Evolutionary assembly of the gnathostome bodyplan: insights from extinct jawless vertebrates

Almost all vertebrates, including ourselves, are jawed vertebrates, but the formative stages in our evolutionary ancestry can be traced to an array of extinct jawless vertebrates (also known as ostracoderms) that lived almost half a billion years ago and record the gradual assembly of the bodyplan that all living jawed vertebrates inherited. While some of the groups of fossil ostracoderms have been well-studied, the biology of the extinct jawless galeaspids lags behind because they have been discovered comparatively recently. Nevertheless, they appear to be close relatives of the jawed vertebrates and, as such, they are key to establishing the nature of the ancestral jawless vertebrate from which jawed vertebrates are descended. We propose to remedy this through SRXTM analysis of exceptionally preserved fossil galeaspids from the Devonian of Yunnan, China, focussing on the nature of the brain, sensory organs and skeleton, sampling from across the breadth of galeaspid diversity.