Totem Druid
The Totem Druid is a Druid Variant Class in Dungeons & Dragons 3rd Edition featured in the pages of Dragon Magazine #335. As the name suggests, these are druids from a culture that worships specific totem animals, and consequently their druidic magic is "filtered" through this reverence for a particular bestial spirit patron.
This makes them one of the simplest variant classes from a mechanical perspective; aside from gaining Natural Spell as a bonus feat at 2nd level and gaining the Totem Speech (Ex) ability at i8th level, which lets them use human language as an animal and speak to their totem beast at-will, it simply restricts the druid's animal companion and wild shape ability.
In short: a totem druid can only take a regular or Dire Animal version of their totem animal (the "listed" totem animals in the article are ape, bear, eagle, horse, shark, snake, tiger or wolf, but you can easily mod those for your own setting) as an animal companion, and they can likewise only assume the shape of their totem animal - a regular one from 1st level, a dire one from 6th level, a celestial or fiendish one from 10th level, and a celestial/fiendish dire one from 16th level.
On the plus side, the totem druid counts as being 2 druid levels higher to determine both the special abilities of their animal companion and if they can take a Dire Animal as a totem companion.
Pathfinder[edit]
Pathfinder would also attempt something akin to the Totem Druid as well in the APG, though now as archetypes, all being labeled as (Animal) Shamans, and unique from the animal domains introduced in Ultimate Magic. On one hand, the aspect of being able to only bond to one type of animal and be extra good at talking to them. On the other hand, these all sacrificed poison immunity (not the worst thing to lose, though it is baffling if you picked Serpent Shaman) and the rather fluff A Thousand Faces capstone feature.
In exchange, these shamans can choose between either having a pet of the same type or a limited choice of thematically appropriate Cleric Domains. The shamans can also pick from a few buffs to channel as a not-quite transformation that can talk to their totem beast a few times each day on top of some bonus feats from level 9 and every four levels afterwards. While they can wild shape into any animal they want, trying to transform into anything aside from their totem animal makes their effective level two levels lower, while buffing transformations into their totem animal by adding +2 to their effective level. If they cast Summon Nature's Ally to call in some totem beasts, they can speed up the spell to a standard action instead of a full round and the summons get some temp HP as well - on top of the option to either reduce their level by slapping the Young template or raise their level by adding the Advanced and/or Giant templates.
Unique among these is the Dragon Shaman, if only because it was mixing dragons (which can't be taken as a pet - drakes would be introduced far later and with plenty of restrictions like a unique archetype - but they could fly by channeling aspects of them as well as a bonus ability that lets natural attacks when transformed deal elemental damage) with lizards (they can only take crocodiles or monitor lizards as pets, they get benefits from turning into or summoning lizards, and they can speak to lizards).