Lituites cf. lituus de Montfort, 1808

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 56-58

Lituites cf. lituus de Montfort, 1808

Figs 33C , 36 , Tables 9–10

Material examined

POLAND • 2 specs; West Pomerania, Island of Chrząszczewska (former Gristow); Ordovician, Upper Grey Orthoceratite Limestone; Müchner Coll.; MB.C.30529 , MB.C.30530 .

SWEDEN • 1 spec.; Island of Öland , Island of Öland; Ordovician; Technische Universität Berlin Coll.; MB.C.30531 .

COUNTRY UNKNOWN • 1 spec.; Ordovician; MB.C.11650 .

Description

Specimen MB.C.30529 ( Fig. 33C ) consists of the coiled part (2.25 tightly coiled volutions; dm = 27 mm; WER 2.3; Fig. 36A–E ) and the weakly curved backcoiled part (length = 102 mm; wh = 18 mm; EA ~5°). The initial chamber of the phragmocone is cup-shaped and small (whorl height ca 1.4 mm). The initial ca 4 mm of conch length is ornamented by fine growth lines (0.1–0.2 mm apart); after that pairs of raised lirae appear (up to 0.7 mm apart) with extremely fine growth lines in between them. From about the beginning of the second whorl, a weak lateral sinus is developed. The ornament of the rest of the coiled and backcoiled part of the conch consists of biconvex lirae and flat ribs. The ribs are barely discernible in the second half of the specimen and only coarse lirae are visible (1.3 mm apart). Lateral sinus is either very shallow or the ornament elements are straight, ventral sinus is deep and rounded, dorsal projection and dorsolateral sinuses are not developed. At the end of the specimen, only lirae (1 mm apart) are present.

Remarks

The specimens resemble Lituites lituus in their overall dimensions, but the backcoiled part in specimens MB.C.30529, MB.C.30530 ( Fig. 36F–J ) and MB.C.30531 is only weakly curved and the shell ornament is slightly finer. Specimen MB.C.30529 differs with its biconvex lirae and flat ribs on the shell surface. Specimen MB.C.11650 is a fragmentary and slightly deformed body chamber, which has a finer shell ornament; the ornament elements form a flatter lateral sinus compared to L. lituus .

Figures

Fig. 33. Lituites lituus de Montfort, 1808 (A–B) and Lituites cf. lituus de Montfort, 1808 (C) from the Upper Grey Orthoceratite Limestone.A. Neotype MB.C.30527 (Neben & Krueger Coll.) from Oderberg, Bralitz (Brandenburg); previously figured by Neben & Krueger (1971: pl. 31 fig. 1); magnification of the coiled part on the right. B. Specimen MB.C.2497 (Helms 1966 Coll.) from Gross Zicker (Island of Rügen, Mecklenburg-Vorpommern); magnification of the coiled part on the right. C. Specimen MB.C.30529 (Münchner Coll.) from the Island of Chrząszczewska (former Gristow), West Pomerania, Poland. Scale bar units = 1 mm.

Fig. 36. Lituites cf. lituus de Montfort, 1808. A. Outline of coiled conch part of specimen MB.C.30529. B–E. Conch proportions and coiling rates of specimen MB.C.30529. F. Outline of coiled conch part of specimen MB.C.30530. G–J. Conch proportions and coiling rates of specimen MB.C.30530. Scale bar units = 1 mm.