) PLS Coordinates: E1/2‐SE‐NW sec. 34, T. 25S, R. 25E, Uniontown Quadrangle Notes: Hepler, Shale Hill, Hertha, and Swope sequences (Figure 20A, 20B) Collected by: Jim Barrick
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TACKETT MOUND 1 (TM) – Labette County, KS (Heckel and Watney, 2002, p. 18, figure 13) PLS Coordinates: SW‐NE‐NE‐SW, sec. 7, T. 32S, R. 19E, Parsons West Quadrangle Notes: Hertha Sequence (Figure 21) Collected by: Jim Barrick
FORT CALHOUN QUARRY (FCQ) – Washington County, NE GPS Coordinates: 41°27.654’ N ‐ 96°00.773’W Notes: Hertha, Swope, Dennis, Cherryvale, and Dewey sequences (Figure 22A, 22B) Collected by: Peter Holterhoff and Steve Rosscoe
JINGO US69 (J69) – Miami County, KS GPS Coordinates: 38°25.968’ N ‐ 94°41.122’W Notes: Swope, Dennis, Hogshooter, and Cherryvale sequences (Figures 23A, 23B, 37A) Collected by: Steve Rosscoe
MASON ROAD (MR) – Okfuskee County, OK GPS Coordinates: 35°33.963’ N ‐ 96°17.300’W Notes: Swope Sequence (Figure 24) Collected by: Steve Rosscoe and Peter Holterhoff
CLEAR CREEK (CC) – Seminole County, OK GPS Coordinates: 34°55.546’ N ‐ 96°34.894’W Notes: Swope Sequence (Figure 25) Collected by: Steve Rosscoe
PWA Quarry (PWA) – Sarpy County, NE (Heckel et al., 1979, p. 52‐53, stop 19A) PLS Coordinates: NE‐SE, sec. 20, T. 13N, R. 12E, Cedar Creek Quadrangle Notes: Swope Sequence (Hushpuckney Shale and Bethany Falls) Collected by: Phil Heckel
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EAST OF PERU (EP) – Madison County, IA (Heckel and Pope, 1992, p. 26, stop 3) PLS Coordinates: West Line E1/2‐NW1/4, sec. 12, T. 74N, R. 27W, East Peru Quadrangle Notes: Swope Sequence Collected by: Jim Barrick
COFFEYVILLE SOUTHWEST (CSW) – Montgomery County, KS GPS Coordinates: 36°58.878’ N ‐ 95°40.846’W Notes: Mound Valley Sequence (Figure 26) Collected by: Peter Holterhoff
BIG CREEK (BC) – Neosho County, KS GPS Coordinates: 37°40.899’ N ‐ 95°18.905’W Notes: Mound Valley and Dennis sequences (Figure 27) Collected by: Steve Rosscoe and Peter Holterhoff
MOUND VALLEY REFERENCE (MVR) – Neosho County, KS GPS Coordinates: 37°35.964’ N ‐ 95°15.122’W Notes: Mound Valley Sequence, grab sample (Figure 37B) Collected by: Steve Rosscoe
RAMONA RAIL CROSSING (RRC) – Washington County, OK GPS Coordinates: 36°32.117’ N ‐ 95°55.581’W Notes: Dennis and Cherryvale sequences (Figures 28, 37C) Collected by: Steve Rosscoe, Peter Holterhoff, Jim Barrick
HOGSHOOTER SOUTH (HS & BNH) – Washington County, OK GPS Coordinates: 36°41.068’ N ‐ 95°51.072’W (HS), 36°40.725’ N ‐ 95°51.075’W (BNH) Notes: Dennis, Hogshooter, and Cherryvale sequences (Figure 29) Collected by: Steve Rosscoe, Jim Barrick, Peter Holterhoff
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EAST OF OCHELATA (OCH) – Washington County, OK GPS Coordinates: 36°33.467’ N ‐ 95°55.714’W Notes: Hogshooter and Cherryvale sequences (Figures 30, 37E) Collected by: Steve Rosscoe
SHIRK EAST (SE) – Creek County, OK GPS Coordinates: 36°07.186’ N ‐ 96°07.168’W Notes: Dennis Sequences (Figure 37D) Collected by: Steve Rosscoe and Jim Barrick
ZINK RANCH (ZR) – Osage County, OK GPS Coordinates: 36°15.940’ N ‐ 96°04.052’W Notes: Dennis, Hogshooter, and Cherryvale sequences (Figure 31) Collected by: Steve Rosscoe
HOGSHOOTER QUARRY (HQN, HQS) – Washington County, OK GPS Coordinates: 36°45.034’ N ‐ 95°48.768’W Notes: Hogshooter and Cherryvale sequences (Figure 32) Collected by: Peter Holterhoff, Jim Barrick, Phil Heckel, and Jeremy Bader
BANNISTER ROAD (BR) – Jackson County, MO GPS Coordinates: 38°57.240’ N ‐ 94°33.320’W Notes: Cherryvale Sequence (Figure 33) Collected by: Peter Holterhoff
DRUM REFERENCE (DR) – Montgomery County, KS GPS Coordinates: 37°13.414’ N ‐ 95°34.907’W Notes: Cherryvale Sequence (Figure 34) Collected by: Steve Rosscoe
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SKIATOOK DAM (SD) – Osage County, OK GPS Coordinates: 36°20.980’ N ‐ 96°04.998’W Notes: Dewey and Iola sequences (Figure 35) Collected by: Steve Rosscoe
KAW DRIVE (KAW) – Johnson County, KS GPS Coordinates: 39°6.199’ N ‐ 94°40.961’W Notes: Dewey and Iola Sequences (Figures 36, 37F) Collected by: Steve Rosscoe
FALCON MATERIALS PIT 1 (HFM) – Seminole County, OK GPS Coordinates: 35°05.009’ N ‐ 96°33.979’W Notes: Dewey Sequence (grab samples) Collected by: Steve Rosscoe
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Key to Measured Sections/Columns Key to Diagrammatic Cross Sections 5 Thick Bedded Major Limestone Units Oolitic Limestone
Algal Limestone Terrestrial Shales
Thin Bedded Limestone
4 Argillaceous Limestone Sandstones
Silty Shale Shaly Sands Siltstone Sandstone Gray - Dark Gray Shale Covered/Missing Interval 3 Nodular Limestone Black Shale Limestone Concretions
ters Coal Sample Site 14 and Number
Shaley Limestone Scale in Me Key to Biological Symbols Limestone conodonts 2 crinoids Ooid Limestone Phosphatic Limestone corals annelids Shale and Limestone brachiopods Interbeds bryozoans Phosphatic Shale ostracodes
1 Black Shale gastropods fish spicules Gray to Dark Gray Shale forams mollusks
Brown/Clay Shale
Mottled Limestone 0 Coal
Figure 17: Key to measured sections (Appendix A) and diagrammatic cross sections (Figures 4 and 5). Measured sections and biological symbols adapted from the National Geologic Mapping Database Digital Standards.
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Little River SW-NE-SE-NW sec. 25 T. 6N, R. 7E. LR Sasakwa Quadrangle
3
105
104 2 Nuyaka Creek Shale
103
102 1
101
15
10 Homer School 0 Figure 18: Measured section for Little River. This outcrop is a stream and ravine exposure in Seminole County, OK. Illustrated here is the Lost Branch Sequence only. The section does extend into the Hepler Sequence further along the stream. Section measured by Jim Barrick and Darwin Boardman. 84 Texas Tech University,Steven J. Rosscoe , August 2008
Roadditch South of Sasakwa SE-SW-SE sec. 12, T. 5N, R. 7E. SS Sasakwa Quadrangle 5 10 15 216
215
214 Glenpool 4 Covered 9 14 Limestone Interval 213
212
Nuyaka Creek 211 Shale 15 3 8 13 14 210
13 Covered 12 Interval Covered Interval 11.1
10.1 2 7 12 9.1 190 9 Upper 8 Holdenville Shale 7 Homer School 180 1 6 6 11 5
Covered Interval
0 5 10
Figure 19: Measured section for the Roadditch South of Sasakwa. The section is exposed in the roadditch along EW 145th Road in Seminole County Oklahoma. This section was measured by Jim Barrick and Darwin Boardman. Note: This section is now overgrown and mostly filled in.
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Uniontown K-3 E1/2-SE-NW sec. 34, T. 25S, R. 22E UT - Uniontown, KS Uniontown Quadrangle 5 10 15
E5 Guthrie Mountain Covered Mantey Shale Shale Interval
4 9 14 E13 Covered Guthrie Interval E12 Critzer Mountain Limestone Shale E11 E16 Exline Limestone E10 3 8 E9 13 E4
E3
E8 Covered Interval
2 7 12
Covered E15 Interval
E2
E14
1 6 E7 11 South Mound Shale Guthrie Mantey Mountain Shale Shale E6
0 E1 5 10
Figure 20A: Measured section for Uniontown K-3. This outcrop is exposed along Kansas 3 south of Uniontown, KS. This portion of the exposure includes the roadditch and roadside outcrop along the eastern side of the highway. Measured by Jim Barrick and Darwin Boardman. 86 Texas Tech University,Steven J. Rosscoe , August 2008
Uniontown K-3 - Continued E1/2-SE-NW sec. 34, T. 25S, R. 22E UT - Uniontown, KS Uniontown Quadrangle 20 25 30
Sniabar Limestone W23 W30
W22 19 24 W27 29 W21 Mound City Shale W20
W19
18 W18 23 28 Covered Interval
W17 W26
17 22 27
W29
Covered 16 21 W25 26 Interval
W28
W24 15 20 25 Figure 20B: Continuation of the measured section for Uniontown K-3. This outcrop is exposed along Kansas 3 south of Uniontown, KS. This portion of the exposure is the roadside outcrop along the western side of the highway. Collected and measured by Jim Barrick and Darwin Boardman. 87 Texas Tech University,Steven J. Rosscoe , August 2008
Tackett Mound 1 SW-NE-NE-SW sec. 7 T. 32S, R. 19E TM Parsons West Quadrangle, Kansas
4
Covered Interval
29 28 27 26 3 25 24
23 Mound City 22 Shale
21
20 2
Covered Interval
13 12 1 11 10
8 7 0 6
Figure 21: Measured section for Tackett Mound I. This outcrop is along the stream below the ponds at the Tackett Mound. Section was collected and measured by Jim Barrick. 88 Texas Tech University,Steven J. Rosscoe , August 2008
Fort Calhoun Quarry 41 27.654’ N, 96 00.773’W FCQ Fort Calhoun, NE 5 10 15
3 Hushpuckney Shale
Galesburg 2 4 9 14 Shale
Bethany Falls Limestone 3 8 13
2 7 12
Bethany Falls Limestone Sniabar Limestone 1 6 11
Hushpuckney Shale 0 1 5 10
Figure 22A: Measured section for Fort Calhoun Quarry. This quarry exposure spans the interval from the Mound City Shale (Hertha Sequence) to the Cement City Limestone (Dewey Sequence) in eastern Nebraska. Measured and collected by Peter Holterhoff and Steve Rosscoe. 89 Texas Tech University,Steven J. Rosscoe , August 2008
Fort Calhoun Quarry - Continued 41 27.654’ N, 96 00.773’W FCQ Fort Calhoun, NE 20 25
Missouri River Sands
17
19 24 29
Winterset Limestone Cement City Limestone Westerville Limestone 18 23 28
15
14
17 22 27 Stark 13 Shale 12 4
Wea 11 Shale 16 21 26 Quivira 5 Shale 10 Galesburg 9 Shale 8 7
15 20 25 Figure 22B: Continuation of measured section for Fort Calhoun Quarry. This quarry exposure spans the interval from the Mound City Shale (Hertha Sequence) to the Cement City Limestone (Dewey Sequence) in eastern Nebraska. Measured and collected by Peter Holterhoff and Steve Rosscoe. 90 Texas Tech University,Steven J. Rosscoe , August 2008
Jingo - Kansas 69 38 25.968’ N, 94 41.122’ W J69 Jingo, Kansas 69 - East Cut 5 10 15 25
Galesburg 24 4 9 Shale 14 12 Lower Bethany Falls Winterset Limestone Limestone 8 23
3 8 13 11 10 22 21 20 7 19 6 18 2 7 12 17
5 4b 4a 16 Bethany Falls Stark Limestone Shale
1 3 6 11 Hushpuckney Shale 15 14 13
Galesburg 9 2 Shale 1 0 Middle Creek5 10 Figure 23A: Measured section for Jingo - Kansas 69. This outcrop is on the East side of Kansas 69 just North of the exit for Jingo, Kansas. Exposures both North (lower) and South (upper) of the K69 Bridge. Phosphatic limestone from 10.5-10.6 meters is Canville. Collected and Measured by S. Rosscoe. 91 Texas Tech University,Steven J. Rosscoe , August 2008
Jingo - Kansas 69 - Continued 38 25.968’ N, 94 41.122’ W J69 Jingo, Kansas 69 - East Cut 20 25
Upper Winterset (Hogshooter?) Limestone
19 24 30 35(4) 29 28 Fontana 27 Shale
18 23 34(3)
Lower 17 22 27 Winterset 33(2) Limestone 32(1)
Soil Cover Top of Hill
Upper Winterset (Hogshooter?) 38(7) 16 21 Limestone 26
Block Limestone
26 Switch to South 37(6) 15 20 31 25 36(5)
Figure 23B: Continuation of the measured section for Jingo - Kansas 69. This outcrop is on the East side of Kansas 69 just North of the exit for Jingo, Kansas. Exposures both North (lower) and South (upper) of the K69 Bridge. 92 Texas Tech University,Steven J. Rosscoe , August 2008
Mason Road 35 33.963’ N, 96 17.300’W MR Mason, Oklahoma
3
CoveredtoTop
6 2 5
4
3 1 Hushpuckney Shale 2 1
X 0
0 Figure 24: Measured section for Mason Road. Exposure is the cutbank of the east branch of Buckeye Creek 3.6 miles East of Mason, Oklahoma. Exposure is poor and conodonts from the shales shows signs of post-depositional weathering. Collected by S. Rosscoe.
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Clear Creek 34 55.546’ N, 96 34.894’ W CC South of Sasakwa, Oklahoma 5
9 8b 8a
4
7
3
5
4 3 2 7
2
1 6
111 1
0 5 110
Figure 25: Measured section Clear Creek (Frances/Hushpuckney Shale). This outcrop is a shale bank on the cutbank of Clear Creek, south of Sasakwa, Oklahoma prior to its confluence with the Canadian River. NOTE: no sample 6 was taken. Collected by S. Rosscoe. 94 Texas Tech University,Steven J. Rosscoe , August 2008
Coffeyville Southwest 36 58.878’ N, 95 40.846’ W CSW South of Coffeyville, KS
1
3 Mound Valley Limestone 2
1 0
Figure 26: Measured section for Coffeyville Southwest. This outcrop is in a ditch tributary to the creek southwest of Coffeyville, KS. This is a rare exposure of a shale break within the Mound Valley Limestone. Collected and measured by Peter Holterhoff. 95 Texas Tech University,Steven J. Rosscoe , August 2008
K39 at Big Creek 37 40.899’ N, 95 18.905’ W BC East of Chanute, KS 5 14
Lower Winterset 4 13 Limestone 18
1
3 12 17
Mound Valley Limestone 2
2 11 16
Stark Lower Shale Winterset Limestone
1 10 Canville 15 Limestone
Covered Interval (Skipped Scale)
0 0 5 14 Figure 27: Measured section for K-39 at Big Creek. This outcrop along Kansas 39 consist of a lower section along the bank of Big Creek (north of the K-39 bridge)(Mound Valley Sequence) and an upper section along the eastbound lane (Dennis Sequence). Measured by Peter Holterhoff. Samples collected by Steve Rosscoe and Peter Holterhoff. 96 Texas Tech University,Steven J. Rosscoe , August 2008
Ramona Railroad Crossing 36 32.117’ N, 95 55.581’ W RRC Ramona, Oklahoma 5
Covered by New Growth
4
3 8
Winterset Limestone Mound Covered Along Hill Top
13 2 7 12
8 11 7 Stark 6 Shale Hogshooter 5 Limestone 4 10 1 Canville 6 Limestone
3 9 2
0 1 5
Figure 28: Measured section for Ramona Railroad Crossing. Exposure is along the South side of Double Creek at the Santa Fe railroad trestle behind the school in Ramona, Oklahoma. Section shows incredible dynamics of deposition (see Figure 37C). Collected by S. Rosscoe. 97 Texas Tech University,Steven J. Rosscoe , August 2008
Hogshooter South & New Harmony HS- 36 41.068’ N, 95 51.075’ W HS & BNH BNH - 36 40.725’ N, 95 51.564’ W 5 Hogshooter, Oklahoma
Fontana Shale
BNH0
4 9
BNH3 Winterset Limestone New Harmony Shale 3 8
BNH2 BNH1
2 7
Fontana Bennison 84 Shale 04/2007 Winterset Limestone 04/2007 Bennison 84
HS5 1 HS4 6 Stark Shale Fontana HS3 Shale HS2 HS1 Canville L.S. 0 5 Figure 29: Measured section for Hogshooter South (Dennis Cyclothem) and New Harmony (Cherryvale Cyclothem) south of Hogshooter, Oklahoma. Portions of the section labelled Bennison 84 were not measured, but are from Bennison (1984). Collected by S. Rosscoe.
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East of Ochelata - N75 36 33.467’ N, 95 55.714’W OCH Ochelata, Oklahoma
2
Covered to Stream Pool
8 7 6 1 Hogshooter 5 Limestone 4 3 2
Undifferentiated Dennis
0 1
Figure 30: Measured section for section East of Ochelata in stream along Northbound US 75 near Ochelata, Oklahoma. Lower section well exposed (similar to Ramona). Upper section (above a small pool in the stream) exposes New Harmony, but was not sampled.
