Early Christians took the prophet Jonah to be a type of Christ because he was in the great fish for three days, like Christ in the tomb -- Jonah 1-2 (cached). Thus he appears often in early Christian art, especially funerary art where the hope of resurrection would be especially important.
In the image above, from the Murano diptych, we see the great fish on the extreme right, ready to swallow Jonah. On the extreme left, the fish has opened its mouth to release the reluctant prophet. Then, as we switch back toward the right we see first Jonah sleeping under the gourd tree (Jonah 4:5-8, cached) and then God's lesson to Jonah about the gourd tree (Jonah 4:9-11, cached). (In scripture God speaks the message himself, but to avoid representing the Deity this artist has substituted an angel, Greek aggelos being the word for "messenger" or "message.")
The payoff episode in Jonah the Prophet's story, his preaching to the Ninevites and their subsequent repentance, is rarely seen in early Jonah narratives, while the gourd-tree episode is almost always included. Artists of the time found it convenient to adapt the episode's imagery from conventional representations of Endymion, such as this one:
Other images:
Two catacomb paintings in
the Cubiculum of Jonah, Rome
A catacombs
painting of Jonah tossed overboard
4th century sculpture
possibly from TarsusMenu