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Fig. 16 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 16. Paterinid brachiopod Pelmanotreta neguertchenensis (Pelman, 1977) from the lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Siberia, Russia; sample 7/27.5. A–E. Dorsal valves, SMNH Br151254–151258, respectively. A2,close-up of the brephic shell. Scale bar: 1 mm (A1, C–E) and 250 µm (A2, B).

Fig. 15 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 15. Lingulid brachiopod Acrothele olenekensis Pelman in Pelman and Pereladov, 1986 from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol'shaya Kuonamka rivers, Siberia, Russia; samples 1/22 (A, B, D), K1/17B (C), and 8/18.5 (E). A, B, D. Ventral valves, SMNH Br151249– 151251, respectively. A2, A3, close-ups showing brephic shell; D2, enlargement showing pits on the surface of brephic shell. C, E. Dorsal valves, SMNH Br151252 and 151253, respectively. E, dorsal valve of the brephic shell. Scale bar: 1 mm (A1, C, D1), 500 µm (B), 250 µm (A2, A3, E), and 25 µm (D2).

Fig. 1. Locality maps. A in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 1. Locality maps. A. Map of the Siberian Platform. B. Khorbusuonka River. Localities referred to in the main text: 96-1, 96-2, 96-3, Malaya Kuonamka (MK) and 96-6, 96-7, 96-8, Bol'shaya Kuonamka (BK) rivers, eastern flank of the Anabar Uplift; 3, 11, 15, 19, 20, Khorbusuonka River, Olenyok Uplift; 21, 22, Lena River lower reaches, Ulakhan-Ald'yarkhay Brook; Le, Lena River middle reaches, Tiktirikteekh and Bydyangaya Brooks; Al, Aldan River, between sections "Dvortsy" and UlakhanSulugur. Margin of the Siberian Platform is shown by a dashed line in A.

Fig. 14 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 14. Lingulid brachiopod Botsfordia caelata (Hall, 1847) from the Cambrian Emyaksin (F, G) and Kuonamka (A–E, H, I) formations, Malaya Kuonamka and Bol'shaya Kuonamka rivers, Siberia, Russia; samples K1/7B (A, B, H) and 1/9 (C–E, I) and 7/70 (F, G). A, B, F. Ventral valves, SMNH Br151240–151242, respectively. A1, A3, B2, close-ups showing brephic shell. C, D, G–I. Ventral valves, SMNH Br151243–151247, respectively. D2, enlargement showing brephic shell. E. Deformed specimen with both valves preserved, SMNH Br151248, view on the ventral valve. Scale bar: 1 mm (A2, B1, C, D1, E–I) and 250 µm (A1, A3, B2, D2).

Fig. 11 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 11. Lingulid brachiopod Homotreta cf. gorjanskii (Pelman, 1973) from the middle Cambrian Olenyok Formation, Malaya Kuonamka River, Siberia, Russia; sample 2/10. A–E. Ventral valves, SMNH Br151212–151216, respectively. A2, close-up of brephic shell, A3, enlargement showing pitted surface; E1, lateral view; E2, posterior view. F–K. Dorsal valves, SMNH Br151217–151222, respectively. G, brephic shell. Scale bar: 250 µm (A1, B–F, H–K), 125 µm (A3, G), and 12.5 µm (A2).

Fig. 7 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 7. Lingulid brachiopod Eoobolus variabilis (Pelman, 1977) from the Cambrian Emyaksin Formation, Bol'shaya Kuonamka River (A–C), Erkeket Formation, Khorbusuonka River (D–F), and Kuonamka Formation, Malaya Kuonamka River (G), Siberia, Russia; sample 7/70 (A–C), samples 19/4B, 19/66.5, 19/10.25 (D–F, respectively), and sample K1/7B (G). A, B. Ventral valves, SMNH Br151190 and 151191, respectively. C, D, F, G. Dorsal valves, SMNH Br151193–151196, respectively. F2, close-up showing brephic shell. E. Specimen with both valves preserved, view on the dorsal valve, SMNH Br151192. Scale bar: 1 mm (A–E, G), 500 µm (F1), 100 µm (F2).

