Futakami and Haggart—early Albian (Early Cretaceous) douvilleiceratid ammonites
49
Table 2. Dimensions of specimens of Douvilleiceras spiniferum (Whiteaves, 1876) from Haida Gwaii, British Columbia
Specimen
GSC No. 10658 (110) 45.3 60.4 GSC No. 10659 (126) 51.0 - GSC No. 10660 75.6 29.5 41.6 GSC No. 10661 (66.2) 20.4 35.3 GSC No. 10662 -
27.3 -
GSC No. 10663 64.0 26.3 37.8 GSC No. 10664 37.3 15.1 - GSC No. 10665 25.8 10.7 - GSC No. 10666 -
GSC No. 10667 60.1 24.8 (29.2) (1.18) 20.4 0.34 21 6 GSC No. 10668 50.7 21.7 29.0 GSC No. 10669 47.9 18.1 30.0 GSC No. 10670 48.3 21.2 28.8 GSC No. 10671 44.3 17.9 26.8
26.7 -
8.5 0.33 - - -
-
GSC No. 10672 44.8 (17.7) (29.2) (1.65) 14.9 0.33 21 6 GSC No. 10673 49.0 20.3 29.2
GSC No. 10674 43.6 17.5 (11.6x2) (1.33) 14.5 0.33 20 5 GSC No. 10675 45.6 18.9 27.8 GSC No. 10676 -
18.5 (27.0) (1.46) 15.7 -
GSC No. 10677 32.0 11.5 20.4 GSC No. 10678 36.1 15.1 19.1 GSC No. 10679 36.5 14.3 23.0 GSC No. 10680 34.4 14.1 18.5 GSC No. 10681 32.0 12.2 18.8 GSC No. 10682 29.6 10.9 18.1
D H B B/H U U/D NR NT 1.33 36.3 (0.33) 22x2 6
- - 10x2 6
- 41.3 0.33 31 7 1.41 27.7 0.37 24 6 1.73 24.8 (0.37) 13x2 6 +1* -
1.44 21.4 0.33 18 6 - 12.7 0.34 18 5 - -
1.34 17.1 0.34 18 5 1.66 16.2 0.34 22 6 1.36 14.9 0.31 20 6 1.50 13.5 0.30 16 6
1.44 15.0 0.31 18 6 1.47 15.0 0.33 21 6 1.77 11.6 0.36 18 5
1.26 11.3 0.31 18 5 1.61 12.1 0.33 24 5 1.31 10.6 0.31 23 5 1.54 11.8 0.37 17 5 1.66 10.4 0.34 20 5
GSC No. 10683 (38.7) (14.5) (27.5) (1.90) 13.6 (0.35) - 5 GSC No. 10684 28.3 9.9 19.2 GSC No. 10685 (28.6) 11.8 18.6
Figure 5. (1) Shell ornamentation of Douvilleiceras spiniferum (Whiteaves) in early growth stage. GSC No. 10708, GSC Loc. C-300855. NC = primary constriction. (2, 3) Ontogenetic changes in the whorl section of Douvilleiceras spiniferum (Whiteaves) in (2) early growth stage (GSC No. 10708, GSC Loc. C-300855), and (3) early to middle growth stage (GSC No. 10711, GSC Loc. 48572).
Dimensions.—See Table 2.
