Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha)

Home , Aerosaurus, Anthracosauria, Archeria (animal), Arroyo Formation, Cardiocephalus, Carrolla

Richard Kissel

A thesis submitted in conformity with the requirements for the degree of doctor of philosophy Graduate Department of Ecology & Evolutionary Biology University of Toronto

Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha)

Richard Kissel

Doctor of Philosophy

Graduate Department of Ecology & Evolutionary Biology University of Toronto

2010 Abstract

Based on dental, cranial, and postcranial anatomy, members of the Permo-Carboniferous clade

Diadectidae are generally regarded as the earliest tetrapods capable of processing high-fiber plant material; presented here is a review of diadectid morphology, phylogeny, taxonomy, and paleozoogeography. Phylogenetic analyses support the monophyly of Diadectidae within

Diadectomorpha, the sister-group to Amniota, with Limnoscelis as the sister-taxon to Tseajaia +

Diadectidae. Analysis of diadectid interrelationships of all known taxa for which adequate specimens and information are known—the first of its kind conducted—positions Ambedus pusillus as the sister-taxon to all other forms, with Diadectes sanmiguelensis, Orobates pabsti,

Desmatodon hesperis, Diadectes absitus, and (Diadectes sideropelicus + Diadectes tenuitectes +

Diasparactus zenos) representing progressively more derived taxa in a series of nested clades. In light of these results, it is recommended herein that the species Diadectes sanmiguelensis be referred to the new genus Oradectes, Diadectes absitus be referred to the new genus Silvadectes, and Diasparactus be synonymized with Diadectes to produce Diadectes zenos. The phylogenetic hypothesis also reveals an evolutionary history leading to more efficient oral processing within the lineage, with successive nodes characterized by features indicative of a high-fiber diet. Within Diadectomorpha, diadectids constitute the majority of the species, ii suggesting that the advent of herbivory resulted in a relatively rapid radiation of species within the group, producing a clade that is markedly more species-rich than other, non-herbivorous diadectomorph taxa. An extensive review of Permo-Carboniferous tetrapod-bearing localities does, however, indicate that diadectids were not a key component of the fauna, discovered at fewer than 50 percent of the sites reviewed. These results counter suggestions that the evolution of Diadectidae led to the formation of the modern terrestrial ecosystem—where a large crop of herbivores supports a much smaller number of carnivores—during the Late Carboniferous and

Early Permian.

iii

Acknowledgments

I would like to thank my thesis committee chairperson, Dr. Robert Reisz, for his guidance, encouragement, and continued support of this project and my career. Words simply cannot express the gratitude that I will forever hold. I also wish to extend thanks to the members of my final exam committee, Drs. David Evans, Hans-Dieter Sues, Denis Walsh, and Rick Winterbottom. For her patience, teaching, and continual smile, a special thanks is offered to Ms. Diane Scott.

For the loan of specimens critical to this study, I thank: Bill Amaral and Charles Schaff (Museum of Comparative Anatomy, Cambridge); Victoria Byre and Jeff Person (Sam Noble Oklahoma Museum of Natural History, Norman); Greg Gunnell (Museum of Paleontology, Ann Arbor); Brian Iwama and Kevin Seymour (Royal Ontario Museum, Toronto); Amy Henrici (Carnegie Museum of Natural History, Pittsburgh); and William Simpson (Field Museum of Natural History, Chicago). And for many discussions of diadectid anatomy, I thank Dr. David Berman of the Carnegie Museum.

Finally, I thank those beautiful few that have have offered their love and support throughout not only this study but throughout my life. Thank you.

Table of Contents

Abstract ii

Acknowledgments iv

List of Tables viii

List of Figures ix

List of Appendices xv

Chapter 1 Introduction and Historical Background 1

Chapter 2 Description of a New Diadected from the Lower Permian of Ohio 6

1 Introduction 6

2 Description and Comparison 8

2.1 Introduction 8

2.2 Maxilla 9

2.3 Dentary 14

2.4 Ambedus pusillus and diadectid ontogeny 18

2.5 Conclusions 19

Chapter 3 Phylogeny of Diadectidae 25

3 Introduction 25

4 Excluded Taxa 26

5 Monophyly of Diadectidae 29

5.1 Revisiting Diadectomorpha as the sister-taxon to Amniota 32

6 Interrelationships of Diadectidae 35

6.1 Taxonomic Implications 39

7 Conclusions 42

Chapter 4 Systematic Revision 69

8 Diadectidae Cope 1880a 69

8.1 Ambedus Kissel and Reisz 2004, p. 198 70

8.2 Orobates Berman et al. 2004, p. 3 71

8.3 Oradectes n. gen. 72

8.4 Desmatodon Case, 1908, p. 236 74

8.5 Silvadectes n. gen. 76

8.6 Diadectes Cope 1878a, p. 505 78

8.7 Problematic Taxa Assigned to Diadectidae 82

Chapter 5 Evolution of Diadectidae 91

9 Introduction 91

10 Evolutionary Radiation of Diadectidae 92

11 Evolutionary Trends within Diadectidae 94

Chapter 6 Stratigraphic and Geographic Distribution of P-C Tetrapods 99

12 Introduction 99

13 Permo-Carboniferous Tetrapod-bearing Localities 101

13.1 Missourian 102

13.2 Virgilian 106

13.3 Wolfcampian 113

13.4 Leonardian 127

14 Results and Conclusions 143

References 156

Appendix 1 169

Appendix 2 173

Appendix 3 177

Appendix 4 181

vii

List of Tables

Table 1. Maximum crown measurements (in mm) and ratios of largest preserved, midseries maxillary cheek teeth in selected specimens of Diadectes, Desmatodon, Orobates, and Ambedus. Modified from Berman and Sumida (1995).

Table 2. Maximum crown measurements (in mm) and ratios of largest preserved, midseries dentary cheek teeth in selected specimens of Diadedectes, Diasparactus, Desmatodon, Orobates, and Ambedus. Modified from Berman and Sumida (1995) and Kissel and Lehman (2002).

Table 3. Missourian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Table 4. Virgilian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Table 5. Wolfcampian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Table 6. Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

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List of Figures

Fig. 1. MCZ 9436, right maxilla and holotype of Ambedus pusillus in lateral (A), occlusal (B), and medial (C) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 2. Fifth posteriormost maxillary tooth of MCZ 9436 (A) and fifth posteriormost dentary tooth of MCZ 9440 (B) in posterior view. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 3. MCZ 9438, complete left dentary of Ambedus pusillus in lateral view. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 4. MCZ 9439, right dentary of Ambedus pusillus in lateral (A) and medial (B) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 5. MCZ 9440, left dentary of Ambedus pusillus in lateral (A) and occlusal (B) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 6. OMNH 56871, articulated left frontal and postfrontal in dorsal view (A), OMNH 56872a (B) and OMNH 56873 (C), premaxillary incisor teeth in lingual and lateral views, and OMNH 56875 (D) and OMNH 56872b (E) in probable posterior, anterior, and lingual views. From Reisz and Sutherland (2001). Scale = 1 cm.

Fig. 7. Articulated series of four presacral and two sacral vertebrae of Phanerosaurus naumanni, the sole specimen assigned to the form, in left lateral (top) and dorsal (bottom) views. From Meyer (1860; no scale provided).

Fig. 8. Partial left lower jaw in medial view (A), partial right dentary in medial view (B), right maxilla in lateral view (C), and vertebrae (D) of Stephanospondylus pugnax; MNG 14000, a partial skull of Orobates pabsti in lateral view (E). B from Stappenbeck (1905; no scale provided); C-D from Geinitz and Deichmüller (1882; no scale provided); scale for E = 1 cm.

11(1), 24(1); Node B (Diadectomorpha): 2(1), 4(1), 18(1), 25(1), 26(1), 32(1), 36(1), 37(1); Node C: 3(1), 8(1); Node D (Diadectidae): 27(1), 30(1), 31(1); Node E: 22(1), 26(2), 28(1); Node F: 12(1); 20(1); Node G: 19(1), 22(2), 30(2), 31(2). Bootstrap and decay index values determined in Paup 4.0b10 are: Node B: 97, 4; Node C: 56, 1; Node D: 96, 3; Node E: 95, 3; Node F: 95, 3; Node G: 92, 3.

Fig. 10. CM 1938, holotype and only known specimen (a partial left maxilla) of Desmatodon hollandi in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm.

Fig. 11. Skull (palatal view; A) and right lower jaw of Diadectes lentus in occlusal (B), medial (C), and lateral (D) views. Scale = 1 cm. Ang, angular; s.ang, surangular; art, articular; p.art, prearticular; d, dentary; spl, splenial; ant fenestra, anterior fenestra; med fenestra, medial fenestra; post fenestra, posterior fenestra; numbers indicate tooth positions. A and B from Case and Williston (1912); C-E from Welles (1941).

Fig. 12. YPM 817, partial skull of Diadectes carinatus in palatal view. From Case and Williston (1912). Scale = 1 cm.

Fig. 13. Skull reconstruction of Limnoscelis paludis is dorsal (A), ventral (B), lateral (C), and occipital (D) views, as well as the lateral (E) and medial (F) views of the lower jaw, based on holotype YPM 811. Scale = 2 cm. a, angular; ac, anterior coronoid; ar, articular; bo, basioccipital; d, dentary; ec, ectopterygoid; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pc, posterior coronoid; pf, postfrontal; pl, palatine; pm, premaxilla; po, postorbital; pp, postparietal; pra, prearticular; prf, prefrontal; ps, parasphenoid; pt, pterygoid; q, quadrate; qj, quadratojugal; s, septomaxilla; sa, surangular; so, supraoccipital; sp, splenial; sq, squamosal; st, supratemporal; t, tabular; v, vomer. From Reisz (2007).

Fig. 14. Skull of Tseajaia campi in dorsal (A), palatal (B), occipital (C), and lateral (D) views, with medial view (E) of lower jaw, based on holotype UCMP 59012. Scale = 2 cm. A, angular; AR, articular; BO, basioccipital; BPT, basipterygoid process; BS, basisphenoid; C, coronoid; D, dentary; EC, ectopterygoid; EO, exoccipital; F, frontal; FM, foramen magnum; FO, fenestra ovalis; IN, internal naris; IPTV, interpterygoid vacuity; J, jugal; L, lacrimal; M, maxilla; MF, Meckelian fenestra; N, nasal; OP, opisthotic; P, parietal; PAF, parietal foramen; PF, postfrontal; PL, palatine; PM, premaxilla; PO, postorbital; PP, postparietal; PRA, prearticular; PRF,

x prefrontal; PS, parasphenoid; PT, pterygoid; Q, quadrate; QJ, quadratojugal; SA, surangular; SO, supraoccipital; SP, splenial; SQ, squamosal; ST, supratemporal; STA, stapes; STF, subtemporal fossa; T, tabular; TO, premaxillary tooth; V, vomer. Modified from Moss (1972).

Fig. 15. Skull of MNG 10181, a complete, articulated skeleton of Orobates pabsti, in dorsal (A) and ventral (B) views. Scale = 2 cm. a, angular; d, dentary; e, epipterygoid; ec, ectopterygoid; eo, exoccipital; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pf, postfrontal; pl, palatine; pm, premaxilla; po, postorbital; pp, postparietal; pra, prearticular; prf, prefrontal; ps, parasphenoid; pt, pterygoid; q, quadrate; qj, quadratojugal; sa, surangular; soc, supraoccipital; sp, splenial; sq, squamosal; st, supratemporal; t, tabular; tm, ossified tympanic membrane; v, vomer.

Fig. 16. Skull of MNG 8760, disarticulated remains of a partial skeleton of Orobates pabsti, in dorsal (A) and ventral (B) views. Scale = 2 cm. a, angular; ar, articluar; d, dentary; c, coronoid; ec, ectopterygoid; eo, exoccipital; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pf, postfrontal; pl, palatine; pm, premaxilla; po, postorbital; pra, prearticular; prf, prefrontal; ps, parasphenoid; pt, pterygoid; q, quadrate; qj, quadratojugal; sa, surangular; scp, sclerotic plates; sm, septomaxilla; soc-pp, supraoccipital-postparietal; sp, splenial; sq, squamosal; st, supratemporal; t, tabular; tm, ossified tympanic membrane.

Fig. 17. Skull of MNG 8980, a nearly complete, articulated skeleton of Orobates pabsti, in dorsal (A) and ventral (B) views. Scale = 2 cm. a, angular; ar, articular; d, dentary; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp, postparietal; pra, prearticular; prf, prefrontal; pt, pterygoid; q, quadrate; qj, quadratojugal; sa, surangular; sm, septomaxilla; soc, supraoccipital; sp, splenial; sq, squamosal; st, supratemporal; t, tabular; tm, ossified tympanic membrane.

Fig. 18. CM 47654, left maxilla and holotype of Desmatodon hesperis in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm.

xi foramen; pl, parietal lappet; pp, postparietal; pr, prootic; ps, parasphenoid; st, supratemporal; t, tabular. From Vaughn (1972).

Fig. 20. CM, 47670, collection of Desmatodon hesperis remains containing a right lower jaw (A, lateral view; B, medial view; C, occlusal view) and a dorsal vertebra, caudal vertebra, and articulated right pterygoid and quadrate (medial view, D). Scale = 2 cm. a, angular; ar, articular; c, coronoid; cv caudal vertebra; d, dentary; dv, dorsal vertebra; cv, pra, prearticular; pt, pterygoid; q, quadrate; sa, surangular; sp, splenial; tf, transverse flange of pterygoid. From Berman and Sumida (1995).

Fig. 21. CM 47677, anterior portion of a right maxilla of Desmatodon hesperis in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm. From Berman and Sumida (1995).

Fig. 22. CM 47678, left premaxilla of Desmatodon hesperis in lateral (A) and medial (B) views. Scale = 1 cm. From Berman and Sumida (1995).

Fig. 23. OMNH 55350, partial dentary of Diasparactus zenos in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm. From Kissel and Lehman (2002).

Fig. 24. UC 675, skull of Diadectes sideropelicus in dorsal (A), palatal (B), and left lateral (C) views. Scale = 2 cm.

Fig. 25. MCZ 2989, holotype skull of Diadectes sanmiguelensis in lateral (A) and dorsal (B) views, with the right lower jaw in lateral (C) and medial (D) views. Scale = 2 cm.

Fig. 26. MNG 8853, holotype skeleton of Diadectes absitus in dorsal view (A) and skull in (B) and lateral (C) views. Scales = 5 and 2 cm. From Berman et al. (1998a).

Fig. 27. MCZ 1035, nearly complete skeleton of Diadectes tenuitectes in left lateral view.

Fig. 28. Consensus (A) and equally parsimonious hypotheses (B-C) demonstrating the interrelationships of Diadectidae. Autapomorphies of the clades and terminal taxa as presented in Hypothesis A, with all characters listed possessing an unambiguous history: Node A: 2(1), 3(1), 6(2), 12(1), 20(1), 21(2), 22(1), 33(1); Node B (Diadectidae): 26(1), 29(1), 30(1); Node C: 25(1), 27(1), 35(1); Node D: 42(1); Node E: 17(1), 24(1), 36(1); Node F: 21(1), 22(2), 28(2); Node G (Diadectes): 6(1), 13(2), 14(2), 19(1), 29(2), 30(2), 31(1), 35(2). Bootstrap and decay xii index values determined in Paup 4.0b10 are: Node B: 97, 3; Node C: 97, 3; Node D: 68, 1; Node E: 84, 2; Node F: 61, 1; Node G: 96, 4.

Fig. 29. MCZ 2780, fragmentary dentary of juvenile Diadectes sideropelicus in lateral (A), occlusal (B), and medial (C) views. Scale = 1 cm.

Fig. 30. Femora (left to right) of Diadectes sideropelicus (MCZ 1717 and 27850) and Diadectes tenuitectes (MCZ 3002, two specimens) in dorsal (A) and ventral (B) views, showing the distinct difference in size between the two forms. Scale = 5 cm.

Fig. 31. Lower jaw of MCZ 1035, Diadectes tenuitectes, in lateral (A) and anterolateral (B) views.

Fig. 32. Reconstruction of the skull of Orobates in lateral (A) and dorsal (B) views, based on specimens (MNG 10181, MNG 8980, and MNG 8760) assigned to Orobates pabsti. Scale = 2 cm. eo, exoccipital; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp, postparietal; prf, prefrontal; q, quadrate; qj, quadratojugal; sm, septomaxilla; soc, supraoccipital; sq, squamosal; st, supratemporal; t, tabular; tm, ossified tympanic membrane.

Fig. 33. Reconstruction of the skull of Oradectes in lateral (A) and dorsal (B) views, based on specimen MCZ 2989, the holotype and only known specimen assigned to Oradectes sanmiguelensis. Poor preservation prevents a confident placement of the postparietal- supraoccipital suture. Scale = 2 cm. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp, postparietal; prf, prefrontal; q, quadrate; qj, quadratojugal; soc, supraoccipital; sq, squamosal; st, supratemporal; t, tabular.

Fig. 34. Reconstruction of the skull of Silvadectes in lateral (A) and dorsal (B) views, based on MNG 8853, the holotype of Silvadectes absitus. Scale = 2 cm. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp-soc, postparietal- supraoccipital; prf, prefrontal; q, quadrate; qj, quadratojugal; sq, squamosal; st, supratemporal; t, tabular.

Fig. 35. Previous interpretations of the skull roofing elements of the genus Diadectes, with author(s) and year of study noted; all reconstructions illustrating dorsal view. EO, exoccipital; F,

xiii frontal; IT, intertemporal; L, lacrimal; N, nasal; P, parietal; PF, postfrontal; PM, premaxially; PO, postorbital; PP, postparietal; PRF, prefrontal; Q, quadrate; QJ, quadratojugal; SO, supraoccipital; SO-PP, supraoccipital-postparietal; SQ, squamosal; ST, supratemporal; T, tabular. Modified from Berman et al. (1992).

Fig. 36. Reconstruction of the skull of Diadectes in lateral (A) and dorsal (B) views, modified from Reisz (2006; lateral view), Olson (1947; dorsal view), and specimens (UC 706, UC 1078, and UR 27) assigned to Diadectes sideropelicus. Scale = 2 cm. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp, postparietal; prf, prefrontal; q, quadrate; qj, quadratojugal; soc, supraoccipital; sq, squamosal; st, supratemporal; t, tabular.

Fig. 37. Phylogeny of Diadectomorpha within a temporal framework, illustrating the diversification of the group during the Late Pennsylvanian Period. Solid lines denote known occurrence, with faded lines representing ghost lineages. Placement of the Wolfcampian- Leonardian boundary from Lucas (2006), with listed numerical ages from Ogg et al. (2008). Des, Desmoinesian; Leonard, Leonardian; Miss, Missourian, Virgil, Virgilian.

Fig. 38. Evolutionary history of traits leading to more efficient oral-processing within Diadectidae.

Fig. 39. Summary of published accounts of Missourian-Leonardian tetrapod-bearing fossil localities, highlighting the number of total sites, the number of sites bearing herbivorous tetrapods (i.e., Edaphosaurus, caseids, bolosaurids, moradosaurines, and diadectids), and the number of those sites producing diadectid remains.

xiv

List of Appendices

Appendix 1. List of characters used to test the monophyly of Diadectidae. No characters were ordered. Characters incorporated from other studies are referenced, with the original number of the character from a particular study indicated.

Appendix 2. Data matrix used to test the monophyly of Diadectidae.

Appendix 3. List of characters used to test the interrelationships of Diadectidae. No characters were ordered. Characters incorporated from other studies are referenced, with the original number of the character from a particular study indicated if appropriate.

Appendix 4. Data matrix used to test the interrelationships of Diadectidae.

xv 1

Chapter 1 Introduction and Historical Background

The evolution of herbivory in terrestrial tetrapods occurred during the late Paleozoic Era,

approximately 300 million years ago, and it lead to not only the development of the basic

pyramidal trophic structure of modern terrestrial ecosystems, where large numbers of herbivores support much smaller populations of top carnivores, but also an increase in tetrapod diversity and distribution (Hotton et al., 1997; Sues and Reisz, 1998; Sues, 2000). Phylogenetic analyses suggest that herbivory was acquired repeatedly and independently in several different tetrapod

lineages during the Late Pennsylvanian and Permian periods (Sues and Reisz, 1998), with high-

fiber herbivory limited to the cotylosaur clade (Hotton et al., 1997). Based on dental and

postcranial anatomy, members of Diadectidae are thought to represent the earliest known

examples of vertebrates capable of processing a diet of high-fiber terrestrial plants. Of the

known Permo-Carboniferous taxa exhibiting the adaptive traits of herbivory, Diadectidae is the

most diverse and widely distributed group; thus, it represents the first radiation of herbivorous

terrestrial tetrapods. Despite their importance regarding the evolution of modern ecosystems,

however, Diadectidae is a poorly understood taxon, having received its last detailed treatment in

1947.

In 1878, Cope (1878a) described several vertebral fragments and a jaw fragment bearing two

complete and two damaged teeth from the Lower Permian of Texas, designating the material

(AMNH 4360) as the holotype of a new genus, Diadectes. The name Diadectidae was first

proposed by Cope (1880a) to include the genera Diadectes and Empedocles Cope, 1878a, and

within fifteen years of its description, nine additional genera were referred to Diadectidae:

Nothodon Marsh, 1878; Helodectes Cope, 1880b; Chilonyx Cope, 1883; Empedias Cope, 1883;

Bolbodon Cope, 1896; Desmatodon Case, 1908; Diasparactus Case, 1910; Diadectoides Case,

1911; and Animasaurus Case and Williston, 1912. Case and Williston (1912) and Romer (1944)

synonymized Nothodon and Bolbodon with Diadectes, respectively, Olson (1947) synonymized

Chilonyx, Empedias (=Empedocles), Diadectoides, and Animasaurus with Diadectes, and

Berman et al. (1998b) showed that Helodectes is a junior synonym of Diadectes.

It is of note that Marsh’s (1878) description of Nothodon first saw print five days before Cope’s

(1878a) study that included the description of Diadectes (Williston, 1911). The nomen

Nothodon therefore maintains priority over Diadectes, as dictated by Article 23.1 (the Principle

of Priority) of the International Code of Zoological Nomeclature, but Case and Williston (1912)

synonymized Nothodon with Diadectes—presumably for the personal reasons cited by Case

(1911)—and the name Diadectes has populated the literature since. In the interest of stability

and in keeping with Article 23.2 of the ICZN, the long-accepted nomen Diadectes is maintained

herein and its continued recognition and usage is recommended.

In a review of the group, Olson (1947) recognized three genera and six species of Diadectidae

from North America: Diadectes sideropelicus Cope, 1878a; Diadectes tenuitectes (Cope, 1896);

Diadectes lentus (Marsh, 1878); Diadectes carinatus (Case and Williston, 1912); Diasparactus

zenos Case, 1910; and Desmatodon hollandi (Case, 1908). Since Olson’s (1947) review,

Vaughn (1969a) has described Desmatodon hesperis, and Lewis and Vaughn (1965) described

Diadectes sanmiguelensis. Both species were recovered from Colorado. Reisz and Sutherland

(2001) described an unnamed form from Oklahoma based on four frontals, one postfrontal, five

incisiform teeth, and nine molariform cheek teeth.

Four diadectid taxa are currently recognized from Europe, and all are found in Germany. Meyer

(1860) described Phanerosaurus naumanni based on an articulated series of four presacral and

two sacral vertebrae produced from the Leukersdorf Formation of the Erzgebirge Basin near

Zwickau. A small collection of cranial and postcranial remains, including several vertebrae and a disarticulated skull from the Doehlen Basin near Dresden, was described as Phanerosaurus pugnax by Geinitz and Deichmueller (1882), but Stappenbeck (1905) reassigned the material to a new genus, Stephanospondylus. Both the vertebrae of Phanerosaurus and the dentition and vertebrae of Stephanospondylus possess the typical diadectid form (Romer, 1925), and they bear similarities to those of the recently described but more completely known Diadectes absitus and

Orobates pabsti, but the true affinity of Phanerosaurus and Stephanospondylus is difficult to

determine in light of their known, fragmentary remains. Berman et al. (1998a) described

Diadectes absitus and Berman et al. (2004) described the new form Orobates pabsti, both from

the Bromacker Quarry of the Tambach Formation. Finally, a new form, Ambedus pusillus, was

described by Kissel and Reisz (2004a) as part of the current study. Thus, the number of

currently recognized, named diadectid taxa includes seven genera with thirteen species.

The stratigraphic range of Diadectidae extends from the Late Pennsylvanian to the Early

Permian. Desmatodon is a Late Pennsylvanian taxon known primarily from skull material and

dentition recovered from the Missourian Red Knob Formation of Pennsylvania (Case, 1908;

Romer, 1952; Berman and Sumida, 1995), Missourian Sangre de Cristo Formation of Colorado

(Vaughn, 1969a; Berman and Sumida, 1995), and Virgilian Cutler Formation of New Mexico

(Berman, 1993). This genus is the earliest known tetrapod possessing an anatomy suggestive of high-fiber herbivory. Diasparactus remains have been recovered from the Upper Pennsylvanian

Virgilian Cutler and Ada formations of New Mexico and Oklahoma, respectively (Berman,

1993; Kissel and Lehman, 2000; Kissel and Lehman, 2002). Ambedus is known from a single

locality in the Lower Permian strata of Ohio (Kissel and Reisz, 2003, 2004a). Diadectes, the

most commonly found and well-known diadectid, is known from the Upper Pennsylvanian of

Utah and the Lower Permian of Colorado, New Mexico, Ohio, Oklahoma, Texas, Utah, West

Virginia, Prince Edward Island, and Germany (Olson, 1947; Langston, 1963; Lewis and Vaughn,

1965; Olson, 1967; Berman, 1971; Olson, 1975; Berman, 1993; Berman et al., 1998a, 1998b;

Sumida et al., 1999). Phanerosaurus and Stephanospondylus are restricted to the Lower

Permian. Perhaps the best-known genus, Orobates, is known from nearly complete, articulated

skeletons recovered from the Lower Permian Tambach Formation of central Germany (Berman

et al., 2004).

Examined here is the stratigraphic occurrence, geographic distribution, and dental, cranial, and

postcranial anatomy of known diadectid taxa, producing a modern review of diadectid morphology, phylogeny, taxonomy, and paleozoogeography. The study incorporates recently

discovered fossil specimens and techniques (e.g., CT scanning) that will provide anatomical

details of diadectid cranial and dental morphology unavailable in previous analyses. Previously

published data on the paleozoogeographic distribution of late Paleozoic tetrapod taxa is compiled

into a single, easily accessible record, documenting the relative abundance and distribution—

both geographic and stratigraphic—of Late Pennsylvanian and Early Permian herbivorous terrestrial vertebrates. Information obtained from the current study will produce a better

understanding of the early evolutionary history of herbivory in terrestrial tetrapods, thereby providing a more complete view of vertebrate evolution and, more specifically, the appearance and formation of the modern terrestrial ecosystem.

Institutional abbreviations used throughout the text are as follows: AMNH, American Museum of Natural History, New York, New York; CM, Carnegie Museum of Natural History,

Pittsburgh, Pennsylvania; FMNH, The Field Museum, Chicago, Illinois; MCZ, Museum of

Comparative Zoology, Harvard University, Cambridge, Massachusetts; MNG, Museum der

Natur, Gotha, Germany; OMNH, Sam Noble Oklahoma Museum of Natural History, Norman,

Oklahoma; UC, The Field Museum, Chicago, Illinois; UCLA VP, University of California, Los

Angeles (material now housed at the Carnegie Museum of Natural History, Pittsburgh); UCMP,

University of California Museum of Paleontology, Berkeley, California; UR, The Field Museum,

Chicago, Illinois; YPM, Peabody Museum of Natural History, New Haven, Connecticut.

Chapter 2 Description of a New Diadectid from the Lower Permian of Ohio 1 Introduction

Presented here is a new genus and species of Diadectidae from the Dunkard Group of Ohio.

Collection data indicates that the specimens attributed to this new form, which was initially

reported by Kissel and Reisz (2003), had been recovered from Clark Hill in Monroe County,

Ohio, with the fossil-bearing horizon found approximately 2.5 m below the Nineveh Coal of the

Greene Formation. The fossil remains are preserved in a light gray, micaceous claystone that weathers to tan. Remains of the dipnoan Sagenodus, the trimerorhachid Trimerorhachis, a

possible embolomere, and the synapsid Ctenospondylus ninevehensis have also been reported

from Clark Hill (Berman, 1978). Produced from a single site in the Greene Formation, these

four taxa were recovered from the Nineveh Limestone, which is interpreted as a freshwater pond

or lake deposit (Berman, 1978).

Recognition of the new form from Clark Hill marks only the second recorded occurrence of

diadectid remains from Ohio and the third recorded occurrence of diadectid remains from the

Dunkard. Olson (1970; 1975) reported the presence of Diadectes from the Belpre locality of

Washington County, Ohio, and Berman (1971) referred a skull that was recovered from Roane

County, West Virginia to Diadectes. With both the Belpre and Roane County localities found

within the Washington Formation, the unit that underlies the Greene Formation, the new form

represents the youngest diadectid recovered from the Dunkard. Age assignments of the Dunkard

Group range from Late Pennsylvanian (e.g., Clendening, 1975) to Early Permian (e.g., Durden,

1975; Eagar, 1975; Remy, 1975), with the vertebrate taxa identified from Dunkard strata

indicative of an Early Permian age (e.g., Berman and Berman, 1975; Lund, 1975; Olson, 1975).

The description below was published by Kissel and Reisz (2004a).

Systematic Paleontology

Cotylosauria Cope, 1880a

Diadectomorpha Watson, 1917

Diadectidae Cope, 1880a

Ambedus, new genus

Diagnosis.—A small diadectid distinguishable from other members of the group by: 1) a shallow

dentary; 2) relatively high maxillary and mandibular tooth count; 3) lack of a labial parapet of

dentary; 4) anterior teeth of maxilla and dentary conical, in contrast to the incisiform anterior

teeth of other diadectids; and 5) shallow alveolar shelf, which suggests a relatively shallow tooth implantation.

Etymology.—Latin, ambedo, to nibble.

Ambedus pusillus, new species

(Figs. 1-5)

Holotype.—MCZ 9436, nearly complete right maxilla.

Horizon.—Eight feet below Nineveh Coal Horizon, Greene Formation, Dunkard Group.

Locality.—Clark Hill, sec. 16, Salem Township, Monroe County, Ohio.

Diagnosis.—Same as that for the genus, this being the only known species.

Referred Specimens.—MCZ 9437, poorly preserved maxilla; MCZ 9438, complete left dentary;

MCZ 9439, anterior portion of right dentary; MCZ 9440, posterior portion of left dentary; MCZ

9441, poorly preserved right dentary.

Etymology.—Latin, ambedo, to nibble; pusillus, tiny.

