Species Gonioptychoceras progastor LANGE

The coils are always wider than high (also between the ribs), a keel formation is not visible in the present specimens. The ribs run curved and slightly retroradiate over the flanks. Lange (1952) introduced the subspecies Gonioptychoceras sebanum progastor because of the large width of the coils. The course of the ribs is very similar to G. sebanum.
After a strong nodule stage, high, curved ribs set in that bend strongly forward near the external side. The ribs reach their greatest height at the point of bending, then weaken and disappear.

* Description according to Lange (1952), supplemented


The species is distinguished from Megastomoceras & Storthoceras by the large width of the coils and the high, strong ribs, which are highest near the external side.
G. sebanum has a smaller Wb and a distinct keel with the same diameter, G. gonioptychum a larger navel width and less high ribs.


Dimensions with D= 27mm (according to Lange)
Nw % v. D: ca. 38%
Wh % v. D: ca. 33%
Wb % v. D: ca. 41%

  • 1952 Gonioptychoceras sebanum progastor subsp. n. – Lange, S. 148, Taf. 17.11

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