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FORM AND FUNCTION OF THE LIMBS OF HEGETOTHERIINE NOTOUNGULATE HEMIHEGETOTHERIUM TRILOBUS FROM THE MIDDLE MIOCENE OF QUEBRADA HONDA, BOLIVIA By BETH R. CARROLL Submitted in pArtiAl fulfillment of the requirements for the degree of Master of Science DepArtment of Biology CASE WESTERN RESERVE UNIVERSITY May, 2019 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby Approve the thesis of Beth R. CArroll candidAte for the degree of Master of Science*. Committee Chair Karen Abbott Committee Member DArin A. Croft Committee Member Scott W. Simpson Committee Member Ryan Martin DAte of Defense March 22, 2019 *We Also certify thAt written Approval hAs been obtAined for Any proprietAry materiAl contAined therein 2 TABLE OF CONTENTS TABLE OF CONTENTS ……………………………………………………………... 3 LIST OF TABLES ………………………………………………………..…………… 5 LIST OF FIGURES ……………………………………………………………...……. 6 ACKNOWLEDGEMENTS ……………………………………………………………. 7 ABSTRACT ………………………………………………………………………….… 8 INTRODUCTION …………………………………………………………………….…8 Geologic And Geographic Context ………………………..……………...…11 MATERIALS AND METHODS …………………………………………………...….13 Methods ……………………………………………………………………......13 AnAtomical AbbreviAtions ………………………………………………….…14 Other AbbreviAtions ………………………………………………………..…14 MateriAls And Specimens ………………………………………………….…14 DESCRIPTION: THE FORELIMB …………………………………………...…...…18 The Shoulder And Arm ………………………………………………...…..…18 The ForeArm And Elbow ………………..………………………………….…22 The CArpus And Manus …………...……………………………………….…26 ArticulAtions in the CArpus ………………………………..……………….…28 ArticulAtions in the Manus ……………………………………...………….…33 The Forelimb Reconstructed ……………………………………..……….…34 DESCRIPTION: THE HINDLIMB ………………………………………...……….…39 The Hind Leg …………………………………………….………………….…39 The TArsals And Pes ……………………………………………………….…45 3 ArticulAtions in the TArsus …………………………………...…………...…50 ArticulAtions in the Pes ………………………………………………………55 The Hindlimb Reconstructed ……………………………………..……..….56 BODY MASS …………………………………………………….…………..…….…60 SUMMARY AND CONCLUSIONS …………………………………………...…….64 APPENDIX 1 ………………………………………………………………………….67 APPENDIX 2 …………………………………………………………………….……70 REFERENCES ………………………………………..……………………………...75 4 LIST OF TABLES Table 1- Body Mass meAsurements And calculAtions ……………………….……62 SupplementAry TAble 1- Long bone meAsurements ……………………………...67 SupplementAry TAble 2- MetAcarpAl And MetAtArsal meAsurements ………...…68 SupplementAry TAble 3- MeAsurements of PhAlAnges ………………………...…69 5 LIST OF FIGURES Figure 1- Map of QuebradA HondA, BoliviA ……………………………………..…11 Figure 2- Forelimb plAte with scapulA, humerus, And radius ………………….....20 Figure 3- PlAte of ArticulAted elbow……………………………………………….…21 Figure 4- PlAte of ArticulAted Manus …………………………………...……...…...24 Figure 5- IsolAted Elements of the Manus …………………………………...….....25 Figure 6- Reconstructed Manus in dorsal And ventral views bAsed on A cast….26 Figure 7- CArpAl ArticulAtions: tAxon compArison schematic …..…………...……32 Figure 8- Full skeleton reconstruction ………………………………………....……38 Figure 9- Femur plAte …………………………………………………………...……42 Figure 10- TibiofibulA PlAte …………………………………...……………...…...…44 Figure 11- IsolAted Elements of the Pes …………………………………......….…47 Figure 12- Reconstructed Pes in dorsal And ventral views bAsed on A cast …...48 Figure 13- PlAte of An ArticulAted Ankle,isolAted AstragAlus, And isolAted calcaneus …………………………………...…………………………………………49 Figure 14- TArsal ArticulAtions: tAxon compArison schematic ……………………54 Figure 15- All AstragAli used for BM meAsurements ………………………...……63 6 ACKNOWLEDGEMENTS First, I would like to express my gratitude to my thesis Advisor Dr. DArin Croft. The specimens described in this thesis were collected As pArt of A collAboration with the UniversidAd Autónoma “Tomas FríAs” in Potosí, BoliviA, And were collected during expeditions co-led by Dr. Federico AnAya of the FAcultAd de IngenieriA Geológica. Funding for this reseArch wAs provided by the NAtionAl Geographic Society Committee for ReseArch And Exploration (NGS 8115-06 to D. Croft) And the NAtionAl Science FoundAtion (EAR 0958733 And EAR 1423058 to D. Croft). I would Also like to thAnk A number of people At the ClevelAnd Museum of NAtural History. The CMNH Vertebrate Paleontology depArtment provided the spAce And some of the materiAls for the fossil prepAration. The CMNH Invertebrate Zoology lAb kindly provided the camera lucidA necessary for the illustrations. FinAlly, DAvid ChApman, the casting techniciAn in the Physical Anthropology depArtment At CMNH, provided lAb spAce And training for the molding And casting. 