Fig. 10 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 10. Lingulid brachiopod Homotreta gorjanskii (Pelman, 1973), SMNH Br151211, from the middle Cambrian Kuonamka Formation, Malaya Kuonamka River, Siberia, Russia; sample 1/28. A1, dorsal valve; A2, close-up of A1; A3, A4, enlargements of anterior margin with mantle canals. Scale bar: 500 µm (A1), 125 µm (A2), 60 µm (A3), 17 µm (A4).

Fig. 13 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 13. Lingulid brachiopod Linnarssonia bulcurica Pelman in Pelman and Pereladov, 1986 from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol'shaya Kuonamka rivers, Siberia, Russia; sample 1/16.5 (A–D, F, G) and sample 8/32 (E). A–C. Ventral valves, SMNH Br151233– 151235, respectively. A1, external surface; A2, lateral view; A3, close-up showing brephic shell. D, F, G. Dorsal valves, SMNH Br151237–151239, respectively. D2, close-up of the brephic shell; D3, enlargement with pits on the surface. E. Specimen with both valves preserved, SMNH Br151236. E1, external surface; E2, oblique lateral view. Scale bar: 1 mm (A1, A2, B, C, D1, E, F), 500 µm (G), 250 µm (A3, D2), and 12.5 µm (D3).

Fig. 9 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 9. Lingulid brachiopod Homotreta gorjanskii (Pelman, 1973) from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol'shaya Kuonamka rivers, Siberia, Russia; samples 8/22.5 (A), 8/23.1 (B, D), 8/18.5 (C, E), and 1/28 (F). A–F. Dorsal valves, SMNH Br151205–151210, respectively. F2, close-up showing brephic shell; F3, F4, enlargements with pits on the surface. Scale bar: 1 mm (A–D), 500 µm (F1), 250 µm (E), 60 µm (F2), 8 µm (F4), and 2.5 µm (F3).

Fig. 12 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 12. Lingulid brachiopod Homotreta aff. gorjanskii (Pelman, 1973) from the middle Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; sample 19/92. A. Specimen with both valves preserved, SMNH Br151223. A1, posterior view; A2, lateral view. B, D, E, I. Ventral valves, SMNH Br151224– 151227, respectively. I1, oblique posterior view, I2, inner surface. C, F–H, J. Dorsal valves, SMNH Br151228–151232, respectively. H1, inner surface; H2, oblique inner view; J2, close-up showing brephic shell. Scale bar: 500 µm (A–E, G, H, I1, J1), 250 µm (F, I2), and 60 µm (J2).

Fig. 8 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 8. Lingulid brachiopod Homotreta gorjanskii (Pelman, 1973) from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol'shaya Kuonamka rivers, Siberia, Russia; samples 1/28 (A, B) and 1/22 (H) and samples 8/14.8 (C, D), 8/18.5 (F), and 8/23.1 (E, G). A–D. Specimens with both valves preserved, SMNH Br151197–151200, respectively. A1, B1, lateral; A2, B3, D1, posterior; and B2, ventral views; C, D2, view on the ventral valve showing brephic shell. E–G. Ventral valves, SMNH Br151201–151203, respectively. H. Ventral valves, SMNH Br151204, sagittal cross-section showing lamination. Scale bar: 1 mm (E–G), 500 µm (H), 250 µm (A, B, D1), 125 µm (C), 60 µm (D2).

Fig. 6 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 6. Lingulid brachiopod Eoobolus variabilis (Pelman, 1977) from the middle Cambrian Kuonamka Formation, Bol'shaya Kuonamka River, Siberia, Russia, sample 8/23.1. A, B, D. Dorsal valves, SMNH Br151184–151186, respectively. A2, A3, close-ups of tuberculate surface. C. Ventral valve, SMNH Br151187. E, F. Specimens with both valves preserved, view on the ventral valve, SMNH Br151188 and 151189, respectively. Scale bar: 1 mm (A1, B–F), 250 µm (A3), 50 µm (A2).

