Anasirenites Anatibetites Anatomites Anatropites Anatsabites Anavirgatites Anaxenaspis Anclyoceras Ancolioceras Andersonites Anderssonoceras Andesites Andiceras Androgynoceras Anetoceras Aneuretoceras Anfaceras Angranoceras Angulaticeras Anisarcestes Anisoceras Ankinatsytes Anomalocaris Annuloceras Anolcites Anotoceras Anthracoceras Anthracoceratites Anthracoceratoides
Ap Aphanites Apleuroceras Aplococeras Apoderoceras Apsorroceras
Aq Aquilonites
Ar Araneites Araxoceras Arcanoceras Arcestes Archoceras Arcthoplites Arcticoceras Arctocephalites Arctoceras Arctogymnites Arctohungarites Arctomeekoceras Arctomercaticeras Arctoprionites Arctoptychites Arctosirenites Arctotirolites Arestoceras Argentiniceras Argolites Argonauticeras Argosirenites Arianites Aricoceras Arieticeras Arietites Arietoceltites Arisphinctes Aristoceras Aristoceratoides Aristoptychites Arkanites Armatites Arnioceltites Arnioceras Arniotites Arpadites Arthaberites Artinksia Artioceras Artioceratoides
As Asaphoceras Asapholytoceras Asklepioceras Aspenites Asphinctites Aspidoceras Aspidostephanus Aspinoceras Asteroceras thumb|right|250px|Asteroceras Asthenoceras Astiericeras Astieridiscus Astreptoceras Asturoceras
At Ataxioceras Atlantoceras Atsabites