...—“\‘4m‘1‘dlmw‘fi‘fi‘mw" . , . .~ '; L ; . ‘ ..‘“ .’. . ‘ x , m ; .r;h:.-.(u.a. ..‘-z“. :r n r 54:“ .. . .‘.xvl . . ,. w ~.~.t “nun: . , Vang.- “Wren“.n w J .n: , ‘ s u- \» . Mai-e. 1¢ \\ lg“: n '1 "4mm .’x‘ «..' 1.4 . . g a: .r z.- L“! I l r z 1 ".w 4' ,y.- . “..., n, 1 . ,~._ : - .1». at. .m .4...” '3 l ..'.,M, ma, 1 .. Lf v' “‘le . ‘15”. '14:" -- Ir.“ 1 ‘ .x'.’ I“: m. .- 9. .y' ' I ‘1. IL u-u V," l, ‘ .,.,,. r: r' ,. ...: I .'.“... .. ..~ , - Aw" . .‘. }., r: m. 1‘ - . . w- XI THEES IIIIHIHIIWHIM”NIH!!!M!ll!!!HUI!!!INIHIIUIIHIII 0902 4856 This is to certify that the thesis entitled SYSTEMATIC REVISION OF SOME POST—ARROYO CLEAR FORK GROUP (LEONARDIAN: LOWER PERMIAN) CAPTORHINIDS FROM NORTH—CENTRAL TEXAS presented by Daniel Lee Brinkman has been accepted towards fulfillment of the requirements for M. S. Geology degree in //M MajorW p Date 8’ S I 9/ 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution \ f LEBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE ll MSU Is An Affirmative Action/Equal Opportunity Institution c:\circ\detedue.omaao.t SYSTEMATIC REVISION OF SOME POST-ARROYO CLEAR FORK GROUP (LEONARDIAN: LOWER PERMIAN) CAPTORHINIDS FROM NORTH-CENTRAL TEXAS BY Daniel Lee Brinkman A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geological Sciences 1991 é5¢~58¥? ABSTRACT SYSTEMATIC REVISION OF SOME POST-ARROYO CLEAR FORK GROUP (LEONARDIAN: LOWER PERMIAN) CAPTORHINIDS FROM NORTH-CENTRAL TEXAS BY Daniel Lee Brinkman Since 1882 numerous specimens of captorhinids have been recovered from deltaic deposits of the post-Arroyo Clear Fork Group (Leonardian: Lower Permian) of north-central Texas. An analysis of skulls, tooth plates, and some postcranial material suggests that two major lineages of captorhinids, the Labidosaurus and Captorhinus groups, were evolving in this area during deposition of the Vale and Choza Formations. Only the Captorhinus group was abundant. The taxa comprising this group are distinguished by their dentition or by the robustness of their mandibles. The Captorhinus group is a continuous phylogenetic lineage, composed of Captorhinus aquti (Cope 1882), Captorhinoides valensis Olson 1951, the new combination Captorhinoides barkeri (Olson 1954), and possibly Waggoneria knoxensis Olson 1954, which prior to this report was considered to have possibly been a seymouriamorph. A new genus, Olsonia, is proposed to replace the synonymized Captorhinikos Olson 1954. To Drs. E. C. Olson and R. J. Seltin on whose previous work so much of this study has been based. iii ACKNOWLEDGMENTS First and foremost, I would like to thank my committee members: Drs. J. Alan Holman, Richard Seltin, and Ralph Taggart for their editorial comments and support. Dr. Seltin, in particular, willingly offered me encouragement and technical assistance through every phase of my research. I am appreciative of the many discussions I have had with my committee members regarding this project, but I take full responsibility for the systematic matters herein. Many thanks go to the faculty and students of the Department of Geosciences at my undergraduate alma mater, Indiana University-Purdue University at Fort Wayne, for providing me with work space and access to their equipment during the previous two summers. I am especially grateful to Dr. Scott Argast and Mr. Daniel Griggs for their photographic assistance. Drs. John Bolt, Nicholas Hotton III, Farish Jenkins, and Hans-Peter Schultze are gratefully ackowledged for allowing me to examine materials under their care. Special thanks are also extended to Dr. Catherine Forster, Mr. William Simpson, Mr. Charles Schaff, and Mr. Desui Miao for their assistance during my museum visits or in preparing loans of specimens for me. I am especially grateful to Dr. iv Stuart Sumida and his wife Ms. Donna Oye for the generous hospitality they extended to me on my visits to Chicago and to Stuart for graciously allowing me access to specimens in his possession. I thank the many researchers with whom I have discussed my work or with whom I have corresponded. Most notably among them are Drs. Everett Olson, Stuart Sumida, Arthur Busbey III, Gary Johnson, Phillip Murry, James Farlow, the late Mr. Robert Zannon, and, especially, Mr. Jeff Dodick. I would also like to thank my officemate, Mr. Kenneth Ford, for generously allowing me to use his word processor, for patiently listening as I rambled on about my numerous multiple working hypotheses, and, especially, for his technical assistance. Many thanks also go to Ms. Laura Abraczinskas for her willingness to proofread the final version of this thesis. Moreover, Ms. Irene Rinchetti and Ms. Lisa Hallock deserve special recognition for their fine illustrations. Finally, I would like to thank my family and friends for their encouragement and support. I trust you know who you are. It is to you, the people who have always had greater faith in my abilities than I have had in myself, that I owe my deepest gratitude. TABLE OF CONTENTS Page ABBREVIATIONS AND SYMBOLS ............................ Vii Institutional Acronyms ........................... vii Abbreviations Used in the Figures and Tables ..... vii Symbols Used in the Figures and Tables ............ ix LIST OF TABLES ......................................... X LIST OF FIGURES ....................................... Xi INTRODUCTION ........................................... l The Family Captorhinidae ........................... 1 Previous Work ...................................... 3 HISTORICAL ACCOUNT ..................................... 8 Genus Labidosaurus Cope, 1896 ...................... 8 Labidosaurus-like Taxa...... ..................... .. 9 Genus Captorhinus Cope, 1896 ...................... 13 Captorhinus-like Taxa... .......................... 18 METHODS. .............................................. 29 THE ANALYSIS .......................................... 34 SYSTEMATIC PALEONTOLOGY ............................... 53 Genus Captorhinus Cope, 1896. ..................... 53 Genus Captorhinoides Olson, 1951 .................. 61 Genus Waqqoneria Olson, 1951 ...................... 