Lituites nebeni, 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 : 82-83

Lituites nebeni sp. nov.

urn:lsid:zoobank.org:act:7DBAADFC-3AC7-41C1-B0BF-894C3FE9D6FE

Figs 58C , 61–62 , Tables 9–10

Lituites cf. lituus – Hardt 1953: 45, text-fig. 10.

Lituites sp. – Neben & Krueger 1971: pl. 31 fig. 2.

Diagnosis

Species of the genus Lituites with coiled part diameter of 24 mm; conch tightly coiled; whorl expansion rate ca 2.00. Uncoiled part weakly curved, very slender and almost tubular upon uncoiling, later reaching an expansion angle of 4°. Shell surface with very flat, widely spaced annuli (up to 4 mm apart) and sharp lirae (up to 1.2 mm apart).

Etymology

After the late W. Neben (1901–1971), a private collector, who collected important specimens studied herein.

Type material

Holotype GERMANY • Brandenburg, Niederfinow; Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Neben Coll.; MB.C.30541 (illustrated in Fig. 58C ).

Description

Holotype MB.C.30541 ( Fig. 58C ) consists of the coiled part (dm = 24 mm; 1.25 whorls, tightly coiled, WER ~ 2.00; Fig. 61 ) and the faintly curved backcoiled part (length = 73 mm; wh = 13 mm); the backcoiled part is almost tubular after uncoiling and later reaches an expansion angle of 4°. The ornament of the coiled part consists of flat, widely spaced annuli (arranged up to 1.5 mm apart) with very fine growth lines in between; the backcoiled part possesses sharp lirae (0.5–1.2 mm apart), which are also visible on the internal mould, and very flat, widely spaced annuli (up to 4 mm apart). In the uncoiled part of the conch, the course of ornament elements is rectiradiate to slightly prorsiradiate; lateral sinus is shallow, dorsal projection is very low. The phragmocone chambers are ca 0.46 of whorl height with an increase up to 0.70 during ontogeny ( Fig. 62 ).

Remarks

Lituites nebeni sp. nov. is somewhat similar to Trilacinoceras filix sp. nov. described below, which differs in the more delicate shell ornament, the less prominent curvature of the conch after uncoiling and a compressed whorl profile in late growth stages. The character of ornament and the circular whorl profile of the backcoiled part of the conch suggests, however, that L. nebeni sp. nov. should be classified in Lituites .

The new species is similar to L. anguinus but the latter has an openly coiled juvenile conch and a lower expansion angle of the uncoiled part. Lituites lituus differs from L. nebeni sp. nov. in the moderate curvature of the uncoiled part, which also has a greater expansion angle (5°–8°); the shell ornament in L. lituus consists of prominent (instead of flat) annuli.

Figures

Fig. 58. Species of Lituites from glacial erratics. A. Lituites clavis sp. nov., holotype MB.C.30537 (Neben Coll.) from the Upper Grey Orthoceratite Limestone of Niederfinow (Brandenburg, Germany); previously figured by Neben & Krueger (1971: pl. 31 fig. 3). B. Lituites dewitzi sp. nov., holotype MB.C.30538 (Neben Coll.) from the Schroeteri Limestone of Boltenhagen near Gross Klütz Höved (Mecklenburg-Vorpommern, Germany). C. Lituites nebeni sp. nov., holotype MB.C.30541 (Neben Coll.) from Upper Grey Orthoceratite Limestone of Niederfinow (Brandenburg, Germany); previously figured by Neben & Krueger (1971: pl. 31 fig. 2). Scale bar units = 1 mm.

Fig. 61. Lituites nebeni sp. nov. A. Outline of coiled conch part of holotype MB.C.30541 (Neben Coll.). B–E. Conch proportions and coiling rates of holotype MB.C. MB.C.30541. Scale bar units = 1 mm.

Fig. 62. Lituites nebeni sp. nov., chamber length/whorl height of holotype MB.C.30541 (Neben Coll.) from Niederfinow (Brandenburg, Germany). A. Empirical data. B. Three data point averaged.