Kimmig et al.—Siphusauctum lloydguntheri n. sp. from the Spence Shale
presence or absence of comb segments in S. lloydguntheri n. sp. is a vital step towards resolving the taxonomic affinities of the genus and determining if Siphusauctum is a stem-group entoproct.
Conclusions
Although S. lloydguntheri n. sp. is very rare, its counterpart S. gregarium has been extremely well characterized, such that it is possible to distinguish the former as lying outside the degree of biological or taphonomical variation shown in the latter. In particular, the different calyx shape, placement of the digestive tract, and the interior calyx structure suggest that separating these two species is warranted. The occurrence of Siphusauctum in the Spence Shale extends its geographic range into the Great Basin, and slightly expands the temporal range for this enig- matic group of early Paleozoic stalked filter feeders. Certain characteristics of S. lloydguntheri n. sp. might suggest a rela- tionship with other Cambrian taxa, such as Dinomischus and Cotyledion, and possibly with modern entoprocts.
Acknowledgments
We thank L. Gunther for collecting and donating the studied material, and we thank J.-B. Caron for discussions regarding it. Two anonymous reviewers, associate editor N. Butterfield, and editor B. Hunda are thanked for their comments on a previous version of the manuscript.
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