Imperial diptych offerings to the emperor. However, the fact that the Barberini ivory was almost certainly not a diptych, but some kind of imperial icon without a second panel is a serious argument against the existence of the imperial diptych type. The two panels representing the empress Ariadne, in the Bargello in Florence and the Kunsthistorisches Museum in Vienna, also belong to the hypothesied imperial diptych type. They are the only central panels of such a diptych (other than the Barberini ivory) to survive, since all other fragments of such diptychs are from side panels. Imperial diptych In Late Antiquity, an imperial
Imperial pigeon al., and followed here. Four species of imperial pigeon are found in Philippines and Sulawesi. All have a distinct pale band across the centre of the tail, and a rich green or purple dorsum. This grouping shares characteristics and distribution with "Ptilinopus", and forms a link between the genera. The pink-belled ("D. poliocephala") and the white-bellied ("D. forsteni") imperial pigeon are similar and allopatric species. The Mindoro ("D. mindorensis") and the grey-headed ("D. radiata") imperial pigeons differ in size but are otherwise similar. The spotted imperial pigeon ("D. carola") is sympatric to "D. poliocephala", and though smaller, short tailed and