http://www.newadvent.org/fathers/250102.htmChapter 15. 1. And thus when the divine word had made its home among them, the power of Simon was quenched and immediately destroyed, together with the man himself. And so greatly did the splendor of piety illumine the minds of Peter's hearers that they were not satisfied with hearing once only, and were not content with the unwritten teaching of the divine Gospel, but with all sorts of entreaties they besought Mark, a follower of Peter, and the one whose Gospel is extant, that he would leave them a written monument of the doctrine which had been orally communicated to them. Nor did they cease until they had prevailed with the man, and had thus become the occasion of the written Gospel which bears the name of Mark.
2. And they say that Peter — when he had learned, through a revelation of the Spirit, of that which had been done — was pleased with the zeal of the men, and that the work obtained the sanction of his authority for the purpose of being used in the churches. Clement in the eighth book of his Hypotyposes gives this account, and with him agrees the bishop of Hierapolis named Papias. And Peter makes mention of Mark in his first epistle which they say that he wrote in Rome itself, as is indicated by him, when he calls the city, by a figure, Babylon, as he does in the following words: The church that is at Babylon, elected together with you, salutes you; and so does Marcus my son. 1 Peter 5:13
So Papias is claiming not this chain in the tradition:
Peter --(1)--> Mark --(2)--> elders -(3)---> Papias
Mark ----(1)--> elders--(2)--> Papias
...with Peter knowing about (1) ''by revelation''.
...since Peter ''learned'' what Mark had done not directly by Mark himself, but ''by revelation of the Spirit''!
Why did Papias claim so? Because, according to the Catholic tradition, already ''Matthew'' had to be the First Gospel in absolute terms, so Papias couldn't invent a direct link between Mark and Peter (in order to make Mark an authoritative gospel by inventing a direct connection with Peter) because otherwise he would have obscured the Matthew's priority, putting himself against an already established tradition of the Matthean priority. Therefore the solution was given by the guy named Mark in 1 Peter 5:13-14 :
Since there Peter doesn't say that this Mark was his secretary nor assistant (pace Ben's evident harmonizations), then Papias invented the story that Peter came to know about the Gospel of Mark not directly by Mark but ''by revelation''. In this case Matthew's priority is saved, and Mark can come after Matthew.
So the link between Mark and Peter has any air of being an invention of Papias. Hence the his ''elders'', pace Ben, never existed.