Cambrian trilobites from the Nounan Dolomite and lower St. Charles Formation (upper Marjuman to lower Sunwaptan; Miaolingian to Furongian Series), Smith ﬁ eld Canyon, northern Utah

Non-Technical Summary. — Distinctive changes in carbon isotope curves are used extensively alongside trilobite faunal turnover in the international correlation of Cambrian strata. One such isotopic signature, called “ SPICE ” (Steptoean Positive Isotope Carbon Excursion), is widely used, but in North America, the co-occurring trilobite fossils have never been illustrated. We here describe, discuss, and illustrate the 34 trilobite species (two new) that occur below, within, and above the SPICE from the same section where the carbon isotope data were collected in Utah. The illustration of the specimens, rather than just listing taxa, allows other scientists to evaluate the conclusions made here: the SPICE began in the Aphelaspis Biochron and ended within the Elvinia Biochron. Abstract. — The trilobite faunas that occur with the Steptoean Positive Isotope Carbon Excursion (SPICE) at Smith ﬁ eld Canyon, Utah, have been reported, but not illustrated. Given the importance of the SPICE at this section for international correlations, the trilobites from new collections from the upper Nounan Dolomite to lower St. Charles Formation at Smith ﬁ eld Canyon are reported herein and integrated with the previously reported taxa. Trilobite assemblages indicate that the upper Cedaria to the Ellipsocephaloides biozones (Miaolingian Series, Guzhangian Stage to Furongian Series, Jiangshanian Stage) are present stratigraphically below or above the SPICE. Some of the taxa reported herein may represent new species, but they are not represented by well-enough preserved specimens and are left in open nomenclature. However, Kingstonia smith ﬁ eldensis n. sp. and Bromella utahensis n. sp. are named on the basis of common and well-preserved specimens. New carbon isotope data from Smith ﬁ eld Canyon from an overlapping section of the lower St. Charles Formation, that add to the overall shape of the SPICE curve, are presented. The new δ 13 C values above the Elvinia Biozone range from – 0.36 ‰ to +1.5 ‰ , con ﬁ rming that the SPICE concludes within the Elvinia Biozone.


Introduction
The Steptoean Positive Isotope Carbon Excursion (SPICE) is an event broadly used for correlation of the Furongian Series worldwide (Saltzman et al., 2004;Geyer, 2019;Peng et al., 2020).The strata containing the SPICE record in northern Utah provides a continuous high-resolution δ 13 C stratigraphy for the upper Miaolingian to Furongian series along with a detailed trilobite biostratigraphy and U-Pb calibrated maximum depositional ages of <494 Ma (Cothren et al., 2022).This combination of features makes this SPICE record in northern Utah probably one of the most important SPICE records in Laurentia and worldwide and allows for testing ideas about correlation, biologic evolution, and the Cambrian timescale.
The Smithfield Canyon section of northern Utah is one of the fundamental locations used to establish the SPICE as an event for international correlation (Saltzman et al., 2004;Geyer, 2019;Peng et al., 2020), and the trilobites from this section are important for establishing the Laurentian biostratigraphic range of the SPICE and its international correlation.The base of the international Furongian, Paibian Stage, is determined by the first appearance of the Glyptagnostus reticulatus (Kobayashi, 1938) in Paibi, China.Biostratigraphic correlation of the base of the Furongian to Laurentia is based on the first appearance of G. reticulatus, which co-occurs with Aphelaspis fauna at the base of the Steptoean Stage of Laurentia (Palmer 1962;Peng et al., 2004).However, agnostids, which are crucial in international correlations (Peng et al., 2020), are essentially absent from the lower part of the Smithfield Canyon section; thus, correlations require the use of polymeroid trilobites, which are less cosmopolitan.

*Corresponding author
The trilobites used for the original biostratigraphy in Smithfield Canyon were identified by Allison Palmer in Saltzman et al. (2004), but unfortunately they were never illustrated to allow re-evaluation of the identifications.The recent high-resolution δ 13 C stratigraphic study by Cothren et al. (2022) re-documented the SPICE at this section and calibrated it using high-precision chemical abrasion-isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) of detrital zircons, yielding maximum depositional ages (MDAs) of the excursion and additional trilobite collections with preliminary results.
