Animal companion prestige classes?

[arcanine]

The only on I can think is is mammoth rider. But that won't help Druids or bloodriders. Because their is no spell progression. Do ouy guys know of any good ones that help?

[Joynt Jezebel]

One level of Mammoth rider allows you to increase the size of your annimal companion to huge, so its worth thinking about anyway.

[Deadmanwalking]

Boon Companion makes a whole 4 levels of any one Prestige Class (including one with spellcasting) an Animal Companion Prestige Class.

Not exactly what you're looking for, I know, but it helps.

[Dafydd]

Nature Warden, but the prereq pushes the class back a few levels.

+4 BaB, Animal Companion, Favored Terrain class feature, Wild Empathy, 5 ranks in KN Nature, Handle Animal, Survival, KN Geogrophy.

There is Lay of the Land feat, which does give the Favored Terrain ability, but that requires Animal Focus, so yeah, it is really just trading 1 class dip for another (admittedly it is a smaller dip). Still not sure how a single class druid could get into the class.

There is also Evangelist, but that requires Deific Obediance. Does improve all you class abilities, making you only 1 level behind.

[UnArcaneElection]

Green Faith Acolyte also progresses your Animal Companion and your spellcasting (no lost levels), can be entered after Druid level 5 or Oracle 6 (no need for Ranger dip). It even gives you an Animal Companion if you don't already have one, in case you are a Druid that went with a Domain, or Druid of some archetype that traded it out, or an Oracle, and Boon Companion makes up 4 out of 5 levels of the Animal Companion progression delay, or 4 out of 6 levels if you started as Oracle other than Oracle of Nature with Bonded Mount.

Another way exists to get an Animal Companion up to your full character level without using a non-spellcasting class, no matter what your spellcasting classes are, but it's really feat-intensive: Nature Soul, Animal Ally, Boon Companion (the last being not technically required, but if you don't get it, your Animal Companion is 3 levels behind, unless you gain enough levels in an Animal Companion class, which defeats the purpose of taking this feat chain).

[Hmm]

Evangelist Prestige Class, especially if you're a worshipper of Erastil.

The Evangelist will completely align with your preexisting spell-casting class (save one level) and the Erastil boons are great if you have an animal companion.