A columnal-bearing eocrinoid from the Cambrian Burgess Shale ...

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Abstract.—A new eocrinoid ?Ubaghsicystis sp. from the middle Cambrian (Series 3, Stage 5) Burgess Shale is reported based on a single known specimen.
Journal of Paleontology, page 1 of 3 Copyright © 2015, The Paleontological Society 0022-3360/15/0088-0906 doi: 10.1017/jpa.2014.54

A columnal-bearing eocrinoid from the Cambrian Burgess Shale (British Columbia, Canada) Colin D. Sumrall1 and Samuel Zamora2,3 Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA, 〈[email protected]〉 Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington DC, 20013–7012, USA 3 Current address: Instituto Geológico y Minero de España, Manuel Lasala 44, E-50006 Zaragoza, Spain, 〈[email protected]〉 1 2

Abstract.—A new eocrinoid ?Ubaghsicystis sp. from the middle Cambrian (Series 3, Stage 5) Burgess Shale is reported based on a single known specimen. This species extends the stratigraphic range of columnal-bearing eocrinoids in Laurentia significantly from Cambrian Stage 7 (Guzhangian) to Stage 5. It increases the diversity of echinoderms in this well-known fossil-Lagerstätte, provides the oldest evidence of columnal-bearing eocrinoids from Laurentia, and further documents the cosmopolitan distribution of middle Cambrian echinoderm clades.

Introduction

Cambrian Series 3 Stage 5 from several Gondwanan localities (Zamora et al., 2010; Smith et al., 2013). This shows that the lack of early occurrences of holomeric stemmed echinoderms in Laurentia was a sampling artifact, and that by the middle Cambrian, such stems were present in both northern and southern continents. The possible presence of Ubaghsicystis in the Burgess Shale provides further evidence for a cosmopolitan distribution of many echinoderm clades during the middle Cambrian. When Burgess Shale echinoderms are compared to nearly coeval deposits, it is noted that gogiids occur in Spain, France, Morocco, and China; Lyracystis occurs in China; Ubaghsicystis occurs in Morocco and Spain; Ctenocystis occurs in France and Australia; and Walcottidiscus (= Kailidiscus) occurs in China (Jell et al., 1985; Ubaghs, 1987; Parsley and Zhao, 2006; Zamora, 2010; Sprinkle et al., 2011; Smith et al., 2013; Zamora et al., 2013). Compared with other North American localities, only two echinoderm clades (Soluta and Stylophora) are missing from the Burgess Shale (Ubaghs and Robison, 1985, 1988; Sumrall and Sprinkle, 1999). Further research on Burgess Shale faunas may yet discover specimens of these clades as shown by the fortuitous discovery of ?Ubaghsicystis sp.

The Burgess Shale of British Columbia, Canada, is the most famous Cambrian fossil locality in North America, and is often used to address questions about the timing and nature of the Cambrian Explosion and origin of animal phyla (Briggs et al., 1994). Although excavations since the time of Walcott have uncovered an extraordinary diversity of animals (Collins, 2009a), echinoderms remain scarce in collections and low in diversity when compared with similar-aged strata from Gondwana (Zamora, 2010; Smith et al., 2013). Currently, only three unambiguous Burgess Shale echinoderms have been formally described. These include the plesiomorphic edrioasteroid Walcottidiscus typicalis Bassler, 1935 (Smith, 1985; Zhao et al., 2010), and the two eocrinoids Gogia stephenensis Sprinkle and Collins, 2006, and Lyracystis radiata Sprinkle, 1973 (Sprinkle and Collins, 2006). There are also poorly preserved ctenocystoids assignable to Ctenocystis that await formal description (Collins, 2009b). Other taxa have been considered by some to be echinoderms, including Echmatocrinus Sprinkle, 1973 (Sprinkle and Collins, 1998), and presumed holothuroids, including Eldonia ludwigi Walcott, 1911, Laggania cambria Walcott, 1911, Louisella pedunchlata Walcott, 1911, Mackenzia costalis Walcott, 1911, Redoubtia polypodia Walcott, 1911, and Portalia mira Walcott, 1911 (Walcott, 1918). Later authors have cast doubt on the echinoderm affinities of these fossils (Clarke, 1913; Madsen, 1957; Müller, 1963; Ausich and Babcock, 1998, 2007; Daley et al., 2009). The new eocrinoid from the Burgess Shale, while left under open nomenclature, has global implications for the timing of the origin of holomeric stems in eocrinoids. Prior to this discovery, the oldest Laurentian echinoderm bearing a holomeric stem was Eustipocystis minor Sprinkle, 1973, known from the middle Cambrian Guzhanguian. However, Gondwanan holomeric columnals predate those from Laurentia and are known from

Systematic paleontology

Subphylum Blastozoa Sprinkle, 1973 Class Eocrinoidea Jaekel, 1918 Family uncertain Genus Ubaghsicystis Gil Cid and Domínguez Alonso, 2002