Variation.—Douvilleiceras spiniferum from Maude Island exhibits a verywide range ofmorphological variation, particularly in the number and mode of tubercles, and the shape of the whorl section. The species is generally characterized by six rows of tubercles on each flank, and occasionally seven at diameters greater than approximately 60mm (Fig. 8). As pointed out by McLearn (1972, p. 65), the appearance of an additional row of tubercles immediately adjacent to the first ventrolateral tubercles on either side, or rarely both sides, of the venter is rare, but noted. If this additional row becomes as large as the first ventrolateral tubercles, it becomes difficult to distinguish D. spiniferum from some European species, such as D. mammillatum (Schlotheim) and D. leightonense Casey. A rare example from Maude Island, GSC No. 10706 (Fig. 9.1, 9.2), shows nine rows of tubercles on each rib at 110mm diameter; these rows are composed of fairly faint, node-like tubercles, and are not clavate on the ventrolateral part. This specimen shows typical features of D. spiniferum on the inner whorl, however: it has three rows of tubercles in the ventrolateral region at about 55mmdiameter. The specimen GSC No. 10704 has six rows of tubercles at 26.3mm diameter and is the smallest example in our material showing six rows
of tubercles. GSC No. 5014b, the lectotype of D. spiniferum figured by McLearn (1972, pl. 11, figs. 1A–C; Fig. 4 herein), is unique in his material. This specimen shows different extent of tuberculation on each side: there are seven rows of tubercles on the right side of the shell, but only six rows on the left side (Fig. 8.4). This specimen appears to represent an intermediate
GSC No. 10686 24.4 10.4 (15.0) (1.44) 6.7 0.27 18 4 GSC No. 10687 28.8 11.3 (10.0x2) (1.77) 9.1 0.32 20 4 GSC No. 10688 (20.0) (7.7) 12.7 (1.65) 6.6 (0.33) - 4 GSC No. 10689 24.7 10.3 (13.8) (1.34) 7.8 0.32 (14) 4 GSC No. 10690 24.3 (12.0) - GSC No. 10691 13.0 5.2 7.9 GSC No. 10692 22.2 8.6 14.3 GSC No. 10693 23.9 9.2 14.9 GSC No. 10694 22.4 9.6 14.1 GSC No. 10695 21.5 9.2 13.5 GSC No. 10696 18.8 7.4 12.9 GSC No. 10697 20.3 9.3 11.8 GSC No. 10698 18.4 7.3 13.2 GSC No. 10699 18.0 7.8 11.7 GSC No. 10700 19.3 7.9 12.0 GSC No. 10701 20.1 8.4 13.3
1.52 4.3 0.33 - - 1.66 7.4 0.33 17 4 1.62 7.8 0.33 22 4 1.47 6.7 0.30 13 5 1.47 6.7 0.31 17 4 1.74 6.2 0.33 (16) 4 1.27 6.2 0.31 16 4 1.81 5.4 0.29 14 4 1.50 5.9 0.33 14 4 1.52 6.4 0.33 17 4 1.58 6.6 0.33 14 -
- 7.4 0.30 - -
GSC No. 10702 19.5 8.6 (12.2) (1.42) 5.8 0.30 - 4 GSC No. 10703 34.0 14.4 21.0 GSC No. 10704 26.3 13.3 17.1 GSC No. 10705 -
15.4 23.3 -
GSC No. 10706 (115.6) 51.3 (55.6) (1.08) 33.4 (0.29) 36 9 GSC No. 10707 (127.0) (53.1) - GSC No. 10708 19.1 7.4 13.4
All measurements in millimeters. Measurements in parentheses are approximate. *Indicating an additional row on each side of the venter.
morphological form between American D. spiniferum and European D. leightonense. Such difference in ornamentation between the right and left sides of the shell, seen as a rare example inD. spiniferum, is noted occasionally in other ornate ammonites, for example Lyelliceras ulrichi Knechtel from the middle Albian (Obata et al., 1975). Regarding the mode of tuberculation, the present species
is characterized by strong tubercles on each rib, compared with D. mammillatum discussed above. Several interesting specimens in ourmaterial, includingGSC No. 10662 andGSC No. 10747, have extremely strong ventrolateral tubercles and coarse ribs in the middle growth stage (D ≈ 40–50mm) (Figs. 6.12–6.14, 8.1). These ventrolateral tubercles are massive and form spiral ridges. In addition, the ventral sulcus is wide and deep, but not U-shaped in outline. These specimens appear to resemble a specimen of
1.46 10.9 0.32 - 5 1.29 9.1 0.35 - 6 1.51 -
- 40.0 (0.31) (39) - 1.81 6.5 0.34 17 4
- 6
1.94 10.0 0.35 16 5 1.58 9.9 (0.35) 15 5
18 6
- 5
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