2 Description and comparison

2.1 Introduction

The material assigned to Ambedus pusillus consists of two maxillae (MCZ 9436 and 9437) and four dentaries (MCZ 9438, 9439, 9440, and 9441) of varying completeness. Both MCZ 9437 and 9441 are poorly preserved, with much of the bone either missing or severely damaged, so the description of A. pusillus is restricted to four elements, a right maxilla (MCZ 9436) and a left

(MCZ 9438) and two right (MCZ 9439 and 9440) dentaries. MCZ 9436 is incomplete anteriorly and also lacks the extreme posterior tip, and MCZ 9439 and 9440 lack the posterior and anterior portions, respectively. In order to preserve the impression of the sixth tooth of the series, matrix was not completely prepared from the anterior portion of MCZ 9439; thus, the anterior teeth of this specimen are exposed in lateral view only. MCZ 9438 is a complete left dentary exposed primarily in lateral view, with the occlusal surfaces of several teeth also exposed. Prior to their recognition as diadectid remains, the above specimens were collectively catalogued as MCZ

8667 and assigned to Mycterosaurus sp. Also referred to MCZ 8667 is an isolated humerus that was collected within the same vicinity as the maxillae and dentaries. Because the humerus

9 exhibits no features indicative of Diadectidae, it is not referred to Ambedus pusillus, and it is therefore not described herein.

Among diadectid taxa, the maxilla and dentary are known in Diadectes, Diasparactus,

Desmatodon, and Orobates. The genus Phanerosaurus is based solely on an articulated series of four presacral and two sacral vertebrae (Meyer, 1860), so comparison to it is not useful for this study. Stephanospondylus is known from a wider range of elements, including tooth-bearing elements of the upper and lower jaws (Stappenbeck, 1905; Romer, 1925), but it remains a poorly known taxon, and Berman et al. (1998a) suggest that the holotype may represent a juvenile form.

Further evaluation of this taxon is required, and it is therefore not included in this study unless specifically noted. Thus, comparison of A. pusillis is restricted primarily to Diadectes,

Diasparactus, Desmatodon, and Orobates, with comparison to the Richards Spur diadectid material restricted to dental morphology.

As discussed below, the remains described herein as A. pusillus possess none of the features that typify known juvenile individuals of previously described diadectid taxa. All elements are therefore thought to represent those of adult individuals.

2.2 Maxilla

The maxilla (Fig. 1) is represented by MCZ 9436, a nearly complete right maxilla that possesses

12 teeth and one empty alveolus. Only the extreme tip of the posterior end is lacking in MCZ

9436, but a larger portion of the anterior end is missing. Although the anterior portion of the tooth row is therefore likely incomplete in MCZ 9436, the preserved tooth positions are numbered from one to 13 for purposes of description, with tooth one representing the most anterior of the preserved teeth.

In lateral view, the dorsal margin is highly convex, as in the posterior region of the maxilla of

both Diadectes and Desmatodon. The ventral margin is nearly horizontal, as in all diadectids.

As preserved, the lateral surface is rough and pitted, but this texture no doubt results from poor

preservation and crushing of the lateral surface, especially of the very thin dorsal lamina. With

the exception of small foramina just above the tooth row, the lateral surface was likely smooth,

as in the dentary, and it is flat and vertical. The dorsal portion of the dorsal lamina is displaced

medially relative to the ventral portion of the lateral surface, but this displacement results from

movement along a postmortem break that extends anteriorly from the posterior margin of the

dorsal lamina to the level of the fifth tooth.

Description of the medial surface of the maxilla is restricted to the alveolar shelf, as the thin,

fragile nature of the dorsal lamina prevented its complete preparation. The alveolar shelf is smoothly finished and, relative to other diadectids, shallow. It is a convex, rounded ridge to the level of the fifth tooth. At the sixth tooth position, an arcuate groove originates from the ventral margin and extends to the ventral margin at the level of tooth ten. Anteriorly, the groove is wide and faces medially, but as it extends dorsoposteriorly, it narrows and faces dorsally and slightly medially. Posteriorly, the groove widens to form a dorsomedially facing platform. A ridge defines the dorsal margin of the groove anteriorly. Ventral to the groove, the alveolar shelf is convex. From the level of tooth five to tooth seven, the dorsal surface of the alveolar shelf is a flat, dorsally facing platform. It is slightly convex and faces dorsomedially throughout its remaining length.

MCZ 9436 possesses 13 teeth, including the empty alveolus at tooth position four. Because the anterior portion of MCZ 9436 is lacking, it can only be stated that a minimum of 13 maxillary teeth were present. In MCZ 9436, tooth 13 likely represents the last tooth of the maxillary series,

11 so only the anteriormost maxillary teeth are not preserved. Maxillary tooth counts in other diadectids include 11 for Diadectes (Case and Williston, 1912; Berman et al., 1998a), 12 for

Desmatodon (Berman and Sumida, 1995), 12 for Orobates (Berman et al., 2004), and the right maxilla of Stephanospondylus illustrated by Geinitz and Deichmüller (1882, plate IV, fig. 2) possesses a series of 12 teeth (Romer, 1925).

The shallow alveolar shelf in Ambedus pusillus suggests that tooth implantation was not as deep as that in other diadectids. Whereas the root is longer than the height of the crown in Diadectes,

Diasparactus, Desmatodon, and Orobates, the shallow alveolar shelf of MCZ 9436 indicates that root length is less than crown height in Ambedus, as observed in the diadectomorphs Limnoscelis and Tseajaia. In no specimen is it possible to determine if the marginal teeth of Ambedus exhibit infolding of the dentine, a feature present in all other diadectomorphs.

In occlusal view, the maxillary dentition is aligned in a straight row with only a slight lateral deflection anteriorly. It is possible that, if the tooth row were completely preserved, this deflection would continue and become more prominent, as in other diadectids. The maxillary dentition of heretofore known diadectids consists of two incisiform teeth that are succeeded by a series of molariform cheek teeth. The incisiform teeth are oval in section near the base and are excavated lingually on the distal half to produce a chisel-like distal tip, and the cheek teeth are transversely expanded with an occlusal surface that possesses a central cusp flanked by labial and lingual shoulders. The maxillary dentition of Ambedus adheres to this general pattern, but the anteriormost teeth of MCZ 9436 are not incisiform. Since the anterior portion is lacking in

MCZ 9436, it is likely that the anterior teeth of the maxilla are also not preserved, opening the possibility that the anterior teeth, if present, would exhibit an incisiform morphology. However, the lack of incisiform anterior teeth on the dentary, as described below, strongly suggests that the

upper tooth row also lacked incisiform dentition. As the tooth row in MCZ 9436 extends

posteriorly, the teeth gradually expand transversely until tooth position nine, from which point

they decrease in transverse width posteriorly to the end of the series. The alveolar shelf attains

its greatest mediolateral width at the level of tooth seven in order to accommodate the

transversely expanded cheek teeth. In Diadectes, the maxillary cheek teeth increase in width to

the sixth or seventh tooth and then decrease to the posterior end of the series (Case and Williston,

1912; Berman et al., 1998a). A similar pattern is found in CM 47654, a left maxilla of

Desmatodon hesperis, but the serial decrease in width after the widest tooth, tooth seven, is less

drastic than that in Diadectes.

The first two teeth of the maxillary series of Ambedus pusillus are conical with a weakly

developed lingual shoulder and a medially directed central cusp. Tooth three is the first of the

series to exhibit the transversely expanded, molariform cheek teeth that are characteristic of

diadectids, although the labial shoulder is weakly developed and the central cusp possesses a

slight medial tilt. On teeth one to three, longitudinal fluting is present on the distal third of the

lingual surface. Tooth four is not preserved. The fifth tooth possesses both labial and lingual

shoulders, but the lingual shoulder is the larger of the two. Also, beginning with tooth five and present on the remaining teeth of the series, the central cusp is directed dorsally and longitudinal fluting is present on the distal half of the lingual surface and near the tip on the labial surface.

Although tooth four is not present and tooth six is incomplete, they were likely intermediate in form between teeth three and five and five and seven, respectively.

Teeth seven to 11 possess a uniform morphology, with a low central cusp flanked by rounded shoulders both labially and lingually, lacking the prominent labial and lingual cusps found in the cheek teeth of Diasparactus and all species of Diadectes except D. absitus. In D. absitus, the

13 maxillary cheek teeth each bear a tall central cusp, and the labial and lingual cusps are poorly developed, resembling shoulders more than cusps (Berman et al. 1998a). The cheek teeth of

Desmatodon have well-developed central and lingual cusps, with a rounded shoulder labially.

With a nearly vertical labial surface and a medially sloping lingual surface near the base of the crown, the outline of the cheek teeth in posterior view (Fig. 2A) differs considerably from other diadectids. In Desmatodon, Orobates, and the unnamed Richards Spur diadectid, the cheek teeth exhibit an exaggerated teardrop, or spade-like, outline (Reisz and Sutherland, 2001; Kissel et al.,

2002; Berman et al., 2004), and Diadectes and Diasparactus exhibit abrupt, shoulder-like expansion of the labial and lingual margins dorsal to a slight constriction between the crown and root. Tooth nine of MCZ 9436 possesses the greatest transverse width of the series, and it also exhibits the greatest degree of molarization of the series. Berman and Sumida (1995) demonstrated that the cheek teeth in adult specimens of Diadectes possess a greater degree of molarization than those of adult Desmatodon specimens (i.e., the cheek teeth of Diadectes have a much greater transverse width relative to their anteroposterior length and dorsoventral height than those of Desmatodon). Ambedus possesses a similar degree of molarization as Desmatodon hesperis and a significantly lesser degree of molarization than both Diadectes lentus and

Desmatodon hollandi (Table 1), with the similar height/width ratios exhibited by A. pusillus and

D. hesperis resulting from the tall, well-developed central cusp of the latter species, in contrast to the low central cusp of the former, and not from a similarity in tooth morphology. Tooth 12 exhibits a lesser degree of molarization than those teeth immediately anterior to it, its morphology resembling tooth three. Only the base of tooth 13 is preserved, and it possesses a subcircular section.

Wear facets are present on the lingual shoulders of teeth nine, 10, and 11 in MCZ 9436. Such an uneven wear pattern of the maxillary cheek teeth, with a greater degree of wear on the lingual

shoulder or cusp than on the labial shoulder or cusp, is characteristic of diadectids (Berman et al.,

1998b). Of these wear facets, none possess microwear patterns (e.g., striations) that may

indicate a direction, or directions, of jaw movement during oral processing.

2.3 Dentary

The dentary (Figs. 3, 4, 5) is long and shallow, in strong contrast to that of all other diadectids in

which the element is known. In Diadectes (Welles, 1941; Berman et al., 1998a), Desmatodon

(Berman and Sumida, 1995), Stephanospondylus (Romer, 1925), and likely Diasparactus, it is

relatively short anteroposteriorly and deep dorsoventrally. The complete mandible of

Diasparactus is known, but sutures delineating the individual elements are not visible (Case and

Williston, 1913); however, with the general morphology of the mandible and the known

morphology of the dentary resembling that of Diadectes (Case and Williston, 1913; Kissel and

Lehman, 2002), it is probable that the complete dentary of Diasparactus was similar to that of

Diadectes.

Along the tooth-bearing area, the dorsal margin of the dentary of Ambedus is only slightly

concave in lateral view. Posterior to the last tooth of the series, the margin is gently convex. In

lateral view, the ventral margin is convex anteriorly and concave posteriorly. The ventral margin

slopes posteroventrally, with the dentary possessing the greatest dorsoventral height posteriorly.

In dorsal view, the dentary is thin anteriorly, expanding posteriorly to attain its greatest

mediolateral width at tooth positions 14 and 15.

With the exception of several foramina and shallow, longitudinal grooves below the tooth row,

the lateral surface is smooth. In other diadectids, the lateral surface of the dentary is irregularly

sculptured with prominent grooves and pits. Below the tooth row, the lateral surface, which is

vertical in other diadectids, curves and continues as a flat surface that extends ventromedially,

undercutting the alveolar shelf so that the ventral margin of the dentary lies medial to the tooth

row in anterior view. The dentary lacks the labial parapet and associated groove that is found in

Diadectes, Diasparactus, Desmatodon, and Orobates. Although initially described by Berman et

al. (1998a) as lacking a labial parapet, further preparation of the holotype of Diadectes absitus

(MNG 8853) has revealed the presence of a low parapet (D. S Berman, pers. comm.). In the

paratype of D. absitus (MNG 8747), the right mandible is incompletely preserved, making

determination of the presence of a labial parapet impossible, but it does possess a flat, dorsally

facing platform lateral to the tooth row posteriorly (Berman et al., 1998a), a feature also not

present in Ambedus.

The medial surface of the dentary is traversed by a deep meckelian canal along its length.

Anteriorly, the symphysis occupies the entire tip of the medial surface, extending posteriorly to

the level of the third tooth. Its surface is rough and therefore distinct from the remaining medial

surface. The meckelian canal continues anteriorly to divide the symphysis into distinct dorsal

and ventral areas, leaving only a small area at the anterior tip of the symphysis to connect these

two surfaces. The canal is shallowest within the symphysis, deepening and expanding

dorsoventrally as it extends posteriorly. Dorsal to the canal, the medial surface of the dentary is

convex from the symphysis to the level of the eighth tooth. Posterior to that position, the medial

surface is flat and oriented vertically. Aside from a series of mostly longitudinal grooves found

posterior to tooth position 12, the medial surface dorsal to the canal is smooth. Ventral to the

canal and posterior to the symphysis, the medial surface is flat and smoothly finished to the level

16 of the thirteenth tooth position, and it is inclined slightly so that the ventral margin lies slightly lateral to the dorsal margin. At the level of the thirteenth to fourteenth tooth position, the meckelian canal expands to completely excavate the ventral half of the medial surface of the dentary posteriorly. Thus, whereas its dorsal border is well-defined by the medial surface of the dentary throughout its entire length dorsally, the canal is well-defined ventrally from the symphysis to the level of tooth 13. As in the maxilla, the alveolar shelf is shallow relative to that of other diadectids, suggesting a relatively shallow tooth implantation in the dentary.

MCZ 9438, a complete left dentary, possesses a complete tooth row, and a total of 22 teeth are present. Incomplete posteriorly, MCZ 9439 possesses the first 18 teeth of the mandibular series, and MCZ 9440 is incomplete anteriorly, possessing teeth six to 22. Such a tooth count represents the greatest yet recorded for a diadectid, with the mandibular tooth counts of other diadectids including 14 to 18 for Diadectes (Case, 1911; Case and Williston, 1912; Welles,

1941; Berman et al., 1998a), 15 for Diasparactus (Kissel and Lehman, 2002), 14 for

Desmatodon (Berman and Sumida, 1995), 17 for Orobates (Berman et al., 2004), and possibly

15 for Stephanospondylus (Romer, 1925).

Specimens MCZ 9438, MCZ 9439, and MCZ 9440 all possess a similar dental morphology. In dorsal view, the dentition is aligned in the sigmoid curvature common to diadectids, but this curvature is slight and not as pronounced as in other members of the group. As in the upper jaw, the mandibular dentition of diadectids is differentiated into incisiform anterior teeth, molariform cheek teeth, and a short series of teeth intermediate to these two forms. However, whereas the anterior dentary teeth of other diadectids are strongly incisiform, those of Ambedus pusillus are conical; they are round in section near the base and terminate in a point, lacking the chisel- shaped, incisiform character of all other diadectids. As in other diadectids, however, the anterior

dentary teeth are procumbent. Tooth 12 is the first transversely expanded tooth of the series, with teeth nine to 11 intermediate to the pointed anterior teeth and the expanded cheek teeth.

The cheek teeth of the dentary possess a lesser degree of molarization than those of the maxilla

(Fig. 2; Tables 1, 2) and a significantly lesser degree than the dentary cheek teeth of Diadectes lentus, Diasparactus zenos, and Desmatodon hesperis (Table 2). As exhibited by MCZ 9438,

9439, and 9440, they possess a low central cusp flanked by rounded shoulders both labially and lingually, not unlike those of the maxilla. In posterior view, both the labial and lingual surfaces are nearly vertical, although the lingual surface slopes mediodorsally near the base of the teeth

(Fig. 2B). The teeth increase in size serially to tooth 18, from which point they slightly decrease in size posteriorly.

Nearly all of the dentary teeth possess wear surfaces, with the tips of the anterior conical teeth and the central cusp of the cheek teeth exhibiting wear. In MCZ 9439, teeth 13 to 18 are heavily worn, reducing the occlusal surfaces to smooth, flat surfaces that face dorsomedially. A smaller wear facet is present on the labial shoulder of tooth 16 in MCZ 9440. What may represent wear facets are present on the labial shoulders of teeth 17, 18, and 21 in MCZ 9440, but these “facets” may just represent damage to the surface of the teeth. The wear pattern exhibited on teeth 13 to

18 of MCZ 9439 and tooth 16 of MCZ 9440, with a greater degree of wear on the labial cusp or shoulder of the dentary cheek teeth, is characteristic of diadectids (Berman et al., 1998b). As in the maxillary dentition, none of these wear facets possess microwear patterns that may facilitate the reconstruction of jaw movement during oral processing.

2.4 Ambedus pusillus and diadectid ontogeny

The small size of the maxilla and dentaries described herein as Ambedus pusillus invites the hypothesis that these elements are simply the remains of a juvenile individual of a previously described diadectid taxon, but such an interpretation is refuted by the following observations. A maxilla (CM 47668) identified as a juvenile form of Desmatodon hesperis possesses four dental features that are absent or greatly reduced in mature specimens of the genus and not present in specimens of Diadectes of any age: 1) fewer number of teeth; 2) greater relative spacing between teeth to produce large gaps between teeth; 3) first two maxillary teeth relatively longer and more incisiform; and 4) absence of wear facets (Vaughn, 1972; Berman and Sumida, 1995). The maxillary teeth of Ambedus, in contrast, outnumber those of adult Desmatodon hesperis specimens, they are packed tightly with little space between them, and they possess wear facets.

In juvenile specimens of Diadectes, the cheek teeth exhibit a lesser degree of molarization than seen in the adult forms, with little or no transverse widening, a weakly developed central cusp, and no labial or lingual cusps (Berman and Sumida, 1995). Immature individuals of Diadectes do, however, possess a labial parapet (Berman et al., 1998a), a feature not present in Ambedus.

Furthermore, the conical anterior dentary teeth of A. pusillus are distinctly different than those of

Diadectes and Desmatodon, which do not exhibit any changes in their incisiform morphology throughout ontogeny (Berman and Sumida, 1995).

With the understanding of diadectid ontogeny currently limited to studies of Diadectes and

Desmatodon by Vaughn (1972) and Berman and Sumida (1995), comparison to immature individuals of the remaining diadectid taxa is not possible. However, in no known juvenile or adult of any diadectid taxon is the dentary as long and shallow as it is in Ambedus, supporting the

19 conclusion that the material described as Ambedus does not represent the juvenile remains of a currently known diadectid, but rather represents a unique member of the group.

2.5 Conclusions

The description of Ambedus pusillus increases the total number of currently recognized diadectid taxa to seven genera and thirteen species: Diadectes sideropelicus Cope, 1878a; Diadectes tenuitectes (Cope, 1896); Diadectes lentus (Marsh, 1878); Diadectes carinatus (Case and

Williston, 1912); Diadectes sanmiguelensis Lewis and Vaughn, 1965; Diadectes absitus Berman et al., 1998a; Diasparactus zenos Case, 1910; Desmatodon hollandi (Case, 1908); Desmatodon hesperis (Vaughn, 1969a); Phanerosaurus naumanni Meyer, 1860; Stephanospondylus pugnax

(Geinitz and Deichmüller, 1882); Orobates pabsti Berman et al., 2004; and Ambedus pusillus.

As previously indicated, affinity of the Richads Spur diadectid remains are uncertain at this time.

Ambedus pusillus is unique among diadectids in its high maxillary and mandibular tooth counts, lack of incisiform anterior teeth, shallow dentary, lack of a labial parapet, relatively shallow alveolar shelf suggesting the presence of teeth with roots shorter than the height of the crown, and lesser degree of molarization of the cheek teeth. Despite lacking a deep lower jaw, which is characteristic of herbivores and found in other diadectids, the presence of procumbent anterior teeth, molariform cheek teeth, and wear facets similar to those of other diadectids suggest that

Ambedus, like all other diadectids, may have been herbivorous.

Fig. 1. MCZ 9436, right maxilla and holotype of Ambedus pusillus in lateral (A), occlusal (B), and medial (C) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale

= 1 cm.

Fig. 2. Fifth posteriormost maxillary tooth of MCZ 9436 (A) and fifth posteriormost dentary tooth of MCZ 9440 (B) in posterior view. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 3. MCZ 9438, complete left dentary of Ambedus pusillus in lateral view. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 4. MCZ 9439, right dentary of Ambedus pusillus in lateral (A) and medial (B) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

Fig. 5. MCZ 9440, left dentary of Ambedus pusillus in lateral (A) and occlusal (B) views. Numbers indicate tooth positions. From Kissel and Reisz (2004a). Scale = 1 cm.

______Table 1. Maximum crown measurements (in mm) and ratios of largest preserved, midseries maxillary cheek teeth in selected specimens of Diadectes, Desmatodon, Orobates, and Ambedus. Modified from Berman and Sumida (1995). ______

Maximum Maximum Maximum Length/Width Height/Width

transverse anteroposterior height

width length

______

Diadectes lentus 13.6 5.3 5.5 0.39 0.40

FMNH UC 675 (positions 6 to 8)

Desmatodon hesperis 7.8; 9.3 5.3; 4.5 8.5; 8.0 0.68; 0.48 1.09; 0.86

CM 47654 (holotype; positions 7 and 8); CM 47677 (seventh posteriormost preserved tooth)

Desmatodon hollandi 9.5 4.3 7.0 0.45 0.74

CM 1938 (holotype; ?eighth posteriormost preserved tooth)

Desmatodon aff. D.hollandi 9.5 4.3 7.0 0.45 0.74

YPM 8639 (CM 38044; positions 9 to 11)

Orobates pabsti 5.4 1.8 6.0 0.33 1.11

MNG 11134 (positions 6 to 8)

Ambedus pusillus 2.11; 1.94 1.06; 1.10 1.86; 1.91 0.50; 0.57 0.88; 0.99

MCZ 9436 (holotype; tooth 9; tooth 8)

______

Table 2. Maximum crown measurements (in mm) and ratios of largest preserved, mideseris dentary cheek teeth in selected specimens of Diadectes, Diasparactus, Desmatodon, Orobates, and Ambedus. Modified from Berman and

Sumida (1995) and Kissel and Lehman (2002).

Maximum Maximum Maximum Length/Width Height/Width

transverse anteroposterior height

width length

______

Diadectes lentus 11.6 4.7 5.5 0.41 0.47

FMNH UC 675 (probable positions 8 to 10)

Diasparactus zenos 13.0 5.0 5.5 0.38 0.42

OMNH 55350 (tooth 10)

Desmatodon hesperis 8.8; 10.5 4.7; 5.7 7.0; 6.8 0.53; 0.54 0.80; 0.65

CM 47670 (positions 9 to 11); CM 47661 (isolated crown)

Orobates pabsti 5.3 2.7 6.4 0.51 1.21

MNG 11134 (tooth 14)

Ambedus pusillus 1.35; 1.35 1.10; 1.01 1.69; 1.69 0.82; 0.75 1.3; 1.3

MCZ 9440 (sixth posteriormost tooth position; fifth posteriormost tooth position)

Chapter 3 Phylogeny of Diadectidae 3 Introduction

Diadectidae was erected by Cope (1880a) to include the genera Diadectes and Empedocles, a form since synonymized by Olson (1947) with Diadectes. For much of its history, the group has been allied to the reptilian lineage of Amniota (e.g., Case, 1911; Olson, 1947), but recent phylogenetic analyses (e.g., Gauthier et al., 1988; Laurin and Reisz, 1995; Reisz, 1997; Reisz,

2007) indicate that Diadectidae forms a clade within Diadectomorpha Watson, 1917, which together with its sister-taxon Amniota Haeckel, 1866 constitutes Cotylosauria Cope, 1880a.

Although some workers (e.g., Berman et al., 1992; Modesto, 1992) have argued that diadectomorphs are amniotes, the placement of Diadectomorpha outside of Amniota, as their sister-clade, is the more widely accepted hypothesis (Berman et al., 1997; Reisz, 2007).

In addition to Diadectidae, Diadectomorpha contains the taxa Limnoscelidae and Tseajaia campi. Defined by Laurin and Reisz (1995) as the most recent common ancestor of Diadectidae,

Limnoscelidae, Tseajaia, and all of its descendants, diadectomorphs have been diagnosed by the following synapomorphies: single, median postparietal; quadratojugal not reaching level of orbit; occipital flange of squamosal absent;otic trough in vental flange of opisthotic; axial intercentrum with strong anterior process; humerus short and robust, without shaft; and dorsolateral shelf on iliac blade (Laurin and Reisz, 1995). Limnoscelids are known from Upper Pennsylvanian to

Lower Permian strata of North America, and Tseajaia is restricted to the Lower Permian of

North America.

While Diadectomorpha has received much attention in recent phylogenetic analyses, which is no

doubt due to its close affinities to Amniota, the interrelationships of diadectids are still poorly

understood, and they have yet to be subjected to phylogenetic analyses. A review of diadectid phylogeny and taxonomy is presented here with two separate analyses: the first, genus-based analysis tests and confirms the monophyly of Diadectomorpha and Diadectidae, whereas the second, more detailed and inclusive analysis examines the interrelationships of diadectid taxa.

4 Excluded Taxa

Diadectids not included in the below analyses are the unnamed Richards Spur form and the

monospecific genera Phanerosaurus and Stephanospondylus. In considering the potential

generic assignment of the Richards Spur diadectid (Fig. 6), Reisz and Sutherland (2001) noted

that the skull elements resembled those of Diadectes absitus, whereas the dentition was similar

to that of (the then unnamed) Orabates pabsti. In D. absitus, the posterior border of the

postfrontal is posterior to the frontal-parietal suture, but that of the Richards Spur form resides

significantly more posterior to that contact; potential assignment to D. absitus is therefore

questionable. The dentition is indeed similar to that in Orobates, but that illustrated by Reisz and

Sutherland (2001) also possesses a similar morphology to the anterior cheek teeth of the genus

Desmatodon. Stratigraphically, Desmatodon has thus far been recovered from Upper

Pennsylvanian deposits only, whereas both the Richards Spur form and Orobates are known

from Lower Permian units, but based strictly on anatomical details, assignment of the Richards

Spur form is not possible; it is maintained as an unnamed taxon herein and its incomplete nature

excludes it from the present analysis.

Meyer (1860) described Phanerosaurus naumanni on the basis of a single specimen: an

articulated series of four presacral and two sacral vertebrae collected from the Lower Rotliegend

Leukersdorf Formation of the Erzgebirge Basin near Zwickau, Germany (Fig. 7). The vertebrae

are diadectid in nature (Berman et al., 2004), with greatly swollen (i.e., broad, with

zygapophyses extending laterally far beyond the centra) and tall neural arches. The neural spines are diamond-shaped in dorsal view, with the long axis oriented anteroposteriorly, as in the

German form Diadectes absitus (Berman et al., 1998a), but they are significantly shorter dorsoventrally than those of D. absitus and all other known diadectids. Whether the height of the

neural spines as preserved in the holotype reflects the true morphology of P. naumanni or is the result of incomplete preservation or breakage is not evident in the figures originally published by

Meyer (1860; figs. 2-5) and later reproduced by Case (1911; fig. 15). Aside from the potentially reduced height of the neural spines, the vertebrae of P. naumanni possess no features that allow separation from other diadectids. It is possible that future studies will conclude that P. naumanni

Meyer, 1860 represents a nomen dubium, but that recommendation is not made at this time.

Also from the Lower Rotliegend of Germany is Stephanospondylus pugnax (Fig. 8). First described by Geinitz and Deichmüller (1882) as a member of the genus Phanerosaurus,

Stappenbeck (1905) referred the form to the new genus Stephanospondylus. Romer (1925) noted that the original and only specimen assigned to the genus actually contained the remains of two distinct taxa; he correctly concluded that elements of the specimen pertaining to the nomen S. pugnax—a near-complete right maxilla, tooth-bearing partial left and right mandibles, and a number of disarticulated vertebrae—are those of a diadectid.

As illustrated by Stappenbeck (1905; fig. 2), the anterior teeth of the dentary are procumbent

(Fig. 8A), whereas the cheek teeth of the both the dentary and the maxilla are transversely

expanded, or molariform, as in all diadectids (Fig. 8B-C). Within Diadectidae, there exist two

general types of molariform cheek teeth. In Ambedus pusillus, Desmatodon hesperis,

Desmatodon hollandi, Orobates pabsti, Diadectes absitus, Diadectes sanmiguelensis, and the

unnamed Richards Spur form, the cheek teeth possess a central cusp flanked by rounded labial

and lingual shoulders. In Diasparactus zenos and all other species of Diadectes, the cheek teeth

are wider labiolingually relative to their anteroposterior length, and they possess a central cusp

flanked by well-developed labial and lingual cusps. The cheek teeth of S. pugnax conform to the first type, possessing a central cusp with adjacent shoulders, and are indistinguishable from those of forms like Orobates pabsti (e.g., MNG 14000; Fig. 8E). Berman et al. (1997) stated that the remains assigned Stephanospondylus could pertain to either a limnoscelid or tseajaiid diadectomorph, but the molariform cheek teeth clearly establish this form as a diadectid.

The vertebrae of S. pugnax (Fig. 8D) possess swollen neural arches, but they lack the anterior hypantrum and posterior hyposphene articular surfaces that are found in all diadectid species

(except Diadectes absitus) in which the vertebrae are adequately known. In this respect, S. pugnax aligns with the German form D. absitus. The complete axial skeleton of Orobates,

another diadectid recovered from Germany, is known, but the preservation of only articulated

vertebral columns does not permit examination of the anterior and posterior surfaces of the

vertebrae. Several of the vertebrae illustrated by Geinitz and Deichmüller (1882) appear to

possess very short neural spines, as those shown by Phanerosaurus naumanni (Meyer, 1860), but

others appear to possess a taller spine. As with P. naumanni, further examination is required. It

is possible that future studies will conclude that Stephanospondylus pugnax (Geinitz and

Deichmüller, 1882) represents a nomen dubium, but until a closer examination and comparison

to the more recently described and more completely known Diadectes absitus Berman et al.

(1998a) and, especially, Orobates pabsti Berman et al. (2004) is conducted, that recommendation is not made at this time.

5 Monophyly of Diadectidae

Heaton (1980) proposed that Diadectomorpha represents a monophyletic group that consists of

(Limnoscelidae (Tseajaiidae + Diadectidae)). Subsequent studies (e.g., Gauthier et al., 1988;

Laurin and Reisz, 1995, 1997, 1999; Lee and Spencer, 1997) indicated that Diadectomorpha is the sister-taxon to Amniota, with Diadectomorpha + Amniota constituting Cotylosauria; however, in none of these analyses is Tseajaia incorporated, leaving Diadectomorpha as a monophyletic group consisting of Limnoscelis and diadectids. The only study since that of

Heaton (1980) to consider the interrelationships of diadectomorphs is that of Berman et al.

