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Fig. 32 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 32. Phosphatised fragment of presumably hyolithid helen with fibrous internal structure preserved, from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; SMNH X 4665, sample 7/70. A. Plan view on the broader side of the fragment. B. View on the narrower side. C. Enlargement of A. Scale bar 600 μm, except C, 200 μm.

Fig. 15 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 15. Mollusc Enigmaconus? pyramidalis sp. nov., holotype, internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; SMNH Mo 167676, sample 7/70. A. Upper view. B. Close-up of A, scaly texture on internal mould. C. Lateral view. D. View on the pegma-like sub-apical structure. E. Close-up of C. F. View on the side opposite to D. Scale bar 300 μm, except B, E, 60 μm.

Fig. 12. Helcionellid mollusc Leptostega hyperborea Parkhaev, 2005 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 12. Helcionellid mollusc Leptostega hyperborea Parkhaev, 2005 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/70. A. SMNH Mo 167667; lateral (A1), oblique supra-apical (A2), and apertural (A3) views. B. SMNH Mo 167668; lateral (B1) and upper (B2) views. C. SMNH Mo 167669; lateral view. Scale bar 600 μm, except C, 1200 μm.

Fig. 13 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 13. Helcionellid mollusc Pararaconus sp. internal mould from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; SMNH Mo 160421, sample 7/70. A. Lateral view. B. Sub-apical view. C. Close-up of D. D. Polygonal texture on the apical surface of internal mould. E. Upper view. F. Pits on the surface of mould near the aperture. Scale bar: A, B, E, 600 μm; D, 120 μm; C, F, 30 μm.

Fig. 11. Helcionellid mollusc Mackinnonia anabarica Parkhaev, 2005 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 11. Helcionellid mollusc Mackinnonia anabarica Parkhaev, 2005 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/70. A. SMNH Mo 160420; A1, lateral view; A2, close-up of A1, microtexture on the surface of internal mould, detailed. B. SMNH Mo 167665 (see also Fig. 10); lateral view. C. SMNH Mo 160419 (see also Fig. 9C); C1, lateral view; C2, close-up of C1, polygons on the surface of internal mould. Scale bar: 300 μm, except A2, 120 μm; C2, 60 μm.

Fig. 9. Helcionellid mollusc Mackinnonia anabarica Parkhaev, 2005 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 9. Helcionellid mollusc Mackinnonia anabarica Parkhaev, 2005 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/70. A. SMNH Mo 167662; lateral (A 1), sub-apical (A 2), and upper (A 3) views. B. SMNH Mo 167663; lateral (B 1), sub-apical (B 2), upper (B 3), and supra-apical (B 4) views. C. SMNH Mo 160419; supra-apical (C 1), lateral (C 2), sub-apical (C 3), and upper (C 4) views. D. SMNH Mo 167664; supra-apical (D ), upper (D ), lateral (D ), and sub-apical (D ) views. Scale bar 600 μm.

Fig. 8 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 8. Helcionellid mollusc Figurina cf. F. nana (Zhou and Xiao, 1984) internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/70. A. SMNH Mo 167659; upper (A1), lateral (A2), and sub-apical (A3) views; A4, close-up of A1, pits on the surface of internal mould. B. SMNH Mo 167660; upper (B1), sub-apical (B2), lateral (B3, B4) views. Scale bar 600 μm, except A4, 30 μm.

Fig. 5 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 5. Helcionellid mollusc Parailsanella sp. 1 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. SMNH Mo 160415; lateral (A 1), sub-apical (A 2), and upper (A 3) views. B. SMNH Mo 167655; lateral (B 1), sub-apical (B 2), and upper (B 3) views. C. SMNH Mo 167656; lateral (C 1), upper (C 2), and sub-apical (C 3) views. D. SMNH Mo 160416; lateral (D 1), oblique sub-apical D ), and upper (D ) views. Scale bar 600 μm.

Fig. 2 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 2. Derivation of fossiliferous samples (arrows with numbers) and chemostratigraphic correlation of sections 1 and 3 (Malaya Kuonamka River) with sections 6 and 7 (Bol'shaya Kuonamka River). Correlation with carbon isotope features II–VII from stratotypes of south-eastern Siberian Platform (Brasier et al. 1994) according to Kouchinsky et al. (2001). Note that the zero level in all sections corresponds to the water level above which the sections were exposed in 1996. Description of fauna from the lower part of the Emyaksin Formation in complementary outcrops at the Bol'shaya Kuonamka River (below that zero level) will be published elsewhere. Fauna from the overlying Kuonamka Formation is published by Gubanov et al. (2004) and Kouchinsky et al. (2011).

