Acanthobatis Larrazet, 1886 † accepted as Anacanthobatis von Bonde & Swart, 1923 (extant flag source)
Acanthoclymeniidae Schindewolf, 1955 † (current name source)
Acanthoclymeniidae Schindewolf, 1955 † (basis of record)
Acanthoclymeniidae Schindewolf, 1955 † (habitat flag source)
Acanthoclymeniidae Schindewolf, 1955 † (extant flag source)
Acar celleporacea (Tate, 1886) † (extant flag source)
Acar domingensis Auct † (extant flag source)
Acar sandersonae Powell, 1933 † (extant flag source)
Acesta maui B.A. Marshall, 2001 † (extant flag source)
Acesta rathbuni (Bartsch, 1913) (extant flag source)
Acharax clarificata Dell, 1995 † (extant flag source)
Achradosporis Srivastava, 1975 † (habitat flag source)
Achradosporis Srivastava, 1975 † (current name source)
Achradosporis Srivastava, 1975 † (basis of record)
Achradosporis Srivastava, 1975 † (extant flag source)
Aclophoropsis B. A. Marshall, 1983 (extant flag source)
Acmophyllum Sytova, 1968 † (name verified source)
Acmophyllum Sytova, 1968 † (basis of record)
Acreuciroa Jaeckel & Thiele, 1931 (extant flag source)
Acroporella A. Praturlon, 1964 † (verified source for family)
Acrosterigma cygnorum (Deshayes, 1855) (extant flag source)
Acrosterigma reeveanum (Dunker, 1852) (extant flag source)
Actinozygus fragilis A.P. Rood & T. Barnard, 1972 † (extant flag source)
Acuodulodon Hu, Meng & Clark, 2007 † accepted as Dsungarodon Pfretzschner & Martin in Pfretzschner, Martin, Maisch, Matzke & Sun, 2005 † (source of synonymy)
Acuturris scotus (J.B. Risatti) F.H. Wind & S.W. Wise † (extant flag source)
Adaverina Klaamann, 1969 † (basis of record)
Adaverina Klaamann, 1969 † (name verified source)
Aegyptosuchidae Kuhn, 1936 † (extant flag source)
Aegyptosuchidae Kuhn, 1936 † (habitat flag source)
Aegyptosuchidae Kuhn, 1936 † (current name source)
Aegyptosuchidae Kuhn, 1936 † (basis of record)
Aeneator attenuatus Powell, 1927 † (extant flag source)
Afrocardium skeeti (Hedley, 1906) (extant flag source)
Agastrioceras Schmidt, 1938 † (basis of record)
Agastrioceras Schmidt, 1938 † (name verified source)
Ahmuellerella dietzmannii P. Reinhardt † (extant flag source)
Aktastioceras Shimanskiy, 1948 † (name verified source)
Aktastioceras Shimanskiy, 1948 † (basis of record)
Alaginella Laseron, 1957 (extant flag source)
Alangium Lamarck, 1783 (extant flag source)
Alaticolpites M.S.P. Regali, N. Uesugui & A.S. Santos, 1975 † (basis of record)
Alaticolpites M.S.P. Regali, N. Uesugui & A.S. Santos, 1975 † (extant flag source)
Alaticolpites M.S.P. Regali, N. Uesugui & A.S. Santos, 1975 † (habitat flag source)
Alaticolpites M.S.P. Regali, N. Uesugui & A.S. Santos, 1975 † (current name source)
Alcithoe sarissa (Tate, 1889) † (extant flag source)
Alcoveria Beltan, 1972 † (verified source for family)
Aliculastrum cylindricum (Helbling, 1779) † (extant flag source)
Alinka Krzeminski, 1992 † (extant flag source)
Alinkidae Krzemiński, 1992 † accepted as Procramptonomyiidae Kovalev, 1985 † (extant flag source)
Alinkidae Krzemiński, 1992 † accepted as Procramptonomyiidae Kovalev, 1985 † (source of synonymy)
Allocoeniopsis Alloiteau, 1958 † (basis of record)
Allocoeniopsis Alloiteau, 1958 † (name verified source)
Allorisma King, 1844 † (extant flag source)
Allorisma curvatum Morris, 1845 † (extant flag source)
Aloconcha † accepted as Alococoncha Pojeta & Gilbert-Tomlinson, 1977 † (source of synonymy)
Altaja Zheltonogova, 1960 † (basis of record)
Altaja Zheltonogova, 1960 † (name verified source)
Altispecula Powell, 1930 accepted as Eumetula Thiele, 1912 (extant flag source)