Fig. 5 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 5. Lingulid brachiopod Eoobolus priscus (Poulsen, 1932) from the lower Cambrian Emyaksin Formation, Bol'shaya Kuonamka River, Siberia, Russia; samples 6/66.2 (A–I, L) and 7/55 (J, K). A–E, L. Ventral valves, SMNH Br151173–151177, 151272, respectively. E2, close up of E1; L2, L3, close-ups of the brephic shell. F–K. Dorsal valves, SMNH Br151178–151183, respectively. Scale bar: 1 mm (A–E1, F–K), 500 µm (L1), 250 µm (E2), 60 µm (L2), and 8 µm (L3).

Fig. 2 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 2. Stratigraphic columns of sections 96-1 and 96-2, Malaya Kuonamka River and section 96-8, Bol'shaya Kuonamka River, Siberia, Russia (after Kouchinsky et al. 2011: fig. 2). Arrows with numbers indicate derivation of fossiliferous samples. Botoman Stage is correlated herein with the Cambrian Stage 4, in accordance with Geyer (2019). Asterisk A, indicates occurrences of Davidonia anabarica, Enigmaconus? pyramidalis, Pelagiella sp. 1 and 2, Majatheca tumefacta, Tetratheca clinisepta, "Lenatheca groenlandica", Conotheca cf. mammilata, Parkula cf. esmeraldina (see Kouchinsky et al. 2015a). Asterisk B, indicates occurrences of Anabaroconus sibiricus, Eotebenna viviannae, Kuonamkaella oliva, Leptostega cf. hyperborea, Pelagiella sp. cf. Cambretina mareki, Pelagiella sp. cf. Costipelagiella zazvorkai, Pojetaia dentifera, Protowenella sp., Pseudomyona queenslandica, and Yochelcionella angustiplicata (see Gubanov et al. 2004b and Kouchinsky et al. 2011). Abbreviations: Ac., Acadoparadoxides; An., Anabaraspis; B., Bergeroniellus expansus; P., Paramicmacca; Fm., Formation; H., Homotreta; O-S, Ovatoryctocara–Schistocephalus; T., Triplagnostus.

FIGURE 5 in Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages

FIGURE 5. Reconstruction of Chuandianella ovata. Upper: dorsal view. Lower: ventral view. Right middle: isolated appendages a1-a3. Not to scale. Abbreviations as in Figures 1-3.

FIGURE 4 in Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages

FIGURE 4. Photographs of Chuandianella ovata, showing morphological details. (A-E) YKLP 16217a (cf. Appendix 9). (A) Dorsal view. Scale bar equals 8.3 mm. (B) Setae on inner surface of 7th podomere of left a1. Scale bar equals 0.1 mm. (C) Setae on inner surface of 5th podomere of right antenniform first appendage. Scale bar equals 1.6 mm. (D) Setae on inner surface of 5th podomere of left antenniform first appendage. Scale bar equals 1.3 mm. (E) Pits on carapace surface. Scale bar equals 1.0 mm. (F-G) YKLP 16238a, specimen depicted in Figure 1F. (F) dorsal view. Scale bar equals 8.4 mm. (G) Visual surface of the left eye. Scale bar equals 1.6 mm. (H,K) YKLP 16259, a laterally compressed specimen with anterior part of right valve missing, exposing the anterior appendages. Posterior part of trunk is also missing. (H) Overview. Scale bar equals 6.0 mm. (K) Detailed view of anterior part, showing position and morphology of a2. Scale bar equals 2.4 mm. (I-J) YKLP 16239, specimen depicted in Figure 1G-H. (I) Dorsal view with trunk reflexed so that it appears to emerge from anterior end of carapace. Scale bar equals 8.8 mm. (J) Pits on carapace surface. Scale bar equals 0.9 mm. Abbreviations additional to Figures 1, 2: app, appendage; vs, visual surface. Italics indicate a right-side appendage. Scale bar in (I) applies to all panels.