The goal of this study is to present the details of the trilobite paleontology of the new material collected for this geochemical analysis and provide refinement of the biostratigraphy originally reported by Saltzman et al. (2004).A parallel goal is to present new δ 13 C chemostratigraphy from a measured section that overlaps with the SPICE section from Cothren et al. (2022) to better identify the end of the SPICE.

Geologic background
Regional geology of the Nounan and St. Charles formations.-TheCambrian (Marjuman-Sunwaptan) Nounan and St. Charles formations are part of a thick Ediacaran-Devonian stratal package exposed in the Bear River Range of southeastern Idaho and northern Utah (e.g., Maxey, 1958;Fig. 1.1).The St. Charles Formation (300 m thick) is divided into the basal ∼20 m thick, siliciclastic-rich Worm Creek Member and overlying informal upper carbonate member.In the northernmost exposures of these strata, in southeastern Idaho, the Worm Creek Member and the underlying Nounan Dolomite (300 m thick) contain two to four laterally discontinuous, overall upward-fining cycles of feldspathic arenite that transition to micrite and dolomicrite, wackestone, and packstone (Wakeley, 1975;Todt, 2014;Link et al., 2017).The upper Nounan and lower St. Charles formations are regionally correlative to the upper Frenchman Mountain Dolostone, Dunderberg, and Nopah formations in the central Great Basin, Utah, Nevada, and Arizona (Rowland and Korolev, 2011;Karlstrom et al., 2020;Rowland et al., 2023); the Bonanza King and Nopah Formations in Death Valley, CA (Montañez et al., 2000); and the Orr Formation in the House Range, Utah (Baker, 2010;Fig. 2).
While for much of western Laurentia, the late Cambrian is a period of putative tectonic quiescence, this region experienced dynamic magmatism and uplift.A combination of normal faulting and thermal subsidence south (current geography) of the dextral-normal Snake River Transfer Fault created the Worm Creek depocenter (Lund, 2008), which received clastic detritus from Cambrian plutons exhumed by uplift of the Lemhi Arch (Link et al., 2017).Quartzites of the Worm Creek Member are interpreted to represent the influx of siliciclastic sediment at the second-order Sauk II-III transition maximum lowstand within the greater transgressive regime across Laurentia during Cambrian time (Sloss, 1963;Saltzman et al., 2004).
The upper contact between the Nounan Formation and the overlying Worm Creek Member is seemingly gradational with an increase in siliciclastic material up-section.The Worm Creek Member comprises tan to pale-pink variably dolomitic orthoquartzites that are fineto medium-grained, trough-cross bedded, and plane bedded.At the top of the member, orthoquartzites are interbedded with thin cryptalgal carbonate beds, suggesting a gradational contact.The lower part of the overlying informal upper member of the St. Charles Formation is lithologically similar to the uppermost Nounan Formation at this locality, dominated by sandy trilobite grainstone.
The δ 13 C values in the strata overlying those presented by Cothren et al. (2022) gradually decrease toward background values within the Elvinia, Taenicephalus, and Ellipsocephaloides biozones (193-245.5m), capturing apparent carbon cycle stabilization following the SPICE.The δ 13 C values range from -0.36‰ to +1.5‰, with a mean value of +0.71‰.The δ 18 O values have a weak correlation with δ 13 C values (R 2 = 0.35), indicating that the δ 13 C values are likely primary (Fig. 3).The end of the SPICE is defined as the inflection point in which the rate of change (first derivative) of the LOESS fit of δ 13 C values returns to 0, indicating no change.From our analysis, the SPICE concludes at 191 m, within the Elvinia Biozone, stratigraphically above the last occurrence (LO) of Irvingella.
These new data allow a complete profile of the SPICE to be captured.The end of the SPICE within the Elvinia Biozone, stratigraphically above the LO of Irvingella, follows similar trends in the Great Basin, in which the SPICE concludes in the upper Elvinia Biozone, above the I. major subzone, with δ 13 C values stabilizing toward near background values in the Taenicephalus Biozone (Saltzman et al., 1998).We do not observe the small +3‰ δ 13 C excursion near the Pterocephaliid-Ptychaspid biomere boundary recorded in Smithfield Canyon by Saltzman et al. (2004).While two points, at 241 m and 243 m, depart from background values at ∼2‰, this is not a well-defined "excursion" as it lacks a rising or falling limb.The post-SPICE positive excursion captured by Saltzman et al. (2004) may not be recorded in this work due to lower sampling resolution and/ or uncertainty regarding the section location and lack of data availability from Saltzman et al. (2004).Alternatively, rock may be missing due to a subtle unconformity or hiatal surface; however, biostratigraphy points toward a near-continuous section.