Ambuscintilla Iredale, 1936 (extant flag source)
Amiantis mathewsoni (Grabb) † (extant flag source)
Amusium balloti (Bernardi, 1861) † (extant flag source)
Amusium corneum (J. Sowerby, 1818) † (extant flag source)
Amynodon Marsh, 1877 † (habitat flag source)
Amynodon Marsh, 1877 † (extant flag source)
Anachis miser (G.B. Sowerby I, 1844) (extant flag source)
Anadara addita Iredale, 1939 (extant flag source)
Anadara craticulata (Nyst, 1848) (extant flag source)
Anadara crebricostata (Reeve, 1844) (extant flag source)
Anadara dautzenbergi (Lamy, 1907) (extant flag source)
Anadara ferruginea (Reeve, 1844) (extant flag source)
Anadara granosa (Linnaeus, 1758) (extant flag source)
Anadara pilula (Reeve, 1843) (extant flag source)
Anadara rotundicostata (Reeve, 1843) (extant flag source)
Anafesta Fedonkin, 1984 † accepted as Anfesta Fedonkin, 1984 † (source of synonymy)
Anaspis Robertson, 1941 † accepted as Saarolepis Robertson, 1945 † (extant flag source)
Anfesta Fedonkin, 1984 † (basis of record)
Angaria delphinus (Linnaeus, 1758) (extant flag source)
Anilioidea incertae sedis † (extant flag source)
Anisodonta subalata Gatliff & Gabriel, 1910 (extant flag source)
Ankylophoridae Gaudant, 1978 † (basis of record)
Ankylophoridae Gaudant, 1978 † (habitat flag source)
Ankylophoridae Gaudant, 1978 † (extant flag source)
Annachlamys flabellata (Lamarck, 1819) (extant flag source)
Annachlamys macassarensis (Chenu, 1845) (extant flag source)
Annachlamys murrayana (Tate, 1886) † (extant flag source)
Anobasicrinidae Strimple, 1961 † (extant flag source)
Anobasicrinidae Strimple, 1961 † (habitat flag source)
Anobasicrinidae Strimple, 1961 † (basis of record)
Anobasicrinidae Strimple, 1961 † (current name source)
Anomia cymbula Tate † (extant flag source)
Anomia trigonopsis Hutton, 1877 (extant flag source)
Anthrasimias Bajpai, Kay, Williams, Das, Kapur & Tiwari, 2008 † accepted as Marcgodinotius Bajpai, Kapur, Thewissen, Das, Tiwari, Sharma & Saravanan, 2005 † (source of synonymy)
Anthropornis Wiman, 1905 † (extant flag source)
Anthropornis nordenskjoeldi † (extant flag source)
Antigona aglaurae † (extant flag source)
Antigona chemnitzii (Hanley, 1845) (extant flag source)
Aphanolemur Granger & Gregory, 1917 † accepted as Smilodectes Wortman, 1903 † (extant flag source)
Aphanolemur Granger & Gregory, 1917 † accepted as Smilodectes Wortman, 1903 † (basis of record)
Aphanolemur Granger & Gregory, 1917 † accepted as Smilodectes Wortman, 1903 † (source of synonymy)
Aphanolemur Granger & Gregory, 1917 † accepted as Smilodectes Wortman, 1903 † (name verified source)

 Taxonomic remark

 for Alinkidae Krzemiński, 1992 †

Treated in The Paleobiology Database as a synonym of Procramptonomyiidae Kovalev, 1985, however listed as a valid ... [details]

 Taxonomic remark

 for Entokrohnia Kassatkina, 2012

Assigned to family Tokiokaispadellidae by describer, however that family is treated as a synonym of Pterosagittidae ... [details]

 Taxonomic remark

 for Holophagus Egerton in Huxley, 1861 †

Treated as a synonym of Undina Germar 1834 in some sources. [details]

 Taxonomic remark

 for Lipanellidae Sánchez, 2005 †

Assigned to subclass Heterodonta no order specified) in WoRMS. [details]

 Taxonomic remark

 for Proscorpiidae Scudder, 1885 †

Originally as subfamily (Proscorpioninae); spelling corrected to Proscorpiidae by Kjellesvig-Waering, 1966. [details]

 Taxonomic remark

 for Rhinebothriidae Euzet, 1953

Originally as subfamily of Phyllobothriidae; elevated to family level by Ruhnke et al., 2015. [details]