Photograph bJ, fames Wagoner. LIFE RESTORATION OF CHAMPSOSAURUS HUNTING. Painting by J erome Connolly in The Science Museum of Minnesota. THE LEPIDOSAURIAN REPTILE CHAMPSOSAURUS IN NORTH AMERICA BRUCE R. ERICKSON CURATOR OF PALEONTOLOGY MONOGRAPH VOLUME 1: PALEONTOLOGY Published by THE SCIENCE MUSEUM OF MINNESOTA ST. PAUL: March 31, 1972 MONOGRAPH OF THE SCIENCE MUSEUM OF MINNESOTA VOLUME 1 Library of Congress Catalog Card Number 77-186470 Standard Boole Number 911338-78-0 CONTENTS Page Illustrations ......................................... 2 Introduction ................................................. 5 Species of Champsosaurus . 7 Skull of Cha;rnpsosauru.s gigas, New Species. 12 Postcranial Skeleton of Champsosaurus gigas, New Species ... 26 General Morphology . 52 Skull ................................................... 52 Postcranial Skeleton . 53 Some Aspects of Functional Morphology . 72 Responsive Functions . 75 Correlations and Distribution. 82 Phylogeny . 86 Summary ................................................... 89 Bibliography . 90 ILLUSTRATIONS FIGURES Page 1. Correlation Chart of Champsosaurs. 9 2. Skull of Champsosaurus gigas, dorsal view, PU 16239. 13 3. Skull of Champsosaurus gigas, ventral view, PU 16239. 14 4. Skull of Champsosaurus gigas, dorsal view, PU 16240. 15 5. Skull of Champsosaurus gigas, ventral view, PU 16240. 16 6. Restoration of skull, C hampsosaurus gig as, dorsal view. 19 7. Restoration of skull, Champsosaurus gigas, ventral view. 22 8. Occipital region of skull, Cha.mpsosaurus gigas. 23 9. Lateral view of mandible, Champsosaurus gigas. 25 10. Cervical vertebrae, Champsosa.urus gigas. 27 11. Pleurocentrum of atlas, Champsosaurus gigas. 28 12. Hypocentrum of atlas, Champsosaurus gigas. 28 13. Posterior cervical centrum, Champsosaurus gigas. 29 14. Intercentrum of cervical vertebra, Chmnpsosaurus gigas. 29 15. Dorsal vertebra, Champsosaurus gigas. 30 16. Sacrum, lateral view, Champsosaurus gigas. 32 17. Sacrum, dorsal view, Champsosaurus gigas. 33 18. Large sacral vertebra, Champsosaurus gigas. 33 19. Representative caudal vertebrae, Champsosaut·us gigas. 34 20. Second caudal vertebra, Champsosaurus gigas. 34 21. Typical chevrons, Champsosaurus gigas. 35 22. Cervical rib of Champsosaurus lara.miensis. 36 23. Dorsal rib with uncinate process, Champsosaurus gigas. 36 24. Posterior dorsal rib, Champsosaurus gigas. 37 25. First sacral rib and vertebra, Champsosa.urus gi_qas. 38 26. Second sacral rib, Champsosaurus gigas. 38 27. First caudals, Charnpsosaurus gigas. 38 28. First caudal, Charnpsosaurus gigas. 39 29. Scapula, Charnpsosaurus gigas. 39 30. Coracoid, Champsosaurus gigas. 40 31. Shoulder girdle, anterior view, Champsosaurus gigas. 42 32. Clavicle, dorsal view1 Champsosaurus gigas . ..................... 43 33. Interclavicle, dorsal view, Champsosaurus gigas . ................. 44 2 ILLUSTRATIONS Page 34. Humerus, Champsosaurus gigas . .............................. 45 35. Radius, Champsosauna; gigas . ................................ 46 36. Foreleg, Champsosaurus gigas . ..................... , , ....... , .. 46 37. Ilium, Champsosaurus gigas . ........... , ........... , ........ , . , 47 38. Ventral plates of pelvis, Champsosaurus gigas . , ............ , . , . , . 47 39. Femur, Chanipsosaurus gigas . ................................. 48 40. Tibia-fibula, Champsosaurus gigas . .. , ... , ..... , ... , ............ 49 41. Astragalus, Champsosaurus ,(Jigas . ............. , ............... 49 42. Metatarsal V, Champsosa·urus gigas . ........... , ............. , .. 49 43. Gastralia, Champsosaurus gigas . .............................. , 49 44. Age variation in axis pleurocentra . ............................ 56 45. Juvenile cervical vertebrae....... , ...... , ........... , ......... 56 46. Cervical vertebra, Chanipsosaurus lara1niensis . ................... 57 47. Mounted skeleton of Champsosaurus laramieusis. , ... , , ... , ...... , 59 48. Juvenile sacrum, Chanipsosaurus laraniiensis . ................... 61 49. Coracoid, Champsosaurus natator . ............................. 63 50. Humeri of different species, Champsosaurus . .. , . , ....... , , , ..... 64 51. Ontogenetic development of humerus, Chamvsosaurus . ............ 65 52. Forefoot of Cha1npsosau-rus larwmiensis . ........................ 66 53. Forefoot of Champsosaurus laramiensis (in situ) ................. 66 54, Ontogenetic development of ilium, Charnpsosaurus . , , . , ......... , . 67 55. Pubis of Champsosaurus gigas . , .... , ......................... 68 56. Hind foot of Champsosaw·us laramiensis . ............................... 70 57, Diagrammatic posture of head ...... , ............ , , ...... , ............. , 74 58. Transverse section of rib cage, C ham,psosaurus gigas .............. 