Biostratigraphy Saltzman et al. (2004) presented the initial biostratigraphy of the SPICE in Smithfield Canyon on the basis of material identified by Allison Palmer (in Saltzman et al., 2004).Unfortunately, none of the trilobite specimens that this biostratigraphy was based on have been illustrated.This paper integrates the list of taxa identified by Palmer present in the Institute of Cambrian The Cedaria Biozone is presently poorly documented on the basis of the occurrence of Glaphyraspis sp.indet., Coosia?sp.indet., and Menomonia cf.M. turberculata Rasetti, 1965 at USNM loc.44289.The biozone diagnostic species is Menomonia cf.M. turberculata, which is known from a single librigena with the characteristic ornamentation and shape of M. turberculata.This taxon is from the Cedaria Biozone of the Maryville Limestone of the East Coast (Rasetti, 1965).By contrast, Glaphyraspis sp.indet., represented here by small cranidia, is similar to an unnamed species typically found in the lower portion of the Crepicephalus Biozone in the Great Basin (Eby, 1981).The small cranidia identified as Coosia?sp.indet.could belong to meraspides of any related taxon to Coosia.No pygidia are associated with the cranidia.
The Dicanthopyge Biozone has not been documented in the section by either Saltzman et al. (2004) or this study.However, Tumicephalus depressus, which occurs with Aphelaspis spp. in the Nounan Formation, is typically found in the Dicanthopyge Biozone of Nevada and Utah (see Palmer, 1965).

Materials and methods
Materials.-Allspecimens were found as isolated sclerites and for the most part in poorly fossiliferous strata.As a result, the association of different sclerites is presumed to represent a single taxon if similar associations have been previously reported (e.g., Palmer, 1965;Westrop, 1986;Sundberg, 1999).However, at localities with multiple taxa present, association of the different sclerites is difficult.As a result, several taxa are herein left in open nomenclature following Bergstrom (1988), with "cf." representing that the material is not abundant or well-enough preserved to demonstrate that it firmly belongs to the assigned taxon and "aff."used to designate a probable new species affiliated with the species, but the samples and or preservation of the specimens are not enough to justify naming a new species.
Illustrated specimens have been coated with colloidal graphite followed by ammonium chloride sublimate.Specimen orientation for photography and measurements is primarily with the cranidial anterior border and/or palpebral lobes, librigenal border, or pygidial border in a horizontal plane.Some photographs of specimen counterparts (negative relief) have been Journal of Paleontology:1-30 digitally inverted using Adobe Photoshop and are labeled in the figure captions as "inverted."This inversion included changing positive images to negatives (changing black to white and vice versa) and flipping the image horizontally.Some materials are not preserved well enough to justify illustration, but they are mentioned so their occurrence can be noted (e.g., Agnostid sp.indet.).
Carbon isotopes.-Samplepreparation and carbon-isotope analyses were conducted using the methods outlined by Cothren et al. (2022, supplemental data).
Repositories and institutional abbreviations.-Specimensdiscussed within this paper are housed in the United States Natural History Museum (USNM).Other abbreviations include American Museum of Natural History (AMNH) and Institute of Cambrian Studies, University of Chicago (ICS).

Systematic paleontology
Sundberg is responsible for all taxonomic assignment of the new material from Smithfield Canyon.

Phylum Arthropoda von Siebold, 1848
Remarks.-Citation of the authorship of the phylum has been variable; however, Hegna et al. (2013) discussed this inconsistency in the authorship, demonstrating that Arthropoda von Siebold, 1848 is the correct citation.
Remarks.-A single, very small cephalon was found from the Nounan Formation (USNM loc.44289), which cannot be identified to generic level and is left in open nomenclature.