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Zink Ranch 36 15.940’ N, 96 04.052’ W ZR Sperry, Oklahoma 5
Debris Covered
4 16
15
14 Wea Shale 3 13
12
11
10 2
9
8
7
6 Hogshooter 5 Limestone 1 6 4 3
Undifferentiated Dennis Debris Covered 2 1 17 0 5
Figure 31: Measured section for the Zink Ranch, near Sperry Oklahoma. Exposure is a shale bank along a dirt ranch road. The road is gated and locked, permission should be acquired before hand. The overlying sandstone has covered most of the upper section. Collected by S. Rosscoe. 100 Texas Tech University,Steven J. Rosscoe , August 2008
Hogshooter Quarry 36 45.034’ N, 95 48.768’ W HCQ Glenoak, OK 5 10 15 HQS4
Hogshooter Limestone Wea Shale
Block Limestone 4 9 14 HQS3
HQS2
HQS1 South Pit North Pit
3 8 13 HQN2
Nellie Bly Shale
2 7 Hogshooter 12 Limestone
1 6 11
HQS6 Wea Shale 0 HQN1 5 10 HQS5 Figure 32: Measured section for Hogshooter Quarry, operated by Belco. This quarry exposure is split between the North Pit which contains the Hogshooter Limestone and the Southeast Pit that contains the Cherryvale Sequence (Block and Wea or New Harmony). Measured by Peter Holterhoff, Collections by Peter Holterhoff, Jim Barrick, Phil Heckel, and Jeremy Bader. 101 Texas Tech University,Steven J. Rosscoe , August 2008
Bannister Road 38 57.240’ N, 94 33.320’ W BR Kansas City, MO
1 Block Limestone 6 5 4 3 2 1 0
Figure 33: Measured section for Bannister Road. This is a small portion of the outcrop exposed at Bannister Road, and is focused on the Block Limestone, which here is split into a lower and upper unit. Measured and collected by Peter Holterhoff. 102 Texas Tech University,Steven J. Rosscoe , August 2008
Drum Reference Section 37 13.414’ N, 95 34.907’ W DR Independence, KS 5 10 6
Drum Limestone
4 9 5
Wea Shale 4
Block Limestone 3 8 3 13 2
Fontana Shale
2 7 12
Fontana Shale Nellie Bly 1 Shale
1 6 11
Drum Limestone
0 5 10 Figure 34: Measured section for the reference section for the Drum Limestone. This section is on a dirt road east of the intersection of 169 and 160 east of Independence Kansas. A better outcrop is available along the Northbound lanes of 169 south of the reference section. Measured and collected by S. Rosscoe.. 103 Texas Tech University,Steven J. Rosscoe , August 2008
Skiatook Dam 36 20.980’ N, 96 04.998’ W SD Skiatook, OK - Dam Spillway
4
7 3
6 5
2 4
Cement City Limestone
3 2
1
1 Quivira Shale
0
0
Figure 35: Measured section for Skiatook Dam west of Skiatook, Oklahoma, showing only the lower portion of the section for the Dewey Sequence. Remeasured and collected by S. Rosscoe, originally measured by Peter Holterhoff. 104 Texas Tech University,Steven J. Rosscoe , August 2008
KAW Drive 39 06.199’ N, 94 40.961’ W KAW Kansas City, KS 5 10 25
Cement City Limestone
4 24 4 9 14 3
Covered Quivira Interval Shale (Chanute Shale) 2
12 3 8 13
Raytown 2 7 12 Limestone
1
11 10 1 Westerville 6 Cement City 11 Limestone Limestone 9
8 Muncie 7 Creek 6 Shale 5
Paola Limestone 0 5 10
Figure 36: Measured section for KAW Drive. This outcrop is along the westbound lane of KAW Drive, west of Junction 70/635 in Kansas City, KS. Section moves from Iola to Dewey westward along KAW Drive. Measured and collected by S. Rosscoe. 105 Texas Tech University,Steven J. Rosscoe , August 2008
A
B
C D
E F Figure 37: Selected photos from field work localities. A - Jingo Kansas 69 (Hushpuckney Shale, Bethany Falls Limestone, Galesburg Shale). B - Mound Valley Reference Section (Mound Valley Limestone). C - Ramona Railroad Cut (Stark Shale, Winterset Mound). D - Shirk (Lost City Limestone, Stark Shale, Winterset Limestone). E - Ochelata 75 (Hogshooter Limestone).F-KAW Drive (Westerville Limestone, Quivira Shale, Cement City Limestone, Iola Sequence). 106 Texas Tech University, Steven J. Rosscoe, August 2008
APPENDIX B SYSTEMATIC PALEONTOLOGY
Introduction The names presented herein are of species for which the holotype specimens are still available. Where possible, the original holotype specimens from older works (Stauffer and Plummer, 1932; Gunnell, 1933) have been re‐illustrated to aid in comparison. Synonymies presented will represent the most complete list possible, to enable ease in transition for several of the redefined or demoted names. The holotypes of Gunnell (1933) and Ellison (1941) are reposited in the paleontology collections of the University of Missouri and are designated as UM (Gunnell) and UMC (Ellison). Holotypes of Stauffer and Plummer (1932) are reposited in the collections of the Texas Memorial Museum, in Austin Texas, and are designated BEG. Holotypes of Kozitskaya et al. (1978) are reposited in the collections of the Institute of Geological Sciences, Ukraine National Academy of Sciences and have a numerical designation beginning with the number 68. All new specimens published in Rosscoe and Barrick (In Press) are reposited in the paleontology collections of the University of Iowa and are designated as SUI. Other new specimens are reposited in the paleontology collections of Texas Tech University and are designated as TTU.
Systematic Paleontology
Phylum CONODONTA Pander, 1856
Class CONODONTI Branson, 1938 Order OZARKODINIDA Dzik, 1976
Family IDIOGNATHODONTIDAE Harris and Hollingsworth, 1933
Genus IDIOGNATHODUS Gunnell, 1931
Type Species: Idiognathodus claviformis Gunnell, 1931, pl. 29, fig. 21.
Diagnosis: Carminiscaphate P1 element consisting of a flat platform bearing transverse ridges. The ventral platform has both rostral and caudal accessory lobes ornamented by discrete hemispherical nodes.
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Description: The oral surface of the P1 element is highly ornamented. The dorsal platform is crossed by a series of well‐defined transverse ridges of varied spacing and elevation. The transverse ridges may be disrupted by grooves and medial nodes. The ventral platform is characterized by a short medial carina consisting of reduced and fused denticles continuing from the blade, short adcarinal ridges, and accessory lobes of varying development and degree of nodose ornamentation. The blade is typically equal to or slightly longer than the platform.
The P2 element of Idiognathodus has a high cusp with long ventral and dorsal processes. The element is arched orally with a distinctive separation visible between the processes and the denticles upon them. The dorsal process is the longer of the two processes. Process denticles are typically thinner on the ventral process and thicker on the dorsal process. Denticles increase in width on both processes with increasing proximity to the cusp. S and M elements are typical of the Idiognathodontidae.
Discussion: Idiognathodus differs from the genera Swadelina and Streptognathodus by its lack of a well‐developed medial trough on the platform of the P1 element. Idiognathodus also has a shortened medial carina on the P1 element compared to that of Streptognathodus.
IDIOGNATHODUS BILIRATUS (Gunnell, 1933) Figures 43.15‐43.21, 53.26, 53.27. Idiognathodus biliratus Gunnell, 1933, pl. 31, fig. 59. Idiognathodus regulatus Gunnell, 1933, pl. 31, fig. 24. Idiognathodus ? sp. Ellison, 1941, pl. 23, fig. 11. Streptognathodus cancellosus Gunnell, 1933. Lane et al., 1971, p. 401, pl. 1, fig. 33; Ritter et al., 2002, p. 508, figs. 8.13, 8.16, 8.17. Streptognathodus aff. cancellosus (Gunnell, 1933). Forke and Samankassou, 2000, p. 195, pl. 37, figs. 12, 13. Streptognathodus elegantulus Stauffer and Plummer, 1932. Stevens et al., 2001, p. 120, fig. 14.1, 14.4. Streptognathodus neverovensis Goreva and Alekseev, 2006, p. 194, pl. 10, fig. 4. Alekseev and Goreva, 2007, p. 233, pl. 1, fig. 7 Streptognathodus oppletus Ellison, 1941. Ellison, 1941, pl. 22, fig. 14; Lane et al., 1971, p. 401, pl. 1, fig. 35; Merrill and Lyons, 1987, p. 27, fig. 3A.
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Diagnosis: P1 element lacking accessory lobes with an elongate medial carina.
Description: The platform of the P1 element has a very high dorso‐ventral to rostro‐caudal ratio. The margins of the platform are elevated and ornamented with short transverse ridges. The dorsal‐most portion of the platform is crossed by one or two complete transverse ridges which exhibit a weak caudal disruption. The medial carina extends between one‐half and three‐ quarters the length of the platform. Weak denticulation of the medial carina is present in most specimens up to one‐half the length of the platform. The medial carina and platform margins are equal in elevation and the remaining platform area is smooth with some development of dorsal nodes. There are no true accessory lobes. The ventral caudal margin is high in elevation and deflects caudally. The point of caudal deflection is associated with the development of one or two nodes on the inside of the marginal ridge in dextral specimens. In sinistral specimens, the caudal marginal ridge is more pronounced and lacks any accessory ornamentation. The ventral rostral margin is similar in elevation to the remainder of the rostral margin. In dextral specimens, the rostral margin is unornamented. In sinistral specimens, the rostral margin can develop a few internal nodes. The rostral adcarinal ridge is much shorter than the caudal adcarinal ridge and both turn inward, toward the blade of the element.
Discussion: The elongate medial carina and lack of accessory lobes in Idiognathodus biliratus distinguish it from every other species in this study. The only other species lacking accessory lobes is I. cherryvalensis. Idiognathodus cherryvalensis does not have the highly elongate medial carina of I. biliratus. The most similar species in this interval is not from the Midcontinent Basin. There are great similarities between Idiognathodus biliratus and Streptognathodus neverovensis from the Moscow Basin. Investigation of this species in the Midcontinent did not reveal the development of a true trough. The elevated margins and medial carina are equal in elevation, but the lack of ornamentation between the margins and medial carina lead to the interpretation of a trough. Some specimens identified as S. neverovensis in the Moscow Basin are definitely specimens of I. biliratus, while others exhibit variation that distinguishes it from the Midcontinent species. This is the first form in the Midcontinent to lack any lobe and is the most distinctive species in the study. Given the first appearance of the species in deposits likely representative of a global
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highstand event, it is probable that I. biliratus is a species that is related to the Eurasian S. neverovensis, and may have traveled from the Moscow Basin to the Midcontinent Basin during global highstand.
Illustrated Specimens: Figures 43.15 (TTU 08/024), 43.17 (TTU 08/025), and 43.19 (TTU 08/26) from the Dennis Sequence. Figures 43.16 (TTU 08/027), 43.18 (TTU 08/028), 43.20 (TTU 08/029), and 43.21 (TTU 08/030) from the Swope Sequence.
Occurrence: Idiognathodus biliratus first appears in the Hushpuckney Shale of the Swope Sequence. Specimens are recovered from the interval spanning the Swope and Dennis sequences.
IDIOGNATHODUS CANCELLOSUS (Gunnell, 1933) Figures 43.1, 43.2, 43.5, 43.6, 43.8‐43.10, 43.12, 43.13, 53.28, 53.29. Streptognathodus cancellosus Gunnell, 1933, pl. 31, fig. 10; Alekseev and Goreva, 2007, p. 233, pl. 1, figs. 19, 20; Barrick et al., 2004, p. 241, pl. 4, fig. 1 (holotype); Ellison, 1941, pl. 22, figs. 23, 26; Kozitskaya, 1978, pl. XXVI, figs. 11‐14, pl. XXVII, figs. 8, 10; Barrick and Boardman, 1989, p. 185, pl. 1, figs. 11, 18; Barrick and Walsh, 1999, p. 155, fig. 7.3 (holotype); Stevens et al., 2001, p. 120, fig. 13.10; Zhihao and Yuping, 2003, p. 395, pl. 4, fig. 20. Idiognathodus clavatulus (Gunnell, 1933). Barrick and Boardman, 1989, p. 185, pl. 1, fig. 10; Zhihao and Yuping, 2003, p. 395, pl. 4, fig. 8. Streptognathodus oppletus Ellison, 1941. Zhihao and Yuping, 2003, p. 393, pl. 3, fig. 20.
Diagnosis: P1 element with reduced rostral and caudal lobes with medial nodosity.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio and is split symmetrically by a row of medial nodes. The dorsal platform is ornamented at the margins with remnant transverse ridges. Medial nodes range from small discrete nodes to small ridges in larger specimens. The dorsal margin of the platform is subrounded to rounded. The caudal accessory lobe is reduced and ornamented with poorly defined to fused nodes. The rostral accessory lobe is reduced, extending about one‐third the length of the platform and
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ornamented by a single row of poorly defined nodes and a few nodes on the caudal side of the rostral lobe where it is most expanded in the rostro‐caudal direction. The caudal adcarinal ridge is well‐developed and forms a high elevation ridge that merges with the ornamentation of the caudal lobe. The rostral adcarinal ridge is less pronounced than the caudal adcarinal ridge and extends onto the platform, where it forms the margin separating the central platform from the rostral lobe. The adcarinal ridges terminate dorsal of the termination of the medial carina. The medial carina terminates near the ventral margin of the platform and does not exceed one‐quarter the length of the platform.
Discussion: Idiognathodus cancellosus can be distinguished from other similar species by its reduced lobes and medial nodosity. The species I. biliratus lacks a rostral lobe and has an elongate medial carina. Idiognathodus aff. cancellosus has an inset rostral lobe and a normal caudal lobe. Idiognathodus species 1 has a robust normal caudal lobe and an elongate rostral lobe with chaotic to nodose platform ornamentation. Idiognathodus clavatulus has an elongate rostral lobe, but has a medial groove and normal caudal lobe. Small specimens of I. cancellosus have an elongate medial carina that extends half the length of the platform, but this feature is lost in specimens of moderate size. Smooth platforms develop along with the medial nodosity in moderately‐sized specimens, but more nodose platforms are common along with the medial nodosity in the largest specimens. As originally defined by Ellison (1941) Idiognathodus cancellosus belonged to the genus Streptognathodus. Idiognathodus cancellosus does not have a troughed platform, and is now placed in the genus Idiognathodus. The medial groove and medial carina, along with the slightly elevated platform margins, give the superficial appearance of a trough.
Type Specimen: Figure 43.12 (UM 491‐2) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figures 43.1 (TTU 08/011), 43. 5 (TTU 08/012), 43.6 (TTU 08/013), and 43.13 (TTU 08/022) from the Dennis Sequence. Figures 43.2 (TTU 08/014), 43.8 (TTU 08/018), 43.9 (TTU 08/019), and 43.10 (TTU 08/020) from the Swope Sequence.
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Occurrence: The first appearance of Idiognathodus cancellosus is in the Hushpuckney Shale of the Swope Sequence. Specimens of I. cancellosus are recovered from the interval spanning the Swope to Dennis sequences.
IDIOGNATHODUS AFF. CANCELLOSUS (Gunnell, 1933) Figures 43.3, 43.4, 43.7, 43.11, 43.14.
Diagnosis: P1 element with inset rostral lobe, normal to reduced caudal lobe, and well developed medial nodosity.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio and is split symmetrically by a row of medial nodes. Transverse ridges ornament the margins of the dorsal platform but are disrupted by medial nodosity along the dorso‐ventral axis of the element. Medial nodosity is best developed in dextral elements. Sinistral elements often have a strong caudal eccentric groove that divides the platform asymmetrically and have a weakly developed medial nodosity. The dorsal platform is subrounded. The normal caudal accessory lobe protrudes from the margin of the element but is not robustly ornamented. Ornamentation of the caudal lobe is typically one or two large nodes that exhibit partial fusing. The rostral lobe is inset with only one or two nodes present on the lobe at an inflection point in the rostral margin of the element. In dextral specimens, the lobe does expand ventrally and caudally from the inset ornamentation as a narrow ghost lobe. The node or nodes of the rostral lobe are discrete and well defined. The caudal adcarinal ridge is longest and high in elevation when compared to the rest of the platform. The caudal adcarinal ridge extends onto the platform forming the ventral portions of the margin that separate the central platform from the caudal accessory lobe. The rostral adcarinal ridge is straight and joins with the rostral margin of the platform at an inflection point that is the focus of the inset ornamentation of the rostral accessory lobe. The medial carina is short but may appear longer due to the dribbling nature of the medial nodosity in some specimens.
Discussion: The inset rostral and normal caudal lobes of Idiognathodus aff. cancellosus distinguish it from other similar species. Idiognathodus biliratus lacks accessory lobes, while the
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caudal lobe in I. species 1 is robust and the platform only shows a caudal eccentric groove. While the ghost‐like projections of the inset lobe of I. aff cancellosus give it the appearance of the reduced elongate rostral lobe of I. clavatulus, the rostral lobe in I. clavatulus is ornamented along its entire length and the platform bears only medial groove. Slight differences between dextral and sinistral specimens of I. aff. cancellosus demonstrate a weak asymmetry of the paired P1 elements in this species.
Illustrated Specimens: Figures 43.3 (TTU 08/015), 43.4 (TTU 08/016), 43.7 (TTU 08/017), and 43.11 (TTU 08/021) from the Swope Sequence. Figure 43.14 (TTU 08/023) from the Dennis Sequence.
Occurrence: Idiognathodus aff. cancellosus first appears and is most common in the Hushpuckney Shale of the Swope Sequence. Specimens of I. aff. cancellosus are recovered from the interval spanning the Swope to Dennis sequences.
IDIOGNATHODUS CHERRYVALENSIS Gunnell, 1933 Figures 45.1‐45.4, 45.6, 48.1‐ 48.4, 48.8‐ 48.11, 48.14, 48.17, 53.18. Idiognathodus cherryvalensis Gunnell, 1933, pl. 32, fig. 5.
Diagnosis: P1 element with no rostral or caudal accessory lobes and an oral surface ornamented with complete transverse ridges from the dorsal tip to ventral margin of the platform.
Description: The platform of the P1 element has a very high dorso‐ventral to rostro‐caudal ratio due to the lack of accessory lobes on either side of the platform. The dorsal platform is ornamented with complete transverse ridges that exhibit a weak medial disruption or deflection near the dorsal termination of the medial carina. The dorsal platform margin ranges from pointed to round. The caudal margin of the element is the most pronounced with a straight margin that is slightly higher in elevation than the remainder of the element. The rostral margin of the element is equal in elevation with the platform. The ventral portion of the platform is ornamented with transverse ridges on either side of the medial carina to the ventral margin of the platform.
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Both rostral and caudal adcarinal ridges appear to be the ventral continuation of the rostral and caudal margins of the element. Ornamentation of the adcarinal ridges is more ridge‐ like than carinate or nodose. The caudal adcarinal ridge is commonly the most carinate in nature. The medial carina is elongate and extends between one‐quarter and one‐half the length of the platform in the dorsal direction. The medial carina is most commonly expressed as a solid ridge with some low relief denticulation evident in smaller specimens.
Discussion: The only species other than Idiognathodus cherryvalensis to lack both rostral and caudal lobes is I. biliratus. The two species are easily distinguishable by the ornamentation of the dorsal platform and length of the medial carina. Idiognathodus cherryvalensis has a platform ornamented with continuous transverse ridges, while I. biliratus typically lacks ornamentation except for a few randomly located nodes ventrally and two or three transverse ridges that cross at the very dorsal portion of the platform. In addition, I. biliratus has an elongate medial carina that extends much further (beyond one‐half the length of the platform) than the elongate medial carina of I. cherryvalensis. The younger I. cherryvalensis and older I. biliratus only co‐ occur in the Dennis Sequence. All other specimens in this study have either a caudal or both caudal and rostral lobes that distinguish them from I. cherryvalensis.
Type Specimen: Figure 48.11 (UM 505‐4) the holotype specimen of Gunnell (1933) from the Wea Shale of the Cherryvale Sequence.
Illustrated Specimens: Figures 45.1 (TTU 08/045), 45.2 (TTU 08/046), 45.3 (TTU 08/047), 45.4 (TTU 08/048), 45.6 (TTU 08/049) from the Dennis Sequence. Figures 48.1 (TTU 08/112), 48.2 (TTU 08/113), 48.3 (TTU 08/114), 48.4 (TTU 08/115), 48.10 (TTU 08/121), 48.14 (TTU 08/124), and 48.17 (127) from the Dewey Sequence. Figures 48.8 (TTU 08/119) and 48.9 (TTU 08/120) from the Cherryvale Sequence.
Occurrence: Idiognathodus cherryvalensis first appears in the lower non‐black portion of the Stark Shale above the Canville Limestone. Specimens of I. cherryvalensis are recovered from the interval spanning the Dennis to Dewey sequences.
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IDIOGNATHODUS CLAVATULUS (Gunnell, 1933) Figures 46.1‐46.8, 53.15. Streptognathodus clavatulus Gunnell, 1933, pl. 31, fig. 9; Barrick and Walsh, 1999, p. 153, fig. 5.1 (holotype). Idiognathodus clavatulus (Gunnell, 1933). Barrick and Walsh, 2004, p. 241, pl. 4, fig. 12 (holotype).
