Cyclolituites Lynceus Holm, 1891: 33 Cyclolituites lynceus Sweet 1958: 21 Cyclolituites lycnus Flower 1975: 161 Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician) Aubrechtová, Martina Korn, Dieter European Journal of Taxonomy 2022 2022-03-08 799 1 1 108 Holm, 1891 Holm 1891 [596,992,1389,1416] Cephalopoda Lituitidae Cyclolituites GBIF Animalia Orthocerida 97 98 Mollusca species lynceus   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  Cyclolituiteswith 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 mmapart.    Type material Not available for study; Holm (1891)did not specify a typebut 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; Nebenand KruegerColl.; MB.C.30561•  1 spec.; Mecklenburg-Vorpommern, Boltenhagen(Gross Klütz Höved); Ordovician, Upper Grey Orthoceratite Limestone; Nebenand Krueger1962 Coll.; MB.C.30562.    Description Specimen MB.C.30562 ( Fig. 73B) is an almost complete, coiled conch with 32 mmdiameter 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 mmwide. 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 mmin 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 mmwide; 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 mmin 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 specimensunder 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   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.   Table 15.Siphuncular diameter ratio (SDR) and siphuncular distance ratio (SPR) at their corresponding whorl height in specimens of  Cyclolituites Remelé, 1886.     taxon  catalogue nr  wh  SDR  wh  SPR   C. applanatus MB.C.11671 6.0 0.25 6.0 0.08   C. lynceus MB.C.30561 11.2 0.41 11.2 0.09 the lectotypeof  Cyclolituites lynceusdescribed 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. lynceushas 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 lynnensisis smaller (conch diameter around 28 mm) than  C. lynceusand has a coarser ornament.  Cyclolituites kjerulfidiffers from the other species of  Cyclolituitesin 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). 3700114347 [189,1399,412,439] MB Neben & Krueger Germany Oderberg Oderberg Ordovician 98 99 MB.C.30561 1 Brandenburg 3700114399 MB Neben & Krueger Germany Boltenhagen Boltenhagen Ordovician 98 99 MB.C.30562 1 Mecklenburg-Vorpommern