Remarks.-There are conflicting views as to which species of Pseudagnostus are valid or definable.Peng and Robison (2000) and Chatterton (2020) viewed P. josepha as a variable species that includes several previously named species.By contrast, Westrop and Eoff (2012) viewed the taxa of Pseudagnostus as more constrained in morphology and removed some taxa that Peng and Robison (2000) included in their synonymy.Of note is Westrop and Eoff's (2012, p. 208) removal of P. communis (Hall and Whitfield, 1877) from P. josepha that was proposed by Peng and Robison (2000).Westrop and Eoff (2012, p. 209) pointed out that the type material of P. communis has never been photographically illustrated and is poorly known from the type area.Chatterton and Gibb (2016;Chatterton 2020) noted that P. josepha is widespread in the McKay Group, Canada, but is designated as Pseudagnostus cf.P. josepha due to its quality of preservation.
The limited samples preserved in limestone from the St. Charles Formation show a combination of features of P. josepha preserved in limestone from Alberta (Westrop, 1986) and China (Peng and Robison, 2000) and Pseudagnostus cf.P. communis preserved in limestone from Newfoundland (Westrop and Eoff, 2012).In terms of cephalon shape (cephalon length/width ratio), the grouping of the St. Charles Formation specimens with the China and Alberta specimens of P. josepha (Fig. 6.1) and their separation from Pseudagnostus cf.P. communis from Newfoundland suggest their placement within P. josepha.This ratio changes during ontogeny from around 97% to 106% cephalic length for P. josepha.By contrast, Pseudagnostus cf.P. communis from Newfoundland show a gradual decrease from 94% to 90% of cephalic length, suggesting Westrop and Eloff's (2012) separation of the Newfoundland specimens from the Alberta and China specimen.Glabellar widths (tr., measured at the termination of the basal lobes) of the samples from the St. Charles Formation are a bit wider than P. josepha from China and Alberta (Fig. 6.2); however, these three localities form an overall trend of glabellar width around 35% to 40% of cephalon width from 2.0 to 4.5 mm in cephalon length.By contrast, the material of Pseudagnostus cf.P. communis from Newfoundland centers around 33% of cephalon width regardless of cephalon length (1.5 to 5.0 mm), again justifying the separation of the Newfoundland specimens of P. josepha.Other cephalic differences between the St. Charles Formation specimens from the Newfoundland specimens include a larger and subcircular M3 delineated with a distinct F2 similar to the China specimens and a shallower median glabellar furrow, although this feature is variable in both the Newfoundland and China specimens.Overall, the St. Charles Formation specimens are most like P. josepha.
Four partial cephala from USNM loc.44289 are similar to P. josepha, but without associated pygidia, they cannot be firmly assigned to this species.
Remarks.-The specimens from USNM 44294 are most like A. subditus in the construction of the frontal area of the cranidium and shape of the librigena.However, the pygidium is more of a rectangular outline and is more like Journal of Paleontology:1-30 A. brachyphaspis Palmer, 1962.This is not unexpected given that Palmer (1965, fig. 10) suggested that this species gave rise to A. subditus.The specimens from USNM 44295 (Fig. 7.11) have a more elongated pygidium, more typical of the species.Palmer (1965, p. 60) reported this species from the upper part of the Aphelaspis Biozone.
A more unusual feature of these specimens from USNM 44294 is that the occipital ring has essentially two small occipital nodes, one near the middle of the ring and the other posterior, near the posterior margin (Fig. 7.2, 7.4).This is not a feature of A. subditus or any other member of the genus from the Great Basin.However, Rasetti (1965) reported A. arses (Walcott, 1916a) from the Nolichucky Formation from Tennessee that has both an occipital spine and a node.Furthermore, another species with a large occipital spine similar to A. arsoides reported from Tennessee (Rasetti, 1965)  Holotype.-USNM144677,cranidium, from the Nolichucky Formation, Jefferson County, Tennessee, USA.
Remarks.-The specimens assigned to this species are similar to the type material from the Nolichucky Formation, Tennessee, in having a long, flat-lying, and narrow occipital spine (Fig. 7.13, 7.17), horizontal intraocular region, pitting in the furrows of the cranidium (Fig. 7.14), librigenal features, and pygidial features.These specimens are dissimilar from the Tennessee species in the absence of an occipital spine in smaller specimens and less-pronounced pitting in the cranidial and librigenal anterior borders, which is the reason for the cf.designation.These specimens differ from A. arses also from Tennessee in the latter's possession of a dorsally arched, broad-based, occipital spine; pitting in the furrows of the cranidium; and more-divergent anterior branches of the facial sutures.The specimens are also very similar to the A. subditus from USNM loc.44294, but the latter lacks the long occipital spine in specimens of the same size, pitting in the cranidial furrows, and the nearly horizontal intraocular regions.This species is also similar to A. spinosa Palmer, 1954  Remarks.-Palmer(1965) discussed the similarity of Bromella to Aphelaspis, Dytremacephalus, and Prehousia, but the differences between these genera and Bromella are consistent as outlined by Palmer (1965).
