Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba lagerstätte.
Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp. nov. from the Xiaoshiba fauna (Cambrian Stage 3, Hongjingshao Formation, Kunming, south China). Although spines are absent, the fossils' sclerites - like those of W. corrugata - are symmetrically arranged in five distinct zones. They form rows across the body, and were individually added and shed throughout growth to retain an approximately symmetrical body shape. Their development pattern suggests a molluscan affinity. The basic body plan of wiwaxiids is fundamentally conserved across two continents through Cambrian Stages 3-5 - revealing morphological stasis in the wake of the Cambrian explosion.
Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
Jie
J
Yang
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
Martin R
MR
Smith
Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
Tian
T
Lan
Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
Jin-bo
JB
Hou
Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
Xi-guang
XG
Zhang
D000818:Animals; D005075:Biological Evolution; D002681:China; D005580:Fossils; D008974:Mollusca / Q000033:anatomy & histology* / Q000145:classification*; D010163:Paleontology; D010802:Phylogeny; D011077:Polychaeta / Q000033:anatomy & histology* / Q000145:classification*