768
Journal of Paleontology 91(4):767–780
fossil record (Thompson et al., 2015b). Furthermore, the echi- noids described herein demonstrate that some of the morpho- logical innovations associated with the echinoid crown group were in fact present in numerous stem group taxa in the Permian.
Geologic setting
All specimens were collected from the Lamar Member of the Bell Canyon Formation from the Guadalupe Mountains ofWest Texas. From 1939 to 1968, numerous expeditions were made by G. A. Cooper and others to the Permian outcrops of West Texas. The specimens herein described were collected during those excursions. In the Guadalupe Mountains, a number of micro- fossil taxa have yielded good biostratigraphic control. From the concurrent presence of the conodonts Jinogondolella postserrata (Behnken, 1975) and J. shannoni Wardlaw in Wardlaw and Mei, 1998, the Lamar Member of the Bell Canyon Formation has been determined to be Capitanian in age (Lambert et al., 2002; Lambert, 2006). The transition from the J. postserrata Zone to the J. shannoni Zone takes place within the uppermost Lamar Limestone Member (Lambert et al., 2010), thus indicating a lower Capitanian age (ca. 264 ma) (Henderson et al., 2012). The uppermost Lamar Limestone Member also marks the transition from J. shannoni to J. altudaensis (Kozur, 1992). The presence of both of these faunal transitions allows for relatively precise biostratigraphic control and clarifies the age of the Lamar Limestone Member to lower Capitanian (263–264 Ma). The Lamar Member of the Bell Canyon Formation was
deposited in the Delaware Basin and is spatially located to the southeast of the Guadalupe Mountains and the Capitan Forma- tion. The Lamar Member contains carbonate debris flows transported from the reef edge sediments of the Capitan Formation. The unit displays a wedge-shaped morphology, being over 90m thick near the shelf margin, where allochtho- nous sedimentation from the reefal sediments represented by the Capitan Formation was greatest, and thinning basinward to only about 2m(Babcock, 1977). The Capitan Formation and the Bell Canyon Formation are coeval (Lambert et al., 2010), and merge toward the edge of the Delaware Basin. Close to the basin edge, at the type section of the Reef Trail Member (which overlies the Lamar Limestone Member), the Lamar Limestone Member was described as containing medium to dark gray organic-rich mudstones, and skeletal, peloidal wackestones and packstones with interspersed carbonate debris flows containing silicified fossils (Lambert et al., 2010). Babcock (1977) noted the presence of numerous transported silicified reef fossils infilling channels in the zone proximal to the reef. Proximal to the reef edge, the fauna of the Lamar Limestone Member consists of brachiopods, bryozoans, and crinoids (Babcock, 1977). Cooper and Grant (1972) furthermore noted that the brachiopod fauna in the Lamar was similar to that occurring on the ‘reef slope.’ Of special importance to this paper, silicified echinoid spines and plates have been noted as common in these debris flows (Babcock, 1977, p. 365, fig. 5). Basinward, the Lamar Lime- stone Member thins and is composed primarily of finely laminated mud lacking fossils and bioturbation (Babcock, 1977). The specimens discussed in this study were collected from localitiesUSNM725e, 728p, and 738b near the Guadalupe
Mountains (Cooper and Grant, 1972), which are interpreted as having been deposited near a shelf margin.
Materials and methods
Following their collection, specimens were prepared out of bulk limestone blocks at the USNM by using the hydrochloric acid dissolution method of Cooper and Grant (1972). Observations were made using dissecting microscopes, and specimens were measured using calipers. Silicified fossils are common in the Lamar Limestone (Cooper and Grant, 1972; Babcock, 1977), and all Lamar echinoid specimens discussed in this study are silicified. Fine scale details of plate structure and tuberculation are obscured by silicification, and stereomic microstructure is lacking from the surface of specimens. Cooper and Grant (1972) discussed two types of silicification present among the fossils of the Glass Mountains. One of these preservation types results in a thin coat of silica on the surface of the specimens, which, when treated with acid, protects the calcite on the interior of the plate from disintegration. This is the nonpervasive silicification dis- cussed by Butts and Briggs (2011), and indeed, some echinoid specimens within this fauna are preserved with only a thin layer of silica and thus contain calcitic interiors. The second type of silicification mentioned by Cooper and Grant (1972) is complete replacement, where the entire fossil has been recrystallized to silica. This is also common among the specimens described herein.
Repositories and institutional abbreviations.—Institutional abbreviations for specimen repositories are as follows: USNM = United States National Museum, Washington D. C., USA; MGL = Musée d’Histoire Naturelle de Lille, France; NMS G = National Museum of Scotland, Edinburgh, Scotland; RGM = Naturalis Biodiversity Center, Leiden, The Netherlands.
Systematic paleontology
Terminology and classification follows Smith (1984) and Kroh and Smith (2010). Methodology follows Lewis and Donovan (2007).
Class Echinoidea Leske, 1778 Subclass Cidaroidea Smith, 1984
Family Miocidaridae Durham and Melville, 1957 Type genus.—Miocidaris Döderlein, 1887
Other genera.—Eotiaris Lambert, 1899, Couvelardicidaris Vadet, 1991, Procidaris Pomel, 1883 Genus Eotiaris Lambert, 1899
Type species.—Cidaris keyserlingi Geinitz, 1848, from the Wuchiapingian Zechstein of Germany and England.
Diagnosis.—Miocidarid with small test. Interambulacral plates imbricate adapically. Aureoles confluent only at and below ambitus. Spines with spinules.
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 |
Page 239 |
Page 240 |
Page 241 |
Page 242 |
Page 243 |
Page 244 |
Page 245 |
Page 246 |
Page 247 |
Page 248 |
Page 249 |
Page 250 |
Page 251 |
Page 252 |
Page 253 |
Page 254 |
Page 255 |
Page 256 |
Page 257 |
Page 258 |
Page 259 |
Page 260 |
Page 261 |
Page 262 |
Page 263 |
Page 264 |
Page 265 |
Page 266 |
Page 267 |
Page 268 |
Page 269 |
Page 270 |
Page 271 |
Page 272 |
Page 273 |
Page 274 |
Page 275 |
Page 276 |
Page 277 |
Page 278 |
Page 279 |
Page 280 |
Page 281 |
Page 282 |
Page 283 |
Page 284 |
Page 285 |
Page 286 |
Page 287 |
Page 288
