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. Roc2-a,-late-middle-smithian, A: UBGD 32220; B: UBGD 32221; C: suture line of UBGD 1314 32221 at H = 12.7 mm, pp.32222-32224

G. , lateral and ventral views of UBGD 1315 32225; I: UBGD 32226; J-K: lateral and ventral views of UBGD 32227; L-M: lateral and 1316 ventral views of UBGD 32228; N: UBGD 32229; O: suture line of UBGD 32229 at H = 9.3 1317 mm; P: UBGD 32230. Black arrows indicate the position of the corresponding ventral view. 1318 Scale bars: 10 mm, pp.5-1319

, All specimens from bed BRC, Workman Wash, Utah, early 1321 late Smithian. A-D: lateral, apertural and ventral views of UBGD 32232; E-F: lateral and 1322 ventral views of UBGD 32233; G-H: lateral and ventral views of UBGD 32234; I: UBGD 1323 32235

, N: lateral view of two specimens on block UBGD 32239; O: ventral view of the specimen on 1325 the left of UBGD 32239; P-Q: lateral and ventral views of UBGD 32240, p.1326

. Fig, A-B: lateral and ventral views of UBGD 32280; C-D: 1377 lateral and ventral views of UBGD 32281; E: UBGD 32282; F-G: lateral and ventral views of 1378 UBGD 32283; H-I: lateral and ventral views of UBGD, vol.12

, N: lateral view of UBGD 32287 (star indicates the minute depression visible near the 1381 ventrolateral margin); O: suture line of UBGD 32288 at H = 15.4 mm; P: lateral view of 1382 UBGD 32289; Q: lateral view of UBGD 32290; R-S: lateral and ventral views of UBGD 1383 32291. All specimens from bed BRC, K: lateral and ventral views of UBGD 32285; L-M: lateral and ventral views of UBGD 1380 32286, p.1385

A. Supplementary-figure, H. Scatter-diagrams-of, U. , H. , W. et al., , p.1389

G. Hooveri, Open symbols indicate specimens from Rock Canyon, p.1390

W. White-sage, Grey symbols indicate specimens from central and western 1391

;. Utah and . From-brayard, = 56) and Palomino Ridge (data from Jattiot et, 1392.

B. Supplementary-figure, H. Scatter-diagrams-of, U. , H. , W. et al., , p.1395

G. Smithi, Open symbols indicate specimens from bed BRC, Workman Wash, Utah, 1396 early late Smithian (n = 40). Grey symbols indicate specimens from Palomino Ridge, p.1397

J. From, Jenks and Brayard, p.1398, 2017.

N. ,

C. Supplementary-figure and . Jattiot, Box plots of U/D for Gurleyites smithi and Hemiprionites typus 1401 from the studied area and Nevada. Specimens from Nevada were sampled at Palomino Ridge 1402, Jenks and Brayard, 2017.

D. Supplementary-figure, H. Scatter-diagrams-of, U. , H. , W. et al., , p.1405

, Open symbols indicate specimens from bed BRC, p.1406

, Utah, early late Smithian (n = 14). Grey symbols indicate specimens from Palomino Ridge, p.1407

N. , , 2017.

E. Supplementary-figure, H. Scatter-diagrams-of, U. , H. , W. et al., , p.1410

, Open symbols indicate specimens from bed BRC, p.1411

. Utah and . Early-late-smithian, Grey symbols indicate specimens from Palomino Ridge 1412 (data from Jattiot et al., 2017; n = 58) and Crittenden Springs (data from Jenks and Brayard, 1413.

F. Supplementary-figure, H. Scatter-diagrams-of, U. , H. , W. et al., , p.1416

H. Walcotti, Open symbols indicate specimens from bed BRC, p.1417

. Utah and . Early-late-smithian, Grey symbols indicate specimens from Palomino Ridge 1418 (data from Jattiot et al., 2017; n = 26) and Crittenden Springs (data from Jenks and Brayard, 1419.

A. Supplementary-table, Measurements of some Smithian ammonoids from the studied area, 1422 central and southern Utah (data from Brayard et al., 2013) and Nevada, p.1423

C. Springs, ;. Data, and . Jattiot, and Jenks and Brayard, 2017.