X-ray tomography reveals how Chinese jawless fish evolved

Most living vertebrates are jawed vertebrates (gnathostomes), and only scarce information on the evolutionary origin of jaws is available from living jawless vertebrates (cyclostomes), hagfishes and lampreys. The extinct bony jawless vertebrates, or 'ostracoderms', have been regarded as precursors of jawed vertebrates and provide an insight into this formative episode in vertebrate evolution. Very recently, Chinese scientists employed synchrotron radiation X-ray tomography in an effort to analyze the cranial anatomy of galeaspids, a 370-435-million-year-old 'ostracoderm' group from China and Vietnam. For more information, see the paper, "Fossil jawless fish from China foreshadows early jawed vertebrate anatomy", Z. Gai et al., Nature 476, 324 (2011).