80 Genus Olsonia, new genus. ......................... 88 DISCUSSION ............................................ 92 SUMMARY .............................................. 101 LIST OF REFERENCES ................................... 105 vi AMNH FMNH MCZ MSU VP OUSM TMM UCLA VP USNM ar atc ati atna ABBREVIATIONS AND SYMBOLS Institutional Acronyms American Museum of Natural History; New York, New York. Field Museum of Natural History; Chicago, Illinois. University of Kansas Museum of Natural History; Lawrence, Kansas. Museum of Comparative Zoology, Harvard University; Cambridge, Massachusettes. Michigan State University Museum; East Lansing, Michigan. Stovall Museum of Science and History, University of Oklahoma; Norman, Oklahoma. Texas Memorial Museum, University of Texas; Austin, Texas. University of California Vertebrate Paleontology Collections; Los Angeles, California. United States National Museum of Natural History, Smithsonian Institution; Washington, D. C. Abbreviations Used in the Figures and Tables angular articular atlantal centrum atlantal intercentrum atlantal neural arch vii axc axial centrum axna axial neural arch cp cultriform process d dentary DTO degree of tooth overlap (i.e. the number of teeth of the lingual row overlapping teeth of the labial row) f frontal ID # specimen identification number j jugal l lacrimal LAB labial tooth row LING lingual tooth row LTP maximum length of multiple tooth row area of tooth plate LT labyrinthodont tooth m maxilla MID middle tooth row n nasal op opisthotic p parietal paf parietal foramen pf postfrontal pm premaxilla po postorbital pra proatlas prf prefrontal ps parasphenoid pt pterygoid viii qj sof SP sq st stf WTP BU K5 +3 quadrate quadratojugal suborbital fenestra splenial squamosal supratemporal subtemporal fossa maximum width of tooth plate Symbols Used in the Figures and Tables Baylor County, Texas Foard County, Texas Knox County, Texas Double letters designate Seltin’s collecting localities originally discovered and named by Olson. Letter-number designates collecting localities discovered and named by Seltin. Long dashes represent formational boundaries Dot-dot represents county line boundaries Dot-dash represents major roads Solid line represents major streams Dash-double dots represent intermittent streams stands for "possibly more" "minus two" indicates lingual row was two teeth shy of overlapping with labial row "plus three" indicates three teeth of lingual row overlap with teeth of labial row indeterminate designates a sexually dimorphic taxon ix LIST OF TABLES Table Page 1. List of captorhinid taxa previously reported from the post-Arroyo Clear Fork beds of Texas and from contempo— raneous deposits of Oklahoma ................. 7 2. Data on maxillary tooth plate size, the number of teeth in each row, and the degree of overlap between teeth of the labial and lingual rows in Captorhinoides ...................... 75 Figure 1. LIST OF FIGURES Page General distribution of beds of Leonardian Age in Texas and Oklahoma (Modified from Olson and Mead, 1982) .............................. 2 Distribution of Seltin’s vertebrate fossil localities in the post-Arroyo Clear Fork Group (Modified from Olson, 1958; Seltin, 1972, unpublished ms; Murry and Johnson, 1987) ..................... 4 FMNH UR 113. Plesiotype of Captorhinoideg barkeri. Right maxilla in occlusal View ..... 12 FMNH UR 110. Holotype of Captorhinoides barkeri. Originally the holotype of Labidosaurikos barkeri. Right dentary in occlusal View ............................ 12 MSU VP uncataloged Captorhinus aquti maxilla and dentary from near Fort Sill, OK. A, maxilla in right-lateral View; B, maxilla in occlusal View; C, dentary in occlusal View; D, dentary in right-lateral View ...... 16 FMNH UR 13. Holotype of Captorhinoides valensis. A, skull in left—lateral View; B, skull in ventral View .................... 20 FMNH UR 101. Plesiotype of Captorhinodes barkeri. Originally the holotype of Captorhinikos valensis. A, partial right maxillary tooth plate in occlusal View; B, partial left mandible in occlusal View... 22 FMNH UR 97. Plesiotype of Waqqoneria knoxensis. Originally the holotype of Captorhinikos chozaensis. A, mandibles in ventral View; B, mandibles in occlusal View ........................................ 24 xi 10. 11. 12. 13. 14. 15. 16. FMNH UR 14. Holotype of Waqqoneria knoxensis. A, skull in dorsal View; B, skull in ventral view ................... MSU VP 41. Plesiotype of Captorhinoides valensis. A, skull in dorsal View; B, partial right maxillary tooth plate in occlusal view; C. skull in ventral view.... FMNH UR 183. Plesiotype of Waqqoneria knoxensis. A, skull in dorsal View; B, skull in ventral View ...................... MSU VP 219. Plesiotype of Captorhinoides valensis. A, skull in dorsal View; B, skull in ventral view ................. ..... MSU VP 71. Plesiotype of Captorhinoides valensis. A, skull in dorsal View; B, skull in ventral View ..... . ................ MCZ 1352. Plesiotype of Captorhinoideg valensis. Right maxillary tooth plate in occlusal View... ........................ USNM 21275. Plesiotype of Waqqoneria knoxensis. A, skull in left-lateral View; B, skull in ventral View ............. Three possible phylogenetic relationships for the Captorhinus group.. ................ xii 28 40 49 64 66 67 71 95 INTRODUCTION During alternate summers between 1958 and 1966, Dr. R. J. Seltin led field parties from Michigan State University to deposits of the post-Arroyo Clear Fork Group (Leonardian: Lower Permian) of north-central Texas (Figure 1) to collect fossil vertebrates. During the years between trips, and especially since 1966, Seltin has prepared a large portion of the fossils that were collected. Of particular interest to the present study are eighty-five specimens of captorhinids. The present study is a re-evaluation of the taxonomic status of some post-Arroyo Clear Fork Group captorhinids, based largely on these MSU specimens. The Family Captorhinidae The Family Captorhinidae is a group of early reptiles known from terrestrial deposits of the Early and Middle (Late according to some authors) Permian of North America and the Late Permian of the Soviet Union, India, and Africa (Dilkes and Reisz, 1986). The family is characterized by having the anapsid skull condition, a downturned premaxilla with at least a medial pair of enlarged "incisiform" teeth, an enlarged "caniniform" tooth anteriorly on the maxilla, and in lacking an ectopterygoid bone. \\ \\ O 2'13“ OM ‘ , Okla omc ’3 City Seltin’s Collecting Area ;/? " Ichita oils / // ,é/ Abilene // Son ,1. 