Fine granules occur on the cranidia, librigenae, and pygidia testate surfaces, smooth on internal surfaces.Terrace lines on the cranidial anterior border and lateral and ventral margins of the librigenal border.Genal caeca occurs on frontal area and genal area of librigena.Exoskeleton relatively thin.
Etymology.-Named after the type locality in Utah.
Remarks.-The pygidia from the Nounan Formation differ from the two pygidia of Bromella veritas Palmer, 1965 (pl. 18, figs. 5, 9) in possessing longer axes with three to four axial rings and more-pronounced pleural bands and furrows although they are roughly the same length (≈2 mm) as Palmer's illustrated specimens.These differences are the justification for assigning the Nounan specimens to a new species.Cranidial and librigenal features of both B. utahensis and B. veritas are very similar, except that the former has a granulated exoskeleton and smooth internal mold, whereas the latter has a pitted, smooth, or finely granulated surface.
Remarks.-These specimens are very similar to the type material of Dytremacephalus asperaxis Palmer, 1965 in overall cranidial and librigenal features.The "cf." designation is the result of the palpebral lobes appearing to be slightly longer and the surface slightly more granular in these specimens, but it is difficult to ascertain given the fragmentary nature of the Smithfield Canyon specimens.This species is also similar to D. granulosus Palmer, 1954, but the latter differs by its coarser surface granulation.Holotype.-USNM123319, cranidium, from the Lion Mountain Sandstone, Riley Formation, White Creek, Texas, USA.
Remarks.-The materials from USNM loc.44297 are fragmentary and cannot be placed in confidence.These specimens differ from D. granulosus from Texas in having a finer granulation and a more convex anterior border.The species from USNM loc.44297 are unusual because of their granulated sclerites and relatively deeper glabellar furrows than most taxa from the Aphelaspis, Dicanthopyge, and Prehousia biozones.Elburgia?sp.indet.Figure 10.5-10.7 Occurrence.-Nounan Formation (Dunderbergia Biozone), Smithfield Canyon, Utah (see Appendix).
Remarks.-The material from USNM 44298 is small cranidia, mostly exfoliated and fragmented; thus, their placement within the genus or to a specific species is not possible.The material is tentatively assigned to Elburgia due to the overall glabellar shape, character of the glabellar furrows, and relatively long palpebral lobes.Ontogenetic changes may explain differences in relative glabellar shape and length, palpebral length and positions, and length of the preglabellar area observed in smaller specimens from the larger specimens illustrated by Palmer (1965; for example, see in these morphologies during ontogeny illustrated by Sundberg, 2020;Sundberg and Webster, 2022).
Remarks.-Relatively large librigenae similar to I. similis (Walcott, 1884) are from USMN loc.44301.These librigenae have a broad, convex lateral border that terminates in a long and curved genal spine (see Palmer, 1965, pl. 2, fig.1).Of particular note, Westrop et al. (2010) assigned librigenae with genal spines that are narrower based and shorter to Iddingsia and related taxa.
A poorly preserved pygidium with a semicircular outline, narrow border, tapering axis with four axial rings, and weakly defined pleural and intrapleural furrows is similar to pygidia assigned to Kindbladia by Frederickson (1948, pl., fig. 21) and Palmer (1965, pl. 3, fig. 4).However, Hohensee and Stitt (1989) assigned a transversely elongated pygidium with a very blunt axis as belonging to the type species of Kindbladia, K. wichitaensis (Resser, 1942).Hohensee and Stitt (1989, p. 870) suggested that the pygidium assigned to K. affinis (Walcott, 1884) by Palmer (1965) should be tentatively assigned to Iddingsia robusta (Walcott, 1884).Due to the poor nature of the preservation, the nomenclature of this pygidium is left open.Palmer in Saltzman et al. (2004) also identified Kindbladia sp. from ICS1440, which is at the same level as USNM 44301 from which the poorly preserved pygidium was recovered.
