Futakami and Haggart—early Albian (Early Cretaceous) douvilleiceratid ammonites
Table 3. Dimensions of specimens of Douvilleiceras offarcinatum (White, 1887) from Haida Gwaii, British Columbia
Specimen D H B B/H U U/D NR NT
GSC No. 10709 57.1 22.6 30.1 1.33 19.8 0.35 21 5 All measurements in millimeters.
Description.—The specimen GSC No. 10709 is approximately 57mmin diameter. The specimen has rectiradiate to very gently rursiradiate ribs and lacks intercalated ribs on the outer whorl. Ribs number 21 per whorl. On the outer whorl there are five rows of tubercles on each rib, consisting of three clavate tuber- cles in the ventrolateral region, a bullate or spinose lateral tubercle, and an umbilical tubercle, as shown in Figure 10.5. The medial ventral sulcus is wide.
Dimensions.—See Table 3.
Material.—A single specimen, GSC No. 10709, obtained from a sandy calcareous concretion at GSC Loc. C-304101, Haida Formation.
Occurrence.—This species is known from the upper lower Albian, the mammillatum Zone of the lower part of the Haida Formation in Canada, the Cuchillo Formation in Texas, and Sergipe Province in Brazil.
Remarks.—The morphological characters of this specimen are closely similar to those of the holotype of D. aurarium Anderson (1938, p. 175, pl. 53, fig. 1) from Shasta County, northern California. It is difficult to distinguish D. aurarium from D. offarcinatum (White, 1887) from Brazil, particularly in the mode and number of tubercles on both examples. Our specimen is somewhat similar to D. spiniferum; a distinct difference between them, however, is that our example of D. offarcinatum shows no intermediate tubercle between the lateral and umbilical tubercles, even in the middle growth stage at 57mm in diameter. Because the intermediate tubercles in D. spiniferum are already present on the flanks at this growth stage, the characteristic tuberculation of this specimen thus appears to fall outside the range of variation of D. spiniferum.
Douvilleiceras scabrosum Casey, 1962 Figures 10.1, 10.2, 11
? 1841 Ammonites mammillaris;d’Orbigny, p. 249, pl. 72, fig. 5.
1962 Douvilleiceras scabrosum; Casey, p. 278, pl. 40, figs. 1–3, pl. 42, figs. 2a-b, text-figs. 102f, 103i.
Types.—The holotype, BM C69861, illustrated by Casey (1962, pl. 40, figs. 1a-b, text-fig. 102f), from Folkstone Beds, mammillatum Zone Bed, Chrismill Bridge (M20 Motorway), Eyhorne Street, Kent (Coll. H. G. Owen); paratypes GSM 107909 (Casey, 1962, pl. 40, figs. 2a-b), GSM 70424 (Casey, 1962, pl. 40, figs. 3a-b, text-fig. 103i), GSM 107913 (Casey, 1962, pl. 42, figs. 2a-b), Folkestone Beds, main mammillatum
1972 Douvilleiceras sp. a; McLearn, p. 67, pl. 12, figs. 1A, B.
53
Table 4. Dimensions of specimens of Douvilleiceras scabrosum Casey, 1962 from Haida Gwaii, British Columbia
Specimen GSC No. 21241* 139.0 54.8 -
D H B B/H U U/D NR NT - 46.5 0.33 38 7 +1**
Notes All measurements in millimeters. *Measurements taken from plaster cast. **Indicating an additional row on each side of the venter.
bed, Copt Point, Folkestone, Kent (Coll. R. Casey), GSM Zn940 from the Folkestone Beds, the puzosianus Subzone, Sandling Junction, and BM C54304 from Machéroménil, Ardennes.
Dimensions.—See Table 4.
Material.—A single specimen, GSC No. 21241, described and illustrated by McLearn (1972, p. 67, pl. 12, figs. 1A-B; illustrated herein in Fig. 10.1, 2) as Douvilleiceras sp. a, is from GSC Loc. 7594.
Occurrence.—This species is known from the mammillatum Zone of the lower part of the Haida Formation in Canada and the Lower Greensand of southern England and France.
Remarks.—This specimen was identified by McLearn (1972, p. 67, pl. 12, figs. 1A-B) as Douvilleiceras sp. a. McLearn described the features of this specimen, giving comparisons with two other species of Douvilleiceras, D. spiniferum and D. scabrosum. McLearn concluded that the specimen either represents an extreme variant of D. spiniferum or a new species. We re-examined the specimen GSC No. 21241. The ribs are unequal in strength and rarely intercalated on the outer whorl. The tuberculation is represented by four distinct clavate tubercles in the ventrolateral region, a strong lateral spinose tubercle, a faint intermediate node-like tubercle, and a bullate umbilical one (Fig. 11.1). Based on the composition of these tubercles, this specimen falls distinctly outside of the range of variation of D. spiniferum. The morphological features of this specimen, particularly
the mode of tuberculation, the number of rows of tubercles on each side, and the mode of ribbing, are closely similar to those of the paratype of D. scabrosum Casey, GSM 107909 (Casey, 1962, p. 278, pl. 40, figs. 2a-b), from the mammillatum Zone of England. The Canadian specimen has somewhat weaker ribs than the paratype of D. scabrosum, and the initial appearance of the intermediate tubercles in this specimen is somewhat later than in the holotype and paratypes of D. scabrosum. It does appear, however, to fall within the relatively wide variation of D. scabrosum. According to Casey (1962, p. 278), D. scabrosum differs from D. mammillatum in having irregular and coarse ribbing and a wide ventral sulcus. In addition, the number of rows of tubercles on each side is seven, although the holotype specimen exhibits an additional row
of tubercles on each side of the venter (Casey, 1962, p. 285, text- fig. 102f).
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
