Salanyella cf. costulata Missarzhevsky, 1981

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 : 357-359

Salanyella cf. costulata Missarzhevsky, 1981

Figs. 29A–C, E–H, 30.

Material.—About 50 phosphatic internal moulds, including figured SMNH Mo160414, 182314–182316, 182318–182321, and a single partially preserved phosphatized conch with internal mould, SMNH Mo182322, from samples 1/29.2 (section 1, Fig. 4 ), 3/12, 3/12.2, 3/22.5, K2/25, and K2/26 (section 3, Fig. 3), from the Medvezhya Formation, western flanks of the Anabar Uplift, Siberian Platform, Russia. Correlated with the uppermost Fortunian Stage.

Description.—Moderately expanding, short conical shell curved up to 45º, with broadly oval, straight aperture. Apical

→ Fig. 24. Molluscs Barskovia hemisymmetrica Golubev, 1976 (A–C, F, G) and Philoxenella spiralis Vostokova, 1962 (D, E), internal moulds (G, internal mould with partly phosphatized shell), from early Cambrian Medvezhya Formation, western Anabar Uplift (A–F) and unnamed formation, NE Tajmyr (G), northern Siberia, Russia; sample K1a/76A (A), section 2; K2/21 (B) and K2/52 (D), section 3; 1/29.2 (C, E, F), section 1; 1571/2 (G), NE Tajmyr. A–G. SMNH Mo182284–182290, respectively. A 1 –F 1, adapical side; A 2, oblique adapical; G 1, adapical; B 2 –G 2, apertural views; G 4, calcium phosphate cast of canals through the wall and outer shell surface; G 3, cast of canals enlarged. Scale bar 25 μm (G 3), 100 μm (G 4), and 500 μm (A–F, G 1, G 2).

region blunt, rounded, not clearly separated from the rest of the shell. Outer shell surface smooth, with thin closely spaced growth lines ( Fig. 30B 1, B 2).

Remarks.—Moulds are covered with tiny, densely arranged, rounded bumps near the aperture and larger, round to elongate bumps on the adapical surface (Fig. 29E 2). Similar forms were described under the monospecfic genus Lenoconus Vasil’eva, 1990, as Lenoconus sulcatus Vasil’eva, 1990, from the Dockidocyathus regularis Zone of the Tommotian Stage (upper part of Cambrian Stage 2) on the lower reaches of the Lena River at the Ulakhan-Ald’yarkhaj section. The type specimen of L. sulcatus designated by Vasil’eva (1990: pl. 2: 3, 4) has a hooked apical part. It is twice as large as Lenoconus sp. from the Tommotian Stage on the Aldan River (Vasil’eva 1990: pl. 2: 7), which likely represents a juvenive form of the same species. The apical part of the latter is not so curved.

Lenoconus is synonymized herein with Salanyella . The specimens described herein are generally similar in shape and treated as growth stages probably of a single species reported herein as Salanyella cf. costulata . A likely similar form is reported without illustration as S. costulata from the Anabar Uplift and elsewhere on the Siberian Platform by

→ Fig. 26. Mollusc Ceratoconus striatus Chen and Zhang, 1980 , internal moulds, from early Cambrian Medvezhya Formation, Kotuj River, western Anabar Uplift, Siberia, Russia; samples 1/46 (A, B, E), section 1; 3/12.2 (C, F) and K2/25 (D), section 3. A–F. SMNH Mo182297–182302, respectively. A 1 –C 1, E 1, F 2, lateral; A 2 –C 2, D, E 2, F 3, subapical; A 3, C 3, E 3, F 1, supra-apical; B 3, apertural views. Scale bar 500 μm.

Khomentovsky and Karlova (2005). Phosphatized shells of S. costulata Missarzhevsky, 1981 , from Cambrian Stage 2 of western Mongolia have, however, numerous thin transverse ribs not present on the internal moulds from the Anabar Uplift (Figs. 29, 30A). The outer surface of the S. cf. costulata shell is preserved as a phosphatic crust ( Fig. 30B ) that has regularly spaced growth lines, although they are less distinct than the ribs in the topotype material from western Mongolia. In addition, steinkerns from western Mongolia bear a regular, transverse, pustulouse ornament, which is probably a result of diagenetic phosphatisation of shell pores.

An apical tuft of acicular elements present between the phosphatized shell and internal mould (Figs. 29F 1, 30B 4) probably represents phosphatic casts of early diagenetic crystals of fibrous aragonite that grew in spaces between the inner surface of the shell and its sediment infill. Similar casts are observed in other parts of the internal moulds where they may have a different orientation, either parallel to or inclined to the surface of the mould. Such features are observed on internal moulds of maikhanellids (Fig. 32B 1, 34A 1, A 4), septa of hyoliths replicated by phosphate ( Fig. 53I ), as well as on the internal moulds of chancelloriid sclerites from Siberia and Laurentia (Kouchinsky et al. 2015a: fig. 34A).

Figures

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. 30. Mollusc Salanyella cf. costulata Missarzhevsky, 1981, from early Cambrian Medvezhya Formation, Kotuj River, western Anabar Uplift, Siberia, Russia; samples 3/22.5 (A) and K2/26 (B) from section 3. A. SMNH Mo182321, internal mould. B. SMNH Mo182322, internal mould with phosphatized shell. A1, apical; A2, subapical; A3, B2, lateral; B1, oblique supra-apical; B3, oblique subapical; B5, apertural views; B4, enlargement of apex with spiny structures on the internal mould. Scale bar 100 μm (B4) and 250 μm (A, B1–B3, B5).

Fig. 53. Orthothecid hyoliths Turcutheca sp. (A, B, D–G) and Khetatheca cotuiensis (Sysoev, 1959b) (C), from early Cambrian Emyaksin (A, B, F, H, I ), Medvezhya (C, D), and basal Kugda-Yuryakh (E, G) formations, Anabar Uplift, Siberia, Russia; samples 1/22 (D), section 1; K2/60 (E, G), section 3; 5 a/34.5 (F, H, I) and 5a/34.75 (A, B), section 96-5a; M424/10 (C), section M424. A, B, D–G. SMNH X5864, 5865 (A, B, respectively), SMNH X5867– 5870 (D–G, respectively). A, B, D, E, lateral views of calcium phosphatic internal moulds with transverse septae; F1, lateral view of phosphatic coating of tube fragment with two septae; F2, oblique transverse view of septum near aperture of fragment; G, transverse view of oval septum from apical side of internal mould. C. SMNH X5866, calcium phosphatic internal mould. C1, oblique lateral view of blunt apical end with septum; C2, lateral view of mould with two transverse septae at apical end. H, I. SMNH X5871, 5872, respectively, calcium phosphatic inner coatings of the hyolith conch wall and septae. Transverse views of rounded triangular septum from the apical (H) and apertural (I) sides. Scale bar 500 μm (A, B, I), 1 mm (C–H).