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Figure 8. A–K in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 8. A–K. Scales of thelodont Barlowodus sp. cf. B. floralis from the uppermost Silurian of the Birch Creek II section, all level 430.5'. A, UCR 10746-31 in baso-lateral view; B, UCR 10746-35 in crown view; C, UCR 10746-36 in crown view; D, UCR 10746-34 in crown view; E, UCR 10746-42 in crown view; F, UCR 10746-29 in crown view; G, UCR 10746-24 in crown view; H, UCR 10746-38 in crown view; I, UCR 10746-23 in crown view; J, K, UCR 10746-14, in crown view, and close up of dorsal mid-crown showing ultrasculpture and taphonomic effects. Scale bars=0.2 mm; anterior to left except A, D, G, I. See Table 1 for meterage.

Figure 7 in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 7. Thelodont scales from the uppermost Silurian of the Birch Creek II section, all level 430.5' except B, C, G, K, L, P, Q. A. Trimerolepis sp. cf. T. tricava. UCR 10746-43 in crown view. B. Trimerolepis sp. AMF97876 (Parkes 1995, fig. 22.19, 20) from level 503', base view. C.?Lanarkia sp. UCR 944-20 (level 527.25') in lateral view. D.?Turinia sp. UCR10746-19, showing taphonomic effects and ultrasculpture, in crown view. E-J. Nikolivia spp. E. UCR 10746-13 with cell pattern on surface in crown view; F, UCR 10746-20 in crown view; G, AMF97875 (Parkes 1995, fig. 22.17, 18) from level 402' with possible bite marks, in crown view; H, UCR 10746-27 in ventral basal view; I, UCR 10746-25 showing taphonomic effects in crown view; J, Nikolivia sp. cf. N. auriculata, UCR 10746-18 in crown view. K, L. Apalolepis sp. AMF97872 (level 503') (Parkes 2005, fig. 22.11, 12), crown and basal views. M-O. Talivalia sp. cf. T. elongata. M, UCR 10746-17 in crown view; N, UCR 10746-37 in crown view; O, UCR 10746-21 in lateral view. P-S. Barlowodus sp. cf. B. tridens. P, Q, AMF97874 (level 875') in crown and basal views (Parkes 2005, fig. 22.15, 16). R, S, UCR 944-21 (level 527.25') in laterocrown view, closeup in S showing striated ultrasculpture. Scale bars=0.2 mm; anterior to left or top, otherwise arrow points to anterior. See Table 1 for meterage.

Figure 6 in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 6. Chondrichthyan and stem osteichthyan scales from the uppermost Silurian of the Birch Creek II section; A, C–G, light microscope images of whitened specimens; B, ESEM image. A-C. Ellesmereia schultzei. A, scale UCR 10746- 44 (level 430.5') in crown view (from Suppl. 1, fig. 5); B, UCR 10746-28 (level 430.5') in anterolateral-crown view; C, scale UCR10746-45 (level 430.5' in crown and lateral views (from Suppl. 1, fig. 4). D. Polymerolepis sp. scale UCR 10752-1 (level 458.67') in crown view (from Suppl. 1, fig. 11). E-G. Lophosteus sp. cf. L. superbus. E, dermal bone fragment 10754-1 (level 468') in external view (from Suppl. 1, fig. 12); F, G, tubercles UCR951-1, 2 (level 457') in crown views (from Suppl. 1, fig. 10). Scale bars=0.25 mm, anterior of scale is up or to left, otherwise arrow points to anterior. See Table 1 for meterage.

Figure 5. Funicristata nevadaensis n. gen. n in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 5. Funicristata nevadaensis n. gen. n. sp. from the uppermost Silurian of the Birch Creek II section. A–C. UCR 10750-3 (level 456.5') in crown views and magnified view of the crown ridges; D, E. UCR 10750-2 (level 456.5') in crown and lateral views; F, G. UCR 10746-10 (level 430.5') in anterocrown and crown views; H, I. UCR 10746-8 (level 430.5') in anterocrown and laterocrown views; J, K. UCR 10750-10 (level 456.5') vertical longitudinal section; L. UCR 10750-12 (level 456.5') horizontal section through crown. Abbreviations: c=canal; en=enameloid; h=hyphal boring; po=pore openings. Scale bars=0.1 mm in A, B, D–L, 0.01 mm in C; anterior is to left or down, otherwise arrows point to anterior. See Table 1 for meterage.

