Aetholicopalla, Conway Morris, 1990

Wrona, Ryszard, 2004, Cambrian microfossils from glacial erratics of King George Island, Antarctica, Acta Palaeontologica Polonica 49 (1), pp. 13-56 : 51-52

Aetholicopalla adnata Conway Morris, 1990 in Bengtson et al. 1990

Fig. 26D, E .

Aetholicopalla adnata Conway Morris; Demidenko in Gravestock et al. 2001: 86, pl. 12: 7, 8 [full synonymy].

Material.— Three specimens from erratic boulder Me32. Figured specimens, ZPAL V. VI/38 S1, 6 .

Description.—Spherical to subspherical, phosphatized microfossil about 600 µm in diameter. Normally double−walled globules, with walls connected by hollow pillars. The external wall is usually destroyed, showing height of the pillars (about 30–50 µm), which corresponds to the distance between the inner and outer wall, and remains of the external wall ( Fig. 26E ). The pillars opened on the outer surface of the globules, and are circular with a constant diameter about 30 µm ( Fig. 26D ). One specimen shows a flattened area corresponding to a zone of attachment to the substrate ( Fig. 26E ). The interior of the globules is filled with amorphous phosphates. The ornamentation of the external surface is not visible because of the poor preservation.

Remarks.—The vermiform tubules observed in the interior of the sphere (Conway Morris in Bengtson et al. 1990) may represent diagenetic replacement of a cyanobacterial filaments.

Occurrence.—Early Cambrian (Atdabanian/Botomian?), Montagne Noire, southern France; Early Cambrian (Atdabanian/ Toyonian), Kulpara Formation, Parara Limestone, Curramulka, Horse Gully, Yorke Peninsula and Ajax Limestone, Flinders Ranges , South Australia; Marianian strata (?uppermost Atdabanian–Botomian), Görlitz Syncline, eastern Germany ( Elicki and Schneider 1992; Elicki 1998); allochthonous Early Cambrian (Botomian) boulders (Me32), King George Island, Antarctica.

Problematic “smooth cones”—?coeloscleritophoran shell

Fig. 25N.

Material.—Sixteen phosphatic steinkerns from erratic boul− der Me33. Figured specimen, ZPAL V.VI/35S8.

Description.—Steinkerns of a cap−shaped, low−conical, slightly longitudinally elongate but rather wide shell. The apex is large, blunt, displaced posteriorly. The shell was apparently originally calcitc or aragonitic, with widely elliptical aperture. The surface of the internal mould is smooth without any trace of boundary between protoconch and teleoconch. No texture pattern or muscle scars have been observed on the surface moulds.

Remarks.—The shape of the moulds is very similar to that of the “ornamented cone”, Form A from the Parara and Ajax Limestones (Runnegar in Bengtson et al. 1990), which possibly represents some kind of mollusc−like coeloscleritophoran shell closely related to halkieriids (e.g., Qian and Bengtson 1989; Conway Morris and Peel 1990, 1995; Bengtson 1992). Occurrence.—Allochthonous Early Cambrian (Botomian) boulders (Me33), King George Island, Antarctica.

Figures

Fig. 26. A. Steinkern of initial part of Stapicyathus cera Debrenne archaeocyath cup, ZPAL Ac.I/53U7, erratic Me33.B, C. Problematic?tommotiid sclerite.B. Fragment of sclerite wall, ZPAL V.VI/49U4, erratic Me66. C. Fragment of sclerite wall, ZPAL V.VI/49U3, erratic Me66; C1, general view; C2, detail showing lamellar structure at the edge (arrowed). D, E. Aetholicopalla adnata Conway Morris. D. Specimen with external wall exfoliated, ZPAL V.VI/38S6, erratic Me32. E. Specimen ZPAL V.VI/38S1, erratic Me66; E1, oblique view, showing inner wall and tubules; E2, detail of surface of inner wall.