Stereoplasmoceratidae Kobayashi, 1934

Fang, Xiang, Kröger, Björn, Liang, Kun, Chen, Qing, Song, Jiaqi, Jiang, Lan, He, Yaoyan, Wang, Chenggang, Zeng, Xiongwei, Liu, Hao, Wei, Kai, Wu, Fafu & Qie, Wenkun, 2025, Late Ordovician cephalopods from Morocco and their implications, Swiss Journal of Palaeontology (37) 144 (1), pp. 1-11 : 5

Family Stereoplasmoceratidae Kobayashi, 1934 Genus Tafadnatoceras Ebbestad et al., 2022

Type species: Tafadnatoceras tiouririnense Ebbestad et al., 2022 from the Katian Stage , Upper Ordovician

Series, Upper Tiouririne Formation at Tafilalt, eastern Anti-Atlas, Morocco.

Included species: Tafadnatoceras tiouririnense Ebbestad et al., 2022 ; Tafadnatoceras elfechtense sp. nov. (this work).

Diagnosis: Slightly curved orthocones with central siphuncle; siphuncle expanded within chambers with adnate area at septa and small septal perforation; septal necks cyrtochoanitic; connecting rings adnate during late growth stages; with siphuncular lining composed of stacked layers of parietal deposits; with cameral deposits (modified after Ebbestad et al., 2022).

Remarks: Ebbestad et al. (2022) proposed that the genus Tafadnatoceras is similar to Adnatoceras Flower, 1939 and Paradnatoceras Chen & Liu, 1974 but differs in having a continuous lining inside the siphuncle. Moreover, the species of Tafadnatoceras resemble Isorthoceras bisignatum (Barrande, 1877) from Bohemia, Zagros of Iran ( Ghavidel-Syooki et al., 2015) and the Moroccan material presented here, but differ in lacking the Isorthoceras -like reticulate ornamentation (Ebbestad et al., 2022).