100
Journal of Paleontology 92(1):99–113
while forming a core source of data used to study paleobiogeo- graphic and macroevolutionary patterns during the Cambrian radiation interval (Hendricks et al., 2008). Non-hurdiid radiodontans reported from the Langston
Formation (Spence Shale Member), Wheeler Formation, and Marjum Formation are limited to two body fossils of Anomalocaris: one from the Spence Shale and one from the
Wheeler Formation, both described by Briggs et al. (2008, figs. 1, 3). Neither specimen has well-preserved large frontal appendages, and the two specimens seem to represent two dif- ferent and new species. Isolated appendages of Anomalocaris aff. A. canadensis Whiteaves, 1892 and Anomalocaris? sp. from the younger (Guzhangian) Weeks Formation in Utah have been described by Lerosey-Aubril et al. (2014). No new Anomalocaris appendages or bodies were identified during the course of this study.Weemphasize newfindings relating toHurdia andPeytoia. As is the case for other radiodontans, Hurdia and Peytoia
are found mostly as isolated elements (carapace elements, mouthparts, appendages, and body flaps) and rarely as whole bodies, which can at times make taxonomic identification challenging. In general, the morphology of Hurdia can be described as follows. The head region comprises a pair of frontal appendages either side of a circular oral cone. The oral cone is made up of four large plates, equally spaced, with seven small plates between each pair of large plates; these surround an opening with multiple inner rows of teeth. A large frontal carapace of three sclerotized elements (two lateral P-elements and one dorsal H-element) and stalked eyes complete the head region. The body is made up of seven to nine segments, with reduced swimming flaps and prominent setal structures (Daley et al., 2009, 2013a). A morphometric analysis showed that there are two species of Hurdia, H. victoria and H. triangulata Walcott, 1912, which are differentiated by comparing the length and width of the carapace H-element (Daley et al., 2013a). Hurdia and Peytoia have recently been recovered within Hurdiidae (e.g., Van Roy et al., 2015), but these genera differ in a number of ways. Peytoia and Hurdia have a similar overall frontal appendage morphology in that both have elongated ventral spines, but these differ in numerous details, including the number and length-width ratio of the podomeres and the shape, arrangement, and number of ventral spines (Daley et al., 2013a). Hurdia has a complex frontal carapace composed of three sclerite elements, whereas Peytoia has no evidence for such a large frontal carapace, with only traces of possible carapace material immediately surrounding the head in ventrally pre- served specimens (Daley et al., 2009). The oral cone has the same arrangement of outer plates in Hurdia and Peytoia, but the multiple inner rows of teeth present in Hurdia are absent in Peytoia. The body trunk in Hurdia consists of seven to nine segments that are more cylindrical than the dorsoventrally flat- tened body of Peytoia, which has 13 body segments. The swimming flaps of Hurdia are much smaller than the wide flaps of Peytoia, but setal blades are more prominent in Hurdia as compared to Peytoia (Whittington and Briggs, 1985, fig. 101).
Materials and methods
One body specimen (USNM 374593) is held at the Smithsonian Museum of Natural History, Washington, D.C., USA. The
remainder of the material studied is held at the Division of Invertebrate Paleontology, Biodiversity Institute, University of Kansas, Lawrence, USA (KUMIP). Detailed information for the fossil localities is available in Hendricks et al. (2008, table 3). All specimen numbers, previous publications, and new identifications are provided in Table 1. Photographs were taken with a Canon EOS 500D DSLR
Camera with Canon EF-S 60mm Macro Lens, controlled for remote shooting using the EOS Utility 2 program. Photographs were taken under cross-polarized light, under nonpolarized light, wet and dry, and under high- and low-angle lighting. Measurements for calculating RI values, and length:width ratios were taken from digital photographs using ImageJ
2.The 3D model was made using Blender 2.76b. Abox model was created from a sketch of Hurdia adapted from Daley and Budd (2010). This was modified with a subdivision surface and rendered to a video. A phylogenetic analysis in TNT v. 1.5 (Goloboff and Catalano, 2016) was run using implicit enumeration under equal weighting on a data matrix modified from Van Roy et al. (2015) consisting of 33 taxa and 61 characters. Modifications to the phylogenetic analysis data matrix were made in Mesquite v. 3.2 (Maddison and Maddison, 2017).
Geologic setting
The Spence Shale Member of the Langston Formation, middle Cambrian Series 3, Stage 5, is a diverse soft-bodied biota (Gunther and Gunther, 1981; Robison, 1991; Liddell et al., 1997), and knowledge of the paleontology, sedimentology, geochemistry, and taphonomy of this deposit has increased substantially over the past few years (Briggs et al., 2008; Gaines et al., 2012; Garson et al., 2012; Olcott Marshall et al., 2012; Gaines, 2014; Kloss et al., 2015). The Spence Shale is primarily made up of shale, with some limestone, and it is developed in a series of parasequences (Liddell et al., 1997; Garson et al., 2012). Detailed discussions of the sedimentology, taphonomy, and geochemistry of the Spence Shale are provided by Liddell et al. (1997), Garson et al. (2012), and Kloss et al. (2015), respectively. All the specimens from the Spence Shale discussed herein come from the Wellsville Mountains of northern Utah (Hendricks et al., 2008; Hendricks, 2013). The Wheeler Formation, Drumian, Cambrian Series 3,
from the House Range of Utah is slightly younger than the Spence from the Wellsvile Mountains, and it too contains a diverse soft-bodied biota (Robison, 1964, 1991; Gunther and Gunther, 1981; Briggs and Robison, 1984; Rogers, 1984; Rees, 1986; Robison et al., 2015). There have been a substantial number of relatively recent sedimentological, taphonomic, and geochemical studies of the soft-bodied biota from this formation and region (e.g., Gaines and Droser, 2003, 2005; Briggs et al., 2008; Brett et al., 2009; Halgedahl et al., 2009; Gaines, 2014). The unit consists of homogeneous mudstones and interbedded mudstones with thin-grained, fine-bedded limestones. The soft- bodied material occurs primarily within carbonaceous shales (Gaines and Droser, 2003, 2005). The still slightly younger soft-bodied deposits from the
Marjum Formation, Drumian, Cambrian Series 3, generally resemble lithologically, stratigraphically, and taphonomically those deposits from the Wheeler Formation where it is exposed
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