Foot-ground-body relationships in the American Alligator
Alligators are capable of postural extremes—from a belly sprawl to a high walk—and the ankle is mobile enough in all three degrees of rotational freedom to achieve foot-ground contact across these diverse hindlimb poses. Alligator ankle anatomy and function has historically focused on the hinge-like peg-and-socket joint between the proximal tarsals (astragalus and calcaneum) and has largely ignored the complex set of bones that make up the ankle and foot.
For the first time, we are able to reconstruct 6 degree-of-freedom movement for all bones in the distal limb across a variety of locomotor behaviors. Such a large multi-bone dataset poses several animation and data visualization challenges — addressing these have been the highlight of my PhD thesis. The ability to identify kinematic patterns and relationships to morphological features is critical for further interpretation of locomotor diversification in extinct Archosaur ancestors, many of which retain the same distinct ankle and foot structure. Much more work to come out of this research, stay tuned!
Collaborator: Stephen Gatesy
Turner ML and Gatesy SM. (In Review). Alligators employ intermetatarsal reconfiguration to modulate plantigrade ground contact. Submitted to the Journal of Experimental Biology.
Turner ML and Gatesy SM (2021). Intermetatarsal mobility in the American alligator. Society of Integrative and Comparative Biology Annual Meeting [virtual].
Turner ML and Gatesy SM (2020). Intermetatarsal mobility and grades of foot contact in the American alligator: building a new perspective on archosaurian foot evolution. Society of Vertebrate Paleontology Annual Meeting [virtual].
Dinosaur footprint formation
A long-standing area of research between Stephen Gatesy and Peter Falkingham, I joined this collaboration as a 1st year graduate student. The driving question “What are the sources of dinosaur footprint variation?” has led us down an exciting path of muddy experiments and data visualization challenges. Our work has revealed strong connections between foot movement through soft substrates and landmarks preserved in fossil tracks–permitting morphological frameworks to be constructed and hypotheses of dinosaur foot motion to be tested. Collaboration with Virtual Reality and data visualization experts were invaluable, as the development of a room-sized application allowed us to interactively explore and gain intuition of patterns occurring within our spatiotemporally complex data.
Collaborators: Peter Falkingham, Stephen Gatesy, Johannes Novotny, Joshua Tveite, Fritz Drury, David Laidlaw
Falkingham PL, Turner ML, Gatesy SM. (2020). Constructing and testing hypotheses of dinosaur foot motions from fossil tracks using digitization and simulation. Palaeontology. https://doi.org/10.1111/pala.12502
Turner ML, Falkingham PL, Gatesy SM.(2020). It’s in the loop: shared subsurface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity. Biology Letters. 16: 20200309. http://dx.doi.org/10.1098/rsbl.2020.0309
Novotny J, Tveite J, Turner ML, Gatesy SM, Drury F, Falkingham P, Laidlaw DH. (2019). Developing Virtual Reality Visualizations for Unsteady Flow Analysis of Dinosaur Track Formation using Scientific Sketching. IEEE Transactions on Visualization and Computer Graphics. https://doi.org/10.1109/TVCG.2019.2898796
Turner ML, Novotny J, Falkingham PL, Laidlaw DH, Gatesy SM. (2019). Where does footprint morphology come from? Developing virtual reality visualizations for exploring dinosaur track formation. International Congress of Vertebrate Morphology. (Invited symposium talk).
Falkingham PL, Turner ML, Gatesy SM. (2019). Generating and Testing Hypotheses of Dinosaur Foot Motions Using 3D-Digitized Tracks and Large-Scale Granular Simulations. International Congress of Vertebrate Morphology.
Novotny J, Tveite JJ, Turner ML, Gatesy SM, Falkingham PL, Laidlaw, DH. (2018). Developing a Virtual Reality Application for Unsteady Flow Analysis in Dinosaur Track Creation. IEEE VIS (Visual analytics science and technology, Information visualization, Scientific visualization). (Best Poster Award)
Turner ML, Falkingham PL, Gatesy SM. (2018). Where does footprint morphology come from? Integrating 3D methods for exploring dinosaur track formation. Society of Vertebrate Paleontology Annual Meeting. (Invited symposium talk).
Gatesy SM, Turner ML, Falkingham, PL. (2018). CT Imaging of Dinosaur Footprints: Hidden Topography and the Origin of Track Diversity. Society for Integrative and Comparative Biology Annual Meeting.
Turner ML, Falkingham PL, Gatesy SM. (2017). Sub-Surface Foot-Trajectories and Fossil Dinosaur Tracks. Last Days of Pangea Triassic-Jurassic Research Symposium.
Insights from Pareiasaurian morphology
As an undergraduate at the University of Washington and Burke Museum of Natural History and Culture, my first research projects were on Pareiasaurs, an extinct group of terrestrial herbivorous reptiles that lived during the middle to late Permian (265–252 Ma).
Collaborators: Christian Sidor, Linda Tsuji, Oumarou Ide
Turner ML and Sidor CA. (2017). Pathology in a Permian Parareptile: Congenital Malformation of Sacral Vertebrae. Journal of Zoology. https://doi.org/10.1111/jzo.12519
Turner ML, Tsuji LA, Ide O, Sidor CA. (2015). The vertebrate fauna of the Upper Permian of Niger—IX. The appendicular skeleton of Bunostegos akokanensis (Parareptilia: Pareiasauria). Journal of Vertebrate Paleontology 35, e994746. https://doi.org/10.1080/02724634.2014.994746
Turner ML, Sidor CA, Tsuji LA. (2015). Removing assumptions of anatomical orientation from cladistic characters: an example from pareiasaurs. Society of Vertebrate Paleontology Annual Meeting.
Turner ML, Tsuji LA, Sidor CA. (2014). Evidence for the earliest evolution of a fully parasagittal quadruped. Society of Vertebrate Paleontology Annual Meeting.
Turner ML, Tsuji LA, Sidor CA. (2013). The Ontogeny of the Scapulocoracoid of the Pareiasaur Bunostegos akokanensis (Amniota: Parareptilia) from the Permian of Niger. Undergraduate Research Symposium, University of Washington.
Collaborating with other researcher-led projects has presented some exciting data visualization challenges (and solutions)!
Alligator hip cartilage interactions
Tsai HP, Turner ML, Manafzadeh AR, Gatesy SM. (2020). Contrast-enhanced XROMM reveals in vivo soft tissue interactions in the hip of Alligator mississippiensis. Journal of Anatomy. https://doi.org/10.1111/joa.13101
Drone footage of a swimming crocodile
Farlow JO, Robinson NJ, Turner ML, Black J, Gatesy SM. (2018). Footfall Pattern of a Bottom-Walking Crocodile (Crocodylus acutus). Palaios 33(9):406-413. https://doi.org/10.2110/palo.2018.037