2025-W9 Cambrian ‘weird wonders’ and the evolution of the early craniate head

Overview

One of the hardest problems in the field of understanding Systems Evolution is the origin of the vertebrate head and its complex morphology. Traditional textbook knowledge assumes head shape to be primarily driven by an embryonic population called the neural crest, the area of particular expertise of Prof Koentges and a vertebrate novelty. Surprisingly, recent work by Dr Dunn (NERC fellow at OUMNH) has shown that complex cranial features – long assumed to be the result of diversifying neural crest cells – were present in the ancestors of all chordates, long before neural crest as a tissue even evolved. These fossils, vetulicolians, show remarkable similarity to craniate larvae, suggesting that a major pedomorphic event is at the heart of the evolution of the vertebrate body plan. The aim of this project is to combine state-of-the-art imaging of embryonic tissues forming key head structures in vertebrates with the palaeobiology of early chordates to understand this event. Such combination will enable us to elucidate the developmental process behind the emergence of anatomical novelties in fossil species (e.g. the formation of head shields) for the first time and map developmental characters into phylogenetic datasets of chordate fossils;  Vetulicolians were very large (and hence slow growing animals), while the smaller descendant chordates develop very fast and are much smaller. The speed of individual character ontogenies is therefore phylogenetically informative, but has so far not been used to build evolutionary trees. The student will establish cellular and molecular ‘ground plans’ for these early fossil chordates, which lived and died more than half a billion years ago, at an unpredecented level of precision.  This project bears the promise to take best advantage of both worlds, state-of-the-art paleontology and cladistics with state-of-the-art vertebrate developmental biology in order to study the emergence of a ecologically revolutionary body plan.