Probillingsites scandinavicum, Kröger, 2013

Kröger, Björn, 2013, The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden, European Journal of Taxonomy 41, pp. 1-110 : 87-88

Probillingsites scandinavicum sp. nov.

urn:lsid:zoobank.org:act:42510E86-B2FE-40F7-8ED5-319BD939BDD4

Fig. 39 D-E

Diagnosis

Probillingsites with a smooth mature conch with depressed conch cross section; conch margins in longitudinal view convex on prosiphuncular side and concave on antisiphuncular side; maximum conch height of ca. 55 mm at mid-length of body chamber; septa of mature conch slightly oblique; sutures nearly straight.

Etymology

Refers to the larger type area; this is only the second species of Probillingsites known from the region.

Holotype

PMU 26922 .

Type locality and horizon

Kallholn, Dalarna, Sweden, Boda Limestone, Boda Core Member, late Katian, Ordovician.

Description

The specimen is a nearly complete fragment of a mature conch, with a length of ca. 105 mm. The height of the septum of truncation is 39 mm and the apertural height is ca. 40 mm. The maximum height of 55 mm of the conch is approximately at mid-length of the body chamber, where the width is 59 mm (width/height ratio 1.07) ( Fig. 39D, F ). In cross-section the prosiphuncular side is more rounded, the prosiphuncular side slightly flattened. The aperture is constricted and depressed with an elliptical cross-section. The conch surface is poorly preserved but appears to be ornamented with fine, irregularly spaced growth lines.

The phragmocone is ca. 35 mm long and consists of four chambers. The septa are simple convex and slightly oblique, projecting toward the aperture on the antisiphuncular side. The septum of truncation is relatively shallow with a depth of ca. 6 mm.

Comparison

This species is unique amongst the known species of Probillingsites in having only simple straight septa in the mature conch, a relatively long body chamber and a shallow convex septum of truncation.

Stratigraphic and geographic range

Boda Limestone, late Katian, Dalarna, Sweden.

Figures

Fig. 39. Ascocerida and Uranoceratidae of the Boda Limestone. A-B. Redpathoceras bullatum sp. nov. A. PMU 26923, holotype, Kallholn; mature truncated body chamber, lateral view. B. Same specimen, view from antispihuncular side. C. Warburgoceras longitudinale (Angelin in Angelin & Lindström, 1880) comb. nov., NRM-PZ Mo 154065, Unskarsheden; mature body chamber and part of phragmocone in lateral view. D-E. Probillingsites scandinavicum sp. nov., PMU 26922, holotype, Kallholn. D. Mature truncated body chamber, lateral view. E. Same specimen, view from prosiphuncular side. F. Schuchertoceras fryi sp. nov., PMU 24744, holotype, Kalllholn, lateral view. Scale bars: A-E =10 mm; F = 10 mm.