Diagnosis: P1 element with a reduced elongate rostral lobe and an oral surface ornamented with closely‐spaced transverse ridges bisected by a medial groove.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio and is asymmetrically split by a medial groove. The platform is ornamented with closely‐spaced transverse ridges that deflect ventrally along the medial groove. The dorsal margin is subrounded to rounded in shape. The robust, normal caudal lobe is ornamented with discrete nodes. Nodes are less discrete in larger specimens. The reduced elongate rostral lobe is ornamented with a single row of discrete hemispherical nodes along its entire length. The rostral lobe extends between one‐half and three‐quarters the length of the platform. The caudal adcarinal ridge is the most pronounced and flares outward at the ventral margin of the platform. The caudal margin of the platform is merged with the caudal adcarinal ridge and separates the caudal lobe from the central platform. The rostral adcarinal ridge is shorter than the caudal and merges with the rostral margin of the central platform. The medial carina is short and is followed by one to three closely spaced nodes at the dorsal termination. In larger specimens these nodes become fused with the medial carina.
Discussion: Idiognathodus clavatulus is recognized by its medial groove and reduced elongate rostral lobe. It is part of a lineage that has a variety of intermediate forms, but can be readily distinguished from both its ancestors and descendents using the reduced elongate rostral lobe. Idiognathodus species 1 has an elongate rostral lobe, I. aff. cancellosus has an inset rostral lobe, and I. cancellosus has a reduced rostral lobe. In addition, the medial groove in I. clavatulus is not found in specimens of I. aff cancellosus and I. cancellosus, which have a caudal eccentric groove and medial nodosity respectively.
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Type Specimen: Figure 46.4 (UM 493‐2) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figures 46.1 (TTU 08/067), 46.2 (TTU 08/068), 46.3 (TTU 08/069), 4.5 (TTU 08/070), 46.6 (TTU 08/071), 46.7 (TTU 08/072), and 46.8 (TTU 08/073) from the Swope Sequence.
Occurrence: Idiognathodus clavatulus first appears in the Hushpuckney Shale of the Swope Sequence. Specimens of I. clavatulus are recovered from only the Swope Sequence.
IDIOGNATHODUS CONFRAGUS Gunnell, 1933 Figures 45.5, 45.7‐45.15, 53.17. Idiognathodus confragus Gunnell, 1933, pl. 31, fig. 43; Barrick and Walsh, 1999, p. 155, fig. 7.4 (holotype); Stevens et al., 2001, p. 120, figs. 14.3, 14.8. Idiognathodus binodosus Gunnell, 1933, pl. 31, fig. 35. Idiognathodus carniferus Gunnell, 1933, pl. 31, fig. 52. Idiognathodus gemmiformis Gunnell, 1933, pl. 31, fig. 44. Idiognathodus species B, Barrick and Boardman, 1989, p. 187, pl. 2, fig. 8. Streptognathodus confragus (Gunnell, 1933). Barrick and Boardman, 1989, p. 185, pl. 1, fig. 4; Ritter et al., 2002, p. 510, figs. 9.17‐9.19; Barrick et al., 2004, p. 241, pl. 4, fig. 2. Streptognathodus oppletus Ellison, 1941. Ellison, 1941, pl. 22, fig. 16; Barrick and Boardman, 1989, p. 187, pl. 2, figs. 2, 4.
Diagnosis: P1 element with a robust reduced rostral lobe and a ventrally shifted robust reduced caudal lobe with an elongate medial carina.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The ventral portion of the element is expanded along the rostro‐caudal axis. The platform is ornamented with complete transverse ridges that begin at the dorsal termination of the medial carina and both of the accessory lobes. The dorsal tip of the platform is pointed. The accessory lobes are shifted and appear to expand in the ventral rather than the dorsal direction. The caudal accessory lobe is the most shifted in the ventral direction. The caudal lobe is reduced in
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shape but robust in ornamentation (especially in the larger specimens). The rostral lobe is reduced in shape with normal ornamentation and protrudes slightly at the ventral margin of the element. The adcarinal ridges do not extend beyond the ventral margins of their respective accessory lobes. The caudal adcarinal ridge is the longest and forms the division between the medial carina and the caudal accessory lobe. The rostral adcarinal ridge forms the margin separating the medial carina and the rostral lobe. Both adcarinal ridges are the same elevation as the ornamentation on the accessory lobes and the medial carina. The medial carina is elongate and extends between one‐quarter and one‐half the length of the platform.
Discussion: Idiognathodus confragus is one of two species in the study interval that exhibits the ventral shift of the caudal accessory lobe. The other species, I. symmetricus, does not co‐occur with I. confragus. Idiognathodus symmetricus does not have the robust development of the caudal lobe and shows a moderately restricted rostral lobe, as opposed to the robust reduced caudal and reduced rostral lobes of I. confragus. Idiognathodus folium and I. lobatus are closely related species to I. confragus. The elongate medial carina of I. confragus distinguishes it from both I. folium and I. lobatus.
Type Specimen: Figure 45.14 (UM 498‐1) the holotype specimen of Gunnell (1933) from the Winterset Limestone of the Dennis Sequence.
Illustrated Specimens: Figures 45.5 (TTU 08/050), 45.7 (TTU 08/051), 45.8 (TTU 08/052), 45.10 (TTU 08/054), 45.11 (TTU 08/055), and 45.12 (TTU 08/056) from the Swope Sequence. Figures 45.9 (TTU 08/053), 45.13 (TTU 08/057), and 45.15 (TTU 08/058) from the Dennis Sequence.
Occurrence: Idiognathodus confragus first appears in the Hushpuckney Shale of the Swope Sequence. Specimens of I. confragus are recovered from the interval spanning the Swope to Dennis sequences.
IDIOGNATHODUS CORRUGATUS Gunnell, 1933 Figures 46.13‐46.26, 53.5. Idiognathodus corrugatus Gunnell, 1933, pl. 32, fig. 6.
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Idiognathodus delicatus Gunnell, 1933. Ellison, 1941, pl. 23, figs. 1, 8. Idiognathodus lanceolatus Gunnell, 1933, pl. 31, fig. 31. Idiognathodus liratus Gunnell, 1933, pl. 31, fig. 27. Streptognathodus confragus Gunnell, 1933. Ritter et al., 2002, p. 510, fig. 9.14. Streptognathodus excelsus Stauffer and Plummer, 1932. Ritter et al., 2003, fig. 19.15.
Diagnosis: P1 element that is missing a rostral lobe, has a reduced caudal lobe and has an elongate medial carina up to one‐quarter the length of the platform.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio and is ornamented by complete transverse ridges. A few specimens exhibit a caudal eccentric groove. All specimens exhibit a ventral deflection of the transverse ridges dorsal of the medial carina. The dorsal margin of the platform is most commonly pointed but can be found as subrounded and rounded as well. The caudal lobe is reduced and ornamented with a fused ridge rather than discrete nodes. The rostral lobe is absent but appears as a ghost lobe in smaller specimens. The adcarinal ridges form parallel, linear features on the ventral surface of the platform. The caudal adcarinal ridge merges with the central platform margin to form the division between the central platform and the caudal accessory lobe. The rostral adcarinal ridge is shorter in the ventral direction and merges with the rostral margin of the element. The medial carina is elongate, typically extending around one‐quarter the length of the platform. The medial carina is longest in small specimens.
Discussion: Idiognathodus corrugatus and I. multinodosus are most closely related and both lack a rostral accessory lobe. Idiognathodus multinodosus is differentiated from I. corrugatus by its ridge‐like medial nodosity formed by two distinctive marginal grooves rather than complete transverse ridges. Specimens of I. corrugatus recovered from the Swope and Mound Valley sequences commonly have an eccentric groove
Type Specimen: Figure 46.14 (UM 491‐2) the holotype specimen of Gunnell (1933) from the Wea Shale of the Cherryvale Sequence.
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Illustrated Specimens: Figure 46.13 (TTU 08/078) from the Hogshooter Sequence. Figure 46.15 (TTU 08/079) from the Cherryvale Sequence. Figure 46.16 (TTU 08/080) from the Dewey Sequence. Figures 46.17 (TTU 08/081), 46.23 (TTU 08/087), and 46.24 (TTU 08/088) from the Swope Sequence. Figures 46.18 (TTU 08/082), 46.19 (TTU 08/083), 46.25 (TTU 08/089), and 46.26 (TTU 08/090) from the Mound Valley Sequence. Figures 46.20 (TTU 08/084), 46.21 (TTU 08/085), and 46.22 (TTU 08/086) from the Dennis Sequence.
Occurrence: Idiognathodus corrugatus first appears in the Hushpuckney Shale of the Swope Sequence. Specimens of I. corrugatus are recovered from the interval spanning the Swope to the Dewey sequences.
IDIOGNATHODUS ECCENTRICUS (Ellison, 1941) Figures 42.3, 42.5, 42.9‐42.11, 42.14, 42.15, 53.10. Streptognathodus eccentricus Ellison, 1941, pl. 22, fig. 24; Barrick and Walsh, 1999, p. 157, fig. 84 (holotype). Idiognathodus eccentricus (Ellison, 1941). Barrick and Boardman, 1989, p. 185, pl. 1, figs. 8, 13, 15; Stevens et al., 2001, p. 120, fig. 14.17; Ritter et al., 2002, p. 508, fig 8.19; Barrick et al., 2004, p. 241, pl. 4, fig. 9 (holotype); Mendez, 2006, p. 250, fig. 5.14; Rosscoe and Barrick, In Press, pl. 5, figs. 8‐17, pl. 6, figs. 7a‐7d.
Diagnosis: P1 element with a restricted rostral lobe and a well defined caudal eccentric groove that runs from the ventral margin to the dorsal tip of the element.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The platform is split asymmetrically by an eccentric groove extending from the caudal adcarinal groove to the dorsal tip of the platform. The caudal portion of the dorsal platform is ornamented with coarse transverse ridges in a generally horizontal orientation. The rostral portion of the dorsal platform is ornamented with transverse ridges that are oriented in an angle from dorsal on the platform margin to ventral at the eccentric groove where they align with the caudal transverse ridges. The dorsal margin of the platform is pointed in shape. The caudal lobe protrudes from the platform and is dorso‐ventrally elongate in shape. Fused nodes form a ridge at the margin of the platform, and internal ornamentation of the lobes is limited to
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a few semi‐fused to fused nodes. The restricted rostral accessory lobe is confined to the ventral quarter of the platform by the first complete transverse ridge. Well‐spaced, discrete nodes ornament the rostral lobe. The caudal adcarinal ridge is the longest and forms the inner margin of the caudal lobe. The margin formed by the adcarinal ridge is, at first, nodose and then becomes a low ridge until merging with the margin of the platform. The rostral adcarinal ridge terminates with the medial carina or is replaced by rostral lobe ornamentation mimicking the orientation of the adcarinal ridge. The medial carina is restricted to the upper quarter of the platform, truncating ventrally of the first complete transverse ridge.
Discussion: Idiognathodus eccentricus can be distinguished from other early Missourian species by its unique eccentric groove. Idiognathodus species 1 has an expanded rostral lobe. Idiognathodus sulciferus may develop a weak and incomplete eccentric groove in juvenile specimens, but never retains the groove in adult specimens. Idiognathodus turbatus has an expanded rostral lobe that protrudes from the platform margin, which distinguishes it from I. eccentricus even though it can develop a weak eccentric to marginal groove.
Type specimen: Figure 42.15 (UMC 560‐1) the holotype specimen of Ellison (1941) from the Hushpuckney Shale of the Swope Sequence.
Illustrated specimens: Figures 42.3 (TTU 08/007) and 42.10 (TTU 08/010) from the Swope Sequence. Figure 42.5 (SUI 108283) from the Hertha Sequence. Figures 42.9 (SUI 108284), 42.11 (SUI 108285), and 42.14 (SUI 108287) from the Shale Hill Sequence.
Occurrence: The first appearance of Idiognathodus eccentricus is in Exline Limestone of the Shale Hill Sequence. Specimens of I. eccentricus are recovered from the interval spanning the Shale Hill to Swope sequences.
IDIOGNATHODUS EXPANSUS Stauffer and Plummer, 1932 Figures 38.1‐38.21, 53.1. Idiognathodus expansus Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 1, 3; Barrick and Boardman, 1989, p. 150, fig. 5.4; Barrick and Walsh, 1999, p. 150, figs. 5.2, 5.3 (cotypes);
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Stevens et al., 2001, p. 118, figs. 13.16, 13.17; Ritter et al., 2002 p. 506, figs. 7.3, 7.7, 7.12, 7.14, 7.16, p. 508, fig. 8.9, 8.22, 8.23; Barrick et al., 2004, p. 239, pl. 3, fig. 4; Lambert et al., 2003, p. 155, pl. 1, fig. 5; Rosscoe and Barrick, In Press, pl. 1, figs. 1‐21, pl. 6, figs. 1a‐1d. Idiognathodus antiquus Stauffer and Plummer, 1932, p. 197, pl. IV, fig. 17; Barrick and Walsh, 1999, p. 150, fig. 5.4 (holotype). Idiognathodus species 1 of Swade, 1985, p. 55, fig. 18.10 (only).
Diagnosis: P1 element with fine transverse ridges and a restricted rostral lobe extending only as far as the ventral quarter of the platform by the ventral‐most transverse ridge.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio. Transverse ridges on the platform are closely‐spaced and exhibit a thin low‐elevation appearance. The caudal lobe is the most developed. The surface of the lobe is covered with discrete hemispherical nodes oriented along the curvature of the caudal element margin. Development of the rostral lobe in the dorsal direction is restricted by the ventral‐most transverse ridge and limits its size to the ventral quarter of the platform. The rostral lobe is ornamented with a few small nodes. The medial carina and adcarinal ridges extend one‐quarter to one‐third the length of the platform in the dorsal direction and are terminated by the ventral transverse ridge. In the ventral direction the adcarinal ridges extend to the first denticles of the free blade. The rostral adcarinal ridge is shorter and less flaring than the caudal adcarinal ridge. In most cases the adcarinal ridges and the medial carina have a nodose appearance and do not stand taller than the surrounding ornamentation on the platform.
Discussion: Idiognathodus expansus has a restricted and underdeveloped rostral lobe that can be differentiated from I. swadei, I. turbatus, I. vorax, I. species 1, and I. sulciferus. Idiognathodus expansus has adcarinal ridges that are much shorter, extending just beyond the ventral platform margin, than adcarinal ridges in the other Missourian species of Idiognathodus. The fine, closely‐ spaced transverse ridges of the platform can differentiate I. expansus from the coarser, widely‐ spaced ridges of I. sulciferus. Idiognathodus expansus can also be differentiated from I. eccentricus by the eccentric groove present in I. eccentricus.
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Juvenile forms of Idiognathodus expansus show only a caudal accessory lobe. The medial carina in juvenile specimens will commonly extend no further than one half the length of the platform and are truncated by the well defined first ventral transverse ridge. Transverse ridges are clearly defined but are fewer in number. Some juvenile forms show a slight marginal groove that is lost with development. Specimens recovered from lithotypes indicative of deeper waters exhibit several forms of ecological variation. The dorsal margin of the platform tends to be more rounded, has a slight marginal groove in larger specimens, and a wavy deflection of transverse ridges can be developed in line with the caudal adcarinal groove. These variations are relatively rare and reflect ecological rather than functionally significant morphological changes.
Type specimens: Figure 38.8 (BEG 19163) cotype of Stauffer and Plummer (1932) from the East Mountain Formation, equivalent to the Lost Branch Sequence. Figure 38.21 (BEG 20928) cotype of Stauffer and Plummer (1932) and lectotype of Barrick and Walsh (1999) from the East Mountain Formation, equivalent to the Lost Branch Sequence.
Illustrated specimens: Figures 38.1 (SUI 108209) and 38.2 (SUI 108210) juvenile specimens from the Lost Branch Sequence. Figures 38.3 (SUI 108211), 38.4 (SUI 108213), 38.5 (SUI 108216), 38.6 (SUI 108227), 38.7 (SUI 108226), 38.9 (SUI 108220), 38.10 (SUI 108214), 38.11 (SUI 108215), 38.12 (SUI 108224), 38.13 (SUI 108221), 38.14 (SUI 108217), 38.15 (SUI 108212), 38.16 (SUI 108223), 38.17 (SUI 108225), 38.18 (SUI 108219), 38.19 (SUI 108222), and 38.20 (SUI 108218) adult specimens from Lost Branch Sequence.
Occurrence: The first appearance of Idiognathodus expansus remains undetermined and will require additional study of Desmoinesian idiognathodids in the Midcontinent. The last appearance of I. expansus is in the Lost Branch Sequence. Its extinction occurs in the same sequence as the extinction of the conodont genera Swadelina and Neognathodus in the Midcontinent Basin.
IDIOGNATHODUS FOLIUM Gunnell, 1933 Figures 44.1‐44.8, 44.13, 49.1‐49.3, 53.19. Idiognathodus folium Gunnell, 1933, pl. 31, fig. 33. Idiognathodus cicatricosis Gunnell, 1933, pl. 31, fig. 34.
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Idiognathodus semipapulatus Gunnell, 1933, pl. 31, fig. 29. Idiognathodus spathodus Gunnell, 1933, pl. 31, fig. 28 Idiognathodus sulciferus Gunnell, 1933. Ritter et al., 2002, p. 508, figs. 8.8, 8.21.
Diagnosis: P1 element with a continuous, non‐robust rostral lobe and normal caudal lobe.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio, due to the expansion of the platform by the development of the two accessory lobes. The dorsal platform is ornamented with complete transverse ridges that are parallel to the rostro‐caudal axis of the element. There is no disruption or deflection of the transverse ridges. The dorsal tip of the platform is subrounded. The caudal accessory lobe is normal with well developed ornamentation of discrete hemispherical nodes to weakly fused node rows. The rostral accessory lobe is expanded in the dorso‐ventral direction, but does not protrude, and forms a continuous rostral margin for the element. Ornamentation of the rostral lobe is that of discrete nodes. Both the rostral and caudal accessory lobes are the same elevation as the central platform of the element. Both the rostral and caudal adcarinal ridges are short and terminate at roughly the same point along the dorsal portion of the blade. The adcarinal ridges are ornamented with short rostro‐caudally oriented ridges beyond the ventral margin of the platform, but become node‐ like when expressed on the platform. The rostral adcarinal ridge forms the margin separating the rostral accessory lobe and the central platform while the caudal adcarinal ridge forms a less distinctive separation between the caudal lobe and the central platform. The medial carina extends only up to one‐quarter the length of the platform.
Discussion: Idiognathodus folium is closely related to I. lobatus, I. confragus, I. swadei, I. turbatus, I. siculus, and I. kansensis. The expanded rostral lobe of I. lobatus forms as a narrow dorsal expansion of a moderately restricted rostral lobe rather than the true expanded lobe of I. folium. The elongate medial carina and ventral shift of accessory lobes in I. confragus distinguishes it from I. folium. Idiognathodus swadei, I. turbatus and I. siculus differ from I. folium in that they have distinctively protruding rostral lobes. Idiognathodus turbatus also exhibits disrupted transverse ridges as opposed to the continuous transverse ridges of I. folium. The species I. siculus is only ornamented along the ventral half of the rostral lobe, not the entire
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length of the rostral lobe as seen in I. folium. The rostral lobe of I. kansensis is more protruding, more robust, and more distinctively separated from the central platform than the rostral lobe of I. folium.
Type Specimen: Figure 44.2 (UM 496‐1) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figures 44.1 (TTU 08/031) and 44.6 (TTU 08/035) from the Hertha Sequence. Figures 44.3 (TTU 08/032), 44.4 (TTU 08/033), 44.5 (TTU 08/034), 44.7 (TTU 08/036), 44.8 (TTU 08/037), and 44.13 (TTU 08/041) from the Swope Sequence. Figures 49.1 (TTU 08/133), 49.2 (TTU 08/134), and 49.3 (TTU 08/135) from the Dennis Sequence.
