Lituites kruegeri, Aubrechtová & Korn, 2022

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 : 84-86

Lituites kruegeri sp. nov.

urn:lsid:zoobank.org:act:52BE9C66-AE91-46CA-893A-B1749CC2980E

Figs 63B , 64A–E , 65 , Tables 9–11

Lituites sp. – Neben & Krueger 1971: pl. 31 fig. 5.

Diagnosis

Species of the genus Lituites with coiled part 33 mm in diameter; inner whorls contiguous, last whorl detached, coiling widely open. Whorl expansion rate based on conch shape 2.70, whorl expansion rate based on whorl height 2.00. Uncoiled part almost straight, tubular (expansion angle 1°). Shell surface with growth lines, sharp lirae and flat annuli. Ornament elements rectiradiate in the coiled part and prorsiradiate in the backcoiled part, closer together in the last quarter of the last whorl and further apart in distance upon uncoiling; ventral sinus deep and rounded, with a ventral band, lateral sinus very shallow or ornament elements straight across flanks.

Etymology

After Hans-Hartmut Krueger, a skilled preparator of the Museum für Naturkunde, Berlin, who masterfully prepared the holotype.

Type material

Holotype GERMANY • Brandenburg, Werbellinsee; Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Neben and Krueger Coll.; previously illustrated by Neben & Krueger (1971: pl. 31 fig. 5), re-illustrated here in Fig. 63B ; MB.C.30539 .

Description

Holotype MB.C.30539 ( Fig. 63B ) consists of the coiled part (dm = 33 mm; innermost whorls are nearly in contact with the preceding, while the last whorl is detached and forms a gap 4.5 mm wide; coiling rates are WER dm = 2.70 and WER ah = 2.00; Fig. 64A–E ) and a short part of the backcoiled part (length = 32 mm; wh = 11 mm; EA ~ 1°). The ornament undergoes some ontogenetic change: shell is not preserved up to 16 mm diameter, but it appears that there are shallow annuli that are visible on the internal mould. Between 16 and 26 mm in diameter, the ornament consists of shallow annuli with distances of 0.5 mm, which are particularly well-developed on the inner and outer flank. They are accompanied by sharp growth lines, which are coarsest in the area of the ventrolateral projection. The annuli weaken at 26 mm diameter and are replaced by raised lirae produced by rhythmically strengthened growth lines. This type of ornament continues along the last part of the coiled part of the conch (33 mm diameter). The backcoiled part and the beginning of the straight part have then sharp growth lines, which are occasionally strengthened to form lirae. This part of the conch bears incipient annuli, which are most conspicuous in the ventrolateral area as semilunate, rounded elevations. The course of the growth lines is rather stable on the coiled and the uncoiled conch, but their direction changes from rectiradiate to prorsiradiate. Generally, the growth lines extend nearly straight across the flank and form a moderately high ventrolateral projection. The shape of the ventral sinus changes: It is very deep and U-shaped in the coiled part and the beginning of the backcoiled part, where the growth lines touch the preceding and form a ventral band ( Fig. 65 ). Along the backcoiled and the straight part, there occurs a shallowing of the ventral sinus. The chamber length ratio is ca 0.38, with lower values in the coiled part apically and higher values in the backcoiled part of the specimen.

Remarks

Lituites kruegeri sp. nov. differs from L. perfectus in the more regular coiling of the conch and a more delicate shell ornament. Lituites dewitzi sp. nov. is similar in the type of coiling but has a coarser ornament and a greater expansion angle of the uncoiled part. Lituites evolutus (Late Ordovician strata of Hunan) is loosely coiled with a straight uncoiled part of the conch but some specimens have a curved uncoiled part ( Fang et al. 2017: pl. 7 figs 2, 7); the whorl expansion rates are greater and the shell ornament is finer compared to L. kruegeri sp. nov.

Specimen MB.C.30540 ( Figs 63A , 64F–J ) might also belong to L. kruegeri sp. nov. because it has a similar geometry of the coiled part. However, the shell ornament has less prominent annuli, the ornament elements are less prorsiradiate and the interspace width is smaller. For these reasons, MB.C.30540 is classified as Lituites cf. kruegeri sp. nov.

Figures

Fig. 63. Lituites kruegeri sp. nov. and L. cf. kruegeri from the Upper Grey Orthoceratite Limestone. A. L. cf. kruegeri – specimen MB.C.30540 (Neben & Krueger Coll.) from Hohensaaten (Brandenburg); lateral view. B. L. kruegeri sp. nov. – holotype MB.C.30539 (Neben & Krueger Coll.) from Werbellinsee (Brandenburg); previously figured by Neben & Krueger (1971: pl. 31 fig. 5); ventral and lateral views. Scale bar units = 1 mm.

Fig. 64. Lituites kruegeri sp. nov. and Lituites cf. kruegeri. A. L. kruegeri sp. nov., outline of coiled conch part of holotype MB.C.30539. B–E. L. kruegeri sp. nov., conch proportions and coiling rates of holotype MB.C.30539. F. L. cf. kruegeri, outline of coiled conch part of specimen MB.C.30540. G–J. L. cf. kruegeri, conch proportions and coiling rates of specimen MB.C.30540. Scale bar units = 1 mm.

Fig. 65. Lituites kruegeri sp. nov. from the Upper Grey Orthoceratite Limestone; lirae on the venter in holotype MB.C.30539 (Neben & Krueger Coll.) from Hohensaaten (Brandenburg, Germany), at wh = 11 mm. Scale bar units = 1 mm.