Acanthambonia sp.

Hansen, Jesper & Holmer, Lars E., 2011, Taxonomy and biostratigraphy of Ordovician brachiopods from northeastern Ny Friesland, Spitsbergen 3076, Zootaxa 3076 (1), pp. 1-122 : 80-81

Acanthambonia sp.

Pl. 21, Fig. 16; Pl. 22, Figs. 1–3

Material. One fragment of a dorsal valve from sample F5316 and five fragments from samples F5217, JH-95 and JH-136. The figured specimens are TSGF 16864, TSGF 16865 and TSGF 16988.

Description. Growth lines with small tubercles on proximal part of postlarval shell, developing into dense lamina with abundant short and straight hollow spines distally. Low spines on one fragment impressed as furrows in shell-matrix below. Spines dominantly subequal, but a few much-thinner spines occur scattered among the normal spines distally.

Dorsal valve small and slightly convex, with shallow sulcus and broadly rounded posterior margin. Pseudointerarea short.

Remarks. The inadequate sample makes detailed comparisons with other species impossible. Based on the available material, it is not possible to verify if the specimen from the Olenidsletta Member (Pl. 22, Figs. 1–2 ) is the same or another species than the others. However, at present we keep them together.

Occurrence. 97 m above base of Olenidsletta Member (one specimen) and 39 and 67 m above base of Profilbekken Member (three specimens), Valhallfonna Formation , Basissletta in northeastern Ny Friesland, Spitsbergen .

Figures

FIGURE 1 Locality maps of the Svalbard Archipelago. a) Locations of sites yielding Lower Palaeozoic fossils mentioned in this paper. b) Geological map of the Basissletta plain, northeastern Ny Friesland; redrawn from Fortey & Bruton (1973). The base map is based on aerial photos made available by the Norwegian Polar Institute and on field observations made by the authors in 2008.

FIGURE 2 Stratigraphical ranges and diversity of brachiopod species at Basissletta, Spitsbergen, and relative sea levels and percentages of linguliform brachiopods in the total brachiopod fauna. White shading in the last graph indicates stratigraphical intervals without brachiopods. Thicknesses of units are according to Fortey & Bruton (1973). Lithological log and sea level curve are from Hansen & Holmer (2010).

FIGURE 3 Rose histograms for the umbonal orientation of the large brachiopod Ectenoglossa? oviforma sp. nov. found in the Olenidsletta Member, Valhallfonna Formation. a) Histogram of 58 specimens from 88 m above the base of the member. b) Histogram of 13 specimens from 94 m above the base of the member.