Journal of Paleontology, 92(1), 2018, p. 99–113 Copyright © 2017, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.11


Hurdiid radiodontans from the middle Cambrian (Series 3) of Utah


Stephen Pates,1 Allison C. Daley,1,2,3 and Bruce S. Lieberman4,5 1Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK ⟨stephen.pates@zoo.ox.ac.uk⟩ 2Oxford University Museum of Natural History, Oxford, OX1 3PW, UK 3Faculty of Geosciences and Environment, University of Lausanne, Sorge Géopolis, CH1015, Lausanne, Switzerland ⟨allison.daley@unil.ch⟩ 4Division of Invertebrate Paleontology, Biodiversity Institute, University of Kansas, Lawrence, Kansas 66045, USA ⟨blieber@ku.edu⟩ 5Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA


Abstract.—Radiodontan body elements, some belonging to Peytoia and Hurdia and some unassigned, have been reported from the Langston Formation (Spence Shale Member), Wheeler Formation, and Marjum Formation of the middle Cambrian (Series 3) of Utah. These identifications are reassessed in light of recent work on the morphology of the radiodontan Hurdia. New specimens of Hurdia are identified from the Spence Shale, representing mouthparts (oral cones), cephalic carapace H-elements, frontal appendages, and a single isolated swimming flap. The shape of the H-elements allows H. victoria Walcott, 1912 to be identified from the Spence Shale for the first time. The flap is larger and more complete than any reported from the Burgess Shale and allows for a better understanding of the morphology of Hurdia swimming flaps. A 3D model of a Hurdia frontal appendage indicates that there is only one morph of Hurdia frontal appendage found in both species, and apparent morphological differences between disarticulated appendages reflect a preservational continuum caused by varying oblique angles relative to the seafloor. Peytoia should no longer be reported from the Spence Shale, but its presence is confirmed in the Wheeler and Marjum formations. New mouthparts (oral cones) of Hurdia from the Spence Shale and Peytoia from the Marjum Formation with surface textures of submillimeter-diameter raised nodes are described. These new features have not been observed in material from the Burgess Shale and suggest slight differences in preservation.


Introduction


Our understanding of the morphology and systematics of HurdiaWalcott, 1912 has greatly expanded in recent years, and it is now recognized as a significant taxon within Radiodonta present in several of thewell-knownCambrian soft-bodied biotas including the Burgess Shale in Canada and the nearby Stanley Glacier, Marble Canyon, Tulip Beds, and Mount Stephen sites (Daley et al., 2009, 2013a); the Jince Formation in the Czech Republic (Chlupáč and Kordule, 2002, fig. 7); Wheeler Forma- tion (Robison andRichards, 1981, pl. 4, fig. 1a, b) and the Spence Shale (Daley et al., 2013a) in Utah, USA; the Shuinjingtuo For- mation in China (Cui and Huo, 1990); and the Fezouata Biota in Morocco (Van Roy and Briggs, 2011, figs. 1d–i, S4a–c, 1l, S3c, d, S4f). Notably, the soft-bodied biotas from the middle Cambrian (Series 3) of Utah have yielded a large number of specimens previously identified as radiodontans in general, and usually AnomalocarisWhiteaves, 1892 or PeytoiaWalcott, 1911 (Daley and Bergström, 2012) (e.g., ConwayMorris and Robison, 1982, 1988; Briggs and Robison, 1984; Robison, 1991; Briggs et al., 2008), but the systematic position of most of this material has not yet been reevaluated in light of the new discoveries on Hurdia. By analysis of appendages and mouthparts originally described by Conway Morris and Robison (1988), Daley et al. (2013a) were able to conclude that Hurdia was in fact present in the middle Cambrian (Series 3) of Utah alongside Peytoia,and


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they described four new specimens from the Spence Shale. Herein, we reconsider the identifications of radiodontan specimens from Utah in detail and confirm that Hurdia is well represented there. Further, we identify H. victoria Walcott, 1912 in the Spence Shale for the first time. A3Dmodel of an idealized Hurdia appendage potentially allows characters used in previous phylogenetic analyses (e.g., Cong et al., 2014; Vinther et al., 2014; Van Roy et al., 2015) to be visualized and evaluated in the hopes of possibly inferring which charactersmight be influenced by taphonomic factors. The middle Cambrian (Series 3) of Utah is well known for


its soft-bodied deposits that preserve a diverse array of taxa in several different depositional settings (Robison, 1991; Briggs et al., 2008; Gaines et al., 2008, 2012; Brett et al., 2009; Halgedahl et al., 2009). The Gunther family of Utah, along with Richard Robison (Robison, 1965; Gunther and Gunther, 1981), played a pivotal role in helping this treasure trove of fossils come to light. Many significant finds have been made from these deposits over the years (Resser, 1939; Brooks and Caster, 1956; Briggs and Robison, 1984; Babcock and Robison, 1988; Conway Morris and Robison, 1986, 1988; Robison and Wiley, 1995; Briggs et al., 2005), and new discoveries continue to be made (Robison and Babcock, 2011; Stein et al., 2011; Conway Morris et al., 2015; LoDuca et al., 2015; Robison et al., 2015). Taxa from these deposits have also provided insights into higher- level arthropod relationships (Hendricks and Lieberman, 2008)


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