(1992). Based on a data matrix of seven taxa and nine characters of the temporal and occipital region, the analysis of Berman et al. (1992) supported the conclusions of Heaton (1980), with

Diadectomorpha consisting of (Limnoscelis (Tseajaia + Diadectes)).

To further test the monophyly of Diadectidae, a new phylogenetic analysis of Diadectomorpha is presented here. It includes nine taxa, including two outgroups, and 37 cranial, dental, and postcranial characters (Appendix 1, 2). When discussing characters of previously published phylogenetic analyses, the character numbers listed correspond to those assigned by the original authors. Because it is incompletely known, A. pusillus is scored for only six of these 37 characters; however, following the conclusions of Kearney and Clark (2003), A. pusillus is included in the analysis despite its incomplete nature. The analysis incorporates a number of characters that are derived from the analyses of Gauthier et al. (1988), Berman et al. (1992),

Laurin and Reisz (1995, 1997), Lee and Spencer (1997), Berman et al. (1998a), and Berman

(2000), but only characters that were found by these authors to possess an unambiguous history

were incorporated into the current analysis. Laurin and Reisz (1997) regarded the absence of a

tabular-parietal contact [24(0)] and the presence of uncinate processes [123(1)] as autapomorphies of Diadectes, but no specimens of Diadectes examined for this study possess uncinate processes, and the tabular does contact the parietal in Diadectes, as indicated by

Berman et al. (1998a) and Berman (2000), and all diadectomorphs in which that region of the skull is known. Thus, since characters 24(0) and 123(1) of Laurin and Reisz (1997) do not represent autapomorphies of Diadectes, they are not included here.

Outgroups in the analysis include Amniota—the sister-group to Diadectomorpha—and

Lepospondyli. Although Solenodonsaurus has been found to be the sister-group to Cotylosauria

(Gauthier et al., 1988; Laurin and Reisz, 1999), the specimens referred to that genus are fragmentary and lack much anatomical information; Lepospondyli, the sister-taxon to

Solenodonsaurus + Cotylosauria, was therefore selected as the second outgroup. Within

Diadectomorpha, the taxa Limnoscelis, Tseajaia, and Diadectidae (represented by Orobates,

Desmatodon, Diasparactus, and Diadectes) were analyzed. Also included in the study is the

new form Ambedus. Since Tseajaia remains the only genus assigned to Tseajaiidae, and all limnoscelids have been referred to the genus Limnoscelis (Wideman, 2002), both Tseajaiidae and

Limnoscelidae represent monogeneric taxa, so the nomina Limnoscelidae and Tseajaiidae are abandoned here.

Using Paup 4.0b10 (branch and bound search; Swofford, 2002) and MacClade 4.0 (Maddison and Maddison, 2000), the analysis yielded a single most parsimonious tree with a length of 53 steps, a consistency index (CI) of 0.8491, and a retention index (RI) of 0.8261. The resulting tree (Fig. 9) supports the previous hypothesis that Limnoscelis, Tseajaia, and diadectids form a

monophyletic group, Diadectomorpha, with diadectids and Tseajaia sharing a more recent common ancestor than either does with Limnoscelis. Here, Diadectomorpha is diagnosed by the presence of the following characters possessing an unambiguous history: a lateral parietal lappet

[2(1)], a single and median postparietal [4(1)], an otic trough in the ventral flange of the opisthotic [18(1)], the infolding of dentine [25(1)], deep marginal tooth roots [26(1)], an anterior process of the axial intercentrum-atlantal pleurocentrum complex [32(1)], a lateral shelf on the iliac blade [36(1)], and a short and robust humerus lacking a distinct shaft [37(1)].

The monophyly of Diadectidae is also supported by the current analysis, with diadectids consisting of a series of nested clades that terminates with Diasparactus + Diadectes.

Diadectidae, node D, is diagnosed by heterodont dentition characterized by the presence of transversely expanded cheek teeth [27(1)] and the presence of labial and lingual cusps of the cheek teeth [31(1)], and it is defined as Diadectes and all taxa sharing a more recent common ancestor with Diadectes than with Tseajaia (Kissel and Reisz, 2004a).

Ambedus is found to be the sister-taxon to all other members of Diadectidae. Although the known remains of Ambedus lack many of the structures considered in the analysis, the absence of a labial parapet of the dentary, deep tooth implantation, deep lower jaw, and well-developed molariform teeth with lateral and lingual cusps supports the position of Ambedus as the sister- taxon to all other diadectids.

Node E is diagnosed by the presence of a labial parapet of the dentary [22(1)], the presence of marginal teeth with roots longer than the height of the crown [26(2)], and the presence of incisiform anterior teeth [28(1)]; node F is diagnosed by the presence of a secondary palatal shelf

[12(1)] and the presence of a deep lower jaw [20(1)]; and node G is diagnosed by the presence of a jaw articulation located ventral the occlusal plane [19(1)], the presence of a tall labial parapet

[22(2)], the presence of a high degree of molarization of the cheek teeth [30(2)], and the presence

of well-developed labial and lingual cusps of the cheek teeth [31(2)].

During the execution of this analysis, certain characters were found to be problematic within the genus Diadectes. With the exception of Diadectes absitus and Diadectes sanmiguelensis, all species of the genus possess a deep lower jaw [20(1)]. Berman et al. (1998a) suggested that the shallow lower jaw of D. absitus represents an autapomorphy of that form. Character 22 is also problematic; D. absitus and D. sanmiguelensis both possess low labial parapets, whereas all other species of Diadectes possess a tall parapet. These features separate these two species from all members of Diadectes, and the more detailed phylogenetic analysis of the interrelationships of Diadectidae presented below addresses these issues by treating taxa at the specfic, not simply generic, level.

5.1 Revisiting Diadectomorpha as the sister-taxon to Amniota

Whereas the analyses of Gauthier et al. (1988), Laurin and Reisz (1995, 1997, 1999), and Lee

and Spencer (1997) hypothesized that Amniota and Diadectomorpha are sister-taxa (the

hypothesis supported by the analysis presented here), Berman et al. (1992) and Berman (2000) concluded differently, suggesting that Synapsida (the sister-taxon to reptilia, the two clades composing Amniota) is the sister-taxon to Diadectomorpha. This latter hypothesis, due to its unconventional nature, warrants discussion here in light of the phylogenetic analysis presented here.

Berman et al. (1992) united synapsids and diadectomorphs based on the presence of three synapomorphies: 2(1), posterolateral corner of the skull table formed entirely or nearly entirely by the supratemporal; 3(1), long posterior expansion of postorbital contacts supratemporal to

exclude the parietal lappet from contacting the squamosal; and 5(1), possession of an otic trough.

These characters are problematic. Although character state 2(1) is present in early synapsids,

recently described remains of Diadectes indicate that the posterolateral corner of the skull table of Diadectes is formed subequally by the supratemporal and tabular (Berman et al., 1998a), a condition shared with all other diadectids in which this region of the skull is known, Desmatodon

(Vaughn, 1972; fig. 4) and Orobates (Berman et al., 2004). As evidenced by YPM 811, the holotype of Limnoscelis paludis (the type species of the genus), the posterolateral corner of the skull table of Limnoscelis is also characterized by nearly equal contributions of the supratemporal and tabular. Only in Tseajaia does the tabular only contribute to the posterolateral corner of the skull table, with the supratemporal representing the dominant element of the region (Moss, 1972). Thus, the presence of a skull table in which the posterolateral corner is formed entirely or nearly entirely by the supratemporal [7(1) of the present study] is not shared by synapsids and all diadectomorphs, and its presence in Tseajaia

and synapsids may represent a convergence. As indicated by Laurin and Reisz (1995), the

second character [3(1)] of Berman et al. (1992) is present in diadectomorphs and all of Amniota,

whereas the third [5(1)] may have evolved convergently in both diadectomorphs and Synapsida,

since several early synapsids (e.g., Eothyris, Varanops, and Aerosaurus) have no otic trough.

Based on an analysis of eight characters of the occipital region, Berman (2000) cited the following three synapomorphies to link diadectomorphs and synapsids: 5(2), a deep, nonsculptured component of the tabular contacts the distal end of a ventrally displaced, laterally directed paroccipital process, enclosing laterally a small, ventrally displaced, posttemporal fenestra; 6(1), presence of an otic trough of the opisthotic; and 7(1), posterolateral corner of the skull table is formed subequally by the supratemporal and the tabular. As indicated by Berman

(2000), character state 7(1) represents a modification of character state 2(1) of Berman et al.

(1992), with the other two states (0, posterolateral corner of the skull table formed entirely by the tabular; and 2, posterolateral corner of the skull table formed almost entirely by the parietal and partly by a greatly reduced supratemporal) of characters 7 and 2 remaining identical. The posterolateral corner of the skull table in all diadectomorphs except Tseajaia, as discussed above, is indeed formed subequally by the supratemporal and tabular, but that of synapsids is formed entirely or nearly entirely by the supratemporal. Thus, whereas Diadectomorpha was incorrectly coded for character 2 of Berman et al. (1992), it is properly coded for character 7 of Berman

(2000), and whereas Synapsida was correctly coded for character 2 of Berman et al. (1992), it is incorrectely coded for character 7 of Berman (2000). Character states 7(1) and 2(1) of Berman

(2000) and Berman et al. (1992) can therefore not be regarded as a synapomorphy uniting

Diadectomorpha and Synapsida.

The second character state [6(1)] of Berman (2000) to link diadectomorphs to synapsids was refuted by Laurin and Reisz (1995) after its first description by Berman et al. [1992; 5(1)], as indicated above, and the first character [5(2)] is also questionable. Examination of YPM 811 indicates that the tabular of Limnoscelis does not contact the paroccipital process of the opisthotic to enclose a small posttemporal fenestra (contra Berman, 2000). The occipital regions of UCMP 59012, the holotype of Tseajaia campi, and FMNH UC 675, the only specimen of

Diasparactus to possess the skull, are imperfectly preserved, leaving the relationship between the tabular and opisthotic uncertain in both taxa. Although Vaughn (1972; fig. 4) described the presence of a fenestra between the postparietal and tabular in Desmatodon hesperis, no fenestra is located between the tabular and opisthotic. Thus, if Berman’s (2000) interpretation of the occipital region of Diadectes is correct, then the presence of character [5(2)] in Diadectes and some synapsids is likely the result of convergence.

With most of the characters used by Berman et al. (1992) and Berman (2000) to link diadectomorphs and synapsids either refuted or in question, the recognition of diadectomorphs and synapsids as sister-taxa is not well supported. Rather, based on the more inclusive analyses performed by Gauthier et al. (1988), Laurin and Reisz (1995, 1997, 1999), and Lee and Spencer

(1997), which employed much larger data matrices than those of Berman et al. (1992) and

Berman (2000), Diadectomorpha is regarded as the sister-taxon to Amniota, not a member of it.

6 Interrelationships of Diadectidae

The number of currently recognized diadectid taxa includes seven genera with thirteen species:

Ambedus pusillus Kissel and Reisz, 2004a; Desmatodon hollandi Case, 1908; Desmatodon

hesperis Vaughn, 1969a; Diadectes sideropelicus Cope, 1878a; Diadectes lentus (Marsh, 1878);

Diadectes tenuitectes (Cope, 1896); Diadectes carinatus (Case and Williston, 1912); Diadectes

sanmiguelensis Lewis and Vaughn, 1965; Diadectes absitus Berman et al., 1998a; Diasparactus

zenos Case, 1910, Orobates pabsti Berman et al., 2004; Phanerosaurus naumanni Meyer, 1860;

and Stephanospondylus pugnax (Geinitz and Deichmueller, 1882). Preliminary results of the

first phylogenetic analysis to incorporate all well-known diadectid species (Kissel et al., 2005)

demonstrated that the currently accepted taxomony of Diadectidae is in need of review. The

objective of the following, expanded analysis is to examine the interrelationships of these taxa.

Phylogenetic hypotheses produced by the analysis will allow a reconsideration of diadectid

taxonomy and a consideration of evolutionary trends within the lineage.

For the reasons outlined above, Phanerosaurus naumanni and Stephanospondylus pugnax, as

well as the unnamed Richards Spur form, are excluded from the analysis. Also excluded are

Desmatodon hollandi, Diadectes lentus, and Diadectes carinatus. D. hollandi is known from

only the holotype—a fragmentary left maxilla (CM 1938; Fig. 10) bearing only four complete

teeth and the root of a fifth (Case, 1908; Case, 1911; Berman and Sumida, 1995)—and two questionable jaw fragments from the Upper Pennsylvanian (Virgilian) deposits at El Cobre

Canyon, New Mexico (Berman, 1993). The morphology of D. hollandi is therefore poorly

known. D. lentus and D. carinatus warrant a more extensive discussion. Nothodon lentus was

described by Marsh (1878) on the basis of a fragmentary specimen collected from the Lower

Permian Abo Formation of New Mexico and possessing incomplete tooth-bearing elements, limb elements, and portions of vertebrae (Fig. 11A; Williston, 1911). In 1912, Case and Williston described a more complete skull and lower jaw from the same locality (Fig. 11A-B) and synonymized the genus Nothodon with Diadectes, and Welles (1941) described a complete right

lower jaw from the Abo of New Mexico (Fig. 11C-E). In his review of Diadectidae, Olson

(1947) referred all specimens from the Abo to D. lentus, and he claims that D. lentus is distinct

from the Texas forms—D. sideropelicus and the very large D. tenuitectes—in size and

proportions of the skull. However, D. lentus falls within the size range and proportions expected

of known D. siderpelicus specimens, and in none of the 44 characters used in the present analysis

(Appendix 3, 4) does D. lentus differ from the more well-known D. sideropelicus and

Diasparactus zenos. Following the concept of Safe Taxonomic Reduction (Wilkinson, 2003), D.

lentus is excluded from the present analysis, and further study is required to determine if it is

morphologically distinct from D. sideropelicus and D. zenos. Diadectes carinatus was described

by Case and Williston (1912) on the basis of a fairly complete skull (Fig. 12) recovered from

Abo-equivalent beds near Animas, Colorado (Olson, 1947). As with Diadectes lentus, D.

carinatus differs from D. sideropelicus in none of the characters used here, with the possible

exception of one [15]. Case and Williston (1912; fig. 3) illustrated the palate of D. carinatus

with greatly elongated internal nares, which extend posteriorly to the level of the final maxillary

tooth. In all other diadectids in which the palate is sufficiently known, the internal nares are

significantly shorter, extending at most to the midpoint of the maxillary tooth row. Until the

specimen in question (YPM 817) can be examined in more detail, the reconstruction provided by

Case and Williston (1912; fig. 3) is left in question, and D. carinatus is excluded from the present analysis.

The analysis includes ten taxa, including the outgroup Limnoscelis paludis, and 44 cranial,

dental, and postcranial characters (Appendix 3, 4). Data were obtained from the following

publications and specimens: L. paludis, from Williston (1911), Reisz (2008), and holotype skull

YPM 811 (Fig. 13); Tseajaia campi, from Moss (1972) and holotypic skull UCMP 59012 (Fig.

14); Ambedus pusillus, from the holotype MCZ 9436 (Fig. 1) and referred specimens MCZ 9438,

a complete left dentary (Fig. 3), MCZ 9439, the anterior portion of a right dentary (Fig. 4), and

MCZ 9440, the posterior portion of a left dentary (Fig. 5); Orobates pabsti, from Berman et al.

(2004), the holotype MNG 10181, a complete, articulated skeleton (Fig. 15), and referred

specimens MNG 8760, a skull with associated, disarticulated elements of the postcranium (Fig.

16), MNG 8980, a nearly complete, articulated skeleton (Fig. 17); Desmatodon hesperis, from

Vaughn (1969, 1972), Berman and Sumida (1995), the holotype CM 47654, a left maxilla (Fig.

18), and referred specimens CM47665, a partial braincase with dermal roofing elements (Fig.

19), CM 47670, a small collection containing a right lower jaw, dorsal vertebra, caudal vertebra,

and an articulated right pterygoid and quadrate (Fig. 20), CM 47677, a partial right maxilla (Fig.

21), and CM 47678, a left maxilla (Fig. 22); Diasparactus zenos from Case and Williston (1913),

UC 679, a nearly complete skeleton, and OMNH 55350, a partial left dentary bearing the entire tooth row (Fig. 23); Diadectes sideropelicus, from Olson (1947), UR 27, a complete skull, and

UC 675, a complete skull (Fig. 24); Diadectes sanmiguelensis, from Lewis and Vaughn (1965) and holotype MCZ 2989, a complete skull, several cervical vertebrae, a few incomplete ribs, a

38 partial pectoral girdle, left humerus, and left epipodium and manus (Fig. 25); Diadectes absitus, from Berman et al. (1998a; Fig. 26); and Diadectes tenuitectes, from MCZ 1035, a nearly complete skeleton (Fig. 27).

Using Paup 4.0b10 (branch and bound search; Swofford, 2002) and MacClade 4.0 (Maddison and Maddison, 2000), the analysis yielded two equally parsimonious trees (Fig. 28), each with a length of 66 steps, a consistency index (CI) of 0.818, and a retention index (RI) of 0.800. The trees differ only in the relationships of the closely related Diasparactus zenos, Diadectes sanmiguelensis, and Diadectes tenuitectes. Until further analysis can provide finer resolution, the relationships of these three taxa is presented as a polytomy within the consensus tree (Fig.

28A). As in the first analysis above, the monophyly of Diadectidae is supported here, with the node diagnosed by the following dentition-related characters: presence of heterodon dentition

[26(1)], low degree of molarization of the cheek teeth [29(1)], cheek teeth with weakly developed labial and lingual shoulders [30(1)]. To have Diadectidae diagnosed by so few characters is unfortunate, but it is no doubt related to the incomplete nature of Ambedus pusillus.

Six additional characters at the node possess a consistency index of 1.0 [10(1), 13(1), 14(1),

15(1), 28(1), 37(1)] but lack an unambiguous history because their state is unknown in A. pusillus. It is predicted that if more complete remains of A. pusillus are recovered, the number of characters diagnosing Diadectidae will increase with the inclusion of one or more of these six characters. As with the first analysis above, Ambedus is found to be the sister-taxon to all other diadectids, with Diadectes sanmiguelensis, Orobates pabsti, Desmatodon hesperis, Diadectes absitus, and a combination of Diasparactus zenos + Diadectes sideropelicus + Diadectes tenuitectes representing progressively more derived taxa in a series of nested clades.

Autapomorphies of clades and terminal taxa are provided in Fig. 28.

6.1 Taxonomic Implications

Perhaps the most significant result of the above analysis is the polyphyletic nature of those

species historically identified as members of the genus Diadectes (Fig. 28). In their description

of D. sanmiguelensis, Lewis and Vaughn (1965) list the shallow lower jaw and low labial

parapet of the dentary as diagnostic features of the species, but as demonstrated here, these

characters are primitive for Diadectidae and can no longer be regarded as autapomorphies of D.

sanmiguelensis. The authors also suggest that the holotype and only known specimen of D. sanmiguelensis (MCZ 2989) is that of a juvenile, noting that the shallowness of the jaw and the low parapet may be related to the animal’s immaturity. The examination of a large collection of isolated tooth-bearing and postcranial elements of extremely small individuals of Diadectes

(MCZ 2780)—including vertebrae in which the neural arch is not fused to the centra—refutes this suggestion. MCZ 2780 was produced from the Lower Permian Wichita of Texas; following

Olson’s (1947) referral of all Wichita Diadectes material to the species D. sideropelicus, MCZ

2780 is regarded here as a member of D. sideropelicus. Among the elements catalogued as MCZ

2780 is the anterior portion of a dentary (Fig. 29), which demonstrates that even extremely immature individuals of Diadectes possessed a deep lower jaw. Although not preserved in its entirety, it appears that the labial parapet is also tall within this specimen, and Berman et al.

(1998a) independently confirmed the presence of a parapet in juvenile specimens of Diadectes.

Another feature long regarded as reflecting a juvenile condition in Diadectes sanmiguelensis is the weakly developed molarization of the cheek teeth. Adult specimens of Diadectes sideropelicus, as well as those of Diadectes tenuitectes and Diasparactus zenos, possess transversely expanded cheek teeth that possess a central cusp flanked by well-developed labial and lingual cusps. Considerable wear is also present within the adults. Conversely, the cheek

teeth of MCZ 2780 are characterized by the presence of a central cusp flanked by weakly

developed, rounded shoulders with no wear. The teeth of D. sanmiguelensis are therefore more

similar in general morphology to those of juvenile specimens of D. sideropelicus than those of the adults, but they do show wear facets (Lewis and Vaughn, 1965). Berman and Sumida (1995) identified the lack of wear facets as a juvenile trait in diadectids, so the presence of wear facets suggests that the weakly developed molarization of D. sanmiguelensis is not related to an immature state.

Whereas it is likely that the sole specimen of D. sanmiguelensis is not fully mature, with the preserved carpus of MCZ 2989 showing only the initial stages of ossification, the shallow lower jaw, low parapet, and low degree of molarization are not related to its state of maturity; they are therefore incorporated into the current analysis. As demonstrated by the resulting phylogenetic trees (Fig. 28), D. sanmiguelensis falls well outside the other, more derived species of Diadectes.

With the current analysis removing D. sanmiguelensis from other known species of Diadectes, it is recommended that “Diadectes” sanmiguelensis be removed from the genus Diadectes and placed in the new genus Oradectes (below).

Also of interest is the relationship between Diadectes absitus, Diadectes sideropelicus,

Diadectes tenuitectes, and Diasparactus zenos, where D. absitus represents the sister-taxon to a

combination of the latter three forms (Fig. 28). As recognized by Berman et al. (1998a),

Diadectes absitus possesses a suite of features that separate it from all other members of the genus, including a shallow lower jaw, the lack of a labial parapet of the dentary, and weakly developed cheek teeth with a low degree of molarization. Its placement within the genus

Diadectes is questioned here. Within the three equally parsimonious trees produced by the current analysis, the clade containing D. absitus, D. sideropelicus, D. tenuitectes, and D. zenos is

diagnosed by three autapomorphies: 21(1), 22(2), and 28(2), whereas the clade containing the

latter three is diagnosed by eight autapomorphies in two trees [Fig. 28A, 28B; 6(1), 13(2), 14(2),

19(1), 29(2), 30(2), 31(1) and 35(2)] and by four in the third [Fig. 28C; 29(2), 30(2), 31(1), and

35(2)]. The lack of resolution at this node likely results from the incomplete nature of D. zenos,

which is scored for only 13 of the 43 characters. Based on these results, it is determined here

that Diadectes is diagnosed by: the presence of a high degree of molarization of the cheek teeth,

where the ratio of anteroposterior length to mediolateral width and dorsoventral height to

mediolateral width are both less than 0.50 [29(2)]; well-developed labial and lingual cusps of the

cheek teeth [30(2)]; a jaw articulation positioned ventral to the occlusal plane [31(1)]; and the

presence of a tall labial parapet, where the parapet is as tall or taller than the occlusal surface of

the teeth near the posterior end of the tooth row [35(2)]. With this diagnosis, the taxon described

as Diadectes absitus falls outside the genus Diadectes; it is recommended that “Diadectes”

absitus be removed from the genus Diadectes and placed within the new genus Silvadectes

(below). Also, the monospecific Diasparactus is included in the genus Diadectes, forming

Diadectes zenos.

Finally, in the most recent review of diadectid taxonomy prior to the current study, Olson (1947)

maintained separation between the two forms described from Texas, Diadectes sideropelicus and

Diadectes tenuitectes, but provided little to distinguish the forms aside from stratigraphic

occurrence and size (Fig. 30). As demonstrated by this analysis, D. sideropelicus is unique among diadectids by lacking an elongated dorsal process of the premaxilla [1(1)], and D. tenuitectes is distinguished by the presence of a highly convex lateral surface of the lower jaw

[38(1)] and a ventral shelf on the lateral surface of the lower jaw [39(1)] (Fig. 31). D. zenos is

maintained as a distinct form based the presence of greatly elongated neural spines throughout

the vertebral column [40(1)].

7 Conclusions

Phylogenetic analyses, with the recognition of Limnoscelidae as a monogeneric taxon

(Wideman, 2002), supports previous hypotheses that Limnoscelis, Tseajaia, and Diadectidae form the monophyletic group Diadectomorpha, with diadectids and Tseajaia sharing a more recent common ancestor than either does with Limnoscelis. A genus-based analysis also confirms the monophyly of Diadectidae, and it is the first to consider the interrelationships of

Diadectidae, which was found to represent a monophyletic group consisting of (Ambedus

(Orobates (Desmatodon (Diasparactus + Diadectes)))). This result is, however, refuted in part by the second and more inclusive, species-based analysis of diadectid interrelationships also presented here, which finds the genus Diadectes to be polyphyletic.

Regarding the interrelationships of diadectids, a phylogenetic analysis based on 44 cranial and postcranial features produced three equally parsimonious trees, with “Diadectes” sanmiguelensis, Orobates pabsti, Desmatodon hesperis, “Diadectes” absitus, and (“Diasparactus zenos” + Diadectes sideropelicus + Diadectes tenuitectes) representing progressively more derived taxa in a series of nested clades. These results indicate that the genus Diadectes is a polyphyletic taxon. The diadectid Diadectes is herein diagnosed by: a high degree of molarization of the cheek teeth, where the ratio of anteroposterior length to mediolateral width and dorsoventral height to mediolateral width are both less than 0.50 [29(2)]; well-developed labial and lingual cusps of the cheek teeth [30(2)]; a jaw articulation positioned ventral to the occlusal plane [31(1)]; and the presence of a tall labial parapet, where the parapet is as tall or taller than the occlusal surface of the teeth near the posterior end of the tooth row [35(2)]. It is therefore recommended that new genera be erected for both “Diadectes” sanmiguelensis and

“Diadectes” absitus; and 2) the genus “Diasparactus” is synonymized with Diadectes (see

Chapter 4: Systematic Revision).

Fig. 6. OMNH 56871, articulated left frontal and postfrontal in dorsal view (A), OMNH 56872a (B) and OMNH 56873 (C), premaxillary incisor teeth in lingual and lateral views, and OMNH 56875 (D) and OMNH56872b (E) in probable posterior, anterior, and lingual views. From Reisz and Sutherland (2001). Scale = 1 cm.

Fig. 9. Hypothesis demonstrating the monophyly of Diadectomorpha and Diadectidae. Autapomorphies of the clades and terminal taxa are as follows, with all characters listed possessing an unambiguous history: Node A (Cotylosauria): 5(1), 33(1), 35(1); Amniota: 1(1), 11(1), 24(1); Node B (Diadectomorpha): 2(1), 4(1), 18(1), 25(1), 26(1), 32(1), 36(1), 37(1); Node C: 3(1), 8(1); Node D (Diadectidae): 27(1), 30(1), 31(1); Node E: 22(1), 26(2), 28(1); Node F: 12(1); 20(1); Node G: 19(1), 22(2), 30(2), 31(2). Bootstrap and decay index values determined in Paup 4.0b10 are: Node B: 97, 4; Node C: 56, 1; Node D: 96, 3; Node E: 95, 3; Node F: 95, 3; Node G: 92, 3.

Fig. 10. CM 1938, holotype and only known specimen (a partial left maxilla) of Desmatodon hollandi in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm.

Fig. 11 (cont.). Skull (palatal view; A) and right lower jaw of Diadectes lentus in occlusal (B), medial (C), and lateral (D) views. Scale = 1 cm. Ang, angular; s.ang, surangular; art, articular; p.art, prearticular; d, dentary; spl, splenial; ant fenestra, anterior fenestra; med fenestra, medial fenestra; post fenestra, posterior fenestra; numbers indicate tooth positions. A and B from Case and Williston (1912); C-E from Welles (1941).

Fig. 12. YPM 817, partial skull of Diadectes carinatus in palatal view. From Case and Williston (1912). Scale = 1 cm.

Fig. 18. CM 47654, left maxilla and holotype of Desmatodon hesperis in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm.

Fig. 19. CM 47665, partial braincase and dermal roofing elements of Desmatodon hesperis in dorsal (A), ventral (B), and left lateral (C) views. Scale = 1 cm. b, basipterygoid process; bs, basisphenoid; d, dentary; e, exoccipital; op, opisthotic; p, parietal; pa, pila antotica; paf, parietal foramen; pl, parietal lappet; pp, postparietal; pr, prootic; ps, parasphenoid; st, supratemporal; t, tabular. From Vaughn (1972).

Fig. 21. CM 47677, anterior portion of a right maxilla of Desmatodon hesperis in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm. From Berman and Sumida (1995).

Fig. 22. CM 47678, left premaxilla of Desmatodon hesperis in lateral (A) and medial (B) views. Scale = 1 cm. From Berman and Sumida (1995).

Fig. 23. OMNH 55350, partial dentary of Diasparactus zenos in lateral (A), medial (B), and occlusal (C) views. Scale = 1 cm. From Kissel and Lehman (2002).

Fig. 24. UC 675, skull of Diadectes sideropelicus in dorsal (A), palatal (B), and left lateral (C) views. Scale = 2 cm.

Fig. 25. MCZ 2989, holotype skull of Diadectes sanmiguelensis in lateral (A) and dorsal (B) views, with the right lower jaw in lateral (C) and medial (D) views. Scale = 2 cm.

Fig. 26. MNG 8853, holotype skeleton of Diadectes absitus in dorsal view (A) and skull in (B) and lateral (C) views. Scales = 5 and 2 cm. From Berman et al. (1998a).

Fig. 27. MCZ 1035, nearly complete skeleton of Diadectes tenuitectes in left lateral view.

Fig. 28. Consensus (A) and equally parsimonious hypotheses (B-C) demonstrating the interrelationships of Diadectidae. Autapomorphies of the clades and terminal taxa as presented in Hypothesis A, with all characters listed possessing an unambiguous history: Node A: 2(1), 3(1), 6(2), 12(1), 20(1), 21(2), 22(1), 33(1); Node B (Diadectidae): 26(1), 29(1), 30(1); Node C: 25(1), 27(1), 35(1); Node D: 42(1); Node E: 17(1), 24(1), 36(1); Node F: 21(1), 22(2), 28(2); Node G (Diadectes): 6(1), 13(2), 14(2), 19(1), 29(2), 30(2), 31(1), 35(2). Bootstrap and decay index values determined in Paup 4.0b10 are: Node B: 97, 3; Node C: 97, 3; Node D: 68, 1; Node E: 84, 2; Node F: 61, 1; Node G: 96, 4.

Fig. 29. MCZ 2780, fragmentary dentary of juvenile Diadectes sideropelicus in lateral (A), occlusal (B), and medial (C) views. Scale = 1 cm.

Fig. 31. Lower jaw of MCZ 1035, Diadectes tenuitectes, in lateral (A) and anterolateral (B) views.

