Holmiceras havelense, 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 : 45-46

Holmiceras havelense sp. nov.

urn:lsid:zoobank.org:act:C92771A7-17B5-4838-8B38-62884C9AAA5C

Fig. 29, Table 8

Lituites aff. praecurrens – Neben & Krueger 1971: pl. 21 figs 2–3.

taxon catalogue nr dm wh uw ww WERdm WERah UWI WWI H. havelense MB.C. 30526 20.6 7.8 7.8 – 2.85 2.59 0.38 –

Diagnosis

Species of the genus Holmiceras with coiled part 21 mm in diameter; uncoiled part nearly straight; expansion angle 7°. Shell surface with growth lines and fine, irregularly spaced lirae.

Etymology

From the river Havel, which flows through the type region.

Type material

Holotype

GERMANY • Brandenburg, Werder (Potsdam); Ordovician, Upper Red Orthoceratite Limestone ; Neben and Krueger Coll.; previously illustrated by Neben & Krueger (1971: pl. 21 figs 2–3), reillustrated here in Fig. 29A; MB.C.30526.

Description

Holotype MB.C.30526 ( Fig. 29A) consists of the coiled part (dm = 21 mm; coiling probably loose, the end of the last volution nearly in contact with the preceding whorl; WER ah = 2.60; WER dm = 2.90) and a short part of the almost straight uncoiled part (length = 29 mm; wh = 14 mm; EA ~ 7°). The delicate shell ornament consists of growth lines and thin lirae, some of which are more raised than others; any prominent annulation is absent. The lirae are laterally oblique, sloping towards the dorsal side; the ventral sinus is deep and rounded and the dorsal projection is flat ( Fig. 29B). The CLR is between 0.20 and 0.25.

Remarks

Specimen MB.C.30526 fits in the diagnosis of Holmiceras but differs from all species of this genus in the more delicate ornament and a much smaller expansion angle of the uncoiled conch part (7° in the new species but 20° in the others).

Geographic and stratigraphic occurrence

The holotype is from Werder (Brandenburg, Germany) and comes from erratics (Aseri Regional Stage, middle Darriwilian, Middle Ordovician) in Pleistocene gravel.