Nature 345, 802 - 805 (28 June 1990); doi:10.1038/345802a0

Articulated halkieriids from the Lower Cambrian of north Greenland

S. Conway Morris^* & J. S. Peel^†

^*Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
^†Geological Survey of Greenland, Joster Voldgade 10, Copenhagen K, DK-1350, Denmark

METAZOAN skeletons appear abruptly in the fossil record near the base of the Cambrian (540MyrBP (before present))^1,2. In the initial stages of diversification, familiar skeletal remains such as sponge spicules, brachiopod valves and echinoderm ossicles are outnumbered by a remarkable array of skeletal types, many of millimetric size^3–9. Particularly conspicuous in these early assemblages are various sclerites, some of which are inferred to have formed cataphract coverings of slug-like metazoans. Recognition of articula tory facets and fused sclerites contribute to partial scieritome reconstructions^8–11, but discovery of articulated material is a vital ingredient in understanding the palaeobiology of these extinct groups. Here we report complete halkieriid scleritomes from the Lower Cambrian of north Greenland. This finding broadly confirms the predictions of an earlier hypothetical reconstruction¹¹, but reveals entirely unexpected anterior and posterior shells. It supports also the proposed phylogenetic link between the halkieriids and Wiwoxia corrugata, a metazoan with a cataphract scieritome best known from the Middle Cambrian Burgess Shale.

References

1.	Conway Morris, S. Am. Scientist. 75, 156−167 (1987).
2.	Conway Morris, S. Sci. Prog., Oxf. 73, 81−99 (1989).
3.	Qian Yi & Bengtson, S. Fossils and Strata 24, 1−156 (1989).
4.	Missarzhevsky, V. V. Oldest Skeletal Fossils and Stratigraphy of Precambrian and Cambrian Boundary Beds. Akad. Nauk. SSSR Trudy 443, 1−238 (Nauka, Moscow, 1989).
5.	Landing, E., Myrow, P., Benus, A. P. & Narbonne, G. M. J. Paleont. 63, 739−769 (1989).
6.	Conway Morris, S. & Chen Menge Geol. Mag. 126, 615−632 (1989).
7.	Conway Morris, S. & Chen Menge J. Paleont. 64, 169−184 (1990).
8.	Conway Morris, S. & Chen Menge Palaeontology (in the press).
9.	Bengtson, S., Conway Morris, S., Cooper, B., Jell, P. A. & Runnegar, B. Mems. Ass. Áustralas. Palaeontols. 9 (in the press).
10.	Landing, E. J. Paleont. 58, 1380−1398 (1984).
11.	Bengtson, S. & Conway Morris, S. Lethaia 17, 307−329 (1984).
12.	Peel, J. S. Can. Soc. Petrol. geol. Mem. 8, 309−330 (1982).
13.	Conway Morris, S., Peel, J. S., Higgins, A. K., Soper, N. J. & Davis, N. C. Nature 326, 181−183 (1987). | Article |
14.	Conway Morris, S. Trans. R. Soc. Edinb. 80, 271−283 (1989).
15.	Conway Morris, S. & Robison, R. A. Paleont. Cont. Univ. Kans. Pap. 117, 1−22 (1986).
16.	Kraft, P. & Mergl, M. Sb. ustred. Ust. geol. paleont. 30, 9−36 (1989).
17.	Bengtson, S. & Missarzhevsky, V. V. U.S. geol. Surv. Open-File Rep. 81−743, 19−21 (1981).
18.	Conway Morris, S. Phil. Trans. R. Soc. B307, 507−586 (1985).
19.	Dzik, J. in Problematic Fossil Taxa (eds Hoffman, A. & Nitecki, M. H.) 116−134 (Oxford University Press, New York, 1986).
20.	Bergström, J. Lethaia 22, 259−269 (1989).
21.	Bengtson, S. Lethaia 3, 363−392 (1970).
22.	Jell, P. A. Alcheringa 3, 253−259 (1979).
23.	Bengtson, S. Thalassia Jugoslavica 12, 1−10 (1978).
24.	Chen Junyuan, Hou Xianguang & Lu Haozhi, Acta palaeont. sin. 28, 1−16 (1989).
25.	Ahlberg, P. E. Nature 344, 23 (1990).