Mongolitubulus spinosus (Hinz, 1987)

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 : 425

Mongolitubulus spinosus (Hinz, 1987)

Fig. 61B .

Material.—Single fragment of calcium phosphatic spine with broken off tip, SMNH Ar75002, from sample 19/31.75, Erkeket Formation, Khorbusuonka River, Siberia, Russia. Toyonian stage (correlated with the Cambrian Stage 4).

Remarks.—Hollow spine fragment nearly circular in cross-section and covered with longitudinally extended scaly polygons with raised ends pointed towards the apex of the spine. The specimen is 0.8 mm long and 0.2 mm wide and similar to the spines described from the Botoman Stage, Emyaksin Formation of the Anabar Uplift ( Kouchinsky et al. 2015a, see description therein). Currently available material extends the stratigraphic range of Mongolitubulus spinosus into the Toyonian stage (Cambrian Stage 4)..

Stratigraphic and geographic range.—Cambrian Series 2, Siberian Platform ( Russia) and Britain.

Mongolitubulus reticulatus Kouchinsky, Bengtson, Clausen, Gubanov, Malinky, and Peel, 2011

Fig. 61C .

Material.—Single calcium phosphate apical fragment of a specimen SMNH Ar75003, from sample 19/3.25, Erkeket Formation, Khorbusuonka River, Siberia, Russia. Lower Botoman stage (correlated with the Cambrian Stage 4).

Remarks.—Short apical fragment of a hollow tubular spine with nearly circular cross-section. Outer surface covered with subdued longitudinally extended polygons. Tip of the spine recurved and pointed. The specimen ca. 0.7 mm long and ca. 0.2 mm in diameter. Mongolitubulus reticulatus is different from Mongolitubulus spinosus (see above) in ornamentation and in having a bent apical part.

Stratigraphic and geographic range.— Lower Botoman stage (correlated with the Cambrian Stage 4)–Wuliuan Stage (type material from the Kuonamka Formation, Anabar Uplift, Kounamkites Zone, Amgan stage , see Kouchinsky et al. 2011), Siberian Platform, Russia .

Figures

Fig. 61. Lobopodian (A) and bradoriid (B–D) calcium phosphatic fragments, from the lower Cambrian Erkeket Formation, Khorbusuonka River (B, C) and Tyuser (D), and Sekten (A) formations, lower reaches of the Lena River, Siberia, Russia; samples 19/3.25 (C), 19/31.75 (B), 21/57.75 (D), and 22/67 (A). A. Microdictyon robisoni Bengtson, Matthews, and Missarzhevsky, 1986, sclerite, SMNH X11294. B. Mongolitubulus spinosus (Hinz, 1987), spine, SMNH Ar75002. C. Mongolitubulus reticulatus Kouchinsky, Bengtson, Clausen, Gubanov, Malinky, and Peel, 2011, spine, SMNH Ar75003. D. Cambria sibirica Neckaja and Ivanova, 1956, carapace, SMNH Ar75001; D1, anterior view; D2, D3, dorsal view. Scale bar: 250 µm A–C) and 1.25 mm (D).