Silurian Silures • Siluric · · · Info · Definitions · Characters · · Silurian · · Text Latin · · Script 8 · · Length Definitions · · · (noun) from 425 million to 405 million years ago; first air-breathing animals. Synonyms: Silurian period. · · Noun Definition 1 Characters · · S latin capital letter s U+0053 a latin small letter a U+0061 i latin small letter i U+0069 l latin small letter l U+006C n latin small letter n U+006E r latin small letter r U+0072 u latin small letter u U+0075