Dog-heads

[Ioannes]

Salvete amici! What different animals did different standard bearers (ie signiferes, aquiliferes, etc) wear? Was there a different animal for each rank? I've seen the aquiliferes on Trajan's Column with no covering, and I've heard that praetorian and vigils units in Rome itself wore lions, but what about bears and wolves on field arms?

Gratias vobis ago!