Chapter 4 Systematic Revision 8 Diadectidae Cope 1880a

Defined as Diadectes and all taxa sharing a more recent common ancestor with Diadectes than with Tseajaia, diadectids are those cotylosaurs diagnosed by the presence of heterdont dentition characterized by the presence of transversely expanded posterior, or cheek, teeth. The molariform cheek teeth possess a single, central cusp flanked by rounded labial and lingual shoulders in primitive members of the group; more derived taxa possess cheek teeth with an exaggerated molariform condition, with a much greater expansion transversely, as well as a central cusp flanked by well-developed labial and lingual cusps. Based on this dentition, members of Diadectidae were likely herbivorous in habit, an interpretation that was first proposed by Cope (1878a) and Marsh (1878) and maintained since (e.g., Reisz, 2006; Sues and

Reisz, 1998). Additional features that are likely diagnostic of Diadectidae are: short internal nares, where the ratio of the anteroposterior length of the internal nares to the length of the skull table is less than 33 percent; procumbent anterior teeth in the lower jaw; absence of coronoid teeth; skull height that is at least 25 percent of skull length; snout width (measured at the anteroposterior midpoint of maxillae) at least 50 percent of the width of the skull at the jaw joint; and contact between the supratemporal and the dorsal margin of the paroccipital process of the opisthotic. Due to the paucity of remains, these additional features are lacking in what is currently the most primitive known member of the group, Ambedus, but it is likely that more complete remains of Ambedus will confirm one or more of these features as additional diagnostic characters of Diadectidae.

8.1 Ambedus Kissel and Reisz 2004, p. 198

Type species Ambedus pusillus Kissel and Reisz

Ambedus is a small diadectid distinguishable from other members of the group by the presence of a shallow dentary, a relatively high maxillary and mindibular tooth count, conical anterior teeth (in contrast to the incisiform anterior teeth of all other known diadectids), and a shallow alveolar shelf supporting only shallow tooth implantation. Wear facets on the dentition suggest that the remains, despite their small size relative to all other known diadectids, are those of adult individuals, following the observations of diadectid ontogeny detailed in Berman and Sumida

(1995). The molariform cheek teeth possess a central cusp flanked by rounded labial and lingual shoulders, as in Oradectes, Orobates, Desmatodon, and Silvadectes, but they differ in that there is no constriction below the labial and lingual shoulders; instead, the labial and lingual surfaces of the molariform teeth are near vertical. Also unlike other diadectids, Ambedus lacks the labial parapet of the dentary. Ambedus is a monospecific genus, with A. pusillus its lone member. A complete description of the known remains is provided here (Chapter 1) and was published by

Kissel and Reisz (2004).

8.1.1 Ambedus pusillus Kissel and Reisz 2004, p. 198

Holotype: MCZ 9436, a nearly complete right maxilla from Clark Hill in Monroe County, Ohio;

Nineveh Limestone, Dunkard Group, Lower Permian.

Diagnosis: Same as that for the genus, this form being the only known species.

Referred specimens: MCZ 9437, a poorly preserved maxilla; MCZ 9438, a complete left dentary;

MCZ 9439, the anterior portion of a right dentary; MCZ 9440, the posterior portion of a left

dentary; MCZ 9441, a poorly preserved right dentary. All specimens are produced from the

Clark Hill site within the Nineveh Limestone.

8.2 Orobates Berman et al. 2004, p. 3

Type species Orobates pabsti Berman et al.

Orobates (Fig. 32) is distinguishable from other members of Diadectidae by the presence of teeth

on the palatine and vomerine teeth that are restricted to the posterior half of the vomer. Also in

contrast to other diadectids, in which it is near vertical for much of its length, the anterior margin

of the otic embayment in Orobates curves strongly posteroventrally at approximately 40 degrees

from the vertical for much of its length. As in the non-diadectid diadectomorphs Limnoscelis

and Tseajaia, as well as the diadectids Oradectes sanmiguelensis and presumably Ambedus, the secondary palatal shelf of the ectopterygoid and palatine is absent. The parietal foramen is located posterior to the midpoint of the parietals along the interparietal sutural contact, as in

Oradectes. Orobates possesses three maxillary teeth, unlike other diadectids, which have four.

The incisiform anterior teeth are procumbent in the lower jaw only. The molariform cheek teeth possess a central cusp flanked by rounded labial and lingual shoulders, with constriction below the shoulders to produce a spade-like outline in anterior view. This dental morphology is similar to that of Oradectes, Desmatodon, and Silvadectes, but the long axes of the molariform teeth are angled relative to the long axis of the jaw 30 to 40 degrees, a feature shared with only Oradectes.

The external iliac shelf in Orobates is positioned lower than in all other diadectomorphs, found at the base of the iliac blade. Diadectidomorphs in which the pelvis is known—Limnoscelis,

Tseajaia, and Diadectes—possess a shelf located at the iliac blade’s midheight, whereas the shelf in Silvadectes is reduced to absent. Orobates is a monospecific genus, with O. pabsti its lone

member. A complete description of several complete, articulated skeletons was provided by

Berman et al. (2004).

8.2.1 Orobates pabsti Berman et al. 2004, p. 4

Holotype: MNG 10181, a complete, articulated skeleton from the Bromacker Quarry, middle

part of the Thuringian Forest near the village of Tambach-Dietharz, central Germany; Tambach

Formation, Upper Rotliegend, Lower Permian.

Diagnosis: Same as that for the genus, this form being the only known species.

Referred specimens: Listed as paratypes by Berman et al. (2004) are: MNG 8760, a skull with

articulated anterior cervical vertebrae and associated but disarticulated elements of the

postcranial skeleton; MNG 8980, a nearly complete, articulated skeleton; MNG 11133, a jaw

fragment with five complete or partial teeth; and MNG 11134, a partial skull lacking the left

mandible. Also known are dozens of disarticulated elements that are likely attributable to this

species, all produced from the Bromacker Quarry of central Germany.

8.3 Oradectes n. gen.

Etymology.—Latin, ora, margin; dectes, biter. Refers to the ventral margin of the Meckelian

fenestra that is formed entirely by the splenial, an autapomorphy of the form.

Type species: Oradectes sanmiguelensis (Lewis and Vaughn)

Described by Lewis and Vaughn (1965) and placed in the genus Diadectes, the holotype and only known specimen of this form (MCZ 2989) is referred here to a new genus, Oradectes (Fig.

33). In Oradectes, the parietal foramen located posterior to the midpoint of the parietals along

73 the interparietal sutural contact, and the spade-like molariform cheek teeth are angled relative to the long axis of the jaw 30 to 40 degrees, as in Orobates. The incisiform anterior teeth are probumbent in the lower jaw only, a primitive feature shared with Orobates, Desmatodon, and presumably Ambedus. In contrast to Orabates but like other diadectids, the anterior margin of the otic embayment is near vertical for much of its length. As in the non-diadectid diadectomorphs Limnoscelis and Tseajaia, as well as the diadectids Orobates and presumably

Ambedus, the secondary palatal shelf of the ectopterygoid and palatine appears to be absent.

Unique among diadectomorphs and an autapomorphy of the taxon, the splenial forms the entire ventral border of the Meckelian fenestra. A complete description of the holotype and only known specimen was provided by Lewis and Vaughn (1965), but one correction is necessary. In

Lewis and Vaughn’s (1965; fig. 7) illustration of the preserved skull, they indicate the presence of an intertemporal and, immediately behind it, an unknown element labeled “?”. Examination of the specimen reveals that the elements labeled as the intertemporal and “?” actually represent the lateral lappet of the parietal, as in the well-known skulls of Orobates, Silvadectes, and the better preserved specimens of Desmatodon (e.g, CM 47665, a partial braincase and skull roof) and Diadectes (e.g., UC 1078, a partial skull of D. sideropelicus).

8.3.1 Oradectes sanmiguelensis (Lewis and Vaughn 1965, p. C13)

Synonym: Diadectes sanmiguelensis Lewis and Vaughn 1965

Holotype: MCZ 2989, a partial skeleton consisting of a complete skull with several articulated cervical vertebrae, a few incomplete ribs, a partial pectoral girdle consisting of left and right clavicles, the interclavicle, left cleithrum, and left scapulocoracoid, and the left forelimb from the

Placerville area in Fremont County, Colorado; Cutler Formation, Lower Permian.

Diagnosis: Same as that for the genus, this form being the only known species.

Attributed specimens: The holotype is the only known specimen.

8.4 Desmatodon Case 1908, p. 236

Type species Desmatodon hollandi Case

Desmatodon possesses molariform cheek teeth bearing a central cusp is flanked by rounded

labial and lingual shoulders, with constriction below the shoulders producing a spade-like outline

in anterior view, as in Orobates, Oradectes, and Silvadectes; as in Silvadectes but unlike

Orobates and Oradectes, the long axes of the teeth are perpendicular to the long axis of the jaw.

The labial parapet of the mandible is present but low, where the parapet never projects higher than the bases of the cheek teeth. The ventral border of the Meckelian fenestra is formed equally by the splenial and angular. As in Diadectes but unlike other diadectid taxa, a deep lower jaw is present, exhibiting a ratio of the dorsoventral height at the level of the coronoid eminence to the anteroposterior length greater than 33 percent. The neural spines are tall, where the ratio of neural spine height to vertebral height is greater than 40 percent. Hyposphene-hypantrum articulations are present, as in all diadectids in which the vertebrae are known except Silvadectes.

Two species are recognized within the genus: D. hollandi and D. hesperis.

8.4.1 Desmatodon hollandi Case 1908, p. 236

Holotype: CM 1938, a fragment of a left maxilla bearing four complete teeth and the root of a

fifth from Locality C of Moran (1952), near Pitcairn, Pennsylvannia; Red Knob Formation,

Conemaugh Group, Upper Pennsylvanian.

Desmatodon hollandi is known from three fragmentary specimens, the holotype and a pair of jaw fragments from El Cobre Canyon, New Mexico. It is distinguishable from Desmatodon hesperis

in the arrangement of the cheek teeth. In D. hesperis, the teeth are tightly packed together, with

little space between them, whereas those of D. hollandi are separated by gaps equivalent to at

least half the anteroposterior length of the adjacent teeth. In discussing the ontogeny of D.

hesperis, Vaughn (1972) and Berman and Sumida (1995) noted four dental features that are present in immature individuals but absent or greatly reduced within mature specimens: fewer

number of teeth; greater relative spacing between teeth to produce large gaps between teeth; first

two maxillary teeth relatively longer and more incisiform; and an absence of wear facets. The

spacing within CM 1938 could therefore be attributed to a state of immaturity, but the teeth of

CM 1938 possess significant wear facets, indicating that the specimen is from an adult animal; the spacing between teeth is therefore not a feature related to immaturity.

Referred specimens: Two jaw fragments collected in 1978 from Upper Pennsylvanian (Virgilian) beds of El Cobre Canyon, NM were identified as belonging to the same species as the holotype.

Examination of casts of these specimens (CM 8640 and CM 38044) reveals: a spade-like tooth

morphology; the long axes of the teeth are perpendicular to the long axis of the lower jaw; and between the teeth are spaces equivalent to half the anteroposterior width of the adjacent teeth.

The features support the assignment of these remains to Desmatodon hollandi.

8.4.2 Desmatodon hesperis Vaughn 1969, p. 11

Holotype: CM 47654 (formerly UCLA VP 1706), a left maxilla with complete dentition from the

Badger Creek locality near the town of Howard, Fremont County, Colorado; Sangre de Cristo

Formation, Upper Pennsylvanian.

As Desmatodon hollandi is known from only three tooth-bearing jaw fragments, knowledge of

the genus Desmatodon rests largely on the remains described as D. hesperis. Much of the

description provided for the genus above therefore applies here. D. hesperis is distinguishable

from D. hollandi in the arrangement of the molariform cheek teeth, with the former characterized

by the presence of tightly packed cheek teeth, in which there is little to no gap between

successive teeth, and the latter possessing considerable spaces between each tooth. Thorough

descriptions of the holotype and attributed specimens were provided by Vaughn (1969, 1972)

and Berman and Sumida (1995).

Referred specimens: Disarticluated skull and postcranial elements produced from the same

locality as the holotype, as documented in Vaugh (1969, 1972) and Berman and Sumida (1995).

8.5 Silvadectes n. gen.

Etymology.—Latin, silva, forest; dectes, biter. Refers to the recovery of the taxon from the

Thuringian Forest of central Germany.

Type species Silvadectes absitus (Berman et al. 1998a)

Initially described as Diadectes absitus by Berman at el. (1998a), this form is referred to a new

genus here. Phylogenetic anaylsis demonstrates that this form is more primitive than other species assigned to Diadectes, lacking the greatly expanded molariform cheek teeth bearing well-developed labial and lingual cusps, deep skull and lower jaw, and tall labial parapet of the

dentary that diagnosis that genus. Silvadectes (Fig. 34) is a medium-sized diadectid possessing

procumbent anterior teeth in both the upper and lower jaws, as in Diadectes but not Desmatodon,

Orobates, Oradectes, and possibly Ambedus (the condition in the upper jaw of Ambedus is

77 unknown). As in Oradectes, Orobates, and Desmatodon, the molariform cheek teeth possess a spade-like outline, bearing a central cusp flanked by rounded labial and lingual shoulders above a constricted crown base. The lower jaw is shallow, with the ratio of dorsoventral height at the coronoid eminence less than 33 percent the anteroposterior length of the jaw. Notable is the absence of the hyposphene-hypantrum articulations of the vertebrae, which are known in all diadectid taxa except Stephanospondylus pugnax. Unique among diadectids is the presence of a greatly expanded dorsal process of the ilium, creating a tall, broad element that possesses a dorsoventral height greater than its anteroposterior length; in all other diadectids in which the pelvis is known, the dorsal process is relatively smaller, producing an overall anteroposterior length that is greater than the element’s height. Silvadectes is a monospecific genus, with S. absitus its lone member. A complete description of S. absitus, based on a series of nearly complete, articulated skeletons, was published by Berman et al. (1998a).

8.5.1 Silvadectes absitus (Berman et al. 1998a, p. 56)

Synonym: Diadectes absitus Berman et al. 1998a

Holotype: MNG 8853, a nearly complete, articulated skeleton from the Bromacker Quarry, middle part of the Thuringian Forest near the village of Tambach-Dietharz, central Germany;

Tambach Formation, Upper Rotliegend, Lower Permian.

Diagnosis: Same as that for the genus, this form being the only known species.

Referred specimens: MNG 8747, nearly complete skull with lower jaws; MNG 7721, nearly complete, articulated postcranial skeleton; MNG 8978, nearly complete but disarticulated postcranial skeleton. All were collected from the Bromacker Quarry of central Germany.

8.6 Diadectes Cope 1878a, p. 505

Type species: Diadectes sideropelicus Cope 1878a

The genus Diadectes has received a great amount of attention within the literature, with an

abundance of skeletal material known from the Wolfcampian beds of Texas, yet no modern

diagnosis of the taxon exists. Herein, Diadectes is distinguished from other diadectids by the

presence of: cheek teeth with a central cusp flanked by well-developed labial and lingual cusps;

high degree of molarization of the cheek teeth, where the ratio of anteroposterior length to

mediolateral width and dorsoventral height to mediolateral width are both less than 0.50;

depressed jaw articulation located ventral to the occlusal plane; tall labial parapet, where the

parapet is as tall or taller then the occlusal surface of the teeth near the posterior end of the dental

series; ratio of maximum skull height to skull length greater than 50 percent; and ratio of snout

width (measured at the anteroposterior midpoint of the maxialla) to width of jaw joint greater

than 75 percent. As in Desmatodon, a deep lower jaw is present, possessing a ratio of the

dorsoventral height at the level of the coronoid eminence to the anteroposterior length greater

than 33 percent. These traits indicate that among diadectids Diadectes possessed the greatest

suite of features for processing a high-fiber diet. The vertebrae possess hyposphene-hypantrum articulations.

Olson (1947) provided a detailed description of the skull of Diadectes, relying primarily on a complete skull of the species D. sideropelicus (MCZ 1105, which is now housed in The Field

Museum, Chicago and catalogued as UR 27), but a correction should be noted here. As reviewed by Berman et al. (1992), the number and arrangement of elements of the temporal region of Diadectes has been a point of contention among authors (Fig. 35). Olson (1947; fig. 2)

and other authors (e.g., Huene, 1913) argued for the presence of an intertemporal immediately

lateral to the parietal. Berman et al. (1992) correctly interpreted this “intertemporal” as a lateral

lappet of the parietal, but their interpretation of the tabular as a reduced element is incorrect. As

demonstrated by UC 1078, a partial skull of D. sideropelicus, the tabular and supratemporal are approximately equivalent in size, subequally forming the posterlateral corner of the skull roof. A new reconstruction of the skull of Diadectes, based on D. sideropelicus, is presented here (Fig.

36). This arrangement is also documented in the well-known skulls of Orobates, Silvadectes, and CM 47665, a partial braincase and skull roof of Desmatodon (Berman et al., 1998a, 2004;

Vaughn, 1969).

The present study recognizes five species within the genus: D. sideropelicus, D. tenuitectes, D. zenos, D. lentus, and D. carinatus; for reasons outlined below, the validity of the latter two is considered tentative.

8.6.1 Diadectes sideropelicus Cope 1878a, p. 505

Synonyms: Diadectes latibuccatus Cope 1878a; Empecocles latibuccatus (Cope 1878a);

Empedias latibuccatus (Cope 1878a); Bolosaurus rapidens Cope 1878a; Chilonyx rapidens

(Cope 1878a); Empedocles alatus Cope 1878a; Empedias alatus (Cope 1878a); Diadectes

molaris Cope 1878b; Empedocles molaris (Cope 1878b); Empedias molaris (Cope 1878b);

Diadectes phaseolinus Cope 1880b; Empedias phaseolinus (Cope 1880b); Helodectes paridens

Cope 1880b; Helodectes isaaci Cope 1880b; Empedias fissus Cope 1883; Diadectes

biculminatus Cope 1896.

Holotype: AMNH 4360, a fragmentary left lower jaw bearing two complete and two incomplete

teeth, as well as vertebral fragments from the Wichita beds of Texas; Lower Permian. Olson

(1947) designated MCZ 1105, a skeleton possessing the skull, a complete series of presacral

vertebrae, complete scapulocoracoids, a clavicle, and ribs, as a neotype of D. sideropelicus.

MCZ 1105 was collected from the Wichita Group of Texas; it was transferred to The Field

Museum of Natural History since Olson (1947) and is now catalogued as UR 27.

In his review of the diadectids, Olson (1947) referred all taxa described from the Wichita beds of

Texas to D. sideropelicus. In doing so, he synonymized Empedias alatus (Cope 1878a),

Diadectes latibuccatus Cope 1878a, and Diadectes phaseolinus Cope 1880b with D. sideropelicus, but aside from this stratigraphic and geographic distinction, Olson (1947) provided no anatomical features to distinguish the species from other forms of Diadectes. In the analysis presented here, D. sideropelicus differs from all other species of Diadectes in possessing a reduced dorsal premaxillary process that does not extend posteriorly to invade the nasal.

Attributed specimens: Numerous well-preserved specimens (e.g., AMNH 4684, 4839), including mounted skeletons, from the Wichita Group (Markely, Archer City, Petrolia, and Waggoneer

Ranch formations of Lucas, 2006) of Texas.

8.6.2 Diadectes tenuitectes (Cope 1896, p. 134)

Synonyms: Bolbodon tenuitectes Cope 1896; Diadectes maximus Case 1910; Diadectoides cretin

Case 1911; Diadectes huenei Broom 1914.

Holotype: AMNH 4375, an incomplete skull lacking the mandible from the Clear Fork Group of

Texas. The nomen D. tenuitectes is based on this specimen, but its incomplete nature makes the assignment of other specimens to the species difficult. Recommended is an appeal to the

International Commission for Zoological Nomenclature that will designate MCZ 1035, a nearly complete skeleton of D. tenuitectes recovered from the Arroyo Formation (Clear Fork Group) of

Texas, as a neotype. Unlike AMNH 4375, MCZ 1035 demonstrates the features considered here

as autapomorphic for the species: highly convex lateral surface of the lower jaw; ventral shelf on

the lateral surface of the lower jaw.

Romer (1944) referred all taxa described from the Clear Fork beds of Texas to D. tenuitectes, an

assignment supported by Olson (1947). In discussing D. tenuitectes and the older, Wichita

representatives of the genus, Romer (1944) noted that the former is significantly larger, with

limb measurements exceeding those of Wichita specimens by 20 percent. In the analysis

presented here, D. tenuitectes is regarded as a large member of Diadectes distinguishable from

all other species in possessing a highly convex lateral surface of the lower jaw, which is flat to

only slightly convex in other forms, and a ventral shelf on the lateral surface of the lower jaw.

As in Diadectes sideropelicus but unlike Diadectes zenos, the external iliac shelf is well-

pronounced, extending laterally beyond the acetabulum in dorsal view.

Attributed specimens: Numerous well-preserved specimens (e.g., AMNH 4378), including

mounted skeletons, from the Clear Fork Group (Arroyo and Vale formations of Lucas, 2006) of

Texas.

8.6.3 Diadectes zenos (Case 1910, p. 174)

Synonym: Diasparactus zenos Case 1910

Holotype: AMNH 4797, a series of several posterior dorsal and two sacral vertebrae.

Diadectes zenos is distinguishable from other species of the genus by the presence of greatly

elongated neural spines, where the ratio of neural spine height to vertebral height is greater than

40 percent. Case (1910) and Williston and Case (1913) also note that the vertebrae of D. zenos

also possess relatively small centra and, within the dorsal series, short transverse processes, which do not extend beyond the edges of the zygapophyses. The external iliac shelf, as

demonstrated by UC 679, is represented by a low ridge and not as expanded laterally as that in

D. sideropelicus and D. tenuitectes. The overlying dorsal process of the ilium is also not as well

developed (e.g., not as tall) as that in other species of Diadectes.

Attributed specimens: UC 679, a nearly complete skeleton from Virgilian (Upper Pennsylvanian)

Cutler Formation of El Cobre Canyon, New Mexico; OMNH 55350, a partial left dentary

preserving the entire tooth row, and OMNH 55351 and 55352, two dorsal vertebrae, from the

Virgilian Ada Formation of Oklahoma.

8.7 Problematic Taxa Assigned to Diadectidae

8.7.1 Phanerosaurus naumanni Meyer 1860, p. 251

Meyer (1860) described P. naumanni on the basis of an articulated series of four presacral and

two sacral vertebrae; no additional remains have been assigned to the form. The vertebrae were

recovered from the Leukersdorf Formation of the Erzgebirge Basin near Zwickau, Germany.

The vertebrae are diadectid in nature (Berman et al., 2004), with greatly swollen (i.e., broad, with

zygapophyses extending laterally far beyond the centra) and tall neural arches. The neural spines are diamond-shaped in dorsal view, with the long axis oriented anteroposteriorly, as in the

German form Diadectes absitus (Berman et al., 1998a), but they are significantly shorter dorsoventrally than those of D. absitus and other known diadectids. Aside from the potentially reduced height of the neural spines, the vertebrae of P. naumanni possess no features that allow separation from other diadectids.

8.7.2 Stephanospondylus pugnax (Geinitz and Deichmueller 1882, p.

10)

Synonym: Phanerosaurus pugnax Geinitz and Deichmueller 1882

Geinitz and Deichmueller (1882) described a small collection of cranial and postcranial remains as Phanerosaurus pugnax recovered from the Lower Rotliegend Doehlen Basin near Dresden,

Germany; Stappenbeck (1905) reviewed the material and assigned it to the new genus

Stephanospondylus. Romer (1925) determined that the original and only specimen assigned to S. pugnax actually contained the remains of two distinct taxa, but the right maxilla, partial left and right mandibular rami, and a small number of disarticulated vertebrae are attributable to the nomen S. pugnax. The dentition and vertebrae are clearly diadectid, with the former possessing the spade-like outline characteristic of the teeth found in Oradectes, Orobates, Desmatodon, and

Silvadectes. The vertebrae of S. pugnax lack the anterior hypantrum and posterior hyposphene articular surfaces that are found in all diadectid species (except Diadectes absitus) in which the vertebrae are adequately known. In this respect, S. pugnax aligns with the German form D. absitus. The complete axial skeleton of Orobates, another diadectid recovered from Germany, is known, but the preservation of only articulated vertebral columns does not permit examination of the anterior and posterior surfaces of the vertebrae. Several of the vertebrae illustrated by Geinitz and Deichmüller (1882) appear to have extremely shortened neural spines, as those shown by

Phanerosaurus naumanni (Meyer, 1860), but other vertebrae appear to possess a taller spine. As with P. naumanni, further examination or more material is required.

8.7.3 Richards Spur diadectid (Reisz and Sutherland, 2001)

Reisz and Sutherland (2001) described an unnamed diadectid recovered from the Leonardian

(Early Permian) Richards Spur fissure fill locality of Oklahoma. Elements include two left and

two right frontals, a left postfrontal (collectively catalogued with one of the left frontals as

OMNH 56871), five individual incisiform teeth (OMNH 56872, OMNH 56873, OMNH 57874, and two uncatalogued specimens), and nine individual molariform cheek teeth (OMNH 56872b,

OMNH 56875, OMNH 56875, OMNH 56876, and five uncatalogued specimens). The anteroposterior length of the frontals suggests a size similar to that of Oradectes sanmiguelensis and smaller individuals of Orabates pabsti (e.g., MCZ 8980). The dentition is of the spade-like form found in Orobates and related taxa, but the known teeth are isolated elements, so their spacing and orientation within the jaw is unfortunately not known. Distinct wear facets on the dentition suggest that the remains are from adult individuals. The posterior border of the postfrontal is found significantly more posterior to the frontal-parietal suture than in other diadectids, and this feature may represent an autapomorphy of the form, but in light of the incomplete and disarticulated nature of the remains, it is maintained an unnamed taxon herein.

No remains outside of those thoroughly described by Reisz and Sutherland (2001) have been reported.

8.7.4 Diadectes lentus (Marsh 1878, p. 410)

Synomym: Nothodon lentus Marsh 1878

Nothodon lentus was initially described by Marsh (1878) on the basis of two premaxillae, at least one maxilla, limb elements, and vertebrae recovered from the Abo Formation of New Mexico

(illustrated in fig. 7 of Case, 1911). Case and Williston (1912) described a nearly complete skull

from the Abo and referred N. lentus to the genus Diadectes; Welles (1941) illustrated a complete mandibular ramus from the Abo Formation. Olson (1947) stated that the skull of D. lentus

differs in size and proportions from those of D. sideropelicus and D. tenuitectes from Texas, but

the sizes of D. lentus specimens do fit within the range seen for D. sideropelicus. In none of the

characters used in the analysis of the present study does D. lentus differ from the

stratigraphically equivalent D. sideropelicus.

8.7.5 Diadectes carinatus (Case and Williston 1912, p. 345)

Synonym: Animasaurus carinatus Case and Williston 1912

An incomplete skull (YPM 817) collected near Animas, Colorado, is the holotype of D. carinatus. As noted by Olson (1947), the published figure of the skull (Case and Williston,

1912; fig. 3) suggests the presence of greatly elongated internal nares, a primitive feature within

Diadectomorpha that would distinguish D. carinatus from all other diadectids in which that area of the skull is know. However, Case and Williston (1912) do not describe the feature in their text, so its presence is unclear. Further examination is required in order to properly assess the status of D. carinatus.

Fig. 34. Reconstruction of the skull of Silvadectes in lateral (A) and dorsal (B) views, based on MNG 8853, the holotype of Silvadectes absitus. Scale = 2 cm. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pf, postfrontal; pm, premaxilla; po, postorbital; pp, postparietal; prf, prefrontal; q, quadrate; qj, quadratojugal; soc, supraoccipital; sq, squamosal; st, supratemporal; t, tabular.

Fig. 35. Previous interpretations of the skull roofing elements of the genus Diadectes, with author(s) and year of study noted; all reconstructions illustrating dorsal view. EO, exoccipital; F, frontal; IT, intertemporal; L, lacrimal; N, nasal; P, parietal; PF, postfrontal; PM, premaxially; PO, postorbital; PP, postparietal; PRF, prefrontal; Q, quadrate; QJ, quadratojugal; SO, supraoccipital; SO-PP, supraoccipital-postparietal; SQ, squamosal; ST, supratemporal; T, tabular. Modified from Berman et al. (1992).

Chapter 5 Evolution of Diadectidae 9 Introduction

The identification of extinct herbivores relies on circumstantial evidence, including the possession of dentition adapted for crushing and grinding, or marginal teeth with labiolingually compressed, leaf-shaped, and cuspidate crowns for puncturing and shredding; short tooth rows, with foreshortening of the snout and mandible; elevation or depression of the jaw joint relative to the occlusal plane for increased mechanical advantage of the adductor jaw muscles during biting; enlargement of the adductor chambers and temporal openings, as well as deepening of the zygomatic arches and mandibular rami, to accommodate powerful adductor jaw muscles; and jaw joints suitable for complex mandibular movements. Postcranial adaptations associated with herbivory include wider and longer, barrel-shaped rib cages to house the longer and bulkier digestive tracts that are required to house large numbers of endosymbionts for the fermentative breakdown of cellulose (Hotton et al., 1997; Sues and Reisz, 1998; Reisz and Sues, 2000).

Within diadectomorpha, the basal, non-diadectid Limnoscelis and Tseajaia, with their conical teeth and slender frames, were no doubt carnivorous in habit. In contrast, all diadectids possess many of the skeletal features listed above and commonly cited as indicative of herbivory. In his initial description of Diadectes, based on maxillary and lower jaw elements, Cope (1878a) proposed that “animals belonging to this genus were, in all probability, herbivorous.” Marsh

(1878) in his description of Nothodon (now synonymized with Diadectes; see Introduction and

Literature Review) similarly noted that the form was likely “herbivorous in habit.” Authors since have consistently supported this concensus. Within the Diadectomorpha, then, is

documented the evolution of high-fiber herbivory within a lineage, but the distribution of these characters within a phylogeny has not been examined until this current study. Presented below is a phylogeny-based discussion of this evolutionary transition. The below discussion is based on

the phylogenetic hypothesis presented in Fig. 28A.

10 Evolutionary Radiation of Diadectidae

The description of Ambedus pusillus increases the total number of currently recognized diadectid

taxa to seven genera and thirteen species: Diadectes sideropelicus Cope, 1878a; Diadectes

tenuitectes (Cope, 1896); Diadectes lentus (Marsh, 1878); Diadectes carinatus (Case and

Williston, 1912); “Diadectes” sanmiguelensis Lewis and Vaughn, 1965; “Diadectes” absitus

Berman et al., 1998a; Desmatodon hollandi Case, 1908; Desmatodon hesperis Vaughn, 1969a;

“Diasparactus” zenos Case, 1910; Phanerosaurus naumanni Meyer, 1860; Stephanospondylus pugnax (Geinitz and Deichmüller, 1882), Orobates pabsti Berman et al., 2004, and Ambedus pusillus Kissel and Reisz, 2004a. As previously indicated, the affinity of the diadectid remains from Richards Spur are uncertain at this time.

