The Roman legions had battle standards called aquila which featured carvings of either an eagle, wolf, ox with man's head (wtf?), horse, or boar. Do we know what specific species these are based off of?
Some spin off questions I thought of while writing this:
Why were these creatures in particular used to represent the legions?
Who was tasked with crafting these battle standards?
How would a soldier be selected to carry the standard?
Why did Caesar retire all the animals but the eagle?
Did the tradition of using aquila survive into the Byzantine period?
Marius (rather than Caesar) is said to have replaced each legion's standard with an Eagle (Aquila actually means 'eagle'.) No Aquila have been found archaeologically, due to their rarity and their revered place in a Legion's ceremonial. What we know about them is due to their appearance in sculpture. For this reason we can't say what species of Eagle it is for sure, or who made them.
Source: Goldsworthy, Adrian 'The Complete Roman Army'