[Antoninus]

Heretical Christians, followers of the teaching of bishop Arian.

His name was Arius, not Arian. His followers were Arians. At one point, Arianism was the dominant Christian belief in the Roman Empire and among some of the major barbarian nations. Arianism was officially denounced at the Council of Nicaea in AD 325, but that didn't prevent the Arian bishops from wielding considerable political power. The Roman Emperor, Constantius II, was an Arian and actively persecuted orthodox Catholic Christians, including Saint Athanasius.

Arius came to a particularly bad end, however...
The Gruesome Death of Arius, AD 336

[AZJeep]

Sorry for the typo. Arius is right. Thanks for the correction.
Apparently he was not even a bishop, just presbyter.
Christianity since the time of Constantine until the rein of Theodosius was oscillating between orthodoxy (Athanasius) and Arians. Councils of Tyre and Smirnium were Arian wins, Council of Nicaea was decisive victory of Athanasius, although even there almost half of the bishops were Arians. Arians were around for a long while, see the Visigoths above, but eventually they were repudiated,, books burned etc.
Medieval Christianity attributed Arians all kind of evils, but during the early times, they were considered fellow Christians with somewhat different theological views. Just few votes here and there, we could be all Arians now?!