With the recognition of Limnoscelidae as a monogeneric taxon (Wideman, 2002), the Permo-

Carboniferous clade Diadectomorpha (sensu Laurin and Reisz, 1995), which is generally regarded as the sister-taxon to Amniota (Gauthier et al., 1988; Laurin and Reisz, 1995), consists of (Limnoscelis(Tseajaia, Diadectidae)). If the number of species associated with each of the three diadectomorph taxa is considered, it is found that members of Diadectidae constitute the majority of diadectomorph species. Limnoscelis consists of L. paludis Williston, 1911 and L. dynatis Berman and Sumida, 1990, and Tseajaia is a monospecific genus, with T. campi Vaughn,

1964 as its only member. In contrast, diadectid species number 13, an asymmetry that suggests

an evolutionary radiation of Diadectidae. The recognition of an evolutionary radiation of species

is dependant upon comparison of sister-taxa in order to indentify a species rich clade (e.g.,

Brooks and McLennan, 2002; Guyer and Slowinski, 1993); since sister-groups are the descendants of a common speciation event and are therefore of equal age, comparing sister-taxa eliminates the possibility that one clade is more species rich relative to another clade simply as a

result of its older age. The evolutionary radiation of Diadectidae, as evidenced by the unbalanced topology produced in the present study and the asymmetry of species-richness within

Diadectomorpha (Fig. 37), is perhaps best explained by the dietary preference of diadectids.

Based on cranial, dental, and postcranial anatomy, members of Diadectidae are thought to represent the earliest known examples of vertebrates capable of processing a diet of high-fiber terrestrial plants (Hotton et al., 1997; Sues and Reisz, 1998; Reisz and Sues, 2000), including even the most primitive member of the lineage, Ambedus pusillus (this study). Among diadectomorphs, only diadectids exhibit features indicative of herbivory, and as the first terrestrial vertebrate herbivores, diadectids inhabited previously unoccupied ecological space. It is therefore hypothesized that the evolution of high-fiber herbivory in Diadectidae led to the relatively rapid radiation of species within that group, producing a clade that is markedly more species-rich than other diadectomorph taxa (Fig. 37). Given the incomplete nature of the fossil record, future descriptions of diadectomorph material will allow the testing of this hypothesis

that herbivory represented a key innovation in the evolutionary diversification of this group.

The geographic distribution of diadectomorph taxa is also greater than that of other

diadectomorphs. Limnoscelis is known from the Upper Pennsylvanian of New Mexico,

Colorado, and Nova Scotia and the Lower Permian of Colorado, New Mexico, West Virginia,

and possibly Utah, and the monospecific Tseajaia is restricted to the Lower Permian of New

Mexico and Utah (Berman et al., 1997). In contrast, diadectid remains are known from a much

94 wider geographic range, having been recovered from Europe and extensively throughout North

America (Berman et al., 1997; Berman et al., 1998a). The evolutionary radiation of Diadectidae, as best determined from the available fossil evidence, is therefore characterized by both a greater species-richness and a wider geographic distribution than those of other diadectomorph taxa.

11 Evolutionary Trends within Diadectidae

The following features within Diadectidae have often been cited as suggestive of a high-fiber diet: labial parapet of the dentary that may have supported a beak (Welles, 1941) or served as a masticatory surface for the labial margins of the maxillary cheek teeth (Berman et al., 1998b), or both; a secondary palatal shelf that may have provided an occlusal surface for the dentary cheek teeth (Olson, 1947; Berman et al., 1998b); a massive lower jaw; the depression of the jaw joint relative to the occlusal plane; deep temporal region; barrel-shaped rib cage; and transversely expanded cheek teeth (Olson et al., 1991; Hotton et al., 1997; Sues and Reisz, 1998; Reisz and

Sues, 2000). The spatulate, incisiform anterior teeth are procumbent, and the upper incisiforms occlude with the lower ones, with vertical striations present on the tooth surfaces. Such wear indicates orthal jaw movements, and the anterior teeth of diadectids likely functioned to seize and crop, an action that, since herbivores must detach portions of plant material before ingestion, is indicative of an herbivorous diet (Rybcynski and Reisz, 2001). The molariform cheek teeth are transversely expanded with anteroposteriorly shortened crowns, a morphology suitable for crushing, and heavy wear and striations oriented parallel to the long axis of the jaw suggest backward (propalinal) motion of the lower jaw at occlusion (Olson et al., 1991; Hotton et al.,

1997; Reisz and Sues, 2000). Propalinal motion is further suggested by the morphology of the jaw articulation; in a number of taxa, as outlined below, the surface of articulation on the

articular is significantly larger anteroposteriorly than that of the quadrate, allowing the lower jaw

to move back and forth during mastication.

The most basal diadectid Ambedus possesses a heterodont dentition, with simple, cone-shaped

teeth at the anterior end of the jaws followed by transversely expanded “cheek” teeth that bear a

central cusp flanked by rounded labial and lingual shoulders. This morphology is in strong

contrast to that of the non-diadected diadectomorphs Limnoscelis paludis and Tseajaia campi, where the teeth are conical throughout the jaws. The dentition of Ambedus also exhibits significant wear throughout the jaws, suggesting that the molariform teeth were surfaces that had been exposed to extensive grinding. These features argue for a diet consisting of resistant material, suggesting that Ambedus is the most primitive diadectomorph possessing a diet of high- fiber plants. Like L. paludis and T. campi, however, the lower jaw of Ambedus is relatively shallow, where the ratio of the dorsoventral height of the mandible at the level of the coronoid eminence to the anteroposterior length of the jaw less than 33%. Ambedus also shares with L. paludis and T. campi are shallow marginal tooth roots and the lack of a labial parapet of the dentary.

Tracing the evolution of characters within the present phylogenetic hypothesis (Fig. 37) reveals an evolutionary history of traits leading to more efficient oral processing within the lineage.

Related to herbivory, Node C is diagnosed by the presence of: deep marginal tooth roots, with root length greater than crown height [25(1)]; incisiform (versus conical) anterior teeth [27(1)]; and the presence of a labial parapet of the dentary [35(1)]. Node D is diagnosed by the presence of a jaw joint in which articular surface is larger than the surface of the overlying quadrate

[42(1)]. Node E is diagnosed by the presence of a secondary palatal shelf formed by the palatine and ectopterygoid [17(1)] and an anterior process of the articular [36(1)]. Node F is

96 characterized by the lack of teeth or denticles on the transverse flange of the pterygoid [22(2)] and the presence of procumbent anterior teeth in both the upper and lower jaws. Node G is diagnosed by the presence of: a deep skull [13(2)]; high degree of molarization [29(2)]; well- developed labial and lingual cusps of the cheek teeth [30(2)]; jaw articulation ventral to the occlusal plane [31(1)]; and a tall labial parapet of the dentary [35(2)].

All members of Diadectidae possess a heterodont dentition with molariform cheek teeth that bear substantial wear, suggesting that even the most primitive forms were likely high-fiber herbivores, but of note is that the phylogeny of Diadectidae presented here indicates a trend toward more efficient oral processing as the lineage evolved (Fig. 38), documenting the evolution of high- fiber herbivory from a carnivorous ancestor.

Fig. 38. Evolutionary history of traits leading to more efficient oral-processing within Diadectidae.

Chapter 6 Stratigraphic and Geographic Distribution of Permo-Carboniferous Tetrapods 12 Introduction

With its recovery from the Upper Pennsylvanian Missourian of Pennsylvania and Colorado, the

diadectid Desmatodon (D. hesperis and D. hollandi) represents the earliest known tetrapod

possessing a diet of high-fiber terrestrial plants. The remaining diadectids—all of which are

thought to have been high-fiber herbivores—include Diadectes zenos from the Upper

Pennsylvanian Virgilian and, from the Lower Permian: Ambedus pusillus, Orobates pabsti,

Oradectes sanmiguelensis, Silvadectes absitus, Diadectes sideropelicus, Diadectes tenuitectes,

Diadectus lentus, Diadectes carinatus, and Stephanospondylus pugnax, Phanerosaurus

naumanni, and Reisz and Sutherland’s (2001) unnamed diadectid from Oklahoma.

Repeated phylogenetic analyses (e.g., Gauthier et al., 1988; Laurin and Reisz, 1995; Reisz, 1997;

Kissel and Reisz, 2004a; this study) indicate that the Diadectidae forms a clade within

Diadectomorpha, which, together with the sister-taxon Amniota, constitutes the Cotylosauria.

Although some workers (e.g., Berman et al., 1992; Modesto, 1992) have argued that diadectomorphs are members of Amniota, the placement of Diadectomorpha outside of crown- group Amniota, as their sister-clade, is the more widely accepted hypothesis (Berman et al.,

1997; this study). The earliest known definitive amniotes thought to possess high-fiber herbivorous diets are the pelycosaurian-grade synapsid Edaphosaurus from the Upper

Pennsylvanina of New Mexico and West Virginia and the bolosaurid parareptiles Bolosaurus and

Eudibamus from the Lower Permian of Texas and Germany, respectively (Berman et al., 1997;

Hotton et al., 1997; Berman et al., 2000). The caseid synapsids and the moradosaurine

100

captorhinid reptiles of the upper Lower Permain are also regarded as high-fiber herbivores

(Reisz, 2006; Sues and Reisz, 1998).

Despite their presence in Upper Pennsylvanian and Lower Permian strata—as evidenced by the

synapsid Edaphosaurus, caseids (e.g., Casea and Cotylorhynchus), the bolosaurid reptiles

Bolosaurus and Eudibamus, moradisaurine captorhinids (e.g., Labidosaurikos), and diadectids— it is generally held that high-fiber herbivores were not a significant component of the terrestrial food web until the Late Permian, when a large primary consumer base was established by the anomodont synapsids (Rybcynski and Reisz, 2001; Sues and Reisz, 1998). These Upper

Permian deposits, such as those from the Upper Permian Beaufort Group of South Africa (Reisz and Sues, 2000), are thought to record the oldest, well-known example of the trophic structure of

modern terrestrial ecosystems.

Recent collecting efforts at the Bromacker locality—found in the Upper Rotliegend (Lower

Permian) Tambach Formation of central Germany—has produced a fossil assemblage that is

indicative of a modern terrestrial ecosystem. There, remains of two distinct diadected taxa,

Diadectes absitus and Orobates pabsti, are considerably abundant relative to the other taxa recovered from the site, as determined from a tabulation of the minimum number of individuals

(MNI) recovered from the site. With data based on collections (catalogued and uncatalogued) housed within the Museum der Natur, Gotha, the MNI figures from Bromacker are as follows:

Diadectidae, 12; Thuringothyris, 10; Seymouria, 4; Eudibamus, 2; caseid, 2; Dimetrodon, 2;

Tambachia, 1; trematopid, 1; varanopid, 1. This observation—that the Bromacker fauna is characterized by a relatively high number of herbivores (caseid synapsids, the bolosaurid

Eudibamus, and especially diadectids)—has led to the hypothesis that the formation of the basic trophic structure of the modern terriestrial ecosystem occurred not during the Late Permian, as

101

commonly presented, but during the Early Permian, some 40 million years earlier (Kissel and

Reisz, 2004a). Within diadectomorpha, diadectids are the most numerous taxa, suggesting that the advent of high-fiber herbivory represented a key innovation that led to a relatively rapid radiation of species within the group during the Upper Pennsylvanian (Fig. 37; this study). In order to test this hypothesis, a further examination of diadectid diversity is presented here, measured through the abundance of diadectid taxa from individual localities relative to other taxa. This current study consists of an extensive literature search of all known tetrapod-bearing

Permo-Carboniferous localities in order to document the fossil assemblages recovered from each site. When possible, lithologic character and facies analyses of the localities are also noted.

Considered as a whole, the data will lead to a better understanding of the early evolutionary history of herbivory in terrestrial tetrapods, thereby providing a more complete comprehension of vertebrate evolution and, more specifically, testing the appearance and timing of the formation of the modern ecosystem. The locality data presented below is arranged stratigraphically and, within, geographically. The taxonomy of non-cotylosaurian tetrapods follows Ruta et al. (2003) and Carroll (2009); that of synapsids follows Reisz (1986).

13 Permo-Carboniferous Tetrapod-bearing Localities

The oldest known diadectomorphs, Desmatodon hollandi from Pennsylvanian and Desmatodon

hesperis and Limnoscelis dynatis from Colorado, were collected from Upper Pennsylvanian

strata dated to the Missourian. Pre-Missourian localities are therefore not presented here. This

exclusion removes historically and scientifically significant sites from the study (e.g., Joggins,

Five Points, Mazon Creek, Florence, Linton, Nyrany), but it is justified on the basis that the

102

current study is focused on the distribution and relative abundance of diadectomorphs. Portions

of the below work was presented in Kissel and Reisz (2004b).

13.1 Missourian

The Badger Creek locality of Fremont County, Colorado is found within the Sangre de Cristo

Formation, near the town of Howard (Sumida and Berman, 1993). The Sangre de Cristo

Formation is approximately 2933 m thick (Vaughn, 1972), with the fossil-bearing site located

approximately 442 m above the base of the formation, as defined by Brill (1952). The vertebrate

remains are produced from a meter-thick, lens-shaped black shale unit—designated as part of

‘Interval 300’ by Brill (1952)—that is thought to represent a pond deposit, perhaps an oxbow

lake that was present within the general system of the stream channels preserved within this part of the formation; in addition to the lenticular shape of the bed, the presence of palaeoniscoid fish scales and small pelecypods further suggests an aquatic origin of the deposit (Vaughn, 1972).

The recognized age of the Badger Creek locality is based on the vertebrate assemblage that it

produces (Vaughn, 1969a). With the exception of some aistopod vertebrae and osteoderms and

some palatal and anterior limb elements of a small temnospondyls, the vertebrate remains are

disarticulated, although they are found in close association (Vaughn, 1969a). Actinopterygian

scales are found in patches, indicating the fishes were resident in the pond, and articulated

vertebrae and osteoderms of the aistopod Coloraderpeton brilli suggest residency, too. The

incomplete, disarticulated remains of nearly all other taxa indicate that they were transported to

the site prior to burial, perhaps from the flooding of adjacent streams, except possibly

Desmatodon hesperis and Triheacaton howardinus; remains of an individual of D. hesperis were

found in close association, and a nearly complete, articulated skeleton of T. howardinus were

recovered at the site (Vaughn, 1972). Taxa reported from the site are: a xenacanth shark; at least

103 one actinopterygian; indeterminate temnospondyls including a possible trimerorhachid, dissorophoid, dendrepetontid, and a fourth form; an “anthracosaur”; the lepospondyls

Triheacoton howardinus and Coloraderpeton brilli; the diadectomorphs Limnscelis dynatis and

Desmatodon hesperis; and at least five synapsids, including an ophiacodontid, a sphenacodontine, a “haptodont”, and the edaphosaurids Ianthasaurus sp. and a possibly new form (Berman and Sumida, 1990, 1995; Sumida and Berman, 1993; Vaughn, 1969a, 1972). In addition to the vertebrate taxa, other fossils recovered include the remains of poorly preserved plant fragments, including carbonized wood fragments and impressions of Calamites, shells of small bivalves, and parts of carapaces of the conchostracan Cyzicus (Vaughn, 1969a, 1972).

The Danville locality of Illnois is a now exhausted bone pocket found on the Vermillion River; it is found within a blackish shale unit of the Upper Pennsylvanian McLeansboro Formation (Cope,

1875; Romer and Price, 1940; Reisz, 1986). Vertebrate remains produced near Danville were recovered from beds found stratigraphically below the Shoal Creek Member of the Bond

Formation. The Shoal Creek has been correlated with the Winterset Limestone, which lies somewhere near the middle of the Missourian Series, thereby supporting a Missourian age for the Danville fossils (DeMar, 1970). Taxa reported from the site are: the chondrichthyans

Orthacanthus sp. and Janassa linguaeformis; the dipnoans Ceratodus vinslovii, Ceratodus paucicristatus, Ctenodus fossatus, Ctenodus gurleyanus, Conchopoma arctata; four distinct sarcopterygian fishes; the “anthracosaur” Cricotus heleroclitus; the synapsids Clepsydrops collettii and Clepsydrops vinslovii (Cope, 1875, 1877a, 1877b; Carroll, 1988; DeMar, 1970;

Reisz, 1986; Romer, 1961; Romer and Price, 1940).

The Garnett locality of Anderson County, Kansas is found in the Rock Lake Shale Member of the Missourian Stanton Formation (Laurin, 1993). The site has produced a rich assemblage of

104 plant (macrofossils, ovules, and miospores), invertebrate (arthropods, molluscs, brachiopods, corals, bryozoans, and foraminifera), and vertebrate remains (Reisz and Berman, 1986), with at least 100 species of fossils recognized, including 39 megaplant, 47 palynomorph, five arthropod, and nine vertebrate species, representing the most diverse Pennsylvanian terrestrial flora and fauna known from North America (Reisz et al., 1982). Winston (1983) provides a detailed treatment of the flora preserved at Garnett. Most of the vertebrate remains are those of terrestrial reptiles, and the Garnett synapsid fauna represents the most abundant and diverse known for the

Pennsylvanian. The best known and most common amniote from the site, however, is the diapsid Petrolacosaurus kansensis (Reisz et al., 1982). The fossil assemblage at Garnett was preserved as a result of the gradual flooding of a stream valley during a regressive-transgressive sequence (Reisz and Berman, 1986), with the sediments at the locality representing a probable stream valley or paleochannel fill. Taxa reported from the Garnett locality are: a hybodont chondrichthyan; the sarcopterygian fishes Synaptotylus newelli and a possible large sarcopterygian; the temnospondyls Actiobates peabodyi and a trematopsid; the “anthracosaur”

Hesperoherpeton garnettens; the reptiles Petrolacosaurus kansensis and a probable protothryridid; and the synapsids Ianthasaurus hardestiorum, Xyrospondylus ecordi, Haptodus garnettensis, ophiacodont cf. Ophiacodon, and Ianthodon schultzei (Foreman and Martin, 1988;

Kissel and Reisz, 2004b; Laurin, 1993; Maples and Schultze; 1988; Modesto and Reisz, 1990;

Reisz and Berman, 1986; Reisz et al., 1982; Wilson, 1989; Winston, 1983).

A single limb bone of a reptile was reported from the Locality D of Moran (1952), which is found near the town of Jewett, Ohio. The site is located in the Ewing limestone, a unit that occurs near the middle of the Pittsburgh red shale, and it is possible that the fossiliferous horizon corresponds to that of Locality C near Pitcairn, Pennsylvania, the type locality of the diadectid

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Desmatodon hollandi. The Locality D material is now lost and can therefore be regarded as only indeterminate ?reptilian remains (Romer, 1952).

The Pitcairn locality in Pennsylvania (Locality C of Moran, 1952) is located within the Red

Knob Formation, approximately 100 m below the base of the Pittsburgh coal, near the middle of the Conemaugh Group. The site represents the oldest known tetrapod-bearing locality of the

Conemaugh. Taxa recovered are: the temnospondyl Eryops sp., the diadectid Desmatodon hollandi, and a synapsid assigned to Edaphosaurus? raymondi (Berman and Sumida, 1995; Case,

1908; Kissel and Reisz, 2004b; Moran, 1952; Reisz, 1986; Romer, 1952, 1961).

Locality 1 of Moran (1952) is located in an abandoned, now-filled quarry located less than 3 km from the Carnegie Museum of Natural History, Pittsburgh, on the east side of Soho Street, 300 to

500 m north of Fifth Avenue. The fossils were produced from the Pittsburgh Limestone, a fresh- water limestone unit of the Conemaugh Group located 12 m below the base of the Pittsburgh

Coal. Taxa reported from the site are: the chondrichthyans Agassizodus variabilis and Dittodus sp.; the sarcopterygian fishes cf. Ectosteorhachis nitidus and Sargenodus cf. S. periprion; the actinopterygian ?Amblypterus stewarti; the temnospondyls cf. Saurerpeton obtusum and Eryops avinoffi; the lepospondyls Diploceraspis conemaughensis, Lysorophus dunkardensis,

Megamolgophis agostinii, and a Diplocaulus-like form; in addition to the vertebrate fossils, worm tubes and the remains of ostracods were also recovered (Moran, 1952; Romer, 1952).

The quarrying of sand and shale deposits from a locality on the east side of McKnight Road near

the junction of Brown’s lane, about 9.5 km north of Pittsburgh, Pennsylvania, produced several, isolated fossil remains of the ophiacodontid Clepsydrops? magnus. Stratigraphically, the

sandstone excavated here is positioned just above the Ames limestone, suggesting that it pertains

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to the upper part of the Conemaugh Group and possessing a latest Missourian to earliest

Virgilian age (Romer, 1961). No other taxa were recovered from the site.

13.2 Virgilian

Virgilian deposits in Jasper County, Illinois have yielded the remains of chondrichthyans,

dipnoans, and tetrapods. Most of the tetrapod fossils are preserved in a 0.5 m interval of cross-

bedded siltstones, sandstones, and shales that overlies a freshwater limestone deposit that

contains abundant remains of xenacanth sharks and dipnoans. The limestone grades into the

overlying clastic units, and it is thought that the tetrapod remains were preserved in pond margin deposits of deltaic origin. The synapsid Milosaurus mccordi, known from five specimens

produced from the site, represents the only tetrapod identified from the Jasper County locality

(DeMar, 1970; Reisz, 1986). DeMar (1970) refers M. mccordi to Varanopidae, but Reisz (1986)

regarded it as “Pelycosauria” incertae sedis.

Laminated limestone beds exposed in a quarry located near Hamilton, Kansas have yielded a

diverse assemblage of well-preserved plant, invertebrate, and vertebrate fossils that represent the

remains of terrestrial (insects, myriapods, and amniotes), freshwater (ostracodes), brackish or

euryhaline (ostracodes, eurypterids, spirorbids, and fish), and marine (brachiopods and

echinoderms) organisms (Cunningham et al., 1993). The locality is found in the Topeka

Limestone of the Middle Virgilian Shawnee Group (Foreman and Martin, 1988). As at Garnett,

the sediments of the quarry are interpreted as a stream valley or paleochannel fill that was

deposited in a tidal environment during a transgression (Cunningham et al., 1993).

Trimerorhachid, dissorophid, and eryopid temnospondyls are known from the site, and amniote

fossils recovered from the site, although rare, include the remains of six taxa: a new, undescribed

107 species of eureptile, the diapsid Spinoequalis, and among synapsids the varanopid

Archaeovenator hamiltonensis, an indeterminate large ophiacodontid and edaphosaurid, and a new, undescribed small ophiacodontid (Reisz, 1988; Reisz and Dilkes, 2003; Schultz and Chorn,

1988). Most of these forms are known from only a single specimen, with the exception of the eureptile, which is known from at least four specimens (R. Reisz, pers. comm.).

The Topeka locality of Kansas preserves a small assemblage of tetrapods. Channel deposits within the White Cloud Member of the Upper Virgilian Scranton Shale contain conglomerates that are rich in fragmentary and disarticulated vertebrate remains. The local facies consists of conglomerates formed of claystone pebbles cemented with calcite, carbonized plant debris, fragments of bone, and marine invertebrates. The conglomerates are thought to have formed within a fluvial channel of a prograding deltaic sequence. Marine invertebrates and vertebrates mixed with freshwater vertebrates suggest that the channels were estuarine with periodic saltwater-wedge encroachment. Whereas some of the fossils possess visible signs of wear from transport, others are well preserved. The vertebrate fauna is largely aquatic, but some terretrial tetrapods have been recovered (Foreman and Martin, 1988). Taxa recovered from the site are: hybodonts the chondrichthyans assignable to the genera Venustodus, Petalodus, Campodus,

Janassa, Orodus, as well as the remains of hybodonts, a xenacanth, and an elasmobranch; the sarcopterygians Sagenodus, Gnathorhiza, and a unidentified coelacanth; palaeoniscoid actinopterygians; an unidentified “microsaur” lepospondyl; and the synapsid Edaphosaurus

(Foreman and Martin, 1988).

The Robinson locality is found just northeast of the town of Robinson, Brown County, Kansas.

The fossiliferous horizon is composed almost entirely of densely packed stromatolites that lie between two shales, and it is located in exposures of the Soldier Creek Shale Member of the

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Upper Virgilian Bern Limestone (Wabaunsee Group), which overlies the Scranton Shale, the unit

that produced the Topeka locality. Although it has been suggested that shallow marine conditions existed at the site during time of deposition, it has also been argued that the

cyanobacteria of the stromatolites grew in an environment of mixed fresh and marine water,

either a lagoon or a bay (Foreman and Martin, 1988). Like the Middle Virgilian Hamilton fauna,

the Robinson fauna is dominated by aquatic taxa, with only a few specimens of terrestrial forms

present. Common elements of the Robinson assemblage include the remains of the dipnoans

Sagenodus copeanus and Gnathorhiza sp. and, to a lesser extent, the acanthodian Acanthodes sp.,

the temnospondyl cf. Playhystrix, an indeterminate trimerorhachid temnospondyl, the

lepospondyl Diplocaulus sp., and an indeterminate lepospondyl. The amniote fauna consists of

two taxa, a eureptile known from an isolated humerus and an indeterminate synapsid known

from a pterygoid (Schultze and Chorn, 1988; Kissel and Reisz, 2004b).

El Cobre Canyon is located approximately 8 km northwest of the village of Abiquiu, Rio Arriba

County, New Mexico (Berman, 1993). Berman (1993) reports the identification of 17 taxa from

El Cobre Canyon, with the fossil remains produced from the Cutler Formation redbeds of the

canyon floor. The age of the Cutler strata exposed in the canyon has long been debated, with

assignments ranging from the Middle Pennsylvanian Desmoinesian to the Early Permian

Wolfcampian. Based on the biostratigraphic information provided by two floral taxa,

Alethopteris serlii and Neuropteris scheuchzeri, Fracasso (1980) argued for an Upper

Pennsylvanian Missourian assignment, but Berman et al. (1997), while acknowledging a Late

Pennsylvanian age, suggested that the beds of the canyon floor are latest Virgilian in age.

Anamniote tetrapods include Chenoprosopus cf. C. milleri, Aspidosaurus novomexicanus,

Platyhystrix rugosus, Anconastes verperus, an indeterminate embolomere, and the

diadectomorphs Limnoscelis paludis, Diasparactus zenos (herein referred to the genus Diadectes

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to form Diadectes zenos), and Desmatodon aff. D. hollandi. The amniote assemblage produced

from the canyon is dominated by synapsids, with seven taxa recognized from the locality, the

ophiacodontids Ophiacodon navajovicus and Baldwinonus trux, the varanopids Aerosaurus

greenlorum and Ruthiromia elcobriensis, the edaphosaur Edaphosaurus cf. E. novomexicanus,

the sphenacodontid Sphenacodon ferox, and the enigmatic Nitosaurus jacksonorum (Berman,

1993; Berman et al., 1992; Fracasso, 1980; Reisz, 1986). The only reptile identified from El

Cobre Canyon is the probable eureptile Chamasaurus dolichognathus (Berman, 1993). Of the

fossil remains recovered from El Cobre Canyon, those of O. navajovicus are the most common

(REISZ 1986). As at the Ada locality of Oklahoma (Kissel and Lehman, 2002), the sequences

preserved at El Cobre Canyon are thought to represent meandering stream deposits, with thin,

irregular calcareous beds of the mudstone units likely representing caliche horizons, indicating

that the climate during the time of deposition was semi-arid (Fracasso, 1980).

The vertebrate fossils of the Kinney Brick locality are recovered from the Pine Shadow Member

of the Wild Cow Formation in Bernalillo County, New Mexico. Based on fusulinids, the Pine

Shadow Member is assigned an early Virgilian age, and approximately 28 m of the upper part of

the member are exposed in the quarry. The fossils, which are among the oldest tetrapod fossils from New Mexico, are produced from the lowermost 0.5 m of shale and shaly limestone above the micritic limestone that floors the quarry. Evidence for both fresh- and salt-water environments are preserved at the site, and it is probable that the environment was periodically both saline and fresh water (Hunt et al., 1992). Berman (1973) suggested that Lafonius remains

had been washed into the saline Kinney lagoon during a period of peak runoff from a stream.

Although both trimerorhachids and dissorophoids may have been tolerant of high-salinity waters,

the rarity of anamniotic tetrapods at the site suggests that they were washed into a saline lagoon

(Hunt et al., 1992). The anamniote assemblage preserved at the quarry includes at least three

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taxa that are at the same level of ontogenetic development (late larval stage), and three of the

anamniote specimens include gill-rakers, which indicate planktonic feeding. These two

characteristics of the assemblage suggest a specialized environment that either existed in the

lagoon or was washed into the lagoon (Hunt et al., 1992). Tetrapods recovered from the site in

the temnospondyls Lafonius lehmani, an amphibamid, a saurerpetontid, and an indeterminate

form. The tetrapod taxa only represent approximately one percent of the vertebrate specimens

from the site; the remaining specimens are fishes (Hunt et al., 1992).

The most recently reported Pennsylvanian tetrapod-bearing locality, OMNH V1005, is located

within the Virgilian Ada Formation of Seminole County, Oklahoma (Kissel and Lehman, 2002).

The fossiliferous exposure is interpreted as overbank (floodplain) deposits of a meandering

stream system, and it has produced the remains of six tetrapod taxa, including those of the

temnospondyl ?Eryops sp., the diadectid Diasparactus zenos (synonymized herein with the

genus Diadectes to form Diadectes zenos), two indeterminate forms known only from jaw fragments, and the synapsids Ophiacodon cf. O. mirus and an indeterminate sphenacodontian.

Although the sphenacodontian is known from only two elements, a right dentary and the distal

end of a right femur, approximately 90 percent of the 186 specimens identified from OMNH

V1005 are assigned to Ophiacodon cf. O. mirus. Taphonomic evidence indicates that the fossil

material represents an allochthonous assemblage transported to the site by low-velocity currents

prior to burial, and the presence of paleosols containing dispersed pedogenic carbonate nodules

suggests a semi-arid or subhumid climate during the time of deposition of the Ada fossil

assemblage (Kissel and Lehman, 2002).

Romer (1937) described the remains of a synapsid, the ophiacodontid Stereophallodon

ciscoensis, that were collected approximately 6.5 km south-southeast of Windthorst, Clay

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County, Texas. The specimen, MCZ 1535, consists of skull fragments and portions of six

vertebrae. It was produced from the Pueblo Formation of the Cisco Group, thereby establishing

it as the earliest known synapsid from Texas, but specific locality data was unfortunately not provided by Romer (1937). Conflicting ages have been reported for the Pueblo Formation, with assignments ranging from the Late Pennsylvanian (Reisz, 1986) to the Early Permian

Wolfcampian (Hentz, 1989). No other fossil remains were described from the site.