7 Angelo TEXAS Figure 1. General distribution of beds of Leonardian Age in Texas and Oklahoma (Modified from Olson and Mead, 1982) . The Family Captorhinidae currently contains thirteen genera that are distinguished primarily on the basis of dental features and skull size. According to Heaton and Reisz (1980) captorhinid skulls are quite large in proportion to the animals’ snout to vent lengths (about 30%) and solidly built. As such, captorhinid skulls tend to be relatively more common, better preserved, and of greater diagnostic value than other skeletal elements (Heaton and Reisz, 1980). With few exceptions, the early captorhinids were relatively small animals with a single-row dentition; whereas later forms were much larger and had multiple rows of posterior maxillary and dentary teeth. Presumably, these modifications (through time) were associated with changes in both diet (Clark and Carroll, 1973; Olson,1983) and demographic strategies (Ricqles, 1980). Previous Work Seltin’s collecting efforts concentrated on outcrops of the Vale Formation in Baylor, Knox, and Foard Counties (Figure 2). The Vale Formation is a clastic wedge of deltaic to paralic sediments that has been differentiated from the underlying Arroyo and the overlying Choza Formations largely on sedimentologic grounds (Olson, 1958; Olson and Mead, 1982). The Vale Formation has been divided into lower, middle, and upper parts based on the dominant types of stream channel deposits found in each (Olson, 1958; l .'v. I 5 - \ ‘ .0 0' . ..‘..“ ‘\ \ { °.\ >. E \a‘..J / '—{ 0. E E ..’Oo\’-o. o :“1. W /\ .-~’>”“'§\.§ r ”...; // . .. F2 _ "+0; “.“M y I \. 3 : ....... ‘9! [$565955 599.531 ...................... " CHOZA i K \ (. mm mm / ...... c; . i / .\ .. o - “V0: “0 coiivr ~ \ \\ VALE ~\ C004, . 3’ Oh” F1 '\ 'o ’r ! D “70104 NWF:\ BT BS '82 ‘3‘. \3 A. ”'al ( 00L.f/"€' . \ BU !\ 0. ‘ \ o) I ..’. .I\ I .0 ; \.\. a}..{ ‘0. \: .’." / L /' i : av\.‘ } 'NJ - l’ i ----------- {- IG ORANT RIDGE 3i?“ 3‘“ °\ 3/ {PGMHAND ‘ Béafl'y ..- :l 23/ ." N A. Q i 1 / KO" K1 “’10,er "3". ..' ' —o—o / IAYlOR COUNTY if I / / KNOX COUNTY .gt \ \ \ ‘ .fi ! § .’ g I I I 1 ‘0 5.- “\ \ . O- E I, ’ ' .‘.~.‘ g ~. :50 ARROYO : .‘.... "N : “~o. Gs .§‘~.‘ ~o-e-u—.—.-. Scale in Miles Figure 2. Distribution of Seltin’s vertebrate fossil localities in the post-Arroyo Clear Fork Group (Modified from Olson, 1958; Seltin, 1972, unpublished ms; Murry and Johnson, 1987). Olson and Mead, 1982). Together, the Arroyo, Vale, and Choza Formations comprise the Clear Fork Group. Seltin acquired his collecting area from his graduate advisor, E. C. Olson, when Olson began to study temporally equivalent deposits in Oklahoma, as well as the Upper Permian. Olson reported on the geology and vertebrate paleontology of his post-Arroyo Clear Fork localities in the 1950’s (see Olson, 1958, for his summary). Of particular importance to the present study were Olson's 1951 and 1954 reports on the captorhinids of the Vale and Choza Formations. Seltin (1959a, 1964, 1972, unpublished ms, 1985) and Murry and Johnson (1987) reported additional faunal and geological information for the northern Vale localities where they had worked; while Olson and Mead (1982) reported similar information for more southern Vale outcrops. All of these reports included information on captorhinids. In addition, Stovall (1950) and Olson (1970) reported two additional captorhinid species from contemporaneous deposits in Oklahoma. Although Olson did substantial work on these post— Arroyo Clear Fork beds during the late 1940’s and early to mid 1950’s, he was not the first paleontologist to explore this area for fossils. As early as 1882, C. H. Sternberg prospected for fossils in the Vale Formation of Baylor County (Craddock and Hook, 1989). Except for a partial captorhinid maxillary tooth plate, MCZ 1352, Sternberg came away from the Vale Formation empty-handed (Olson, 1990). As many as seven genera and eleven species of captorhinids have previously been reported from the post— Arroyo Clear Fork beds of Texas and from temporally equivalent deposits in Oklahoma (Table 1). These genera and species have been distinguished from each other primarily on the number and configuration of tooth rows found posteriorly on their maxillae and dentaries, on the nature of the transitions from the multiple tooth rows posteriorly to the single tooth row anteriorly, or on the relative robustness of their lower jaws. Much of the material on which the above taxa have been based is limited and of an extremely fragmentary nature (Olson, 1951, 1954, 1962a, 1967; Olson and Mead, 1982). Thus, Olson and Mead (1982) suggested that a re-examination of the Vale captorhinids based on additional materials would likely change the current status of these genera and species. The Michigan State University collections represent a significant addition to the number of known specimens for this taxonomic complex and provided the rationale for the research described in this study. Table 1. 