EVOLUTIONARY STUDIES INSTITUTE, SCHOOL OF GEOSCIENCES AND SCHOOL OF ANIMAL, PLANT AND ENVIRONMENTAL SCIENCES UNIVERSITY OF THE WITWATERSRAND A postural validation for the limb loadings in Thrinaxodon liorhinus (Therapsida, Cynodontia)

by Finite Element Analysis

Engineering Simulation Conference 2018 3 September 2018 African Pride Irene, Pretoria

Safiyyah Iqbal [email protected]

Co-Authors: Prof. Kristian J. Carlson http://www.blc.arizona.edu/courses/schaffer/182/Anapsid-Therapsid.htm Prof. Fernando Abdala Prof. Frank Kienhofer Prof. Jonah Choiniere Acknowledgments I sincerely thank the following departments in making this research possible! Background Cynodonts

• Appear in the Late Permian and dominate in the Early Triassic

• Best documented sequence in the fossil record

• Transitional lineage

• Features in these fossil forms

• Functional adaptations in order to understand behaviour http://dinosauriosjavier.blogspot.com/2012/06/el-cynodont.html

Why Thrinaxodon? Thrinaxodon liorhinus

• Semi-sprawling posture

• Primitive and derived

features are represented http://bio.sunyorange.edu/updated2/comparative_anatomy/anat_3/l_femur.htm in cynodonts

• Posture of Thrinaxodon will offer insight into the transition that led to humerus radius/ulna mammals

Significance of Study • Multidisciplinary approach

• Builds on previous research of the first attempt to study the functional morphology of Thrinaxodon

• Research focuses on the loading conditions of remodelling skeletal elements

http://biology- forums.com/index.php?action • This will provide robust evidence of the type =gallery;sa=view;id=8280 of limb posture that characterized this ancestral mammal as the limb structure transitioned from reptilian to mammalian.

http://borbl426-526.blogspot.com/2012/01/lab-1-reptile- development-and-anatomy.html Problem and Goal for this research Problem and Main Goal • Problem: Mechanical loads are applied to bone over time, influence morphology and in turn impacts functional adaptations.

• Main Goal: Using Finite Element Analysis (FEA) to test hypotheses of reconstructed limb postures in the transitional cynodonts.

http://www.bris.ac.uk/news/2009/6547.html Hypotheses and Aims Hypotheses • Thrinaxodon forelimb posture is optimised for semi-sprawling gaits

• Thrinaxodon hindlimb posture is http://www.deviantart.com/morelikethis/artists/609 optimised for parasagittal gaits 11804?view_mode=2#skins

Aims

• Determine mechanical response experienced by the humeri and femora during different posture configurations. http://www.savalli.us/BIO370/Anatomy/5.AlligatorSkeleton.html • Relate individual limb bones to overall limb morphology in order to identify the optimal state for a given posture.

• Relate configurations of extant analogs http://www.environment.gov.au/biodiversity/abrs/publi cations/fauna-of-australia/pubs/volume1b/32-ind.pdf Materials and Methods Material - Comparative species The humeri and femora were analysed. Humeri Femora

• Thrinaxodon was compared to: http://commons.wikimedia.org/wiki/File:Thrinaxodon_liorhinus _BP_1_7199.jpg ▫ Galesaurus – Fossorial

▫ Therocephalia – Non-fossorial

▫ Cynognathus – Non-fossorial

http://www.snipview.com/q/Galesaurus ▫ Tachyglossus - Fossorial

http://global.britannica.com/animal/Cynognathus

http://wiredspace.wits.ac.za/bitstream/handle/10539/13813/2009.v.44.FOURIE_AN D_RUBIDGE_Postcranial_skeleton_of_Glanosuchus.pdf?sequence=1 Materials and Methods Methodology

1. MicroCT 2. VG Studio Max/Avizo

http://www.ansys.com/Products/Workflow+Technology/ 3. Geomagic Studio 14.0 ANSYS+Workbench+Platform/Features 4. ANSYS

https://www.mech.kuleuven.be/en/bme/research/bone • Cross-sectional properties ▫ ImageJ v1.50i ▫ BoneJ ▫ Cortical Area ▫ Second Moments ▫ Principal Moments

http://biomechanics.stanford.edu/ Figure adapted from Doube et al. 2009) Mechanics_of_growth Materials and Methods Methodology • FEA • ANSYS ▫ Model Creation ▫ Elements were modelled as solids Mechanical Properties: • Modelling the fossil as Bovine Constraints and Boundary Conditions • Fixed Support: Condyle attachments • Muscle forces