Remarks.-A single well-preserved cranidium from USMN loc.44301 and one poorly preserved cranidium from USNM loc.44300 were recovered.These cranidia are similar to Pseudosaratogia leptogranulata Palmer, 1960, but the latter differs in possessing a longer and wider preglabellar area, a less-curved anterior border, a more-tapered glabella, and more-pronounced lateral glabellar furrows.The difference in glabellar tapering may be the result of ontogeny with the specimen from USMN loc.44301 having a length of 6.7 mm versus the type specimen having a length of 11.3 mm.
Remarks.-These specimens are typically small in the collections but do not represent a juvenile of the co-occurring Aphelaspis.The specimens have an upturned anterior border with a stronger curvature, swollen preglabellar area, and dorsally sloped intraocular area from the glabella to the  (1965, p. 90) stated that this species is commonly found in the Dicanthopyge Biozone; however, its occurrence with Aphelaspis cf. A. arsoides and below A. subditus either extends the range of T. depressus into the Aphelaspis Biozone or extends the range of A. suditus into the Dicanthopyge Biozone.Palmer (1965) included Aphelaspis tumifrons Resser, 1938into Tumicephalus. Rasetti (1965) reported A. tumifrons commonly from the same horizons as A. arsoides in the southern Appalachians; at Smithfield Canyon, it occurs with Aphelaspis cf. A. arsoides.
Remarks.-Only a few small cranidia were found, and without associated pygidia the genus cannot be firmly assigned.
Remarks.-The pygidium found from USNM loc.44296 has a wide border that is slightly upturned at the edge, a high profile with a steep descent from the axis to the anterior border, and no evidence of the pleural furrows crossing the border.In these features, the pygidium is similar to Cheilocephalus brachyops Palmer, 1965, C. brevilobus (Walcott, 1916b) Holotype.-USNM98750 cranidium from the Bonneterre Dolomite, Missouri, USA.
Remarks.-A cranidium and a few pygidia were found at USNM loc.44290.These samples are very similar to specimens reported by Eby (1981) from the upper Cedaria to lower Crepicephalus biozones, House Range, Utah.Eby, in his dissertation, reported 25 cranidia and 56 pygidia of Prochuangia?berryi under a new genus, which has yet to be formally established.These sclerite associations illustrate that this species does not belong to Prochuangia as suggested by Lochman (1940) or Genevievalla as reported by Tasch (1951) and Robison (1960) on the basis of cranidial and/or pygidial differences.Rasetti (1965, p. 114) noted that the pygidia from Virginia are similar to Coosia or a related taxon, of which the authors agree.However, the cranidia are unlike any of the Coosia or related taxa in its nearly parallel-sided glabella that extends to the anterior border furrow.At present, this species is placed into "Coosella" on the basis of the pygidial characteristics, but this placement is problematic, and it probably belongs to a new genus.Specimens reported here are not complete or abundant enough to justify proposing a new generic name.
Remarks.-The specimens from Smithfield Canyon are similar to those of Saratogia (I.) fria from the St. Charles Formation of Idaho (Lochman and Hu, 1959) in glabellar shape, relative length of the preglabellar area, position of palpebral lobes, and angle of anterior suture.However, the type material (Lochman and Hu, 1959, pl. 59, figs. 1-11;Ludvigsen and Westrop, 1983, pl. 9, fig. 4) possesses a long occipital spine, which is lacking in the specimens from Smithfield Canyon, which possess only a small occipital node.Bell and Ellinwood (1962) figured two specimens (pl. 53, figs. 19, 20) from Texas without occipital spine or node that they assign to S. fria.They mention all of the cranidial features are the same other than the spine, but one of the key features they discussed for S. fria from Texas is the presence of coarse granules on the "occipital ring, occipital spine, posterior limbs, and preoccipital glabellar lobes…" (Bell and Ellinwood, 1962, p. 394).These granules are not apparent on the type, the Texas (Ludvigsen and Westrop, 1983, pl. 9 Remarks.-Thesingle cranidium from the St. Charles Formation is similar to Wilbernia expansa in its short frontal area, concave anterior border, wide intraocular area of the fixigena, and slightly tapered glabella.A difference between specimens illustrated by Frederickson (1949, pl. 72, figs. 13-16) and those illustrated by Bell and Ellinwood (1962, pl. 54, figs. 11, 12) is the shorter (sag.)anterior border in the latter.A co-occurring librigena (Fig. 20.5) also has a convex border and is also assigned to Wilbernia aff.W. expansa.
