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Fig. 14. A in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 14. A. Hypothesized morphogenetic pathway for derivation of the bivalved stenothecoid scleritome from a multisclerite, tubular, organocalcitic, eccentrothecimorph ancestor via a hypothetical organocalcitic tannuolinid. Eccentrothecimorph slightly modified from Skovsted et al. (2011: text-fig. 17). Tannuolinid modified from Skovsted et al. (2014). B. A possible cladogram that assumes an organocalcitic scleritome is primitive for the Pan-Brachiopoda. In this view, organophosphatic mineralogy evolved independently several times and the Stenothecoida evolved a bivalved scleritome independently of the Brachiopoda + Micrina clade.

Fig. 7 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 7. SEM micrographs of stenothecoid pan-brachiopod Stenothecoides cf. elongata, middle Cambrian, Burgess Shale Formation, Kootenay National Park, Canada, Locality 3. A. ROMIP 66248, articulated shell in right lateral view. B. ROMIP 66249, articulated shell in left lateral (B1) and posterior (B2)

Fig. 5 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 5. Stenothecoid pan-brachiopod Stenothecoides rasettii sp. nov., middle Cambrian, Burgess Shale Formation, Yoho National Park, Canada, Locality 2 (A, G) and Locality 1 (B–F, H–J). A. TMP 2002.083.0178, dorsal valve in interior (A1), exterior (A2), right lateral (A3), and posterior (A4) views. B. TMP 2008.024.1138, ventral valve in interior view. C. TMP 2008.024.1133, dorsal valve in interior view, arrows show possible bifurcated peripheral ridges. D. TMP 2008.024.1143, dorsal valve in interior (D1) and anterior oblique (D2) views. E. TMP 2008.024.1144, dorsal valve in interior (E1) and anterior (E2) views. F. TMP 2008.024.1134, ventral valve, interior view. G. TMP 2002.083.0177 (same specimen as Fig. 4B), ventral valve in interior (G1, magnified) and oblique (G2) views. H. TMP 2008.024.1135, dorsal valve in interior view. I. TMP 2008.024.1121, ventral valve, anterior view. J. TMP 2008.024.1136, ventral valve in interior view, showing detached apical boss and remnant apical stem and cardinal troughs.

Fig. 4 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 4. Stenothecoid pan-brachiopod Stenothecoides rasettii sp. nov., middle Cambrian, Burgess Shale Formation, Yoho National Park, Canada, Locality 2 A, B, D) and Locality 1 (C, D). A. TMP 2002.083.0176 (holotype), dorsal valve in exterior (A1) and interior (A2) views. B. TMP 2002.083.0177, ventral valve in exterior view. C. TMP 2008.024.1147, dorsal valve, internal apical area. D. TMP 2008.024.1122, articulated juvenile, dorsal/ventral (uncertain) valve in posterior (D1), lateral (D2), and oblique planar (D3) views; D1 and D3 show posterior median opening, D2 shows slightly sinusoidal commissure.

Fig. 3 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 3. Orientation, measurements, and ridge zones in Stenothecoides rasettii sp. nov. A. Ventral valve, exterior, showing orientation for measurements. B. Ventral valve, interior, showing peripheral and axial ridge zones, and approximated body cavity. Abbreviations: ax, auricular axis; az, axial ridge zone; bc, body cavity; L, valve length; ll, left lobe; lx, lobe axis; pz, peripheral ridge zone; rl, right lobe; vx, valve axis; W, valve width.

Fig. 2 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 2. Stratigraphic and geographic distribution of sample localities. A. Stratigraphic position of localities 1–3 indicated with stars. Thicknesses of units at Fossil Ridge/Mount Field from Fletcher and Collins (1998) and Mount Stephen northwest shoulder from Christopher J. Collom and PAJ (unpublished data); stratigraphic units after Collom et al. (2009), Odaray Mountain section from Streng et al. (2016). Helcionellid icons show known silicified assemblages. B. Geographic distribution of localities 1–3 relative to the Cathedral escarpment. C. Known stratigraphic distribution of stenothecoids in British Columbia, Utah, and Nevada. Stratigraphy modified from Johnston et al. (2009a). D. General location of study area in western Canada. Abbreviations: CC, Campsite Cliff Shale Member; Fm., Formation; KH, Kicking Horse Shale Member; Loc, Locality; MF, Monarch Formation; Mt., Mount or Mountain; S., Stenothecoides; WA, Wapta Member; WL, Wash Limestone Member; WQ, Walcott Quarry Shale Member; YR, Yoho River Limestone Member.