The Halgaito Shale of Utah has produced a diverse assemblage of vertebrates. All material reported by Vaughn (1962) was recovered from the Halgaito tongue of the Cutler Formation in

Lime Creek Valley and near John’s Canyon of San Juan County. The known fossils from the

Halgaito tongue are restricted to stream deposits and were found in lenses of channel conglomerates or in cross-bedded sandstones immediately above, below, or at the lateral edges of the conglomerates. Frede et al. (1993) and Sumida et al. (1999) reported the presence of additional taxa from the Halgaito Shale. Vaughn (1962) referred to the age of the Halgaito tongue as Wolfcampian, but Sumida et al. (1999) indicate that the Elephant Canyon Formation, which is assigned a Virglian age based on the fusulinid and conodont assemblages that it produces, interfingers with the Halgaito Shale, supporting a Virgilian age for the latter. Except

for the elements of the lower jaws and an instance of two limbs bones, articulated elements are

not found in the conglomerates. The cross-bedded sandstones produced larger pieces and occasionally articulated vertebrae and other elements (Vaughn, 1962). Fishes known are the chondrichthyan Xenacanthus aff. X. texensis, the sarcopterygian Ectosteorhachis aff. E. nitidus,

and possible actinopterygians. Tetrapods include the temnospondyls Eryops sp. and Platyhystrix

cf. P. rugosus, a possible nectridean lepospondyl, the diadectomorphs Diadectes sp. and possibly

Limnoscelis, a possible araeoscelid reptile, and the synapsids Ophiacodon cf. O. navajovicus,

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Ophiacodon sp., Edaphosaurus sp., Sphenacodon sp., and indeterminate sphenacodontids (Frede et al., 1993; Sumida et al., 1999; Vaughn, 1962).

The Elm Grove locality of West Virginia is found along a road cut on Interstate Highway 70, near the town of Elm Grove. The fossiliferous horizon is Limestone “B” of the Pittsburgh

Formation of the Monongahela Group (Berman, 1979), which is considered Virgilian in age

(Berman et al., 1997). The deposit preserved at the Elm Grove locality is interpreted as a meander cutoff channel that filled very slowly (Lund, 1972). Taxa known from the locality are: the temnospondyls Edops sp.; the lepospondyls Diploceraspis burkei and Lysorophus dunkardensis; and the synapsid Edaphosaurus colohistion (Berman, 1979a; Lund, 1972, 1975).

Locality 3 of Moran (1952) is found within an outcrop just north of Owl Run, one and one-half miles northeast of Sistersville, West Virginia. The fossils are produced by a light gray limestone that lies about 7.5 m below the Uniontown coal and is part of the Uniontown limestone. Taxa recovered from the site are: the actinopterygian ?Amblypterus stewarti and the lepospondyl

Lysorophus dunkardensis (Moran, 1952; Romer 1952).

Kounova is found in the Czech Republic approximately 55 km northwest of Prague in the

Rakonitz coal basin. Fossil material recovered at this locality is produced from a single coal mine and found in blocks of a shaly coal similar to the cannel coals at Linton and Five Points in

North America. The flora indicates a Stephanian age very close to the Permo-Carboniferous boundary; thus, the fossils from Kounova are latest Virgilian in age. The sediments at Kounova suggest deposition in the bottom of a quiet pool, and the environment seems to have been that of a coal-swamp region. Whereas remains of fish and aquatic non-amniote tetrapods are abundant in the Kounova sample, those of terrestrial tetrapods are rare (Romer, 1945). Anamniotes include Memonomenos ? simplex, Onchiodon ? foveolatum, Dawsonia polydens, and the

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lepospondyls Ophiderpeton vicinum and Sparodus crassidens. Two amniote taxa have been

identified from the site, and both are members of Synapsida. The edaphosaurid Edaphosaurus mirabilis is known from a fragment of a dorsal vertebra, and the sphenacodont Macromerion? schwarzenbergii is known from a nearly complete right maxilla, the interorbital region of a skull roof that includes the frontals and fragments of the prefrontal and postfrontal, and a left pelvic girdle (Reisz, 1986).

A partial, disarticulated ophiacodontid synapsid skeleton collected from an Upper Stephanian

(Upper Virgilian) deposit near Autun, France was described by Gaudry (1880). The specimen, which consists of a partial maxilla, the anterior halves of both mandibles, thirteen vertebrae, a clavicle, the interclavicle, scapular elements, and possibly a humerus and an ulna (Romer and

Price, 1940; Reisz, 1986), was designated as the holotype of Stereorhachis dominans. Other taxa recovered from the Autun locality include a chondrichthyan, an acanthodian, actinopterygians, two lepospondyls, and a temnospondyl (Maples and Schultze, 1988). Unfortunately, the extensive literature search conducted for this current study was unable to produce a detailed account of the locality, its precise age, and the nature of its sediments.

13.3 Wolfcampian

In the Placerville area of Fremont County, Colorado, the Cutler Formation crops out on both

sides of the San Miguel River for 6.5 km upstream and the same distance downstream from the

town of Placerville. The vertebrate fossils have been recovered from 14 localities in this area,

and they are all produced from finer clastic units that contain mudcracks and raindrop and trackway impressions. The age of the vertebrate fauna is Early Permian, comparable to that of

part of the Dunkard Group and part of the Wichita Group of the United States and the Autunian

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and Lower Rotliegend of Europe (Lewis and Vaughn, 1965). The following taxa list is from

Lewis and Vaughn (1965). Recovered from the site are: the temnospondyls: Eryops cf. E.

grandis and Platyhystrix rugosus; a seymouriamorph; the diadectomorphs Limnoscelops

longifemur and Diadectes sanmiguelensis (referred herein to the new genus Oradectes); a

possible captorhinid reptile; and the synapsids Mycterosaurus smithae, Ophiacodon sp.,

Haptodus baylei, and an indeterminate form (Lewis and Vaughn, 1965; Reisz, 1986).

A number of localities are known from the Abo Formation of New Mexico; with the exception of

one site, the Pecos River Valley locality, all of the Wolfcampian sites in New Mexico are found

within the Abo. Following Lucas (2006), the Abo Formation is considered Wolfcampian in age

and equivalent with the lower Wichita Group in Texas. First reported by Vaughn (1969), the

Tularosa Locality consists of several vertebrate-bearing fossil sites found along a 20 km long

northwest-southeast trend along the western escarpment of the Sacramento Mountains, near the

town of Tularosa. The fossil remains are produced from a zone of interfingering between the

uppermost units of the marine Laborcita Formation, which thickens to the northwest,

representing open-marine conditions, and the lowermost strata, which are interpreted as

terrestrial flood-plain deposits, of the Abo Formation to the southeast and east. Specifically, the fossiliferous horizon originates from a nodular layer in the uppermost Laborcita Formation and extends southward into stream-channel deposits in the lowermost Abo Formation. Based on the invertebrate remains recovered from the Laborcita Formation, the Tularosa Locality is considered Wolfcampian in age. The vertebrate remains from this site consist mainly of isolated elements, although a large, partial skull and seven articulated dorsal vertebrae with ribs of a dissorophid were recovered (Berman, 1993). The following list of taxa is from Berman (1993): a xenacanth chondrichthyan; the acanthodian Acanthodes sp.; at least one type of actinopterygian; a sarcopterygian fish; the temnospondyl Platyhystrix cf. P. rugosus, as well as a probably new

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dissorophid and a form similar to Edops; and the synapsids Ophiacodon sp., Edaphosaurus cf. E. novomexicanus, Sphenacodon cf. S. ferox, and Sphenacodon sp.

Most of the fossils from Rio Arriba County, New Mexico have been recovered from the area near the small village of Arroyo de Agua. Fossils recovered from Arroyo de Agua are predominantly known from seven bone beds or quarries, the Anderson Quarry, Baldwin

Bonebed, Camp Quarry, Miller Bone Bed, Quarry Butte Locality, VanderHoof Quarry, and

Welles Quarry, which are discussed in more detail below. Langston (1953a) interpreted the deposits at most of these sites as pond or lake deposits, but recent facies analyes of the Arroyo de

Agua sites suggest that the fining-upward, U-shaped, mixed-fill units of the quarries and bonebeds are proximal remnants of seasonally active (ephemeral) crevasse-channel deposits that acted as small ponds in the later stages of the channel fill (Berman, 1993).

The fossiliferous section of the Anderson Quarry, which is at least 70 m stratigraphically above the Welles Quarry, is a large pocket of light gray shale that is several feet thick and possesses thin lenses of cross-bedded sandstone. Several lightly colored marl layers near the top of the section have yielded broken, heavily encrusted pelycosaur elements. The depositional environment represented at the Anderson Quarry was similar to that at the Welles Quarry

(Langston, 1953a). The Anderson site has produced the remains of the temnospondyl Eryops grandis, a Pantylus-like lepospondyl, the diadectid Diadectes sp., and the synapsids Ophiacodon sp. and Sphenacodon cf. S. ferocior (Berman et al., 1988; Langston, 1953a).

The Baldwin Bonebed is located approximately 2.4 km northwest of the confluence of Salitral

Creek and the Rio Puerco at Arroyo del Agua. The sediments consist of a dark to light gray pocket of a highly jointed, fine claystone that lacks the micaceous character and lamination of the deposit at Welles Quarry. Although small, the bonebed produces many vertebrate remains at

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one or two levels through a thickness of 0.6 m, and the vertebrate assemblage resembles that recovered from the Quarry Butte site (Langston, 1953a). Taxa include: the temnospondyls

Chenoprosopus milleri, Eryops grandis, Zatrachys serratus, Platyhystrix rugosus; the diadectid

Diadectes lentus, and the synapsids Ophiacodon mirus and Sphenacodon ferox (Langston,

1953a).

The fossils of the Camp Quarry, UCMP V-2814, were produced from a soft, brick-red clay- siltstone 38 m below the top of the butte (Langston, 1966). Most of the fossil material is well preserved, with only minor crushing, and the Camp Quarry represents one of the few sites in

New Mexico that produces articulated skeletons. The presence of articulated and partly associated skeletons suggests rapid burial, and deposition likely occurred on a floodplain

(Langston, 1953a). The most common animal recovered from the site is the small synapsid

Aerosaurus wellesi (Langston, 1953a; Langston and Reisz, 1981). Taxa recovered from the site are: the temnospondyls Eryops grandis, Zatrachys serratus, and Broiliellus novomexicanus; the

diadectomorphs Limnoscelis sp. and Diadectes sp.; and the synapsids Aerosaurus wellesi,

Ophiacodon mirus, Edaphosaurus novomexicanus, and Sphenacodon ferox (Langston, 1953a,

1966; Reisz, 1986; Wideman, 2002). Near the Camp Quarry were produced a large collection of

lepospondyl remains described as Stegotretus agyrus by Berman et al. (1988).

The Welles Quarry, UCMP V-3528, consists of alternating dark red and gray-banded shale

underlying several feet of brown micaceous clay and siltstones of varying coarseness. Small,

spherical carbonate concretions are present in the marl layers of the lower portion of the exposed

section. The base of the fossiliferous section is stratigraphically 6 to 9 m below the horizon of

the Camp Quarry. The fossil material is slightly crushed but well preserved and typically

isolated and rarely concentrated, with the specimens consisting of primarily skulls, jaws, anda

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few articulated vertebrae and ribs. The material produced from the marl layers consists of

disarticulated postcranial elements that are encrusted with carbonate and oxide concretions

(Langston, 1953a). Taxa recovered from the site include: the chondrichthyan Xenacanthus sp.; the actinopterygian ?Progyrolepis; the temnospondyls Chenoprosopus milleri, Eryops grandis,

Zatrachys serratus, and Platyhystrix rugosus; the diadectomorph Diadectes lentus; and the

synapsids Ophiacodon mirus and Sphenacodon ferox (Langston, 1953a).

The VanderHoof Quarry, UCMP V-2843, is found approximately 150 yards from the Welles

Quarry, and it is similar to the Welles Quarry in all major sedimentary and structural features.

The section is about 3 m thick, and overlying it is a medium-grained white cross-bedded

sandstone that is not present at the Welles site. Although rare, vertebrate fossils recovered from

the VanderHoof Quarry are well preserved and lack concretionary encrustations, and

fragmentary remains of all tetrapod species recovered from the Welles Quarry have been

produced (Langston, 1953a).

The Quarry Butte site, UCMP V-3529, is generally similar in lithology to that of the Welles and

VanderHoof quarries. All tetrapod species recovered from the Welles Quarry, except Zatrachys

serratus, are also found at the Quarry Butte locality, but skulls are rare (Langston, 1953a).

UCMP V-2844 refers to scattered fossil remains found on the valley floor east of Loma Salazar.

Stratigraphically below the Camp Quarry, it has also produced the same vertebrates as the

Welles Quarry (Langston, 1953a).

Exposures of the Abo Formation are found along the walls of Canyon San Diego, on both sides

of the Jemez River, from a point 10 km north to about 15 km south of Jemez Springs, with fossil

producing localities found in the lower levels of the formation and distributed within the area of

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2 km north to 12 km south of Jemez Springs. The Johnson, Harvard, and Spanish Queen Mine

localities of Langston (1953a, 1953b) are found in this area. The Abo Formation of Jemez

Springs is considered Wolfcampian in age (Berman, 1993). The following list represents taxa

recovered from the Jemez Springs area: the chondrichthyan Xenacanthus sp.; the sarcopterygian

Gnathorhiza sp.; the lepospondyl Diplocaulus sp.; the “anthracosaurs” ?Archeria and an

indeterminate embolomere; the temnospondyls Trimerorhachis sandovalensis, Trimerorhachis

sp., Eryops sp., Platyhystrix sp., and Zatrachys sp.; the diadectomorph Diadectes sp., and the synapsids Sphenacodon ferocior, Sphenacodon sp., Dimetrodon occidentalis, and Dimetrodon cf.

D. occidentalis (Berman, 1977; Langston, 1953a, 1953b).

The Pecos Ruins Locality is found in a small exposure in the Abo Formation approximately a mile north of the Pecos Ruins. The deposit consists of a grey shale with an underlying one foot thick marl bed. Recovered taxa include large limb bones of a diadectid and the synapsid

Sphenacodon sp. (Langston, 1953a).

Reported by Vaughn (1969a) and Olson and Vaughn (1970), the Caballo Mountains locality is located on the mountains’ eastern flank. Berman (1993) suggested that the tetrapod taxa recovered from the site indicate an age near the Wolfcampian-Leonardian boundary. Taxa include the lepospondyl Diplocaulus, the temnospondyl Trimerorhachis, and the synapsid

Dimetrodon aff. D. limbatus (Berman, 1993).

The Arroyo de la Parida locality is found on the west slope of Arroyo de la Parida; the locality has produced four tetrapod taxa: the temnospondyl Eryops sp., a diadectid, the synapsids

?Ophiacodon and Sphenacodon (Langston, 1953a). The Salt Brothers Ranch Locality is found five miles east of the Arroyo de la Parida site, and the fossiliferous horizon is near that at Arroyo

119 de la Parida (Langston, 1953a); taxa include the temnospondyl Eryops sp. and the synapsid

Sphenacodon sp. (Langston, 1953a).

The Gallina Well Locality is found in the Abo Formation about 20 km northeast of Socorro. The following taxa are known from the site: the lepospondyl Diplocaulus, the temnospondyls

Trimerorhachis and Zatrachys, and an indeterminate captorhinid reptile (Berman, 1993).

The Los Pinos Mountains Locality is represented by two fossil bearing sites located approximately 30 km east of Interstate Highway 25 near the easten margin of the Los Pinos

Mountains. All specimens were recovered from the lower part of the Abo Formation of Socorro

County. All fossils from the first locality are produced from a limestone layer, which is interpreted as a freshwater pond or lake deposit (Berman, 1993). Taxa include the sarcopterygian Gnathorhiza bothrotreta, the lepospondyl ?Diplocaulus, and the temnospondyls

Trimerorhachis and an indeterminate dissorophid (Berman, 1979b, 1993). The second locality is found stratigraphically near the contact of the Abo Formation and the underlying Bursum

Formation (Berman, 1993). The taxa recovered from this locality include the lepospondyl

Phlegethontia, the temnospondyl Platyhystrix, and the synapsid Ophiacodon (Berman, 1993).

The fossil-bearing sites of the Sierro Lucero Locality are found along a 10 km long, narrow north-south exposure of the lower part of the Abo Formation approximately 8 km east of Sierra

Lucero (Berman, 1993). The vertebrate remains were found in a pond or lake deposit, and they include material assigned to the sarcopterygian Gnathorhiza bothrotreta, the temnospondyl

Trimerorhachis sp., an embolomere “anthracosaur”, the diadectomorph Diadectes sp., and the synapsid Sphenacodon sp. (Berman, 1979b, 1993)

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The only vertebrate fossils reported from the Sangre de Cristo Formation in New Mexico are

found at scattered sites along the upper reaches of the Pecos River drainage; the sites extend

from Glorieta Pass at Glorieta on the eastern border of Sante Fe County southeastward to about 8

km south of Ribera in San Miguel County. The fossils are produced from stream-channel

deposits, and, although a few small portions of articulated skeletons have been recovered, they consist mainly of isolated elements (Berman, 1993). Taxa recovered from the locality are: a xenacanth chondrichthyan; the sarcopterygian Gnathorhiza sp; the temnospondyls Eryops sp.

and Platyhystrix cf. P. rugosus; the lepospondyls Phlegethontia sp., Diplocaulus sp., and

Lysorophus sp., the diadectomorph Diadectes sp.; a captorhinid reptile; and the synapsids

Ophiacodon sp. and Sphenacodon sp. (Berman, 1993).

In Ohio, Locality 6 of Moran (1952) is found in Monroe County within the Washington

Formation of the Dunkard Group. The fossils are produced from two layers of limestone that lie

2 to 3 m below the Waynesburg “A” coal, corresponding to the Mount Morris limestone of West

Virginia and Pennsylvania. Preserved at the site are remains of: the chondrichthyan Dittodus sp.;

the sarcopterygian Sargenodus cf. S. periprion; the temnospondyls Eryops cf. E. megacephalus,

?Branchiosaurus darrahi, and an indeterminate form similar to Trimerorhachis (Romer, 1952);

the lepospondyl Diploceraspis sp.; the reptile Protorothyris morani; and the synapsids

Baldwinonus ? dunkardensis, a possible ophiacodontid, and Edaphosaurus cf. E. boanerges

(Carroll, 1988; Moran, 1952; Reisz, 1986; Romer, 1952).

The fossiliferous unit of Moran’s (1952) Locality H is the Creston Reds, which is found near the

horizon of the Washington “A” coal, at Marietta, Ohio. The exact stratigraphic position of the

Creston Reds within the Washington Group is only approximate, and the only taxon recovered is

the synapsid Edaphosaurus cf. E. boanerges (Moran, 1952; Romer, 1952).

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In Pennsylvania, there are a number of localities from the Washington Formation. Locality 8 is found within a limestone unit of the lower Washington limestone that crops out in Greene

County along the ditch on the west side of Pennsylvania State Route 21 between Ryerson Station andWind Ridge P.O., approximately 1.5 km northeast of the bridge over the North Fork of

Dunkard Fork at Ryeson Station. At this locality, the Washington coal outcrops just 0.6 m below the base of the Lower Washington limestone (Moran, 1952). Here, the temnospondyl Eryops cf.

E. megacephalus has been recovered (Romer, 1952). Locality 11 is found in a limestone quarry located 6 km southeast of West Alexander on the east side of the road leading to West Finley.

The fossils are from the Upper Washington limestone at the top of the Washington Formation

(Moran, 1952); the lepospondyl Megamolgophis agostinii is known (Romer, 1952). Locality 24 is found about 1 km north of Garrison, Pennsylvania on the west side of Pennsylvania Route 18, and the fossils are produced from a fresh-water limestone deposit that, based on its apparent position relative to the Nineveh coal, is tentatively assigned to the Lower Rockport limestone

(Moran, 1952). The lepospondyl Diploceraspis burkei has been recovered from this site (Romer,

1952). Finally, Locality 15 is represented by a quarry on the east side of Pennsylvania Route

231 approximately 3 km south-southeast of the town limits of Claysville. An indeterminate temnospondyl is produced from one of the thin limestone units that are exposed in the quarry, but the exact stratum from which the fossils are derived is unknown (Moran, 1952; Romer,

1952).

Following the stratigraphic nomenclature of Lucas (2006), the Wolfcampian of Texas includes, in ascending order, the Markley, Archer City, and lower Petrolia formations, which together form the lower two thirds of the Wichita Group. Although the basal sections of the Petrolia formation are Wolcampian in age, the majority of the unit is lowermost Leonardian in age, so it is treated within the Leonardian section below.

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Beginning with collecting efforts dating to the late nineteenth century (Craddock and Hook,

1989), the Lower Permian units of Texas have produced a wealth of tetrapod remains from over

200 localities. Hook (1989) provided an extensive, formation-based review of Texas’s Early

Permian fauna from the Wichita Group, incorporating data from previously published findings and studies of the vast collections at the University of Texas’s Texas Memorial Museum and the

National Museum of Natural History, Washington, D.C.; the data from this study is presented here. Unfortunately, the data is arranged by formation and not presented in terms of individual localities. Hook’s (1989) data, therefore, can speak to the stratigraphic ranges of genera, but is not useful for measuring the relative diversity and commonality of taxa across localities of the same age. It is presented here, but not considered in the below conclusions regarding diadectid diversity during Permo-Carboniferous.

From the Markley formation are: the temnospondyls Edops and Eryops; the “anthracosaurs”

Trematops and Neopteroplax?; the diadectomorph Diadectes; and the synapsids Edaphosaurus and Stereophallodon. The number of genera from the Markley at first appears sparse relative to the overlying units, but Hook (1989) notes that collecting efforts have traditionally favored these latter units, with the Markley receiving little attention. The overlying Archer City formation has

produced the following genera: the temnospondyls Brevidorsum, Edops, Eryops, Neldasaurus,

Parioxys, Tersomius, Trimerorhachis, Zatrachys, an unnamed trematopsid, at least one armored

dissorophid and possibly Platyshystrix; the lepospondyls Pantylus, Pariotichus, Diplocaulus, and

an unnamed urocordylid; the “anthracosaur” Trematops; the seymouriamorph Seymouria; the

diadectomorph Diadectes; the synapsids Ctenospondylus, Dimetrodon, Edaphosaurus,

Lupeosaurus, Ophiacodon, Secodontosaurus, and Stereophallodon; and the reptiles

Protorothyris, Romeria, Protocaptorhinus, Araeoscelis, and Bolosaurus (Hook, 1989).

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Sander (1987) provided a detailed account of the Wolfcampian locality known as the Geraldine

Bonebed, produced from the Archer City Formation. The Geraldine is thought to represent the

deposits of a well-vegetated floodplain populated with small lakes. Vertebrate taxa recovered

from the locality are: the chondrichthyan Orthacanthus texensis; the sarcopterygian Sagenodus

sp.; the “anthracosaur” Archeria crassidisca; the temnospondyls Trimerorhachis insignis,

Zatrachys sp., and Eryops megacephalus; the diadectomorph Diadectes sp.; the reptile

Bolosaurus striatus; and the synapsids Ophiacodon retroversus, Ophiacodon uniformis,

Edaphosaurus boanerges, and Dimtrodon natalis (Sander, 1987).

Sander (1989) documented a series of additional Wolfcampian bonebeds recovered from the

Archer City Formation, all of which represent pond deposits. From Archer City Bonebed 1 are

the temnospondyls Eryops megacephalus, Zatrachys serratus, Acheloma cumminsi, and

Acheloma pricei; the “anthracosaur” Archeria crassidisca; the reptiles Romeria texana and

Bolosaurus striatus; and the synapsids Ophiacodon uniformis and Dimetrodon milleri. Archer

City Bonebed 2 has produced the chondrichthyan Orthacanthus texensis; the sarcopterygian fish

Sagenodus sp.; the temnospondyls Eryops megacephalus, Zatrachys serratus, and Acheloma sp.; the “anthracosaur” Archeria crassidisca; the seymouriamorph Seymouria baylorensis; the diadectomorph Diadectes sideropelicus; and the synapsids Edaphosaurus boanerges and

Dimetrodon milleri. Taxa recovered from Archer City Bonebed 3 are: the chondrichthyan

Orthacanthus texensis; indeterminate actinopterygians; the sarcopterygian fish Ectosteorhachis nitidus; the temnospondyls Eryops megacephalus and a small indeterminate form; the

“anthracosaur” Archeria crassidisca; and the synapsid Edaphosaurus boanerges (Sander, 1989).

From the upper Archer City Formation (latest Wolfcampian), the Coprolite Bonebed has yielded:

the chondrichthyans Hybodus sp. and Orthacanthus texensis; indeterminate actinopterygians; the

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sarcopterygian fishes Sagenodus periprion and Ectosteorhachis nitidus; the temnospondyl

Eryops megacephalus; the “anthracosaur” Archeria crassidisca; the diadectomorph Diadectes

sideropelicus; and the synapsids Edaphosaurus boanerges and Dimetrodon limbatus. Also from

the upper Archer City, Rattlesnake Canyon Bonebed 2 has produced: the chondrichthyan

Orthacanthus texensis; indeterminate actinopterygians; the sarcopterygian fishes Sagenodus

porrectus and Spermatodus pustulosus; the temnospondyls Eryops megacephalus, Zatrachys serratus, and Trimerorhachis insignis; the “anthracosaur” Archeria crassidisca; the diadectomorph Diadectes sideropelicus; and the synapsids ?Edaphosaurus boanerges and

Dimetrodon milleri (Sander, 1989).

Romer (1928) provided a comprehensive review of Permian-aged localities from Texas. The

Archer City Formation of Archer County has produced: the temnospondyl Eryops sp. from the

Cottonwood Creek locality; the temnospondyl Eryops sp. and the synapsids Dimetrodon sp. and

Ophiacodon major from the Elm Creek locality; the synapsid Ophiacodon sp. from the Onion

Creek locality; Eryops sp. and the “anthracosaur” Cricotus sp. from the Fireplace locality; the temnospondyls Eryops sp. and Zatrachys sp., Cricotus sp., and Dimetrodon sp. and Ophiacodon retroversus from the Three Forks of the Little Wichita locality; Eryops sp., Cricotus sp., the diadectomorph Diadectes sideropelicus, and Dimetrodon booneorum and Ophiacodon sp. from the Shell Point locality; and Eryops sp., Diadectes sp., and the synapsids Dimetrodon sp. and

Edaphosaurus sp. from the Long Creek locality.

From the latest Wolfcampian of Texas, Romer (1928) documented from Archer County: the

temnospondyls Trimerorhachis sp. and Eryops sp., the lepospondyl Pariotichus brachyops; the

“anthracosaur” Archeria crassidisca, the diadectomorph Diadectes sideropelicus, and the

synapsid Dimetrodon sp. from the North Fork of the Little Wichita; Trimerorhachis sp., Eryops

125 sp., Cricotus sp., and the synapsids Dimetrodon sp., Ophiacodon retroversus, and Edaphosaurus sp. from the Middle Fork of the Little Wichita; and Eryops sp., Dimetrodon sp., and Ophiacodon sp. from the Holliday locality. From the Briar Creek locality, the temnospondyls Trimerorhachis sp., Zatrachys serratus, Eryops sp., and Aspidosaurus sp., the lepospondyl Diplocaulus sp., the

“anthracosaurs” Archeria robinsoni and Cricotus sp., the diadectomorph Diadectes sp., the reptile Bolosaurus sp., and the synapsids Dimetrodon sp., Ophiacodon uniformis, Ophiacodon sp., and Edaphosaurus sp. are known. Also in Archer County is the Godwin Creek locality, which has produced the remains of Trimerorhachis sp., Eryops sp., Cricotus sp., Diadectes sp.,

Dimetrodon sp., Ophiacodon retroversus, and Ophiacodon uniformis. Within Wichita County is the Mount Barry locality; taxa known from this site are: the temnospondyls Trimerorhachis sp.,

Parioxys ferricolus, and Eryops sp., the “anthracosaur” Cricotus sp., the diadectomorph

Diadectes sideropelicus, the reptiles Bolosaurus striatus and Bolosaurus major, the synapsids

Dimetrodon natalis, Dimetrodon booneorum, and Secodontosaurus obtusidens, and two taxa with uncertain affinities, Metarmosaurus fossatus and “Tomicosaurus” sp. (Romer, 1928).

Wolfcampian-aged deposits in Utah include the Cedar Mesa Sandstone and the overlying Organ

Rock Shale. The Cedar Mesa Sandstone directly overlies the Halgaito Shale in the Cutler

Formation; the Permo-Carboniferous boundary occurs at this contact, which is gradational. The unit consists mainly of light-colored, resistant, cliff-forming, and cross-bedded sandstones, and it is thought to represent a shallow water, marginal marine to beach deposit, where the sand was deposited as nearshore bars and coastal dunes. Tetrapod fossils, all referable to the synapsid

Sphenacodon sp., are known from only one locality, which is found near Canyonlands National

Park (Sumida et al., 1999). The Organ Rock Shale is lithologically similar to the older, Virgilan

Halgaito Shale, but its fossils are more numerous and more complete than those of the Halgaito.

The Organ Rock Shale possesses a gradational contact between it and the underlying Cedar Mesa

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Sandstone. Taxa produced from the Organ Rock include the diadectomorphs Tseajaia campi and

Diadectes sp. and the synapsids Ophiacodon sp., Ctenospondylus cf. C. casei, Ctenospondylus cf. C. casei (?), Dimetrodon sp., and Sphenacodon cf. S. ferocior (Baker, 1936; Sumida et al.,

1999; Vaughn, 1964, 1966).

Moran (1952) and Romer (1952) documented a number of localities from the Washington

Formation of West Virginia. Locality 1 is found at Portland, West Virginia; it is located within the lower part of the upper Marietta Sandstone (Moran, 1952) and produced the remains of the synapsid Edaphosaurus cf. E. boanerges (Romer, 1952). Locality 4 is found approximately 2 km southeast of Viola, West Virginia, and the fossil material is produced from a thin limestone bed exposed along an outcrop in the bed of a creek, which is locally known as Line Run and is the first stream to enter Wheeling Creek from the north, east of the town of Viola (Moran, 1952).

Teeth from the chondrichthyan Dittodus sp. have been recovered from Locality 4, as well as remains of the sarcopterygian Sagenodus cf. S. periprion and a questionable temnospondyl

(Romer, 1952). The fossils from Locality 7 were recovered from a fresh-water limestone, but the exact stratigraphic position of the unit is not known, although it is thought that the limstone unit lies between the Waynesburg and Washington coals of the Washington Formation. The site is located 2.5 km southeast of the town of Viola, West Virginia (Moran, 1952), and it contains the remains of the lepospondyl Diploceraspis burkei (Romer, 1952). Locality 9 is found along a roadcut along the east side of the Blacksville-Hundred Road (West Virginia Route 7) just west of the town of Blacksville. The fossiliferous unit, a siliceous limestone lens, is exposed northeast of the confluence of Miracle Run and Dunkard Creek, and it is about 12 m beneath the Hundred sandstone at the horizon of the Upper Marietta Sandstone (Moran, 1952). The reptile

Protorothyris morani is known from the site (Romer, 1952). At Oglebay Park, near Wheeling,

West Virginia, a single fossil specimen was recovered from the basal portion of the Elm Grove

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limestone, from 1.5 to 4.5 m above the top of the Waynesburg coal. This locality, Locality G, is

the stratigraphically lowest vertebrate fossil reported from the Washington Formation. A neural

spine fragment of Edaphosaurus cf. E. boanerges was collected here (Romer, 1952).

