Maenioceratidae Bogoslovsky 1958

Family Maenioceratidae Bogoslovsky, 1958

Diagnosis

Family of the superfamily Pharciceratoidea without or with ventrolateral grooves; sutural formula (E 2 E 1 E 2) L U 2 U 1 I; wide to extremely wide external lobe.

Included genera

Maenioceras Schindewolf, 1933; Afromaenioceras Göddertz, 1987; Bensaidites Korn in Korn & Klug, 2002; Trimaenioceras gen. nov.

Remarks

The four genera of the family are very easily distinguished on the basis of the suture line, particularly the shape of the external lobe. This shows a small, rounded E 2 lobe in Maenioceras and Afromaenioceras, but deep and pointed in Trimaenioceras gen. nov. Maenioceras and Afromaenioceras differ in the shape of the E 2 lobe, which in the latter genus has a rectangular form.

The stratigraphic distribution of the four genera is only in part well-known. Bensaidites is probably the stratigraphically oldest representative of the family with “ B. koeneni ” defining the earliest Givetian (Aboussalam & Becker 2011; Becker et al. 2018) in the Moroccan sections. Becker et al. (2004: pl. 1 fig. 22) illustrated a specimen from the basal part of the Oued Mzerreb section (bed -1a), which they named “ Bensaidites n. sp. ”. However, due to its suture line with a shallow, rounded E 2 lobe, this specimen belongs to Maenioceras.

It is clear that Maenioceras precedes Afromaenioceras (Fig. 2), but the position of the material assigned here to the new genus Trimaenioceras gen. nov. has been conclusively determined. In Oued Mzerreb, Trimaenioceras klugi gen. et sp. nov. co-occurs with several Afromaenioceras species in the high part of the section (“ Afromaenioceras Beds ”).