Fig. 9 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 9. Bivariate plots of length and width and best fit lines of Stenothecoides rasettii sp. nov., Burgess Shale Formation, Locality 2 (tectonic strain is evident in some specimens at Locality 1, which are excluded from this plot); Stenothecoides elongata (Walcott, 1884), Wheeler Formation, Drum Mountains, Utah, USA, Locality 8 of Robison (1964); Stenothecoides cf. elongata, Burgess Shale Formation, Locality 3; Stenothecoides cf. elongata, Mount Whyte Formation, Ross Lake, Mount Stephen, and Mount Field, Yoho National Park, Canada (Rasetti 1954, 1957).

Fig. 13 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 13. Stylized anatomical reconstruction of the stenothecoid pan-brachiopod Stenothecoides rasettii sp. nov. A. Dorsal valve, plan view. B. Longitudinal section slightly off the midline of the valves and normal to commissure. Colors: black in A, shell outline; black in B, valves and juxtaposed apical bosses; green, pedicle, inserting on posterior surface of apical boss and in cardinal troughs; red, muscles originating on anterior surface of apical boss and attaching to the anterior body wall; turquoise, visceral mass; orange, lophophore; grey, peripheral and axial furrow zones; short black lines, cilia in grooves between mantle canals; blue arrows, inferred inhalant and exhalant water currents; dotted areas, coelomic fluid; olive green, setae omitted in A). Lophophore modelled after Heliomedusa (Chen et al. 2007).

Fig. 8 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 8. Stenothecoid pan-brachiopod Stenothecoides elongata (Walcott, 1884), middle Cambrian, Drumian Stage stratotype, Drum Mountains, western Utah (USA), Locality 8 (Robison 1964), internal shell features. Dorsal vs. ventral valves uncertain. A, B. TMP 2021.022.0001 (A) and TMP 2021.022.0002 B), valves preserving peripheral furrows; note in A a prominent cardinal sulcus. C. TMP 2021.022.0003, valve interior, showing a cardinal pseudosocket. D. TMP 2021.022.0004, valve interior, preserving a nearly symmetrical apical area and conspicuous posterior median opening. E–G. Variation of apical areas of valve interiors. TMP 2021.022.0005 (E), TMP 2021.022.0006 (F), TMP 2021.022.0007 (G).

Fig. 12 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 12. Microstructure in the stenothecoid pan-brachiopod Stenothecoides spp. and co-occurring rhynchonelliformean brachiopods. A–C. Stenothecoides rasettii sp. nov., middle Cambrian, Burgess Shale Formation, Yoho National Park, Canada, Locality 1. A. TMP 2008.024.1142, fragmentary valve in interior view (A1), detail showing silica rods imbricated and inclined toward valve margin (A2). B. TMP 2008.024.1150, ventral valve in exterior view (B1), showing silica rods oriented with proximal ends of rods overlapping distal ends of preceding rods in posterior third of valve, but seemingly reversing orientation in posterior third of valve (B2). C. TMP 2008.024.1141 (same specimen and valve area as in Fig. 11C1, inner box) detail showing silica rods. D, E. Stenothecoides elongata (Walcott, 1884), Drumian Stage stratotype, Drum Mountains, western Utah (USA), Locality 8 (Robison 1964), external shell features. D. TMP 2021.022.0008, ventral(?) valve in exterior view (D1), detail of anterior end (D2), arrows show incompletely silicified radial rods. E. TMP 2021.022.0009, dorsal(?) valve, anterior end showing silicified outer shell surface with fine radial elements extending across growth varices (black arrows) and apparently shorter radial rods in valve sublayers (white arrows). F, G. Rhynchonelliformean brachiopods, silicified microstructure, Burgess Shale Formation, Canada, Locality 1. F. Tomteluva sp., TMP 2008.024.1151, silicified shell in exterior view (F1), posterior end is broken; anterior is to the right; detail showing orientation of silica rods (F2), anterior is to the left. G. Fragmentary nisusiid, TMP 2008.024.1152, silicified shell in interior view (G1), detail showing imbricated silica rods (G2). A, C, F, SEM images and B, D, E, G, light microscope images.

