Calycoceras is an extinct genus of cephalopods belonging to the subclass Ammonoidea and family Acanthoceratidae that lived during the Cenomanian stage of the Late Cretaceous, 100-94 Mya. Their shells had ornate ribs. Species C. algeriense Kennedy & Gale, 2017 C. annulatum Collignon, 1964 C. asiaticum (Jimbo, 1894) C. a. asiaticum (Jimbo, 1894) C. a. spinosum (Kossmat, 1897) C. besairieri Collignon, 1937 C. boreale Kennedy, Cobban & Landman, 1996 C. dromense (Thomel, 1972) C. cenomanense (d’Archiac, 1846) C. navicularis Mantell, 1822 C. orientale Matsumoto, Saito & Fukada C. paucinodatum (Crick) C. tarrantense Distribution Calycoceras species may be found in the Cretaceous of Angola, Antarctica, Canada (British Columbia), France, Germany, Japan, Nigeria, Oman, Russia, the United Kingdom, United States (Alaska, Arizona, Kansas, New Mexico, South Dakota, Utah) C. asiaticum may be found in the Cenomanian of Canada, Southern England, northern and southern France, Spain, Romania, Bulgaria, Tunisia, Madagascar, south India and Japan. C. cenomanense may be found in the Cenomanian of United Kingdom, France and Madagascar. Description Shells of Calycoceras asiaticum may reach a diameter of about . The larger phragmocones may reach in diameter. Coiling is moderately involute. All ribs show strong subspinose tubercles. C. asiaticum asiaticum and C. asiaticum spinosum are very similar, the latter has much more robust tuberculation. References Acanthoceratidae Ammonitida genera Cretaceous ammonites Late Cretaceous ammonites of North America Late Cretaceous cephalopods of North America Late Cretaceous animals of Africa Cenomanian life