Nomismocanites raritas, Korn & Weyer, 2023

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany), European Journal of Taxonomy 882, pp. 1-230 : 211

Nomismocanites raritas gen. et sp. nov.

urn:lsid:zoobank.org:act:4A1A2F0D-59CF-4F75-97CD-8F2ED1381525

Fig. 128 ; Table 124

Etymology

From the Latin ‘ raritas ’ = ‘rarity’, as only one specimen has been found so far.

Material examined

Holotype

GERMANY • Rhenish Mountains , Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3d1b ; Weyer 1993–1994 Coll.; illustrated in Fig. 128 ; MB.C. 31253 .

Diagnosis

Species of the genus Nomismocanites gen. nov. with a conch reaching 25 mm diameter. Conch at 15 mm dm extremely discoidal and evolute (uw/dm ~0.55) with weakly compressed whorl profile (ww/wh ~0.90) and rounded venter. Ornament with lamellar, rectiradiate, concavo-convex growth lines with deep ventral sinus. With low, rounded crescent-shaped ventrolateral notches in the shell.

Description

Holotype MB.C.31253 has nearly 19 mm conch diameter and is rather well-preserved ( Fig. 128 ). It is extremely discoidal (ww/dm = 0.22) and evolute (uw/dm = 0.49); during the last half volution, the uw/ dm ratio decreases from 0.54 to 0.49. The flanks are subparallel, weakly convergent and flattened but the whorl profile changes on the last half volution; here it shows a weak depression in the outer flank area. The venter is slightly flattened, hence the conch shape reminds on a thick coin. The coiling rate is low (WER = 1.65) and the whorl overlap is rather high (IZR = 0.29) when compared with other prolecanitid ammonoids.

The shell ornament consists of lamellar concavo-convex growth-lines with a semicircular dorsolateral sinus, a moderately prominent ventrolateral projection and a deep ventral sinus. On the last 60 degrees segment, there are weak radial depressions visible on the outer flank in the area of the ventrolateral projection of the growth lines, whose course they follow.

The suture line is not visible in the specimen.

Figures

Fig. 128. Nomismocanites raritas sp. nov., holotype MB.C.31253 (Weyer 1993–1994 Coll.) from the Oberrödinghausen railway cutting, bed 3d1. Scale bar units=1 mm.