FIGURE 2 in Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages

FIGURE 2. Micro-CT images of Chuandianella ovata. (A) YKLP 16238, left lateral view, showing endopods and exopods of trunk appendages. Scale bar equals 4.9 mm. (B,C) YKLP 16239. (B) Ventral view, showing circa 20 eggs within the left valve. Scale bar equals 4.3 mm. (C) Endopods of 3rd and 5th (?) appendages showing long blade-like endites each with a terminal seta. Proximally in this image two endopods overlap, giving the false impression of setae along the lateral margins of the endites. Scale bar equals 3.4 mm. All panels are stereo-pairs. Abbreviations additional to Figure 1: eg, egg; se, seta; tr, trunk. Italics indicate a right-side appendage.

FIGURE 8 in A new euarthropod with large frontal appendages from the early Cambrian Chengjiang biota

FIGURE 8. Diagrammatic reconstructions of Fengzhengia mamingae gen. et sp. nov. A, dorsal view; B, lateral view. The scale bar is 5 mm. Abbreviations: as, medial axial spines; en, endopod; ex, exopod; hl, frontal head limb; hs, head shield; lae, left eye; pyg?, putative pygidium; rae, right eye; tf, tail fan; t1, tergite 1; t9, tergite 9; t15, tergite 15. Morphological details of the tail fan were partially inferred from Kylinxia zhangi Zeng, Zhao, and Huang in Zeng et al., 2020.

FIGURE 1 in Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages

FIGURE 1. Micro-CT images of Chuandianella ovata. (A,C-E,G) YKLP 16218. (A) Ventral view. Scale bar equals 5.0 mm. (C) Ventral view (white rectangle in A), showing details of second appendage (a2, green). Scale bar equals 2.0 mm. (D) Endopod of 6th appendage showing endites. Scale bar equals 1.6 mm. (E) Close-up view of 2nd appendages, with podomeres numbered. Scale bar equals 1.4 mm. (G) Ventral view of the anterior part of A, showing the arrangements of the anterior appendages. Scale bar equals 1.3 mm. (B,F) YKLP 16216. (B) Taphonomically deformed specimen, showing ventral view of the carapace and dorsal view of the soft parts (cf. Appendix 7). Scale bar equals 3.8 mm. (F) Dorsal view of part of right side of the body, showing exopods (blue) and endopods (green). Scale bar equals 1.4 mm. All panels except for E are stereo-pairs. Abbreviations: a1, antenniform first appendage; a2, second appendage; a3-a12, biramous appendages; ab1-4, abdominal segments 1 to 4; an, anus; asc, anterior sclerite; cs, caudal structure; en, endopod; es, eye stalk; et, endite; ex, exopod; ey, stalked eyes; lv, left valve; rv, right valve; tp, tailpiece. Italics indicate a right-side appendage.

FIGURE 7 in A new euarthropod with large frontal appendages from the early Cambrian Chengjiang biota

FIGURE 7. Consensus trees from Bayesian (left) and parsimony (right) analyses of panarthropod relationships based on a matrix of 283 characters and 84 taxa with deutocerebral frontal-most appendages inferred. A, 50% majority-rule consensus tree from a Bayesian analysis; B, strict consensus of a single most parsimonious tree of 54.38597 steps (consistency index = 0.48; retention index = 0.86) from a parsimony analysis using implied character weighting (concavity constant k = 3). In the parsimony analysis Fengzhengia mamingae gen. et sp. nov. is retrieved as the sister taxon to the early branching deuteropod Kylinxia zhangi Zeng, Zhao, and Huang in Zeng et al., 2020. In the Bayesian analysis F. mamingae is resolved as a deuteropod that bridges between K. zhangi and all other deuteropods. Abbreviations: D, Deuteropoda; P, Panarthropoda; T, total-group Euarthropoda.