Ermoceras is a genus of ammonite belonging to the Thomboceratidae family of the Middle Jurassic (u Baj) found in deposites of central Arabia, Sinai, and Algeria with strong primary and secondary ribs and a single row of lateral tubercles; described as having a deep ventral groove [1]
Telermoceras, with low, depressed whorls, and Kosmermoceras with high, compressed whorls are considered subgenera of Ermoceras [1] Both are from the same time and region. Telermoceras has coarse secondary ribs and a deep umbilicus surrounded by large tubercles or spines. Kosmermocerashas fine sharp to coarse ribbing and a flattish venter
Ermoceras s.l. is derived from Arkelloceras. Westermann (1965)[2] tentatively placed Ermoceras in the Thamboceratidae, based on sutural morphology, removing it from the Stephanoceratidae where it was previously included.