An early Cambrian agglutinated tubular lophophorate with brachiopod characters.
The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen. et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagerstätte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long pedicle with coelomic space. The terminal bulb of the pedicle provided anchorage in soft sediment. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.
1] Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China [2] LPS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
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ZF
Zhang
LPS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
G-X
GX
Li
Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, SE-752 36 Uppsala, Sweden.
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LE
Holmer
Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia.
G A
GA
Brock
University of Glasgow, Department of Geographical and Earth Sciences, Gregory Building, Lilybank Gardens, G12 8QQ, Glasgow, United Kingdom.
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U
Balthasar
Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
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Skovsted
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
D-J
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Fu
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
X-L
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Zhang
Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, SE-752 36 Uppsala, Sweden.
H-Z
HZ
Wang
Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, SE-752 36 Uppsala, Sweden.
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Butler
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
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ZL
Zhang
LPS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
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CQ
Cao
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
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Han
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
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JN
Liu
Early Life Institute, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an, 710069, China.
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Shu
D000818:Animals; D005075:Biological Evolution; D002681:China; D005580:Fossils; D007448:Invertebrates / Q000033:anatomy & histology* / Q000502:physiology*; D010802:Phylogeny