Jonas
Jonas is the older English form of the name UPDV renders Jonah — the eighth-century prophet whose mission to Nineveh becomes, in Jesus' teaching, a typological sign. The form "Jonas" itself does not appear in UPDV; the prophet's name is uniformly "Jonah." A second figure traditionally collected under "Jonas" — the father of Peter — is rendered "John" in UPDV at John 1:42, so that strand resolves elsewhere.
The Sign of Jonah
When the crowds press in on Jesus and demand a sign, he answers by pointing back to the prophet: "And when the multitudes were gathering together to him, he began to say, This generation is an evil generation: it seeks after a sign; and there will be no sign given to it but the sign of Jonah" (Luke 11:29). The point of the analogy then becomes explicit — the prophet was himself the sign: "For even as Jonah became a sign to the Ninevites, so will also the Son of Man be to this generation" (Luke 11:30). Jonah's preaching, not a separate miracle, was the Ninevites' sign; the Son of Man's appearance among "this generation" works the same way.