Wotte and Sundberg—Small shelly fossils from the Great Basin
Remarks.—Spicules show a flat base and an almost radial symmetry. Number and arrangement of the rays indicates a systematic affiliation to Chancelloria.
Genus Archiasterella Sdzuy, 1969
Type species.—Archiasterella pentactina Sdzuy, 1969 (p. 134–137, pl. 15, fig. 4–12, 13?, text figs. 2d, 3, 4); Andalusiana cornuta-Termierella sevillana band (lower Cambrian; middle Marianian Stage; correlated with the upper- most Terreneuvuian/Cambrian Stage 2); basin of Guadalcanal, Sierra Morena, southern Spain.
Archiasterella cf. A. hirundo Bengtson in Bengtson et al., 1990 Figure 8.23
Occurrence.—One spicule from the Log Cabin Mine section (LC 1); Delamaran Stage.
Description.—Spicule with 4+0 rays. Specimen strongly recrystallized.
Remarks.—Configuration and arrangement of rays suggests a similarity with A. hirundo Bengtson in Bengtson et al., 1990.
Phylum Echinodermata Klein, 1734 Indeterminate echinoderm ossicles Figure 8.1–8.8
Occurrence.—Several ossicles from the Echo Canyon (E 12, E 15), Log Cabin Mine (LC 6), and Split Mountain (SM 14, SM 15) sections; Dyeran Stage.
Remarks.—Echinoderm ossicles with preserved stereome micro- structure. Morphology ranges from plates, irregular segments, to barrel-shaped segments, typical for eocrinoids and edrioasteroids. However, no assignment to a particular taxon is possible.
Phylum Tardipolypoda Chen and Zhou, 1997 Class Xenusia Dzik and Krumbiegel, 1989
Order Scleronychophora Hou and Bergström, 1995 Family Eoconchariidae Hao and Shu, 1987
Genus Microdictyon Bengtson, Matthews, and Missarzhevsky in Missarzhevsky and Mambetov, 1981
Type species.—Microdictyon effusum Bengtson, Matthews, and Missarzhevsky in Missarzhevsky and Mambetov, 1981 (p. 78, pl. 13, figs. 3, 5); Rhombocorniculum cancellatum Zone, Geres Member, basal Shabakty Formation (lower Cambrian; upper
895
Atdabanian Stage; correlated with the lower Cambrian Series 2); Ushbas River, Malyi (Lesser) Karatau, Kazakhstan (see Mam- betov and Missarzhevsky, 1972).
Microdictyon montezumaensis new species Figure 8.24–8.25
Holotype.—Specimen FG 544/GB/M/5/C8-8 from sample M 5 from the upper Fallotaspis Zone of the Montenegro Member; middle Montezuman Stage; 5mbelow the 127maluminum tag; Montezuma Range section.
Diagnosis.—Microdictyon with simple, smooth nodes.
Description.—One fragment of ~180 μm thickness (Fig. 8.25). Sclerite composed of a dense crystalline layer (capping, sensu Bengtson et al., 1986) forming its surface and the walls/bases of holes, and a coarser crystalline layer hosting the holes (frame- work, sensu Bengtson et al., 1986). Holes surrounded by a prominent ridge (Fig. 8.24, 8.25). Cross-section of holes clearly shows the relationship between holes and ridges, offering a barrel-shaped structure (Fig. 8.25). At the capping, hole dia- meters constricting from ~80 μm to ~50 μm, extending into bulbous cavities (width of 120 μm in their central part) in the framework. Holes surrounded by six regularly arranged weak nodes (Fig. 8.24, 8.25).
Etymology.—Named after Montezuma Range.
Remarks.—The exact determination of Microdictyon species is primarily based on the morphology of the nodes surrounding the holes. A further aspect is the hole diameter and a common basal closure of the holes. The last feature is a typical characteristic of M. effusum (Bengtson et al., 1986, p. 101, fig. 3). However, the absence of such a basal closure in all other described species of Microdictyonmay be an artifact of
preservation.According to the original description, the nodes of M. effusum have a mushroom- like shape, although this and the basal closure are not observable on the figured material (Bengtson et al. in Missarzhevsky and Mambetov, 1981, pl. 13, figs. 3, 5). Bengtson et al. (1986) described a distinct brim and a sub-centrally placed apex for M. effusum. Nodes of our sclerite show no prominent relief (Fig. 8.24, 8.25). However, the good preservation of the surface layer indicates no or only minor erosion, thus excluding a destruction of prominent nodes. Therefore, the gentlemorphology on the sclerite is considered as representing the original shape. Because the structure of the nodes is an essential criterion for species definition, it is necessary to assign this fragment to the new species M. montezumaensis.
Figure 7. Small shelly fossils from the Delamar, Echo Shale, and Combined Metals members of Echo Canyon, Grassy Spring, Groom Range, and Oak Spring Summit sections; Dyeran Stage. (1–6) Pelagiella aff. P. subangulata (Tate, 1892); scale bar = 200μm: (1–3) FG 544/GB/GS/13/A6-8, (1, 2) lateral view, (3) oblique apertural view; (4–6) FG 544/GB/GR/11/A10-14, (4, 5) lateral view, (6) oblique apertural view. (7–12) Helcionellid gen. and sp. indet. 1; note the fine radial lirae in the apical region: (7, 8) FG 544/GB/OS/3/B2-3; scale bar = 500μm; (7) lateral view, (8) apical view; (9, 10) FG 544/GB/OS/3/B2-5; scale bar = 200μm; (9) lateral view, (10) apical view; (11, 12) FG 544/GB/OS/3/B2-4; scale bar = 500μm; (11) lateral view, (12)apical view. (13–16) Helcionellid gen. and sp. indet. 2; scale bar = 500μm; note the well-developed concentric rugae in the apical region: (13, 14) FG 544/GB/OS/3/B2-8, (13) lateral view, (14) apical view; (15, 16) FG 544/ GB/OS/3/B2-9, (15) lateral view, (16) apical view. (17–32) Parkula sp.; scale bars 400μm except for (25, 26, 31, 32)(200μm): (17, 18) FG 544/GB/GS/13/A6-2, (17) dorsal view, (18) oblique view from the aperture; (19, 20) FG 544/GB/E/12/B6-17, (19) dorsal view, (20) oblique view from the aperture; (21, 22) FG 544/GB/ GS/17/A4-14, (21) dorsal view, (22) oblique view from the aperture; (23, 24) FG 544/GB/GS/17/A5-15, (23) dorsal view, (24) oblique view from the aperture; (25, 26) FG 544/GB/E/12/B6-7, (25) dorsal view, (26) oblique view from the aperture; (27, 28) FG 544/GB/GS/17/A5-16, (27) dorsal view, (28) oblique view from the aperture; (29, 30) FG 544/GB/E/10/A3-5, (29) dorsal view, (30) oblique view from the aperture; (31, 32) FG 544/GB/E/10/A3-2, (31) dorsal view, (32) oblique view from the aperture.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228 |
Page 229 |
Page 230 |
Page 231 |
Page 232 |
Page 233 |
Page 234 |
Page 235 |
Page 236 |
Page 237 |
Page 238