7 List of captorhinid taxa previously reported from the post-Arroyo Clear Fork beds of Texas and from contemporaneous deposits of Oklahoma. TAXON Captorhinus aquti Captorhinoides valensis Captorhinikos valensis Captorhinikos chozaensis Captorhinikos parvus cf. Labidosaurus sp. Labidosaurikos meachami Labidosaurikos barkeri cf. Labidosaurikos sp. cf. Rothianiscus sp. Large captorhinomorph FORMATION Vale, Choza? Vale Vale Choza, Hennessey Hennessey Vale, Choza Garber-Hennessey Transition Zone Vale, Choza Vale Vale Vale PUBLISHED SOURCE Olson (1958), Seltin (1959b) Olson (1951, 1954) Olson (1954, 1958) Olson (1954, 1958, 1962a, 1967) Olson (1970) Murry and Johnson (1987) Stovall (1950), Olson (1967) Olson (1954) Olson and Mead (1982) Olson and Mead (1982) Murry and Johnson (1987) HISTORICAL ACCOUNT In this section I present brief taxonomic histories of the Clear Fork and equivalent age captorhinids and mention the major morphological characteristics that have been used to differentiate them. Genus Labidosaurus Cope 1896 Except for Labidosaurus hamatus (Cope 1895), a relatively large, single tooth-rowed form from the Arroyo of Texas, all of the later Leonardian age captorhinids have multiple rows of teeth posteriorly in their jaws. Cope (1896) established the genus Labidosaurus for some single tooth-rowed specimens from the Arroyo that were originally assigned to his multiple tooth-rowed genus Pariotichus. Case (1911) synonymized Pariotichus and several other poorly preserved, presumably multiple tooth-rowed Cope taxa, with Captorhinus aquti (Cope 1882) (See reviews in Fox and Bowman, 1966; Heaton, 1979). One of the taxa that Case (1911) synonymized with Captorhinus aquti was at different times placed in all three of the above genera, demonstrating the similar cranial morphology of these Clear Fork taxa! Case (1911) recognized two species of Labidosaurus and four species of Captorhinus from the Arroyo, mainly from Cope’s sites in Baylor County, Texas. Williston (1917) 8 suggested that only a single species of Labidosaurus was present in the Arroyo; while Seltin’s (1959b) statistical analysis suggested the presence of only two species of captorhinids (Captorhinus aquti and Labidosaurus hamatus). Both Captorhinus (Olson, 1954, 1958; Seltin, 1959a, 1964, 1972, unpublished ms) and Labidosaurus (Murry and Johnson, 1987) appear to have survived into the post-Arroyo Clear Fork beds of Texas, though in much reduced numbers. Murry and Johnson (1987) were the first to report Labidosaurus in post-Arroyo Clear Fork deposits. Prior to their report, Labidosaurus was not thought to have existed in the post-Arroyo of this region (Olson, 1952, 1958; Olson and Mead, 1982). Whether these isolated vertebrae (P. A. Murry, 1991, personal communication) represent Labidggaurus hamatus or some other species has not been determined. Thus, these specimens are designated here as cf. Labidosaurus sp. Labidosaurus-like Taxa Seltin (1959b) described a new, smaller species of Labidosaurus from somewhat older deposits of Oklahoma. Heaton (1979) synonymized this species with Pariotichus laticeps Williston 1909, a contemporary form from the Wichita Group of Texas, as a new combination, Eocaptorhinus laticeps. Eocaptorhinus laticeps differs from the much larger Labidosaurus hamatus in the structure of both its teeth (Heaton, 1979) and vertebrae (Sumida, 1990). Eocaptorhinus laticeps is thought to have given rise to the 10 first multiple tooth-rowed captorhinid, Captorhinus aquti, early in the Arroyo (Clark and Carroll, 1973; Heaton, 1979; Olson, 1983). Except for the single tooth row in Eocaptorhinus laticeps, the two species are essentially identical in cranial morphology. These taxa are the most thoroughly studied representatives of the Captorhinidae (Sumida, 1990); thus skeletal elements of these forms (in the FMNH collection) were used for comparative purposes in this study. Stovall (1950) established a new genus and species, Labidosaurikos meachami, for an extremely large, Labidosaurus-like skull with clenched jaws from the Garber- Hennessey transition zone of Oklahoma. Olson (1967) considered this zone to be an equivalent of the Vale Formation. Stovall originally considered this specimen, OUSM 3-1-82, to be a large Labidosaurus. But his preparation of the dentition of OUSM 3-1-82 exposed six rows of bulbous, subconical teeth posteriorly on medially expanded, crescentic-shaped maxillae and five rows on similarly shaped dentaries (Stovall, 1950; Dodick, 1989). This specimen is unique in having the anterior teeth of its maxillae (and possibly its premaxillae as well) flanked by smaller, sharp pointed teeth (Stovall, 1950; Olson, 1962a). Olson (1954) established Labidosaurikos barkeri for some considerably smaller specimens from the Vale and Choza Formations. He reported that Labidosaurikos barkeri has five regular rows of bulbous, subconical teeth in its 11 maxillae (Figure 3) and four rows in its dentaries (Figure 4). Seltin (1959a, 1964, 1972, unpublished ms, 1985) reported Labidosaurikos from several Vale localities. Seltin (1959b) synonymized Labidosaurikos barkeri with the much larger (and toothier) Labidosaurikos meachami; considering the former species to be an immature form of the latter. This synonymy was based primarily on FMNH UR 115, a partial maxillary tooth plate from the lower Vale of Baylor County originally assigned to Labidosaurikos barkeri, which has a trace of a sixth row preserved labially. Olson (1967) accepted this change for what he considered to be the "large and robust" Vale specimens of Labidosaurikos, but retained the name Labidosaurikos barkeri for the "more lightly built" Choza specimens. The number of tooth rows in multiple tooth-rowed captorhinids was thought to increase with age (Seltin, 1959b; Edmond, 1960; Fox and Bowman, 1966; Clark and Carroll, 1973). But Bolt and DeMar (1975) found that in Captorhinus aquti the number of tooth rows did not increase with age and that a decrease in the number of rows could occur in extremely old individuals. Recognizing that the same might be true for Labidosaurikos, Olson and Mead (1982), while not fully discounting Seltin (1 chose to follow Olson’s (1954) original assignment of Labidosaurikos barkeri for specimens from both the Vale and Choza Formations. 