Fig. 6 in Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation

Fig. 6. Stenothecoid pan-brachiopod Stenothecoides rasettii sp. nov., middle Cambrian, Burgess Shale Formation, Yoho National Park, Canada, Locality 1 A, D, E, G, H) and Locality 2 (B, C, F). A. TMP 2008.024.1140, ventral valve in exterior view. B. TMP 2002.083.0179, ventral valve in exterior (B1) and interior (B2) views. C. TMP 2002.083.0180, dorsal valve in exterior (C1) and interior (C2) views. D. TMP 2008.024.1145, dorsal valve in interior magnified, D) and exterior (D) views. E. TMP 2008.024.1141, ventral valve in interior (E) and exterior (E2) views. F. TMP 2002.083.0181, dorsal 1 2 1 valve in exterior (F1) and interior (F2) views. G. TMP 2008.024.1146, dorsal valve in posterior (G1) and exterior (G2) views. H. TMP 2008.024.1139, ventral valve in interior view.

Fig. 3 in Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Fig. 3. Sclerites of the problematic lophotrochozoan Wiwaxia (NIGP 153962–153977) from the middle Cambrian Kaili Formation, Guizhou, China. A. KAIL−05−01−N28. B. KAIL−GTBM−9−2−a−M38. C. KAIL−05−01−S43. D. KAIL−GTBM−9−35M−02−F25. E. KAIL−05−01−T15. F. KAIL−A−01−R33. G. KAIL−05−03−L36. H. KAIL−GTBM−9−2−b−D40. I. KAIL−GTBM−9−2−d−P33. J. KAIL−GTBM−9−2−d−N34. K. KAIL−GTBM−9−35M−02−J34. L. KAIL− GTBM−9−37M−01−S46 (image reversed). M. KAIL−07−01−L24. N. KAIL−A−01−P37. O. KAIL−05−05−T6. P. KAIL−GTBM−9−37M−01−M22. Scale bars: A 200 µm, B–P 100 µm.

Fig. 7 in Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Fig. 7. Problematic metazoan microfossils (NIGP 153992–154010) from the middle Cambrian Kaili Formation, Guizhou, China. A–F. Ornamented spines cf. Rushtonites/Mongolitubulus. A. KAIL−04−05−M10. B. KAIL−GTBM−9−35M−02−G23. C. KAIL−BP−01−K41. D. KAIL−X−01−P42. E. KAIL−09−01−S31. F−J. Possible elements of a lophotrochozoan jaw apparatus. F. KAIL−05−01−U23. G. KAIL−04−2−T39 (G1); detail (G2). H. KAIL−GTBM−9−2−d−F6 (image reversed). I. KAIL−BP−01−N25 (image reversed). J. KAIL−GTBM−9−2−d−E9. K−O. Diverse spinose forms including possible elements of a radula−like apparatus (M, N). K. KAIL−04−07−Q33. L. KAIL−05−03−J25. M. KAIL−GTBM−9−35M−02−N41. N. KAIL−05−03−M17. O. KAIL−04−09−X27. P, Q. Possible arthropodan seta (P) and setal array (Q). P. KAIL−X−01−M28. Q. KAIL−GTBM−9−35M−01−W29. R, S. Complex forms of unknown affinity. R. KAIL− 05−03−U21. S. KAIL−05−01−F35. Scale bars: A–P, S 100 µm; Q, R 50 µm; G 2 40 µm.

