Fomitchella infundibuliformis Missarzhevsky

Kouchinsky, Artem, Bengtson, Stefan, Landing, Ed, Steiner, Michael, Vendrasco, Michael & Ziegler, Karen, 2017, Terreneuvian stratigraphy and faunas from the Anabar Uplift, Siberia, Acta Palaeontologica Polonica 62 (2), pp. 311-440 : 402-405

Fomitchella infundibuliformis Missarzhevsky in Rozanov et al., 1969

Figs. 59 –64.

Material.— Seven topotype specimens, SMNH X5910– 5916 , from sample M314/4 and over 200 sclerites from samples 1/39.3, 1/29.5, 1/29.2, 1/28.5, 1/27.5, 1/26.3, 1/25.5 (section 1, Fig. 4 ), K1a/80 and K1a/82 (section 2, Fig. 1), K2/21, K2/22, K2/23, K2/26, K2/33, K2/38A, K2/43, K2/45, K2/50, K2/52, K2/60?, 3/12.2, 3/20.5, 3/22.5 (section 3, Fig. 3), 5/10, 5/10B, 5a/1, 5a/1.2, 5a/5, 5a/6, 5a/8, 5a/9 (sections 96-5, 96-5a, Fig. 2 ), including figured SMNH X5917–5926 , 5928–5931 , 5933–5935 , 5937–5941 , from other samples (see SOM 1) from the Medvezhya and lower Emyaksin formations, Anabar Uplift , Siberian Platform , Russia. Correlated with the upper Fortunian and lower part of the Cambrian Stage 2 .

Description.—Phosphatic, conical, hollow sclerites with elongate, usually recurved tip and flared base. Basal margin irregularly rounded in planar view and undulating, often with circumferential wrinkles. Outer surface with radial striation, smooth or occasionally bumpy. Inner surface smooth, often with scattered pits and closely spaced wrinkles at the basal margin. Wall with thin growth lamellae, of which the innermost ones are restricted to the apical part.

Remarks.— Topotype specimens of F. infundibuliformis from sample M314/4 ( Figs. 59 , 60) have a broad rounded aperture with the two opposing sides of the margin arched. One of the specimens is compacted perpendicular to the plane of its broken aperture ( Fig. 59E ). A certain similarity exists between the illustrated topotype material and the elements from southeastern Newfoundland and eastern Massachusetts (Landing 1988; Landing et al. 1989). The Avalonian material has a subcircular outline of the aperture and includes specimens ranging from gently to rapidly tapering, are more or less recurved, and have acicular longer or shorter tips (“cusps” sensu Landing 1988).

The species differs from Fomitchella acinaciformis Missarzhevsky, 1977 , in having a flared base, higher rate of expansion, and relatively broad circumferential wrinkled margin. Fomitchella aff. infundibuliformis has a wider apex (Fig. 65); Fomitchella aff. acinaciformis ( Fig. 66A– E ) has narrower, less flared, and more elongate sclerites. Fomitchella sp. ( Fig. 66H ) sclerites are much smaller than

Fig. 60. Problematic calcium phosphatic sclerites Fomitchella infundibuliformis Missarzhevsky in Rozanov et al., 1969, from early Cambrian Medvezhya → Formation , northern flank of the Anabar Uplift , Siberia, Russia; topotypes from sample M314/4, Fomitch River section. A, B. SMNH X5915 , 5916 , respectively. A 2, A 4, B 1, lateral views; A 1, B 3, apertural views; A 3, A 5, B 2, enlargements of the apertural margin showing fibrous composition of outer layer. Scale bar 12.5 μm (B 2), 25 μm (A 5), 100 μm (A 3), 250 μm (A 1, A 2, A 4, B 1, B 3) .

the other specimens. A comparison with other, earlier described species is hampered by their inadequate illustration. Stratigraphic and geographic range.—Upper Fortunian– Cambrian Stage 2 of the Siberian Platform and probably Kazakhstan (Missarzhevsky and Mambetov 1981), Upper Fortunian – lower part of Cambrian Stage 3 of Avalonia (Landing and Brett1982; Bengtson and Fletcher1983; Landing

1988, 1995; Landing et al. 1989); doubtful reports from the Terreneuvian Series of western Mongolia (Missarzhevsky 1977) and South China (Qian and Bengtson 1989).

Figures

Fig. 59. Problematic calcium phosphatic sclerites Fomitchella infundibuliformis Missarzhevsky in Rozanov et al., 1969, from early Cambrian Medvezhya Formation, northern flank of the Anabar Uplift, Siberia, Russia; topotypes from sample M314/4, Fomitch River section. A. SMNH X5910. B. SMNH X5912. C. SMNH X5911. D. SMNH X5913. E. SMNH X5914. A1, B3, C2, D1, E1, lateral; A2, D2, apertural; B1, C1, E2, apical views; B2, close-up of inner surface showing comarginal folds. Scale bar 100 μm (B2), 250 μm (A, B1, B3, C–E).