Fig. 6 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 6. Helcionellid mollusc Parailsanella sp. 1 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. SMNH Mo 167656; close-up of Fig. 5C 2; A 1, pits on the surface of internal mould; A 2, close-up of A 1. B. SMNH Mo 160416; close-ups of Fig. 5D; B 1 , lateral view, polygonal texture on the mould; B 2 , polygons, A B close-up of B 1. Scale bar: A 1, 120 μm; A 2 and B 2, 30 μm; B 1, 300 μm. margin and continuous with the pegma-like structure (Figs. 9C, 11C). Remarks.—The surface of the moulds is covered with 10–40 μm wide, blunt tubercles and bears reticulate microornamentation best seen on the convex parts (folds) of the mould. The tubercles tend to be situated in comarginal rows, similar to what occurs in Mellopegma (Vendrasco et al. 2011b). Where concentric folds are developed, the tubercles are concentrated D along their surface. Reticulation is formed by shallow concave C polygons, ca. 20 μm wide. On the surface of concentric folds, the polygons become deeper and more variable in size, with a diameter typically ranging from 2–10 μm (Fig. 10G). The microornamentation flattens out in the subapical area. In addition to the polygonal texture, some specimens of Mackinnonia show imprints of a laminar shell microstructure in the concave bands between folds on the internal mould (Fig. 10C, G). Fig. 7. Helcionellid mollusc Parailsanella sp. 2 internal moulds from low- er Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar As demonstrated by Runnegar (in Bengtson et al. 1990: fig. Uplift, Siberia; SMNH Mo 167658, sample 7/70; lateral (A), sub-apical 159g), the troughs on internal moulds of Mackinnonia corre- (B), and oblique upper (C) views. D. Close-up of A, showing pits on the spond to areas where the shell was thicker, and where the inner surface of internal mould. Scale bar 1200 μm, except D, 300 μm. layer of shell microstructure would be preserved, whereas the

Fig. 1 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 1. Map showing location of sections 1, 3, Malaya Kuonamka River; 6, 7, Bol'shaya Kuonamka River.

Fig. 4 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 4. Helcionellid mollusc Bemella? sp. internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. SMNH Mo 167650; lateral (A1), apertural (A2), and sub-apical (A3) views. B. SMNH Mo 167651; lateral (B1) and upper (B2) views. C. SMNH Mo 167652; apertural (C1), lateral (C2), and sub-apical (C3) views. D. SMNH Mo 167653; D1, close-up of apertural margin in D3; upper (D2) and lateral (D3) views. Scale bar 1200 μm, except D1, 300 μm.

Fig. 3 in An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia

Fig. 3. Helcionellid mollusc Yochelcionella cf. Y. greenlandica Atkins and Peel, 2004 internal moulds from lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. SMNH Mo 160417; lateral (A 1, A5), sub-apical (A 2), upper (A 3), and supra-apical (A 4) views; A 6, polygonal texture on the surface of snorkel mould. B. SMNH Mo 160418; lateral (B 1), sub-apical (B 2), and upper (B 3) views; B 4, enlargement of B 2, with a shallow groove between the snorkel and aperture; B 5, apical part of the mould with tubercles; B 6, close-up of B 5. C. SMNH Mo 167648; lateral (C 1), sub-apical (C ), and upper (C ) views. D. SMNH Mo 167649; lateral view. Scale bar 600 μm, except A , 60 μm; B , 150 μm; B , 300 μm; B , 120 μm.

Fig. 5 in Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

Fig. 5. An early arthropod reconstruction of Isoxys curvirostratus (Vannier and Chen, 2000). The animal was covered by the carapace. The trunk length, which consists of 14 somites varies from 2 to 3 cm in adults. Large stalked eyes and a pair of uniramous prehensile appendages (5 podomeres) bearing stout inner outgrowths protruded anteriorly. The following appendages are biramous and uniform—i.e., a slender endopod with many podomeres and an exopod fringed with many long lamellae.