Figure 4 in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 4. Nostovicina and Nostolepis sp. acanthodian scales from the Siluro-Devonian boundary levels of the Birch Creek II section. A. Nostovicina sp. cf. N. elegans: UCR 10755-1 (level 470.2') in crown view (from Supplement 1, fig. 13). B–D, J. Nostovicina laticristata: B. UCR 10768-10 (level 518.3') in crown view; C, D. UCR 10768-6 (level 518.3') in anterocrown and crown views; J. UCR 10768-11 (level 518.3') horizontal thin section through crown. E–I, K, L. Nostovicina sp. cf. N. guangxiensis; E. UCR 5443-1 (level 562.6') in anterocrown view; F, G. UCR 5443-3 (level 562.6') in crown and lateral views; H. UCR 5443-4 (level 562.6') in posterocrown view; I. UCR 5443-6 (level 562.6') in crown view; K, L. UCR 5443-7 (level 562.6') vertical transverse section, magnified view of crown structure in L. M–P. Nostovicina sp. cf. N. lacrima: M. UCR 5439-8 in lateral view; N. UCR 5439-6 in posterior view; O. UCR 5439-4 (level 549') in lateral view; P. UCR 10768-1 (level 518.3') in anterior view. Q–T. Nostolepis matukhini: Q, R. UCR 5443-2 (level 562.6') in crown and laterocrown views; S, T. UCR 5443-5 (level 562.6') in crown and anterocrown views. Abbreviations: cgz=crown growth zones; h=hyphal borings; Sf=Sharpey's fiber bundles. Scale bars=0.1 mm, anterior of scale is to right or up, otherwise arrows point to anterior. See Table 1 for meterage.

Figure 3 in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 3. Poracanthodid and ischnacanthid acanthodian scales from Upper Silurian levels of the Birch Creek II section. A–E,?F,?G. Gomphonchoporus hoppei: A. UCR 949-1 (level 567.3') in crown view (from Supplement 1, fig. 24); B. UCR 944-11 (level 527.25') in laterocrown view; C, D. UCR 5439-2 (level 549') in anterocrown and laterocrown views; E. UCR 5439-3 (level 549') in basal view; F. UCR 5439-7 (level 549') in crown view; G. UCR 5439-1 (level 549') in anterocrown view. H–J. Zemlyacanthus menneri: UCR 10815-1, 2, 3 (level 556.5'), in crown views (from Supplement 1, fig. 22). M–P. Trundlelepis cervicostulata: K, L. UCR 10768-4 (level 518.3') in anterior and lateral views; M. UCR 944-17 (level 527.25') in crown view; N. UCR 944-3 (level 527.25') in crown view; O. UCR 944-23 (level 527.25'), vertical longitudinal thin section; P. UCR 944-22 (level 527.25'), horizontal thin section through crown. Q, R. Poracanthodidae gen., sp. indet. sensory line scale UCR 930-3 (level 395') in crown and posterior views. S-V. Gomphonchus sandelensis: S, T. UCR 10746-11 (level 430.5') in crown and lateral views; U, V. UCR 930-7 (level 395') in antero- and posterocrown views. W–Z. Gomphonchus mediocostatus: W. UCR 944-6 (level 527.25') in crown view; X. UCR 944-16 (level 527.25') in crown view; Y. UCR 942-1 (level 526') in crown view (from Supplement 1, fig. 20); Z. UCR 944-19 (level 527.25') in laterocrown view. Abbreviations: cgz=crown growth zones; dt=dentine tubules; h=hyphal borings; vc=vertical canals. Scale bars=0.1 mm, anterior of scale is to left or down, otherwise arrows point to anterior. See Table 1 for meterage.