Fig. 4. The δ13Ccurve for Kotuj River section 1and sampled horizons with fossiliferous samples (arrows with numbers). Shift in stratigraphic column carb at Nemakit-Daldyn–Medvezhya formations contact indicates position of sequence boundary. Stratigraphic ranges and first appearances of fossils (see SOM 1): 2, Oelandiella korobkovi; 3, Securiconus cf. simus; 4, Bemella jacutica?; 8, Anabarella plana; 9, Watsonella crosbyi; 10, Pseudoyangtzespira selindeica; 11, Aldanella crassa; 13, Aldanella attleborensis; 15, Philoxenella spiralis; 16, Barskovia hemisymmetrica; 18, Khairkhania cf. evoluta; 19, Ceratoconus striatus; 21, Salanyella cf. costulata; 23, Purella cristata; 25, Yunnanopleura sp.; 26, Obscurania auriculata; 29, Protoconus cf. crestatus; 32, Siphogonuchites triangularis; 34, Lopochites sp.; 37, first appearance of Halkieria sp.; 39, first appearance of Chancelloria sp.; 40, Tianzhushanella sp.; 42, Khetatheca cotuiensis; 46, Turcutheca sp.; 48, Orthothecid operculum type A; 52, Fomitchella infundibuliformis; 57, Hyolithellus sp.; 62, Selindeochrea missarzhevskyi; 63, Selindeochrea ternaria; 64, Anabarites trisulcatus; 67, Anabarites kelleri; 68, Anabarites biplicatus; 71, Anabarites hexasulcatus; 74, Tiksitheca licis; 75, Cambrotubulus decurvatus; 76, Platysolenites antiquissimus; 77, Blastulospongia sp.

Fig. 2. Composite δ13Ccurve for the Bol’shaya Kuonamka River sections 96-4, 5, and 5a and sampled horizons with fossiliferous samples (arrows with carb numbers). Arrow 4/4 indicates “marker bed with angustiochreids” (Val’kov 1975; Kouchinsky et al. 1999). For section 96-6 see Kouchinsky et al. (2001, 2015a). Shift in stratigraphic column at Manykay–Emyaksin formations contact indicates position of sequence boundary. Stratigraphic ranges and first appearances of fossils (see SOM 1): 1, first appearance of helcionellid molluscs; 2, Oelandiella korobkovi; 3, Securiconus cf. simus; 6, Obtusoconus vostokovae; 7, Obtusoconus cf. mirabilis; 8, Anabarella plana; 13, Aldanella attleborensis; 14, Aldanella cf. sibirica; 22, Purella antiqua; 24, Yunnanopleura accurata; 34, Lopochites sp.; 35, Tianzhushania longa; 37, first appearance of Halkieria sp.; 38, Chancelloria symmetrica; 42, Khetatheca cotuiensis; 44, Conotheca cf. mammilata; 46, Turcutheca sp.; 47, Cupitheca sp.; 50, Orthothecid operculum type C; 51, Protohertzina anabarica; 52, Fomitchella infundibuliformis; 53, Fomitchella aff. infundibuliformis; 54, Fomitchella acinaciformis; 55, Fomitchella aff. acinaciformis; 56, Hyolithellus vladimirovae; 57, Hyolithellus sp.; 60, Selindeochrea cf. tecta; 61, Selindeochrea tripartita; 62, Selindeochrea missarzhevskyi; 63, Selindeochrea ternaria; 64, Anabarites trisulcatus; 65, Anabarites latus; 66, Anabarites natellus; 67, Anabarites kelleri; 68, Anabarites biplicatus; 69, Anabarites tristichus; 70, Anabarites compositus; 71, Anabarites hexasulcatus; 72, Anabarites hariolus; 73, Aculeochrea rugosa; 74, Tiksitheca licis; 75, Cambrotubulus decurvatus; 76, Platysolenites antiquissimus.

Fig. 66. Problematic calcium phosphatic sclerites Fomitchella aff. acinaciformis Missarzhevsky, 1977 (A–E), Fomitchella acinaciformis Missarzhevsky, 1977 (F, G), and Fomitchella sp. (H), from early Cambrian Emyaksin Formation, eastern flank of the Anabar Uplift, Siberia, Russia; samples 5a/10.5 (A, B, E), 5a /17.5 (C, F–H), 5a/9 (D), section 96-5a. A–H. SMNH X5954–5961, respectively. A1, oblique apical; A3, C2, D2, H3, apical; A2, B, C3, D1, E1, F, G2, G3, H1, H2, lateral; E2, apertural; G1, oblique apertural views; C1, close-up of apertural margin with fibres (note two inserted sclerites). Scale bar 50 μm (C1), 250 μm (A1, B, C2, C3, E, H), 500 μm (A2, A3, D, F, G).