A NEW MULTI-FACETED FRAMEWORK FOR DECIPHERING DIPLODOCID ONTOGENY by David Cary Woodruff A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Earth Sciences MONTANA STATE UNIVERSITY Bozeman, Montana January 2015 ©COPYRIGHT by David Cary Woodruff 2015 All Rights Reserved ii DEDICATION I dedicate this work to the late Mr. John Bell Hatcher. Like myself, Hatcher was raised a farm boy who headed to a distant city to pursue his dreams and a deep scientific passion. In 1884 Hatcher got the opportunity to work one-on-one with one of the most preeminent paleontologists of his day, Othneil Charles Marsh. For nearly a decade Hatcher traveled the American west collecting fossils for Marsh, and becoming a rising star in the Yale based lab. However, Hatcher wanted to be an active and contributing paleontologist, a dream severely demonized in Marsh’s presence. So in 1890 Hatcher left Marsh’s company and set off to blaze his own trail. Yet sadly, Hatcher’s short career lacks the prestigious laurels and deserving recognition in the paleontological annals. Succumbing to Typhoid fever in 1904, Hatcher had a seemingly promising career ahead of him that was dotted with notoriety and achievements during his years at Princeton University and the Carnegie Museum of Natural History. Today Hatcher is most credited with his work on ceratopsian dinosaurs. Hatcher famously discovered the first specimen of the cerastopsian “Torosaurus”, and several of his scientific works revolve around these dinosaurs, most notably “The Ceratopsia”. Yet I would argue that Hatcher’s greatest paleontological accomplishments were in regards to his work on sauropods. Working for the Carnegie Museum of Natural History, Hatcher heavily explored and collected in the Morrison Formation of Colorado. In Colorado, Hatcher discovered and named the enigmatic sauropods Haplocanthosaurus priscus and H. delfsi. However Hatcher’s magnum opus bar none was his description of Diplodocus carnegii in 1901. To this day “Diplodocus (Marsh): Its Osteology, Taxonomy, and Probable Habits, with a Restoration of the Skeleton” remains one of the most distinguished paleontological monographs. Not only is the monograph executed with exquisite precision and detail, but Hatcher’s keen insight and understanding of sauropods is prophetic to this day. Hatcher was one of the first to consider the significance of ontogeny and biomechanics in sauropods. In regards to ontogeny, he noted that the species “Diplodocus lacustrius” was only characterized by its small size and slender build. From this dubious assessment he noted that size was an unsuitable character, and that “D. lacustrius” merely represented an immature Diplodocus. In terms of biomechanic forethought, in 1901 Hatcher wrote, “The Sauropoda have been considered as the least specialized of the Dinosauria, and in many respects this is doubtless true, but in its adaptation for the application of those mechanical principles which combine maximum strength with minimum weight and increased surface for muscular attachment, the vertebral column of Diplodocus exhibits a remarkable degree of specialization, unsurpassed if not unequaled by other vertebrates”. All sauropod biomechanic work done since, in one guise or another, directly descends from this astute observation. John Bell Hatcher’s legacy lives on today as strong as ever, and I gratefully thank him for his contributions and inspiration which has had such a profound impact on my own work. iii ACKNOWLEDGEMENT “Qui si convien lasciare ogni sospetto; ogni viltà convien che qui sia morta.” -Dante Alighieri “The Divine Comedy – Inferno” Canto III, lines 14-15 “Here one must leave behind all hesitation; here every cowardice must meet its death.” Graduate school is no simple or trivial task. And all serious and worthwhile endeavors should present an extreme challenge. I have slipped, stumbled, fallen, limped, and crawled along the way, but I can proudly say that I did not give up. I may not have run the fastest time, but by God I completed the race. There certainly were days I wanted to throw in the towel, but I was able to preserve because of my committee. Drs. Horner, Varricchio, and Woodward all laudably guided me. As Virgil to Dante, the path was harrowing, and along the way there were times for friendly support and others for tough love, but it was critical guidance in any guise. My committee’s care for my success is directly visible from this support and guidance. I am and will always be eternally thankful and grateful for their support. I would not be standing where I am today if were not for these individuals, and I know I will progress and thrive because of them. “Poca favilla gran fiamma seconda.” -Dante Alighieri “The Divine Comedy – Paradiso” Canto I, line 34. “A great flame follows a little spark.” iv TABLE OF CONTENTS Manuscript Information Page ..........................................................................................1 Contribution of Author and Co-Authors ..........................................................................2 1. THE ANATOMY OF THE BIFURCATED NEURAL SPINE AND IT OCCURRENCE WITHIN TETRAPODA ....................................3 Abstract ....................................................................................................................3 Introduction ..............................................................................................................4 Materials and Methods .............................................................................................5 Results ......................................................................................................................7 Dissection .........................................................................................................7 Slide Descriptions ...........................................................................................12 