Cupitheca holocyclata ( Bengtson, 1990b )

Malinky, John M. & Skovsted, Christian B., 2004, Hyoliths and small shelly fossils from the Lower Cambrian of North-East Greenland, Acta Palaeontologica Polonica 49 (4), pp. 551-578 : 569-570

Cupitheca holocyclata ( Bengtson, 1990b)

Fig. 12 .

Actinotheca holocyclata Bengtson, 1990b: 204 , figs. 134–136.

Cupittheca holocyclata ( Bengtson, 1990b) ; Demidenko 2001: 97, pl. 9: 1a, b.

Cupitheca holocyclata ( Bengtson, 1990b) ; Wrona 2003: 200, fig. 11A–F, G 3.

Holotype: South Australian Museum , Adelaide SAMP30845 .

Material.— MGUH 27114–27118 and 59 additional specimens from GGU samples 314807, 314835, 314904, 314906, 314908, 314918, 314919, 314931 and 314933.

Description.—Straight to slightly tapering tubular conch with circular cross−section; apical region with shallow though well−developed constriction that separates the septum−like wall from remainder of conch. Septum convex toward apex. Constriction may be either perpendicular to, or at an oblique angle to the longitudinal axis of the conch. Wall of conch seems to consist of distinct tubular or rod−like structure. Shell with very faint, widely spaced, shallow depressions with spaces in between equal to width of 2–5 depressions; areas between depressions are flat or slightly concave.

Remarks.—This taxon ordinarily is represented by short segments whose length may be only several times the width. Most specimens of Cupitheca holocyclata illustrated by Bengtson (1990b: fig. 134I, P) possess coarse annular rings, but in some the rings are much finer, resembling those on the specimens recorded herein. Thus these specimens are assigned to C. holocyclata because of the generally fine transverse sculptural elements that completely encircle the shell. Cupitheca hemicyclata has much coarser elements though only one on side of the shell, and C. clathrata ( Bengtson, 1990b) has a distinctive cancellate ornamentation not seen in any material from Greenland.

Stratigraphic range and distribution.—Lower Cambrian, Australia, Antarctica, and North−East Greenland.

Figures

Fig. 12. Cupitheca holocyclata (Bengtson, 1990b). A. MGUH 27114; A1, apical view showing septum; A2, lateral view showing shell with ornamentation. B. MGUH 27115; B1, B2, oblique views of apical septum with structure of shell wall visible in B2. C. MGUH 27116. From GGU sample 314809. Lateral view showing apical septum. D. MGUH 27117; D1, lateral view showing apical septum; note oblique angle of constriction; D2, enlarged view of apical septum and constriction. E. MGUH 27118, lateral view showing apical septum. All specimens except C from GGU sample 314807. Scale bars 0.2 mm except B2 which is 0.1 mm.