Aipoceratidae Hyatt, 1884

Family Aipoceratidae Hyatt, 1884

Fig. 38 View Fig

Diagnosis

Family of the superfamily Aipoceratoidea with a gyroconic conch. Whorl profile usually laterally compressed.

Included genera

Asymptoceras Ryckholt, 1852 (Tournaisian to Serpukhovian; 6 species).

Aipoceras Hyatt, 1884 (Tournaisian to Viséan; 7 species).

Oncodoceras Hyatt, 1893 (Tournaisian; 3 species).

Librovitschiceras Shimansky, 1957 (Moscovian; 1 species).

Barskoceras Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species).

Remarks

Of the genera of the family Aipoceratidae , only the two genera Aipoceras and Asymptoceras can be considered well known (e.g., Foord 1900; Miller & Furnish 1939). They show a continuous evolution in the degree of coiling, ending in the genera Acanthonautilus Foord, 1896 and Solenochilus Meek & Worthen, 1870 . At the same time there is a continuous evolution towards a more depressed whorl profile.

Librovitschiceras appears as a foreign item in the list of genera; this is due to the very different conch morphology with a wide umbilicus and low coiling rate ( Fig. 38 View Fig ). The genus has been placed in the family Aipoceratidae because of the marginal ventral position of the siphuncle ( Shimansky 1957, 1962, 1967, 1979; Kummel 1964), while Dzik (1984: 173) placed the genus in the Tainoceratidae with question mark. Kummel (1964) did not accept the validity of Librovitschiceras and synonymised the genus with Knightoceras , while Furnish & Glenister (in Kummel 1964, in the same Treatise volume) listed it among the superfamily Aipocerataceae . This controversy cannot be resolved at present.