Aldanella attleborensis (Shaler and Foerste, 1888)

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 : 347-351

Aldanella attleborensis (Shaler and Foerste, 1888)

Figs. 20–22.

Material.—Over 1000 phosphatic internal moulds, including figured SMNH Mo160428, 182260–182272, from samples 1/46, 1/45, 1/29.5 (section 1, Fig. 4 ), and K2/20, K2/21, K2/22, K2/23, K2/24, K2/26, 3/10, 3/12, 3/12.2, 3/12.5 (section 3, Fig. 3), and 5/10, 5/10B, 5a/1, 5a/1.2, 5a/5, 5a/6, 5a/9 (sections 96-5 and 96-5a, Fig. 2 ), Medvezhya and Emyaksin formations, Anabar Uplift, Siberian Platform, Russia. Correlated with uppermost Fortunian Stage and lower part of Cambrian Stage 2.

Description.—Moderately expanding shells, up to 2.0 mm in diameter, consist of up to 2.5 whorls. Spire slightly protrudes above the surface of the last whorl. Lateral surface of the whorl is broadly rounded and passes gradually into flattened or slightly convex adapical and slightly concave umbilical surfaces of the whorl. Aperture irregularly elliptical in outline, width/height ratio 1.6–1.8. Ornamentation of the shell exterior (judging from the surface of external mould; Fig. 22A ) is represented by transverse growth lines. Protoconch with a diameter of 90–120 μm, not clearly separated in the available internal and external moulds (Figs. 20–22). Apex of internal moulds sometimes with polygonal to rounded impressions 20–40 μm in diameter (Figs. 20A 3, F 1, 21F; see also Kouchinsky 2000a, Ushatinskaya and Parkhaev 2005, Isakar and Peel 2007).

Remarks.—The specimens previously assigned to A. crassa by Kouchinsky (2000a: figs. 13A, B, L– R) are referred herein to A. attleborensis , following Parkhaev and Karlova (2011: 1187). Those authors also synonymized A. kunda (Öpik, 1926) ; A. rozanovi Missarzhevsky in Rozanov and Missarzhevsky, 1966 [in part]); A. yanjiahensis Chen, 1984 ; A. costata Missarzhevsky, 1989 ; and A. patelliforma Bokova, 1990 , with A. attleborensis (see discussion above and more inclusive synonymy in Landing 1988; Landing et al. 1989, 2013).

Stratigraphic and geographic range.— Uppermost Fortunian and Cambrian Stage 2 of Siberia, Avalonia, North and South China, and Baltica.

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. 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. 22. Mollusc Aldanella attleborensis (Shaler and Foerste, 1888), SMNH Mo182272 (cast of the outer shell surface) from early Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, eastern Anabar Uplift, Siberia, Russia; sample 5/10 from section 96-5. A. Adapical side with transverse sculpture. B. Protoconch enlarged. Scale bar 250 μm (A) and 125 μm (B).