Tackling taxonomic and taphonomic biases in the Triassic fossil fish record

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Ray-finned fishes (actinopterygians) are the most diverse and successful group of vertebrates today, accounting for over half of living vertebrate species. In their nearly half-a-billion-year history they have survived countless mass extinctions, but, in contrast to many other groups, there is limited understanding of the effect of these devastating mass extinction events on their evolution. Despite thousands of exceptionally preserved two- and three-dimensional fossils from early Triassic deposits worldwide, there is a particularly poor understanding of how the Permo-Triassic Mass Extinction (252 million years ago) impacted ray-finned fishes. The reasons for this are two-fold: no robust hypothesis of the taxonomy and relationships of early Triassic ray-fins, and limited comprehension of the taphonomic processes that may have biased the Early Triassic fossil fish record. This project will combine CT scanning, phylogenetic analyses and taphonomic investigations to tackle these biases. Recent work has established a backbone of relationships amongst early actinopterygians, and the student will use a combination of traditional descriptive methods and CT scanning to place key early Triassic taxa into this phylogenetic framework and answer taxonomic questions. Much of our understanding of fish taphonomy and decay is based on teleost fishes, which display a very different morphology from early actinopterygians, in particular with regard to scale histology. Different types of squamation may have a profound impact on the preservation potential of different fish groups, potentially biasing the fossil record in this key period of earth's history and skewing our understanding of ray-finned fish recovery after the Permo-Triassic mass extinction. The student will investigate the effects of this through targeted interrogation of scale-bearing and scaleless taxa as well as taphonomic investigation of extant scale-bearing actinopterygians. This research will provide new insights into taphonomic processes acting on ray-finned fishes and the varying preservation potential of different fossil fish groups. It will also contribute to a revised hypothesis of actinopterygian relationships, answering fundamental questions concerning the impact of the Permo-Triassic mass extinction on the evolution of the largest living vertebrate clade.