Occurrence: The first appearance of Idiognathodus folium is in the Mound City Shale of the Hertha Sequence. Specimens are recovered from the interval spanning the Hertha to Dennis sequences.
IDIOGNATHODUS FUSIFORMIS Gunnell, 1933 Figures 40.12‐40.14, 47.8‐47.19, 53.9. Idiognathodus fusiformis Gunnell, 1933, pl. 31, fig. 49. Idiognathodus erodus Gunnell, 1933, pl. 31, fig. 48. Idiognathodus magnificus Stauffer and Plummer, 1932, p. 197, pl. IV, fig. 20; Barrick and Walsh, 1999, p. 150, fig. 3.4 (re‐illustrated); Stevens et al., 2001, p. 120, fig. 13.9, 13.15, 13.16; Ritter et al., 2002, p. 510, figs. 9.20‐9.23; Barrick et al., 2004, p. 241, pl. 4, fig. 7 (re‐ illustrated). Idiognathodus strigillatus Gunnell, 1933, pl. 31, fig. 37, pl. 32, fig. 8. Idiognathodus sulciferus fusiformis Rosscoe and Barrick, In Press, pl. 3, figs. 2‐6, 11. Idiognathodus vadosus Gunnell, 1933, pl. 31, fig. 45. Idiognathodus wintersetensis Gunnell, 1933, pl. 31, fig. 36.
Diagnosis: P1 element with a protruding and robust restricted to moderately restricted rostral lobe and normal caudal lobe.
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Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio due to its robust accessory lobes. The dorsal platform is ornamented with complete transverse ridges. In rare cases, disruption of transverse ridges on the caudal side of the platform is recognized. The dorsal margin of the platform is subrounded. The caudal lobe is robust and ornamented with discrete hemispherical nodes. In some cases, these nodes may be partially fused or even ridge‐like. The rostral lobe is on the borderline between restricted and moderately restricted. In most cases, the rostral lobe is expanded beyond the first transverse ridge, but by a single node. This is the shortest dorsal expansion possible under the classification of moderately restricted rostral lobes. In small‐ and intermediate‐sized specimens the rostral margin of the rostral lobe protrudes ventrally but joins with the dorsal platform as a continuous margin. In larger specimens it is common to see an inflection point where the rostral lobe has become so protruding that it no longer forms a continuous rostral margin to the platform. The adcarinal ridges are very short. Both the rostral and caudal adcarinal ridges terminate at the same position along the dorsal portion of the blade. The caudal adcarinal ridge merges with the nodose margin separating the caudal lobe from the transverse ridges of the central platform. The rostral adcarinal ridge truncates at the first transverse ridge. The remainder of the margin between the rostral lobe and the central platform is marked by the rostral truncation of the transverse ridges. The medial carina is short and is truncated by the first transverse ridge.
Discussion: Idiognathodus fusiformis is the only species in the study interval that has a moderately restricted rostral lobe by expanding dorsally by a single node beyond the first transverse ridge. It is also the only species to develop a highly protruding rostral lobe in large specimens. Idiognathodus sulciferus and I. harkeyi both have true moderately restricted rostral lobes where the lobe structure continues beyond the first one or two transverse ridges. The rostral lobe of I. sulciferus is not robust but rather narrow and continuous. Idiognathodus harkeyi forms a very pronounced triangular platform that is not expressed in I. fusiformis. Idiognathodus fusiformis co‐occurs with I. magnificus, I. species 3, and I. species 4. Idiognathodus magnificus has a well developed robust moderately restricted rostral lobe that expands two transverse ridges dorsally and has a lower dorso‐ventral to rostro‐caudal ratio than I. fusiformis. Idiognathodus species 3 has an inset rostral lobe and I. species 4 has an inset rostral
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lobe with a low dorso‐ventral to rostro caudal ratio. Because of their inset rostral lobes I. species 3 and I. species 4 cannot compare with the moderately restricted rostral lobe of I. fusiformis. Rosscoe and Barrick (In Press) designated Idiognathodus fusiformis as the subspecies I. sulciferus fusiformis. Since the work was submitted for publication, it has been recognized that this unique form is present as a distinctive form in a sufficient number of sequences and is abundant enough to constitute a species.
Type Specimen: Figure 40.14 (UM 499‐2) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figure 40.12 (SUI 108248) from the Hertha Sequence. Figure 40.13 (SUI 108250) from the Shale Hill Sequence. Figures 47.7 (TTU 08/098), 47.8 (TTU 08/099), 47.9 (TTU 08/100), 47.10 (TTU 08/103), 47.13 (TTU 08/107), 47.14 (TTU 08/106), 47.16 (TTU 08/109), 47.17 (TTU 08/104), and 47.19 (TTU08/111) from the Dennis Sequence. Figures 47.11 (TTU 08/101) and 47.12 (TTU 08/102) from the Mound Valley Sequence. Figures 47.18 (TTU 08/110) from the Cherryvale Sequence. Figure 47.15 (TTU 08/161) from the Dewey Sequence.
Occurrence: Idiognathodus fusiformis first appears in the Exline Limestone of the Shale Hill Sequence. Specimens are recovered from the interval spanning the Shale Hill to Dewey sequences.
IDIOGNATHODUS HARKEYI Gunnell, 1933 Figures 40.1, 40.6‐40.8, 53.8. Idiognathodus harkeyi Gunnell, 1933, pl. 31, fig. 11; Barrick and Walsh, 1999, p. 153, fig. 5.3 (holotype). Idiognathodus cuneiformis Gunnell, 1933, pl. 31, fig. 8; Barrick and Walsh, 1999, p. 153, fig. 5.2 (holotype). Idiognathodus jugosus Gunnell, 1933, pl. 31, fig. 13; Barrick and Walsh, 1999, p. 153, fig. 7.2 (holotype). Idiognathodus sulciferus harkeyi Rosscoe and Barrick, In Press, pl. 3, figs. 1, 7‐10.
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Diagnosis: P1 element with a robust moderately restricted rostral lobe and protruding normal caudal lobe.
Description: The platform of the P1 element has a very high dorso‐ventral to rostro‐caudal ratio and forms a triangular, almost arrow‐head shape. The dorsal platform is ornamented with complete transverse ridges that are disrupted on the caudal side of the platform. Ventral deflection of transverse ridges and even a primitive eccentric groove are common expressions of this disruption. The dorsal margin of the platform is pointed in all specimens. The caudal lobe is normal in shape, but reduced in overall size from the normal lobes of similar‐sized species. The caudal lobe protrudes at a very sharp angle along its dorsal margin, appearing as almost ninety degrees is some specimens. The rostral lobe is moderately restricted with only one or two nodes forming the dorsal‐most expansion of the lobe beyond the first transverse ridge. The adcarinal ridges are short in their extent beyond the ventral margin of the platform. The caudal adcarinal ridge is longer than the rostral adcarinal ridge. The caudal adcarinal ridge intersects the ventral margin of the caudal accessory lobe. The ventral margin and the margin separating the caudal lobe from the central platform are the most distinctive features of the caudal accessory lobe. The rostral adcarinal ridge forms the pronounced ventral margin of the rostral accessory lobe. The medial carina is short and is truncated by the ventral‐most transverse ridge.
Discussion: The most closely related species to Idiognathodus harkeyi are I. sulciferus and I. fusiformis. Idiognathodus sulciferus and I. fusiformis both have moderately expanded lobes, but the robust and protruding nature of these lobes serves to distinguish them from I. harkeyi. The rostral lobe of I. sulciferus is not robust, but rather narrow and continuous, while the rostral lobe of I. harkeyi is robust and protruding. The rostral lobe of I. fusiformis protrudes to a greater extent and is more robust in nature than the rostral lobe of I. harkeyi. While moderately restricted, the rostral lobe of I. fusiformis is only extended beyond the first transverse ridge by a single node.
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Rosscoe and Barrick (In Press) designated Idiognathodus harkeyi as the subspecies I. sulciferus harkeyi. Since the work was submitted for publication, it has been recognized that this unique form is present as a distinctive form in a sufficient number of sequences and is abundant enough to constitute a species.
Type Specimen: Figure 40.7 (UM 491‐3) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figure 40.1 (SUI 108252) from the Hepler Sequence. Figure 40.6 (SUI 108253) from the Shale Hill Sequence. Figure 40.8 (SUI 108253) from the Hertha Sequence.
Occurrence: Idiognathodus harkeyi first appears in the South Mound Shale of the Hepler Sequence. Specimens are recovered from the interval spanning the Hepler to Swope sequences.
IDIOGNATHODUS LOBATUS Gunnell, 1933 Figures 45.16‐45.24, 53.16. Idiognathodus lobatus Gunnell, 1933, pl. 31, figs. 17, 18. Barrick and Boardman, 1989, p. 185, pl. 1, figs. 7, 9, 24; Barrick and Walsh, 1999, p. 154, fig. 6.4 (holotype). Idiognathodus delicatus Gunnell, 1931. Ellison, 1941, pl. 22, fig. 33. Idiognathodus modulatus Gunnell, 1933, pl. 31, fig. 15.
Diagnosis: P1 element with a reduced elongate rostral lobe and robust normal caudal lobe.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio and the element is curved toward the caudal side. The platform is ornamented with complete transverse ridges that exhibit weak medial disruption along the dorsal margin. The dorsal margin of the platform is pointed to subrounded. The caudal rostral lobe is robust and reduced through intermediate‐sized forms, but is normal and robust in the largest forms. The caudal lobe is ornamented with nodes, most of which are poorly defined or partially fused with neighboring nodes. The rostral lobe is reduced elongate, extending one‐half to three‐quarters the length of the platform. Ornamentation of the rostral lobe consists of poorly defined nodes. The ventral
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portion of the lobe is wide enough for two rows of ornamentation, reducing down to one row dorsally. The adcarinal ridges extend beyond the ventral margin of the platform a moderate distance. The caudal adcarinal ridge is slightly longer than the rostral adcarinal ridge. The dorsal termination of the caudal adcarinal ridge is the ventral margin of the caudal accessory lobe. It does not merge with the margin between the lobe and the platform or ornamentation on the lobe. The rostral adcarinal ridge merges with the ornamentation on the ventral margin of the rostral lobe forming a ventral ridge on the lobe margin. The medial carina is short and truncated by the first transverse ridge of the platform.
Discussion: Idiognathodus lobatus is closely related to I. folium, I. confragus, and I. kansensis. Idiognathodus folium and I. kansensis have expanded rostral lobes instead of the reduced elongate lobe of I. lobatus. The accessory lobes in I. confragus are robust and ventrally shifted, which differentiates them from I. lobatus. Other similar species include I. swadei, I. turbatus, and I. siculus. In all three cases the expanded rostral lobes are protruding and robust instead of reduced elongate in nature.
Type Specimen: Figure 45.18 (UM 492‐5) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figures 45.16 (TTU 08/060), 45.17 (TTU 08/061), 45.19 (TTU 08/062), 45.20 (TTU 08/063), 45.21 (TTU 08/064), 45.22 (TTU 08/065), and 45.23 (TTU 08/066) from the Swope Sequence.
Occurrence: Idiognathodus lobatus first appears in the Hushpuckney Shale of the Swope Sequence. Specimens are only recovered from the Swope Sequence.
IDIOGNATHODUS MAGNIFICUS Stauffer and Plummer, 1932 Figures 49.4‐49.15, 50.1‐50.7, 50.9, 53.22, 53.23. Idiognathodus magnificus Stauffer and Plummer, 1932, p. 197, pl. IV, fig. 18, 19 only; Ellison, 1941, pl. 23, fig. 2, 3; Barrick and Boardman, 1989, p.187, pl. 2, figs 9, 15, 19, 20, p. 185, pl. 1, figs. 1, 2; Barrick and Walsh, 1999, p. 150, fig. 3.2 (lectotype), 3.3 (re‐illustration);
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Stevens et al., 2001, p. 122, fig. 15.18; Ritter et al., 2002, p. 510, fig. 9.16; Barrick et al., 2004, p. 241, pl. 4, fig. 6, 8 only (re‐illustration). Idiognathodus claviformis Gunnell 1931. Ellison, 1941, pl. 23, fig. 16. Idiognathodus delicatus Gunnell, 1931. Ellison, 1941, pl. 22, fig. 34. Idiognathodus kansensis Gunnell, 1933, pl. 32, figs. 62, 63, 64. Idiognathodus walteri Gunnell, 1933, pl. 32, fig. 9. Idiognathodus warei Gunnell, 1933, pl. 32, figs. 59, 60, 61.
Diagnosis: Species with an asymmetric P1 element pair. The sinistral element exhibits a robust expanded rostral lobe and a platform with a high dorso‐ventral to rostro‐caudal ratio (thin). The dextral element exhibits a robust moderately restricted rostral lobe and a platform with a moderate to low dorso‐ventral to rostro‐caudal ratio (broad).
Description: The platform of the sinistral P1 element has a high dorso‐ventral to rostro caudal ratio. The platform is crossed by complete transverse ridges that show a medial disruption, usually in the form of a weakly developed medial to caudal eccentric groove. The dorsal tip of the platform is most commonly subrounded. The normal caudal lobe is robust with discrete hemispherical ornamentation. In some specimens, the outermost nodes on the caudal lobe can be partially to completely fused. The rostral lobe is expanded along the linear (not curved) rostral margin of the platform. The rostral lobe is most robust at the ventral margin of the element and narrows to its termination. Discrete nodes ornament the rostral lobe. In some specimens, the dorsal‐most portions of the rostral lobe can be relatively unornamented. The adcarinal ridges are short, extending only a short distance beyond the ventral margin of the platform. The termination of both adcarinal ridges is along the same rostro‐caudal horizon, neither is longer than the other. The caudal adcarinal ridge shapes the rostral margin of the caudal lobe until it is truncated by the first transverse ridge. The remaining separation between the caudal lobe and the central platform is formed by a ridge extending from the caudal margin of the element. The rostral adcarinal ridge is truncated by the first transverse ridge on the caudal margin of the rostral lobe. As with the caudal side, the rostral margin forms a ridge that completes separation of the rostral lobe from the central platform. The medial carina is short and extends less than one‐quarter the length of the platform.
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The platform of the dextral P1 element has a low dorso‐ventral to rostro‐caudal ratio due to the robust nature of the accessory lobes and a broad platform shape. Coarse transverse ridges ornament the platform of the element. Only the dorsal‐most transverse ridges exhibit any evidence of disruption. The dorsal margin of the platform is subrounded. The protruding and robust caudal accessory lobe is the most prominent feature of the element. The caudal lobe is ornamented with discrete nodes and a few fused nodes. The moderately restricted rostral lobe is robust but does not protrude from the rostral margin. In some cases an inflection point is formed where the rostral margin of the lobe joins with the rostral margin of the dorsal platform. The adcarinal ridges do not form high elevation features on the platform but are subdued in nature. The caudal adcarinal ridge is longer than the rostral adcarinal ridge in most specimens. The caudal adcarinal ridge flares away from the blade without forming a frill. The margin separating the caudal lobe from the platform is formed by the adcarinal ridge extending from the ventral margin and a second ridge formed by the most rostral row of lobe ornamentation. The rostral adcarinal ridge forms a distinctive margin to the rostral lobe. The medial carina is average in length and is truncated by the first transverse ridge of the platform.
Discussion: The sinistral element Idiognathodus magnificus is most similar in morphology to the older I. swadei. While the two species are separated by an entire depositional sequence, the two may be distinguished by the much more robust and protruding rostral lobe exhibited by I. swadei. Similarly, the robust and protruding nature of the rostral lobe in I. turbatus, along with its chaotic and grooved platform, distinguishes it from I. magnificus. Idiognathodus lobatus has a much less robust rostral lobe than I. magnificus. Idiognathodus confragus has a ventral shift in the caudal lobe development as well as an elongate medial carina that distinguishes it from I. magnificus. The dextral element of Idiognathodus magnificus is most closely related to I. fusiformis, I. corrugatus, and I. multinodosus. In the cases of I. corrugatus and I. multinodosus, the missing rostral lobe can be used to distinguish them from the moderately restricted rostral lobe of I. magnificus. Idiognathodus fusiformis is distinguished from I. magnificus because I. fusiformis has a higher dorso‐ventral to rostro‐caudal ratio and a less robust, more restricted rostral lobe. Idiognathodus species 3 and I. species 4 co‐occur with I. magnificus and can be differentiated by their inset rostral lobe. The asymmetry of the pair of P1 elements of Idiognathodus magnificus is
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the first appearance of asymmetry in Missourian species of Idiognathodus. The thinner, sinistral form was named I. kansensis by Gunnell (1933), which is now a junior synonym of I. magnificus.
Type Specimen: Figure 50.9 (BEG 19164) the cotype specimen (dextral) of Stauffer and Plummer (1932), lectotype specimen of Barrick and Walsh (1999), from the Wolf Mountain Shale, equivalent to the Dewey Sequence. Figure 49.11 (BEG 20926) the cotype specimen (sinistral) of Stauffer and Plummer (1932).
Illustrated Specimens: Figure 49.4 (TTU 08/136), 50.1 (TTU 08/147), 50.5 (TTU 08/151), 50.6 (TTU 08/152), and 50.7 (TTU 08/153) from the Dennis Sequence. Figures 49.5 (TTU 08/137), 49.6 (TTU 08/138), 49.10 (TTU 08/141), and 50.4 (TTU 08/150) from the Hogshooter Sequence. Figures 49.7 (TTU 08/139), 49.9 (TTU 08/140), 49.12 (TTU 08/143), 49.13 (TTU 08/144), 49.14 (TTU 08/145), 49.15 (TTU 08/146), and 50.2 (TTU 08/148) from the Dewey Sequence. Figure 50.3 (TTU 08/149) from the Cherryvale Sequence.
Occurrence: Idiognathodus magnificus first appears in the Stark Shale of the Dennis Sequence. Specimens are recovered from the interval spanning the Dennis to Dewey sequences in this study interval.
IDIOGNATHODUS MULTINODOSUS Gunnell, 1933 Figures 48.5‐48.8, 53.25. Idiognathodus multinodosus Gunnell, 1933, pl. 33, fig. 5. Streptognathodus oppletus Ellison, 1941, pl. 22, fig. 13. Barrick and Walsh, 1999, p. 157, fig. 8.3.
Diagnosis: P1 element with a ghost rostral lobe, a reduced caudal lobe, marginal disruption of transverse ridges and an elongate medial carina.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio. The margins of the platform are elevated and separated from the central platform by both rostral and caudal marginal grooves. The margins are ribbed in alignment with the complete transverse ridges that ornament the interior portion of the platform. The dorsal margin of the platform is subrounded to rounded. The caudal lobe is reduced in shape often having only a single node or
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short ridge branching from the caudal adcarinal ridge. The ghost rostral lobe is expressed smooth rostral platform that is very narrow and at most extends one‐half the length of the platform. The ghost lobe becomes incorporated into the rostral margin in larger specimens. The adcarinal ridges are long, equal in length and extend up to one‐quarter the length of the blade. The caudal adcarinal ridge merges with the elevated caudal margin of the element and effectively separates the caudal lobe from the central platform. In larger specimens the caudal adcarinal ridge can form a fused ridge that splits from the margin and ornaments the caudal lobe. The rostral adcarinal ridge merges with the elevated rostral margin separating the ghost lobe from the central platform. The medial carina extends between one‐quarter and one‐ half the length of the platform.
Discussion: Idiognathodus multinodosus is most closely related to I. corrugatus. The ghost rostral lobe of I. multinodosus distinguishes it from I. corrugatus, which has no rostral lobe. In addition, I. corrugatus does not have the elevated platform margins or the distinctive marginal grooves that are seen in I. multinodosus. All other specimens in this study interval are either missing or have ornamented rostral lobes that distinguish them from I. multinodosus. Idiognathodus multinodosus was originally named by Gunnell (1933) but the holotype specimen was reclassified (and re‐illustrated) by Ellison (1941) to the genus Streptognathodus as S. oppletus. Careful examination has revealed that the elevated platform margins and marginal groove give the superficial appearance of the troughing characteristic of Streptognathodus. The main body of the platform is flat, not troughed, and, therefore, the species has been returned to the genus Idiognathodus.
