Lituites bottkei Aubrechtová & Korn 2022, sp. nov.

Lituites bottkei sp. nov.

urn:lsid:zoobank.org:act: E0CCF553-04EB-4E2C-9E3F-6653ABF2432A

Figs 54B, 56–57, Tables 9–10

Diagnosis

Species of the genus Lituites with coiled part ca 26 mm in diameter; coiling open, the last whorl approaches preceding whorls just before uncoiling. Uncoiled part moderately curved, expansion angle 6–7°. Shell ornament with growth lines, transverse lirae and annuli; irregularly developed in thickness and spacing. Ornament elements biconvex in the coiled conch. Ventral sinus moderately deep, lateral sinus wide and shallow, dorsolateral sinus shallow, dorsal projection low.

Etymology

After the late Werner Bottke (1943–2020), the collector of the holotype.

Type material

Holotype SWEDEN • Island of Öland, Gärdslösa; Middle Ordovician; Bottke Coll.; MB.C.29651 (illustrated in Fig. 54B).

Paratype POLAND • West Pomerania, Ustronie Morskie (former Henkengahen); Ordovician; Müldner? Coll.; MB.C.30536.

Description

Holotype MB.C.29651 (Fig. 54B) consists of the coiled part (dm = 26 mm; coiling is open with the whorls not in contact; only the last whorl nearly touches the preceding just before uncoiling; Fig. 56) and the moderately curved backcoiled and straight parts (length = 300 mm; wh = 42 mm; EA ~ 6°). The ornament is best preserved in the penultimate whorl. It is here composed of various successive elements including shallow, rounded annuli, irregularly spaced growth lines and raised lirae. In the backcoiled part, very weak annuli are developed with irregular distances (between 0.5 and 1.0 mm apart); they are particularly well-visible in the ventrolateral area. Lirae (0.1–0.3 mm apart) cover the annuli and their interspaces. They are slightly coarser on the ridges of annuli. The ornament elements become progressively more prominent until the beginning of the straight part (wh ~ 17 mm, Fig. 57), where the shell bears traces of healed injuries (Fig. 6A). For another 21 mm of conch length following the position of the damage, the shell ornament is composed of widely spaced annuli (ca 4 mm apart) and lirae (0.6 mm apart). After that, the annuli become weaker, less regularly developed; at the end of the straight part of the conch, the annuli attain a maximum distance of ca 3 mm. The ornament elements extend with moderately deep ventral sinus, wide and shallow lateral sinus, shallow dorsolateral sinus and low dorsal projection. The chamber length can be measured only locally (CLR between 0.36 and 0.42).

Remarks

Lituites bottkei sp. nov. differs from L. lituus in the loosely coiled part of the conch and in the ornament, which is generally finer with biconvex course in the coiled conch. Lituites bottkei sp. nov. differs from L. perfectus in regular coiling (i.e., the whorls are not eccentric) and greater expansion angle (6° vs 1–3°) of the uncoiled part.

Specimen MB.T.4492.52 is a nearly complete body chamber with several chambers of the phragmocone, which corresponds to the dimensions and expansion angle of L. bottkei sp. nov. However, the ornament is coarser (annuli up to 4 mm apart) and the specimen is therefore classified as Lituites cf. bottkei.

Geographic and stratigraphic occurrence

Sweden (in situ) and Poland (in erratics within Pleistocene gravels); Middle Ordovician.