Valhalloceras floweri Evans & King 1990

Valhalloceras floweri Evans & King, 1990

Figs 5H–N, 6C, 8B, 50B

Valhalloceras floweri Evans & King, 1990: 628–629, pl. 1 figs 5–11, text-fig. 3.

As for genus, by monotypy.

Specimen FMNH-P30343 from Profilstranda section, adjacent to Hinlopenstretet, Spitsbergen, bed PO 123.3, 120.3 m above base of Olenidsletta Member, V2 a trilobite zone, and specimens FMNH-P30340, P30346, P30348, and P30350 from bed PO 131, 128 m above base of Olenidsletta Member, V2 b trilobite zone, Blackhillsian, Floian.

Specimen FMNH-P30343 is the externally most complete specimen (Fig. 5H–I). It is a slightly crushed curved conch with a length of more than 30 mm which grows from 7.3 mm in height and 9.5 mm in width to 10 mm in height and 14 mm in width at a length of 15 mm (width expands with 17°, height with 10°). The cross section is depressed (rW: 1.3–1.5) and nearly elliptical at the adapical end of the specimen. The surface is ornamented with irregularly spaced fine growth lines, which run almost transversally at the ventral side and form a shallow broad sinus at the dorsal side. The internal characters of specimen FMNH-P30343 are not preserved. Three specimens with similar relative conch shape (rW: 1.3–1.6) occur in bed PO 131 and are better preserved internally. In specimen FMNH-P30340 from bed PO 131 at the Profilstranda section, the septal necks are orthochoanitic and the connecting rings are thickened and concave (figs 6C, 50B). The septal perforation is 1.7 mm in diameter and the connecting ring at approximately midlength between two chambers is 1.4 mm in diameter (0.11–0.14 of corresponding conch height). Approximately six chambers occur at a distance similar to the corresponding conch height.

The type specimen of this species comes from a coastal outcrop between Lundehuken and Papegoyneset, adjacent to Hinlopenstretet, from a level near the top of V 2 in the terminology of Fortey (1980) (see Evans & King 1990). This is only a few kilometers south of the Profilstranda section, and at a level almost identical to beds PO 131, where the majority of our specimens of V. floweri were collected (see Fig. 1). Evans & King (1990) described and discussed Valhalloceras floweri in detail based on a single specimen, which expands laterally with an angle of 12° and dorsally with an angle of 19°, and which has a relative conch width (rW) of 1.4. Both values are closely similar to the specimens described herein. The specimens are also almost identical in conch cross section shape, conch curvature, in relative septal spacing and in the shape of the septal necks. However, the only available median section from specimens from our collection shows a siphuncle with contracted segments. This difference can be an effect of different preservation. In the type specimen, the septa and partly the connecting rings are strongly recrystallized and partly only traces of the former outlines are preserved (Evans & King 1990: pl. 1 figs 8, 10–11). Alternatively, the difference can be true and reflect different growth stages and ontogenetic change, because the figured siphuncle in the type is from a corresponding conch height of ca 7 mm, compared with the specimen figured herein (Fig. 50B) with a corresponding conch height of ca 14 mm. Depending on the interpretation of the differences, the genus Valhalloceras has tubular to concave or exclusively concave segments, respectively. In the former interpretation the genus would be transitional between Oncocerida and Ellesmerocerida and in the latter it would be a bassleroceratid, similar to Lawrenceoceras, but with orthochoanitic, instead of loxochoanitic septal necks. More material is needed to definitively solve this problem. Here we place the genus provisionally within the Phthanoncoceratidae, because the presence of tubular connecting rings during early growth stages is assumed to be real.