Proceedings of the Royal Society B: Biological Sciences
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The earliest history of the deuterostomes: the importance of the Chengjiang Fossil-Lagerstätte

D.-G. Shu

D.-G. Shu

Early Life Institute & Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, People's Republic of China

School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, People's Republic of China

[email protected] [email protected]

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S. Conway Morris

S. Conway Morris

Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK

[email protected] [email protected]

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Z.-F. Zhang

Z.-F. Zhang

Early Life Institute & Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, People's Republic of China

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J. Han

J. Han

Early Life Institute & Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, People's Republic of China

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    While the broad framework of deuterostome evolution is now clear, the remarkable diversity of extant forms within this group has rendered the nature of the ancestral types problematic: what, for example, does the common ancestor of a sea urchin and lamprey actually look like? The answer to such questions can be addressed on the basis of remarkably well-preserved fossils from Cambrian Lagerstätten, not least the celebrated Chengjiang Lagerstätte (Yunnan, China). This deposit is particularly important because of its rich diversity of deuterostomes. These include some of the earliest known representatives, among which are the first vertebrates, as well as more enigmatic groups, notably the vetulicolians and yunnanozoans. The latter groups, in particular, have been the subject of some radical divergences in opinion as to their exact phylogenetic placements. Here, we both review the known diversity of Chengjiang deuterostomes and in particular argue that the vetulicolians and yunnanozoans represent very primitive deuterostomes. Moreover, in the latter case we present new data to indicate that the yunnanozoans are unlikely to be any sort of chordate.

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