Early schism

There are 550,000 followers of the Oriental Orthodox Church, mostly in Iraq, Lebanon, Syria, Iran, USA, and India. Why am I fascinated by this, other than as more proof that I would need thousands and thousands of lifetimes to learn, read, and experience all the things I would like to.

Encyclopedia: Eastern Rite:
2. Those who accepted the Council of Chalcedon 451 similarly classified those who rejected it as Monophysite heretics. The Churches that refused to accept it considered, of course, that it was they who were orthodox. The six present-day Churches that continue their tradition reject the description 'Monophysite'. They are often called, in English, Oriental Orthodox Churches, to distinguish them from the Eastern Orthodox Churches. This distinction, by which the words 'oriental' and 'eastern' are used as labels for two different realities, is impossible in most other languages and is not universally accepted even in English. These churches are also be referred to as non-Chalcedonian or, more positively, as pre-Chalcedonian.