I am interested in the forelimbs of dinosaurs because they played so many diverse roles from grasping to body support. The common ancestor of all dinosaurs was a biped that used its forelimbs for capturing prey or manipulating food. However, several groups of dinosaurs became quadrupeds, converting the forearm into a foreleg. One quadrupedal group, called the sauropods, became the largest animals ever to walk on land, and a lot of my research has been dedicated to understanding the role of their forelimbs in locomotion, posture, and support before and after they became giants.
To seek the answers to my paleontology questions I have traveled the globe to study dinosaur skeletons in the field and at museums. A highlight of my career has been National Geographic-sponsored field work with an international team of colleagues in South Africa which led to the discovery of three new species of plant-eating dinosaurs closely related to the common ancestor of the giant sauropods. One of these dinosaurs, Aardonyx, was a transitional fossil that shows the beginnings of the switch from bipedal to quadrupedal locomotion.
More recently, in the laboratory, my colleagues, students, and I are using using a technique called XROMM (X-ray Reconstruction of Moving Morphology) to non-invasively study how the bones in the forelimbs of living birds, reptiles, and mammals move. We are using these data to test hypotheses about the evolution of forelimb posture in the ancestors of mammals and dinosaurs. I have also dabbled in a few shark studies, including a recent exploration of newborn size and growth in the giant fossil shark Megalodon.
Paleontology
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Voegele, K.K., M.F. Bonnan, S. Siegler, C.R. Langel, and K.J. Lacovara. 2022. Constraining Morphologies of Soft Tissues in Extinct Vertebrates Using Multibody Dynamic Simulations: A Case Study on Articular Cartilage of the Sauropod Dreadnoughtus. Frontiers in Earth Science, 13 June 2022. https://doi.org/10.3389/feart.2022.786247
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Ullmann, P.V., M.F. Bonnan, and K.J. Lacovara. 2017. Characterizing the evolution of wide-gauge features in stylopodial limb elements of titanosauriform sauropods via geometric morphometrics. The Anatomical Record, DOI: 10.1002/ar.23607
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McPhee, B.W., Bonnan, M.F., Yates, A.M., Neveling, J., and Choiniere, J.N. 2015. A new basal sauropod from the pre-Toarcian Jurassic of South Africa: evidence of niche-partitioning at the sauropodomorph-sauropod boundary? Scientific Reports 5: doi:10.1038/srep13224.
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Xing, L., Lockely, M.G., Bonnan, M.F., Marty, D., Klein, H., Liu, Y., Zhang, J., Kuang, H., Burns, M.E., and Li, N. 2015. Late Jurassic-Early Cretaceous trackways of small-sized sauropods from China: new discoveries, ichnotaxonomy and sauropod manus morphology. Cretaceous Research 56:470-481. http://dx.doi.org/10.1016/j.cretres.2015.06.014
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Yates, A.M., Bonnan, M.F., Neveling, J., Chinsamy, A., and Blackbeard, M. 2009. A new transitional sauropodomorph from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proceedings of the Royal Society, London, B: DOI: 10.1098/rspb.2009.1440.
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Bonnan, M.F. 2007. Linear and geometric morphometric analysis of long bone scaling patterns in Jurassic Neosauropod dinosaurs: their functional and paleobiological implications. The Anatomical Record, 290(9): 1089-1111. ABSTRACT
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Bonnan, M.F. and P. Senter. 2007. Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds?; pp. 139-155 in Barrett, P. M. and D.J. Batten (eds.), Evolution and palaeobiology of early sauropodomorph dinosaurs. Special Papers in Palaeontology, 77.
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Bonnan, M.F. and A.M. Yates. 2007. A new description of the forelimb of the basal sauropodomorph Melanorosaurus: implications for the evolution of pronation, manus shape and quadrupedalism in sauropod dinosaurs; pp. 157-168 in Barrett, P. M. and D.J. Batten (eds.), Evolution and palaeobiology of early sauropodomorph dinosaurs. Special Papers in Palaeontology, 77.
