瑜伽論記 1.355

1.355

婆沙復云：施設論說：劫初時人，有忽腹行，身形既變，共號為蛇；復有欻然，生第三牛，身形既變，共號為象。

The *Vibhāṣā* further says: The *Prajñapti-śāstra* states: 'Among humans at the beginning of the kalpa, some suddenly moved on their bellies; once their physical form changed, they were collectively called snakes. Again, there were those who suddenly gave birth to a third cattle [type]; once their physical form changed, they were collectively called elephants.'