12 Figure 3. FMNH UR 113. Plesiotype of Captorhinoides barkeri. Right maxilla in occlusal view. Figure 4. FMNH UR 110. Holotype of Captorhinoides barkeri. Originally the holotype of Labidosaurikos barkeri. Right dentary in occlusal view. 13 Olson and Mead (1982) reported some fragmentary, indeterminate materials from the Vale which resembled either Labidosaurikos or Rothianiscus, a large, fairly common captorhinid from the Upper Permian of Texas and Oklahoma (Olson and Barghusen, 1962; Olson, 1965; Olson and Mead, 1982). In addition, Murry and Johnson (1987) reported two specimens of a large, indeterminate captorhinomorph from the Vale Formation. A more definitive placement of this material must await further study. A recent cladistic analysis by J. T. Dodick (1991, personal communication) suggests that Labidosaurus, and not Captorhinus, is the closest sister taxon to Labidosaurikos meachami and Rothianiscus. Dodick put more emphasis on cranial than dental characters, and did not include taxa in which skulls are not definitely known (e.g. Captorhinikos valensis and Labidosaurikos barkeri). Still, Dodick concurred with Seltin (1959b) that Labidosaurikos barkeri is probably a juvenile form of Labidosaurikos meachami. Genus Captorhinus Cope, 1896 The modern concept of Captorhinus aquti was developed by Seltin (1959b), Fox and Bowman (1966), and by Bolt and DeMar (1975). These studies indicate that the dentition of Captorhinus aquti exhibits a wide range of individual variation. Prior to Bolt and DeMar (1975), who found the number and configuration of tooth rows posteriorly on the maxillae and dentaries of Captorhinus aquti to be extremely variable, the posterior maxillary and mandibular dentition 14 of Captorhinus aquti was thought to consist of four or less, "irregular" rows of laterally compressed, chisel-shaped teeth (Figure 5) (Seltin, 1959b; Fox and Bowman, 1966). Most, if not all, of the Vale captorhinids were considered by Olson (1951, 1952, 1954, 1962b) and by Olson and Mead (1982) to have evolved from Captorhinus aquti. Thus, it was imperative that I study the morphological variation in Captorhinus aquti before systematically analyzing the other post-Arroyo Clear Fork captorhinid taxa. A quantitative analysis of the variability in Captorhinus aggti was not attempted, but morphological variations observed by the above authors and myself led to the development of many useful generalizations (which will be presented later as part of a systematic revision of Captorhinus aquti). In addition to many complete or nearly complete Captorhinus aquti skulls and jaws from the Arroyo Formation, most of the above studies incorporated numerous, mostly disarticulated specimens from the fissure-fill deposits of the Dolese Brothers’ Quarry near Fort Sill, Comanche County, Oklahoma. These fissure—fill deposits are thought to be contemporaneous with the Arroyo based primarily on the presence of Captorhinus aquti (Olson, 1954, 1967, 1991). Heaton (1979) estimated that about 5% of the captorhinid jaws collected from the Dolese Brothers’ Quarry have only a single row of teeth posteriorly. Consequently, there has been much debate over whether these are specimens Figure 5. 'TT—________________:3IIII-lluggillllllllllll-I 15 MSU VP uncataloged Captorhinus aquti maxilla and dentary from near Fort Sill, OK. A, maxilla in right-lateral View; B, maxilla in occlusal view; C, dentary in occlusal View; D, dentary in right-lateral View. 16 .. a I‘.‘ --.‘.l. ,:..'-‘”O.‘l.n'-.'i;'n...‘.- - :.': -ocm< F f 4 / / / J m|_.m..c..ol.|e>. 228.85. a. .233.» mcc_-_.o..lc_.:|..o..mc..or ante. commmwss. 6102055036. 0 530.. _ _ _IIJ _ \ / «8:985. _ £3985. \ / amtccmmmmg «rename? z 38.: . w._<> \ , toxin mwdwfiEEofi—mo cued: «330.. (N010 96 sexually dimorphic taxon (i.e. Waqqoneria knoxensis) in the middle Vale. In this hypothesis Captorhinoides valensis would have been contemporaneous with its descendants during part of the middle Vale. Although presently available materials seem to support the first hypothesis more strongly than the latter two, none are falsified. Thus, future discoveries may support the idea that the Vale and Choza members of the Captorhinus group represent a single, sexually dimorphic species instead of two or more sympatric species undergoing much parallelism. As such, the morphological differences between specimens presently assigned to Captorhinoides valensis and both Captorhinoides barkeri and Waqqoneria knoxensis would then represent intraspecific variability through time. Heaton (1979) suggested such temporal variabilty in the dentition of Eocaptorhinus laticeps. Romer and Price (1940) and Seltin (1959b) suggested that dental differences found in specimens of pelycosaurs and Captorhinus aquti, respectively, might have been sexually dimorphic. Heaton (1979) suggested that the differences in adult skull lengths he found in Eocaptorhinus laticeps might be due to sexual dimorphism. Furthermore, Vaughn (1966) suggested that a species of Sevmouria from the Lower Permian of Utah might have been sexually dimorphic in its skull and jaws, as are some modern turtles (Carr, 1952). Although Sumida (1987) suggested that the two types of vertebrae he found in the axial column of Labidosaurus might 97 indicate sexual dimorphism, he thought this hypothesis was untestable given presently available materials. A modified "stratophenetic" approach allows one to suggest morphological characters and stratigraphic fossil ocurrences that might support one or the other of these sexual dimorphic hypotheses. To synonymize both Captorhinoides valensis and Captorhinoides barkeri with Waqqoneria knoxensis, thereby supporting the second hypothesis, one would need to find dorso-ventrally and laterally expanded lower jaws (with multiple rows of bulbous, subconical teeth posteriorly) in the lower Vale. To verify the third hypothesis one would need to show that the differences between the dentition of Captorhinoides valensis (from the lower and middle Vale) and Captorhinoides barkeri (from the upper Vale and Choza) are also found between the holotype of Waqqoneria knoxensis (from the middle Vale) and later Waqqoneria knoxensis specimens. Although future collecting in the lower Vale may uncover specimens that meet this first set of criteria, the poor condition of FMNH UR 14, the holotype of Waqqoneria knoxensis, presently prevents determination of the second set of criteria. Moreover, in post-Arroyo Clear Fork deposits mandibles are much less frequently preserved than are skulls or fragmentary tooth plates. Therefore, finding evidence to support a hypothesis of sexual dimorphism (regardless of immediate ancestry) may be difficult. 