The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany) Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.korn@mfn.berlin Author Weyer, Dieter A09A1738-C70E-4F22-A069-8B7DB4A1753D Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.weyer@t-online.de text European Journal of Taxonomy 2023 2023-07-19 882 1 230 http://dx.doi.org/10.5852/ejt.2023.882.2177 journal article 58033 10.5852/ejt.2023.882.2177 57d1d191-2bf5-4229-a0f5-9ab472a114a6 2118-9773 8177581 67C909E4-C700-4F8D-B8CE-5FD9B2C5D549 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.