Remarks.-The specimens from the St. Charles Formation are similar to Wilbernia explanata in their long frontal area, relatively flat anterior border, wide intraocular area of the fixigena, slightly tapered glabella, and wide pygidium.Most of the specimens reported here are fragmented, but they vary in the length of the preglabellar area, primarily on the basis of specimen size as suggested by Westrop (1986, p. 43).An additional difference between specimens illustrated by Westrop (1986, pl. 12, fig.5) and herein is the rounded terminal piece of the pygidial axis versus the pointed termination of the specimens illustrated herein.The specimens are left in open nomenclature due to the incomplete cranidia and the rounded terminal piece of the pygidial axis.Wilbernia aff.W. pero (Walcott, 1890) Figure 20.1-20.3Occurrence.-St.Charles Formation (Ellipsocephaloides Biozone), Smithfield Canyon, Utah (see Appendix).
Remarks.-The three cranidia from the St. Charles Formation are similar to Wilbernia pero in their short preglabellar area, narrow intraocular area of the fixigena, and nearly parallel-sided glabella.Most of the sclerites reported here are fragmented but differ from previously illustrated specimens (Bell et al., 1952, pl. 34, fig. 5a-c;Bell and Ellinwood, 1962, pl. 54, figs. 19, 21;Grant, 1962, pl.139, fig. 8a-c;Westrop, 1986, pl. 13, figs. 1-3) in possessing a less convex anterior border and a less constricted (hourglass shape) glabella with a strongly rounded frontal lobe similar to those illustrated by Frederickson (1949, pl. 72, figs. 7-9).These specimens are similar to other species of Wilbernia and specifically W. pero but are different enough that they may represent a new species.The specimens are left in open nomenclature until additional material can be found.
Terrace lines on the cranidial anterior border and lateral and ventral margins of the librigenal border.Other surfaces may have a small punctuate pattern, but this may be the result of preservation.Exoskeleton relatively thick.
Etymology.-Named after the type locality in Smithfield Canyon.
Remarks.-Many aspects of this new species are similar to Kingstonia inflata Resser, 1938, including the cranidial outline, anterior and posterior cranidial border and furrows, exoskeleton thickness, and pygidial shape and furrows.However, unlike most representatives of Kingstonia, this species has well-defined cranidial and pygidial furrows and a relatively long (sag.)occipital ring.Also, by contrast is the apparent absence of lateral glabellar furrows and pygidial axial ring furrows and pleural/interpleural furrows on the internal molds of the sclerites (see Fig. 21.11,21.25).Westrop (1992, p. 244) discussed a potential synapomorphy linking taxa in Kingstoniidae that consists of a very short (5-10% glabellar length-calculated from specimens illustrated by Eby, 1981) occipital ring that forms a transverse band that is depressed below the adjacent portions of the glabella.This unique narrow occipital ring occurs in Kingstonia, Bynumia Walcott, 1924, Ankoura Resser, 1938, and Bynumina Resser, 1942. Westrop (1992) tentatively included Blountia (Walcott, 1916b) and Maryvillia Walcott, 1916b into Kingstoniidae, which was further substantiated by Armstrong et al. (2020).The new species reported here clearly does not possess this synapomorphy, with an occipital ring nearly 20% glabellar length and occurring slightly at the same elevation as the adjacent glabellar lobes and the hourglass shape of the glabella.
Subfamily Blountiinae Lochman in Lochman and Duncan, 1944 Genus Blountia Walcott, 1916b Remarks.-Afew cranidia and pygidia were found at USNM loc.44290.These samples are unlike the previously named species but are very similar to specimens reported by Eby (1981) from the upper Cedaria Biozone, House Range, Utah.
Figure 22 Occurrence.-St.Charles Formation (Taenicephalus Biozone), Smithfield Canyon, Utah (see Appendix) Remarks.-These specimens are most similar to Noelaspis in the placement and lengths of the palpebral lobes, glabellar furrows, lateral glabellar furrows, fixigenal width, frontal area, and pygidial outline.However, the specimens are questionably assigned to Noelaspis on the basis of the stronger rounded frontal lobe, narrower glabella, and strongly upsloping intraocular region of the fixigena.The associated hypostome is similar to the closely related Orygmaspis Resser, 1937 as illustrated by Ludvigsen et al. (1989, pl. 10, fig. 5).