Fig. 2 in Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Fig. 2. Biomineralizing taxa preserved as small carbonaceous fossils (NIGP 153954–153961) from the middle Cambrian Kaili Formation, Guizhou, China. A. Hyolithid helen (A1), with detail of rounded proximal end (A2), KAIL−BP−01−J38. B. Multi−rayed chancelloriid sclerite, KAIL−A−01−P39. C−E. Single−rayed or disarticulated chancelloriid sclerites. C. KAIL−GTBM− 9−2−b−E39. D. KAIL−05−05−O17 (image reversed). E. KAIL−09−01−U19. F–H. Brachiopod fragments (F1, G1, H1), with details of microstructure (F2, G2, G3, H2). F. KAIL−07−01−U38. G. KAIL−05−05−E17. H. KAIL−GTBM− 9−2−d−K41. Scale bars: A1, B–E 200 µm; A2 40 µm; F1 400 µm; F2 125 µm; G1 250 µm; G2 125 µm; G3 60 µm; H1 500 µm; H2 150 µm.

Fig. 4 in Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Fig. 4. Pterobranch periderm (NIGP 153978–153979) from the middle Cambrian Kaili Formation, Guizhou, China. A. KAIL−BP−01−N23. B. KAIL−A− 01−R36. A2 is a photographic detail of A1; A3 and B2 are camera lucida drawings highlighting the fusellar microstructure, including characteristic oblique sutures developed locally in a "zig−zag" arrangement. Scale bars: A1 200 µm; A2, A3 100 µm; B1, B2 400 µm.

Fig. 1 in Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Fig. 1. Filaments and acritarchs (NIGP 153940–153953) from the middle Cambrian Kaili Formation, Guizhou, China. A–G. Cyanobacterial filaments. A–C. Eomicrocoleus Horodyski and Donaldson, 1980/Siphonophycus Schopf, 1968 emended Knoll, Swett, and Mark, 1991 with multiple cellular trichomes enclosed within a common sheath (in C, a double sheath). D,E,G. Siphonophycus spp. exhibiting a variety of growth forms. F. Polytrichoides Hermann, 1974 emend. Knoll, Swett, and Mark, 1991. A. KAIL−04−03−L44. B. KAIL−05−02−V31. C. KAIL−05−05−D13. D. KAIL−GTBM−9−35M−01−T45. E. KAIL− GTBM−9−37M−01−J23. F. KAIL−A−01−K26. G. KAIL−GTBM−9−2−b−M37. H, I. Filaments of uncertain affinity. H. KAIL−GTBM−9−35M−01−E44. I. KAIL− 09−01−H12. J–N. Acritarchs, including forms with medial splitting (K, L) and possible vegetative colony growth (M). J. KAIL−A−01−O25. K. KAIL− 04−05−T17. L. KAIL−04−05−G17. M. KAIL−GTBM−2−9−c−D21. N. KAIL−GTBM−9−2−d−S14. Scale bars A–F, J–L 200 µm; G–I 400 µm; M, N 100 µm.

Fig. 4 in A Marrella-like arthropod from the Cambrian of Australia: A new link between "Orsten"-type and Burgess Shale assemblages

Fig. 4. Localities, in which Marrellomorpha (sensu Kühl et al. 2008) have been found. 1, Monastery Creek Phosphorite Formation, Late Templetonian– Early Floran, Australia: Austromarrella klausmuelleri gen. et sp. nov. 2, Kaili, early middle Cambrian, China: Marrella sp. (Zhao et al. 2003). 3, Burgess Shale, middle Cambrian, British Columbia, Canada: Marrella splendens Walcott, 1912 (Whittington 1971; García−Bellido and Collins 2006). 4, Fezouata biota, Ordovician, Morocco: Furca spp. (Van Roy 2006a, b; Van Roy et al. 2010). 5, Letná Formation, Ordovican, Czech Republic: Furca bohemica Fritsch, 1908 (Chlupáč 1999; Van Roy 2006a, b; Rak 2009; Rak et al. 2013). 6, Herefordshire, Silurian, England: Xylokoris chledophilia Siveter, Fortey, Sutton, Briggs and Siveter, 2007 (Siveter et al. 2007). 7, Hunsrück slate, Lower Devonian, Germany: Vachonisia rogeri Lehmann, 1955 (Kühl et al. 2008); Mimetaster hexagonalis Gürich, 1931 (Kühl and Rust 2010). Table indicates occurrences.

