Parakorilithes mammillatus He and Pei

Kouchinsky, Artem, Alexander, Ruaridh, Bengtson, Stefan, Bowyer, Fred, Clausen, Sébastien, Holmer, Lars E., Kolesnikov, Kirill A., Korovnikov, Igor V., Pavlov, Vladimir, Skovsted, Christian B., Ushatinskaya, Galina, Wood, Rachel & Zhuravlev, Andrey Y., 2022, Early-middle Cambrian stratigraphy and faunas from northern Siberia, Acta Palaeontologica Polonica 67 (2), pp. 341-464 : 413-414

Parakorilithes mammillatus He and Pei in He et al., 1984

Fig. 53 .

Material.—Several phosphatised conchs, including figured SMNH X11223–11225, and 11351, from 19/10.25 and 19/11.75; Khorbusuonka River, Erkeket Formation, Siberia, Russia. Lower Botoman stage (correlated with the lower part of Cambrian Stage 4).

Description.—Moderately expanding conch gently curved in sagittal plane, with an oval aperture showing protruding dorsal and ventral margins (lips). The dorsal lip is longer than the ventral one. Ventral and dorsal sides of the conch covered with growth lines curved towards the aperture following curvature of the lips. Laterally, the growth lines show angulation between the ventral and dorsal curves. Initial part rounded blunt slightly separated from the main conch by a shallow constriction.

Remarks.— Pan et al. (2019) emended diagnosis of the genus and considered the species as a senior synonym to Hyptiotheca karraculum Bengtson in Bengtson et al. 1990. Bengtson et al (1990) interpreted the dorsal side in this form as shorter than the ventral one and the sagittal ventrally directed curvature of the conch. The curvature is herein reinterpreted as the normal one, dorsally directed, but with the dorsal lip longer than the ventral one.

Stratigraphic and geographic range.—Series 2 of Australia Bengtson et al. 1990; Gravestock et al. 2001), Antarctica Wrona 2003), North China ( Pan et al. 2019), and Laurentia Malinky and Skovsted 2004).

Figures

Fig. 53. Hyolith conchs Parakorilithes mammillatus He and Pei in He et al., 1984, from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; sample 19/10.25. A–D. Phosphatised conchs, SMNH X11223–11225, and 11351 respectively. B1, C1, dorsal; B2, D2, lateral; B3, oblique lateral; C2, B4, apertural; and D1, oblique apertural views. Scale bar 250 µm.