▫ Model Solving ▫ Stress ▫ Strain Results Results • FEA ▫ Deformation

Results Results - Humeri Therocephalia sp. Cynognathus Galesaurus

Thrinaxodon Tachyglossus Results Results - Humeri 8,00E-04 Total Deformation (mm)

Directional Deformation (mm) 7,00E-04 Equivalent Elastic Strain (mm/mm)

Equivalent (Von-Mises) Stress (MPa) 6,00E-04

5,00E-04

4,00E-04 Mean 3,00E-04

2,00E-04

1,00E-04

4,40E-18 BPI1675 BPI1693 BPI1730 BPI4335 BPI4506 BPI6228 BPI7199 Tachyglossus

-1,00E-04

Species Results Results - Femora Therocephalia sp. Cynognathus Galesaurus

Thrinaxodon Tachyglossus Results Results - Femora 8,00E-04 Total Deformation (mm)

Directional Deformation (mm) 7,00E-04 Equivalent Elastic Strain (mm/mm)

6,00E-04 Equivalent (Von-Mises) Stress (MPa)

5,00E-04

4,00E-04 Mean 3,00E-04

2,00E-04

1,00E-04

2,60E-18 BPI1675 BPI1693 BPI1730 BPI4335 BPI4506 BPI6228 BPI7199 Tachyglossus

-1,00E-04

Species Discussion • Change in posture

• Significant differences among each gait

• Factors that affect the stress and strain of limb bones http://biology- ▫ Muscle attachments forums.com/index.php?action =gallery;sa=view;id=8280 • Gait pressure – Torsion of the humeri

http://borbl426-526.blogspot.com/2012/01/lab-1-reptile- development-and-anatomy.html Future Directions

• Assumptions • Non-invasive

http://www.uky.edu/KGS/education/Imgtriassic.htm

• Inferred properties for standing phase • Extant data – Validation • Different diaphyseal length • Postcranial elements

http://farm4.staticflickr.com/3002/2417900765_48e0eaec27.jpg References

• ABDALA, F. and RIBEIRO, A. M. 2010. Distribution and diversity patterns of Triassic cynodonts (Therapsida, Cynodontia) in Gondwana. Palaeogeography, Palaeoclimatology, Palaeoecology 286: 202-217. • ABDALA, F., JASINOSKI, S. C. and FERNANDEZ, V. 2013. Ontogeny of the Early Triassic cynodont Thrinaxodon liorhinus (Therapsida): dental morphology and replacement. Journal of Vertebrate Palaeontology 33: 1408-1431. • BENNETT, A. F. and RUBEN, J. A. 1986. The metabolic and thermoregulatory status of therapsids. In the The ecology and biology of mammal-like reptiles. Smithsonian Institute Press. Washington. D.C. USA. • BIEWENER, A. A. 1989. Mammalian terrestrial locomotion and size. American Institute of Biological Sciences 39: 776-783. • BLOB, R. 2001. Evolution of hindlimb posture in nonmammalian therapsids: biomechanical tests of paleontogical hypotheses. Paleobiological 27: 14-38. • BLOB, R. W. and BIEWENER, A. A. 1999. In vivo locomotor strain in the hindlimb bones of Alligator mississippiensis and Iguana iguana: implications for the evolution of limb bone safety factor and non-sprawling limb posture. The Journal of Experimental Biology 202: 1023-1046. • BUTLER, E. 2009. The postcranial skeleton of the Early Triassic non-mammalian cynodont Galesaurus planiceps: implications for biology and lifestyle. MSc Dissertation. University of the Free State. Bloemfontein. • BOTHA, J. and SMITH, R. M. H. 2006. Rapid vertebrate recuperation in the Karoo Basin of South Africa following the End-Permian extinction. Journal of African Earth Sciences 45: 502-514. • CROMPTON, A. W. and JENKINS, F. A. Jr. 1973. Mammals from reptiles: A review of mammalian origins. Annual Review of Earth and Planetary Science 1: 131-155. • DAMIANI, R., MODESTO, S., YATES, A. and NEVELING, J. 2003. Earliest evidence of cynodont burrowing. Proceedings of the Royal Society of London: Biological Sciences 270: 1747-1751. • FOURIE, H. and RUBIDGE, B. S. 2009. The postcranial skeleton of the basal therocephalian Glanosuchus macrops (Scylacosauridae) and comparison of morphological and phylogenetic trends amongst the Theriodontia. Palaeontologica Africana 44: 27-39.

• Contact: Safiyyah Iqbal for more information Questions?