Fig. 4 in Muscle attachment scars in helcionelloids from Denmark cast light on mollusc evolution in the Cambrian

Fig. 4. Helcionelloid mollusc Eotebenna danica sp. nov., internal moulds, Andrarum Limestone, Bornholm, Denmark, Guzhangian, Miaolingian, middle Cambrian. A. MGUH 34277, lateral view (A1) with rectangles indicating location of Fig. 5B1, B2, and B3. Muscle scars at apex illustrated in different orientations (A2–A6), with arrow in A2 indicating slight diagenetic compression or deformation along edge of muscle field. Arrow in A3 indicating imbricated lamellar structure shown in detail in A4. B. MGUH 34278, apex in lateral view. C. MGUH 34279, lateral view. D. MGUH 34280, holotype, lateral (D1) and apico-lateral (D2) views, the latter showing the laterally compressed shell form, with detail of apical muscle scars (D3). E. MGUH 34281, lateral view. F. MGUH 34282, apex in lateral view. pontifex Runnegar and Jell, 1976, from the Currant Bush southern Freuchen Land, North Greenland is more strongly Limestone (Miaolingian) of Queensland, Australia, is also coiled than Eotebenna danica, with a convex supra-apical much more elongate than Eotebenna danica but the massive surface, in lateral view, and the apex strongly overhanging snorkel is circular in cross-section compared to the inverted the sub-apical surface (Peel 1989, 1991b). teardrop-shape in the two Bornholm species. Eotebenna arctica Peel, 1989, from the Henson Gletscher Stratigraphic and geographic range.—Drumian of Sweden Formation (uppermost Series 2, Stage 4, lower Cambrian) of and Guzhangian of Denmark (both middle Cambrian).图4 太阳女神螺类软体动物（Helcionelloid mollusc）新种丹麦始梯螺（Eotebenna danica sp. nov.）的内模标本，产自丹麦博恩霍尔姆岛安达鲁姆灰岩（Andrarum Limestone），时代为寒武纪中期苗岭统（Miaolingian）古丈阶（Guzhangian）。 A. 标本编号MGUH 34277，侧视图（A1），图中方框标注了图5B1、B2及B3的对应位置。壳顶处的肌痕以不同方位展示（A2~A6）：A2中的箭头指示肌痕区域边缘存在轻微成岩压实或变形；A3中的箭头指示叠覆板状结构，其细节见图A4。 B. 标本编号MGUH 34278，壳顶侧视图。 C. 标本编号MGUH 34279，侧视图。 D. 正模标本（holotype）MGUH 34280，分别为侧视图（D1）与壳顶侧视图（D2），后者展示了侧扁的壳体形态，并显示壳顶肌痕细节（D3）。 E. 标本编号MGUH 34281，侧视图。 F. 标本编号MGUH 34282，壳顶侧视图。 产自北格陵兰弗赖申兰南部柯兰特布什（Currant Bush）以及澳大利亚昆士兰州苗岭统灰岩的教皇螺属（Pontifex）Runnegar & Jell, 1976，其壳体卷绕程度较丹麦始梯螺更强，侧视可见凸形的壳顶上方表面，且壳顶强烈悬覆于亚壳顶表面（Peel, 1989, 1991b）。该类群体型远较丹麦始梯螺更为修长，但其粗壮的出水管（snorkel）横截面呈圆形，而博恩霍尔姆岛的两个该属物种的出水管则呈倒泪滴形。 北极始梯螺（Eotebenna arctica Peel, 1989）发现于瑞典亨森冰川组（下寒武统统2顶部，第4阶）以及丹麦古丈阶地层，二者均属于寒武纪中期。 地层与地理分布：瑞典德鲁姆阶（Drumian）与丹麦古丈阶（均为寒武纪中期）。