76 59, Restoration of lungs in Champsosaurus . ................... , .... 77 60. Cross section of rib shaft, Champsosaurus gigas ............ , , .... 78 61. Juvenile cross section of rib shaft, Chamvsosaurus laramiensis, .... 79 62. Adult cross section of rib shaft, Chamvsosaurus laramiensis . .. , .... 79 63. Map, Cretaceous distribution of Champsosaurus . ................. 84 64. Map, Tertiary distribution of Charnpsosaurus . .................. , . 85 65. Phylogenetic Chart ........................................ , .. 87 TABLES 1. Measurements of Chanipsosanrus gigas . ......................... 50 2. Comparison of adult and juvenile proportions in Champsosaurus . ... 54 3 INTRODUCTION Remains of the moderate-s,ized eosuchian features. Age and individual variations reptile, Champsosaurus, are common in have definite trends as well that have been many late Cretaceous and early Tertiary helpful in the present overall study. Age deposits of western North America and in variations, however, are much easier to the Tertiary of Europe; yet, they are poor­ determine than the latter, which must be ly represented in major museum collections regarded as only suggestive. and, by and large, not identified to specific Most informative of this group is a very level. The prime limiting factor responsi­ large form from the late Paleocene that is ble for the latter situation is the incom­ herein referred to as the new species, pleteness of materials and the extreme mor­ Champsosaurus gigas. In being very abun­ phological uniformity that runs through­ dant and fairly complete, it presents much out the group. interesting morphological evidence-some new and some in a better light; hence, the During the course of several seasons, discussions of general morphology and the writer made extensive collections of functional morphology draw heavily from fossil vertebrates in western North Amer­ it. ica. A sizable quantity of champsosaurian The present study treats Champsosau­ material was included in these collections. rus, the long-snouted North American Confusion in trying to work out the tax­ form. Only brief reference is made to onomy of this material provided the in­ other champsosaurids. In addition to the centive for the initiation of the present rather large sample of Champsosaurus now study, in The Science Museum of Minnesota, ma­ terials from seven other institutions were Handicaps encountered by most workers examined. Certain other materials, namely, have been due chiefly to inadequate sam­ those in the Royal Ontario Museum, were ples resulting in much synonymy. It was not examined but are referred to in the felt, however, that if enough material was present work. analyzed, specific taxonomy could be im­ proved upon. As comparisons were made, In the present work, the term "Clark­ characters that are considered significant forkian" is used rather than Tiffanian in delineating species were found. Many (Wood, 1967) to designate the late Paleo­ are subtle in expression, yet are consistent cene span from Olive to the Eocene boun­ in their occurrence. Due to the lack of dary. Figure 1 is a correlation chart for skulls, most distinctions rest on postcranial North American champsosaurs. 5 INTRODUCTION ACKNOWLEDGMENTS The writer is indebted to numerous per­ staff artists of The Science Museum of sons who have assisted with the present Minnesota, with all of whom I have en­ work. Sincere thanks are extended to joyed working. I am indebted, first of all, Drs. Donald Baird of Princeton University to the late Alexander Oja who was respon­ and Rainer Zangerl of the Field Museum sible for figures 11, 13, 18, 26, 41, and 55; of Natural History for their encourage­ second to Chief Artist, Paul Snyder, who ment and suggestions, as well as providing contributed figures 25, 30, 58, and sug­ the loan of specimens critical to this study. gestions on others; and especially to James Without the loan of other materials as Wagoner who contributed the bulk of the well, this project would have suffered. For illustrations: 6-9, 12, 14, 16, 17, 20, 21, the loan of additional specimens from the 23, 28, 29, 32, 33, 35, 38, 42, 44-46, 48-53, following respective institutions, I wish to 56, and all photographs except figure 47. thank Drs. David Dunkle, formerly of the The frontispiece was painted by Jerome United States National Museum; Robert Connolly. Maps and figures 54, 57, 59, 60, W. Wilson of the South Dakota School of and 65 are the work of the writer who also Mines and Technology; Robert E. Sloan accepts the responsibility for all omissions of the University of Minnesota; and Mr. and inaccuracies in this publication. Fred G. Bard, director of the Saskatche­ Messrs. Ray and Eugene Lingk are to wan Museum of Natural History, Regina. be commended for their diligent