Philoxenella spiralis Vostokova, 1962

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 : 351

Philoxenella spiralis Vostokova, 1962

Fig. 24D, E.

Material.—22 internal moulds, including figured SMNH Mo182287 and 182288, from samples 1/29.2 (section 1, Fig. 4 ) and 3/22.5, K2/52, and K2/60 (section 3, Fig. 3), Medvezhya and basal Kugda-Yuryakh formations, Anabar Uplift, Siberian Platform, Russia. Correlated with Cambrian Stage 2.

Description.—Shell up to 1.3 mm in diameter, dextrally coiled, up to 1.5 moderately expanding whorls with a broadly oval cross-section. The inner shell surface (as replicated by the available internal moulds) is smooth.

Remarks.—Internal moulds of Philoxenella are morphologically identical to those of Barskovia Golubev, 1976 (Fig. 24A–C, F, G), although the latter is sinistral (see below). Parkhaev (2007a, b) tentatively regarded them as dextral and sinistral variants of the same species and assigned them to the family Khairkhaniidae Missarzhevsky, 1989 . This attribution is corroborated by probably similar microstructures of the conch, which is perforated by canals (Parkhaev 2006, 2007b). Philoxenella differs from Aldanella , which lacks canals in its conch walls, in being relatively loosely coiled and with lower rate of shell expansion.

Stratigraphic and geographic range.— Cambrian Stage 2 of the Siberian Platform and probably Avalonia (see Landing 1996: fig. 5b, c).

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.