Type species.—Ubaghsicystis segurae Gil Cid and Domínguez Alonso, 2002 from the Cambrian of northern Spain. 1

Journal of Paleontology

2

Remarks.—The new eocrinoid specimen from Burgess Shale is tentatively assigned to Ubaghsicystis based on the presence of a globular, polyplated theca bearing two feeding appendages and a slender, columnal-bearing stem. Although this taxon has a somewhat different size and distribution of thecal plates as compared to U. segurae, poor preservation precludes the description of a new species. Until now, Ubaghsicystis was only known from middle Cambrian deposits of Perigondwanan Spain and Morocco. The Spanish specimens were collected in the Cantabrian Mountains from the lower Languedocian section of the Oville Formation at the Barrios de Luna locality (León, North Spain). Specimens from Morocco are slightly older, and come from the Agzian Jbel Wawrmast Formation in its type locality (Gil Cid and Domínguez Alonso, 2002; Smith et al., 2013). The Agzian regional stage corresponds approximately with Cambrian Series 3, Stage 5, but the correlation of the Languedocian with global stages proposed by the International Subcommission on Cambrian Stratigraphy is problematic. Based on chemostratigraphic evidence, the lower Languedocian corresponds to Series 3 Stage 5 (see Álvaro et al., 2008). However, correlation based on trilobites and agnostids suggests it is correlative with the base of the Drumian (see Gozalo et al., 2011).

plates per exposed surface (Figs. 1, 2); specimen too poorly preserved to reveal exact disposition of plates or details of ornamentation, but plates appear slightly ridged and convex, some plates suggest small circular epispires along plate margins; two feedings appendages (brachioles) arise from oral spout (Figs. 1.1, 2); brachioles slender with massive, biserial brachiolar plates and very thin and small cover plates; connection with stem abrupt; on one side, two large plates at thecal base connect with the stem as in Ubaghsicystis segurae, no evidence seen for the position and plating of the periproct; stem relatively thin and gracile, holomeric with very short columnals (Figs. 1.2, 2), length unknown, but at least 10 mm visible; stem slightly wider close to theca and somewhat tapered, proximal width 0.8 mm, distalmost preserved diameter 0.3 mm. proximally with 6 columnals per mm.

?Ubaghsicystis sp. Figure 1.1–1.3 Occurrence.—Bathyuriscus–Elrathina Zone, Cambrian Series 3, Stage 5. The specimen was collected in situ from a level 250 cm below the Phyllopod Bed in the Walcott Quarry, Mount Field, British Columbia. Description.—Theca of single known specimen globular, 7 mm in diameter, composed of polygonal plates, with at least 16–20

Figure 1. ?Ubaghsicystis sp. showing a polyplated and globular theca, two brachioles, and a long stem constructed with low columnals. (1, 3) Part ROM 62443b and counterpart ROM 62443a immersed underwater with crossed polarized light, ×4.25; (2) Detail of proximal stem of ROM 62443a showing columnar construction, ×10.

Figure 2. Camera lucida drawing of Ubaghsicystis sp. ROM 62443a, showing two brachioles (b) arising from the thecal summit, a polyplated theca (t), and a gracile holomeric stem (s). The specimen is preserved overlapping an arthropod fragment (a), ×6.

Sumrall and Zamora—Burgess Shale eocrinoid

Remarks.—?Ubaghsicystis sp. differs from U. segurae by possessing a slightly less tumid theca and a more gracile stem. The poor preservation of the Burgess Shale specimen precludes formal description until better-preserved material is discovered. The presence of ?Ubaghsicystis sp. in Laurentia is important because it provides new data on the timing of holomeric columnals in Laurentian eocrinoids. While this feature appears by the Cambrian Series 3 Stage 5 in several Gondwanan localities (Zamora et al., 2010, Smith et al., 2013), the oldest previously reported Laurentian eocrinoid with holomeric columnals in the stem is the Guzhanguian Eustipocystis minor Sprinkle, 1973, thus extending the range of Laurentian holomeric columnals by 10 Myr. ?Ubaghsicystis sp. also adds another suspension-feeding echinoderm to the Burgess Shale assemblage. Material.—Part and counterpart (ROM 62443a, b), housed at the Royal Ontario Museum, Toronto, Ontario.

Acknowledgments We acknowledge the support of the Royal Ontario Museum curatorial staff, especially J.-B. Caron and P. Fenton, and the Royal Ontario Museum Burgess Shale Project no. 29 for collecting the specimen described in this paper. S.Z. was funded by a postdoctoral fellowship at the Smithsonian Institution (Springer fund). Additional funding was provided by NSF DEB-1036260. J.A. Waters of Appalachian State University and B. Lefebvre of the Université Lyon provided valuable input to improve the manuscript.

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Accepted 28 September 2014