These are called four "beasts" in the King James Version. But the Greek word is not the same term that is used for symbolic beasts in Revelation. The word here is dzo' on, meaning a living thing. Being derived from the word "life" or "living," the emphasis is that these are living creatures. Perhaps the translation that best conveys the meaning of the word in this context would be "living beings." So actually this is not a prophetic symbol. Revelation does not exactly identify these beings, it just mentions their existence.