Resolving the nature of our deuterostome ancestor by integrating Cambrian fossils into evolutionary trees based on genomic data

forthcoming

Deuterostomes are a major group of animals that include creatures as diverse as sea stars, acorn worms, and humans. Though seeming very different, these animals have long been grouped together taxonomically and the nature of their ancient ancestor has been greatly controversial. However, new research suggests that the deuterostome grouping might be false, leaving our understanding of their evolutionary relationships and evolutionary origins in complete disarray. I propose to resolve this controversy through joint analysis of genomic data and anatomical data from living animals and exceptionally preserved fossils from the Cambrian (520 million years old) that can directly inform on the nature of ancient deuterostomes. Realising the evolutionary significance of the fossils requires we resolve their phylogenetic affinity, which can only be achieved by elucidating their fine anatomy. My proposal focuses on three groups of Cambrian deuterostome fossils, myllokunmingids, yunnanozoans, and vetulicolians, from the Chengjiang UNESCO World Heritage fossil site, which I will integrate into a holistic synthetic family tree of deuterostomes to understand how their anatomical and physiological features evolved over time. For this, I will employ multiple state-of-the-art technologies to reveal the high-resolution histological information of the fossils, including spectrometry, electron microscopy, and computed tomography. The latest methods for phylogenetic analysis and ancestral state estimation will be used to construct the evolutionary tree and infer character evolution. Together, these work packages will allow me to resolve debates on the evolutionary relationships of deuterostomes and the evolution of their disparate bodyplans. The training will help me make the transition from a fossil-focusing palaeontologist, to an independent interdisciplinary palaeobiologist comfortable with the joint analysis of living and fossil species based on the anatomical and genomic data.