Does the Devoted Tracker feat allow you to take an unconventional animal companion?

The paladin mount allows the character to take unconventional creatures as their mounts, such as dragons, magical beasts and things like that.

The druid/ranger animal companion must be an animal.

The Devoted Tracker feat (Complete Adventurer, p. 108) allows you to treat your mount as your animal companion.

Does it give any creature the bonuses, or does the creature need to be eligible be an animal companion to begin with?