Acanthopectinidae † (basis of record)
Acanthopectinidae † (extant flag source)
Acastea Yang, 1993 † (basis of record)
Achaenodontidae † (extant flag source)
Achaenodontidae † (basis of record)
Acinetasteridae Kesling, 1982 † (basis of record)
Acinetasteridae Kesling, 1982 † (extant flag source)
Acratiidae Gruendel, 1962 † (extant flag source)
Acratiidae Gruendel, 1962 † (basis of record)
Acropyramididae Haeckel, 1881 (basis of record)
Acrospiriferidae † (basis of record)
Acrospiriferidae † (extant flag source)
Acteocinidae Dall, 1913 † (extant flag source)
Acteocinidae Dall, 1913 † (basis of record)
Actinastreidae Alloiteau, 1952 † (basis of record)
Actinastreidae Alloiteau, 1952 † (extant flag source)
Actinodictyidae † (extant flag source)
Actinodictyidae † (basis of record)
Actinostromellidae † (basis of record)
Actinostromellidae † (extant flag source)
Aegocrioceratidae † (extant flag source)
Aegocrioceratidae † (basis of record)
Aenigmastrophiidae † (basis of record)
Aenigmastrophiidae † (extant flag source)
Agathiphylliidae † (extant flag source)
Agathiphylliidae † (basis of record)
Alabushevothyrididae Smirnova, 1994 † (basis of record)
Alabushevothyrididae Smirnova, 1994 † (extant flag source)
Aldanellidae Linsley & Kier, 1984 † (basis of record)
Alpinophylliidae Roniewicz, 1989 † (basis of record)
Alpinophylliidae Roniewicz, 1989 † (extant flag source)
Alxasauridae Russell & Dong, 1993 † (basis of record)
Ambulocetidae Thewissen et al., 1996 † (basis of record)
Ambulocetidae Thewissen et al., 1996 † (extant flag source)
Ameghinichnidae Casamiquela, 1964 † (extant flag source)
Ameghinichnidae Casamiquela, 1964 † (basis of record)
Ammagnostidae Opik, 1967 † (basis of record)
Ammagnostidae Opik, 1967 † (extant flag source)
Amotapidae † (extant flag source)
Amotapidae † (basis of record)
Amphipellidae † (basis of record)
Amphipellidae † (extant flag source)
Amphipithecidae Godinot, 1994 † (extant flag source)
Amphipithecidae Godinot, 1994 † (basis of record)
Ampullinidae Cossmann, 1918 (extant flag source)
Anachronistidae Duffin & Ward, 1983 † (extant flag source)
Anachronistidae Duffin & Ward, 1983 † (basis of record)
Ancistrorhynchidae Cooper, 1956 † (basis of record)
Ancistrorhynchidae Cooper, 1956 † (extant flag source)
Andemantastraeidae † (extant flag source)
Andemantastraeidae † (basis of record)
Angustothyrididae † (basis of record)
Angustothyrididae † (extant flag source)
Anisopidae accepted as Anisopodidae Knab, 1912 (source of synonymy)
Anisopidae accepted as Anisopodidae Knab, 1912 (basis of record)
Anomalocarididae Raymond, 1935 † (basis of record)
Anomalocarididae Raymond, 1935 † (extant flag source)
Anomalorthidae † (extant flag source)
Anomalorthidae † (basis of record)
Anomopterellidae † (basis of record)
Anomopterellidae † (extant flag source)
Anozygidae † (basis of record)
Antiacodontidae † (basis of record)
Antiacodontidae † (extant flag source)
Antzeilleridae † (extant flag source)
Antzeilleridae † (basis of record)
Aphralysiaceae † (basis of record)
Aplocomidae † (basis of record)
Aplocomidae † (extant flag source)
Araksalosiidae † (extant flag source)
Araksalosiidae † (basis of record)
Archaeomaenidae † (basis of record)
Archaeomaenidae † (extant flag source)
Archaeophialidae Knight & Yochelson, 1958 † (extant flag source)
Archaeophialidae Knight & Yochelson, 1958 † (basis of record)
Archaeorthidae † (basis of record)
Archaeorthidae † (extant flag source)
Archegonasteridae Spencer, 1951 † (extant flag source)
Archegonasteridae Spencer, 1951 † (basis of record)
Archeosmylidae Riek, 1953 † (basis of record)
Archeosmylidae Riek, 1953 † (extant flag source)
Archipelepididae Soehn, Märss, Caldwell & Wilson, 2001 † (extant flag source)
Archipelepididae Soehn, Märss, Caldwell & Wilson, 2001 † (basis of record)
Archocyrtiidae Kozur & Mostler, 1981 † (basis of record)
Archocyrtiidae Kozur & Mostler, 1981 † (extant flag source)
Arctolepidae † accepted as Arctolepididae Heintz, 1937 † (extant flag source)
Arctolepidae † accepted as Arctolepididae Heintz, 1937 † (basis of record)
Arenicolitidae † (basis of record)
Arenicolitidae † (extant flag source)
Areostrophiidae Manankov, 1979 † (extant flag source)
Areostrophiidae Manankov, 1979 † (basis of record)
Arkonasteridae Kesling, 1982 † (basis of record)
Arkonasteridae Kesling, 1982 † (extant flag source)
Aseptorhynchiidae † (extant flag source)
Aseptorhynchiidae † (basis of record)
Asioryctidae Kielan-Jaworowska, 1981 † (basis of record)
Asioryctidae Kielan-Jaworowska, 1981 † (extant flag source)
Aspalacidae Gray, 1825 accepted as Spalacidae Gray, 1821 (extant flag source)
Aspalacidae Gray, 1825 accepted as Spalacidae Gray, 1821 (basis of record)
Astraeomorphidae Frech, 1890 † (basis of record)