Type Specimen: Figure 48.5 (UM 513‐3), the holotype specimen of Gunnell (1933) from the Quivira Shale of the Dewey Sequence.
Illustrated Specimens: Figures 48.6 (TTU 08/116) and 48.7 (TTU 08/117) from the Dewey Sequence.
Occurrence: Idiognathodus multinodosus first appears in the lower clay shale of the Quivira Shale in the Dewey Sequence. In this study interval, it is only collected from the Dewey Sequence.
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IDIOGNATHODUS SICULUS Gunnell, 1933 Figures 44.9‐44.12, 44.14‐44.16, 53.11. Idiognathodus siculus Gunnell, 1933, pl. 31, fig. 14; Barrick and Walsh, 1999, p. 154, fig. 6.2. Idiognathodus clavatus Gunnell, 1933, pl. 31, fig. 19; Barrick and Walsh, 1999, p. 153, fig. 5.4. Idiognathodus sulciferus Gunnell, 1933. Ritter et al., 2002, p. 508, fig. 8.24.
Diagnosis: P1 element with a robust and protruding rostral lobe exhibiting nodose ornamentation on only the ventral portions of the rostral lobe.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio. The platform is ornamented by closely‐spaced, complete transverse ridges. Weak disruption of the transverse ridges in the dorsal half of the platform is observed in some specimens. The dorsal margin of the platform is subrounded. The normal caudal accessory lobe is robust and protruding. Discrete to semi‐fused nodes ornament the caudal lobe. The rostral lobe is expanded to slightly over one‐half the length of the platform. The rostral lobe is robust and protrudes from the rostral margin of the element. The ventral half of the rostral lobe is ornamented with discrete nodes. The dorsal half is similar to a ghost lobe in that is smooth and unornamented, yet clearly is distinct from the central platform. Adcarinal ridges are very short, with the caudal adcarinal ridge extending slightly further in the ventral direction than the rostral adcarinal ridge. The caudal adcarinal ridge intersects with the ventral margin of the caudal lobe but does become involved with the ornamentation or separation of the lobe. The ornamentation on the inside of the lobe is very discrete and forms a series of punctuated ridges rather than a single continuous ridge. The rostral adcarinal ridge terminates at the ventral margin of the lobe and does not become involved with lobe ornamentation or separation. The medial carina is short and terminates prior to the first complete transverse ridge.
Discussion: Idiognathodus siculus is a rare, but recognizable species in the study interval. It is most similar to the species I. swadei, I. turbatus, I. vorax, and I. species 2. Both I. swadei and I. turbatus have similar protruding and robust rostral lobes, but neither exhibit the unique pattern of ventral‐only ornamentation shown in I. siculus. The nature of the protruding lobe is almost rectangular in I. siculus; in both I. swadei and I. turbatus it is more rounded. The rostral lobe in I. vorax is highly ornamented and elongate in shape. Idiognathodus species 2 may have derived
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from I. siculus, but is easily distinguished from I. siculus by its less robust expanded rostral lobe and the medial groove that disrupts its transverse ridges.
Type Specimen: Figure 44.9 (UM 492‐2) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figures 44.10 (TTU 08/038), 44.11 (TTU 08/039), 44.12 (TTU 08/040), and 44.14 (TTU 08/042) from the Swope Sequence. Figure 44.15 (TTU 08/043) from the Shale Hill Sequence. Figure 44.16 (TTU 08/044) from the Dennis Sequence.
Occurrence: Idiognathodus siculus first appears in the Exline Limestone of the Shale Hill Sequence. Specimens are recovered from the interval spanning the Shale Hill to Dennis sequences.
IDIOGNATHODUS SULCIFERUS Gunnell, 1933 Figures 40.2‐40.5, 40.9‐40.11, 53.7. Idiognathodus sulciferus Gunnell, 1933, pl. 31, fig. 16; Barrick and Boardman, 1989, p. 185, pl. 1, figs. 9, 23, 24; Barrick and Walsh, 1999, p. 154, fig. 6.1 (holotype); Ritter et al., 2002, p. 508, fig. 8.25; Barrick et al., 2004, p. 241, pl. 4, fig. 13 (holotype); Rosscoe and Barrick, In Press, pl. 3, figs. 12‐17, pl. 6, figs. 2a‐2d. Idiognathodus chiriformis Gunnell, 1933, pl. 31, fig. 23. Idiognathodus magnificus Stauffer and Plummer, 1932. Zhihao and Yuping, 2003, p. 395, pl. 4, fig. 23.
Diagnosis: P1 element with a moderately restricted, continuous rostral lobe, normal caudal lobe and a platform ornamented with complete transverse ridges that exhibit minor caudal deflection in the ventral direction.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The platform is ornamented with complete transverse ridges. The transverse ridges are deflected ventrally along the medial axis in some specimens. The dorsal platform margin is subrounded in shape. The caudal accessory lobe is normal in shape and ornamented with large
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discrete nodes. In smaller specimens, the caudal lobe is more reduced in shape. The rostral lobe is moderately expanded, but is not robust, and does not protrude from the ventral margin of the element. The rostral lobe is ornamented by discrete nodes that lose some definition at the margin of the lobe. The adcarinal ridges are moderate in length, with the caudal adcarinal ridge extending further in the ventral direction than the rostral adcarinal ridge. The caudal adcarinal ridge merges with the margin separating the caudal lobe from the central platform. The rostral adcarinal ridge forms a ventral ridge on the ventral margin of the rostral lobe. The medial carina does not extend beyond one‐quarter the length of the platform.
Discussion: Idiognathodus sulciferus is one of the first species to be derived following the Late Desmoinesian extinction. It is closely related to and co‐occurs with I. swadei, I. harkeyi, I. fusiformis, I. eccentricus, and I. corrugatus. Idiognathodus swadei has an expanded rostral lobe that distinguishes it from I. sulciferus. Idiognathodus eccentricus has a restricted rostral lobe and a caudal eccentric groove that distinguishes it from I. sulciferus. Idiognathodus corrugatus does not have rostral lobe. Idiognathodus harkeyi and I. fusiformis both have a moderately restricted rostral lobe, but both are more robust and protruding than the continuous rostral lobe of I. sulciferus.
Type Specimen: Figure 40.11 (UM 492‐4) the holotype specimen of Gunnell (1933) from the Hushpuckney Shale of the Swope Sequence.
Illustrated Specimens: Figure 44.2 (SUI 108256) and 44.10 (SUI 108258) from the Shale Hill Sequence. Figures 44.3 (TTU 08/004) and 44.5 (TTU 08/005) from the Swope Sequence. Figures 44.4 (SUI 108255) and 44.9 (SUI 108257) from the Hertha Sequence.
Occurrence: Idiognathodus sulciferus first appears in the Checkerboard Limestone of the Hepler Sequence. Specimens are recovered from the interval spanning the Hepler to Swope sequences.
IDIOGNATHODUS SWADEI Rosscoe and Barrick, In Press Figures 39.1‐39.16, 53.2‐53.4. Idiognathodus swadei Rosscoe and Barrick, In Press, pl. 2, figs. 1‐18, pl. 6, figs. 3a‐3d.
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Idiognathodus delicatus Gunnell, 1931. Ellison, 1941, pl. 22, fig. 35. Idiognathodus clavatulus (Gunnell, 1933). Barrick and Boardman, 1989, p. 185, pl. 1, fig. 14. Idiognathodus lobatus Gunnell, 1933. Barrick and Boardman, 1989, p. 185, pl. 1, fig. 23. Idiognathodus sulciferus Gunnell, 1933. Ritter et al., 2002, p. 508, figs. 8.8, 8.24. Idiognathodus species 1 of Swade, 1985, p. 55, figs. 18.4, 18.5, 18.11 (only). Idiognathodus sp. Mendez, 2006, p. 250, fig. 5.5.
Diagnosis: P1 element with a robust and protruding expanded rostral accessory lobe that is at the same elevation as the central platform surface.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The dorsal platform is crossed by coarse transverse ridges that are deflected in the ventral direction or disrupted in alignment with the caudal adcarinal groove. The dorsal margin of the platform is pointed. The caudal lobe shows the greatest development in the rostro‐caudal direction. The dorsal extent of the caudal lobe is typically 1/2 the length of the platform with rostro‐caudal extent of the lobe reaching nearly the same length. The caudal lobe is a protruding, slightly triangular feature, decorated with discrete nodes aligned with the curvature of the caudal adcarinal ridge. The rostral lobe is elongate with the rostro‐caudal extent of the lobe reaching a maximum of half the dorso‐ventral dimension. In mature specimens the rostral lobe is ornamented with two to three rows of discrete, hemispherical nodes. Adcarinal ridges are equal in length to the medial carina, extending one‐quarter to one‐ third the length of the platform. Adcarinal ridges form a short, slightly flared collar around the dorsal blade. The constriction of the adcarinal ridges around the medial carina is tight, leaving a very shallow adcarinal groove that in most cases is the same elevation of the surrounding platform. The adcarinal ridges typically form a fused ridge ending ventrally with a few discrete nodes at an elevation no higher than the surrounding platform ornamentation.
Discussion: Idiognathodus swadei can be distinguished from all other co‐occurring idiognathodid conodonts in the study interval by its flat undisrupted dorsal platform ornamented with transverse ridges and its protruding rostral lobe. Idiognathodus swadei can be distinguished from I. turbatus by the presence of medial nodosity in I. turbatus. The less protruding rostral lobes of I. folium and I. lobatus distinguish them from I. swadei. The younger I. kansensis has a
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more separate rostral lobe than I. swadei. Specimens of I. sagittalis that exhibit weak medial nodosity can be confused with I. swadei. Idiognathodus swadei has a more dorsally elongate rostral lobe than I. sagittalis. The rostral lobe of I. swadei is at the same elevation as the main body of the platform as opposed to the lower elevation discretely bounded rostral lobe of I. sagittalis. Specimens SUI 108240 (Figure 39.5) and SUI 108237 (Figure 39.9) of I. swadei have a more distinctively bounded rostral lobe than other specimens, and may reflect the development of similar characters to I. sagittalis. Idiognathodus swadei is the only member of the genus that survives the Late Desmoinesian extinction in the Midcontinent region. Juvenile elements that show both rostral and caudal lobes, slight troughing and a long medial carina, are the only juvenile forms encountered immediately above the extinction level. All early Missourian forms of Idiognathodus in the Midcontinent region are derived from I. swadei.
Type specimen: Figure 39.12 (SUI 108241) the holotype specimen of Rosscoe and Barrick (In Press) from the Nuyaka Creek Shale of the Lost Branch Sequence.
Illustrated specimens: Figures 39.1, 39.2, 39.3, 39.4, and 39.6 from the Lost Branch Sequence. Figures 39.5, 39.8, and 39.13 from the Hepler Sequence. Figures 39.7, 39.11, and 39.15 from the Swope Sequence. Figures 39.9, 39.10, and 39.1 6 from the Hertha Sequence. Figure 39.14 from the Shale Hill Sequence.
Occurrence: The first appearance of Idiognathodus swadei cannot be determined until work in older Desmoinesian sequences has been completed. In this study, specimens are recovered from the interval spanning the Lost Branch to Swope Sequences.
IDIOGNATHODUS SYMMETRICUS Gunnell, 1933 Figures 48.12, 48.13, 48.15, 48.16, 48.18‐48.23, 53.24. Idiognathodus symmetricus Gunnell, 1933, pl. 32, fig. 3. Idiognathodus simplex Gunnell, 1933, pl. 32, fig. 9.
Diagnosis: P1 element with ventrally shifted reduced caudal lobes and reduced rostral lobes with a pointed dorsal margin.
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Description: The platform of the P1 element has a high dorso‐ventral to rostro caudal ratio. The platform is ornamented with complete transverse ridges that exhibit weak medial disruption in some specimens. The dorsal margin of the platform is subrounded to pointed. The caudal accessory lobe is reduced in shape and ventrally shifted. The reduced caudal lobe varies from a high elevation ridge formed in conjunction with the caudal adcarinal ridge to two distinct rows of poorly defined nodes. The rostral accessory lobe is reduced and extends one‐quarter the length of the platform. The lobe is ornamented with discrete nodes. The adcarinal ridges are long and extend up to one‐quarter the length of the blade in the ventral direction. The caudal adcarinal ridge is longer than the rostral adcarinal ridge by a small amount. The caudal adcarinal ridge forms the interior margin to the caudal accessory lobe. In specimens with poorly developed caudal lobes, the caudal adcarinal ridge forms the bulk of the caudal lobe. The rostral adcarinal ridge forms the interior margin of the rostral accessory lobe. The medial carina is elongated, extending just beyond one‐quarter the length of the platform.
Discussion: Idiognathodus symmetricus is most closely related to I. cherryvalensis and I. biliratus. In both I. cherryvalensis and I. biliratus there are no lobes present, rather than reduced rostral and caudal lobes. The retention of the high elevation caudal margin in some specimens of I. symmetricus is similar to the high elevation caudal margin seen in I. biliratus and rarely in I. cherryvalensis. Idiognathodus symmetricus is likely derived from I. cherryvalensis whose ancestor is I. biliratus. The only other species with ventrally shifted lobes in the study is I. confragus, but the lobes in I. confragus are expanded and robust.
Type Specimen: Figure 48.20 (UM504‐2) the holotype specimen of Gunnell (1933) from the Wea Shale of the Cherryvale Sequence.
Illustrated Specimens: Figures 48.12 (TTU 08/122), 48.13 (TTU 08/123), 48.15 (TTU 08/125), 48.19 (TTU 08/129), 48.21 (TTU 08/130), 48.22 (TTU 08/131), and 48.23 (TTU 08/132) from the Dewey Sequence. Figures 48.16 (TTU 08/126) and 48.18 (TTU 08/128) from the Cherryvale Sequence.
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Occurrence: Idiognathodus symmetricus is first recovered in the Block Limestone of the Cherryvale Sequence. Specimens are recovered from the interval spanning the Cherryvale to Dewey sequences in this study interval.
IDIOGNATHODUS TURBATUS Rosscoe and Barrick, In Press Figures 41.1‐41.13, 53.12. Idiognathodus turbatus Rosscoe and Barrick, In Press, pl. 4, figs. 1‐9, pl. 6, fig. 5a‐5d. Idiognathodus cancellosus (Gunnell, 1933). Zhihao and Yuping, 2003, p. 395, pl. 4, fig. 21. Idiognathodus claviformis Gunnell, 1931. Ellison, 1941, pl. 23, fig. 14. Idiognathodus sagittalis Kozitskaya, 1978. Barrick and Boardman, 1989, p. 185, pl. 1, figs. 10, 14. Idiognathodus species A Barrick et al., 1996. Ritter, et al, 2002, p. 508, fig. 8.10‐8.12, 8.15, 8.20; Barrick et al., 2004, p. 241, pl. 4, fig. 11.
Diagnosis: P1 element with a robust and protruding expanded rostral accessory lobe (at the same level as the platform surface) and a ventral platform with medial nodosity and shallow medial trough.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The platform of this species is extremely variable. Most specimens exhibit a weak eccentric groove to the caudal side of a medial node row extending almost to the dorsal tip of the element. The larger specimens develop chaotic platforms. The dorsal tip ranges from pointed to subrounded. Specimens with the most rounded tips tend to have the most chaotic dorsal platforms. Both the caudal and rostral lobes are extremely well developed and ornamented with discrete hemispherical nodes. The caudal lobe is ornamented in a concentric pattern around the center of the lobe. The rostral lobe is longer in the dorsal direction than in the rostral direction. In large specimens, where the protruding rostral lobe is especially robust, the ornamentation forms as rays of nodes that begin aligned with a transverse ridge and curve ventrally to the ventral margin of the element. The adcarinal ridges are longer than most of the ridges seen in other species of the study interval. The caudal adcarinal ridge can be twice as long as the rostral adcarinal ridge. On the platform both adcarinal ridges and the medial carina form a series of dorso‐ventrally aligned
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low‐elevation ridges. The caudal adcarinal ridge flares off the platform. The caudal margin of the element sits at a slightly higher elevation than the rostral margin due to the flaring, high‐ elevation caudal adcarinal ridge.
Discussion: Idiognathodus turbatus has medial nodosity or a chaotically modified platform that can be distinguished from I. swadei. Idiognathodus turbatus can be distinguished from I. species 1 and I. vorax by the shorter and more protruding rostral lobe of I. turbatus. Idiognathodus turbatus is close in appearance to the Eurasian conodont I. sagittalis, but can be distinguished by the relationship of the rostral lobe to the central platform. In I. sagittalis, the central platform is distinctively separated from the lower elevation rostral lobe. In I. turbatus, the central platform and rostral lobe are not distinctively separate and are equal in elevation. Idiognathodus species A of Barrick et al. (1996) is included in this species as it represents those specimens with the most clearly defined medial nodosity.
Type specimen: Figure 41.9 (SUI 108266) the holotype specimen of Rosscoe and Barrick (In Press) from the Mound City Shale of the Hertha Sequence.
Illustrated specimens: Figures 41.1 (SUI 108268), 41.3 (SUI 108271), 41.5 (SUI 108265), 41.7 (SUI 108270), 41.10 (SUI 108264), 41.12 (SUI 108267), and 41.13 (SUI 108272) from the Hertha Sequence. Figures 41.2 (SUI 108260) and 41.11 (SUI 108263) from the Shale Hill Sequence. Figure 41.4 (SUI 108262) transitional specimen from the Hepler Sequence. Figure 41.6 (TTU 08/006) and 41.8 (TTU 08/006) from the Swope Sequence.
Occurrence: Idiognathodus turbatus first appears in the Exline Limestone of the Shale Hill Sequence. Specimens are collected from the interval spanning the Shale Hill to Swope sequences.
IDIOGNATHODUS VORAX Rosscoe and Barrick, In Press Figures 42.4, 42.6, 42.7, 42.12, 42.13, 53.14. Idiognathodus vorax Rosscoe and Barrick, In Press, pl. 5, figs. 1, 3, 4, pl. 6, fig. 6a‐6d.
Diagnosis: P1 element with a robust elongate rostral lobe and robust normal caudal lobe.
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Description: The platform of the P1 element has a low dorso‐ventral to rostro‐caudal ratio. Coarse transverse ridges cross the dorsal platform and are occasionally disrupted along the dorso‐ventral axis. This disruption is not continuous across all transverse ridges, but is usually restricted to the most dorsal portions of the element. The caudal lobe protrudes and is ornamented with discrete nodes. The rostral margin of the platform is the rostral margin of the rostral lobe of the P1 element. The highly elongate rostral lobe connects to the dorsal tip of the platform and is ornamented with discrete hemispherical nodes. The rostral lobe is not separated from the platform and sits at the same elevation. The adcarinal ridges are no higher than the transverse ridges or nodes ornamenting the platform and extend a very short distance away from the ventral platform margin. The caudal adcarinal ridge is slightly longer than the rostral adcarinal ridge. The medial carina is low in elevation and extends to its truncation at the first ventral transverse ridge along with the adcarinal ridges.
Discussion: This distinctive species is rare in the study interval. The lack of medial nodosity and the rostral elongation of the rostral lobe in Idiognathodus vorax can be used to distinguish it from I. species 1. The elongate rostral lobe is the characteristic that distinguishes I. vorax from its ancestor I. swadei, and any other species in the study interval.
Type specimen: Figure 42.12 (SUI 108274) the holotype specimen of Rosscoe and Barrick (In Press) from the Mound City Shale of the Hertha Sequence.
