Acanthodesma Zittel, 1876 † accepted as Acanthodesmia Müller, 1857 (verified source for family)
Acanthonotozoma Boeck, 1876 (verified source for family)
Acanthonotozomella Schellenberg, 1926 (verified source for family)
Acanthonotozomoides Schellenberg, 1931 (verified source for family)
Acanthonotus Ross in Ross, 1835 accepted as Acanthonotozoma Boeck, 1876 (verified source for family)
Accanthomunna accepted as Acanthomunna Beddard, 1886 (verified source for family)
Acraspedanthus Carlgren, 1924 (verified source for family)
Acremodonta B. A. Marshall, 1983 (verified source for family)
Acremodontina B. A. Marshall, 1995 (verified source for family)
Actinoporus Duchassaing, 1850 (verified source for family)
Adeonella Busk, 1884 (verified source for family)
Afrosenia Huys & Gee, 1996 (verified source for family)
Afrotethina Munari, 1986 (verified source for family)
Agglutinaria Antsulevich, 1987 (verified source for family)
Agularcturus Kensley, 1984 (verified source for family)
Akritogyra Warén, 1992 (verified source for family)
Alector Gistl, 1848 accepted as Cepheus Koch in Panzer, 1835 (verified source for family)
Allas Sandon, 1927 (verified source for family)
Allosteganoderma Campbell, 1983 † accepted as Steganodermatoides Parukhin & Lyadov, 1979 (verified source for family)
Amalte Reichenbach, 1828 † accepted as Amaltheus de Montfort, 1808 † (verified source for family)
Amaltes Bowdich, 1822 † accepted as Amaltheus de Montfort, 1808 † (verified source for family)
Amalthea Oken, 1817 † accepted as Amaltheus de Montfort, 1808 † (verified source for family)
Amaltheus de Montfort, 1808 † (verified source for family)
Amalthus Sowerby, 1839 † accepted as Amaltheus de Montfort, 1808 † (verified source for family)
Amastiga (verified source for family)
Amaterasia Izawa, 2008 (verified source for family)
Amatheus Oken, 1815 † accepted as Amaltheus de Montfort, 1808 † (verified source for family)
Amatiguakius Coleman, 1991 (verified source for family)
Amesopous Stebbing, 1905 (verified source for family)
Amidostomum Railliet & Henry, 1909 (verified source for family)
Amphifenestrella Rhumbler, 1935 (verified source for family)
Amphion Gistl, 1848 accepted as Axius Leach, 1815 (verified source for family)
Anactinia Annandale, 1909 (verified source for family)
Anademaria Rankin, 1979 accepted as Asperspina Rankin, 1979 (verified source for family)
Anapophysia Huys & Gee, 1996 (verified source for family)
Androcyclas Jørgensen in Nordgaard & Joergensen, 1905 (verified source for family)
Anekes Bouchet & Warén, 1979 (verified source for family)
Angulochiton Hoare, 2001 † (verified source for family)
Anisodoris Bergh, 1898 accepted as Diaulula Bergh, 1878 (verified source for family)
Anomala Deshayes, 1854 accepted as Polymesoda Rafinesque, 1820 (verified source for family)
Anomala Möller, 1832 accepted as Polymesoda Rafinesque, 1820 (verified source for family)
Antemnella Rankin, 1979 accepted as Asperspina Rankin, 1979 (verified source for family)
Anthocolyte Monticelli, 1888 accepted as Anthocotyle van Beneden & Hesse, 1863 (verified source for family)
Anthocotile Parona & Perugia, 1890 accepted as Anthocotyle van Beneden & Hesse, 1863 (verified source for family)
Anthocyrtidium Haeckel, 1881 (verified source for family)
Antiblinia (verified source for family)
Apetaenus Eaton, 1875 (verified source for family)
Apharyngtus Westheide, 1971 (verified source for family)
Aplisiopterus Paetel, 1875 accepted as Elysia Risso, 1818 (verified source for family)
Aplysiapterus Bronn, 1863 accepted as Elysia Risso, 1818 (verified source for family)
Aplysioptera Paetel, 1875 accepted as Elysia Risso, 1818 (verified source for family)
Aplysiopterus Delle Chiaje, 1830 accepted as Elysia Risso, 1818 (verified source for family)
Apocremnus A. Milne-Edwards, 1878 accepted as Aepinus Rathbun, 1897 (verified source for family)
Apodonsiella Hicks, 1988 (verified source for family)
Arachnactis Sars, 1846 (verified source for family)
Arachnanthus Carlgren, 1912 (verified source for family)
Archicircus Haeckel, 1887 (verified source for family)
Archisenia Huys & Gee, 1993 (verified source for family)
Arctocyclopina Mohammed & Neuhof, 1985 (verified source for family)
Arctopsis Barnard, 1920 (verified source for family)
Arcturella G.O. Sars, 1897 accepted as Astacilla Cordiner, 1793 (verified source for family)
Arcturina Koehler, 1911 (verified source for family)
Arcturinella Poisson & Maury, 1931 (verified source for family)
Arcturinoides Kensley, 1977 (verified source for family)
Arcturopsis Koehler, 1911 (verified source for family)
Arcturus Latreille, 1829 (verified source for family)
Areschougia Meneghini, 1844 accepted as Elachista Duby, 1830 (verified source for family)
Argoviaster Hess, 1972 † (verified source for family)
Armandia Guiart, 1927 accepted as Grillotia Guiart, 1927 (verified source for family)
Artocapsa Haeckel, 1881 (verified source for family)
Artophormis Haeckel, 1881 † (verified source for family)
Artrostrobus Cleve, 1899 accepted as Artostrobus Haeckel, 1887 (verified source for family)
Ascaris Linnaeus, 1758 (verified source for family)
Asketochiton Hoare & Sabattini, 2000 † (verified source for family)
Asperspina Rankin, 1979 (verified source for family)
Aspidogaster von Baer in Férussac, 1826 (verified source for family)
Astacilla Cordiner, 1793 (verified source for family)
Astropeplus Sollas, 1888 (verified source for family)
Asymmetracantha Mawson, 1960 (verified source for family)
Atkinsiella Vishniac, 1958 (verified source for family)
Aureliana accepted as Aureliania Gosse, 1860 (verified source for family)
Aureliania Gosse, 1860 (verified source for family)
Austrotrochaclis B. A. Marshall, 1995 (verified source for family)
Axilosphaera E.R. Cox & T.R. Deason, 1968 (verified source for family)
Baccacoccum Y. Zhang, 1978 † (verified source for family)
Bathyphellia Carlgren, 1932 (verified source for family)
Bathypsammis Huys & Gee, 1993 (verified source for family)
Bathyspinula Filatova, 1958 (verified source for family)
Batista Dollfus, 1915 accepted as Batissa Gray, 1853 (verified source for family)
Bautisa Paetel, 1875 accepted as Batissa Gray, 1853 (verified source for family)
Beanella Thiele, 1893 (verified source for family)
Belchiton Ashby & Cotton, 1939 † (verified source for family)
Bennetia accepted as Bennettiella Gibson, 1982 (verified source for family)
Boldia van Bellen, 1946 † (verified source for family)
Botryochytrium R. Yokoyama, B. Salleh & D. Honda, 2007 (verified source for family)
Botryococcus Kützing, 1849 (verified source for family)
Bougisia Laval, 1966 (verified source for family)
Bromeloecia Spuler, 1925 (verified source for family)
Bruceiella Warén & Bouchet, 1993 (verified source for family)
Bulbipora MacGillivray, 1895 (verified source for family)