Fig. 4 in Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

Fig. 4. An early arthropod Isoxys curvirostratus (Vannier and Chen, 2000) from the Lower Cambrian Chengjiang biota, South China. A. JS0008 from Jianshan section; A1, posterior part of an incomplete specimen showing the frontal appendage, exopod, endopod; A2, detailed view of the frontal appendage, showing five podomeres and tooth−like outgrowths; A3, detailed view of exopod and endopod, showing the gill lamellae of exopod and the podomeres of endopod; A4, detailed view of endopod, showing its podomeres. B. EJ0404 from Erjie section; B1, showing the location of the eye stalk, trunk, proximal part of appendages and the outline of endopod; B2, camera−lucida drawing of B1. Abbreviations: as, anterior spine; en, endopod; es, eye stalk; ex, exopod; f1–5, podomeres of the frontal appendage from the distal to proximal; fa, frontal appendage; gl, gill lamellae of exopod; lv, left valve; p1–5, podomeres of endopod from the distal to proximal; pr, proximal part of appendage; rv, right valve; st, striated ornament; ta, trunk appendage; ti, trunk inclusion; 1–7, numbered trunk appendage.

Fig. 3 in Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

Fig. 3. An early arthropod Isoxys curvirostratus (Vannier and Chen, 2000) from the Lower Cambrian Chengjiang biota, South China. A. JS0014 from Jianshan section; A1, specimen showing the striated ornament of the carapace, eye, frontal appendages, exopod and trace of the trunk; A2, detailed view of eye sphere, showing two individual layers, the light external cornea and the dark internal core; A3, camera−lucida drawing of A1; A4, detailed view of frontal appendages, showing the intersegmental membranes, five podomeres and tooth−like outgrowths; A5, the counterpart of JS0014, showing the posterior part of specimen. B. EJ0417 from Erjie section, dorsal view showing the single shield carapace and unsplit base of anterior or posterior spines. Abbreviations: as, anterior spine; co, cornea; ex, exopod; f1–5, podomeres of the frontal appendage from the distal to proximal; fa, frontal appendage; ou, tooth−like outgrowth of the frontal appendage; ps, posterior spine; ru, retinular units; st, striated ornament.

Fig. 1 in Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

Fig. 1. An early arthropod Isoxys curvirostratus (Vannier and Chen, 2000) from the Lower Cambrian Chengjiang biota, South China. A. JS0010 from Jianshan section; A1, showing the outline and the striated ornament of the carapace; A2, detailed view of exopod, showing the gill lamellae; A3, camera−lucida drawing of A1; A4, detailed view of vascular integumental network. B. JS172 from Jianshan section; B1, detailed view of exopod, showing the gill lamellae; B2, showing the striated ornament on the posterior of the carapace and exopod. Abbreviations: as, anterior spine; ex, exopod; fa, frontal appendage; ps, posterior spine; rv, right valve; st, striated ornament; ta, trunk appendage; vn, vascular integumental network.

Fig. 2 in Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

Fig. 2. An early arthropod Isoxys curvirostratus (Vannier and Chen, 2000) from the Lower Cambrian Chengjiang biota, South China from Erjie section (A–C, E) and from Jianshan section (D). A. EJ0423; A1, complete specimen showing the outline of carapace, lamellae of the exopod; A2, camera−lucida drawing of A1. B. EJ0424, showing the eye spheres, frontal appendage, trunk and the traces of trunk appendages. C. EJ0422, immature specimen showing 14 trunk somites. D. JS154; D1, showing eye spheres, the number of the trunk somites and location of appendages; D2, camera−lucida drawing of D1. E. EJ0407; E1, showing the eye sphere and stalk, appendages in relief and the trunk; E2, camera−lucida drawing of E1. Abbreviations: es, eye stalk; ex, exopod; fa, frontal appendage; gl, gill lamellae of exopod; le, lateral eye; pr, proximal part of appendage; ps, posterior spine; te, telson; ti, trunk inclusion; 1–14, numbered trunk appendage.

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Fig. 14 in The Early Cambrian (Botomian) stem group brachiopod Mickwitzia from Northeast Greenland

Fig. 14. Schematic reconstruction of inferred relationships between mantle, shell, pedicle, and the various types of setae in a reconstructed cross−section of a living Mickwitzia cf. occidens Walcott, with enlarged crosssections showing the interpretation of the various types of cylindroid structures penetrating the shell.