Illustrated specimens: Figures 42.4 (TTU 08/008) and 42.7 (TTU 08/009) from the Swope Sequence. Figures 42.6 (SUI 108277) and 42.13 (SUI 108276) from the Hertha Sequence.
Occurrence: Idiognathodus vorax first appears in the Mound City Shale of the Hertha Sequence. Specimens are recovered from the interval spanning the Hertha to Swope sequences.
IDIOGNATHODUS SPECIES 1 Rosscoe and Barrick, In Press Figures 42.1, 42.2, 42.8, 53.13. Idiognathodus species 1 Rosscoe and Barrick, In Press, pl. 5, figs. 2, 5‐7, pl. 6, figs. 4a‐4d.
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Diagnosis: P1 element with an elongate rostral lobe, normal caudal lobe, and chaotic platform ornamentation.
Description: The platform of the P1 element has moderate dorso‐ventral to rostro‐caudal ratio. The platform is ornamented with coarse transverse ridges that are disrupted by medial nodosity or chaotically. The dorsal tip of the platform is subrounded in shape. The caudal lobe protrudes from the margin of the platform and is ornamented with nodes arranged concentrically around the center of the lobe. The ventral margin of the caudal lobe is set more ventrally than the same margin on the rostral lobe. The elongate rostral lobe is long and narrow and decreases in width toward the dorsal tip of the element. The rostral lobe does not extend completely to the dorsal tip of the platform. Near the ventral end of the rostral lobe, ornamentation consists of two nodes that can become fused in larger specimens. Most of the length of the rostral lobe is ornamented with a single row of nodes. The nodes decrease in width from the ventral to dorsal end of the rostral lobe. Adcarinal ridges are moderate in length. The caudal adcarinal ridge extends farther ventrally than the rostral adcarinal ridge. In most specimens, the adcarinal ridges are poorly defined and consist of a low series of partially‐fused to fused, short denticles. The medial carina is a ridge extending dorsally to the first transverse ridge where it merges with a medial row of nodes lying in a shallow groove along the central axis of the element.
Discussion: Specimens of Idiognathodus species 1 are quite rare in early Missourian strata. Specimens of I. species 1 have a less elongated and narrower rostral lobe than I. vorax, as well as the presence of a chaotic ornamentation or medial nodosity. The species I. swadei and I. turbatus exhibit a protruding rostral lobe that is elongate in the rostral direction as well as the dorsal direction, unlike I. species 1.
Illustrated specimens: Figures 42.1 (SUI 108275), 42.2 (SUI 108279) and 42.8 (SUI 108278) from the Hertha Sequence.
Occurrence: Idiognathodus species 1 first appears in the Mound City Shale of the Hertha Sequence. Specimens are recovered only from the Hertha Sequence.
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IDIOGNATHODUS SPECIES 2 Figures 46.9‐46.12, 53.20.
Diagnosis: P1 element with an expanded non‐protruding rostral lobe and well defined medial groove.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio. The platform is ornamented with closely‐spaced transverse ridges. A medial groove splits the platform symmetrically and the transverse ridges are deflected ventrally at the groove. The dorsal margin of the platform is subrounded. The caudal lobe is normal in intermediate and large specimens (reduced in small specimens). The caudal lobe is ornamented with discrete nodes, some of which have fused to form small ridges in larger specimens. The rostral accessory lobe does not protrude from the rostral margin of the element and is ornamented with nodes of variable definition. In smaller specimens, the dorsal portions of the rostral lobe are smooth and unornamented. The adcarinal ridges are long and terminate equally along the blade. The caudal adcarinal ridge has a small frill that is lost in larger specimens. The caudal adcarinal ridge forms the interior margin of the caudal lobe. The rostral adcarinal ridge reduces in definition at the ventral margin of the platform, but forms the interior margin of the rostral lobe. The medial carina is normal in length, extending less than one‐quarter the length of the platform. A few dribbling nodes may be present beyond the termination of the medial carina.
Discussion: Idiognathodus species 2 is closely related to I. swadei, I. turbatus, I. siculus, and I. folium. Idiognathodus species 2 is distinguished from I. swadei, I. siculus, and I. folium by its medial groove, as the other species all have continuous transverse ridges. Idiognathodus turbatus has a much more protruding and robust rostral lobe, and a more chaotic disruption of transverse ridges than I. species 2. Idiognathodus species 2 is a rare form that has only been identified from the Mound Valley Sequence. It most likely is derived from I. siculus. The retention of smooth ventral portions of rostral lobes in small specimens of I. species 2 suggests the retention of the adult I. siculus characters in juveniles of I. species 2.
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Illustrated Specimens: Figures 46.9 (TTU 08/074), 46.10 (TTU 08/075), 46.11 (TTU 08/076), 46.12 (TTU 08/077) from the Mound Valley Sequence.
Occurrence: Idiognathodus species 2 first appears in the clay shale facies of the Mound Valley Sequence. Specimens are recovered from the Mound Valley Sequence only.
IDIOGNATHODUS SPECIES 3 Figures 47.1‐47.6, 53.6.
Diagnosis: P1 element with an inset rostral lobe ornamented with a single node and a reduced caudal lobe.
Description: The platform of the P1 element has a moderate dorso‐ventral to rostro‐caudal ratio. The platform is ornamented by transverse ridges that are disrupted by a caudal marginal groove. The caudal marginal groove is best expressed in larger specimens and may be partially filled in smaller specimens. The dorsal margin of the platform is pointed to subrounded. The caudal lobe is highly reduced. In many cases, a single node will ornament the lobe surface. In larger specimens, the caudal lobe is ornamented with a single row of two or three partially fused nodes. The rostral lobe is inset into the infection point where the rostral adcarinal ridge merges with the rostral margin of the platform. The lobe is ornamented with a single hemispherical node. The adcarinal ridges are long and extend between one‐quarter and one‐half the length of the blade. The caudal adcarinal ridge forms a slight frill along its ventral extent after passing the ventral margin of the caudal lobe. The caudal adcarinal ridge forms the margin separating the caudal lobe from the central platform and merges with the caudal margin of the element. The rostral adcarinal ridge forms the margin between the rostral lobe and the central platform before merging with the rostral margin of the element. The medial carina is normal in length, not extending beyond one‐quarter the length of the platform.
Discussion: Idiognathodus species 3 is most similar to I. corrugatus, I. multinodosus, I. magnificus, I. fusiformis, I. eccentricus, and I. species 4. In the cases of I. corrugatus, I. multinodosus, I. fusiformis, and I. eccentricus the rostral lobe is not inset as is the case in I.
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species 3. Idiognathodus magnificus is the closest to having a true inset rostral lobe, but is really a poorly developed moderately restricted rostral lobe. The only other species to have an inset rostral lobe is I. species 4. Idiognathodus species 4 has a lower dorso‐ventral to rostro‐caudal ratio and has more developed rostral and caudal lobes than evidenced in I. species 3.
Illustrated Specimens: Figures 47.1 (TTU 08/091) and 47.5 (TTU 08/096) from the Swope Sequence. Figure 47.2 (TTU 08/092) from the Hogshooter Sequence. Figures 47.3 (TTU 08/094) and 47.4 (TTU 08/095) from the Dennis Sequence. Figure 47.6 (TTU 08/097) from the Mound Valley Sequence.
Occurrence: Idiognathodus species 3 first appears in the Hushpuckney Shale of the Swope Sequence. Specimens are recovered from the interval spanning the Swope to Hogshooter sequences.
IDIOGNATHODUS SPECIES 4 Figures 50.8, 50.10‐50.16, 53.21.
Diagnosis: P1 element with an inset rostral lobe and low dorso‐ventral axis to rostro‐caudal axis ratio.
Description: The expansion of the rostro‐caudal axis gives the P1 element a very low ratio between the dorso‐ventral axis and rostro‐caudal axis. The platform of the element is ornamented with coarse transverse ridges. Medial disruption of the transverse ridges is most common near the dorsal margin of the element. The dorsal margin of the platform is rounded to subrounded. The caudal lobe is reduced in most specimens, but appears normal in the largest specimens. The caudal lobe is ornamented with poorly defined nodes and protrudes from the caudal margin of the element. The rostral lobe is inset and is ornamented with between two and three poorly defined nodes or rostro‐caudally‐oriented short ridges. The adcarinal ridges are long and extend up to one‐quarter the length of the blade. The caudal adcarinal ridge terminates at the ventral margin of the caudal lobe and does not become a part of the separation or ornamentation of the caudal lobe. The rostral adcarinal ridge merges with the marginal ornamentation of the inset rostral lobe. The interior margin of the lobe is
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continuous with the rostral margin of the element, not the rostral adcarinal ridge. The medial carina is short and does not extend into the ornamented portion of the platform.
Discussion: Idiognathodus species 4 is one of the few forms with a low dorso‐ventral to rostro‐ caudal ratio. Idiognathodus vorax also has a low dorso‐ventral to rostro‐caudal ratio, but has an elongate rostral lobe instead of the inset rostral lobe of I. species 4. Idiognathodus species 3 has only a single ornamenting node on the rostral lobe and a medial groove, as opposed to the multi‐node ornamentation and medial disruption of transverse ridges in I. species 4. The inset rostral lobe indicates that I. species 4 may be derived from I. species 3.
Illustrated Specimens: Figures 50.8 (TTU 08/154), 50.10 (TTU 08/155), and 50.12 (TTU 08/157) from the Dennis Sequence. Figures 50.11 (TTU 08/156) and 50.16 (TTU 08/160) from the Dewey Sequence. Figures 50.13 (TTU 08/158) and 50.14 (TTU 08/159) from the Hogshooter Sequence. Figure 50.15 (TTU 08/093) from the Mound Valley Sequence.
Occurrence: Idiognathodus species 4 first appears in the clay shale of the Mound Valley Sequence. Specimens are recovered from the interval spanning the Mound Valley to Dewey sequences within the study interval.
Genus STREPTOGNATHODUS Stauffer and Plummer, 1932
Type Species: Streptognathodus excelsus Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 2, 5.
Diagnosis: Carminiscaphate P1 element with a deep medial trough and reduced or missing accessory lobes.
Description: The most prominent feature of the P1 element is the medial trough. The most common ornamentation of the oral surface is transverse ridges. The transverse ridges are commonly incomplete. The disruption of the transverse ridges by a well‐defined narrow groove or a wider more trough‐like disruption are more common than complete transverse ridges. Nodose ornamentation is restricted to the poorly developed accessory lobe structures and is rarely found on central platform. The blade is typically equal in length or slightly longer than the
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platform. The P2 element has yet to be adequately described in literature due to its similarity to
P2 elements in Idiognathodus.
Discussion: Streptognathodus differs from the genus Idiognathodus because it has a troughed platform as opposed to a flat platform. A troughed platform starts at elevated platform margins and decreases in elevation to the medial axis of platform. Some species of Idiognathodus have grooved disruptions of the platform, but the platforms are flat across the entire platform. Streptognathodus differs from the genus Swadelina because of its longer medial carina and more poorly developed accessory lobes.
STREPTOGNATHODUS EXCELSUS Stauffer and Plummer, 1932 Figures 52.1‐52.10, 53. 35, 53.36. Streptognathodus excelsus Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 2, 5; Ellison, 1941, pl. 22, figs. 15,17; Lane et al., 1971, p. 401, pl. 1, fig. 36; Barrick and Boardman, 1989, p. 187, pl. 2, figs. 3, 22; Ritter, 1995, p. 1146, fig. 9.19; Barrick and Walsh, 1999, p. 150, fig. 3.1 (holotype); Stevens et al., 2001, p. 122, fig. 15.19; Ritter et al., 2002, p. 510, figs. 9.9, 9.12; Zhihao and Yuping, 2003, p. 393, pl. 3, fig. 1; Barrick et al., 2004, p. 241, pl. 4, fig. 10. Streptognathodus corrugatus Gunnell, 1933. Ritter et al., 2002, p. 510, fig. 9.10. Streptognathodus subdivisus Gunnell, 1933, pl. 32, fig. 16.
Diagnosis: P1 element with a moderately restricted to expanded rostral lobe and normal caudal lobe.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal ratio. The platform is deeply troughed with a well defined groove splitting the platform symmetrically. The transverse ridges are truncated medially by the groove at the center of the trough and point ventrally along the medial axis. The groove is widest near the termination of the medial carina. The dorsal tip of the platform is subrounded to pointed in shape. The caudal accessory lobe is normal in shape and is ornamented with semi‐fused nodes. In some specimens the caudal lobe appears reduced due to its lack of robust development and less protruding form. The rostral accessory lobe is moderately restricted to expanded, is non‐protruding, and ornamented with poorly defined
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nodes. In larger specimens the dorsal portions of the rostral accessory lobe are incorporated into platform ornamentation giving the appearance of a moderately restricted rostral lobe. The adcarinal ridges are short, with the rostral adcarinal ridge terminating before the caudal adcarinal ridge beyond the ventral margin of the element. The caudal adcarinal ridge forms the margin separating the caudal lobe from the central platform of the element and merges with the caudal margin of the element. The rostral adcarinal ridge is short and merges with the ornamentation of the rostral lobe along the ventral margin. The medial carina is elongate, extending between one‐quarter and one‐third the length of the platform before truncating at the start of the medial groove. A few dribbling nodes may be found dorsal of the medial carina in the medial groove.
Discussion: Streptognathodus excelsus is the only species in the study interval to have a well developed rostral lobe. The moderately restricted to expanded rostral lobe of S. excelsus differs from S. sulcatus, S. elegantulus, and S. gracilis which have ghost or no rostral lobes. Streptognathodus increbescens has a inset to reduced rostral lobe instead of the moderately restricted to expanded rostral lobe of S. excelsus.
Type Specimen: Figure 52.6 (BEG 19168) the holotype specimen of Stauffer and Plummer (1932) from the Gradford Formation, Dewey Sequence Equivalent.
Illustrated Specimens: Figures 52.1 (TTU 08/185), 52.2 (TTU 08/186), 52.5 (TTU 08/189), and 52.9 (TTU 08/192) from the Hogshooter Sequence. Figures 52.3 (TTU 08/187), 52.4 (TTU 08/188), and 52.8 (TTU 08/191) from the Cherryvale Sequence. Figure 52.7 (TTU 08/190) from the Dewey Sequence.
Occurrence: Streptognathodus excelsus first appears in the lag at the base of the Hogshooter Sequence. Specimens are recovered from the interval spanning the Hogshooter to Dewey sequences in the study interval.
STREPTOGNATHODUS ELEGANTULUS Stauffer and Plummer, 1932 Figures 51.2‐51.5, 51.13, 51.25, 53.33, 53.34.
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Streptognathodus elegantulus Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 6, 7, 22, 27; Ellison, 1941, pl. 22, figs. 2, 5; Lane et al., 1971, p. 401, pl. 1, fig. 28; Kozitskaya, 1978, pl. XXVIII, figs. 5, 8‐11; Barrick and Boardman, 1989, p. 187, pl. 2, figs. 7, 13; Ritter, 1995, p. 1146, fig. 9.9; Zhihao and Yuping, 2003, p. 393, pl. 3, fig. 1, p. 395, pl. 4, figs. 12, 14; Barrick and Walsh, 1999, p. 152, figs. 4.3 (holotype), 4.4; Forke and Samankassou, 2000, p. 195, pl. 37, figs. 15, 16; Barrick et al., 2004, p. 241, fig. 3 (holotype). Streptognathodus spatulatus Gunnell, 1933, pl. 32, fig. 14.
Diagnosis: P1 element lacking both rostral and caudal accessory lobes.
Description: The platform of the P1 element has a very high dorso‐ventral to rostro‐caudal ratio due to the lack of accessory lobes. The platform is troughed and ornamented with transverse ridges that are bisected by a medial groove. In most specimens, the medial groove is defined only enough to disrupt the transverse ridges. In a few specimens, the transverse ridges can retain completeness across the medial axis of the trough. The dorsal margin of the platform is rounded to subrounded in shape. The rostral margin of the platform is elevated and merges with the short adcarinal ridge that forms the ventral portion of the margin. The caudal margin of the platform is elevated and merges with the caudal adcarinal ridge. The caudal adcarinal ridge is longer and more flaring than the rostral adcarinal ridge. The medial carina is average in length and may be followed a few dribbling nodes.
Discussion: Streptognathodus elegantulus differs from S. gracilis because S. gracilis has a reduced caudal lobe and better defined medial groove. Streptognathodus sulcatus has a low dorso‐ventral to rostro‐caudal ratio and a reduced caudal lobe that distinguishes it from S. elegantulus. Streptognathodus elegantulus differs from both S. excelsus and S. increbescens in that it has no rostral lobe.
Type Specimen: Figure 51.13 (BEG 19166) the holotype specimen of Stauffer and Plummer (1932) from the Gradford Formation, Dewey Sequence Equivalent.
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Illustrated Specimens: Figure 51.2 (TTU 08/163), 51.4 (TTU 08/165), and 51.25 (TTU 08/183) from the Cherryvale Sequence. Figure 51.3 (TTU 08/164) from the Hogshooter Sequence. Figures 51.5 (TTU 08/166) and 51.26 (TTU 08/184) from the Dewey Sequence.
Occurrence: Streptognathodus elegantulus first appears in the lag at the base of the Hogshooter Sequence. Specimens are recovered from the interval spanning the Hogshooter to Dewey sequences in the study interval.
STREPTOGNATHODUS GRACILIS Stauffer and Plummer, 1932 Figures 51.6, 51.7, 51.10‐51.12, 51.14‐51.24, 51.26, 53.31, 53.32. Streptognathodus gracilis Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 12, 23; Ellison, 1941, pl. 22, figs. 7, 11; Kozitskaya, 1978, pl XXVIII, figs. 8, 9; Barrick and Boardman, 1989, p. 187, pl. 2, fig. 6; Ritter, 1995, p. 1146, fig. 9.8; Barrick and Walsh, 1999, p. 150, fig. 2.1 (holotype); Barrick et al., 2004, p.241, pl. 4, fig. 5. Streptognathodus corrugatus Gunnell, 1933. Barrick and Boardman, 1989, p. 187, pl. 2, fig. 5. Streptognathodus elegantulus Stauffer and Plummer, 1932. Barrick and Boardman, 1989, p. 187, pl. 2, figs. 1, 12, 18. Streptognathodus holmesi Gunnell, 1933, pl. 32, figs, 1, 2. Streptognathodus multinodosus Gunnell, 1933, pl. 32, fig. 11. Streptognathodus sulciferus Gunnell, 1933, pl. 32, fig. 12.
Diagnosis: P1 element lacking a rostral lobe or exhibiting a ghost rostral lobe and reduced caudal lobe.
Description: The platform of the P1 element has a very high dorso‐ventral to rostro‐caudal ratio due to the reduced or missing nature of its accessory lobes. The platform is deeply troughed with a well developed medial groove that marks the base of the trough. All specimens are ornamented by transverse ridges at the margins. In rare cases, the transverse ridges may be complete across the entire platform surface. The medial groove is deep and well defined in nearly all specimens. The caudal margin of the element develops a non‐robust, non‐protruding reduced caudal lobe. The dorsal margin of the platform is subrounded in shape. The caudal lobe is very narrow and is commonly expressed as a ghost lobe, a reduced lobe with a single node, or a reduced lobe with up
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to three nodes. The rostral margin does not develop an ornamented accessory lobe, but in many of the specimens will develop a ghost rostral lobe that is reduced in size. The adcarinal ridges are of moderate length, extending up to one‐quarter the length of the blade. The caudal adcarinal ridge is slightly longer and is more flaring than the rostral adcarinal ridge. The caudal adcarinal ridge merges with the caudal margin of the element to develop a ridge separating the caudal lobe from the central platform. The rostral adcarinal ridge merges with the rostral margin of the platform. The medial carina ranges from short to moderate in length and extends less than one‐quarter the length of the platform.
