Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians

Caron, Jean-Bernard and Smith, Martin R. and Harvey, Thomas H. P. (2013) Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians. Proceedings of the Royal Society B: Biological Sciences, 280 (1767).

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Official URL: http://rspb.royalsocietypublishing.org/content/280...

Abstract

Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian �explosion�. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution�but are difficult to interpret in the absence of corresponding whole-body fossils. Here, we provide new observations on the dorsal spines of the Cambrian lobopodian (panarthropod) worm Hallucigenia sparsa from the Burgess Shale (Cambrian Series 3, Stage 5). These exhibit a distinctive scaly microstructure and layered (cone-in-cone) construction that together identify a hitherto enigmatic suite of carbonaceous and phosphatic Cambrian microfossils�including material attributed to Mongolitubulus, Rushtonites and Rhombocorniculum�as spines of Hallucigenia-type lobopodians. Hallucigeniids are thus revealed as an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the �middle� Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. The cone-in-cone construction of hallucigeniid sclerites is shared with the sclerotized cuticular structures (jaws and claws) in modern onychophorans. More generally, our results emphasize the reciprocal importance and complementary roles of Burgess Shale-type fossils and isolated microfossils in documenting early animal evolution.

Item Type: Article
Additional Information: PMID: 23902914
Uncontrolled Keywords: Biostratigraphy, Cambrian evolutionary radiation, lagerstätten, small carbonaceous fossils, small shelly fossils
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Proceedings of the Royal Society B: Biological Sciences
Volume: 280
Depositing User: Sarah Humbert
Date Deposited: 31 Aug 2013 12:20
Last Modified: 31 Aug 2013 12:20
URI: http://eprints.esc.cam.ac.uk/id/eprint/2864

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