Hexactinellida Schmidt, 1870

Clausen, Sébastien & Álvaro, J. Javier, 2006, Skeletonized microfossils from the Lower-Middle Cambrian transition of the Cantabrian Mountains, northern Spain, Acta Palaeontologica Polonica 51 (2), pp. 223-238 : 226

Class Hexactinellida Schmidt, 1870

Order and family uncertain

Fig. 3B–D.

Material. —More than 100 specimens preserved as secondary phosphatized spicules or phoshatic steinkerns in the Middle Cambrian “Beleño” facies, sections Cr 1 to Cr 4.

Description.—Siliceous hexactine spicules, exhibiting regular triaxons with six rays at right angles displaying the original spicule symmetry of hexactinellids; size variable, from about 0.2 to 0.8 mm in diameter; rays long and inflated with rounded ends; basal diameter of the ray 80–100 µm; in some specimens, the rays radiate from an inflated spherical center reaching 350–400 µm in diameter ( Fig. 3D). Normally, the rays are of approximately equal length, but in some specimens a few rays are reduced (probably because of erosion) and, in others, one or two rays reach almost double length. When broken, most of the rays show central canals, and hollow spherical center ( Fig. 3D).

Remarks.—Similar inflated hexactines (with inflated rays) have been reported from the Middle Cambrian of Australia ( Mehl 1998), and the Upper Cambrian of Argentina ( Heredia et al. 1987).