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Bonnan, M.F. 2005. Pes anatomy in sauropod dinosaurs: implications for functional morphology, evolution, and phylogeny; pp. 346-380 in K. Carpenter and V. Tidwell (eds.), Thunder-Lizards: The Sauropodomorph Dinosaurs. Bloomington, IN: Indiana University Press.
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Bonnan, M.F. and M.J. Wedel. 2004. First occurrence of Brachiosaurus (Dinosauria: Sauropoda) from the Upper Jurassic Morrison Formation of Oklahoma. PaleoBios, 24(2): 13-21.
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Bonnan, M.F. 2004. Morphometric analysis of humerus and femur shape in Morrison sauropods: implications for functional morphology and paleobiology. Paleobiology, 30(3): 444-470.
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Bonnan, M.F. 2003. The evolution of manus shape in sauropod dinosaurs: implications for functional morphology, forelimb orientation, and sauropod phylogeny. Journal of Vertebrate Paleontology, 23(3): 595-613.
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Bonnan, M. F. 2000. The presence of a calcaneum in a diplodocid sauropod. Journal of Vertebrate Paleontology, 20(2): 317-323.
Functional Morphology & XROMM
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Langel, C.R. and M.F. Bonnan. 2023. Ontogenetic Changes in the Cross-Sectional Geometry and Deltopectoral Crest of the Humerus in Alligator mississippiensis; pp. 68-79 in H.N. Woodward and J.O. Farlow (eds.), Ruling Reptiles: Crocodylian Biology and Archosaur Paleobiology. Indiana University Press. 417 p.
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Bonnan, M.F., J. Shulman, R. Varadharajan, C. Gilbert, M. Wilkes, A. Horner, and E. Brainerd. 2016. Forelimb kinematics of rats using XROMM, with implications or small eutherians and their fossil relatives. PLoS ONE 11(3): e0149377. doi:10.1371/journal.pone.0149377 Click here for Open Access article.
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Bonnan, M.F., Wilhite, D.R., Masters, S.L., Yates, A.M., Gardner, C.K., and Aguiar, A. 2013. What Lies Beneath: Sub-Articular Long Bone Shape Scaling in Eutherian Mammals and Saurischian Dinosaurs Suggests Different Locomotor Adaptations for Gigantism. PLoS ONE 8(10): e75216. doi:10.1371/journal.pone.0075216
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VanBuren, C.S. and Bonnan, M.F. 2013. Forearm posture and mobility in quadrupedal dinosaurs. PLoS ONE 8(9): e74842. doi:10.1371/journal.pone.0074842
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Livingston, V.J., Bonnan, M.F., Elsey, R.M., Sandrik, J.L., and Wilhite, D.R. 2009. Differential limb scaling in the American Alligator (Alligator mississippiensis) and its implications for archosaur locomotor evolution. The Anatomical Record, 292: 787-797.
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Bonnan, M.F., J.O. Farlow, and S.L. Masters. 2008. Using linear and geometric morphometrics to detect intraspecific variability and sexual dimorphism in femoral shape in Alligator mississippiensis and its implications for sexing fossil archosaurs. Journal of Vertebrate Paleontology, 28(2): 422-431.
Sharks & Other
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Shimada, K., M. F. Bonnan, M. A. Becker, and M. L. Griffiths. 2021. Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon —implications for its reproductive biology, development, and life expectancy. Historical Biology https://doi.org/10.1080/08912963.2020.1861608
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Reiss, K.L., and Bonnan, M.F. 2010. Ontogenetic scaling of caudal fin shape in Squalus acanthias (Chondrichthyes, Elasmobranchii): a geometric morphometric analysis with implications for caudal fin functional morphology. The Anatomical Record, 293:1184–1191.
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Bonnan, M.F. 2006. REVIEW: Chinsamy-Turan: The Microstructure of Dinosaur Bone: Deciphering Biology with Fine-Scale Techniques. Journal of Vertebrate Paleontology, 26(1): 233-234.
Paleontologist | Professor | Author | Science Communicator | Singer/Songwriter