Hadimopanella knappologica (Bengtson, 1977)

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 : 419-421

Hadimopanella knappologica (Bengtson, 1977)

Fig. 57 .

Material.—Hundreds of individual calcium phosphate sclerites, including SMNH X11245–11256, from samples 19/5.5 and 20/1B, Erkeket Formation, Khorbusuonka River, Siberia, Russia. Lower Botoman stage (correlated with the Cambrian Stage 4).

Description.—Disk-like, 100–300 μm in diameter, circular to broadly oval sclerites with a gently convex smooth lower side and the upper side representing the conical surface capped with a flattened nodular face. The latter includes numerous tubercles (nodes), ca. 10 μm in diameter. The outermost tubercles form a ring, whereas other tubercles are less orderly distributed inside the ring. The conical surface carries radially oriented folds situated between the outer margin of sclerite and the outermost ring of tubercles of the nodular face.

Remarks.—The holotype of the species shows numerous nodes on the nodular face and distinct radial folds on the conical surface (Bengtson 1977). The number of nodes can vary but presence of radial folds remains a diagnostic feature of the species. Type material occurs in the Judomia –Uktaspis ( Prouktaspis ) Zone, Atdabanian Stage, Perekhod Formation, middle Lena River (Astashkin et al. 1991). Previously described range of the fossil from the Emyaksin Formation is correlated with the lower Judomia –Uktaspis ( Prouktaspis ) Zone, Atdabanian stage– Calodiscus –Erbiella Zone, lower Botoman stage. Forms described by Kouchinsky et al. (2011: fig. 32) from the Kounamkites Zone, Amgan stage (correlated with the Wuliuan Stage) are reinterpreted herein as Hadimopanella sp. (see below). Only those sclerites figured by Kouchinsky et al. (2015a: fig. 57G–N) from the Judomia –Uktaspis ( Prouktaspis ) Zone, Atdabanian stage with diagnostic radial folds are interpreted herein as H. knappologica . Those with a single apical tip ( Kouchinsky et al. 2015a: fig. 57B, E) in the middle of conical side are similar to H. apicata Wrona, 1982 , from the upper Stage 3– Stage 4 of Gondwana and Laurentia. The latter species has sclerites up to 150 μm in diameter and up to four nodes in larger specimens.

Stratigraphic and geographic range.— Judomia –Uktaspis ( Prouktaspis ) Zone, Atdabanian stage– Calodiscus –Erbiella Zone, lower Botoman stage (correlated with the upper part of Cambrian Stage 3–lower Cambrian Stage 4); Siberian Platform.

Hadimopanella foveata Kouchinsky sp. nov.

Fig. 58 .

Zoobank LCID: urn:lsid:zoobank.org:act:1BC57845-B56E-467B-9AC6-BE6E97BD5BC9

Etymology: From Latin fovea, pit, refers to the pitted upper face of sclerites.

Siberia, Russia. Toyonian–lower Amgan stages (correlated with the Cambrian Stage 4).

Diagnosis. —Almost circular disk-like calcium phosphatic sclerites with a flattened circular upper face bearing closely situated pits. The latter are arranged in a circlet at the margin of the upper face.

Description.—Disk-like, almost circular sclerites, 100– 200 μm in diameter, with a gently convex smooth lower side. The upper side represents a conical surface capped with a flattened circular upper face with closely situated pits, ca. 10 μm in diameter. The outermost part of the upper face represents a ring of 5–12 pits, whereas pits of the same type inside the ring are less orderly distributed. Conical surface carries radially oriented furrows and intervening folds situated at the margin of sclerite and granulation surrounding the upper face. The number of pits increases with size of sclerites.

Stratigraphic and geographic range.—Toyonian–lower Amgan stages (correlated with the Cambrian Stage 4), Siberian Platform, Russia.

Figures

Fig. 57. Paleoscolecid Hadimopanella knappologica (Bengtson, 1977) from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; samples 19/5.5 (A–F) and 20/1B (G–L). A–L. Disarticulated sclerites, SMNH X11245–11256, respectively.A, B2, D2, E–K, apical view; B1, C, D1, L, oblique apical view. Scale bar 100 µm. Type material: Disarticulated calcium phosphatic sclerites: Holotype Type horizon: Erkeket Formation, ca. 30 m below the Kuonamka For- SMNH X11257 (Fig. 58A) and paratypes SMNH X11258–11260, mation, Toyonian Stage (correlated with the Cambrian Stage 4). 11262–11265 (Fig. 58B–D, F–I), from the type locality and horizon. Type locality: Locality 19/31.75 (71°28.8’N, 123°50.0’E) on the left Material.—Several hundred calcium phosphate sclerites, in bank of the Khorbusuonka River, ca. 20 km downstream of the mouth addition to the type series, from samples 19/31.75, 19/33, of the Mattaia River, northern Siberia, Russia. 19/40, 19/43.25, 19/46.5, 20/5B, 20/6B, Khorbusuonka River,

Fig. 58. Paleoscolecid Hadimopanella foveata sp. nov., from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; samples 19/31.75 (A–D, F–I), 19/43.25 (E, J, N, O), 20/5B (L, M), and 20/6B (K). A–O. Disarticulated sclerites, SMNH X11257–11268, 11352–11354, respectively.A, holotype. A1, B–D, G, H, O, oblique apical view; A2, E, F, I–N, apical view. Scale bar 100 µm.