98 The strongest evidence against a sexual dimorphic hypothesis might stem from two small vertebrae (Murry, 1991, personal communication) from the lower Arroyo assigned to Waqqoneria? by Murry and Johnson (1987). I have not seen these, but the presence of Waqqoneria in a deposit that old seems unlikely. Until these vertebrae are thoroughly studied and more complete specimens of Captorhinoides and Waqqoneria are found from the lower and middle Vale, it is best to consider them as separate taxa, thereby supporting the first hypothesis. Captorhinus aquti appears to have steadily decreased as deposition of the post-Arroyo sediments progressed, with just a few specimens being reported beyond the middle Vale (Olson, 1954, 1958; Murry and Johnson, 1987). It is probable that the Vale specimens once considered to be Captorhinus aquti (e.g. TMM 30966-433, MSU VP 73, etc.), based on the number and configuration of their MTRA Zahnreihen, are actually specimens of Captorhinoides valensis with somewhat laterally compressed, bulbous, subconical teeth. Of the fifty or so MSU specimens from the lower and middle Vale that have, at least, a portion of their tooth rows exposed in occlusal View, only two or three might possibly be assignable to Captorhinus aquti. Moreover, not one MSU specimen from the upper Vale is assignable to Captorhinus aguti. Thus, less than 6% of the MSU sample from the lower and middle Vale might be Captorhinus aquti. 99 This is close to the percentage of Fort Sill specimens with a single tooth row dentition. Therefore, it seems possible that these few MSU specimens are, like the Fort Sill "Eocaptorhinus", an atavistic morphological variant of a more abundant taxon, i.e. Captorhinoides valensis. The fact that the quantity of possible Captorhinus aquti specimens decreases with time; and that their numbers are inversely proportional to those of the more typical post-Arroyo captorhinids, e.g. Captorhinoides and Waqqoneria may support this contention. Thus, it is likely that Captorhinus aquti did not exist beyond the upper Arroyo. Although differences in the dentition of Captorhinoides valensis and Captorhinoides barkeri might be seen as variability in a single taxon through time, I have chosen to recognize a second "paleomorphospecies", Captorhinoides barkeri, for those younger (late Vale and early Choza) specimens of Captorhinoides. My recognition of both Captorhinoides valensis and Captorhinoides barkeri is similar to the distinction made by Heaton (1979) between Protocaptorhinus pricei and Eocaptorhinus laticeps, which also reflects the paleomorphospecies concept. A third species of Captorhinoides could possibly be established for the upper Vale specimens of this taxon; thereby reflecting Olson’s (1967) arguments about Labidosaurikos and my observations that some Choza specimens of Captorhinoides barkeri (including the holotype, FMNH UR 110) have more mesiodistally compressed tooth crowns than do upper Vale 100 specimens. But until more complete specimens are known from the upper Vale and lower Choza, these slight differences will be considered as intraspecific variability in Captorhinoides barkeri through time (cf. Heaton, 1979). SUMMARY Two major captorhinid lineages, the Labidosaurus group and the Captorhinus group, are recognized from the Vale and Choza Formations of north-central Texas. The systematics of the most common lineage, the Captorhinus group, is the major focus of this study. This lineage is thought to include specimens previously included in Captorhinus aquti (Cope 1882), Captorhinoides valensis Olson 1951, Captorhinikos valensis Olson 1954, Captorhinikos chozaensis Olson 1954, Labidosaurikos barkeri Olson 1954, and Waqqoneria knoxensis Olson 1951. The Captorhinus group consists of Captorhinus aquti, Captorhinoides valensis, the new combination Captorhinoides barkeri (Olson 1954), and Waqqoneria knoxensis. The latter taxon was thought by Olson (1951) to have possibly been a seymouriamorph, but is here considered a captorhinid closely related to Captorhinus and, especially, to Captorhinoides. Furthermore, Olsonia parvus (Olson 1970), new combination, a closely related taxon presumably descended from an isolated population of Captorhinus aquti, was evolving in Oklahoma during the later Leonardian. Captorhinus is a monospecific genus that was most abundant during the Arroyo. Captorhinus aquti is 101 102 characterized by having multiple rows (Zahnreihen) of laterally and medially faceted, chisel-shaped teeth posteriorly on its maxillae and dentaries. The oldest teeth in these Zahnreihen are, with few exceptions, shed along the labial border of the dentigerous area. Furthermore, in Captorhinus the lingual and labial Zahnreihen almost never overlap. The widest portion of the maxillary and mandibular tooth plates of Captorhinus aquti, as seen in occlusal View, are located toward their midlengths. Moreover, the premaxillaries of this taxon usually bears four slightly recurved, subconical teeth. Captorhinus aquti arose in the early Arroyo from an Eocaptorhinus laticeps ancestor and gave rise to Captorhinoides valensis (and possibly Captorhinoides barkeri and Waqqoneria knoxensis) by the early Vale. At least two species of Captorhinoides are recognized from the post-Arroyo Clear Fork deposits of Texas. The dentition of the earlier of these two species, Captorhinoides valensis, is intermediate between that of Captorhinus aquti and the later Captorhinoides barkeri. Like Captorhinus aquti, the tooth plates of Captorhinoides valensis are widest in occlusal View along their midlengths. But unlike Captorhinus aquti, Captorhinoides valensis has multiple rows of bulbous, subconical teeth posteriorly on their maxillae and dentaries; and tend to have only three premaxillary teeth. The crescentic shape of the maxillary tooth plates in Captorhinoides valensis causes the oldest 103 teeth of the lingual and next most labial