Fig. 76 in Early-middle Cambrian stratigraphy and faunas from northern Siberia

Fig. 76. Spicules of Nabaviella sp. from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; samples 20/1B (A) and 19/5.5 (B–D). A. Calcium phosphatic mould of the spicule with the proximal (proximal part of the spicule) shaft and a terminal knob (arrowed in A2) at the opposite surface of the distal disc (distal part of the spicule) consisting of radiating rays (A1), SMNH Sp11495. B. Calcium phosphatic coatings incompletely replicating the proximal surface of the disc with basal parts of the rays and internal axial canal in the spicule, SMNH Sp11496. B1, plain view; B2, lateral view. C. Internal mould of the proximal shaft with terminal proximal swelling (arrow), SMNH Sp11497. D. Calcium phosphatic internal mould of the axial canal and internal cavity of the distal disc and terminal knob (arrowed in D1), SMNH Sp11498. Scale bar: 125 µm (B) and 250 µm (A, C, D).