Figure 2 in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 2. Poracanthodid acanthodian scales from Upper Silurian levels of the Birch Creek II section, SEM images. A–G. Poracanthodes punctatus: A, B. UCR 930-2 (level 395') in lateral and posterobasal views; C. UCR 930-6 (level 395') in posterobasal view; D, E. UCR 930-5 (level 395') in crown and posterocrown views; F, G. UCR 930-1 (level 395') in lateral and basal views. H–P,?Q–V. Poracanthodes canadensis: H, I. UCR 930-4 (level 395') in crown view; J, K. UCR 10746-6 (level 430.5') in crown view plus closeup of crown pores; L–N. UCR 10750-6 (level 456.5') in anterior and crown views, and closeup of pores near hyphal borings; O. UCR10746-5 (level 430.5') in laterocrown view; P. UCR 540-1 (level 510') in crown view (from Supplement 1, fig. 17); Q–S. UCR 10768-3 (level 518.3') in crown, anterocrown views, and closeup of posterior crown surface; T. UCR 930-8 (level 395'), horizontal thin section through crown; U, V. UCR 10746-12 (level 430.5'), vertical thin section through anterior half of crown; W–BB. Radioporacanthodes porosus: W, X. UCR 10750-7 (level 456.5') in crown and anterocrown views; Y, Z. UCR 10746-4 (level 430.5') in anterocrown and lateral views; AA. UCR 10746-9 (level 430.5') in crown view; BB. UCR 10750-11 (level 456.5'), horizontal thin section through crown, showing two radial pore canals, viewed with Nomarski optics. CC–EE. Radioporacanthodes scheii: CC. UCR 10750-5 (level 456.5') in crown view; DD, EE. UCR 10750- 1 (level 456.5') in crown view plus closeup of pores and hyphal borings. Abbreviations: arc=arcade canals; b=scale base; c=scale crown; h=hyphal borings; n=neck; p=pore; pc=pore canal; pco=pore canal opening under posterior crown; pr=pore canal opening row on crown surface; rc=radial canal. Scale bars=0.1 mm, anterior of scale is to left or down, otherwise arrows point to anterior. See Table 1 for meterage.

Figure 1. Birch Creek II in Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A.

Figure 1. Birch Creek II section, central Roberts Mountains, Nevada. A. locality map, topographic map showing locations of sections BC II, BC III, WC I, WC IV after Murphy (2016, appendix 1). B. stratigraphic column through the uppermost Silurian– lowermost Devonian (after Klapper and Murphy 1975, fig. 5; scale on left is in feet; X denotes their proposed Silurian–Devonian boundary at approx. 567'=172.8 m level); to the right, stratigraphically significant conodont ranges in red, graptolites in blue (see Murphy 2016, fig. 2).

Figure 17 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 17. Selected representatives of nautiloids from the Aras Valley section. (a) Domatoceras parallelum (Abich, 1878), specimen MB.C.29346 from the lower Julfa Formation. (b) Pleuronautilus sp., specimen MB.C.29347 from the lower Julfa Formation. (c) Tainoceras (?) sp., specimen MB.C.29348 from the upper Julfa Formation. (d) Pleuronautilus sp., specimen MB.C.29349 from the Zal Member. (e) Liroceras sp., specimen MB.C.29350 from the lower Julfa Formation. (f) Permoceras abichi (Kruglov, 1928), specimen MB.C.29351 from the lower Julfa Formation. (g) Liroceras sp., specimen MB.C.29352 from the lower Julfa Formation.

Figure 18 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 18. Succession carbon isotopes (δ13 C) in the Aras Valley section and correlation with the conodont stratigraphy. Abbreviated carb conodont zones: (1) Clarkina bachmanni, (2) Clarkina abadehensis, (3) Clarkina hauschkei, (4) Merrillina ultima–Stepanovites mostleri.

Figure 15 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 15. Selected representatives of ammonoids from the Aras Valley section. (a) Prototoceras discoidale Ruzhencev, 1963, specimen MB.C.29343 from the lower Julfa Formation. (b) Vedioceras fusiforme Korn & Ghaderi, 2019, holotype MB.C.29132 from the upper Julfa Formation. (c) Iranites transcaucasius (Shevyrev, 1965), specimen MB.C.29148 from the Zal Member. (d) Pseudotoceras sp., specimen MB.C.29344 from the lower Julfa Formation. (e) Dzhulfoceras sp., specimen MB.C.29345 from the upper Julfa Formation. (f) Dzhulfites nodosus Shevyrev, 1965, specimen MB.C.29182 from the Zal Member at −9.50 m. (g) Araxoceltites cristatus Korn, Ghaderi and Ghanizadeh Tabrizi, 2019, holotype MB.C.22706 from the Zal Member. (h) Phisonites triangulus Shevyrev, 1965, specimen MB.C.22703 from the Zal Member at −12.90 m.

