Hexactinellida, Schmidt, 1870

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

Hexactinellida indet.

Fig. 5D, E, G.

Material.—Nine disarticulated spicules of tetractine up to hexactine, preserved as phosphatic replacement from etching residues of limestone erratic boulders Me33, 52, and 66. Figured specimens, ZPAL Pf. V /21S21; 39S15; 25S4.

Description.—There are four−rayed spicules (Fig. 5D) oriented in one plane (stauracts) up to six−rayed spicules (hexactines), which are often asymmetric (Fig. 5E, G) with aberrantly developed rays. The spicule surfaces are coarse, when corroded or coated by minearl grains (Fig. 5E, G). The spicule rays tapering to a point, but rays usually have broken ends. They are preserved as recrystallized steinkerns, possibly phosphatized.

Remarks.—The antarctic forms are most similar to the South Australian spicules from Horse Gully and Curramulka, Parara Limestone, and Mount Scott Range, Ajax Limestone discussed and figured by Bengtson (in Bengtson at al. 1990: fig. 15). These spicules seem to be the most common disarticulated sponge spicules in the Cambrian rocks from several localities around the world (e.g., Hinz 1987; Kruse 1990; Bengtson et al. 1990; Brock and Cooper 1993; Zhang and Pratt 1996; Dong and Knoll 1996; Mehl 1998; Krautter 2002).

Occurrence.—Allochthonous Early Cambrian (Botomian) boulders (Me33, 52 and 66), King George Island, Antarctica.