Lituites lasaulxii Remelé, 1890

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 : 66-68

Lituites lasaulxii Remelé, 1890

Fig. 45 , Tables 9–11

Lituites Lasaulxii Remelé, 1890 : pl. 3 fig. 1.

? Lituites cf. Lasaulxii – Remelé 1890: pl. 6 fig. 2.

Lituites perfectus ? – Remelé 1890: pl. 6 fig. 4.

Diagnosis

Species of the genus Lituites with diameter of the coiled conch of 25–27 mm; coiling tight or almost tight; backcoiled part strongly curved; juvenile expansion angle of ca 5.5°. Shell surface with narrow annuli and very fine lirae in the coiled part and more prominent annuli and lirae after uncoiling; ventral sinus deeply rounded, becoming shallow and wide on the backcoiled part.

Type material

Lectotype (designated here) GERMANY • Brandenburg, Heegermühle; Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Kgl. Forstakademie Eberswalde Coll.; illustrated by Remelé (1890: pl. 3 fig. 1), re-illustrated here in Fig. 45A ; MB.C.11678 .

Additional material

GERMANY • 1 spec.; Brandenburg, Eberswalde; Ordovician, Upper Grey Orthoceratite Limestone; Remelé Coll.; MB.C.11645 • 1 spec.; Brandenburg, Heegermühle; Ordovician, Upper Grey Orthoceratite Limestone; Kgl. Forstakademie Eberswalde Coll.; MB.C.11677 .

Description

Lectotype MB.C.11678 ( Fig. 45A ) consists of the coiled part (dm = 28 mm; only the last three quarters of the last volution are preserved, coiling is probably nearly tight or tight) and the backcoiled part (length = 93 mm; wh = 18.4 mm; EA = 5.6°) of the conch. The shell surface is preserved mainly in the coiled part and the beginning of the backcoiled part; there the ornament consists of raised lirae (up to 1.2 mm apart); ventrolaterally they bend steeply backwards to form a deep, U-shaped ventral sinus. The ornament grades into marked annuli (up to 3.4 mm apart) with lirae during ontogeny; the ventral sinus becomes wide. After uncoiling of the conch, there are two conspicuous, raised lines of ornament. The development of the ornament can be subdivided into four successive stages: (1) The last whorl bears lirae, which run almost straight on the inner half of the flank and bend into a narrow projection in the ventrolateral area. The lirae are almost 1 mm apart (on the mid-flank). (2) In the transition from the coiled part to the backcoiled part, the distances between the lirae decrease for a length of 11 mm. The distances between the lirae are somewhat irregular between 0.3 and 0.5 mm. (3) In the following area of the backcoiled part of about 7.5 mm in length, flat annuli appear for the first time; these are superimposed by very fine growth lines. The annuli alternate with some intermediate lirae that form groups of three or four. (4) The remaining extent of the backcoiled and straight part has then only annuli with intervals of 2.5 to 3.5 mm. They are occupied by fine growth lines with 0.1 to 0.15 mm wide intervals. At this stage the growth lines extend with shallow lateral sinus, low ventrolateral projection, and shallow, broadly rounded ventral sinus.

Specimen MB.C.11645 ( Fig. 45B ) is similar to the lectotype in general proportions and shape. The shell ornament has wider and flatter annuli in the uncoiled part of the conch.

Remarks

Specimen MB.C.11677 (Remelé 1890: pl. 6 fig. 2) is a laterally compressed and crushed, straight phragmocone, which is ornamented by narrow, regularly spaced annuli similar to those of the lectotype. However, the specimen differs from the lectotype in having a lower expansion angle (4°). Because the specimen in discussion does not have anything of the coiled part preserved, it is placed in open nomenclature as Lituites cf. lasaulxii .

Lituites lasaulxii is most similar to L. lituus but differs in the stronger curvature of the backcoiled part; also, in L. lasaulxii , annuli are not developed at the coiled part of the conch and in the straight part, annuli are covered by growth lines instead of lirae.

Geographic and stratigraphic occurrence

Northern Germany (in erratics within Pleistocene gravels); late Darriwilian, Middle Ordovician.

Figures

Fig. 45. Lituites lasaulxii Remelé, 1890 from the Upper Grey Orthoceratite Limestone. A. Lectotype MB.C.11678 (Kgl. Forstakademie Eberswalde Coll.) from Heegermühle (Brandenburg); photograph and reproduction of the illustration by Remelé (1890: pl. 3 fig. 1). B. Specimen MB.C.11645 (Remelé Coll.) from Eberswalde (Brandenburg); photograph and reproduction of the illustration by Remelé (1890: pl. 6 fig. 4). Scale bar units = 1 mm.