Parkula, Bengtson, 1990

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 : 559-560

Parkula ? sp.

Fig. 4C, D .

Material.—MGUH ZZZ13−27095 and ten additional specimens from GGU sample 314835.

Description.—Low and broad conical shield of generally low profile, grading into shallow and poorly defined furrows with no identifiable rooflets; summit low and indistinct; cardinal shield low, curving by summit to become convex toward conical shield. Interior with cardinal processes having broad base that originates at edges of operculum and progressively expands to form wide, blade−like processes at center of cardinal shield that have blunt, rounded terminations with very slightly curvature and indentation at distal end of processes. Operculum monoclaviculate, and cardinal processes diverge at angle of 80°. Exterior of operculum smooth.

Remarks.—This taxon is known from two specimens in which the edge of the conical shield is broken, and no details remain of the exterior. The most distinctive feature is the massive cardinal processes with the broad base that attaches them to the cardinal shield. The seemingly small size of the cardinal shield itself is worthy of note, although the amount removed by breakage cannot be known with certainty. These features clearly distinguish this taxon from all others reported by Bengtson (1990a) and Demidenko (2001) from Australia, and no Early Cambrian opercula of similar morphology have been reported from elsewhere.

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

Figures

Fig. 4. A, B. Parkula bounites Bengtson, 1990a. A. MGUH 27092; A1, exterior of operculum from above; A2, lateral view of operculum with conical shield to right. B. MGUH 27093, interior of operculum with cardinal processes and clavicles (top of the picture). C, D. Parkula? sp. C. MGUH ZZZ13; C1, exterior of operculum from above; C2, view from cardinal shield showing enlarged cardinal processes. D. MGUH 27095; D1, exterior of operculum from above; D2, lateral view of operculum with conical shield to right; D3, view from cardinal shield showing enlarged cardinal processes. E–I. Hyptiotheca karraculum Bengtson, 1990a. E. MGUH 27096; E1, exterior of operculum from above; E2, lateral view with conical shield to right, showing no change in angle between conical and cardinal shields; E3, view from edge of conical shield.F. MGUH 27097; F1, oblique view from above of exterior of operculum from above; F2, view from edge of conical shield; F3, exterior of operculum from above. G. MGUH 27098; G1, oblique view from above of exterior of operculum from above; G2, lateral view of operculum with conical shield to right, showing abrupt change in angle between cardinal and conical shields. H. MGUH 27099; H1, lateral view of operculum with conical shield to right, showing abrupt change in angle between cardinal and conical shield; H2, exterior of operculum from above.I. MGUH 27100, interior view showing weakly developed depressions along edges only, corresponding to rooflets on exterior. All from GGU sample 314835. Scale bars 0.2 mm.