University of Wollongong Research Online University of Wollongong Thesis Collection 1954-2016 University of Wollongong Thesis Collections 2016 Walking With Indonesian elephants: attribution of isolated proboscidean femurs and tibias to genus based on morphological differences Unggul Prasetyo Wibowo University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/theses University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. 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Recommended Citation Wibowo, Unggul Prasetyo, Walking With Indonesian elephants: attribution of isolated proboscidean femurs and tibias to genus based on morphological differences, Master of Philosophy thesis, School of Earth and Environmental Sciences, University of Wollongong, 2016. https://ro.uow.edu.au/theses/4803 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Walking With Indonesian Elephants: Attribution of Isolated Proboscidean Femurs and Tibias to Genus Based on Morphological Differences A thesis submitted in fulfilment of the requirements for the award of the degree Master of Philosophy From University of Wollongong by Unggul Prasetyo Wibowo Department of Science, Medicine and Health 2016 CERTIFICATE OF ORIGINALITY I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of a university or other institute of higher learning except where due acknowledgment is made in the text. I also declare that the intellectual content of this thesis is the product of my own work, even though I may have received assistance from others on style, presentation and language expression. Unggul Prasetyo Wibowo (Signed)……………………….................................................................... Date: 25/08/2016 ABSTRACT Direct comparison and biometric measurement analysis of homologue skeletal elements pertaining to distinct members of closely related vertebrate taxa (genera and species) can reveal qualitative diagnostic distinctive characteristics that reflect phylogeny and that may be related to differences in functional morphology. Apart from morphological differences, size can be an important factor in distinguishing taxa, especially when considering dwarfed insular proboscideans. Dwarfed proboscideans were once present on several islands of Indonesia during the Quaternary, but their postcranial remains have hardly been studied in detail. Most studies on fossil proboscideans focus on cranial and dental elements, which are comparatively easy to distinguish. In the case of proboscidean limb bones, morphological differences may be associated with different types of locomotion and could represent specific adaptations to insular environments. In order to investigate such adaptive morphologies in detail, a first step is to assess which differences exist between closely related genera. Establishing a list of diagnostic criteria to distinguish limb bones of different proboscidean genera and species will also aid in identifying isolated specimens of these elements. This study applied biometric analysis combined with 3D Geometric Morphometric (GM) analysis of fossil and recent skeletal parts of Indonesian proboscideans. The study aimed at characterizing the morphological differences between proboscidean taxonomic groups of two skeletal elements, the femur and the tibia. These elements were chosen because complete specimens of femur (n=10) and tibia (n=10) of known identity (based on associated dental elements) are relatively common in Indonesian fossil collections and were easily accessible. The studied sample comprises a recently excavated femur and tibia of a single adult individual of the very small-sized Stegodon sondaari from Flores. This offered the opportunity for the first time to investigate if this insular dwarf proboscidean possessed specific adaptations (apart from its small size) that are frequently encountered in insular megafauna, such as shortened distal limbs. First a surface morphology assessment and Principal Component Analysis (PCA) of biometric variables taken from the literature were performed on femurs and tibias of known species pertaining to the genera Stegodon, Elephas and Sinomastodon. PCA resulted in only a weak grouping predominantly according to size. Because dwarfed proboscidean taxa were included in the PCAs, size differences rather than morphological differences tended to i dominate the grouping outcome. Next, a Geometric Morphometric (GM) analysis was performed on the same specimens to investigate additional shape differences of femurs and tibias. All specimens were 3D scanned and a set of meaningful 3D landmarks was defined. Following size and orientation adjustments of the 3D coordinates (procrustes registration) a PCA was performed on the 3D shapes combined with visualization of the outcome with wireframe images. This revealed a set of additional distinctive morphological features for both the femur and the tibia. Stegodon and Sinomastodon both have a more robust femur and tibia than Elephas. This is expressed by the new composite variable Total Length/Minimum Circumference, which is significantly smaller in Stegodon and Sinomastodon than in Elephas. For the femur other new variables that separate genera are the length of the third trochanter and the angle of shaft rotation. The third trochanter is longer and more flaring outward in Stegodon and Sinomastodon than in Elephas, which has a weakly developed third trochanter and as a result a more columnar femur. The angle of femur rotation in Elephas shows greater values than in most Stegodon and Sinomastodon, with the exception of Stegodon sondaari, which has a rotational angle even greater than in Elephas. Regarding the tibia, all Stegodon specimens have a markedly deeper and longer medial collateral ligament (MCL) attachment scar than in Elephas (no Sinomastodon tibia was available for study). The differences between Stegodon and Elephas suggest that the Elephas hindlimb is designed to restrict movement and reduce energy consumption, while the Stegodon hindlimb is more flexible in movement during locomotion and has a higher strength and robustness. The more slender and columnar hindlimb of Elephas is shared with Mammuthus and supports a shared close common ancestry for these genera, while the more robust hindlimb bones of Stegodon and Sinomastodon are the primitive character state that is shared with Mammut. These results support classification of Elephas and Stegodon into distinct subfamilies. The Stegodon sondaari hindlimb is morphologically different from all other Stegodon species examined, in showing a mixture of advanced and primitive morphologies. The S. sondaari femur has the longest and most widely flaring third trochanter of all taxa investigated, and its femur rotation angle is even greater than in Elephas. Although S. sondaari does not appear to exhibit a relative shortening of the distal hindlimb, its specific hindlimb morphology may reflect an adaptation to locomotion in a rugged and steep mountainous terrain. However, more fossil material would be required to verify this hypothesis, particularly of the pelvis. ii ACKNOWLEDGEMENTS I gratefully acknowledge the University of Wollongong for providing me with a scholarship for this research. Fieldwork in Flores and visits to the various museums in Central Java were financed by an Australian Research Council (ARC) Discovery grant to Mike Morwood/Gert van den Bergh (DP1093342). I would like to express my deep appreciation to my supervisors Dr. Gerrit van den Bergh and Dr. Susan Hayes for their help, encouragement and guidance during the study. I’m also indebted to the Head of Postgraduate Studies, Dr. Samuel Marx, the former Head of the School of Earth & Environmental Sciences of the University of Wollongong, Professor Colin Murray Wallace and Professor Zenobia Jacobs. Special gratitude also goes to all academic, administrative and technical staff of the department. Special thanks are forwarded to the former Head of the Geological Agency, Energy and Mineral Resources Ministry (EMRM) of Indonesia, Dr. Surono; the Expert Staff for Spatial Planning and Environment of EMRM, Dr. Yunus Kusumahbrata;