Figure 13 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 13. Succession of ostracod species in the Paratirolites Limestone, Aras Member, and Claraia Beds of the Aras Valley section .

Figure 7 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 7. Carbonate microfacies of samples from the Aras Member (a, b) and the Claraia Beds (c–e) of the Aras Valley section. (a) Burrowed mudstone with calcite fan structures; sample AJ202 (+1.65 m). (b) Burrowed mudstone with calcite fans; sample AJ203 (+2.00 m). (c) Gastropod mudstone and wackestone with microgastropods and sponge remains of possible keratose sponges; sample AJ204 (+2.35 m). (d) Laminated mudstone with irregularly shaped sparry calcite crystals; sample AJ210 (+3.80 m). (e) Laminated mudstone with subrounded sparry calcite crystals; sample AJ216 (+4.95 m). Scale bar units = 1 mm.

Figure 10 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 10. Characteristic conodonts from the Aras Valley section (scale bars equal to 100 µm); all specimens stored in the collection of the Ferdowsi University, Mashhad. (a) Clarkina leveni Kozur et al., 1975, FUM no. AJ122-1, lower Julfa Formation, upper view; (b) Clarkina guangyuanensis Dai and Zhang in (Li et al., 1989), FUM no. AJ131-7, upper Julfa Formation, upper view; (c) Clarkina liangshanensis (Wang, 1978), FUM no. AJ179-8, upper Julfa Formation, upper view; (d) Clarkina transcaucasica (Gullo and Kozur, 1992), FUM no. AJ151-5, upper Julfa Formation, upper view; (e) Clarkina orientalis (Barskov and Koroleva, 1970), FUM no. AJ157-9, upper Julfa Formation, upper view; (f) Clarkina changxingensis (Wang and Wang in Zhao et al., 1981b), FUM no. AJ173-1, Ali Bashi Formation, Zal Member, upper view; (g) Clarkina subcarinata (Sweet in Teichert et al., 1973), FUM no. AJ165-7, Ali Bashi Formation, Zal Member, upper view; (h) Clarkina deflecta (Wang and Wang, 1981a), FUM no. AJ177-14, Ali Bashi Formation, Paratirolites Limestone, upper view; (i) Clarkina bachmanni Kozur, 2004, FUM no. AJ185-23, Ali Bashi Formation, Paratirolites Limestone, upper view; (j) Clarkina nodosa Kozur, 2004, FUM no. AJ190-7, Ali Bashi Formation, Paratirolites Limestone, upper view; (k) Clarkina yini Mei, 1998b, FUM no. AJ192-5, Ali Bashi Formation, Paratirolites Limestone, upper view; (l) Clarkina tulongensis (Tian, 1982), FUM no. AJ198-4, Ali Bashi Formation, Paratirolites Limestone, upper view; (m) Clarkina abadehensis abadehensis Ghaderi, 2014, FUM no. AJ198-13, Ali Bashi Formation, Paratirolites Limestone, upper view; (n) Clarkina abadehensis iranica Ghaderi, 2014, FUM no. AJ198-9, Ali Bashi Formation, Paratirolites Limestone, upper view; (o) Clarkina hauschkei Kozur, 2004, FUM no. AJ200-77, Ali Bashi Formation, Paratirolites Limestone, upper view; (p) Clarkina taylorae (Orchard et al., 1994), FUM no. AJ198-21, Ali Bashi Formation, Paratirolites Limestone, upper view; (q) Clarkina cf. chengyuanensis, FUM no. AJI195-23, Ali Bashi Formation, Paratirolites Limestone, upper view.

