New edrioasteroid (Echinodermata) from the Spence Shale (Cambrian), Idaho, USA: further evidence of attachment in the early evolutionary history of edrioasteroids Rongqin Wen, LoRen e. BaBcock, Jin Peng & RichaRd a. RoBison A new species of Totiglobus, T. spencensis (class Edrioasteroidea, order Edrioasterida), is reported from the Spence Shale (Cambrian: Miaolingian Series, Wuliuan Stage) of eastern Idaho. The holotype, which was evidently buried at the base of a tempestite bed, is attached by a basal disk to a hyolithid conch. In contrast to the closely related species T. nimius, which attached to mat-stabilized sediment by means of a suction disk on the aboral surface, T. spencensis attached­to­hard­substrates­by­means­of­an­attachment­disk­on­the­aboral­surface.­Edrioasteroids­first­evolved­ mechanisms for attaching to hard substrates in the Wuliuan Age, and T. spencensis is thus among the earliest-known edrioasteroids­to­show­this­habit.­By­the­Drumian­Age,­attachment­to­hard­substrates­had­become­the­dominant­post- larval life habit of edrioasteroids. • Key words: Edrioasteroid, Cambrian, Spence Shale, Idaho, Cambrian Substrate Revolution. WEN, R., BABCOCK, L.E., PENG, J. & ROBISON, R.A. 2019. New edrioasteroid (Echinodermata) from the Spence Shale (Cambrian),­Idaho,­USA:­further­evidence­of­attachment­in­the­early­evolutionary­history­of­edrioasteroids.­Bulletin of Geosciences 94(1),­115–124­(2­figures,­1­table).­Czech­Geological­Survey,­Prague.­ISSN­1214-1119.­Manuscript­ received­October­30,­2018;­accepted­in­revised­form­March­5,­2019;­published­online­March­21,­2019;­issued­March­ 31,­2019.­ Rongqin Wen, Resources and Environmental Engineering College, Guizhou University, Guiyang 550025, China & School of Earth Sciences, The Ohio State University, Columbus, Ohio 43210, USA • Loren E. Babcock, School of Earth Sciences, The Ohio State University, Columbus, Ohio 43210, USA; [email protected] • Jin Peng, Resources and Environmental Engineering College, Guizhou University, Guiyang 550025, China; [email protected] • Richard A. Robison, Department of Geology, University of Kansas, Lawrence, Kansas, 66045, USA The Cambrian Period was a time of sweeping reorgan - o iostelians (Zamora et al. 2017), evidently attached to or i­zation­in­marine­ecosystems.­A­series­of­diversification­ stuck to mat-stabilized surfaces in post-larval phases of events resulted in the introduction of varied taxa, and life. Twelve named genera of edrioasteroids, plus some evolutionary radiation was accompanied by fundamental undetermined forms, have been recorded from Cambrian changes in substrate consistency leading, ultimately to deposits­worldwide­(Pompeckj­1896;­Jaekel­1899,­1921;­ more­fluidized­sediment­surfaces.­For­echinoderms­and­ Schuchert­1919;­Bassler­1935,­1936;­Bell­&­Sprinkle­1978;­ suspension-feeders in general, the Cambrian was a time Jell­et al.­1985;­Smith­1985;­Sprinkle­1985;­Smith­&­Jell­ of evolutionary experimentation (e.g., Domke & Dornbos 1990;­Ubaghs­1998;­Fatka­et al.­2004;­Parsley­&­Prokop­ 2010, Zamora & Smith 2010, Zamora et al. 2017, Lefebvre 2004;­Zamora­et al.­2007,­2013,­2015;­Domke­&­Dornbos­ & Lerosey-Aubril 2018). One interesting aspect of the 2010; Lefebvre et al. 2010; Zamora & Smith 2010; Zhao paleoecology of the early to mid-Cambrian (late Epoch et al.­2010;­Zamora­2013;­Guensburg­&­Rozhnov­2014;­ 2 to Miaolingian Epoch) was the widespread presence Robison et al.­2015;­Lefebvre­&­Lerosey-Aubril­2018).­ of mat-stabilized sediment surfaces in shallow marine Of these, nearly all show evidence of attachment (Tab. 1). ecosystems (e.g.,­Seilacher­&­Pflüger­1994,­Bottjer­et al. In this paper, we discuss attachment in a new species of 2000).­Prior­to­the­widespread­fluidization­of­substrates­ the Cambrian edrioasteroid Totiglobus. This example by burrowing animals (referred to as the Cambrian presents an interesting addition to the life habit information Substrate­Revolution;­Bottjer­et al. 2000), some early previously­documented­for­the­genus­(Bell­&­Spinkle­ echinoderms, including taxa assigned as helicoplacoids 1978,­Domke­&­Dornbos­2010,­Zamora­et al. 2017). (Bottjer­et al. 2000), edrioasteroids (Sumrall & Sprinkle The new species was collected from the Spence 1992,­Domke­&­Dornbos­2010),­eocrinoids,­and­hom- Shale (Cambrian: Miaolingian Series, Wuliuan Stage) in DOI 10.3140/bull.geosci.1730 115 Bulletin of Geosciences • Vol. 94, 1, 2019 southeastern­Idaho.­Wuliuan­shales­of­the­Great­Basin,­ especially­the­Spence­Shale­in­Idaho­and­Utah,­and­the­ equivalent­Chisholm­Shale­in­Nevada­and­Utah,­have­ yielded a moderately diverse fauna of echinoderms, principally from layers at the bases of tempestites (e.g., Bell­&­Sprinkle­1978,­Robison­1991,­Domke­&­Dornbos­ 2010, Robison et al.­2015).