Cardioceras
Cardioceras (Neumayr and Uhlig, 1881) - the genus from ammonite family Cardioceratidae. Cardioceras descended from genus Quenstedtoceras at the border between Callovian and Oxfordian. They differed from Quenstedtoceras clearly expressed keel, however this keel is observed in the last Quenstedtoceras. Formally Cardioceras genus existed until the middle Oxfordian, but they did not became extinct, they turned into a Amoeboceras genus.
Early representatives of Cardioceras were very diverse, some of them placed on separate genera: Pavloviceras, Goliathiceras, Pachycardioceras, etc. Among Cardioceras described some subgenera, the largest of which can be considered Scarburgiceras with smooth shells and Vertebriceras with strong lateral lobes on the edges.
Dimorphism in the genus Cardioceras was expressed in size, as well as in significant smoothing of living chamber sculpture of macroconch shells. However, their microconch were rather large, with an average phragmocone diameter about 5-7 cm, macroconchs had a diameter of 20-25 cm. Microconchs of Cardioceras genus had no lateral projections on their apertures, however they had long ventral projection (rostrum). All representatives of Cardioceratidae family had more or less long rostrums.
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