• Aaleniella variata M. A. Conti & J. C. Fischer, 1981 †: Aalenian
• Abathomphalus intermedius (Bolli, 1951) †: Cretaceous, Upper
• Abathomphalus mayaroensis (Bolli, 1951) †: Cretaceous, Upper
• Absurdaster meriani (Ooster, 1865) †: Cretaceous, Lower
• Absurdaster puezensis Kroh, Lukeneder & Gallemí, 2014 †: Barremian
• Abyssomelania campbellae Kaim, R. G. Jenkins, Tanabe & Kiel, 2014 †: Albian
• Abyssomelania cramptoni Kaim, R. G. Jenkins, Tanabe & Kiel, 2014 †: Maastrichtian
• Acanomyphoria tuberosa F.-X. Guo, 1985 †: Triassic, Upper
• Acanthopora icaunensis d'Orbigny, 1850 †: Valanginian
• Acanthopora lamourouxi Haime, 1854 †: Jurassic
• Acesta brycei Marwick, 1953 †: Oxfordian
• Acesta brycei Marwick, 1953 †: Bathonian
• Acesta brycei Marwick, 1953 †: Aalenian
• Acesta marlburiensis (H. Woods, 1917) †: Santonian
• Acesta marlburiensis (H. Woods, 1917) †: Turonian
• Acesta marlburiensis (H. Woods, 1917) †: Cenomanian
• Aciculiscala coffea Dockery, 1993 †: Campanian
• Acirsa culmosa Sohl, 1964 †: Campanian
• Acirsa pacifica (Wilckens, 1922) †: Campanian
• Acirsa pacifica (Wilckens, 1922) †: Santonian
• Acoscinopleura albaruthenica Koromyslova, Martha & Pakhnevich, 2018 †: Campanian
• Acoscinopleura occulta Koromyslova, Martha & Pakhnevich, 2018 †: Maastrichtian
• Acoscinopleura rimosa Voigt, 1956 †: Maastrichtian
• Acoscinopleura rugica Voigt, 1956 †: Maastrichtian
• Acoscinopleura vindocinensis (Filliozat, 1908) †: Santonian
• Acrocidaris arginensis Weber, 1934 †: Hauterivian
• Acrocidaris borissiaki Weber, 1934 †: Jurassic, Upper
• Acrocidaris marocense Vadet, Marignac, Nicolleau & Reboul, 2007 †: Berriasian
• Acrocidaris nicolleaui Vadet & Nicolleau, 2000 †: Callovian
• Acropeltis atlantica Rey, Taj-Eddine & Witam, 1989 †: Valanginian
• Acropeltis atlantica Rey, Taj-Eddine & Witam, 1989 †: Berriasian
• Acrosalenia arabica Kier, 1972a †: Bathonian
• Acrosalenia dhrumaensis Kier, 1972a †: Bathonian
• Acrosalenia mathildae Lambert, 1935 †: Callovian
• Acrosalenia somaliensis Currie, 1925 †: Jurassic, Lower
• Acrosalenia zararensis Lambert, 1937 †: Pliensbachian
• Acrostele incertum H.-Z. Pan, 1982 †: Cretaceous, Upper
• Acteon cretacea Gabb, 1862 †: Cretaceous
• Acteon marullensis A. d'Orbigny, 1850 †: Hauterivian
• Acteonella agricolai Vidal, 1921 †: Maastrichtian
• Acteonella borneensis C. P. Nuttall & Leong, 1972 †: Cretaceous, Upper
• Acteonella crassa (Dujardin, 1835) †: Santonian
• Acteonella decorata Hacobjan, 1976 †: Cenomanian
• Acteonella grossouvrei Cossmann, 1897 †: Turonian
• Acteonella sublaevis Briart & Cornet, 1868 †: Albian
• Acteonina novozealandica Bandel, Gründel & P. A. Maxwell, 2000 †: Callovian
• Acteonina novozealandica Bandel, Gründel & P. A. Maxwell, 2000 †: Bajocian
• Acteonina novozealandica Bandel, Gründel & P. A. Maxwell, 2000 †: Pliensbachian