­Overall,­Laurentian­deposits­ have yielded four genera and at least seven species (Tab. 1). As discussed by Zamora et al. (2017) most of these taxa were probably attached suspension-feeders. Domke & Dornbos (2010) studied numerous specimens of Totiglobus nimius from the Chisholm Shale of Nevada and concluded that the species attached by suction, possibly with the addition of a bioglue, to mat-stabilized sediment surfaces. The Spence and Chisholm formations represent­predominantly­fine-grained­siliciclastic­or­mixed­ siliciclastic-carbonate sedimentation, including some organic-rich­black­shale­intervals,­on­a­storm-influenced­ continental shelf. As sessile, and commonly attached, metazoans, intact echinoderms were preserved after rapid in situ burial and entombment resulting from storm- related sediment disturbance and deposition (see Sprinkle Figure 1.­Geographic­occurrences­of­named­species­of­Totiglobus in 1973,­LoDuca­et al.­1997,­Robison­et al. 2015).­The­inter­- the­Great­Basin,­USA.­•­1­–­Totiglobus nimius­Bell­&­Sprinkle,­1978­ pretation of echinoderms attaching to mat-stabilized from­the­Chisoholm­Shale.­•­2­–­Totiglobus spencensis sp. nov. from the surfaces (Domke & Dornbos 2010) adds an important Spence Shale. •­3­–­Totiglobus lloydi­Sprinkle,­1985­from­the­Marjum­ detail that helps to explain occurrences of extensive Formation. echinoderm-bearing obrution beds in the Cambrian. The new Totiglobus documented here is attached Babcock­2011,­Garson­et al. 2012, Robison et al.­2015).­ by means of a basal attachment disk to a hard, shelly The polymerid trilobite fauna includes representatives of substrate. Its attachment mechanism differs from the open-shelf and restricted-shelf Laurentian environments. better-known suction-style of attachment documented Restricted-shelf polymerid trilobites present are indicative in T. nimius­(Domke­&­Dornbos­2010;­also­see­Bell­&­ of the Glossopleura Zone, open-shelf polymerid trilobites Sprinkle­1978,­pl.­6,­fig.­9).­This­specimen,­plus­another­ present are indicative of the Oryctocephalus Zone, and that has been illustrated (Robison et al. 2015,­fig.­188)­ agnostoids present are indicative of the Ptychagnostus but­not­described,­confirm­that­Totiglobus was attached in praecurrens Zone (e.g.,­ Robison­ &­ Babcock­ 2011,­ post-larval life, but had varied means of attachment and Robison et al.­2015).­Strata­of­the­Spence­Formation­are­ species-level preferences for types of stabilized surfaces. correlated with the Miaolingian Series, Wuliuan Stage, Available evidence suggests that edrioasteroids first which were formerly referred to in literature as provisional evolved the capacity for attachment to hard substrates in Series­3­and­provisional­Stage­5­(see­Cohen­et al. 2018, the Wuliuan Age of the Cambrian, and thus edrioasteroids Zhao et al. in press). from the Spence Shale are among the earliest species to Various authors have discussed the lithostratigraphy, show this habit. sequence stratigraphy, or paleoenvironmental setting of the Spence Shale (e.g., Walcott­1908,­Resser­1939,­ Sprinkle­1973,­Campbell­1974,­Gunther­&­Gunther­1981,­ Locations and stratigraphy Robison­1991,­Liddell­et al.­1997,­Bonino­&­Kier­2010,­ Robison­&­Babcock­2011,­Garson­et al. 2012, Robison The holotype of Totiglobus spencensis sp. nov. is from the et al.­2015).­The­formation­is­dominated­by­shale,­with­ type­locality­of­the­Spence­Shale­in­Spence­Gulch,­Idaho­ thin silty shale or siltstone interbeds in places. The lower (Fig.­1).­The­specimen­was­collected­by­the­Gunther­ portion of the formation tends to show dark, organic-rich family­in­1992.­The­Spence­Shale­is­rich­in­fossils­and­ shale, including black shale, beds, and the upper portion of includes a diverse polymerid and agnostoid trilobite the formation tends to be rich in tan to olive-green shales. fauna (e.g., Walcott­1908,­Resser­1939,­Sprinkle­1973,­ Liddell et al.­(1997)­and­Garson­et al. (2012) suggested Campbell­1974,­Gunther­&­Gunther­1981,­Robison­1991,­ that the extraordinary preservation of nonbiomineralized Liddell et al.­1997,­Bonino­&­Kier­2010,­Robison­&­ tissue in fossils of the Spence Shale was favored 116 Rongqin Wen et al. • New edrioasteroid from the Cambrian of Idaho during times of low or depleted levels of bottom-water Lin et al. 2008). The Idaho edrioasteroid, preserved oxygenation.­Robison­(1991)­showed­that­echinoderms­ attached to a hyolithid, is inferred to have been toppled were often preserved in articulated condition at the bases and buried rapidly by sediment smothering during a storm of tempestite beds. event­(compare­Robison­1991,­Lin­et al. 2008, Robison et al.­2015).­It­may­have­undergone­a­small­amount­of­ current transport moments before burial but is unlikely Paleoecology and Taphonomy to have been transported