Cyndaquil isn't a Porcupine. Its based off of an Enchidna or Shrew. Its also Classified as the Fire Mouse Pokemon, making it the Chinese Zodiac representation of the Mouse.
While, yes Fennekin does break the chain as a Fox is not part of the Zodiac, though many support it representing the Dog as Vulpines are related to Canines. And with that theory...I dread it evolving into a Dog now.
I don't know what they meant by Evolution, but Grass Types used to be all reptilian based. Bulbasaur and Chikorita based off some kinda Dinosaur, Treecko a gecko, Turtwig was a turtle, Snivy was a snake. Chespin who is a Mammal breaks this cycle.
Water is the only thing with a close relationship as all Water Starters are Semi-Aquatic creatures.