Fig. 3. Marrellomorph Marrella splendens Walcott, 1912 in A Marrella-like arthropod from the Cambrian of Australia: A new link between "Orsten"-type and Burgess Shale assemblages

Fig. 3. Marrellomorph Marrella splendens Walcott, 1912, for comparison with Austromarrella klausmuelleri gen. et sp. nov., Mount Murray, Western Queensland, Australia; Series 3 of the Cambrian. A. Dorsal view on a rendered 3D model, based on own observations. B–E. Micrographs under polarized light. B. Beautifully preserved specimen USNM 83486f with the exopods in a "rusty" preservation (cf. García−Bellido and Collins 2006). C. Stereo image of specimen USNM 139665. Exopods of preceding limbs are super−imposing each other, separated by a thin layer of sediment. D. Detail of specimen ROM 56766A in "rusty" preservation. Here the spines on the lateral side of the exopod ringlets are well preserved. E. One of the smallest specimens of M. splendens USNM 219817e that possesses preserved appendage remains. The single fragmentary specimen of A. klausmuelleri could, based on its size, belong to an entire specimen of a comparable size.

Fig. 1 in A Marrella-like arthropod from the Cambrian of Australia: A new link between "Orsten"-type and Burgess Shale assemblages

Fig. 1. SEM images of the holotype and single specimen CPC 30719 of marrellomorph Austromarrella klausmuelleri gen. et sp. nov., Mount Murray, Western Queensland, Australia; Series 3 of the Cambrian. A. Median or lateral view, exposing the more or less lanceolate lamellae. B. Anterior or posterior view. The 16 ringlets are well separated from each other. Letters indicate the direction of view in images D–F. C. Median or lateral view, opposing to side displayed in A. Here the insertion of the most proximal preserved ringlet is well apparent. D–F. Details of the stout spines on the most distal preserved annuli viewed as indicated in image B. D. View from latero/medio−proximal on the distal tip. E. View from lateral/median, same spine as in D. F. View from medio/latero−proximal. Spine on the other side of the same ringlet as in D and E.

Fig. 2 in A Marrella-like arthropod from the Cambrian of Australia: A new link between "Orsten"-type and Burgess Shale assemblages

Fig. 2. Examples of multi−annulated exopods of fossil and extant representatives of the taxa Agnostina and Crustacea sensu lato. A. SEM image of the exopod of the second head appendage of Agnostus pisiformis (Wahlenberg, 1818) composed of nine articles. Each of the six distal articles bears a pair of long, outwardly directed setae, a short spinule close to the base of the setae and a short seta opposite of the long setae (cf. Müller and Walossek 1987: pl. 18.1). Series 3 of the Cambrian (Agnostus pisiformis Zone), UB 832. B. SEM image of appendages two and three of a stage two larva of the fossil micro−predator Goticaris longispinosa Walossek and Müller, 1990. Series 3 of the Cambrian (Agnostus pisiformis Zone), UB 98. Detail of pl. 2.5 of Haug et al. (2009b). C. SEM image of the appendages two to four of the phosphatocopine Vestrogothia spinata Müller, 1964, Furongian, Cambrian, UB 622. D. Light microscopic image (processed according to Haug et al. 2009a) of a putative thecostracan larva (E_G2010_16_2_1), from the Devonian Windyfield Chert (cf. Fayers and Trewin 2004). E. Composite fluorescence image (cf. Haug et al. 2008) of an undetermined natant decapod from the Solnhofen Lithographic Limestones, Upper Jurassic, Southern Germany (SMNS 70149, ex coll. Gebert, Iphofen). F. SEM image of the second antenna of the Recent mystacocarid Derocheilocaris remanei Delamare−Deboutteville and Chappuis, 1951 (cf. Olesen 2001; Haug et al. 2011). Specimen from the collection of the Zoological Museum, Copenhagen. G. SEM image of a pleomeric segment with a pair of pleopods of the Recent amphipod Gammarus roeselii Gervais, 1835. Image courtesy Gerd Mayer, Ulm.