Discussion ..............................................................................................................14 Phylogenetic Distribution of Neural Spine Bifurcation .................................15 Conclusion ..............................................................................................................17 Acknowledgements ................................................................................................18 REFERENCES ...........................................................................................................31 Manuscript Information Page .................................................................................35 Contribution of Author and Co-Authors ................................................................36 2. A NEW MULTI-FACETED FRAMEWORK FOR DECIPHERING DIPLODOCID ONTOGENY ......................................................37 Abstract ....................................................................................................................37 Introduction ..............................................................................................................38 Institutional Abbreviations .......................................................................................41 Materials and Methods .............................................................................................41 Skeletal Features .............................................................................................45 CAT Scans of Pneumatic Architecture ..........................................................45 Vertebral Neural Spines .................................................................................46 Thoracic Ribs .................................................................................................46 Femora ............................................................................................................48 Results .....................................................................................................................49 Morphologic Data ...........................................................................................49 Neural Spine Bifurcation .......................................................................49 Postparietal Foramen .............................................................................50 Macroscopic Examination of Pneumatic Structures ..............................51 Computed Axial Tomography ................................................................53 v TABLE OF CONTENTS - CONTINUED Ontogenetic Data ............................................................................................55 Neural Spine Histology ...........................................................................55 Thoracic Rib Histology ...........................................................................56 Femoral Histology ...................................................................................60 Mother’s Day Quarry Femora ..........................................................60 MOR 592 Femur ..............................................................................60 Discussion ..............................................................................................................61 Morphologic Evidence ...................................................................................61 Pneumatic Architecture, Cranial Foramen, and Femoral Proportions ................................................................................61 Ontogenetic Compilation ...............................................................................65 Conclusion .............................................................................................................67 Acknowledgements ................................................................................................68 REFERENCES ...............................................................................................................93 Supplementary Information ..........................................................................................101 Diplodocus ...........................................................................................................101 Diplodocus cervical vertebra MOR 790 8-10-96-204: Serial and ontogenetic mis-assignment? ......................................................101 Elongation Index: Does a high value indicate maturity? ..............................103 The overall vertebral morphology of MOR 790 8-10-96-204 .................................................................................105 Diplodocus specimen MOR 592 ...................................................................107 Apatosaurus .........................................................................................................111 CM 3390 .......................................................................................................111 CM 555 .........................................................................................................111 Additional Information ........................................................................................112 Anterior Cervical Bifurcation .......................................................................112 Camarasaurus Spine Bifurcation .................................................................114 Haplocanthosaurus .......................................................................................115 Implications Regarding Sauropod Growth Rates .........................................117 Questionably Small Statured Diplodocid Taxa ............................................119 REFERENCES .............................................................................................................135 