Discussion: Streptognathodus gracilis differs from S. elegantulus because S. elegantulus has no true rostral or caudal lobe. Streptognathodus sulcatus has a low dorso‐ventral to rostro‐caudal ratio and a reduced caudal lobe that distinguishes it from S. gracilis. Streptognathodus gracilis differs from both S. excelsus and S. increbescens in that it has no rostral lobe or a reduced ghost rostral lobe.
Type Specimen: Figure 51.15 (BEG 19169) the holotype specimen of Stauffer and Plummer (1932) from the Gradford Formation, Dewey Sequence Equivalent.
Illustrated Specimens: Figures 51.6 (TTU 08/167), 51.16 (TTU 08/174), 51.20 (TTU 08/178), 51.21 (TTU 08/179), 51.22 (TTU 08/180), and 51.23 (TTU 08/181) from the Cherryvale Sequence. Figures 51.7 (TTU 08/168), 51.10 (TTU 08/170), 51.11 (TTU 08/171), 51.12 (TTU 08/172), and 51.17 (TTU 08/175) from the Hogshooter Sequence. Figures 51.19 (TTU 08/177) and 51.24 (TTU 08/182) from the Dewey Sequence.
Occurrence: Streptognathodus gracilis first appears in the lag at the base of the Hogshooter Sequence. Specimens are recovered from the interval spanning the Hogshooter to Dewey sequences in the study interval.
STREPTOGNATHODUS INCREBESCENS Stauffer and Plummer, 1932 Figures 52.10‐52.19, 53.37. Streptognathodus increbescens Stauffer and Plummer, 1932, p. 197, pl. IV, figs. 9, 15, 16; Barrick and Walsh, 1999, p. 152, figs. 4.1 (lectotype), 4.2.
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Streptognathodus excelsus Stauffer and Plummer, 1932. Barrick and Boardman, 1989, p. 187, pl. 2, figs. 17, 23.
Diagnosis: P1 element with an inset to reduced rostral lobe and reduced caudal lobe.
Description: The platform of the P1 element has a high dorso‐ventral to rostro‐caudal axis due to the poor development of accessory lobes. The platform is troughed in shape, with a medial groove marking the base of the trough. The platform is ornamented with transverse ridges that are bisected by a deep, well‐defined medial groove. The medial groove is widest at the termination of the medial carina and narrows dorsally. The dorsal margin of the platform is pointed to subrounded in shape. The caudal accessory lobe is reduced in shape and ornamented with discrete nodes. The rostral accessory lobe is inset to reduced in shape. Most of the ornamentation of the rostral lobe is centered on inflection point where the rostral adcarinal ridge joins with the rostral margin of the element. Typically two nodes ornament this region and the lobe thins out dorsally as ghost lobe. The adcarinal ridges are short, with the rostral adcarinal ridge terminating dorsally of the caudal adcarinal ridge. The caudal adcarinal ridge has a slight flare around the caudal lobe as it forms the margin separating the caudal lobe from the central platform. The rostral adcarinal ridge is short and terminates at the ventral margin of the rostral lobe where it aligns with the rostral margin of the platform. The medial carina is average in length and may have a few dribbling nodes dorsal of its terminus.
Discussion: Streptognathodus increbescens differs from S. elegantulus, S. gracilis, and S. sulcatus by its reduced rostral lobe. The species S. elegantulus, S. gracilis, and S. sulcatus do not have rostral lobes. Streptognathodus increbescens is differentiated from S. excelsus by its reduced rostral lobe instead of the more developed moderately restricted to expanded rostral lobe of S. excelsus.
Type Specimen: Figure 52.14 (BEG 20949) the holotype specimen of Stauffer and Plummer (1932) from the Gradford Formation, Dewey Sequence Equivalent. Illustrated Specimens: Figures 52.10 (TTU 08/193), 52. 12 (TTU 08/195), 52.15 (TTU 08/197), 52.16 (TTU 08/198), and 52.17 (TTU 08/199) from the Dewey Sequence. Figures 52.11 (TTU 08/194) and 52.19 (TTU 08/201) from the Hogshooter Sequence. Figures 52.13 (TTU 08/196) and 52.18 (TTU 08/200) from the Cherryvale Sequence.
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Occurrence: Streptognathodus increbescens first appears in the lag at the base of the Hogshooter Sequence. Specimens are recovered from the interval spanning the Hogshooter to Dewey sequences in the study interval.
STREPTOGNATHODUS SULCATUS Gunnell, 1933 Figures 51.1, 51.8, 51.9, 53.30. Streptognathodus sulcatus Gunnell, 1933, pl. 32, figs. 10; Barrick and Walsh, 1999, p. 157, figs. 8.2.
Diagnosis: P1 element with a low dorso‐ventral axis to rostro‐caudal axis ratio, no rostral lobe and a reduced caudal lobe.
Description: The platform of the P1 element has a very low dorso‐ventral to rostro‐caudal ratio due to shortening of the overall length of the platform. The platform is troughed and ornamented with coarse transverse ridges that are bisected by a well defined medial groove. The dorsal margin of the platform is rounded. A reduced caudal lobe is developed on the caudal margin of the element and ornamented by a single node in small specimens or a series of fused nodes in large specimens. The caudal adcarinal ridge merges with the ornamentation of the caudal lobe. The rostral margin does not have a rostral lobe, but will occasional have one node that marks the inflection point where the rostral adcarinal ridge merges with the rostral margin. The medial carina ranges from one‐quarter to one‐half the length of the platform.
Discussion: Streptognathodus sulcatus differs from all other species of Streptognathodus because of its low dorso‐ventral to rostro‐caudal ratio. It does not have a true rostral lobe which distinguishes it from S. excelsus and S. increbescens. The primary distinction between S. sulcatus and S. gracilis and S. elegantulus is on the basis of its low dorso‐ventral to rostro‐caudal ratio.
Type Specimen: Figure 51.9 (UM505‐3) the holotype specimen of Gunnell (1933) from the Wea Shale of the Cherryvale Sequence.
Illustrated Specimens: Figure 51.1 (TTU 08/162) from the Cherryvale Sequence. Figure 51.8 (TTU 08/169) from the Hogshooter Sequence.
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Occurrence: Streptognathodus sulcatus first appears in the lag at the base of the Hogshooter Sequence. Specimens are recovered from the interval spanning the Hogshooter to Cherryvale sequences in the study interval.
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EXPLANATION OF FIGURE 38 Position Page 1‐21 IDIOGNATHODUS EXPANSUS Stauffer and Plummer, 1932. All specimens shown at 50 X magnification.……………………………………………………………………… 120 1,2 Juvenile specimens from the Lost Branch Sequence (SUI 108209, SUI 10210) 1, 2 from South Sasakwa. 3‐7, Adult specimens from the Lost Branch Sequence (SUI 108211, 9‐20 SUI 108213, SUI 108216, SUI 108227, SUI 108226, SUI 108220, SUI108214, SUI 108215, SUI 108224, SUI 108221, SUI 108217, SUI 108212, SUI 108223, SUI 108225, SUI 108219, SUI 108222, SUI 108218). 3‐7, 9‐20 from South Sasakwa. 8 Cotype specimen from the East Mountain Formation (Lost Branch Sequence Equivalent) at Mineral Wells in Palo Pinto County, Texas (BEG 19163). 21 Cotype specimen from the East Mountain Formation (Lost Branch Sequence Equivalent) at Mineral Wells in Palo Pinto County, Texas (BEG 20928). Lectotype of Barrick and Walsh, 1999.
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EXPLANATION OF FIGURE 39 Position Page 1‐16 IDIOGNATHODUS SWADEI Rosscoe and Barrick, 2008. All specimens shown at 50 X magnification………………………………………………………………………...... 136 1‐4, 6 Juvenile and adult specimens from the Lost Branch Sequence (SUI 108228, SUI 108229, SUI 108231, SUI 108235, SUI 108231). 1‐4, 6 from South Sasakwa. 5, 8, 13 Adult specimens from the Hepler Sequence (SUI 108240, SUI 108241, SUI 108236). 5 from South Mound Reference; 8 from Type Checkerboard; 13 from Little California Creek. 7, 11, Adult specimens from the Swope Sequence (TTU08/001, 15 TTU08/002, TTU08/003). 7 from Fort Calhoun Quarry; 11, 15 from PWA Quarry. 9, 10, Adult specimens from the Hertha Sequence (SUI 108237, 16 SUI 108243, SUI 108238) 9, 16 from Uniontown; 10 from Tacket Mound I. 12 Holotype specimen from the Nuyaka Creek Shale from the Lost Branch Sequence from South Sasakwa at Sasakwa, Oklahoma (SUI 108233). 14 Adult specimen from the Shale Hill Sequence (SUI 108241). 14 from Uniontown.
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EXPLANATION OF FIGURE 40 Position Page 1, 6‐8 IDIOGNATHODUS HARKEYI (Gunnell, 1933). All specimens shown at 50 X magnification………………………………………………………………………...... 126 1 Adult specimen from the Hepler Sequence (SUI 108252). 1 from Little River. 6 Adult specimen from the Shale Hill Sequence (SUI 108246). 6 from Uniontown. 7 Holotype specimen of from the Hushpuckney Shale of the Swope Sequence (UM491‐3). 8 Adult specimen from the Hertha Sequence (SUI 108253). 8 from Uniontown.
2‐5, 9‐11 IDIOGNATHODUS SULCIFERUS Gunnell, 1933. All specimens shown at 50 X magnification...... 135 2 Adult specimen from the Shale Hill Sequence (SUI 108256). 2 from Section 75/71. 3, 5 Adult specimens from the Swope Sequence (TTU 08/004, TTU 08/005). 3 from Fort Calhoun Quarry; 5 from East of Peru. 4, 9 Adult specimens from the Hertha Sequence (SUI 108255, SUI 108257). 4, 9 from Tackett Mound I. 10 Adult specimen from the Shale Hill Sequence (SUI 108258). 10 from Kimball East. 11 Holotype specimen of Idiognathodus sulciferus from the Hushpuckney Shale of the Swope Sequence (UM492‐4).
12‐14 IDIOGNATHODUS FUSIFORMIS (Gunnell, 1933). All specimens shown at 50 X magnification...... 124 12 Adult specimen from the Hertha Sequence (SUI 108248). 12 from Uniontown. 13 Adult specimen from the Shale Hill Sequence (SUI 108250). 13 from Uniontown. 14 Holotype specimen of Idiognathodus fusiformis from the Hushpuckney Shale of the Swope Sequence (UM499‐2).
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EXPLANATION OF FIGURE 41 Position Page 1‐13 IDIOGNATHODUS TURBATUS Rosscoe and Barrick, 2008. All specimens shown at 50 X magnification.………………………………………………………………………. 140 1, 3, 5, Adult specimens from the Hertha Sequence (SUI 108268, 7, 10, SUI 108271, SUI 108265, SUI 108270, SUI 108264, SUI 108267, 12, 13 SUI 108272). 1, 10 from Tacket Mound I; 3, 5, 7, 10, 12, 13 from Uniontown. 2, 11 Adult specimens from the Shale Hill Sequence (SUI 108260, SUI108263). 2, 11 from US 69 Outcrops. 4 Transitional form between Idiognathodus turbatus and Idiognathodus swadei from the Hepler Sequence (SUI 108262). 4 from Little California Creek. 6, 8 Adult specimens from the Swope Sequence (TTU08/005, TTU08/006). 6 from PWA Quarry; 8 from East of Peru. 9 Holotype specimen of Idiognathodus turbatus from the black facies of the Mound City Shale from the Hertha Sequence from Uniontown at Uniontown, Kansas (SUI 108266).
14 IDIOGNATHODUS SAGITTALIS Kozitskaya, 1978 from Limestone 01 in Kalinovkoe, Ukraine. Holotype specimen at 50 X magnification (68‐3039)..... 56
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EXPLANATION OF FIGURE 42 Position Page 1, 2, 8 IDIOGNATHODUS SPECIES 1. All specimens shown at 50 X magnification.…… 142 1, 2, 8 Adult specimens from the Hertha Sequence (SUI 108275, SUI 108279, SUI 108278). 1, 8 from Tackett Mound I; 2 from Uniontown.
3, 5, 9‐ IDIOGNATHODUS ECCENTRICUS Ellison, 1941. All specimens shown at 50 X 11, 14, 15 magnification...... 119 3, 10 Adult specimens from the Swope Sequence (TTU08/007, TTU08/010). 3 from PWA Quarry; 10 from Fort Calhoun Quarry. 5 Adult specimen from the Hertha Sequence (SUI 108283). 5 from Uniontown. 9, 11, Adult specimens from the Shale Hill Sequence (SUI 108284, SUI 14 108285, SUI 108287). 9 from US 69 Outcrops; 11 from Little California Creek; 14 from Uniontown. 15 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UMC560‐1).
4, 6, 7, IDIOGNATHODUS VORAX Rosscoe and Barrick 2008. All specimens shown 12, 13 at 50 X magnification...... 141 4, 7 Adult specimens from the Swope Sequence (TTU08/008, TTU08/009). 4 from Fort Calhoun Quarry; 7 from PWA Quarry. 6, 13 Adult specimens from the Hertha Sequence (SUI 108277, SUI 108276). 6, 13 from Tackett Mound I. 12 Holotype specimen of Idiognathodus vorax from the gray facies of the Mound City Shale of the Hertha Sequence from Uniontown at Uniontown, Kansas (SUI 108274).
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EXPLANATION OF FIGURE 43 Position Page 1, 2, 5, 6, IDIOGNATHODUS CANCELLOSUS (Gunnell, 1933). All specimens shown at 8‐10, 12, 50 X magnification.……………………………………………………………………………………… 110 13 1, 5, 6, Adult specimens from the Dennis Sequence (TTU 08/011, 13 TTU 08/012, TTU 08/013, TTU 08/022). 1, 5 from Jingo 69; 6 from Ramona Railroad Crossing; 13 from Shirk. 2, 8‐10 Adult specimens from the Swope Sequence (TTU 08/014, TTU 08/018, TTU 08/019, TTU 08/020). 2 from Jingo 69; 8‐10 from Clear Creek. 12 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UM491‐2).
3, 4, 7, IDIOGNATHODUS AFF. CANCELLOSUS (Gunnell, 1933). All specimens shown 11, 14 at 50 X magnification.………………………………………………………………………………… 112 3, 4, 7, Adult specimens from the Swope Sequence (TTU 08/015, 11 TTU 08/016, TTU 08/017, TTU 08/021). 3 from Clear Creek; 4, 7 , 11 from Jingo 69. 14 Adult specimens from the Dennis Sequence (TTU 08/023). 14 from Ramona Railroad Crossing.
15‐21 IDIOGNATHODUS BILIRATUS (Gunnell, 1933). All specimens shown 50 X magnification.…………………………………………………………...... 108 15, 17, Adult specimens from the Dennis Sequence (TTU 08/024, 19 TTU 08/025, TTU 08/026). 15 from Shirk; 17, 19 from Ramona Railroad Crossing. 16, 18, Adult specimens from the Swope Sequence (TTU 08/027, 20, 21 TTU 08/028, TTU 08/029, TTU 08/030). 16, 20 from Jingo 69; 18, 21 from Clear Creek.
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EXPLANATION OF FIGURE 44 Position Page 1‐8, 13 IDIOGNATHODUS FOLIUM Gunnell, 1933. All specimens shown at 50 X magnification.………………………………………………………………………...... 122 1, 6 Adult specimens from the Hertha Sequence (TTU 08/031, TTU 08/035). 1, 6 from Uniontown. 2 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UM496‐1). 3‐5, 7, Adult specimens from the Swope Sequence (TTU 08/032, 8, 13 TTU 08/033, TTU 08/034, TTU 08/036, TTU 08/037, TTU 08/041). 3 from Jingo 69; 4, 7 from East of Peru; 5, 8 from Clear Creek, 13 from PWA Quarry.
9‐12, IDIOGNATHODUS SICULUS Gunnell, 1933. All specimens shown at 50 X 14‐16 magnification.……………………………………………………...... 134 9 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UM492‐2). 10‐12, Adult specimens from the Swope Sequence (TTU 08/038, 14 TTU 08/039, TTU 08/040, TTU 08/042). 10 from Clear Creek; 11, 14 from Fort Calhoun Quarry; 12 from Jingo 69. 15 Adult specimen from the Shale Hill Sequence (TTU 08/043). 15 from Uniontown. 16 Adult specimen from the Dennis Sequence (TTU 08/044). 16 from Ramona Railroad Crossing.
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EXPLANATION OF FIGURE 45
Position Page 1‐4, 6 IDIOGNATHODUS CHERRYVALENSIS Gunnell, 1933. All specimens shown at 50 X magnification.………………………………………………………………………..……………. 113 1‐4, 6 Adult specimens from the Dennis Sequence (TTU 08/045, TTU 08/046, TTU 08/047, TTU 08/048, TTU 08/049). 1 from Shirk; 2, 4, 6 from Ramona Railroad Crossing; 3 from Hogshooter South.
5, 7‐15 IDIOGNATHODUS CONFRAGUS Gunnell, 1933. All specimens shown at 50 X magnification.………………………………………………………………………………………...... 116 5, 7, 8, Adult specimens from the Swope Sequence (TTU 08/049, 10‐12 TTU 08/051, TTU 08/052, TTU 08/054, TTU 08/055, TTU 08/056). 5, 7, 8, 10, 12 from Jingo 69; 11 from Clear Creek. 9, 13, Adult specimens from the Dennis Sequence (TTU 08/053, 15 TTU 08/057, TTU08/058). 9, 15 from Hogshooter South; 13 from Ramona Railroad Crossing. 14 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UM498‐1).
16‐23 IDIOGNATHODUS LOBATUS Gunnell, 1933. All specimens shown 50 X magnification.………………………………………………………………………………………………. 128 16, 17, Adult specimens from the Swope Sequence ( TTU 08/060, 19‐23 TTU 08/061, TTU 08/062, TTU 08/063, TTU 08/064, TTU 08/065, TTU 08/066). 17, 19, 21‐23 from Jingo 69; 16 from Clear Creek; 21 from Fort Calhoun Quarry. 18 Holotype specimen from Hushpuckney Shale of the Swope Sequence (UM492‐5).
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EXPLANATION OF FIGURE 46
Position Page 1‐8 IDIOGNATHODUS CLAVATULUS (Gunnell, 1933). All specimens shown at 50 X magnification.………………………………………………………………………..…………….. 115 1‐3, Adult specimens from the Swope Sequence (TTU 08/067, 5‐8 TTU 08/068, TTU 08/069, TTU 08/070, TTU 08/071, TTU 08/072, TTU 08/073). 1, 8 from Jingo 69; 2, 3, 6 from East of Peru; 5 from PWA Quarry; 7 from Fort Calhoun Quarry. 4 Holotype specimen from the Hushpuckney Shale of the Swope Sequence (UM493‐2).
9‐12 IDIOGNATHODUS SPECIES 2 All specimens shown at 50 X magnification...... 144 9‐12 Adult specimens from the Mound Valley Sequence (TTU 08/074, TTU 08/075, TTU 08/076, TTU 08/077). 9‐12 from Coffeyville Southwest.
