Algerites

Algerites is middle Cretaceous (Cenomanian) anisoceratid ammonoid with a close-coiled adult shell in which the whorls at that stage are in close contact, after starting off with openly coiled whorls, and in which every rib (a character of the family) has a pair of sharp ventral tubercles.

Algerites, which is found in North Africa, named for the country of Algeria, is thought to be derived from Idiohammites, also an anisoceratid. It (Algerites) differs from Allocrioceras in that the later whorls come together in close contact where as in the latter they remain apart.

The Anisoceratidae to which this genus is assigned is included in the diverse heteromorphic superfamily Turrilitaceae

References

• Arkell, et al., 1957. Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part L, Ammonoidea. Geol. Soc. of America and Univ. Kansas Press.

Notable fossil cephalopods (listed by first occurrence)
Cenozoic	The belemnite-cuttlefish-like Belosaepia	Evolutionary history of cephalopods
Mesozoic	Advanced nautiloids Nautilaceae True ammonites Early coleoids Proteroctopus Styletoctopus Keuppia Palaeoctopus Paleocirroteuthis Ceratitid ammonoids late Nautilida Advanced belemnoids Diplobelids: Diplobelus Belemnites: Belemnites Belemnopsis Belemnotheutis
Palaeozoic	First appearance of long-lasting lineages Goniatite and ceratite ammonoids Probable coleoid ancestor Bactritida Earliest belemnoids: Aulacocerids: Aulacoceras Phragmoteuthids: Phragmoteuthis Early forms the earliest cephalopod group Ellesmerocerida Orthocones: Endocerida, Orthocerida, Actinocerida Brevicones: Ascocerida, Oncocerida Earliest coiled cephalopods: Tarphycerida Spirulid?: Shimanskya Octopus Pohlsepia
Cambrian	Earliest unambiguous cephalopods: Plectronocerida Plectronoceras Monoplacophoran-like ancestral forms: Knightoconus Possible, nude, "stem-group cephalopods": Nectocarididae