Berman (1971) documented an additional locality in West Virginia found on the muddy bank of

Reedy Creek, one half mile south of the town of Reedy. The fossil material, which consists of

one specimen (the internal mold of a skull of Diadectes sp.), was likely transported by Reedy

Creek some distance from its original site of deposition. The sandstone matrix on the specimen

matches that of the upper and lower Marietta sandstones, and, of the two units, only the lower

Marietta Sandstone crops out close to where the specimen was found; thus, it seems reasonable

to assume that the fossil was derived from the lower Marietta Sandstone, which is suggestive of a

terrestrial rather than pond-like habitat, of the Washington Formation (Berman, 1971).

13.4 Leonardian

The fossil-bearing horizon from the Clark Hill locality of Ohio is found approximately 2.5 m below the Nineveh Coal of the Green Formation. Following Lund (1975), the Greene Formation is regarded as Leonardian here. The fossils at Clark Hill are preserved within a light gray, micaceous claystone that weathers to tan. Deposits are interpreted as a freshwater pond or lake deposit, and taxa recovered from Clark Hill include: the sarcopterygian fish Sargenodus cf. S. periprion; the temnospondyl Trimerorhachis; a possible embolomere “anthracosaur”; the diadectomorph Ambedus pusillus; and the synapsid Ctenospondylus ninevehensis (Berman, 1978;

Kissel and Reisz, 2004; Romer, 1952).

Olson (1967) provided an extensive review of the majority of Lower Permian localities in

Oklahoma, which are Leonardian in age and equivalent to the upper Wichita and Clear Fork

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groups of Texas (Olson, 1967; Sullivan and Reisz, 1999). In the review, Olson (1967) presented

the localities based on three geographic regions: southwestern Oklahoma, southcentral

Oklahoma, and central, northcentral, and northern Oklahoma. In the southwestern region,

Warika site 1 has produced: the chondrichthyan Xenacanthus sp.; indeterminate actinopterygians; the “anthracosaur” Archeria sp.; the temnospondyls Trimerorhachis cf. T.

insignis, Eryops cf. E. megacephalus; the lepospondyl Diplocaulus cf. D. magnicornis; the diadectomorph Diadectes sp.; and the synapsids Ophiacodon retroversus, Dimetrodon limbatus; and Edaphosaurus boanerges. Waurika site 2 has produced Diadectes sp., and the Waurika site

3 produced fragments of Dimetrodon sp. The East Taylor site has yielded the remains of Eryops sp., Dimetrodon sp., and Edaphosaurus sp. The “anthracosaur” Cricotus sp., the temnospondyls

Trimerorhachis sp. and Eryops sp., the lepospondyl Diplocaulus sp., the diadectomorph

Diadectes sp., and the synapsids Ophiacodon major, Edaphosaurus sp., Dimetrodon dollovianus,

Dimetrodon grandis, and Dimetrodon macrospondylus are known from the Deep Red Run sites.

The West Grandfield site has produced the chondrichthyan Xenacanthus sp., the lepospondyl

Diplocaulus magnicornis, the temnospondyl Trimerorhachis? sp., and Dimetrodon cf. D. giganhomogenes. Poorly preserved remains of Dimetrodon, Eryops, and Trimerorhachis are known from the East Manitou site, as well as Orodus-like chondrichthyan teeth, and a partial skull of the temnospondyl Acheloma cumminsi was produced from the South Snyder site (Olson,

1967; Dilkes and Reisz, 1987).

From southcentral Oklahoma, the Byars site has produced the temnospondyl Zatrachys serratus and the diadectomorph Diadectes sp.; fragments of the synapsid Dimetrodon sp. and the temnospondyl Eryops cf. E. megacephalus were recovered from the South Rosedale site; the

South Paoli site produced a fragment of the synapsid Edaphosaurus; possible remains of Eryops are known from South Pauls Valley site; and Dimetrodon is known from the North Katie site.

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The Dolese Brothers limestone quarry at Richards Spur is also contained within Olson’s (1967)

southcentral region. This locality has produced a diverse assemblage of fossil vertebrates in

Oklahoma, and it has produced more specimens than any other Permian site in Oklahoma (Kissel et al., 2002). The locality and its fauna has been well documented by Olson (1967, 1991), May and Cifelli (1998), Sullivan and Reisz (1999b), and Sullivan et al. (2000). Fossils are preserved in Early Permian fissure fill deposits within the Ordovician-aged Arbuckle Limestone. Taxa reported in the literature include: the temnospondyls Cacops cf. C. aspidophorus, Doleserpeton annectens, Tersomius sp., Pasawioops mayi, ?Eryops sp., Acheloma cf. A. cumminsi, a

trematopid, and a dissorophid; the lepospondyls Phlegethontia cf. P. linearis, Cardiocephalus

peabodyi, Euryodus primus, Llistrofus pricei, Bolterpeton carrolli, and Nannaroter mckinziei;

the seymouriamorph Seymouria sp.; the unnamed Richards Spur diadectid; the reptiles

Captorhinus aguti, Captorhinus magnus, Baeotherates fortsillensis, an indeterminate basal captorhinid, an indeterminate basal captorhinomorph, Colobomycter pholeter, Delorhynchus priscus, Bolosaurus grandis, and an unidentified neodiapsid; and the synapsids Oromycter dolesorum, Mycterosaurus sp., Varanops cf. V. brevirostris, an unnamed mycterosaurine, and an unidentified sphenacodontid (Anderson and Reisz, 2003; Anderson et al., 2009; Bolt, 1969,

1974, 1977; Carroll and Gaskill, 1978; Evans et al., 2009; Fox and Bowman, 1966; Frobisch and

Reisz, 2008; Gregory et al., 1956; Kissel et al., 2002; Maddin et al., 2006; May and Cifelli, 1998;

Modesto, 1996, 1999; Olson, 1991; Reisz, 1980, 2005; Reisz and Sutherland, 2001; Reisz et al.,

1997; Sullivan and Reisz, 1999a, 1999b; Sullivan et al., 2000; Vaughn, 1958).

The central, northcentral, and northern region of Olson (1967) contains a host of tetrapod- bearing localities. From the Wellington Formation, the Perry Site 1 contains a large concentration of the temnospondyl Trimerorhachis insignis and the sarcopterygian Gnathorhiza sp.; remains of the captorhinid reptile Labidosaurus sp. are also known from the site. Perry Site

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3 has produced the temnospondyls Trimerorhachis insignis and Eryops sp., and fragments of

Dimetrodon were identified from Perry Site 4. The McCann Quarry site has produced a diverse assemblage of vertebrates: the chondrichthyan Xenacanthus sp.; indeterminate actinopterygians;

the “anthracosaur” Archeria; the lepospondyl Diplocaulus cf. D. magnicornis; the

temnospondyls Trimerorhachis insignis and Eryops megacephalus; the captorhinid reptile

Labidosaurus; and the synapsids Edaphosaurus cf. E. boanerges and Dimetrodon cf. D.

limbatus.

Overlying the Wellington Formation is the Garber Formation (Olson, 1967), which is also a

fossil-rich unit and equivalent to the Arroyo Formation of Texas (Sullivan and Reisz, 1999). The

Lucien sites consist of five sites near Lucien, Oklahoma, and they have produced the

fragmentary remains of: the chondrichthyan Pleuracanthus and Xenacanthus; the lepospondyls

Diplocaulus magnicornis and Diplocaulus sp.; the temnospondyls Trimerorhachis cf. T. insignis,

Trimerorhachis sp. and Eryops cf. E. megacephalus; and the synapsids Dimetrodon cf. D. giganhomogenes and Dimetrodon sp. Xenachanthus sp. and Diplocaulus magnicornis are known from the Bean Farm site. The well-known Pond Creek site represents a stream deposit that contains an abundant fauna: the chondrichthyan Xenacanthus sp.; the sarcopterygians

Gnathorhiza cf. G. serrata, Sagenodus sp., and Ectosteorhachis sp.; the actinopterygians

Sphaerolepis arctata and Platysomus sp.; the “anthracosaur” Archeria sp.; the lepospondyl

Diplocaulus magnicornis; the temnospondyls Trimerorhachis sp. and Eryop megacephalis; the diadectomorph Diadectes sp.; the captorhinid reptiles Captorhinus cf. C. aguti and Labidosaurus

hamatus; and the synapsids Dimetrodon grandis, Dimetrodon giganhomogenes, and

Edaphosaurus sp. (Olson, 1967).

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The Garber Formation and the overlying Hennessey Formation meet in a transitional zone, not

an abrupt contact. From this zone are a number of localities. The Crescent site has produced the

captorhinid reptile Labidosaurikos meachami and the synapsid Dimetrodon giganhomogenes; L. meachami is also known from the South Crescent site. Well-preserved specimens of D. giganhomogenes are known from the Northwest Edmond site, as are fragments of the lepospondyl Diplocaulus; Dimetrodon sp. and Diplocaulus sp. have been produced from the

North Edmond site. The South Covington site has yielded the remains of Diplocaulus sp.,

Labidosaurikos cf. L. meachami, and Dimetrodon cf. D. giganhomogenes (Olson, 1967).

Sediments from the Hennessey Formation that are exposed near Norman are known for producing the large herbivorous synapsid Cotylorhynchus romeri, as well as the remains of the sarcopterygian Gnathorhiza sp., the lepospondyl Lysorophus cf. L. tricarinatus, and the

captorhinid reptile Captorhinikos chozaensis. C. romeri is also known from the Navina site; no

other taxa are known from this locality (Olson, 1967).

Olson (1970a) described the geology and paleontology of three additional significant Leonardian

sites in Oklahoma: the Orlando, Perry site 6, and a site just south of Norman, Oklahoma in the

Hennessey Formation. The Orlando deposits are found within the early Leonardian Wellington

Formation, approximately 30 m below the contact of the Wellington and the overlying Garber

Formation. Specimens from the site are typically fragmentary and occur in sandy ironstone

nodules. Taxa recovered from the Orlando site are the “anthracosaur” Cricotillus brachydens

and the captorhinid reptile Protocaptorhinus sp. Perry site 6 is also located within the

Wellington Formation, with its beds having been deposited within and along the margins of a

lake. Fossil remains are found disarticulated, but several hundred bones have been collected.

The fauna reported from the site include: the chondrichthyans Xenacanthus sp. and

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“Ctenacanthus”, the sarcopterygian Gnathorhiza serrata; the actinopterygians Platysomus cf. P.

palmaris, Sphaerolepis arctata, and indeterminate forms; the temnospondyls Trimerorhachis cf.

T. insignis and Eryops cf. E. megacephalus; the lepospondyl Diplocaulus cf. D. magnicornis; the

possible araeoscelid reptile Dictybolos tener, and the synapsids Ophiacodon uniformis,

Ophiacodon sp., Dimetrodon cf. D. limbatus, and Dimetrodon sp. Overlying the Garber

Formation, the Hennessey Formation possesses a fossil-bearing site within the city of Norman.

Taxa from this locality are: the sarcopterygian fish Gnathorhiza serrata; indeterminate

actinopterygians; the temnospondyl Tersomius mosesi and a possible second form; the

lepospondyls Rhynchonkos stovalli, Lysorophus tricarinatus, and Peronedon primus; the

captorhinid reptile Captorhinikos parvus and Captorhinikos chozaensis; and possibly the

synapsid Dimetrodon sp. (Olson, 1970a; Carroll, 2009).

In Texas, Leonardian-aged units include the Wichita Group’s Petrolia and Waggoner Ranch

formations, as well as the overlying Arroyo, Vale, and Choza formations of the Clear Fork

Group (Lucas, 2006). As presented in Hook (1989), Petrolia sediments have produced the

remains of: the temnospondyls Eryops, Parioxys, Tersomius, Trimerorhachis, Zatrachys, an

unnamed trematopsid, and at least one armored dissorophid; the lepospondyls Carrolla and

Diplocaulus; the “anthracosaur” Trematops; the seymouriamorph Seymouria, the diadectomorph

Diadectes; the synapsids Ctenospondylus, Dimetrodon, Edaphosaurus, Eothyris, Ophiacodon,

Secondontosaurus, Varanosaurus, and possibly Lupeosaurus; and the reptiles Eocaptorhinus,

Protocaptorhinus, Araeosclis, and Bolosaurus. Genera recorded from the Waggoneer Ranch

formation are: the temnospondyls Eryops, Trimerorhachis, and at least one armored dissorophid; the lepospondyls Pantylus, Lysorophus, cf. Phlegothontia, Crossotelos, Diplocaulus, and gymnarthrids; the “anthracosaur” Trematops; the diadectomorph Diadectes; the synapsids

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Dimetrodon, Edaphosaurus, Glaucosaurus, Mycterosaurus, Ophiacodon, and Varanosaurus; and

the reptiles Eocaptorhinus and Protocaptorhinus (Hook, 1989).

Romer (1928) documented more specifically the localities and taxa of the Petrolia Formation. In

Archer County: the Scalen’s locality has produced the temnospondyls Eryops sp. and

Trimerorhachis sp., the “anthracosaur” Cricotus sp., the diadectomorph Diadectes sp., and the

synapsid Dimetrodon; the Slippery Creek locality produced the temnospondyls Trimerorhachis

sp., Zatrachys sp., and Eryops sp., the diadectomorph Diadectes sp., and the synapsids

Ctenospondylus casei, Dimetrodon sp., Ophiacodon retroversus, Ophiacodon uniformis, and

Varanosaurus wichitaensis; the Tit Mountain locality has produced the temnospondyls Eryops sp., Trimerorhachis sp., and Aspidosaurus sp., the diadectomorph Diadectes sp., and the

synapsids Secodontosaurus obtusidens, Dimetrodon macrospondylus, Eothyris parkeyi, and

Ophiacodon retroversus; and the Camp Creek locality has produced remains of the

temnospondyls Eryops sp. and Trimerorhachis sp., the diadectomorph Diadectes sp., and the

synapsids Dimetrodon sp. and Edaphosaurus sp.

From the Petrolia of Baylor County: Trimerorhachis sp., Eryops sp., Aspidosaurus glascocki,

Diadectes sp., and Dimetrodon sp. are known from the Cox’s Camp locality; Eryops sp. and

Dimetrodon sp. are known from the Head of Godwin Creek; Eryops sp., Diadectes sp.,

Dimetrodon sp., Ophiacodon major, Ophiacodon retroversus, and Varanosaurus sp. from the

Big Wichita locality; and from the South of Fulda locality are known the temnospondyls Eryops

sp., Trimerorhachis sp., and Tersomius texensis, the lepospondyl Cardiocephalus sternbergi, the

diadectomorph Diadectes sp., and the synapsids Dimetrodon sp., Edaphosaurus sp., Ophiacodon

uniformis, and Ophiacodon retroversus. In Wichita County, the Beaver Creek locality of the

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Petrolia Formation has produced: the temnospondyl Eryops sp., the diadectomorph Diadectes sp., and the synapsids Ophiacodon sp. and Edaphosaurus cruciger.

The Waggoner Ranch Formation of Texas has produced several tetrapod-bearing sites in Baylor

County: the temnospondyls Eryops sp. and Trimerorhachis sp., the lepospondyl Diplocaulus sp., the diadectomorph Diadectes sp., and the synapsids Dimetrodon sp. and Ophiacodon sp. from the Bluff Bonebed of Udden; the temnospondyl Broiliellus texensis and the synapsids

Dimetrodon sp. and Glaucosaurus megalops from the Coal Creek locality; the temnospondyls

Eryops sp. and Trimerorhachis sp., the diadectomorph Diadectes sideropelicus, the reptile

Labidosaurus hamatus, and the synapsid Dimetrodon sp. from the Whiskey Creek locality; the temnospondyl Eryops sp., the diadectomorph Diadectes sp., and the synapsids Dimetrodon sp. and Ophiacodon sp. from the Moonshine Creek locality; the temnospondyl Eryops sp., the lepospondyl Pantylus cordatus, the diadectomorph Diadectes sideropelicus, and the synapsids

Dimetrodon limbatus, Dimetrodon sp., and Ophiacodon major from the Military Trail locality; the temnospondyls Eryops sp., Trimerorhachis sp., and Broiliellus sp., the lepospondyl Pantylus sp., the reptiles Araeoscelis casei, Captorhinus sp., Captorhinus laticeps, Captorhinus aguti,

Labidosaurus hamatus, and the synapsids Dimetrodon sp., Ophiacodon sp., Varanosaurus wichitaensis, and Mycterosaurus longiceps from the Mitchell Creek locality. From northeast of

Fulda were recovered the remains of Dimetrodon sp. and Ophiacodon sp. (Berman et al., 1998b;

Romer, 1928).

The Leonardian Arroyo Formation marks the base of the Clear Fork Group in Texas, and the unit

has produced an extensive collection of Lower Permian tetrapods. The Cacops Bonebed of

Baylor County has produced: the temnospondyls Eryops sp., Trimerorhachis insignis, Cacops

aspidephorus, and Isodectes obtusus; the lepospondyl Diplocaulus sp.; the seymouriamorph

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Seymouria baylorensis; the diadectomorph Diadectes sp.; the reptiles Captorhinus sp.,

Captorhinus aguti, Labidosaurus sp., and Labidosaurus hamatus; and the synapsids Dimetrodon

sp., Casea broilii, Ophiacodon sp., Edaphosaurus sp., and Varanops brevirostris. The Craddock

Bonebed of Baylor County has produced: the temnospondyls Eryops sp., Trimerorhachis sp.,

Zatrachys sp., and Acheloma cumminsi, ? Aspidosaurus peltatus, Broiliellus peltatus, and an

indeterminate dissorophid; the lepospondyls Diplocaulus magnicornis, Diplocaulus brevirostris,

Euryodus primus, and Lysorophus sp.; the seymouriamorph Seymouria sp.; the diadectomorph

Diadectes sp.; the reptiles Bolosaurus sp., Araeoscelis gracilis, and Captorhinus aguti; and the

synapsids Trichasaurus texensis, Dimetrodon natalis, Dimetrodon limbatus, Dimetrodon sp.,

Secodontosaurus willistoni, Ophiacodon sp., Edaphosaurus sp., and Varanosaurus acutirostris;

and Goniocephalus willistoni, of uncertain affinities (Romer, 1928).

Also from Baylor County are: the temnospondyls Isodectes sp. and Eryops sp., the lepospondyls

Diplocaulus sp. and Diplocaulus magnicornis, the reptiles Captorhinus sp. and Labidosaurus

hamatus, and the synapsids Dimetrodon sp. and Ophiacodon sp. from the Pony Creek locality;

the temnospondyl Dissorophus sp., the lepospondyl Diplocaulus sp., and the seymouriamorphs

Seymouria sp. and Otocoelus testutineus from the Gray’s Creek locality; the temnospondyls

Trimerorhachis sp., Dissorophus sp., and Eryops sp., the lepospondyls Diplocaulus sp.,

Diplocaulus magnicornis, Lysorophus sp., the reptiles Captorhinus aguti, Labidosaurus sp., and

Labidosaurus hamatus, and the synapsids Dimetrodon sp. and Ophiacodon sp. from the Hog

Creek locality; the temnospondyls Trimerorhachis sp. and Eryops sp., the lepospondyl

Diplocaulus sp., the seymouriamorph Seymouria sp., the diadectomorph Diadectes sp., the

reptile Captorhinus sp., and the synapsid Ophiacodon sp. from the Table Top Mountain locality;

the temnospondyl Trimerorhachis sp., the lepospondyl Diplocaulus sp., the diadectomorph

Diadectes sp., and the synapsid Ophiacodon sp. from the Crooked Creek locality; the

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lepospondyl Lysorophus sp. and the synapsid Ophiacodon sp. from the Dead Man’s Creek

locality; the temnospondyl Eryops sp., lepospondyl Diplocaulus sp., and synapsid Ophiacodon

sp. from the Soap Creek locality (Romer, 1928).

The Coffee Creek locality of the Arroyo Formation has produced: the temnospondyls Eryops sp.,

Trimerorhachis mesops, Zatrachys microphthalmus, Zatrachys conchigerus, Acheloma sp.,

Aspidosaurus chiton, Dissorophus articulatus, and Alegeinosaurus sp.; the lepospondyls

Diplocaulus magnicornis, Diplocaulus brevirostris, Diplocaulus sp., Pantylus coicodus,

Ostodolepis brevispinatus, Pelodosotis elongatum, ? Micraroter erythrogeios, Cardiocephalus sternbergi, Pariotichus brachyops, and Lysorophus sp.; the seymouriamorph Seymouria baylorensis; the diadectomorph Diadectes tenuitectes; the reptiles Captorhinus aguti and

Labidosaurus hamatus; and the synapsids Dimetrodon loomisi, Dimetrodon gigashomogenes,

Dimetrodon dollovianus, Edaphosaurus claviger, Edaphosaurus pogonias, Varanosaurus acutirostris, and Tetraceratops insignis; and Anisodexis sp. of uncertain affinities. Finally, the

Arroyo of Willbarger County has produced the temnospondyl Zatrachys sp., the lepospondyls

Diplocaulus magnicornis and Cardiocephalus sternbergi, the diadectomorph Diadectes sp., and the synapsids Dimetrodon grandis and Dimetrodon sp. at the Beaver Creek locality (Romer,

1928).

Overlying the Arroyo Formation in Texas are the Vale and Choza formations (Lucas, 2006).

The highest stratigraphic occurrence of Diadectes within the Early Permian of Texas is within

the lower Vale. For this reason, localities above this occurrence are not presented here. Olson

(1958) provided a summary of the Vale and Choza fauna of Texas, describing the fauna from

known localities. From the lower Vale, Locality BR is produced within channel, flood plain, and

pond deposits. Taxa from the locality are: the lepospondyl Diplocaulus magnicornis (pond); the

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temnospondyls Eryops megacephalus (flood plain) and Trimerorhachis insignis (channel); the

reptile Labidosaurikos barkeri (flood plain); and the synapsid Dimetrodon gigashomogenes

(flood plain and stream). From Locality BS, taxa include Diplocaulus sp. and Dimetrodon gigashomogenes, which are both recovered from small pond deposits. Locality BT has produced the chondrichthyan Xenacanthus cf. X. playpternus and the temnospondyl Eryops megacephalus from channel deposits, with the lepospondyl Lysorophus tricarinatus and the synapsid

Dimetrodon gigashomogenes recovered from pond and flood plain deposits, respectively.

Locality BU has produced remains of Eryops megacephalus, Diplocaulus recurvatus, and

Dimetrodon gigashomogenes from channel deposits and Labidosaurikos barkeri from the flood plain sediments. From the flood plain gravel of Locality BV, Eryops megacephalus, Diplocaulus sp., Dimetrodon gigashomogenes, and Labidosaurikos sp. are known (Olson, 1958).

Continuing in the lower Vale, Locality BW has produced the chondrychthian Xenacanthus cf. X. platypternus (channel), the lepospondyl Diplocaulus sp. (red shale of unknown origin), the temnospondyl Eryops sp. (flood plain), the diadectomorph Diadectes sp. (channel), and the synapsid Dimetrodon gigashomogenes (flood plain and channel). This single specimen of

Diadectes represents the stratigraphically highest occurrence of the form in Texas; from this site,

Xenacanthus and Dimetrodon are known from multiple individuals, Eryops from three, and

Diplocaulus from one. From Locality BX are known Dimetrodon gigashomogenes and the sarcopterygian Gnathorhiza dikeloda from pond deposits and the reptiles Captorhinus cf. C. aguti and Labidosaurikos barkeri from flood plain sediments. Locality BZ has yielded a diverse fauna, including Xenacanthus cf. X. platypternus, Gnathorhiza dikeloda, Diplocaulus sp., the lepospondyl Lysorophus, the temnospondyl Trimerorhachis sp., Eryops sp., Labidosaurikos

barkeri, and Dimetrodon gigashomogenes from pond deposits, with the latter two forms also

recovered from flood plain deposits. Locality Bab has produced Gnathorhiza dikeloda

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(channel), the temnospondyl Cacops aspidephorus (flood plain), and Labidosaurikos sp. (flood

plain), and Locality Bac has produced the remains of Dimetrodon gigashomogenes from channel deposits (Olson, 1958).

In West Virginia, there are a number of localities from the Greene Formation, which overlies the

Wolfcampian Washington Formation; following Lund (1975), the Greene Formation is regarded as Leonardian here. Moran (1952) and Romer (1952) documented a series of localities from the

Greene Formation of West Virginia. Locality N is located approximately five miles southwest of

Cottageville, West Virginia, but the exact geographic and stratigraphic position of the fossil

yielding unit is not certain (Moran, 1952). The taxon recovered from Locality N is the diadectomorph Limnoscelis sp. (Romer, 1952; Wideman, 2002). The exposure that contains

Locality 14 crops out on the east side of the Cameron-Bellton Road (U.S. Route 250), west of the

town of Bellton. The fossil-bearing unit is a light gray, limy shale that produces the lepospondyl

Diploceraspis burkei, and—although its exact stratigraphic position is unknown—it is

considerably above the Upper Washington limestone and near the horizon of Fish Creek coal

(Moran, 1952; Romer, 1952). Locality 17 is located just east of Adaline; it is found within a

fresh-water limestone unit and produces remains of the temnospondyl “Brachiosaurus” darrahi

(Romer, 1952). Locality 18 is found approximately 1.5 km due east of the southern end of

Captina Island, which is in the Ohio River between Captina, West Virginia and Thompson P.O.,

West Virginia. A fresh-water limestone unit produced the fossil material, which includes the

chondrichthyan Dittodus sp. and the lepospondyl Diploceraspis burkei (Moran, 1952; Romer,

1952). Locality 19, near Bellton, produced an isolated jaw fragment. Since the fossil was not

found in situ, the exact stratigraphic unit from which it came is not known. Since the matrix

adhering to the remains is a light gray shale, it is probable that the fossils were produced from

one of the shale units found between the thin limestones that are exposed at the locality. The

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stratigraphic position of this limestone may be at or near the Nineveh limestone (Moran, 1952).

The temnospondyl ?Eryops sp. was found (Romer, 1952). Locality 20 occurs within a fresh-

water limestone unit that is exposed 1.5 km south of the mouth of Grave Creek, cropping out on both sides of the road (West VirginiaRoute 88) extending from Moundsville to Riggs Knob. The limestone is 7.6 and 102 m above the Nineveh limestone and Washington coal, respectively, and it may represent the horizon of the Lower Rockport limestone (Moran, 1952). Taxa known from

Locality 20 are the chondrichthyan Dittodus sp. and the lepospondyl Diploceraspis burkei

(Romer, 1952). Locality 21 is located near the town of Cameron on the road extending southeast to the top of Big Run Ridge from the eastern branch of Big Run, with the fossil-bearing unit, a fresh-water limestone, exposed on the north side of this road near its junction with U.S. Route

250. Although the exact stratigraphic position of the limestone is uncertain, it is thought that the limestone may represent the horizon of the Lower Rockport limestone, approximately 12 m above the Nineveh coal (Moran, 1952). The temnospondyl ?Eryops sp. and the lepospondyl

Diploceraspis burkei have been recovered (Romer, 1952). The outcrop producing Locality 26 is approximately 0.5 km southeast of Adaline, West Virginia, 160 m south of Locality 17. The fossiliferous unit is interpreted as a fresh-water limestone. It may be the Middle Rockport limestone (Moran, 1952); it produces the acanthodian Acanthodes cf. A. marshi; the sarcopterygian fish Cf. Ectosteorhachis nitidus, the actinopterygian Amblypterus? stewarti, and the lepospondyl Diploceraspis burkei (Romer, 1952). Locality 27 is represented by a fossiliferous fresh-water limestone that is exposed along the surface of a hill that is 1 km west of the confluence of Maggoty Run, where the southernmost tributary enters it from the west. The exposure is located approximately 1.5 km to the northwest of the outcrop of Locality 26, and the limestone unit of Locality 27 may represent the same fossil-bearing, fresh-water limestone unit

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of Locality 26 (Moran, 1952). The lepospondyl Diploceraspis burkei has been recovered from

the site.

Located less than two miles east-northeast of Fairview, West Virginia, Locality 29 represents

two outcrops on both sides of the road between Long Run and Whetstone Creek. A fresh-water

limestone yields the fossil material. Approximately 35 m above the Nineveh coal, the limestone

unit may represent the horizon of the Upper Rockport limestone just above the Taylor sandstone

(Moran, 1952). The chondrichthyan Dittodus sp., the sarcopterygian fish Sagenodus cf. S.

periprion, and the lepospondyl Diploceraspis burkei have been recovered (Romer, 1952). Less

than one mile south of Locality 29, Locality 30 is represented by a series of limestone blocks that

Moran (1952) discovered piled up across the road by a barn. The source of the fossiliferous limestone is therefore uncertain, but it is likely that the limestone pieces are derived from the

same stratigraphic unit that is found at Locality 29 (Moran, 1952). Taxa recovered are the lepospondyls Diploceraspis burkei and Lysorophus minutus (Romer, 1952).

Locality 25 is part of an outcrop located 2.7 km from Crossroads, West Virginia on the east side of the road leading southeast from that town. The fossils were produced from a light brown, limy shale that is interbedded with several thin limestone layers, which are at the same stratigraphic position of the Middle, or possibly Upper or Lower, Rockport limestone (Moran,

1952). Recovered taxa include the chondrichthyan Dittodus sp. and the synapsid Edaphosaurus

cf. E. cruciger (Romer, 1952). The fossil material from Locality 28 is produced from a soft,

light gray shale that is 15 m above the Lower Rockport Limestone, although the shale may be

included in either the Middle or Lower Rockport limestones. The site is located on the south

side of West Virginia Route 7 between Cottontown and Wadestown (Moran, 1952). From

Locality 28 are known the chondrichthyan Dittodus sp.and the temnospondyl Eryops cf. E.

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megacephalus (Romer, 1952). Less than 1.5 km southwest of the town of Liberty, Locality 12 is

found along the north side of the road from Liberty to Paradise. The fossils are produced from a

greenish-gray sandstone unit that has an unknown stratigraphic position, although it may be the

Jollytown sandstone in the lower part of the Greene Group, or it may be the Hundred sandstone,

which is positioned 9 m or more below the Jollytown and included in the upper part of the

Washington Group (Moran, 1952). The taxon Edaphosaurus cf. E. boanerges has been

recovered from Locality 12 (Romer, 1952). Locality J is located 5 km east of New Martinsville

(Moran, 1952), with the remains of a possible temnospondyl reported (Romer, 1952). The

exposure bearing Locality 23 is found on the north side of the West P.O.-Newdale Road,

approximately 320 m southwest of West P.O., West Virginia, and the fossil-bearing unit is a

sandy, fresh-water limestone, which Moran (1952) tentatively identified as the Lower Rockport

limestone. Taxa recovered are an indeterminate temnospondyl and the lepospondyl

Diploceraspis burkei (Romer, 1952). Locality 33 is found on the southwest side of the road on

Brock Ridge, 2 km southwest of West P.O., West Virginia, and 2.3 km southeast of Newdale,

West Virginia. The fossil-bearing unit is a brown and gray clayey shale that is overlain directly

by a fresh-water limestone. It is 16 m below the Windy Gap coal (Moran, 1952) and contains the

remains of the chondrichthyan Dittodus sp., the temnospondyl Eryops cf. E. megacephalus, and an indeterminate synapsid (Romer, 1952).

