Ermoceras
Encyclopedia
Ermoceras is a thomboceratid ammonite from the Middle Jurassic ( u Baj
)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
Telermoceras, with low, depressed whorls, and Kosmermoceras with high,compressed whorls are considered subgenera of Ermoceras 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) tentatively placed Ermoceras in the Thamboceratidae, based on sutural morphology, removing it from the Stephanoceratidae
where it was previously included.
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
)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
Telermoceras, with low, depressed whorls, and Kosmermoceras with high,compressed whorls are considered subgenera of Ermoceras 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
Arkelloceras
Arkelloceras is an early Middle Jurassic Stephanoceratacean genus from arctic Canada, Alaska, and Siberia belonging to the family Otoitidae...
. Westermann (1965) tentatively placed Ermoceras in the Thamboceratidae, based on sutural morphology, removing it from the Stephanoceratidae
Stephanoceratidae
Sephanoceratidae is a family of planulate and coronate ammonites within the Stephanocerataceae. Shells are evolute so that all whorls are exposed and have strong ribbing that bifurcates, that is splits in two, on the flanks. Many have tubercles at the point of bifurcation...
where it was previously included.