Patrick Gillespy: "Ontogenetic Change in Distal and Proximal Limb Bones in Pleistocene Coyotes (Canis Latrans)
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ONTOGENETIC CHANGE IN DISTAL AND PROXIMAL LIMB BONES OF JUVENILE PLEISTOCENE COYOTES (Canis latrans) AND DIRE WOLVES (Canis dirus) FROM THE RANCHO LA BREA TAR PITS, CALIFORNIA A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Geological Sciences By Patrick D. Gillespy 2018 SIGNATURE PAGE THESIS: ONTOGENETIC CHANGE IN DISTAL AND PROXIMAL LIMB BONES OF JUVENILE PLEISTOCENE COYOTES (Canis latrans) AND DIRE WOLVES (Canis dirus) FROM THE RANCHO LA BREA TAR PITS, CALIFORNIA AUTHOR: Patrick D. Gillespy DATE SUBMITTED: Spring 2018 Geological Sciences Department Dr. Jonathan A. Nourse Thesis Committee Chair Geological Sciences Dr. Donald R. Prothero Geological Sciences Dr. Bryan P. Murray Geological Sciences ii ACKNOWLEDGEMENTS The expertise and help of those around me was invaluable to the completion of this thesis project, without which I would have had added difficulty to an already laborious process. I would like to devote this section to those who gave me their time, in whatever form it may have taken. Thank you to my advisor, Dr. Don Prothero, for his expertise in paleontology and willingness to impart that knowledge. Your ability to convey concepts new and old will continue to keep me interested in the life that has existed in the ancient past, still exists today, or may exist in the future. Urging me to attend conferences has brought me out of old comfort zones into the realm of new possibilities. Thank you to Johnnie French of the U.S. Fish and Wildlife Service for dedicating time out of your busy day to collect data that was beyond my reach and thereby contributing to this project. Thank you to the La Brea Tar Pits and Museum staff, especially collection managers Aisling Farrell and Gary Takeuchi, for making the time for me to come in and explore your extensive collections. An additional thank you is in order for the members of the Department of Vertebrate Paleontology of the Los Angeles County Natural History Museum, notably Vanessa Rhue, for your insight and skills in training me on how to properly catalogue, handle, and prepare fossil specimens. To the faculty and staff of the Geological Sciences department of Cal Poly Pomona, thank you for putting up with my incessant questions about coursework and this thesis itself. Hopefully you see some of your advice and geologic teachings imparted herein, as I took everything to heart and mind. iii Thank you to my family for your company and pushing me to be the first to achieve what you were unable to. Exposing me to the many experiences and views in this world broadened my horizons. Your help and life experiences mean a great deal to me. Thank you to my friends, old and new, for believing in my abilities, even when I found my own lack of faith disturbing. Some of whom I respectfully follow in your footsteps, as you have toiled in graduate programs of your own, and others who have embarked on further studies. It is a dangerous business, stepping out onto this road— there is no knowing where you might be swept off to. Finally, thank you to my wife, Caitie, for lending a sympathetic ear to my lengthy scientific explanations and tangents. It is more appreciated than you could possibly imagine, even if you do not always understand what I am saying. Thank you for encouraging all that I love as much as you love the tiny Atelerix albiventris. It may not be normal, but it is natural. If I could, I would throw a lasso around the moon and give it to you. Just say the word. iv ABSTRACT Large sample sizes of juvenile animal fossils are rare compared to their adult counterparts. The preponderance of adult specimens in the fossil record overshadows the entire ontogenetic growth series of an organism from the earliest stages of life and onward. This is partially because the fragile parts of younger individuals are typically poorly preserved. However, the natural asphalt seeps of the Rancho La Brea Tar Pits have yielded spectacular quantities of specimens young and old, allowing for a more complete investigation of ontogenetic growth series. We collected long bone length, thickness, and circumference data from nearly 800 separate appendicular skeleton elements across three canid species; Pleistocene coyotes (Canis latrans) and dire wolves (Canis dirus), as well as modern gray wolves (Canis lupus). Standardized major axis bivariate regressions were used to determine the ontogenetic change in limb bones and the deviation from the line of isometry (“same growth”). Using regression slopes as a proxy for long bone allometry, we were able to compare the growth patterns of the extinct canids to other cursorial animals and their modern counterparts. We found that C. latrans, C. dirus, and C. lupus long bone growth series are positively allometric, with bones growing longer faster than they do thicker. The degree of positive allometry is typically more pronounced in the distal elements than the proximal elements. This suggests an increasing degree of gracility in the distal elements compared to the relatively robust proximal elements. As expected of animals adapted to a running lifestyle, the increasing gracility of long bones would allow for a much more efficient running locomotion behavior. This would be beneficial while hunting, much like the modern gray wolf when in pursuit of smaller and faster prey. These statistical results show that coyote and dire wolf growth series are v typical of other cursorial animals during ontogeny, regardless of climatic influences on body size changes during the glacial and interglacial periods of the Pleistocene. vi TABLE OF CONTENTS SIGNATURE PAGE ......................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................ iii ABSTRACT ....................................................................................................................... v LIST OF TABLES ........................................................................................................... ix LIST OF FIGURES ......................................................................................................... xi CHAPTER 1 – INTRODUCTION .................................................................................. 1 1.1 GEOLOGIC SETTING .......................................................................................... 5 1.1.1 REGIONAL SETTING ........................................................................................ 5 1.1.2 TECTONIC SETTING ........................................................................................ 7 1.1.3 STRATIGRAPHY .............................................................................................. 10 1.1.4 NATURAL RESOURCES .................................................................................. 12 1.1.5 CLIMATE.......................................................................................................... 18 1.1.6 FAUNA ............................................................................................................. 20 CHAPTER 2 – METHODS ........................................................................................... 25 2.1 MEASUREMENT DETAILS .............................................................................. 25 2.2 EQUIPMENT AND SOFTWARE ....................................................................... 33 2.3 ISOMETRY AND ALLOMETRY ...................................................................... 35 2.4 STATISTICS: WHY ALLOMETRIC REGRESSIONS? ................................. 35 CHAPTER 3 – RESULTS .............................................................................................. 40 3.1 DATA ANALYSIS ................................................................................................ 40 3.2 C. latrans ALLOMETRY ..................................................................................... 41 3.3 C. lupus ALLOMETRY ........................................................................................ 41 3.4 C. dirus ALLOMETRY......................................................................................... 42 CHAPTER 4 – DISCUSSION AND INTERPRETATION ........................................ 49 4.1 DISCUSSION ........................................................................................................ 49 4.2 INTERPRETATION ............................................................................................ 49 4.2.1 C. latrans .......................................................................................................... 49 vii 4.2.2 C. lupus ............................................................................................................. 50 4.2.3 C. dirus ............................................................................................................. 51 4.3 PROXIMAL VS. DISTAL LIMB BONES ......................................................... 61 CHAPTER 5 – CONCLUSIONS AND FUTURE WORK ......................................... 68 5.1 CONCLUSIONS ................................................................................................... 68 5.2 FUTURE WORK .................................................................................................. 68 REFERENCES ................................................................................................................ 70 APPENDIX