Schuchertoceras fryi, Kröger, 2013

Kröger, Björn, 2013, The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden, European Journal of Taxonomy 41, pp. 1-110 : 84-86

Schuchertoceras fryi sp. nov.

urn:lsid:zoobank.org:act:BA02C2EE-982A-483B-90DF-46E5E5F80FD4

Figs 10F , 39F

Schuchertoceras troedssoni – Frye 1982: 1280, pl. 1, fig. 3 (non pl. 1, figs 1, 2, 5).

Diagnosis

Schuchertoceras with gibbous mature conch with slightly depressed cross section, a basal septum and one ascocerid septum, a highly convex septum of truncation and a mature body chamber height of ca. 40 mm.

Etymology

Refers to Mark W. Frye, who first described some of the ascocerids of the Boda Limestone ( Frye 1982).

Holotype

PMU 24744 .

Type locality and horizon

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

Description

The specimen is a complete fragment of a mature conch. The outer shell is partially preserved and nearly smooth with fine, irregularly spaced growth lines. The total conch length is 65 mm and the maximum height of 40 mm and width of 44 mm (ratio width/height 1.1) are reached at approximately mid-length of the mature body chamber ( Fig. 39F ). The length/height ratio of the mature conch is 0.61. The aperture is depressed, elliptical in cross section, with a height of 32 mm and a width of ca. 36 mm. The septum of truncation is highly convex and dome-shaped, with a height of ca. 14 mm and oblique. The septal perforation is close to the conch margin (ca. 5 mm). The ascocerid septum forms a short and pointed lobe and a wide and shallow sinus and almost reaches the aperture on the antisiphuncular side of the conch. The prosiphuncular side is slightly flattened in cross section ( Fig. 10F ).

Remarks

This specimen was assigned to Schuchertoceras troedssoni Frye, 1982 by Frye (1982: 1280) and described as an “unusually gibbous, and nearly egg-like” specimen. A reinvestigation of the specimens described by Frye (1982) reveals that PMU d727 is not only significantly larger than the other specimens assigned to S. troedssoni , which have a mature length of 40–50 mm only, but differs in having a highly convex septum of truncation. This is in strong contrast to the type of S. troedssoni , which possesses a relatively shallow and flat septum of truncation and which is clearly less gibbous in general conch form. These differences are considered to be significant here and justify the erection of a new species for this specimen.

Stratigraphic and geographic range

Boda Limestone, late Katian, Dalarna, Sweden.

Figures

Fig. 10. Camera lucida drawings of cross sections of selected Boda Limestone cephalopods. A. Cyrtorizoceras thorslundi sp. nov., PMU 26657, Osmundsberget, mature body chamber. B. Tyrioceras cf. kjaerulfi Strand, 1934, PMU 26897, Kallholn. C. Nathorstoceras adnatum sp. nov., PMU 26733, holotype, Kallholn. D. Nathorstoceras kallholnense sp. nov., PMU 26729, holotype. E. Redpathoceras depressum sp. nov., PMU 26927, holotype, Kallholn, cross section of base of mature truncated conch. F. Schuchertoceras fryi sp. nov., PMU 24744, holotype, Kalllholn, cross section of mature aperture (dark grey) and body chamber (medium grey). G. Redpathoceras bullatum sp. nov., PMU 26923, holotype, Kallholn, cross section of base of mature truncated conch. Prosiphuncular side directed downward in all figures. Siphuncles shown as white circles. Scale bar = 10 mm for all 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.