Jurgis Baltrusaitis (1999) demonstrated that there was considerable trade in ideas affecting the iconography of medieval Europe from China, despite the physical distance and the tenuous cultural contacts. He cites for instance the sudden appearance of bat winged demons in european artwork as a direct chinese influence, notably borrowing from the work of Li Long Mien, (previous iconography presented both angels and demons with similar bird wings), and gives other examples through the evolution of Gryllos and a diversity of monstrous forms. With the source material, he makes a quite compelling case.

I guess the slightest degree of contact might in such circumstances allow for a common mythological landscape, notably in shared ornamental forms.