Final Report Summary - JAWEVOL (The Origin of Jawed Vertebrates and the Evolution of Morphology in Deep Time)
Jawed vertebrates represent the vast majority of living vertebrate diversity—including humans. They possess not only jaws and teeth, but paired appendages and diverse skeletal tissues, which no doubt have all contributed to the enormous evolutionary success of this group. They originated more than 420 million years ago, during the Palaeozoic Era. However our understanding of their evolutionary origins has been hampered by a poor understanding of their fossil record. Although many fossils of early jawed vertebrates exist, their interpretation is often contentious and there exists no clear picture of the group’s early evolution. The purpose of this project was to enhance this understanding by using state-of-the-art techniques to understand fossils and develop new techniques to understand how fossils are related to each other. During the course of this work, we used x-ray computed tomography scanning to generate three-dimensional digital ‘dissections’ of the skulls of early jawed fishes. By creating these detailed anatomical accounts we were able to piece together clues about the origins of modern jawed vertebrates. In particular, this work helped overturn a long-standing view that the ancestors of jawed vertebrates were shark-like fishes that lived high up in the water column. We’ve been able to show that much of what we think is “primitive” in sharks are actually specialisations unique to their branch in the family tree. The ancestors of modern jawed vertebrates likely looked more like bony fishes, having a heavy skeletal armour on their heads. To add to our understanding of fossil diversity, we undertook fieldwork in western Mongolia and uncovered fossils that provided similar challenges to our understanding—particularly about the evolutionary history of bone. Overall, the work provided a modernized view of the evolution of jawed vertebrates as well as raising new questions for future research.