498
Journal of Paleontology 92(3):488–505
Holotype.—CMCIP 76789, holotype; CMCIP 76790, paratype; UMMP 74681.2, paratype.
Diagnosis.—Cleiocrinus with medium conical to bowl-shaped calyx; sutural pores few, positioned along plate sutures to either side of each plate corner; plates ornamented withfine pitting; median ray ridges narrow, rounded; 20 free arms; abundant fixed pinnules.
Occurrence.—The occurrences documented here are from the middle–upper Bobcaygeon Formation, Kirkfield Quarry, Upper Ordovician (lower Katian) and from the Bobcaygeon–Verulam contact zone, LaFarge Quarry, UpperOrdovician (lowerKatian).
Description.—Calyx medium cone with bowl-shaped base, as high as wide; plates ornamented with fine pitting; median ray ridges narrow, rounded. Upper and lower margins of fixed brachial plates undulatory, medial portion of distal margin deflected downward; distal plate margins slightly elevated from the calyx surface and appearing to overlap the plates above, giving the appearance of weak imbrication. Sutural pores positioned along plate sutures, relatively
large in size compared to other species, typically eight per plate, positioned to either side of each plate corner; pores more closely spaced in more distal plates. Infrabasals not observed; infrabasal circlet probably
confined to basal concavity and overlapped by higher circlet as is typical in other Cleiocrinus species. Basals and radials arranged in a single circlet of 10 plates.
Basals small, pentagonal, higher than wide, with angled surface directed upwards. Radials slightly smaller than basals, rectangular as known, wider than high. Rays comprised of numerous fixed brachials that are fused
laterally; interray plates absent. Posterior interray imperfectly preserved, articulation with CD basal not observed; middle to higher portion of posterior interray forming an anal series comprised of a single column of wide, low plates; anal series plates four to five times wider than high, upper and lower margins strongly undulatory and similar in shape to the patelloid process of flexible crinoids. Anal series ornamented by a broad, protruding anitaxial ridge. Primibrachials two; first primibrachial roughly hexagonal,
largest plate in calyx, more than twice as wide as high, resting on underlying radial and sloping upper margins of adjacent basals; second primibrachial axillary, wider than high. Secundibra- chials three in preserved rays, third axillary, all secundibrachials approximately twice as wide as high. Tertibrachials four to six, bifurcating at different positions within rays, dimensions becoming more equant distally, but still wider than high throughout. Quartibrachials variable in number, giving rise to one arm and two large fixed pinnules per quarter ray; 20 free arms and 40 large fixed pinnules in total; higher quartibrachials giving rise to additional, smaller fixed pinnules that grade into
free pinnules. Undulatory pattern of plate margins becoming increasingly exaggerated in higher fixed brachials. Arm openings 20; two large fixed pinnules positioned
between each arm, 40 large fixed pinnules in total. Brachials weakly cuneate uniserial, pinnulate. Stem obtusely pentagonal with rounded margins; lumen
large, diameter ~60% stem diameter. Proximal to medial stem heteromorphic, N212; nudinodals moderately thick with smooth, rounded latera, priminternodals slightly thinner and with smaller diameter than the first; internodals very thin, not visible in side view, entirely overlapped by nudinodals, comprised of five narrow petal-like arcuate segments that are only marginally in lateral contact. Distal column, holdfast, distal arms, and tegmen unknown.
Etymology.—The specific name lepidotus is derived from the Greek lepidotós, meaning scaly, in reference to the scale-like appearance of the calyx plates.
Materials.—CMCIP 76789, holotype (middle–upper Bobcay- geon Formation, Kirkfield Quarry); CMCIP 76790, paratype (middle–upper Bobcaygeon Formation, Kirkfield Quarry); UMMP 74681.2, paratype (Bobcaygeon-Verulam contact zone, LaFarge Quarry).
Remarks.—Cleiocrinus lepidotus n. sp. is most similar to C. perforatus but differs from this and all other species of Cleiocrinus on the basis of its plate ornamentation, the number and arrangement of sutural pores, and the condition of the posterior interray. Whereas C. lepidotus n. sp. is ornamented with fine pitting, other Cleiocrinus species are unornamented (C. perforatus) or have a variety of ridges arranged in radiating, concentric, and/or rhombic patterns (all other species). Among species of Cleiocrinus, sutural pore number and arrangement ranges from several large pores along each plate margin (C. perforatus) to small elongated slits (C. laevis) to many small, closely spaced circular pores (all other species). In con- trast, C. lepidotus n. sp. has few, relatively large sutural pores (typically two per plate margin) that are positioned to either side of each plate corner. In addition, in many species of Cleiocrinus, the external plate sutures converge into larger pores before reaching the inner surface of the plate (e.g., C. regius, C. bromidensis). The large pores of C. lepidotus n. sp. appear to penetrate the calyx directly and do not converge, a character apparently shared with C. perforatus. Finally, all species of Cleiocrinus for which the posterior is known have a posterior interray that is not in contact with the tegmen, whereas the posterior of C. lepidotus n. sp. is in contact with the tegmen.
Cleiocrinus sp. Figure 4.6
Figure 6. Cleiocrinus lepidotus n. sp. from southern Ontario. (1, 5–8) CMCIP 76789, holotype (middle–upper Bobcaygeon Fm., Kirkfield Quarry); (1) lateral view of partial crown and stem, posterior interray indicated by arrow; (5) lateral view of partial crown, opposite side; (6) radial/basal circlet showing radial plate (center), wide fixed primibrachials, and adjacent basals; (7) proximal (upper) stem articular facet, photographed under alcohol; (8) distal (lower) stem articular facet, photographed under alcohol; (2, 3, 9–11) CMCIP 76790, paratype (middle–upper Bobcaygeon Fm., Kirkfield Quarry); (2) lateral view of distal calyx and arm bases; (3) posterior view of partial calyx; (9) close-up of fixed brachial plates showing pitted ornamentation; (10) closeup of fixed brachial plates showing sutural pores adjacent to plate corners, photographed under alcohol; (11) close-up of posterior interray; (4) UMMP 74681.2, paratype (Bobcaygeon-Verulam contact zone, LaFarge Quarry), lateral view of small partial calyx. All scale bars 5mm unless otherwise indicated.
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
