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Hyoliths are Palaeozoic lophophorates.

Moysiuk, J. and Smith, M.R. and Caron, J.-B. (2017) 'Hyoliths are Palaeozoic lophophorates.', Nature., 541 . pp. 394-397.

Abstract

Hyoliths are abundant and globally distributed ‘shelly’ fossils that appear early in the Cambrian period and can be found throughout the 280 million year span of Palaeozoic strata1, 2. The ecological and evolutionary importance of this group has remained unresolved, largely because of their poorly constrained soft anatomy and idiosyncratic scleritome, which comprises an operculum, a conical shell and, in some taxa, a pair of lateral spines (helens)3, 4, 5. Since their first description over 175 years ago, hyoliths have most often been regarded as incertae sedis4, 6, related to molluscs7, 8 or assigned to their own phylum1, 2. Here we examine over 1,500 specimens of the mid-Cambrian hyolith Haplophrentis from the Burgess Shale and Spence Shale Lagerstätten. We reconstruct Haplophrentis as a semi-sessile, epibenthic suspension feeder that could use its helens to elevate its tubular body above the sea floor3, 9, 10, 11, 12. Exceptionally preserved soft tissues include an extendable, gullwing-shaped, tentacle-bearing organ surrounding a central mouth, which we interpret as a lophophore, and a U-shaped digestive tract ending in a dorsolateral anus. Together with opposing bilateral sclerites and a deep ventral visceral cavity, these features indicate an affinity with the lophophorates (brachiopods, phoronids and tommotiids), substantially increasing the morphological disparity of this prominent group.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1038/nature20804
Date accepted:25 October 2016
Date deposited:04 November 2016
Date of first online publication:11 January 2017
Date first made open access:11 July 2017

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