Acanthoclymenia Hyatt, 1900

Korn, Dieter & Bockwinkel, Jürgen, 2022, The early gephuroceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea), European Journal of Taxonomy 823, pp. 10-47 : 39-40

Genus Acanthoclymenia Hyatt, 1900

Type species

Clymenia ( Cyrtoclymenia) Neapolitana Clarke, 1892 (original designation).

Diagnosis

Genus of the family Acanthoclymeniidae with extremely discoidal, subinvolute to subevolute conch; venter flattened or concave. Suture line with relatively narrow wide lobe, moderately high median saddle, V-shaped E 2 lobe, shallow and rounded lateral lobe. Suture line formula (E 2 E 1 E 2) L: U I.

Included species

Clymenia ( Cyrtoclymenia) Neapolitana Clarke, 1892 , New York; Goniatites forcipifer Sandberger & Sandberger, 1851 , Rhenish Mountains; Goniatites Genundewa Clarke, 1879 , New York; Goniatites Planorbis Sandberger & Sandberger, 1851 , Rhenish Mountains.

Remarks

In the description of the type species as well as its assignment to a genus, it was erroneously assumed that it was a clymeniid; this error was corrected by House (1961) and the species was classified among the gephuroceratids, although in the genus Manticoceras .

Acanthoclymenia is considered the stratigraphically earliest and morphologically simplest genus of the superfamily Beloceratoidea ( Korn & Klug 2002) . It still has a suture line of the early gephuroceratids (for example Ponticeras ), consisting of a divided external lobe and a lateral, umbilical and internal lobe each. The genus is distinguished from the ponticeratids by the concave venter; a character that persists in subsequent forms of the Beloceratoidea .