Let’s not forget Ignatius of Antioch who dies in about 110 AD.
The disciple of the Apostle John, bishop and martyr is not one to be forgotten. He is instructive on the larger topic of Petrine Primacy, but for the moment I was keeping on the narrower topic of Matt. 16:18. Nothing in the extant letters of his speaks directly to that verse.
But his time may come. :)