Wotte and Sundberg—Small shelly fossils from the Great Basin
less prominent. Again, poor preservation prevents a secure taxonomic placement.
Phylum uncertain
Class Hyolitha Marek, 1963 Order Hyolithida Sysoiev, 1957
Family Nelegerocornidae Meshkova, 1974 Genus Microcornus Mambetov, 1972
Type species.—Microcornus parvulusMambetov, 1972 (p. 268, fig. 1a–1e); Rhombocorniculum cancellatum Zone, Geres
Member, basal Shabakty Formation (lower Cambrian; upper Atdabanian Stage; correlated with the lower Cambrian Stage 3); Ushbas River, Malyi (Lesser) Karatau, Kazakhstan.
Microcornus sp. Figure 5.23–5.32
Occurrence.—Several poorly preserved internal molds of the Indian Springs Canyon and Montezuma Range sections (I 1, I 2, I 3, I 7, I 12, I 16, M 5); Montezuman Stage. Several internal molds or shells from the Echo Canyon (E 10, E 12), Grassy Spring (GS 13, GS 17), Groom Range (GR 5, GR 11), Log Cabin Mine (LC 6, LC 7), Oak Spring Summit (OS 5, OS 7), and Split Mountain (SM 14) sections; Dyeran Stage.
Description.—Slender shells or internal molds. Aperture and apex often incomplete. Incomplete specimens normally ~2mm long (~3.3mm maximum; Fig. 5.27). Dorsal side with distinct, rounded median ridge. Ventral side flat to gently convex. Lateral sides rounded. Cross-section sub-triangular. Protoconch absent, but probably separated from the mature conch by a shallow constriction (see Fig. 5.23). Surface sculpture not preserved.
Remarks.—Microcornus differs from Parkula Bengtson in Bengtson et al. (1990) by a more prominent dorsal median ridge and a sub-triangular cross-section. The flat to gently convex ventral side and the sub-triangular cross-section of the conch indicate affiliation to M. eximius Duan, 1984 or M. petilus Bengtson in Bengtson et al., 1990. Microcornus eximius is characterized by a flat ventral side, whereas M. petilus has a convex ventral side (Demidenko in Gravestock et al., 2001). However, the absence of opercula prevents an assignment to a species.
Family unassigned Genus Parkula Bengtson in Bengtson et al., 1990
Type species.—Parkula bounites Bengtson in Bengtson et al., 1990 (p. 223, figs. 149–151); Abadiella huoi Zone, Parara
891
Limestone (lower Cambrian; correlated with the Cambrian Series 2); Kulpara, Yorke Peninsula, South Australia.
Parkula sp. Figure 7.17–7.32
Occurrence.—Poorly preserved internal molds from the Mon- tezuma Range section (M 6); Montezuman Stage. Several inter- nal molds or shells from the Antelope Canyon (AC 1, AC 6), Echo Canyon (E 10, E 12, E 15), Grassy Spring (GS 13, GS 17), Groom Range (GR 5, GR 11), Log Cabin Mine (LC 6, LC 7), Oak Spring Summit (OS 1, OS 4, OS 5, OS 6, OS 6/2, OS 7, OS 11), and Split Mountain (SM 14, SM 15) sections; Dyeran– Delamaran stages.
Description.—Conchs with lenticular cross-section. Dorsal side with faint median ridge. Ventral side less convex than dorsal side. Aperture and apex often incomplete. Most specimens incomplete and 1mm in length (with a maximum of 2.7mm; Fig. 7.21). Angle of divergence 12–20°. Aperture perpendicular to the long axis of the conch. Apex slightly bulbous (Fig. 7.17, 7.19). Surface generally smooth, but a few specimens with faint transverse lines and irregularly spaced depressions of ~6 μmin diameter (Fig. 7.19, 7.25).
Remarks.—Parkula differs from Microcornus by having a faint dorsal median ridge and a lenticular to sub-triangular cross- section. Cross-section is similar to P. esmeraldina Skovsted, 2006a. However, poor preservation and the absence of opercula hinder a certain taxonomic affiliation.
Phylum and class uncertain
Order Hyolithelminthida Fisher, 1962 Family Hyolithellidae Walcott, 1886 Genus Hyolithellus Billings, 1872 (1871)
Type species.—Hyolithes micans Billings, 1872 (p. 215, figs. 3a, 3b); Bonnia-Olenellus Zone, Dyeran Stage; Troy, New York State, USA.
Hyolithellus? sp. Figure 6.24–6.28
Occurrence.—Several fragments of internal molds from the Montezuma Range (M 5) and Indian Springs Canyon (I 2, I 3) sections; Montezuman Stage. Few fragments from the Echo Canyon section (E 12), Grassy Spring (GS 13, GS 17), Groom Range (GR 4, GR 5, GR 11), Indian Springs Canyon (I 12), Log Cabin Mine (LC 6, LC 7), Oak Spring Summit (OS 5, OS 6), and Split Mountain (SM 15) sections; Dyeran Stage. Several fragments from the Antelope Canyon (AC 3),
Figure 5. Molluscs from the Delamar and Combined Metals members of Grassy Spring and Log Cabin Mine sections and from the Emigrant Formation of Split Mountain; Dyeran Stage. (1–13) Anabarella chelata Skovsted, 2006a; scale bar = 200μm; lateral views: (1) FG 544/GB/SM/14/A1-17; (2) FG 544/GB/SM/14/A1- 21; (3) FG 544/GB/SM/14/A1-7; (4) FG 544/GB/SM/14/A1-1; (5) FG 544/GB/SM/14/A1-8; (6) FG 544/GB/SM/14/A1-16; (7) FG 544/GB/SM/14/A1-3; (8)FG 544/GB/SM/15/A2-4; (9) FG 544/GB/SM/14/A1-12; (10) FG 544/GB/SM/14/A1-25; (11) FG 544/GB/SM/15/A2-2; (12) FG 544/GB/SM/14/A1-22; (13)FG 544/ GB/SM/15/B8-1. (14–16) Costipelagiella nevadense Skovsted, 2006a; scale bar = 200μm; lateral views: (14) FG 544/GB/SM/15/B8-7; (15) FG 544/GB/SM/15/ B8-10; (16) FG 544/GB/SM/14/A1-27. (17–22) Pelagiella aff. P. subangulata (Tate, 1892); scale bar = 200μm: (17–19) FG 544/GB/LC/6/A9-11, (17, 18) lateral view, (19) oblique apertural view; (20–22) FG 544/GB/LC/6/A8-26, (20, 21) lateral view, (22) oblique apertural view. (23–32) Microcornus sp.; scale bar = 500μm: (23, 24) FG 544/GB/GS/17/A4-4, (23)dorsal view, (24) oblique view from the aperture; (25, 26) FG 544/GB/GS/17/A4-12, (25)dorsal view, (26) oblique view from the aperture; (27, 28) FG 544/GB/GS/17/A4-10, (27)dorsal view, (28) oblique view from the aperture; (29, 30) FG 544/GB/GS/17/A4-6, (29) dorsal view, (30) oblique view from the aperture; (31, 32) FG 544/GB/GS/17/A5-16, (31)dorsal view, (32) oblique view from the aperture.
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