Zenostephanus is true ammonite genus from the lower part of the Upper Jurassic of eastern England and Scotland belonging to the ammonitid family, Perisphinctidae.

[1] Zenostephanus is revised from Xenostephanus, a preoccupied name for a new genus of toxodont notoungulate from Argentina.

[2] The type is Aulacostephanus ranbyensis

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