Halkieria parva Conway Morris, 1990

Wrona, Ryszard, 2004, Cambrian microfossils from glacial erratics of King George Island, Antarctica, Acta Palaeontologica Polonica 49 (1), pp. 13-56 : 28-30

Halkieria parva Conway Morris, 1990 in Bengtson et al. 1990

Fig. 7.

Halkieria sp. ; Gaździcki and Wrona 1986: 611, fig. 7h.

Halkieria parva Conway Morris in Bengtson et al. 1990; Demidenko in Gravestock et al. 2001: 113, pl. 7: 1–3 [full synonymy].

Material.—A number of isolated sclerites and phosphatic internal moulds from erratic boulders Me30, 32, 33, and 66. Figured specimens, ZPAL V. VI /25S2; 26S13; 32S5; 35S22; 36S3; 37S2; 39S7; 55S55; 105S7; 106S2; 108S4.

Description.—Minute calcareous sclerites of Halkieria with left− and right−hand forms representing variable morphotypes: mainly palmate and cultrate. Other known forms (siculate and spiniform) are absent in the present Antarctic collection. Palmate sclerites are elongated triangular, asymmetric, with compressed blade. Their distal end tapers to a point. Base is flattened, with oval foramen in the centre and set at a steep angle to the blade (Fig. 7F, G). Outer surface of the sclerite is covered with longitudinal ridges (Fig. 7A–E) and transverse tuberculation which is more distinct at the lateral edge (Fig. 7F 2, M). Cultrate sclerites are more symmetric, long, knife−like in shape and strongly bent, tapering distally to a point. Base rhomboid with relatively small circular foramen in the centre. External ornamentation of cultrates is similar to that of palmates. There are a number of internal moulds with external wall partly preserved, which have large central canal and narrow and shorter lateral longitudinal canals (Fig. 7E, I, J) may also represent sclerites of H. parva . Steinkerns with a large central canal are abundant and characteristic for the Antarctic assemblage (Fig. 7I–L).

Remarks.—The preservation and highly variable sclerite forms make it difficult to classify the three morphocategories

Fig. 7. A–M. Halkieria parva Conway Morris. A. Broken cultrate sclerite in upper view, ZPAL V. VI /39S7, erratic Me66. B. Complete cultrate sclerite in Ą upper view, ZPAL V. VI /26S13, erratic Me30. C. Middle part of cultrate sclerite, ZPAL V. VI /108S4, erratic Me66; C 1, lateral view; C 2, ornamentation of upper surface. D. Broken cultrate sclerite, ZPAL V. VI /29S11, erratic Me66; D 1, blade preserved as internal mould of central and longitudinal lateral canals, with adhering sclerite wall, in upper view; D 2, ornamentation of upper surface. E. Steinkern of basal part of the sclerite with central and lateral canals, ZPAL V. VI /39S5, erratic Me66. F. Palmate sclerite, ZPAL V. VI /106S2, erratic Me66; F 1, oblique lower view; F 2, ornament, prominent tubercles at the margin.

G. Palmate sclerite with basal foramen in lower view, partly obscured by mineral coating, ZPAL V. VI /106S4, erratic Me66. H. Distal part of palmate broken sclerite in upper view, ZPAL V. VI /36S3, erratic Me32. I. Steinkern of proximal part of the central canal, palmate sclerite, ZPAL V. VI /32S5, erratic Me33. J. Steinkern of distal part of the central canal, palmate sclerite, ZPAL V. VI /55S55, erratic Me32. K. Steinkern of central blade sclerite, in lateral view, ZPAL V. VI /35S12, erratic Me32. L. Steinkern of distal part of cultrate sclerite, in upper view, ZPAL V. VI /37S2, erratic Me32. M. Distal part of palmate sclerite, showing broken lateral longitudinal canals, ZPAL V. VI /25S2, erratic Me33.

in the Antarctic assemblage and to define their position in the halkieriid scleritome. The mollusc−like shells were not identified in Antarctic SSF but it is possible that some enigmatic “smooth cones”, preserved as internal moulds and referred in this paper to problematic molluscs for lack of better diagnostic features (Fig. 25N), may represent poorly preserved internal moulds of coeloscleritophoran halkieriid cap−shaped shells.

Occurrence.—This species is restricted to the Early Cambrian (Atdabanian–Botomian) of the Kulpara Formation, Parara Limestone and Koolywurite Limestone Member, Yorke Peninsula, Stansbury Basin and Ajax Limestone, Flinders Ranges, Arrowie Basin , South Australia; allochthonous Early Cambrian (Botomian) boulders (Me30, 32, 33, and 66), King George Island, Antarctica.

Tommotiids

Order Tommotiida Missarzhevsky, 1970

Family Kennardiidae Laurie, 1986

Genus Dailyatia Bischoff, 1976

Type species: Dailyatia ajax Bischoff, 1976 .