Cyclolituites lynceus Holm, 1891

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 : 98-100

Cyclolituites lynceus Holm, 1891

Figs 73–74

Cyclolituites Lynceus Holm, 1891: 33 , pl. 1 figs 8–9.

Cyclolituites lynceus – Sweet 1958: 21. — Neben & Krueger 1971: pl. 32 figs 17–18.

Cyclolituites lycnus – Flower 1975: 161.

Diagnosis

Species of the genus Cyclolituites with conch diameters around 35 mm; tight coiling with only the apertural part of the body chamber detached from preceding volutions; whorl expansion rate ca 3.00; whorl profile compressed (WWI = 0.70). Shell surface with fine growth lines and raised pairs of lirae up to 0.4 mm apart.

Type material

Not available for study; Holm (1891) did not specify a type but illustrated one specimen ( Holm 1891: pl. 1 figs 8–9), which is reproduced here in Fig. 73C ; it comes from Lerkaka (Island of Öland, Sweden),

Folkeslunda Limestone (Upper Grey Orthoceratite Limestone, late Lasnamägi Regional Stage, late Darriwilian, Middle Ordovician).

Material examined

GERMANY • 1 spec.; Brandenburg, Oderberg; Ordovician; Neben and Krueger Coll.; MB.C.30561 • 1 spec.; Mecklenburg-Vorpommern, Boltenhagen (Gross Klütz Höved); Ordovician, Upper Grey Orthoceratite Limestone; Neben and Krueger 1962 Coll.; MB.C.30562 .

Description

Specimen MB.C.30562 ( Fig. 73B ) is an almost complete, coiled conch with 32 mm diameter and consists nearly two tightly coiled whorls (WWI = 0.70; WER = 2.90; Fig. 74B–F ), of which only the second half of the last whorl is detached from the preceding. The umbilical window is 4 mm wide. 135 degrees of the last whorl belongs to the body chamber. An increasingly pronounced ridge is raised on the venter at the apertural end of the specimen. The shell ornament is preserved only in the inner whorls and consists of raised pairs of lirae (up to 0.4 mm in distance) and very fine growth lines. The aperture is partly preserved; it has a deep ventral sinus, elongated ventrolateral lappets and a rather shallow lateral sinus (dorsal edge of the aperture is not preserved). The chamber length varies between CLR = 0.20 and 0.30.

Specimen MB.C.30561 ( Fig. 73A ) is an almost complete, coiled conch (dm = 37 mm, nearly two tightly coiled whorls with only the second half of the last whorl is detached; the umbilical window 5.3 mm wide; WWI = 0.71; WER = 3.10; Fig. 74A, C–F ); 135 degrees of the last whorl belong to the body chamber. The shell ornament is preserved only locally and consists of slightly irregularly spaced, raised lirae (up to 0.2 mm in distance) and very fine growth lines in between; the lirae leave imprints on the internal mould. The aperture is incomplete, only a fragment of one ventrolateral lappet is preserved.

Remarks

The two specimens under study are from the Neben & Krueger collection and one of them, MB.C.30562, was previously figured by Neben & Krueger (1971: pl. 32 figs 17–18). Both specimens closely resemble

the lectotype of Cyclolituites lynceus described by Holm (1891: pl. 1 figs 8–9) and are thus confidently assigned to this species. Only specimen MB.C.30561 is slightly more compressed.

In contrast to Cyclolituites applanatus , the species C. lynceus has a larger diameter of the conch (ca 35 mm), a more compressed whorl profile (WWI = 0.70), a higher whorl expansion rate (WER ca 3.00) and a finer ornament. Cyclolituites lynnensis is smaller (conch diameter around 28 mm) than C. lynceus and has a coarser ornament. Cyclolituites kjerulfi differs from the other species of Cyclolituites in the smaller in diameter (20 mm); it uncoils much earlier (almost the whole last whorl is detached), has a narrower umbilical window and a much higher coiling rate (WER = 4.00–5.00).

Geographic and stratigraphic occurrence

Sweden (in situ) and northern Germany (in erratics within Pleistocene gravels); late Lasnamägi Regional Stage (late Darriwilian, Middle Ordovician).

Figures

Fig. 73. Cyclolituites lynceus Holm, 1891. A. Specimen MB.C.30561 (Neben & Krueger Coll.) from Oderberg (Brandenburg). B. Specimen MB.C.30562 (Neben & Krueger 1962 Coll.) from Boltenhagen, Gross Klütz (Mecklenburg); previously figured by Neben & Krueger (1971: pl. 32 figs 17–18). C. Reproduction of the illustration by Holm (1891: pl. 1 figs 8–9). Scale bar units = 1 mm.

Fig. 74. Cyclolituites lynceusHolm, 1891.A. Coiling outline of specimen MB.C.30561.B. Coiling outline of specimen MB.C.30562. C–F. Conch proportions and coiling rates of the specimens MB.C.30561 and MB.C.30562. Scale bar units = 1 mm.