Final PhD Seminar

CT investigations of Devonian fossil fishes from Australia and applications of scientific visualization in vertebrate morphology.

Miss Yuzhi Hu
Department of Applied Mathematics, Research School of Physics ANU

Fossils represent the history of life and have always been the key to raising hypotheses of evolution. Australia is well-known for its great fossil fish resources in the Devonian (also known as the Age of Fishes). Previous functional morphology reconstruction of fossils was mainly graphical (i.e. presented as how the elements are imagined to fit together) because of the risk of breakage of bones. New techniques - high resolution computed tomography, scientific visualisation and 3D printing, allowing physical reconstruction of fossils possible.

In this talk, I first presented the digital reconstruction of the shoulder girdle and opercular series based on micro-CT data and manipulation of 3D printouts permitted testing of the morphological fit of extremely fragile acid-etched bones of a lobe-finned fish Gogonasus. Following this pathway, previous assumptions about jaw structure and function were tested on a unique articulated 400 million-year-old buchanosteid arthrodire (placoderm fish), ANU V244.

Reassembling and manipulating 3D printouts demonstrates the limits of jaw kenetics. Evidence indicates unrecognised similarities in jaw structure between arthrodires and osteichthyans and will help to clarify the sequence of character acquisition in the evolution of early jawed vertebrates. After this, taking a narrow-down scope, three types of toothplate were studied in basal arthrodires, giving insights into their morphology and the organisation of the associated dentition.

Evidence gives further insights into the primitive arthrodire condition for comparison with the dermal jaw bones of Chinese ‘maxillate’ placoderms that have been homologised with the premaxilla, maxilla, and dentary of osteichthyans. The new details will also help clarify the sequence of character acquisitions in the evolution of marginal jaw bones in early gnathostomes (jawed vertebrates). Scientific visualisation, including 3D segmentation, was done mainly through Drishti. An overview of the protocols for performing 3D segmentation and mesh generation using the latest Drishti version v2.7  will also be presented. 

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