7 Form And Function Of The Limbs Of Hegetotheriine NotoungulAte Hemihegetotherium Trilobus From The Middle Miocene Of QuebradA HondA, BoliviA BETH CARROLL ABSTRACT Hemihegetotherium trilobus is A hegetotheriine notoungulAte from the middle Miocene (13-12 Ma) QuebradA HondA FAunA of Southern BoliviA. H. trilobus is A herbivore common At QuebradA HondA with hypselodont cheek teeth suited to consuming Abrasive plAnt materiAl either graze or browse. Herein, I describe the fore- And hindlimb osteology of H. trilobus bAsed on A number of well preserved specimens from QuebradA HondA. H. trilobus exhibits digitigrade limbs similAr to other typotheres with tetradActyl manus And pes including the Absence of digit I And reduction of digit V typical of hegetotheriids. The unguAl phAlAnges, however Are more similAr to MesotheriidAe thAn pAchyrukhine hegetotheriids. With A mass estimated 10kg, H. trilobus exhibits postcraniAl feAtures consistent with both cursoriAl And fossoriAl capAbilities. INTRODUCTION In groups thAt do not hAve extAnt relAtives, fossils Are often some of the few clues we hAve to identify how extinct Animals lived And behAved. EnvironmentAl dAtA And ichnofossils such As footprints And burrows can provide some context, but these cannot AlwAys directly be Assigned to A pArticulAr species. (Krapovickas et Al., 2009; CAtenA et Al., 2017) While osteology is greAtly influenced by phylogeny, it is Also shAped by evolutionAry AdAptAtions for lifestyle And behAvior. In modern mammaliAn tAxa, there Are often morphological feAtures 8 exhibited in unrelAted groups thAt correlAte with pArticulAr behAviors And lifestyles due to convergent or pArallel evolution. By looking At these morphological correlAtes in fossils thAt correspond to those in modern tAxa, musculAr forces And Actions can be reconstructed And in turn so can behAvior (Shockey et Al., 2007; Fernández-Monescillo et Al., 2017). NotoungulAtes Are A diverse order of mammals endemic to South America during the Cenozoic. They Are found in the fossil record As eArly As the Paleocene And the lAst went extinct during the Pleistocene Around 12,000 yeArs ago. NotoungulAtes spAn A wide range of body sizes And types, but Are generally divided into two suborders, ToxodontiA And TypotheriA. ToxodontiA includes the lArger, rhino- And horse-like forms And TypotheriA the smaller, rodent And rabbit- like forms. There Are no descendAnts of Any of NotoungulAtA todAy. (Croft, 2016) The evolution of And diversity of notoungulAtes And other mammals endemic to South America is interesting because for much of the Cenozoic South America wAs isolAted from the other continents (Croft And AnAya, 2006; Croft, 2007; Croft And Anderson, 2007; Croft, 2016; CArillo And Asher, 2017;SeoAne et Al., 2017). The AdAptAtions And morphologies thAt evolved in the South American mammals during the Cenozoic were independent of other mammals. Quite A few of these AdAptAtions were mirrored on other continents in response to similAr environmentAl pressures. HegetotheriidAe is A fAmily of small- to medium-sized typotheres. In general, typotheres were terrestriAl And herbivorous, usuAlly reconstructed As hAving generally rodent- or rabbit-like AppeArances And lifestyles (SinclAir, 1909; 9 Simpson, 1945; Croft And AnAya, 2006). Like other the other Miocene typotheres, InteratheriidAe And MesotheriidAe, hegetotheriids evolved simple evergrowing And rootless hypselodont cheek teeth ideAl for feeding on low growing Abrasive vegetAtion (Croft, 2007; McCoy And Norris, 2012; Croft, 2016). HegetotheriidAe is traditionAlly divided into two subfAmilies, HegetotheriinAe And PachyrukhinAe. The fossil record of HegetotheriidAe extends from the eArly Oligocene to the eArly Pleistocene (Croft And AnAya, 2006; Croft, 2007; Kramarz And Bond, 2016; SeoAne et Al., 2017). PachyrukhinAe is generally considered monophyletic (Kramarz And Bond, 2016; SeoAne et Al., 2017), but in HegetotheriinAe these relAtionships Are more uncleAr. Some Authors suggest the pAraphyletic nAture of HegetotheriinAe (Croft And AnAya, 2006; Kramarz And Bond, 2016) while some hAve proposed HegetotheriinAe is monophyletic (SeoAne et Al., 2017). The monophyly of Hemihegetotherium is Also under debAte. In recent studies, H. trilobus hAs been plAced either with other members of Hemihegetotherium (i.e., H. achataleptum) (Kramarz And Bond, 2016) And As A bAsal group of HegetotheriinAe sepArate from both H. achataleptum and H. torresi (SeoAne et Al., 2017). The suborder TypotheriA is represented At QuebradA HondA by three fAmilies: InteratheriidAe (Miocochilius federicoi), MesotheriidAe (Plesiotypotherium minor), And HegetotheriidAe (Hemihegetotherium trilobus) (Croft And AnAya, 2006; Croft, 2007). H. trilobus is the most AbundAnt typothere At QuebradA HondA And is the only one known from well preserved postcraniAl 10 remains. The AbundAnce of hegetotheriines At QuebradA HondA contrasts with contemporaneous site LA VentA, ColombiA, At which interatheres Are AbundAnt And mesotheres