CUMULATIVE REFERENCES ..................................................................................140 vi LIST OF TABLES Table Page 1.1 Depth and width of Ankole-Watusi neural spine bifurcation...............................................................................................30 2.1 Sauropod specimens examined in this analysis ...............................................82 2.2 Terms, definition, and usage of pneutmatic morphology and histology used in this analysis ..................................................................86 2.3 Diplodocidae Mass Table ................................................................................89 2.4 The Sauropod Ontogeny Scale.........................................................................91 S.I.1 Elongation Index .........................................................................................130 vii LIST OF FIGURES Figure Page 1.1 Cranial comparison of large extinct and extant bovids ....................................20 1.2 Ankole-Watusi cows used for this study .........................................................20 1.3 Musculature comparison of Ankole-Watusi cow versus typical domesticated cattle ...............................................................................21 1.4 Musculature of the four-year-old Ankole-Watusi cow ....................................22 1.5 Preserved portion of nuchal ligament from the four-year-old Ankole-Watusi cow ..................................................................22 1.6 Vertebrae exhibiting neural spine bifurcation within the four-year-old Ankole Watusi cow ...................................................................23 1.7 Vertebrae exhibiting neural spine bifurcation within the sixteen-year-old Ankole-Watusi cow ..............................................................24 1.8 Vertebral features within the Ankole-Watusi ..................................................25 1.9 Histological thin section of nineteen-year-old Ankole-Watusi .................................................................................................26 1.10 Histological thin section of the desiccated nuchal ligament from the four-year-old Ankole-Watusi cow ....................................26 1.11 Lateral comparison of the nuchal ligament ....................................................27 1.12 Time calibrated phylogenetic distribution of neural spine bifurcation within Tetrapoda .................................................................28 1.13 Neural spine bifurcation in extinct and extant tetrapods ...............................29 2.1 Elements histologically sampled for this analysis ...........................................70 2.2 Schematic of coring bit method used in this analysis ......................................70 2.3 Presence of the Post Parietal Foramen within Diplodocidea ...........................71 viii LIST OF FIGURES – CONTINUED 2.4 Macroscopic pneumatic architecture in diplodocid cervical vertebrae .............................................................................................72 2.5 CAT scans of diplodocid anterior cervical vertebrae ......................................72 2.6 CAT scans of diplodocid anterior dorsal vertebrae .........................................73 2.7 CAT scans of diplodocid posterior dorsal vertebrae ........................................74 2.8 Posterior cervical and anterior dorsal vertebrae neural spine histology ..................................................................................................75 2.9 Histologic sections of MOR 790 7-24-96-95 and MOR 790 7-27-8-96 thoracic ribs ..................................................................76 2.10 Histologic section of MOR 592 thoracic rib ..................................................77 2.11 Histologic section of CM 94 (Diplodocus carnegii paratype) thoracic rib .....................................................................................................78 2.12 Histologic section of the diplodocid femur MOR 790 7-23-95-122 ...................................................................................79 2.13 Histologic section of the Diplodocus femur MOR 592-35 ............................79 2.14 Selection of the diplodocid femoral dataset used throughout this analysis ..................................................................................80 2.15 An ontogenetic trajectory in consideration of morphologic attributes for the Morrison diplodocid Diplodocus .......................................81 S.I.1 The juvenile Diplodocus specimens of the Mother’s Day Quarry ..................................................................................................123 S.I.2 The degrees and variation of neurocentral fusion in diplodocid cervical vertebrae ......................................................................124 S.I.3 Anterior cervical vertebrae of Mamenchisaurus and Diplodocus ...............124 ix LIST OF FIGURES – CONTINUED S.I.4 The sub-adult Diplodocus specimen MOR 592 compared to the adult Diplodocus carnegii .................................................................125 S.I.5 Neural spine morphology in the caudal vertebrae of Diplodocus specimens MOR 592 and CM 84 ............................................126 S.I.6 Neural spine bifurcation in diplodocid anterior most cervical vertebrae ........................................................................................127 S.I.7 Haplocanthosaurus incipient neural spine bifurcation ...............................127 S.I.8 Calculated body masses for the Morrison diplodocids Apatosaurus and Diplodocus ........................................................................128 S.I.9 Histologic and morphologic commonalities of Diplodocus (MOR 592) and Suuwassea emilieae ........................................129