Eiffelia araniformis (Missarzhevsky, 1981)

Wrona, Ryszard, 2004, Cambrian microfossils from glacial erratics of King George Island, Antarctica, Acta Palaeontologica Polonica 49 (1), pp. 13-56 : 22-24

Eiffelia araniformis (Missarzhevsky, 1981)

Fig. 5H.

Eiffelia araniformis (Missarzhevsky) ; Bengtson in Bengtson et al.

1990: 27, figs. 12, 13 [full synonymy].

Material.— Eight specimens from etching residues of limestone erratic boulder Me66. Figured specimen, ZPAL Pf. V/38 S16.

Description.—Spicules with six slender rays, and diverging at 60° in one plane. The spicule surfaces are smooth, and the rays tapering to a point, but usually have broken ends. The rays are set at a low angle to their common plane, and thus form a concave and convex side of the spicule (Fig. 5H). A central ray may occur on the convex side, perpendicularly to the hexiradiate plane.

Remarks.—The antarctic forms are most similar to the South Australian ones from Horse Gully and Curramulka, Parara Limestone, and Mount Scott Range, Ajax Limestone discussed and figured by Bengtson (in Bengtson at al. 1990: fig. 13C). Isolated spicules of Eiffelia sp. have recently been recorded also in Middle Cambrian phosphatic sediments of the Georgina Basin ( Mehl 1998).

Occurrence.—Allochthonous Early Cambrian (Botomian) boulders (Me66), King George Island, Antarctica.

? Heteractinida indet.

Fig. 5C, F.

Material.—A dozen isolated megasclere spicules of polyactine (?octactine) forms, preserved as phosphatic sheaths from etching residues of limestone erratic boulders Me32and 66. Figured specimens, ZPAL Pf.V/108S16; 29U13.

Description.—There are polyaxial spicules, which are usually asymmetric octactines (Fig. 5C) with aberrantly developed rays, and some that are perfectly hexiradially symmetric (Fig. 5F), with six rays in a plane, separated at 60° from each other, and addition of two rays at right angles to the plane (octactine). The spicule surfaces are smooth or coarse, when coated by minearl grains. The spicule rays tapering to a point, but rays usually have broken ends. The spicules were probably initially calcareous, solid rayed, now dissolved and preserved as phosphatic sheaths, with large hollows along ray axes. Such spicules are common in calcareous heteractinid sponges ( Rigby 1983; Pickett 2002).

Remarks.—The antarctic forms are similar to the South Australian spicules from Horse Gully and Curramulka, Parara Limestone, and Mount Scott Range, Ajax Limestone dis−

Fig. 5. A, B. Sponge spicules of Dodecaactinella cf. cynodontota Bengtson and Runnegar. A. Fragment of phosphatized spicule, ZPAL Pf.V/35S23, erratic Ą Me32; B. Phosphatized broken triactine spicule, ZPAL Pf.V/35S26, erratic Me32. C, F. Heteractinid spicules. C Phosphatic sheath of broken polyactine, ZPAL Pf.V/108S16, erratic Me66; C 1, oblique view; C 2, axial view of the same. D −E, G. Hexactinellid spicules. D. Phosphatized tetractine, ZPAL Pf.V/ 21S21, erratic Me52. E. Phosphatized hexactine in lateral views, ZPAL Pf.V/39S15, erratic Me66. F. Phosphatic sheath of broken polyactine,?oxyaster, ZPAL Pf.V/29U13, erratic Me32. G. Phosphatized hexactine, ZPAL Pf.V/25S4, erratic Me33. H. Eiffelia araniformis (Missarzhevsky) 6−rayed spicule, with 7th central ray, ZPAL Pf.V/38S16, erratic Me66. I. Broken chancelloriid sclerite of Archiasterella ? sp., ZPAL V.VI/37S5, erratic Me32. J. Allonnia ex

gr. A. tripodophora Doré and Reid , damaged sclerite, covered with mineral matter, ZPAL V.VI/38S19, erratic Me32. K. Allonnia ? cf. tetrathallis (Jiang) , broken sclerite ZPAL V.VI/36S7, erratic Me33. L. Phosphatic overgrowth of Radiocyathus ? sp. cf. R. minor Bedford and Bedford, ZPAL V.VI/40S9, erratic Me66; L 1, inner surface view; L 2, outher (external) surface of the same rosette; L 3, the same in oblique lateral view.

cussed by Bengtson (in Bengtson at al. 1990), and to the forms from the early Middle Cambrian Tindall Limestone of the Daly Basin, Northern Territory, Australia ( Kruse 1990), These spicules seem to be common isolated sponge spicules in the Cambrian rocks (e.g., Hinz 1987; Kruse 1990; Bengtson et al. 1990; Mehl 1998).

Occurrence.—Allochthonous Early Cambrian (Botomian) boulders (Me32, 66), King George Island, Antarctica.