Figure 11 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 11. Characteristic conodonts from the Aras Valley section (scale bars equal to 100 µm); all specimens stored in the collection of the Ferdowsi University, Mashhad. (a) Merrillina ultima Kozur, 2004, Pa element, FUM no. AJ204.13, Elikah Formation, Aras Member, lateral view; (b) Stepanovites sp., Sc element, FUM no. AJ205-1, Elikah Formation, Aras Member, lateral view; (c) Hindeodus typicalis (Sweet, 1970), FUM no. AJ200-27, Ali Bashi Formation, Paratirolites Limestone, lateral view; (d) Hindeodus julfensis (Sweet, in Teichert et al., 1973), FUM no. AJ183-8, Ali Bashi Formation, Paratirolites Limestone, lateral view; (e) Hindeodus julfensis (Sweet, in Teichert et al., 1973), FUM no. AJ183-5, Ali Bashi Formation, Paratirolites Limestone, lateral view; (f) Hindeodus bicuspidatus Kozur, 2004, FUM no. AJ200-32, Ali Bashi Formation, Paratirolites Limestone, lateral view; (g) Hindeodus praeparvus Kozur, 1996, FUM no. AJ201-4, Elikah Formation, Aras Member, lateral view; (h) Hindeodus eurypyge Nicoll et al., 2002, FUM no. AJ208-2, Elikah Formation, Aras Member, lateral view; (i) Hindeodus parvus (Kozur and Pjatakova, 1976), FUM no. AJ206-2, Elikah Formation, Aras Member, lateral view; (j) Hindeodus magnus Kozur, 2004, FUM no. AJ211-15, Elikah Formation, Claraia Beds, lateral view; (k) Hindeodus anterodentatus (Dai et al., 1989), FUM no. AJ208-7, Elikah Formation, Aras Member, lateral view; (l) Isarcicella staeschei Dai & Zhang, 1989, FUM no. AJ216-2, Elikah Formation, Claraia Beds, upper view; (m) Isarcicella isarcica (Huckriede, 1958), FUM no. AJ217-13, Elikah Formation, Claraia Beds, upper view.

Figure 3 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 3. Columnar section of the late Permian to Early Triassic succession in the Aras Valley section with colour indications and numbers of microfacies and conodont samples.

Figure 2 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 2. The Permian–Triassic boundary section near the Aras Valley, NW Iran. View towards the north, in the background, beyond the Aras Valley, mountains in Azerbaijan consisting of Triassic rocks.

Figure 12 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 12. Quantity of ostracod specimens per 500 g of rock material and species richness in the Paratirolites Limestone, the Aras Member, and the Claraia Beds of the Aras Valley section and important ostracod species in the lithological units. Scale bar for figured ostracods = 100 µm. Figured ostracods are as follows. (a) Bairdia kemerensis Crasquin-Soleau, 2004. (b) Bairdiacypris ottomanensis CrasquinSoleau, 2004. (c) Liuzhinia sp. 2. (d) Langdaia sp. (e) Cavellina sp. (f) Microcheilinella sp. (g) Cavellina sp. nov. (h) Kempfina qinglaii (Crasquin), 2008. (i) Fabalicypris sp. nov. (j) Carinaknightina sp. nov. (k) Iranokirkbya brandneri Kozur and Mette, 2006. (l) Fabalicypris obunca Belousova, 1965. (m) Fabalicypris blumenstengeli Crasquin, 2008. (n) Orthobairdia sp. nov. (o) Hungaroleberis sp. nov. (p) gen. nov. sp. nov.

Figure 6 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 6. Carbonate microfacies of samples from the upper Julfa Formation and the Paratirolites Limestone of the Aras Valley section. (a) Peloidal–foraminiferal packstone; sample AJ144 (−18.00 m). (b) Peloidal–foraminiferal packstone with algae; sample AJ190 (−2.20 m). (c) Microfacies sample from the topmost 4 cm of the Paratirolites Limestone (sample AJ200; = 0.00 to −0.04 m). Lower part: burrowed bioclastic–intraclastic wackestone with ammonoids, bivalves and ostracods, lithoclasts, and micrite clasts. Upper part: sponge packstone with ammonoids, bellerophontids, and ostracods; uppermost 10 mm with a densely packed sponge meshwork of possible keratose sponges. Scale bar units = 1 mm.

Figure 5 in Aras Valley (northwest Iran): high-resolution stratigraphy of a continuous central Tethyan Permian-Triassic boundary section

Figure 5. Carbonate microfacies of samples from the Paratirolites Limestone of the Aras Valley section. (a) Burrowed bioclastic mudstone with ammonoids and micritic intraclasts; sample AJ182 (−3.65 m). (b) Burrowed bioclastic wackestone with ammonoids and echinoderms (E); sample AJ186 (−2.95 m). (c) Burrowed bioclastic–intraclastic mudstone with Fe-encrusted ammonoid; sample AJ188 (−2.70 m). (d) Burrowed bioclastic–intraclastic wackestone with shell debris and echinoderms, micrite clasts, and intense brecciation; sample AJ197 (−0.45 m). Scale bar units = 1 mm.