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A New Species of Yunnanozoan with Implications for Deuterostome Evolution
Degan Shu,1*Simon Conway Morris,2Z. F. Zhang,1J. N. Liu,1Jian Han,1Ling Chen,1X. L. Zhang,1K. Yasui,3Yong Li4
Yunnanozoans are a distinctive clade of Lower Cambrian
metazoans. Although widely accepted as deuterostomes, their exact
placementwithin this superphylum is controversial. Here we describe a
newspecies of Haikouella (H. jianshanensis) from
the Chengjiang Lagerstätte(Yunnan, China) with exceptional
preservation of a number of features.These include external gills,
which suggest that the origin ofthe pharyngeal clefts was independent
of the gills. The diagnosticbranchial arches of chordates may,
therefore, be composite structures.No evidence was found for the
chordate-like structures that havebeen described in other
yunnanozoans. We propose that yunnanozoansare stem-group
deuterostomes, allied to the vetulicolians.
1 Early Life Institute and Department of
Geology, Northwest University, Xi'an 710069, China, and School of
Earth Sciences and Resources, China University of Geosciences, Beijing
100083, China.
2 Department of Earth Sciences,
University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
3 Institute of Molecular Embryology and Genetics,
Division of Development and Biohistory, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
4 College of Earth
Science and Land Resources, Chang'an University, Xi'an 710054, China.
*
To whom correspondence should be addressed. E-mail:
elidgshu{at}nwu.edu.cn and dgshu{at}sein.sxgb.com.cn
