Kiwetinokia sp.

Beresi, Matilde Sylvia, Botting, Joseph P., Palafox, Juan J. & Buitrón Sánchez, Blanca E., 2017, New reticulosan sponges from the middle Cambrian of Sonora, Mexico, Acta Palaeontologica Polonica 62 (4), pp. 691-703 : 699

Kiwetinokia sp. ?

Fig. 6M .

Material.—USDG 001–5, several isolated triradiate spicules from the middle Cambrian at the Cerro El Mogallón, Arivechi, Sonora.

Description.— Occasional triradiate or Y-shaped spicules occur in the assemblage, associated with dissociated stauractines of diverse sizes. Triactine-like prodiaene spicules have presumed proximal rays 5.5 mm long, and two somewhat longer, presumed distal rays, with maximum ray lengths of 10.3 mm (mean = 5.5 mm). Basal ray diameter in largest spicules is 0.40–0.50 mm.

Remarks.— Walcott (1920) proposed the genus Kiwetinokia , designating the new species K. utahensis as the type, to include clusters of scattered spicules in the absence of any articulated material. Similar disarticulated remains from Little Métis, Quebec ( Dawson and Hinde 1889) were reassigned to the genus from Hyalostelia . There is thus a severe risk that the spicule assemblage is itself not natural, although the name is effectively tied to the most distinctive spicules, consisting of triradiate spicules, Y-shaped spicules resembling demosponge prodiaenes, and spicules with helically twisted rays. Walcott (1920) considered the cruciform spicules associated with the more distinctive morphologies to be characteristic of species included in that genus. Fink and Rigby (2004) and other authors considered that the twisted spicular rods may be part of the basalia of the co-occurring (at Little Métis) Palaeosaccus Hinde, 1893 . It is therefore possible that Kiwetinokia may be a junior synonym of Palaeosaccus , although the full range of distinctive spicules included in the genus is unlikely to be accommodated in that way. Until articulated remains are discovered, the genus remains recognisable as a spicule assemblage.

In the Arivechi material the spirally twisted triradiate spicules are not yet known. However , from the early Cambrian of the Caborca , northern Sonora, McMenamin (2008) described one spicule of this type, assigning it to Kiwetinokia .

Figures

Fig. 6. Isolated spicules and associated fossils from the middle Cambrian El Mogallón Formation at Cerro El Mogallón, Sonora, Mexico. A, B, D. Spicules exhibiting 90° angles between four coplanar rays, and a vestigial fifth perpendicular ray, preserved as a central boss (arrows), indicating a geometry of three orthogonal axes. C. Assemblage of diverse disarticulated spicules. E. Stauractine with three smooth equal long rays and the forth longer. F, G. Fragments of possibly semi-articulated skeleton composed of stauractines and monaxons, with traces of a sub-regular, perhaps quadruled array. H. Fine monaxial spicules. I. Unidentified agnostoid trilobite and a typical cruciform stauractine. J. Possible anchoring spicule with two strongly recurved rays. K. Ptychagnostus atavus (Tullberg, 1880). L. Isolated, partial, presumed root tuft with two long parallel monaxons. M. USDG 001, triactine Kiwotinokia) and a long isolated monaxon; the arrow points to a possible ovoid sponge.