Noelaspis has previously been reported from the Beothuckia duomenta fauna of Newfoundland, which is compared to the Stigmacephalus oweni fauna and Ellipsocephaloides Biozone of Alberta (Westrop, 1986, Ludvigsen et al., 1989).
Remarks.-Two small cranidia have a parallel-sided glabella, wide fixigena, and a very thin anterior border similar to a form found by Eby (1981)  Holotype.-CranidiumUSMN 144696 from the Maryville Limestone, Hawkins County, near Rogersville, Tennessee, USA.
Holotype.-Articulatedcarapace (UA14129) from the McKay Group, high in Green Creek Section, British Columbia, Canada.

Figure 1 .
Figure 1.(1) Map showing the location of the Smithfield Canyon section (black star, "SF") in regional context.Gray polygons represent the aerial extent of mapped Nounan and St. Charles formations.Modified from the Stage Geologic Map Compilation (Horton et al., 2017) and Wakeley (1975).(2) Portion of the Naomi Peak 7.5-foot quadrangle showing the locations of the three measured sections.Basemap: 2013 National Geographic USA topographic map, projection: NAD 1983 UTM Zone 12N.
Figure 1.(1) Map showing the location of the Smithfield Canyon section (black star, "SF") in regional context.Gray polygons represent the aerial extent of mapped Nounan and St. Charles formations.Modified from the Stage Geologic Map Compilation (Horton et al., 2017) and Wakeley (1975).(2) Portion of the Naomi Peak 7.5-foot quadrangle showing the locations of the three measured sections.Basemap: 2013 National Geographic USA topographic map, projection: NAD 1983 UTM Zone 12N.

Figure 2 .
Figure 2. Working hypothesis for the correlation of the Nounan and St. Charles formations in northern Utah with formations in the Great Basin.Approximated biomere boundaries and their corresponding estimated time boundaries.NA = North American; WC = Worm Creek Member; Mtn = Mountain.

Figure 3 .
Figure 3. Composite lithostratigraphy of the Smithfield Canyon sections, estimated Sauk II-III boundary, biozones, and biomeres.Solid lines indicate well-defined biostratigraphic boundaries (e.g., first occurrence and last occurrence of biozone fauna are <1 m), and dashed lines indicate estimated biozone boundary position; δ 13 C stratigraphy: black points are from this study, and red points are from Saltzman et al. (2004); δ 13 C and δ 18 O cross plot indicating a lack of co-variation between δ 13 C and δ 18 O values and arguing that δ 13 C values are likely primary.Aph = Aphelaspis; Di = Dicanthopyge; Pr = Prehousia; Fm. = Formation; Mbr.= Member; VPBD = Vienna PeeDee Belemnite.Modified from Cothren et al. (2022).

Figure 4 .
Figure 4. Composite stratigraphic column and trilobite ranges of the upper Nounan and lower St. Charles formations from Smithfield Canyon, Utah.Taxa occurrences and localities listed in red represent data from Saltzman et al. (2004); those listed in black represent new data from this study.sp = no specific identification by Saltzman; ?= questionable occurrence of the taxon.Section modified from Cothren et al. (2022).

2022
12.5) are also similar to the smaller cranidium and pygidium of I. flohri illustrated by Westrop and Adrain (2016, fig.9G-K), although the cranidial anterior border and border furrow are very faint in the specimen reported here.Due to the fragmentary nature of the larger specimens, these samples are questionably placed into I. flohri.Palmer in Saltzman et al. (2004) reported Irvingella cf.I. flohri from ICS-1440 in Smithfield Canyon.Apachia prima, Cothren et al., fig.2.8.Occurrence.-St.Charles Formation (Dunderbergia Biozone), Smithfield Canyon, Utah (see Appendix).
, fig.5), or the Smithfield material, and the forms without an occipital spine may represent the same species as the Smithfield material.The Smithfield material is left in open nomenclature due to the lack of well-preserved material.Genus Wilbernia Walcott, 1924 Type species.-Ptychopariapero Walcott, 1890 from the Wilberns Formation, Texas (by original designation).Wilbernia aff.W. expansa Frederickson, 1949 Figure 20.4-20.11Occurrence.-St.Charles Formation (Ellipsocephaloides Biozone), Smithfield Canyon, Utah (see Appendix).