Hyperlioceras

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''

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 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 convergens, at about 167.7 Ma, which defines base of Zigzagiceras zigzag Zone.

Distribution

Luxembourg, Saudi Arabia, Spain and the United Kingdom.

Synonyms

Source:Braunsella Buckman, 1904Braunsina Buckman, 1902DarelliaDarellina Buckman, 1904Deltoidoceras Buckman, 1902Deltotoceras Buckman, 1904Dissoroceras Buckman, 1902Hugia Buckman, 1904Hyperlioceras Lopadoceras Buckman, 1904ReynesellaReynesia Buckman, 1902

''Toxolioceras''