This is the order of the hornworts containing the family Anthocerotaceae. According to some classification systems, this is the only order and family of the hornworts. Others divide the hornworts further, either with additional orders (such as Foliocerotales, Leiosporocerotales, Dendrocerotales and Nothothylales), or by dividing the order Anthocerotales into two families Anthocerotaceae and Notothyladaceae). For this site, the most recent classification by Hasegawa (1994) will be used, with the Anthocerotales being sub-divided into the Notothyladaceae and the Antherocotaceae.