Zachos—Paleocene echinoids
that this species could be assigned to Schizaster rather than Linthia, but the structure of the apical disc is unlike that typically seen in Schizaster, and consideration of reassignment will require further study and evaluation of other related species. Most morphological details of the type of Linthia
maverickensis are obscured by matrix, but it does not differ substantially from other small specimens of L. alabamensis and on this basis the synonymy with L. alabamensis by Cooke (1942) is justified. Isolated occurrences of specimens substan- tially smaller than the type of L. alabamensis are found in Texas, Mississippi, and Alabama. Several lots in the UF collection, totaling several hundred specimens, were collected from the Pine Barren Member at the base of the Clayton Formation (early Danian) on Mussel Creek, Lowndes County, Alabama. The specimens range from 11–15mm in length and are juveniles based on the poor development of the anterior sulcus, low total pore count in the petals, and reduced numbers of hydropores in the madreporite (Fig. 11.2–11.4), but all have fully developed genital pores and were apparently sexually mature. They are, in fact, very similar to specimens of L. variabilis (Slocum, 1909) collected from the Ripley Formation (Maastrichtian) at Pontotoc, Mississippi, although lacking the small tubercles or beads in the anterior ambulacrum characteristic of L. variabilis, and with more widely divergent petals. The in situ occurrence of these small L. alabamensis just above the Cretaceous/ Paleogene boundary suggests progenetic maturity in a popula- tion representing a recovery fauna. Smith and Jeffery (2000) placed this species in synonymy
with Paraster sindensis (Duncan and Sladen, 1882). The drawings in the original description are of little value in a comparison of the species, although the drawing of the plates of the apical disc indicates a similarly deep insertion of ocular plate III and occlusion of interambulacral plates 2b and 3a. The location of the holotype is not known but may be in the Duncan and Sladen collections of the Indian Museum, Kolkata. The specimen of P. sindensis figured by Jagt (2000) differs from L. alabamensis in the relative lengths of the petals, the deeper and narrower anterior sulcus, and the much less inflated outline and lack of shoulders in the posterior interambulacra.
Linthia tumidula Clark, 1891 Figures 9.10–9.12, 12.1, 12.4
1891 Linthia tumidula Clark, p. 77. 1893 Linthia tumidula; Clark, p. 91. 1907 Linthia tumidula; Weller, p. 304, pl. 18, figs. 1–9. 1915 Linthia tumidula; Clark in Clark and Twitchell, p. 99, pl. 53, figs. 1a–i.
1942 Schizaster (Linthia) tumidulus; Cooke, p. 41.
Types.—Lectotype AMNH 8954, from the Vincentown Formation, Vincentown, New Jersey. No holotype was designated by Clark (1891) or in any subsequent publications. Other cotypes indicated by Clark (in Clark and Twitchell, 1915) as residing in the Boston Society of Natural History and Johns Hopkins University collections are now missing.
Description.—Test oval to slightly cordiform, narrow anterior sulcus; base relatively flat, test tall, apex posterior of apical disc.
1019
Apical disc ethmolytic, four equal-sized genital pores. Petals depressed, narrow, anterior pair longer than posterior and extending nearly to margin; pores conjugate, oval, nearly equal-sized. Anterior ambulacrum depressed, narrow; pores in two single series, individual pore pairs inset, separated by faint stereom wall. Anterior petals widely diverging 150°, posterior pair narrowly diverging 40°. Surface covered by fine primary tuberculation, tubercles larger on margin and oral surface, oral posterior ambulacra naked. Peristome transverse, reniform, lipped. Periproct small, oval, marginal, not visible from above. Peripetalous fasciole passes at tip of anterior petals and forms a distinct zig-zag pattern in the posterior paired interambulacra, meeting lateral fasciole such that the three shared angles all approach 120°.
Additional material.—USNM488624, USNM 488772, USNM 540913, USNM 636364, all from the Vincentown Formation, Vincentown, New Jersey.
Occurrence.—Vincentown Formation, Vincentown, New Jersey (exact locality unknown).
Remarks.—Description expanded based on new material from New Jersey. Clark (in Clark and Twitchell, 1915) listed specimens in the American Museum of Natural History, the Boston Society of Natural History, and Johns Hopkins University. The AMNH has a specimen listed as a syntype and this is hereby designated as the lectotype. The Harvard Museum of Comparative Zoology, which received much of the Boston Society material, lists three specimens in the catalog (HMCZ IPEC-3941), but these were reportedly collected from Alabama, and are now lost. The Johns Hopkins collection was moved to the Smithsonian, but Cooke (1942) stated that no specimens were found in the NMNH collections, and that the type was in the AMNH. It was not included in the list of species from the Vincentown in Cooke (1959), but several previously unidentified specimens have been found in the collection. According to specimen labels, all of these were collected long after Clark’s description of the species.
Linthia prima (Cooke, 1942) Figure 12.7, 12.10–12.14
1942 Eupatagus?(Brissopatagus?) primus Cooke, p. 59, pl. 4, figs. 1–4.
1959 Linthia? prima; Cooke, p. 70, pl. 43, figs. 1–4. 2000 Linthia? prima; Smith and Jeffery, p. 335.
Type.—Holotype USNM 498978, from the Clayton Formation, 5 miles south of Ellaville, Schley County, Georgia.
Description.—Test cordate, medium size, upper surface high, posterior paired interambulacra form distinct shoulder near apex; oral surface relatively flat with slight posterior keel, margins sharply
rounded.Broad, relatively deep anterior sulcus, indenting anterior margin. Apical disc nearly central, ethmolytic, four genital pores. Petals straight, in deep, broad depressions; anterior pair longer than posterior pair, anterior pair diverge at 120º–140º, posterior pair diverge at 60º. Pore pairs in anterior ambulacrum
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
