Purella cristata Missarzhevsky, 1974

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 : 364-369

publication ID	https://doi.org/ 10.4202/app.00289.2016
persistent identifier	https://treatment.plazi.org/id/03AD87A8-FFAE-6D1D-FCB9-FCEE645E81E3
treatment provided by	Felipe
scientific name	Purella cristata Missarzhevsky, 1974
status

Treatment

Purella cristata Missarzhevsky, 1974 View in CoL

Figs. 35.

Material.—Over80internal moulds with fragments of phosphatized shells,including figured SMNH Mo182343‒182348, from samples 1/29.2, 1/29.5, 1/50 (section 1, Fig. 4 View Fig ), K2/12, K2/13, K2/25, K7, 3/0, 3/0.1, 3/6.5, 3/12, 3/12.2 (section 3, Fig. 3), Medvezhya and Kugda-Yuryakh formations, western Anabar Uplift, Siberian Platform, Russia. Correlated with upper Fortunian and lower part of Cambrian Stage 2.

Description.—Shell low to high conical, with blunt apex slightly inclined but not projecting beyond the apertural margin. Aperture wide oval to broadly rounded rhomboid, with narrower subapical part, length/width ratio 1.5–1.8. Supra-apical side of the shell may bear a broad longitudinal buttress between apex and apertural margin. Shell composed of comarginally elongated scales.

Remarks.— Purella cristata Missarzhevsky, 1974 , was first described from limestones (sample M71-2/66 collected by Vladimir V. Missarzhevsky) in the upper Kessyusa Formation of the Olenyok Uplift. Purella cristata is more laterally compressed than P. antiqua and has a more elongated shape (Fig. 35). Parkhaev (in Varlamov et al. 2008: pl. 12: 3a, 3b; in Rozanov et al. 2010: pl. 26: 1) described internal moulds of P. cristata with preserved scales. Parkhaev and Demidenko (2010) suggested its synonymy with P. dzhandica Yermak in Pel’man et al., 1990, and P. rudavskae Vasil’eva, 1998, from Siberia. The taxonomy of Purella

Fig. 32. Mollusc Purella antiqua ( Abaimova, 1976) , from early Cambrian Nemakit-Daldyn Formation, western Anabar Uplift, Siberia, Russia; sample → 1282, section 2. A. SMNH Mo182326; A 1, partial external mould of shell; A 2, enlarged apical area shows radial microtubules and circumferential scales.

B. SMNH Mo182327, internal mould; B 1, oblique lateral; B 2, upper views. C. SMNH Mo182328, lateral view of internal mould separated by a narrow slit (arrowed) from external phosphatic coat of a dissolved shell. D. SMNH Mo182329, upper view of internal mould that underlies external phosphatic coating of a dissolved shell. E. SMNH Mo182330, internal mould; E 1, subapical; E 2, upper views. Scale bar 125 μm (A 2), 250 μm (B–E), 500 μm (A 1).

was discussed by Parkhaev and Demidenko (2010) and Devaere et al. (2013). The co-occurrence of more elongate forms comparable with P. arcana (Val’kov 1987: pl. 16: 4; Fig. 35A, herein) with those identified in this report as P. cristata from sample 1/50 (Kotuj River, section 1; Figs. 4 View Fig , 35) suggests that P. arcana Val’kov, 1987 is probably synonymous with P. cristata . In P. gracilis Zhegallo in Voronin et al., 1982, hollow spines are present in the subapical area ( Devaere et al. 2013), as in P. squamulosa Qian and Bengtson, 1989 (i.e., Yang et al. 2014). These spines are unknown in other species and in our material. Parkhaev and Demidenko (2010) followed Missarzhevsky (1989) and synonymized Rozanoviella Missarzhevsky, 1981 , from the Terreneuvian beds of western Mongolia with Purella . Parkhaev and Demidenko (2010) also concluded a probable synonymy of R. atypica Missarzhevsky, 1981 (Missarzhevsky 1981: text-fig. 2, pl. 3: 9; Esakova and Zhegallo 1996: pl. 20: 4), with Purella antiqua based on general morphology and shell structure ( Abaimova 1976: pl. 20: 1, 4; Kouchinsky 2000a: fig. 3).

Stratigraphic and geographic range.— Fortunian Stage and lower part of Cambrian Stage 2; South China and Siberian Platform, probably western Mongolia.