Zahnreihen to be shed away from the labial border of the dentigerous area. Moreover, unlike Captorhinus aquti, the lingual and labial Zahnreihen on the tooth plates of larger specimens of Captorhinoides valensis overlap. Such overlap may result from an ontogenetic increase in the number of teeth in this species, a condition not found in Captorhinus aquti. Captorhinoides valensis gave rise to Captorhinoides barkeri, and possibly Waqqoneria knoxensis, in the middle Vale; and may have been contemporaneous with its descendants for at least part of the middle Vale. Both Captorhinoides barkeri and Waqqoneria knoxensis are similar to Captorhinoides valensis in having bulbous, subconical teeth in their MTRA Zahnreihen; in exhibiting a great deal of overlap between the lingual and labial Zahnreihen in larger specimens; and in shedding teeth medially from the tooth plate’s labial border. Furthermore, the premaxillaries of Waqqoneria knoxensis are similar to Captorhinoides valensis in usually having just three teeth. Unfortunately, premaxillaries are unknown for Captorhinoides barkeri. Unlike Captorhinoides valensis, Captorhinoides barkeri and, at least the upper Vale, Choza, and Hennessey specimens of Waqqoneria knoxensis, have the widest (occlusal) portions of their tooth plates located posteriorly. Waqqoneria differs from Captorhinoides only in having more dorso- ventrally and laterally expanded mandibles. 104 The most parsimonious phylogentic relationship for the Captorhinus group, given presently available materials, is as follows: Captorhinus aquti gave rise to Captorhinoides valensis during the late Arroyo. By the early Vale, Captorhinoides valensis was the most common captorhinid in north-central Texas. Captorhinoides valensis like its ancestor, Captorhinus aquti, was an extremely morphologically variable taxon. By the middle Vale Captorhinoides valensis gave rise to Captorhinoides barkeri and Waqqoneria knoxensis. As far as is known Captorhinoides barkeri and Waqqoneria knoxensis differ only in Waqqoneria knoxensis having proportionally more robust mandibles. Thus, I have suggested that Captorhinoides and Waqqoneria might represent the two sexes of a sexually dimorphic taxon. But available materials do not fully support this suggestion. Therefore, until new fossil discoveries are made, these forms are considered to be sympatric species; and to have evolved in parallel from the middle Vale into the early Choza. Although they may have lived beyond the early Choza, geologically younger specimens have not been found. Deteriorating environmental conditions during this time may have severely limited faunal distribution and affected preservation (Murry and Johnson, 1987). LIST OF REFERENCES Berman, D. S. and R. R. Reisz. 1986. Captorhinid reptiles from the Early Permian of New Mexico, with description of a new genus and species. Annals of Carnegie Museum, 55:1-28. Bolt, J. R. 1980. New tetrapods with bicuspid teeth from the Fort Sill Locality (Lower Permian, Oklahoma). Neues Jahrbuch fur Geologie und Paléontologie Monatshefte, 82449-459. , and R. DeMar. 1975. An explanatory model of the evolution of multiple rows of teeth in Captorhinus aguti. Journal of Paleontology, 49(5):814-832. , and R. E. DeMar. 1978. Taxonomic position of Captorhinoides valensis Olson (Reptilia: Captorhinomorpha). Journal of Paleontology, 52(4):934- 937. Broom, R. 1910. A comparison of the Permian reptiles of North America with those of South Africa. Bulletin American Museum of Natural History, 28(20):197-234. Busbey, A. 8., III. 1990. The Bally Mountain Lower Permian vertebrate locality, Kiowa Co., Oklahoma (Abs.). Journal of Vertebrate Paleontology Abstracts of Papers, 10(3):16A. Carr, A. 1952. Handbook of Turtles; the Turtles of the United States, Canada, and Baja California. Cornell University Press, Ithaca, New York. 542 pp. Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Co., New York. 698 pp. , and W. Lindsay. 1985. Cranial anatomy of the primitive reptile Procolophon. Canadian Journal of Earth Sciences, 22(11):1571-1587. Case, E. C. 1910. New or little known reptiles and amphibians from the Permian (?) of Texas. Bulletin American Museum of Natural History, 28(17):163-181. 105 106 Case, E. C. 1911. A revision of the Cotylosauria of North America. Carnegie Institute of Washington Publication No. 145: 121 pp. Clark, J., and R. L. Carroll. 1973. Romeriid reptiles from the Lower Permian. Harvard University, Bulletin of the Museum of Comparative Zoology, 144:353-407. Cope, E. D. 1896. Second contribution to the history of the Cotylosauria. American Philosophical Society Proceedings, 35(151):122-149. Craddock, K. W., and R. W. Hook. 1989. An overview of vertebrate collecting in the Permian system of North- central Texas. In R. W. Hook, ed., Permo-Carboniferous vertebrate paleontology, lithostratigraphy, and depositional environments of North-central Texas, pp. 40-46, Field Trip Guidebook No. 2, 49th Annual Meeting of the Society of Vertebrate Paleontology. Dilkes, D. W., and R. R. Reisz. 1986. The axial skeleton of the Early Permian reptile Eocaptorhinus laticeps (Williston). Canadian Journal of Earth Science, 23:1288-1296. Dodick, J. T. 1989. A multiple tooth rowed captorhinid from the Lower Permian of Oklahoma (Abs.). Journal of Vertebrate Paleontology Abstracts of Papers, 9(3):19A. Edmund, A. G. 1960. Tooth replacement phenomena in the lower vertebrates. Royal Ontario Museum (Toronto) Contribution, 52:1-190. Fox, R. C., and M. C. Bowman. 1966. Osteology and relationships of Captorhinus aguti (Cope) (Reptilia: Captorhinomorpha). The University of Kansas Paleontological Contributions, Vertebrata, 11: 79 pp. Gaffney, E. S., and M. C. McKenna. 1979. A Late Permian captorhinid from Rhodesia. American Museum Novitates, 2688:1-15. Gingerich, P. D. 1979. The Stratophenetic Approach to phylogeny reconstruction in vertebrate paleontology. In J. Cracraft and N. Eldredge, eds., Phylogenetic Analysis and Paleontology; Proceedings of a symposium entitled "Phylogenetic Models", convened at the North American Paleontogical Convention II, pp. 41-77, Columbia University Press. Heaton, M. J. 1979. Cranial anatomy of primitive captorhinid reptiles from the Late Pennsylvanian and Early Permian Oklahoma and Texas. Oklahoma Geological Survey Bulletin, 127: 84 pp. 107 Heaton, M. J., and R. R. Reisz. 