My limited understanding of spirit animals is that there has been a lot of crossing in lore, between certain aspects of Native American totem animals (and different Native tribes held sometimes vastly different beliefs about the topic) and spirit guides.
It is generally accepted these days by many people who believe in spirit animals that a person may have more than one, and sometimes the fashion in which they are attached may change. That is, someone may have several spirit animals, or might have a main spirit animal and secondaries and tertiaries, or may have a main animal totem and a "shadow" totem, and the beliefs are quite various beyond that.
It is important to lean more on your own beliefs than on what someone else may tell you about it. That is, don't necessarily out-right reject the words and advice of others, but take it with its due amount of scrutiny. They may be advising according to a tradition you do not follow. The same goes for books. I was recommended one book, which seemed interesting to an extent but the author eventually ran down paths which were far from what I would be willing to follow.
As far as meanings, there are some lists out there. But ultimately the representation is up to you, your beliefs, and your own personal experiences. For a very easy example, some people will identify with a bear, saying it is reflective of their inner strength or strong nurturing and protective traits; another may say they identify with the bear because of its undying hunger and touchy temper. Some may say they identify with a wolf because of its loyalty, social pack mentality, and tenacious hunting to completion. Others may identify with a wolf as a lone creature, vulnerable yet fierce in it sown right. None of them are wrong; they all looked inward to find the answer.