Locality 34 is an outcrop located approximately 320 m northeast of Newdale, West Virginia along the north side of the Newdale-West P.O. Road. Here, fossils ae produced from a fresh- water limestone, which appears to be approximately 15 m below the Windy Gap coal (Moran,

1952), and contain the fragmentary remains of the lepospondyl Lysorophus dunkardensis

(Romer, 1952). An outcrop located approximately 800 m east of West P.O., along the south side of the West P.O.-Silver Hill Road, produced fossil remains from a brown sandy shale. The

142 outcrop appears to underly the Windy Gap coal horizon by about 12 m (Moran, 1952); it produces the chondrichthyan Dittodus sp., the lepospondyls Diploceraspis burkei, Lysorophus dunkardensis, and Megamolgophis agostinii, and the synapsid Edaphosaurus cf. E. cruciger

(Romer, 1952).

The exposure containing the fossil-bearing sandstone that is Locality 36 is just northeast of

Silver Hill, West Virginia, and it is found along the north side of the road leading from Silver

Hill to Miller Ridge Church. A fresh-water limestone is 1.5 m below the fossiliferous sandstone.

The stratigraphic position of the sandstone is uncertain, but the underlying limestone unit may lie

15 m below the Windy Gap coal (Moran, 1952). Taxa known are the lepospondyls

Diploceraspis burkei and Megamolgophis agostinii (Romer, 1952). Locality 37 is located nearly

1.5 km west of Silver Hill; the fossil material was collected from a brown limy clay that overlies a fresh-water limestone unit. Although the exact stratigraphic position of the clay unit is not know, it is likely either just above the limestone that is 15 m below the Windy Gap coal, or it is just above the Windy Gap limestone (Moran, 1952). The chondrichthyan Dittodus sp., the sarcopterygian fish Sagenodus cf. S. periprion, an indeterminate temnospondyl, the lepospondyls

Diploceraspis burkei and Lysorophus dunkardensis, and an indeterminate edaphosaurid synapsid is known from the site (Romer, 1952). Locality L, at Limestone Hill, West Virginia, is found at the Upper Rockport limestone horizon (Moran, 1952); known taxa are the chondrichthyan

Dittodus sp., an indeterminate actinopterygian, an the temnospondyls Eryops cf. E. megacephalus and ?Trimerorhachis sp. (Romer, 1952).

Locality 16 is part of an exposure that crops out for approximately 800 m on the east side of U.S.

Route 21 from Limestone Hill to Lockhart P.O., south of Limestone Hill, West Virginia. A limestone and a gray shale produce the fossil material, and this limestone is apparently the

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Nineveh limestone. The three limestones found above it at the outcrop are likely the Lower,

Middle, and Upper Rockport limestones (Moran, 1952). Taxa recovered from the site are the chondrichthyan Dittodus sp., the actinopteryigian Amblypterus? stewarti, and the lepospondyl

Diploceraspis burkei (Romer, 1952). Finally, the Lower Rockport limestone has produced one fossil specimen, tentatively identified as a temnospondyl (Romer, 1952), several kilometers southeast of Rockport, West Virginia. The exact location of this site, Locality K, is uncertain

(Moran, 1952).

Although rare, tetrapod remains have been recovered from the late Paleozoic sediments of Prince

Edward Island. From these beds are known: the chondrichthyan Xenacanthus sp.; an

indeterminate sarcopterygian fish; the temnospondyl Eryops megacephalus; the seymouriamorph

Seymouria sp.; the diadectomorph Diadectes sp.; and the synapsids Bathygnathus borealis, cf.

Mycterosaurus, Trichasaurus sp., and an indeterminate ophiacodontid. These taxa overlap with

those from the earliest Leonardian of Texas (Langston, Jr., 1963).

14 Results and Conclusions

Of the 117 Permo-Carboniferous tetrapod-bearing fossil localities documented above and

producing more than a single taxon, taxa thought to possess a diet of high-fiber terrestrial plants

(i.e., Diadectidae, the edaphosaurid synapsid Edaphosaurus, the caseid synapsids, the bolosaurid

reptiles Bolosaurus and Eudibamus, and the captorhinid reptiles of the moradisaurine clade;

Dodick and Modesto, 1995; Reisz, 2006; Sues and Reisz, 1998) are known from 73, with

diadected remains were recovered from 54 of these sites (Fig. 39, Tables 3-6). These results

indicate that herbivorous tetrapods in general and diadectids in particular were identified from 62 and 46 percent, respectively, of the localities examined; these numbers are skewed, however, by

144 the apparent abundance of non-herbivorous tetrapod taxa within Leonardian sites. The uniqueness of the fauna recovered from the Bromacker locality, with its abundance of herbivores

(e.g., diadectids), has been attributed to the site existing within an upland setting, whereas most of the North American sites represent extensive-lowland coastal and alluvial plain settings

(Eberth et al., 2000). However, the Richards Spur site of Oklahoma is also thought to represent an upland locality, but diadectid remains are extremely rare in comparison to other taxa, so the true composition of a Permo-Carboniferous “upland” fauna remains in question. Thus, while the advent of herbivory appears to have led to a diversification within the clade Diadectomorpha, the commonality of herbivorous diadectomorphs (i.e., diadectids) within Permo-Carboniforous localities as a whole is low. Further investigation of abundance of individuals within localities is advisable, but the values discussed herein suggest that diadectids and other high-fiber herbivores were not a significant component of the terrestrial food web during the Late Pennsylvanian and

Early Permian, initially refuting the hypothesis that the modern terrestrial ecosystem may have developed during the Early Permian (e.g., Kissel and Riesz, 2004) and instead supporting the more traditional notion (e.g., Reisz and Sues, 2000) that the oldest example of a modern terrestrial ecosystem is recorded within the Upper Permian Beaufort Group of South Africa.

145

146

Table 3. Missourian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Badger Creek, CO 14 x x x x D. hesperis

Danville, IL 3 x x x x x

Garnett, KS 10 x x x x x

Pitcairn, PA 3 Y x x x D. hollandi

Locality 1, PA 6 x x x x x

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Table 4. Virgilian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Hamilton, KS 8 x x x x x

Topeka, KS 2 Y x x x x

Robinson, KS 6 x x x x x

El Cobre Canyon, NM 16 Y x x x D. zenos

D. aff. D. hollandi

Kinney Brick, NM 4 x x x x x

Ada, OK 6 x x x x D. zenos

Halgaito, UT 11 Y x x x Diadectes sp.

Elm Grove, WY 4 Y x x x x

Kounova, Czech Rep. 7 Y x x x x

Autun, France 4 x x x x x

148

Table 5. Wolfcampian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Placerville, CO 10 x x x x O. sanmiguelensis

Tularosa, NM 7 Y x x x x

Anderson Quarry, NM 5 x x x x Diadectes sp.

Baldwin Bonebed, NM 7 x x x x D. lentus

Camp Quarry, NM 10 Y x x x Diadectes sp.

Welles Quarry, NM 7 x x x x D. lentus

VanderHoof Quarry, NM 7 x x x x D. lentus

Quarry Butte, NM 6 x x x x D. lentus

UCMP V-2844, NM 7 x x x x D. lentus

Jemez Springs, NM 13 x x x x Diadectes sp.

Pecos Ruin, NM 2 x x x x indet. diadectid

Caballo Mountains, NM 3 x x x x x

Arroya de la Parida, NM 4 x x x x indet. diadectid

Gallina Well, NM 4 x x x x x

Los Pinos Mtns, NM 6 x x x x x

149

Table 5 (cont.). Wolfcampian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Sierro Lucero, NM 4 x x x x Diadectes sp.

Sangre de Cristo, NM 9 x x x x Diadectes sp.

Locality 6, OH 8 Y x x x x

Geraldine Bonebed, TX 10 Y x Y x Diadectes sp.

Archer City Bnbd 1, TX 9 x x Y x x

Archer City Bnbd 2, TX 7 Y x x x D. sideropelicus

Archer City Bnbd 3, TX 7 Y x x x x

Coprolite Bnbd, TX 6 x x x x D. sideropelicus

Rattlesnake Cnyn, TX 7 Y x x x D. sideropelicus

Elm Creek, TX 3 x x x x x

Fireplace, TX 2 x x x x x

Three Forks, TX 5 x x x x x

Shell Point, TX 5 x x x x D. sideropelicus

Long Creek, TX 4 Y x x x Diadectes sp.

North Fork, TX 6 x x x x D. sideropelicus

Middle Fork, TX 6 Y x x x x

150

Table 5 (cont.). Wolfcampian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Holliday, TX 3 x x x x x

Briar Creek, TX 13 Y x Y x Diadectes sp.

Godwin Creek, TX 7 x x x x Diadectes sp.

Mount Barry, TX 12 x x Y x D. sideropelicus

Organ Rock, UT 7 x x x x Diadectes sp.

151

Table 6. Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Warika 1, OK 8 Y x x x Diadectes sp.

East Taylor, OK 3 Y x x x x

Deep Run Road, OK 10 Y x x x Diadectes sp.

West Grandfield, OK 3 x x x x x

East Manitou, OK 3 x x x x x

Byars, OK 2 x x x x Diadectes sp.

South Rosedale, OK 2 x x x x x

Richards Spur, OK 24 x Y Y x Indet. diadectid

Perry Site 1, OK 2 x x x x x

Perry Site 3, OK 2 x x x x x

McCann Quarry, OK 7 Y x x x x

Lucien, OK 7 x x x x x

Pond Creek, OK 10 Y x x x Diadectes sp.

Crescent, OK 2 x x x Y x

Northwest Edmond, OK 2 x x x x x

152

Table 6 (cont.). Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

North Edmond, OK 2 x x x x x

South Covington, OK 3 x x x Y x

Norman I, OK 3 x Y x x x

Orlando, OK 2 x x x x x

Perry Site 6, OK 8 x x x x x

Norman II, OK 8 x x x x x

Scalen’s Locality, TX 5 x x x x Diadectes sp.

Slippery Creek, TX 9 x x x x Diadectes sp.

Tit Mountain, TX 8 x x x x Diadectes sp.

Camp Creek, TX 5 Y x x x Diadectes sp.

Cox’s Camp, TX 5 x x x x Diadectes sp.

Head of Godwin Crk, TX 2 x x x x x

Big Wichita, TX 6 x x x x Diadectes sp.

South of Fulda, TX 9 Y x x x Diadectes sp.

Beaver Creek, TX 4 Y x x x Diadectes sp.

153

Table 6 (cont.). Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Bluff Bonebed, TX 6 x x x x Diadectes sp.

Coal Creek, TX 3 x x x x x

Whiskey Creek, TX 5 x x x x D. sideropelicus

Moonshine Creek, TX 4 x x x x Diadectes sp.

Military Trail, TX 6 x x x x D. sideropelicus

Mitchell Creek, TX 13 x x x x x

Fulda, TX 2 x x x x x

Cacops Bonebed, TX 16 Y Y x x Diadectes sp.

Craddock Bonebed, TX 25 Y x Y x Diadectes sp.

Pony Creek, TX 8 x x x x x

Gray’s Creek, TX 4 x x x x x

Hog Creek, TX 11 x x x x x

Table Top Mtn, TX 7 x x x x Diadectes sp.

Crooked Creek, TX 4 x x x x Diadectes sp.

Dead Man’s Creek, TX 2 x x x x x

Soap Creek, TX 3 x x x x x

154

Table 6 (cont.). Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Coffee Creek, TX 29 Y x x x D. tenuitectes

Willbarger, TX 6 x x x x Diadectes sp.

Locality BR, TX 5 x x x Y x

Locality BS, TX 2 x x x x x

Locality BT, TX 3 x x x x x

Locality BU, TX 4 x x x Y x

Locality BV, TX 4 x x x x x

Locality BW, TX 4 x x x x Diadectes sp.

Locality BX, TX 3 x x x Y x

Locality BZ, TX 6 x x x Y x

Locality Bab, TX 2 x x x Y x

Locality 21, WV 2 x x x x x

Locality 30, WV 2 x x x x x

Locality 23, WV 2 x x x x x

155

Table 6 (cont.). Leonardian locality data, listing those tetrapod-bearing sites that produce taxa thought to possess an herbivorous diet.

Locality Tetrapod Taxa Edaphosaurus Caseid Bolosaurus Moradisaurine Diadectid

______

Locality 33, WV 2 x x x x x

West P.O., WV 4 Y x x x x

Locality 36, WV 2 x x x x x

Locality 37, WV 4 Y x x x x

Locality L, WV 2 x x x x x

PEI, Canada 7 x x x x Diadectes sp.

156

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Appendix 1

List of characters used to test the monophyly of Diadectidae. No characters were ordered. Characters incorporated from other studies are referenced, with the original number of the character from a particular study indicated.

1) Frontal: excluded from orbit (0); contacts orbit between prefrontal and postfrontal (1). (Laurin and Reisz, 1997, 8).

2) Lateral parietal lappet: absent (0); present (1).

3) Parietal foramen diameter: less than 33% (0) or 33% or greater than the anteroposterior length of the parietal midline suture (1).

4) Postparietal: paired (0); single and median (1). (modified from Laurin and Reisz, 1995, 4; Laurin and Reisz, 1997, 22).

5) Postparietal position: on skull table or on skull table and occiput (0); only on occiput (1). (Laurin and Reisz, 1997, 23; Lee and Spencer, 1997, 11).

6) Tabular: large, on skull table and occiput (0); reduced, on skull table and occiput (1); reduced, nearly to entirely occipital (2).

7) Posterolateral corner of skull table: formed entirely by tabular (0); formed entirely or nearly entirely by supratemporal (1); formed subequally by the supratemporal and tabular (2). (modified from Berman et al., 1992, 2; Berman, 2000, 7).

8) Vertical, shallow temporal notch: absent (0); present (1).

9) Internal nares: short (0); long, where the ratio of the anteroposterior length of the internal nares to the length of the skull table 33% or greater (1).

10) Denticles on palate: present (0); absent (1). (Laurin and Reisz, 1997, 53).

11) Three distinct rows of teeth on palate: absent (0); present (1).

12) Secondary palatal shelf formed by palatine and ectopterygoid: absent (0); present (1).

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13) Palatal ramus of pterygoid makes substantial contribution to posterior medial border of internal naris and prevents a palatine-vomer contact: absent (0); present (1). (Berman et al., 1998a).

14) Medial row of teeth on palatal ramus of pterygoid: absent (0); present (1).

15) Transverse flange of pterygoid: lies at approximately the same level as the palate (0); projects ventrally to or below the level of the maxillary dentition (1).

16) Well-developed teeth on the margin of the transverse flange of the pterygoid: absent (0); present (1).

17) Contact between supratemporal and the dorsal margin of the paroccipital process of opisthotic: absent (0); present (1). (Berman et al., 1998a)

18) Otic trough in ventral flange of opisthotic: absent (0); present (1). (Laurin and Reisz,1995, 58).

19) Position of jaw articulation: at approximately the same level as the occlusal plane (0); ventral to the occlusal plane (1).

20) Deep lower jaw: absent (0); present, where the ratio of the dorsoventral height of the mandible at the level of the coronoid eminence to the anteroposterior length of the jaw is 33% or greater (1). With the exception of Diadectes absitus and Diadectes sanmiguelensis, all species of Diadectes possess a deep lower jaw. Because of this and other features, the diadectid specimens described as D. absitus and Diadectes sanmiguelensis are quite distinct from all other Diadectes species. For the purposes of this genus-based analysis, Diadectes is coded as possessing a deep lower jaw, with the distinct features of D. absitus and D. sanmiguelensis regarded in the second analysis of this study, which treats taxa at the specific, and not simply generic, level.

21) Meckelian fenestra: absent (0); elongate (1); tall, where the ratio of the greatest dorsoventral height to the anteroposterior length is 25% or greater (2).

22) Labial parapet: absent (0); low, where the parapet never projects higher than the bases of the cheek teeth (1); tall, where the parapet is as tall or taller than the occlusal surface of the teeth near the posterior end of the tooth row (2). This character, like 20, is problematic within the

171 genus Diadectes. All species of Diadectes possess a tall labial parapet except those described as Diadectes sanmiguelensis and Diadectes absitus, both of which possess a low labial parapet. For the purposes of this genus-based analysis, Diadectes is coded as possessing a tall labial parapet, with the distinct features of D. absitus and D. sanmiguelensis regarded in the second analysis of this study, which treats taxa at the specific, and not simply generic, level.

23) Anterior process of articular: absent (0); present (1).

24) Coronoid teeth: present (0); absent (1).

25) Infolding of dentine: absent (0); present (1). (Gauthier et al.,1988, 44; Laurin and Reisz, 1995, 68).

26) Deep marginal tooth roots: absent (0); present, with root length less than crown height (1); present, with root length greater than crown height (2).

27) Heterodont dentition, characterized by the presence of transversely expanded cheek teeth: absent (0); present (1).

28) Anterior teeth: conical (0); incisiform (1).

29) Procumbent anterior teeth: absent (0); present in the lower jaw only (1); or present in both upper and lower jaws (2).

30) Degree of molarization of largest preserved, midseries dentary cheek teeth: absent (0); low (1); high, where the degree of molarization is considered high if the ratio of anteroposterior length to mediolateral width and dorsoventral height to mediolateral width are both less than 0.50 (2).

31) Labial and lingual cusps of cheek teeth: absent (0); weakly developed, represented by shoulders (1); or well developed (2).

32) Anterior process of axial intercentrum-atlantal pleurocentrum complex: absent (0); present (1). (Sumida et al., 1992, 9; Laurin and Reisz, 1995, 84; Laurin and Reisz, 1997, 111).

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33) Neural arches of dorsal vertebrae: flat or concave (0); swollen (1). (Laurin and Reisz, 1997, 107; Sumida and Modesto, 2001).

34) Neural spines: short (0); tall, where the ratio of neural spine height to vertebral height is greater than 40% (1).

35) Sacrum composed of one (0), or at least two (1) vertebrae. (Gauthier et al., 1998, 65; Laurin and Reisz, 1997, 119).

36) Lateral shelf on iliac blade: absent (0); present (1). (Heaton, 1980; Laurin and Reisz, 1995, 107).

37) Humerus with a distinct shaft (0), or short and robust, without a distinct shaft (1). (modified from Laurin and Reisz, 1995, 104).

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Appendix 2

Data matrix used to test the monophyly of Diadectidae.

Taxon 1 2 3 4 5 6 7 8 9 10

Lepospondyli 0 0 0 0 0 0 0 0 0 0

Amniota 1 0 0 0 1 2 1 0 0 0

Limnoscelis 0 1 0 1 1 1 2 0 1 0

Tseajaia 0 1 1 1 1 1 1 1 1 0

Ambedus ? ? ? ? ? ? ? ? ? ?

Orobates 0 1 1 1 1 1 2 1 ? 0

Desmatodon ? 1 1 1 1 1 2 1 ? 0

Diasparactus ? ? 1 ? ? ? ? ? ? ?

Diadectes 0 1 1 1 1 1 2 1 0 1

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Data matrix used to test the monophyly of Diadectidae (continued).

Taxon 11 12 13 14 15 16 17 18 19 20

Lepospondyli 0 0 0 0 0 0 0 0 0 0

Amniota 1 0 0 1 1 1 0 0 0 0

Limnoscelis 0 0 0 0 1 1 0 1 0 0

Tseajaia 0 0 0 1 0 0 ? 1 0 0

Ambedus ? ? ? ? ? ? ? ? ? 0

Orobates 0 0 ? 1 0 0 1 1 0 0

Desmatodon 0 1 ? 1 1 0 1 1 0 1

Diasparactus ? 1 ? ? ? ? ? ? 1 1

Diadectes 0 1 1 1 1 0 1 1 1 1

175

Data matrix used to test the monophyly of Diadectidae (continued).

Taxon 21 22 23 24 25 26 27 28 29 30

Lepospondyli 0 0 0 0 0 0 0 0 0 0

Amniota 0 0 0 1 0 0 0 0 0 0

Limnoscelis 1 0 0 0 1 1 0 0 0 0

Tseajaia 2 0 0 0 1 1 0 0 0 0

Ambedus ? 0 ? ? ? 1 1 0 ? 1

Orobates 2 1 0 1 1 2 1 1 1 1

Desmatodon 2 1 1 1 1 2 1 1 1 1

Diasparactus ? 2 ? ? 1 2 1 ? ? 2

Diadectes 2 2 1 1 1 2 1 1 2 2

176

Data matrix used to test the monophyly of Diadectidae (continued).

Taxon 31 32 33 34 35 36 37

Lepospondyli 0 0 0 0 0 0 0

Amniota 0 0 1 0 1 0 0

Limnoscelis 0 1 1 0 1 1 1

Tseajaia 0 1 1 0 1 1 1

Ambedus 1 ? ? ? ? ? ?

Orobates 1 1 1 0 1 1 1

Desmatodon 1 ? 1 1 ? ? 1

Diasparactus 2 1 1 1 1 1 1

Diadectes 2 1 1 0 1 1 1

177

Appendix 3

List of characters used to test the interrelationships of Diadectidae. No characters were ordered. Characters incorporated from other studies are referenced, with the original number of the character from a particular study indicated if appropriate.

1 Dorsal process of premaxilla extends posteriorly to invade nasal along the midline of the skull: present (0); absent (1).

2 Nasals: longer than frontals (0); as long or shorter than frontals (1) (Reisz, 2007)

3 Frontals: narrow anteriorly and wide posteriorly (0); with approximately equal widths anteriorly and posteriorly (1) (Reisz, 2007)

4 Posterior border of postfrontal: in line with suture between frontal and parietal (0); posterior to suture between frontal and parietal (1) (Reisz, 2007)

5 Postorbital: long and in contact with supratemporal (0); short and not in contact with supratemporal (1) (Reisz, 2007)

6 Quadratojugal: occupies less than 50% of the skull’s length behind the posterior margin of the orbit (0); occupies 50-75% of the skull’s length behind the posterior margin of the orbit (1); occupies 75% or more of the skull’s length behind the posterior margin of the orbits (2) (Reisz, 2007)

7 Parietal foramen: located at anteroposterior midpoint along parietal sutural contact (0); located posterior to midpoint along parietal sutural contact (1). Reisz (2007) identifies the posterior location of the parietal foramen as an autapomorphy of Tseajaia, but it should be noted that specimens of “Diadectes” sanmiguelensis (MCZ 2989) and Orobates (MNG8 960 and the holotype MNG 10181) possess the same condition and the taxon is coded as such here; the condition is apparently not present in Orobates specimen MNG 8760, but this “absence” is likely due to imperfect preservation.

178

8 Parietal foramen: small, where the diameter is less than 50% of the anteroposterior length of the parietals along their sutural contact (0); large, where the diameter is 50% or greater of the anteroposterior length of the parietals along their sutural contact (1) (Reisz, 2007)

9 Parietal: does not contact squamosal (0); contacts squamosal (1)

10 Contact between supratemporal and the dorsal margin of the paroccipital process of opisthotic: absent (0); present (1)

11 Posterolateral corner of skull table formed: subequally by the supratemporal and tabular (0); entirely or nearly entirely by supratemporal (1) (modified from Berman et al., 1992; 2)

12 Vertical, shallow temporal notch: absent (0); present (1)

13 Ratio of maximum skull height to skull length: less than 25% (0); 25 to 50% (1); greater than 50% (2)

14 Ratio of snout width (measured at the anteroposterior midpoint of the maxilla) to width of jaw joint: less than 50% (0); between 50 and 75% (1); greater than 75% (2)

15 Internal nares: long, where the ratio of the anteroposterior length of the internal nares to the length of the skull table is 33% or greater (0); short (1)

16 Teeth on vomer: restricted to posterior half of vomer (0); extend anteriorly beyond midpoint (1)

17 Secondary palatal shelf formed by palatine and ectopterygoid: absent (0); present (1).

18 Teeth on the palatine: present (0); absent (1) (Reisz, 2007)

19 Well-developed/wide interpterygoid vacuity: present (0); absent (1)

20 Single row of teeth along the medial edge of the palatal process of pterygoid: absent (0); present (1) (Reisz, 2007)

21 Medial row of teeth on palatal ramus of pterygoid: absent (0); present with teeth numbering less than 15 per pterygoid (1); present with teeth numbering greater than 15 per pterygoid (2)

179

22 Transverse flange of pterygoid with: well-developed teeth (0); small denticles (1); or smooth (2)

23 Transverse flange of pterygoid projects: below the level of the maxillary dentition (0); ventrally to the level of the maxillary dentition (1)

24 Palatal ramus of pterygoid makes substantial contribution to posterior medial border of internal naris and prevents a palatine-vomer contact: absent (0); present (1) (Berman et al., 1998a)

25 Marginal tooth roots: shallow, with root length less than crown height (0); deep, with root length greater than crown height (1)

26 Heterodont dentition, characterized by the presence of transversely expanded cheek teeth: absent (0); present (1)

27 Anterior teeth: concial (0); incisiform (1)

28 Procumbent anterior teeth: absent (0); present in lower jaw only (1); or present in both upper and lower jaws (2)

29 Degree of molarization of largest preserved, midseries dentary cheek teeth: absent (0); low (1); or high, where the ratio of anteroposterior length to mediolateral width and dorsoventral height to mediolateral width are both less than 0.50 (2)

30 Labial and lingual cusps of cheek teeth: absent (0); weakly developed, represented by shoulders (1); or well developed (2)

31 Position of jaw articulation: at approximately the same level as the occlusal plane (0); ventral to the occlusal plane (1)

32 Deep lower jaw: absent (0); present, where the ratio of the dorsoventral height of the mandible at the level of the coronoid eminence to the anteroposterior length of the jaw is 33% or greater (1)

180

33 Meckelian fenestra: elongate (0); or tall, where the ratio of the greatest dorsoventral height to the anteroposterior length is 25% or greater (1) (also noted in Reisz, 2007: 241)

34 Ventral border of medial fenestra of dentary: formed equally by splenial and angular (0); primarily by splenial (1); formed primarily by angular (2)

35 Labial parapet of dentary: absent (0); low, where the parapet never projects higher than the bases of the cheek teeth (1); or tall, where the parapet is as tall or taller than the occlusal surface of the teeth near the posterior end of the tooth row (2)

36 Anterior process of articular: absent (0); present (1)

37 Coronoid teeth: present (0); absent (1)

38 Lateral surface of lower jaw: flat to slightly convex (0); highly convex (1)

39 Ventral shelf on lateral surface of lower jaw: absent (0); present (1)

40 Neural spines: short (0); tall, where the ratio of neural spine height to vertebral height is greater than 40% (1)

41 Humerus: short and robust, without a distinct shaft (0); with short shaft (1) (modified from Laurin and Reisz, 1995; 104)

42 Articular surface of lower jaw (articular): same size as that on quadrate (0); larger anteroposteriorly than that of quadrate (1)

43 Hyposphene-hypantrum articulations: absent (0); present (1)

44 Orientation of long axis of cheek teeth: perpendicular to the long axis of the jaw (0); strongly angled relative to the long axis of the jaw (1).

181

Appedix 4

Data matrix used to test the interrelationships of Diadectidae.

Taxon 1 2 3 4 5 6 7 8 9 10

L. paludis 0 0 0 0 0 0 0 0 0 0

T. campi 0 1 1 1 1 2 1 1 1 0

A. pusillus ? ? ? ? ? ? ? ? ? ?

O. pabsti 0 1 1 0 0 2 1 1 0 0

D. hesperis 0 ? ? ? ? ? ? ? ? 1

D. zenos ? ? ? ? ? ? ? ? ? ?

D. sideropelicus 1 1 1 0 ? 1 0 1 0 1

D. sanmiguelensis 0 1 1 1 0 2 1 0 0 ?

D. absitus 0 1 1 0 0 2 0 1 0 1

D. tenuitectes 0 1 1 1 ? 1 0 1 0 1

182

Data matrix used to test the interrelationships of Diadectidae (continued).

Taxon 11 12 13 14 15 16 17 18 19 20

L. paludis 0 0 0 0 0 0 0 0 0 0

T. campi 1 1 0 0 0 1 0 1 0 1

A. pusillus ? ? ? ? ? ? ? ? ? ?

O. pabsti 0 1 1 1 ? 0 0 0 0 1

D. hesperis 0 1 ? 1 ? ? 1 ? ? 1

D. zenos ? ? ? ? ? ? 1 ? ? ?

D. sideropelicus 0 1 2 2 1 1 1 1 1 1

D. sanmiguelensis 0 1 1 1 ? ? 0 ? ? 1

D. absitus 0 1 1 1 1 1 1 1 0 1

D. tenuitectes 0 1 2 2 1 1 1 1 1 1

183

Data matrix used to test the interrelationships of Diadectidae (continued).

Taxon 21 22 23 24 25 26 27 28 29 30

L. paludis 0 0 0 0 0 0 0 0 0 0

T. campi 2 1 1 0 0 0 0 0 0 0

A. pusillus ? ? ? ? 0 1 0 ? 1 1

O. pabsti 2 1 1 0 1 1 1 1 1 1

D. hesperis 2 1 1 1 1 1 1 1 1 1

D. zenos ? ? ? ? 1 1 ? ? 2 2

D. sideropelicus 1 2 1 1 1 1 1 2 2 2

D. sanmiguelensis ? 1 1 ? 1 1 1 1 1 1

D. absitus 1 2 0 1 ? 1 1 2 1 1

D. tenuitectes 1 2 1 1 1 1 1 2 2 2

184

Data matrix used to test the interrelationships of Diadectidae (continued).

Taxon 31 32 33 34 35 36 37 38 39 40

L. paludis 0 0 0 0 0 0 0 0 0 0

T. campi 0 0 1 0 0 0 0 0 0 0

A. pusillus ? 0 ? ? 0 ? ? 0 0 ?

O. pabsti 0 0 1 2 1 0 1 0 0 0

D. hesperis 0 1 1 0 1 1 1 0 0 1

D. zenos 1 1 ? ? 2 ? ? 0 0 1

D. sideropelicus 1 1 1 2 2 1 1 0 0 0

D. sanmiguelensis 0 0 1 1 1 ? 1 0 0 ?

D. absitus 0 0 1 2 1 ? 1 0 0 0

D. tenuitectes 1 1 1 2 2 1 1 1 1 0

185

Data matrix used to test the interrelationships of Diadectidae (continued).

Taxon 41 42 43 44

L. paludis 0 0 0 0

T. campi 0 0 0 0

A. pusillus ? ? ? 0

O. pabsti 1 1 ? 1

D. hesperis 1 1 1 0

D. zenos 0 ? 1 0

D. sideropelicus 0 1 1 0

D. sanmiguelensis 0 0 ? 1

D. absitus 1 ? 0 0

D. tenuitectes 0 1 1 0