1980. A skeletal reconstruction of the Early Permian captorhinid reptile Eocaptorhinus laticeps (Williston). Journal of Paleontology, 54(1):136—143. Mayr, E. 1981. Biological classification: toward a synthesis of opposing methodologies. Science, 214:510-516. ' Murry, P. A., and G. D. Johnson. 1987. Clear Fork vertebrates and environments from the Lower Permian of North-central Texas. The Texas Journal of Science, 39(3):253—266. Olson, E. C. 1951. Fauna of Upper Vale and Choza, 1-5. Fieldiana Geology, 10(11):89-218. . 1952. The evolution of a Permian vertebrate chronofauna. Evolution, 6:181-196. 1954. Fauna of the Vale and Choza, 9. Fieldiana Geology, 10(19):211-218. 1956. Fauna of the Vale and Choza, 13. Fieldiana Geology, 10(27):329-334. 1958. Fauna of the Vale and Choza, 14. Fieldiana Geology, 10(32):397-448. . 1962a. The osteology of Captorhinikos chozaensis Olson. Oklahoma Geological Survey Circular, 59(Part II):49-68. . 1962b. Upper Permian terrestrial vertebrates: U.S.A. and U.S.S.R. Transactions of the American Philosophical Society, 52(2): 224 pp. . 1965. Chickasha vertebrates. Oklahoma Geological Survey Circular, 70: 70 pp. 1967. Early Permian vertebrates. Oklahoma Geological Survey Circular, 74: 111 pp. 1970. New and little known genera and species of vertebrates from the Lower Permian of Oklahoma. Fieldiana Geology, 18(3):359-434. . 1979. Seymouria qrandis n.sp. (Batrachosauria: Amphibia) from the Middle Clear Fork (Permian) of Oklahoma and Texas. Journal of Paleontology, 53(3):720— 728. 108 Olson, E. C. 1983. Coevolution or coadaptation? Permo- carboniferous vertebrate chronofauna. In M. H. Nitecki, ed., Coevolution, pp.307-338, University of Chicago Press. 1984. The taxonomic status and morphology of Pleuristion brachycoelus Case; referred to Protocaptorhinus pricei Clark and Carroll (Reptilia: Captorhinomorpha). Journal of Paleontology, 58(5):1282— 1295. 1990. The Other Side of the Medal; a Paleobiologist Reflects on the Art and Serendipity of Science. McDonald and Woodward Publishing Co., Blacksburg, Virginia. 182 pp. 1991. An eryopid (Amphibia: Labyrinthodontia) from the Fort Sill fissures, Lower Permian, Oklahoma. Journal of Vertebrate Paleontology, 11(1):130-132. , and H. Barghusen. 1962. Permian vertebrates Oklahoma and Texas. Oklahoma Geological Survey Circular, 59(Part I):4—48. , and K. Bolles. 1975. Permo—Carboniferous fresh water burrows. Fieldiana Geology, 33(15):271-290. , and J. G. Mead. 1982. The Vale Formation (Lower Permian); its vertebrates and paleoecology. Texas Memorial Museum Bulletin No. 29: 46 pp. Reisz, R. R., and M. J. Heaton. 1982. Bayloria morei Olson 1941 identified as an immature specimen of the Permian reptile Captorhinus aguti (Cope, 1882). Canadian Journal Earth Science, 19:1232-1234. Ricqles, A. de. 1980. Croissance periodique, ontogenese, phylogenese et strategies démographiques: le cas des reptiles Captorhinomorphes. Bulletin Société Zoologique de France, 105(2):363-369. 1984. Remaraques systématiques et méthodologiques pour servir a l’étude de la Famille des Captorhinidés (Reptilia, Cotylosauria, Captorhinomorpha). Annales de Paléontologie, 70(1):1—39. , and P. Taquet. 1982. La faune de vertebrés du Permien supérieur du Niger, I. le captorhinomorphe Moradisaurus grandis (Reptilia, Cotylosauria). Annales de Paléontologie, 68(1):33-106. 109 Ricqles, A. de, and J. R. Bolt. 1983. Jaw growth and tooth replacement in Captorhinus aquti (Reptilia: Captorhinomorpha): a morphological and histological analysis. Journal of Vertebrate Paleontology, 3(1):7- 24. 1956. Osteology of the Reptiles. University of Romer, A. S. Illinois. 772 pp. Chicago Press, Chicago, Romer, A. S., and L. I. Price. 1940. Review of the Pelycosauria. Geological Society of America Special Papers No. 28: 538 pp. Seltin, R. J. 1959a. New vertebrate fossil localities in the Vale Formation (Lower Permian) of North-central Texas. Publications of the Museum, Michigan State University Biological Series, 1(7):259-268. 1959b. A review of the Family Captorhinidae. 10(34):461-509. Fieldiana Geology, . 1964. Grant No. SOB-Johnson Fund (1963), $900, Evolution of the reptiles and amphibians in the Early Permian. Year Book of the American Philosophical Society: 295—297. . 1972. Report of new vertebrate fossil localities in the Vale Formation (Early Permian) of Texas. Unpublished ms. 1985. The skull of Captorhinikos valensis (Olson) (Vale Formation, Early Permian, Texas) (Abs.). Michigan Academy of Science Geology and Mineralogy Section: 2 (mimeograph). A new cotylosaur from North central Stovall, J. w. 1950. 248:46-54. Oklahoma. American Journal of Science, Sumida, S. S. 1987. Two different forms in the axial column of Labidosaurus (Captorhinomorpha: Captorhinidae). Journal of Paleontology, 61(1):155-167. . 1990. Vertebral morphology, alternation of neural spine height, and structure in Permo-Carboniferous tetrapods, and a reappraisal of primitive modes of terrestrial locomotion. University of California Publications Zoology, 122: 129 pp. Vaughn, P. P. 1958. A specimen of the captorhinid reptile Captorhinikos chozaensis Olson, 1954, from the Hennessey Formation, Lower Permian of Oklahoma. of Geology, 66:327-332. Journal 110 Vaughn, P. P. 1966. Sevmouria from the Lower Permian of southeastern Utah, and possible sexual dimorphism in that genus. Journal of Paleontology, 40(3):603-612. Watson, D. M. S. 1954. On Bolosaurus and the origins and classification of reptiles. Harvard University, Bulletin of the Museum of Comparative Zoology, 111:297- 449. White, T. E. 1939. Osteology of Sevmouria bavlorensis Broili. Harvard University, Bulletin of the Museum of Comparative Zoology, 85:325-409. Williston, S. W. 1917. Labidosaurus Cope, a Lower Permian cotylosaur reptile from Texas. Contributions of the Walker Museum, 2:45-57. llllllllllllllllllllHilllllllllllllllll/ll