The authorship of the sauropod dinosaur genus Astrodon is frequently cited as Johnston, 1859, and its type species Astrodon johnstoni is usually cited as Leidy, 1865. Although Johnston's publication does satisfy the Code's requirements for published work, the lack of description means it does not satisfy the criteria of availability in Article 12 for names published before 1931. Astrodon was a nomen nudum until it was made available by Leidy in his subsequent description of the nominal genus with its single new nominal species. The correct authorship of both the genus Astrodon and its type species Astrodon johnstoni is therefore Leidy, 1865.