),[1] was an Early Christian Bishop of Smyrna (modern İzmir, Turkey), who allegedly was an eyewitness and disciple of Jesus of Nazareth and a companion of John the Elder.
Aristion is identified in Ado of Vienne (874 CE) as "one of the seventy-two disciples of Christ."
And if by chance anyone who had been in attendance on the elders arrived, I made enquiries about the words of the elders—what Andrew or Peter had said, or Philip or Thomas or James or John or Matthew or any other of the Lord’s disciples, and whatever Aristion and John the Elder, the Lord’s disciples, were saying.
Implying that the authorship of the long ending of Mark would be traditionally attributed to this first century Bishop.
This would explain why Church Fathers like Irenaeus of Lyon already received the longer ending as canonical part of the Gospel.