We describe a Middle Triassic volcano-sedimentary sequence, which outcrops on Rhodes Island at the southeastern edge of the Aegean Arc. The sequence is tectonically overlain by the Mesozoic calcareous platform of the local Archangelos Unit. The latter is regarded as equivalent to the Gavrovo-Tripolis Unit of mainland Greece and Crete. We propose that the volcano-sedimentary sequence described here is homologue to the Tyros Beds of Peloponnesus or the Ravdoucha Beds of Crete, which mark the stratigraphic base of the Gavrovo-Tripolis calcareous platform. Consequently we suggest that Tyros Beds characterize the base of the Gavrovo-Tripolis Unit all along the southern Hellenic Arc, from Peloponnesus through Kythira and Crete to Rhodes Island.