13‐26 IDIOGNATHODUS CORRUGATUS Gunnell, 1933. All specimens shown at 50 X 117 magnification...... 13 Adult specimen from the Hogshooter Sequence (TTU 08/078). 13 from Zink Ranch. 14 Holotype specimen from the Wea Shale of the Cherryvale Sequence (UM504‐5). 15 Adult specimen from the Cherryvale Sequence (TTU 08/079). 15 from New Harmony. 16 Adult specimen from the Dewey Sequence (TTU 08/080). 16 from Fort Calhoun Quarry. 17, 23, Adult specimens from the Swope Sequence (TTU 08/081, 24 TTU 08/087, TTU 08/088). 17, 23, 24 from Jingo 69. 18, 19, Adult specimens from the Mound Valley Sequence (TTU 08/82, 25, 26 TTU 08/83, TTU 08/89, TTU 08/90). 18, 19, 25, 26 from Coffeyville Southwest. 20‐22 Adult specimens from the Dennis Sequence (TTU08/084, TTU 08/085, TTU 08/086). 20 from Ramona Railroad Crossing; 21, 22 from Hogshooter South.
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EXPLANATION OF FIGURE 47
Position Page 1‐7 IDIOGNATHODUS SPECIES 3. All specimens shown at 50 X magnification.……. 145 1, 5 Adult specimens from the Swope Sequence (TTU 08/091, TTU 08/096). 1 from Jingo 69; 5 from PWA Quarry. 2 Adult specimen from the Hogshooter Sequence (TTU 08/092). 2 from Zink Ranch. 6 Adult specimen from the Mound Valley Sequence (TTU 08/097). 6 from Coffeyville Southwest. 3, 4 Adult specimens from the Dennis Sequence (TTU 08/094, TTU 08/095). 3 from Ramona Railroad Crossing, 4 from Jingo 69.
7‐19 IDIOGNATHODUS FUSIFORMIS. All specimens shown at 50 X magnification… 124 7‐10, Adult specimens from the Dennis Sequence (TTU 08/098, 13, 14, TTU 08/099, TTU 08/100, TTU08/103, TTU 08/107, TTU 08/106, 16, 17, TTU 08/109, TTU 08/104, TTU 08/111). 7, 8, 13, 17, 19 from Jingo 19 69; 9, 16 from Ramona Railroad Crossing; 10 from Fort Calhoun Quarry; 14 from Shirk. 11, 12 Adult specimens from the Mound Valley Sequence (TTU 08/101, TTU 08/102). 11, 12 from Coffeyville Southwest. 15 Adult specimen from the Dewey Sequence (TTU 08/161). 15 from Fort Calhoun Quarry. 18 Adult specimen from the Cherryvale Sequence (TTU 08/110). 18 from Hogshooter Quarry South Pit.
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EXPLANATION OF FIGURE 48
Position Page 1‐4, 8‐11, IDIOGNATHODUS CHERRYVALENSIS Gunnell, 1933. All specimens shown at 14, 17 50 X magnification.………………………………………………………………………..……………. 113 1‐4, 10, Adult specimens from the Dewey Sequence (TTU 08/112, 14, 17 TTU 08/113, TTU 08/114, TTU 08/115, TTU 08/121, TTU 08/124, TTU 08/ 127). 1‐3, 11 from KAW Drive; 4, 14, 17 from Fort Calhoun Quarry. 11 Holotype specimen from the Wea Shale of the Cherryvale Sequence (UM504‐4). 8, 9 Adult specimens from the Cherryvale Sequence (TTU 08/119, TTU 08/120). 8 from Hogshooter Quarry South East Pit; 9 from New Harmony Type.
5‐7 IDIOGNATHODUS MULTINODOSUS Gunnell, 1933. All specimens shown at 50 X magnification.……………………………………………………………………………………… 132 5 Holotype specimen from the Quivira Shale of the Dewey Sequence (UM513‐3). 6, 7 Adult specimens from the Dewey Sequence (TTU 08/117, TTU08/119). 6, 7 from KAW Drive.
12, 13, 15, IDIOGNATHODUS SYMMETRICUS Gunnell, 1933. All specimens shown 50 X 16, 18‐23 magnification.………………………………………………………………………………………………. 138 12, 13, Adult specimens from the Dewey Sequence (TTU 08/122, 15, 19, TTU 08/123, TTU 08/125, TTU 08/129, TTU 08/130, TTU 08/131, 21‐23 TTU 08/132). 12, 13, 15, 19, 21 from Fort Calhoun Quarry; 22, 23 from KAW Drive. 16, 18 Adult specimens from the Cherryvale Sequence (TTU 08/126, TTU 08/128). 16 from Zink Ranch; 18 from Bannister Road. 20 Holotype specimen from Wea Shale of the Cherryvale Sequence (UM504‐2).
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EXPLANATION OF FIGURE 49
Position Page 1‐3 IDIOGNATHODUS FOLIUM Gunnell, 1933. All specimens shown at 50 X magnification.……...... 122 1‐3 Adult specimens from the Dennis Sequence (TTU 08/133, TTU 08/134, TTU 08/135). 1‐3 from Jingo 69.
4‐15 IDIOGNATHODUS MAGNIFICUS Gunnell, 1933. All specimens shown at 50 X magnification...... 129 4 Adult specimen from the Dennis Sequence (TTU 08/136). 4 from Ramona Railroad Crossing. 5, 6, 10 Adult specimens from the Hogshooter Sequence (TTU 08/137, TTU 08/138, TTU 08/141). 5 from East of Ochelata; 6 from Zink Ranch; 10 from Hogshooter South. 7, 9, Adult specimens from the Dewey Sequence (TTU 08/139, 12‐15 TTU 08/140, TTU 08/142, TTU 08/143, TTU 08/144, TTU 08/145, TTU 08/146). 7, 9, 13‐15 from Fort Calhoun Quarry; 11 from Skiatook Dam; 12 from Kaw Drive. 8 Holotype specimen of Idiognathodus kansensis Gunnell, 1933, from the Quivira Shale of the Dewey Sequence (UM513‐4). Now recognized as the sinistral element of Idiognathodus magnificus. 11 Cotype specimen Idiognathodus magnificus of Stauffer and Plummer, 1932.
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EXPLANATION OF FIGURE 50 Position Page 1‐7, 9 IDIOGNATHODUS MAGNIFICUS Stauffer and Plummer, 1932. All specimens shown at 50 X magnification.……...... 129 1, 5‐7 Adult specimens from the Dennis Sequence (TTU 08/147, TTU 08/151, TTU 08/152, TTU 08/153). 1, 5, 7 from Jingo 69; 6 from Shirk. 2 Adult specimen from the Dewey Sequence (TTU 08/148). 2 from Fort Calhoun Quarry. 3 Adult specimen from the Cherryvale Sequence (TTU 08/149). 3 from New Harmony. 4 Adult specimen from the Hogshooter Sequence (TTU 08/150). 4 from East of Ochelata. 9 Holotype specimen from the Wolf Mountain Shale of the Gradford Formation (Dewey Sequence Equivalent) at the Bridgeport Brick Plant in Wiles County, Texas (BEG19164).
8, 10‐16 IDIOGNATHODUS SPECIES 4. All specimens shown at 50 X magnification...... 146 8, 10, Adult specimens from the Dennis Sequence (TTU 08/154, 12 TTU 08/155, TTU 08/157). 8, 10, 12 from Jingo 69. 11, 16 Adult specimens from the Dewey Sequence (TTU 08/156, TTU 08/160). 11, 16 from Fort Calhoun Quarry. 13, 14 Adult specimens from the Hogshooter Sequence (TTU 08/158, TTU 08/159). 13 from East of Ochelata; 14 from Hogshooter South. 15 Adult specimen from the Mound Valley Sequence (TTU 08/093). 15 from Coffeyville Southwest.
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EXPLANATION OF FIGURE 51
Position Page 1, 8, 9 STREPTOGNATHODUS SULCATUS Gunnell, 1933. All specimens shown at 50 X magnification.………………………………………………………………………..……………...... 154 1 Adult specimen from the Cherryvale Sequence (TTU 08/162). 1 from New Harmony Type. 8 Adult specimen from the Hogshooter Sequence (TTU 08/169). 8 from Ramona Railroad Crossing. 9 Holotype specimen from the Wea Shale of the Cherryvale Sequence (UM505‐3).
2‐5, 13, STREPTOGNATHODUS ELEGANTULUS Stauffer and Plummer, 1932. All 25, 26 specimens shown at 50 X magnification.……………………………………………………... 149 2, 4, 25 Adult specimens from the Cherryvale Sequence (TTU 08/163, TTU 08/165, TTU 08/183). 2 from New Harmony Type; 4 from Bannister Road; 25 from Drum Reference. 3 Adult specimens from the Hogshooter Sequence (TTU 08/164). 3 from Ramona Railroad Crossing. 5, 26 Adult specimens from the Dewey Sequence (TTU 08/166, TTU 08/184). 5 from KAW Drive; 26 from Fort Calhoun Quarry. 13 Holotype specimen from the Wolf Mountain Shale of the Gradford Formation (Dewey Sequence Equivalent) at the Bridgeport Brick Plant in Wiles County, Texas (BEG19166)
6, 7, 10‐ STREPTOGNATHODUS GRACILIS Stauffer and Plummer, 1932. All specimens 12, 14‐24 shown 50 X magnification.…………………………………………………………………………… 151 6, 16, Adult specimens from the Cherryvale Sequence (TTU 08/167, 20‐23 TTU 08/174, TTU 08/178, TTU 08/179, TTU 08/180, TTU 08/181). 6, 16, 20, 23 from Bannister Road; 21, 22 from Zink Ranch. 7, 10‐ Adult specimens from the Hogshooter Sequence (TTU 08/168, 12, 17 TTU 08/170, TTU 08/171, TTU 08/172, TTU 08/175). 7 from East of Ochelata 75; 10, 12 from Zink Ranch; 11 from Hogshooter South; 17 from Ramona Railroad Crossing. 15 Holotype specimen from the PP3 Shale Member of the Posideon Formation (Cherryvale Sequence equivalent) at the abandoned “Wiles” railroad stop in Stephens County, Texas (BEG19169). 19, 24 Adult specimens from the Dewey Sequence (TTU 08/177, TTU 08/182). 19 from KAW Drive; 24 from Skiatook Dam.
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EXPLANATION OF FIGURE 52
Position Page 1‐9 STREPTOGNATHODUS EXCELSUS Stauffer and Plummer, 1932. All specimens shown at 50 X magnification.……………………………………………………………………….. 148 1, 2, Adult specimens from the Hogshooter Sequence (TTU 08/185, 5, 9 TTU 08/186, TTU 08/189, TTU 08/192). 1 from Ramona Railroad Crossing; 2 from East of Ochelata 75; 5 from Zink Ranch; 9 from Hogshooter Quarry North Pit. 3, 4, 8 Adult specimens from the Cherryvale Sequence (TTU 08/187, TTU 08/188, TTU 08/191). 3, 4 from New Harmony Type; 8 from Hogshooter Quarry Southeast Pit. 6 Holotype specimen from the Wolf Mountain Shale of the Gradford Formation (Dewey Sequence Equivalent) at the Bridgeport Brick Plant in Wiles County, Texas (BEG19168) 7 Adult specimen from the Dewey Sequence (TTU 08/190). 7 from Fort Calhoun Quarry.
10‐19 STREPTOGNATHODUS INCREBESCENS Stauffer and Plummer, 1932. All specimens shown at 50 X magnification.……………………………………………………... 152 10, 12, Adult specimens from the Dewey Sequence (TTU 08/193, 15‐17 TTU 08/195, TTU 08/197, TTU 08/198, TTU 08/199). 10, 15‐17 from Fort Calhoun Quarry; 12 from Skiatook Dam. 11, 19 Adult specimens from the Hogshooter Sequence (TTU 08/ 194, TTU 08/201). 11, 19 from Hogshooter South. 13, 18 Adult specimens from the Cherryvale Sequence (TTU 08/196, TTU 08/200). 13, 18 from Bannister Road. 14 Holotype specimen from the Wolf Mountain Shale of the Gradford Formation (Dewey Sequence Equivalent) at the Bridgeport Brick Plant in Wiles County, Texas (BEG20949).
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EXPLANATION OF FIGURE 53
Dorsal views of selected P1 elements of Idiognathodus and Streptognathodus from the study interval. All specimens are shown at 50X magnification and have been illustrated from the oral viewpoint on previous plates. 1. Idiognathodus expansus Stauffer and Plummer, 1932 (SUI 108225). 2 – 4. Idiognathodus swadei Rosscoe and Barrick, 2008 (SUI 108233, TTU 08/002, TTU 08/003). 5. Idiognathodus corrugatus Gunnell, 1933 (TTU 08/080). 6. Idiognathodus species 3 n. sp. (TTU 08/096). 7. Idiognathodus sulciferus Gunnell, 1933 (SUI 108257). 8. Idiognathodus harkeyi Gunnell, 1933 (SUI 108253). 9. Idiognathodus fusiformis Gunnell, 1933 (SUI 108248). 10. Idiognathodus eccentricus (Ellison, 1942) (SUI 108283). 11. Idiognathodus siculus Gunnell, 1933 (TTU 08/044). 12. Idiognathodus turbatus Rosscoe and Barrick, 2008 (SUI 108266). 13. Idiognathodus species 1 Rosscoe and Barrick, 2008 (SUI 108279). 14. Idiognathodus vorax Rosscoe and Barrick, 2008 (SUI 108274). 15. Idiognathodus clavatulus Gunnell, 1933 (TTU 08/069). 16. Idiognathodus lobatus Gunnell, 1933 (TTU 08/064). 17. Idiognathodus confragus Gunnell, 1933 (TTU 08/051). 18. Idiognathodus cherryvalensis Gunnell, 1933 (TTU 08/120). 19. Idiognathodus folium Gunnell, 1933 (TTU 08/041). 20. Idiognathodus species 2 n. sp. (TTU 08/076). 21. Idiognathodus species 4 n. sp. (TTU 08/159). 22, 23. Idiognathodus magnificus Stauffer and Plummer, 1932 (TTU 08/139, TTU 08/147). 24. Idiognathodus symmetricus Gunnell, 1933 (TTU 08/132). 25. Idiognathodus multinodosus Gunnell, 1933 (TTU 08/116). 26, 27. Idiognathodus biliratus Gunnell, 1933 (TTU 08/028, TTU 08/029) 28, 29. Idiognathodus cancellosus (Gunnell, 1933) (TTU 08/011, TTU 08/020). 30. Streptognathodus sulcatus Gunnell, 1933 (TTU 08/162). 31, 32. Streptognathodus gracilis Stauffer and Plummer, 1932 (TTU 08/174, TTU 08/182). 33, 34. Streptognathodus elegantulus Stauffer and Plummer, 1932 (TTU 08/184, TTU 08/164). 35, 36. Streptognathodus excelsus Stauffer and Plummer, 1932 (TTU 08/187, TTU 08/190). 37. Streptognathodus increbescens Stauffer and Plummer, 1932 (TTU 08/199).
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APPENDIX C HYDROGEN PEROXIDE METHOD FOR THE BREAKDOWN OF BLACK SHALES
The following method is for breaking down organic rich shales and can be used to remove organic material from other preprocessed residues. The method involves an exothermic reaction, generates high pressures, splashes hot liquids, and yields fumes (and smoke) that may be extremely unhealthy. For the best and safest results use multiple containment vessels (which need to be vented) and allow the reaction to occur in an operational fume hood. At no time have we tested the fumes released by this reaction. Carbon dioxide gas and water vapor are the most likely fumes, but other harmful chemical oxides may also be released.
Equipment and Supplies 1 – Large Reaction Vessel (13 gallon plastic garbage bin with snap on top) 1 – Small Reaction Vessel (10 liter plastic bucket) 1 – Free Floating Lid (Should be heavy plastic to cover the small vessel, 5 gallon bucket lids work) 1 – 1000 ml Beaker 35% Hydrogen Peroxide (Technical Grade) Protective Gloves Protective Eyewear Fume Hood Sink Sorting Sieves
General Method It is best to work with small sample and peroxide amounts to make containment of the reaction easier. In most cases, if black shale is productive a small sample size will provide more than enough specimens to be representative. Each black shale, gray shale, or organic residue has its own unique geochemistry. Some samples will react ideally, others will not. This general method works on most shale. Figure 53 shows the flow chart I use to determine how to go about processing samples of varying reaction style and varying reaction residues.
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Hydrogen Peroxide Processing: Step by Step Methodology
1. Break up sample into 250 gram portions composed of chips around 4‐6 centimeters in diameter (sample does not need to be dry).
2. Place sample in the bottom of the small reaction vessel, spread out to maximize the surface area of the sample on the base of the bucket.
3. Add 2000 ml of 35% technical grade hydrogen peroxide (1000 ml at a time) to the sample inside the bucket (wear protective gloves and eyewear). If, after adding the first 1000 ml, a smoking or boiling reaction begins continue with the procedure without adding the second 1000 ml.
4. Place the small reaction vessel inside of the large reaction vessel.
5. Cover the small reaction vessel with the heavy plastic lid. This lid should be free to move, allowing the efficient release of pressure and helping to contain boil‐over and spray.
6. Cover the large reaction vessel with the snap down lid. This lid should be perforated with 1/8 inch holes to allow the release of smoke, steam, and pressure without allowing for the escape of boil‐over and spray.
7. The whole apparatus should be placed in a fume hood for the duration of the reaction (See Reaction Observations).
8. Once the reaction is complete and has cooled to a safe temperature rinse the residue and evaluate for further processing (See Figure 54).
9. Once the sample is completely processed, dry and pick for conodonts as you would any sample.
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Reaction Observations • Temperatures get high enough to make most plastics loosen. A temperature recorded during experimentation peaked at 87°C. • The speed of the reaction and success of the reaction varies for every shale. Some will completely breakdown in an explosive reaction in less than thirty minutes, others will never smoke and take several days before the reaction ceases. • Deep marine black shales. The more fissile a sample the longer it will take to breakdown. Because of the high organic content these reactions are commonly hot, smoky, and splash hot fluids. • Marine dark gray shales. Most dark gray shales will breakdown with the first reaction. These are usually very smoky, but splash less material than the deep marine black shales. • Nearshore black shales and coals. The organics bound in these rocks do not respond to hydrogen peroxide as readily as in deep marine shales. The reaction discolors the water to black, bubbles slowly at low temperature and takes a very long time to break down. • Phosphate nodules will not process, but they are commonly found with organics that break down readily in hydrogen peroxide. • Glauconitic samples breakdown into glauconite and deflocculated clay with a smoky, but not explosive reaction. • Samples with abundant un‐oxidized metals (especially sulfides) react violently to hydrogen peroxide processing. These reactions usually involve very high temperatures, smoke (usually red, orange, or yellow in color), explosive releases of energy (usually cannot be contained), and the release of dangerous, choking fumes.
NOTE: The containment vessels described are not guaranteed to contain every reaction. This method should be used at your own risk. Take extreme care in using this procedure and do not use this procedure if you are at all unsure of whether you can effectively contain and control the reaction.
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Preprocessed Residue Gray/Dark Gray Shale Black Shale
High Nearshore Quartz-Rich Near Shore Off Shore Metal Content Organics Soak in Bleach Peroxide (1 Week) Processing Soak in Bleach Heavy Mineral Peroxide (1 Week) Separation Processing
Repeat (as necessary) Soak in Bleach Peroxide Repeat Twice
(1 Week) , University, Tech Texas Processing (if necessary) 191
Large Clay Carbonate Organics Organic Free Repeat Residue Residue Residue Small Remain Residue (as necessary) Heavy Mineral Kerosene Formic Acid Residue Separation Processing Processing
Large Clay Carbonate 2008 August Rosscoe J. Steven Residue Residue Residue Small Residue Heavy Mineral Kerosene Formic Acid Separation Processing Processing
Pick Conodonts Pick Conodonts Pick Conodonts
Figure 54: Flow chart showing the processing of materials using the hydrogen peroxide breakdown method. The high degree of geochemical variability in samples leads to a diverse number of reactions and pathways to getting to an acceptable sample for picking.