The Japonic language family includes the Japanese language spoken on the main islands of Japan as well as the Ryukyuan languages spoken in the Ryukyu Islands. The family is widely accepted by linguists, and the term "Japonic languages" was coined by Leon Serafim. The common ancestral language is known as Proto-Japonic. The essential feature of this classification is that the first split in the family resulted in the separation of all dialects of Japanese from all varieties of Ryukyuan. According to Shiro Hattori, this separation occurred during the Yamato period (250–710).