Kingdom Animalia Family Graphoceratidae Rank Genus Subclass Ammonites | Superfamily Hildocerataceae Phylum Mollusca Order Ammonitida | |
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Similar Ammonites, Ludwigia murchisonae, Stephanoceras, Ludwigia, Dorsetensia | ||
Hyperlioceras is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is Hyperlioceras discites (Waagen, 18567)
Contents
Morphology
The shell of Hyperlioceras is very compressed and involute, with a tall persistent keel and a deep umbilicus.
Biostratigraphic significance
The International Commission on Stratigraphy (ICS) has defined the base of the Bajocian Stage of the Jurassic as the lowest occurrence of the genus Hyperlioceras, at 170.3 ± 1.4 million years ago, which defines base of the Hyperlioceras discites Zone. This point also marks the end of the preceding Aalenian Stage. The upper boundary of the Bajocian is indicated by the lowest occurrence of the ammonite Parkinsonia (G.) convergens, at about 167.7 Ma , which defines base of Zigzagiceras zigzag Zone.