To make the comparison of Fennekin to the dog zodiac is completely ignoring the meaning of the dog zodiac. Even though both foxes and dogs are canines, they represent completely different things in Chinese lore. In both Japanese and Chinese folklore, foxes are tricksters, while the dog is noble and stoic.
Not to mention how much of a stretch it is to compare the Cyndaquil line to the mouse zodiac. Since the 2nd generation it has been clear that there was no attempt at following a theme and the Chinese zodiac certainly isn't it.
Chimchar and Emboar are only loosely based as well, the real inspiration comes from the Chinese epic - Journey to the West. With Infernape being Sun Wukong and Emboar being Zhu Bajie.
I just wish this theory would die off, it makes no sense.
I'll continue with the Water starters, with the trend being that they are all amphibious, meaning that they are able to live on land or in the water. This is less of a trend but more of a 'duh. The point of the starter Pokemon is to be the first Pokemon to be handed to a beginner trainer, having a water-type Pokemon not be able to work well above the water defeats the purpose, such as having a fish or something else that doesn't have legs. So does that make it a trend? Sure, in the sense that there is a trend that all starter Pokemon have legs, or that all Grass starters incorporate some variation of the color green. Beyond the vagueness that is "amphibious" there is no other relation between a turtle, a crocodile/alligator, a mudpuppy or axolotl, a penguin, an otter, and a frog.
The grass trend stated earlier is equally as vague, but even with its vagueness, still fails to incorporate all of the grass starters in a neat little package. With Bulbasaur, the first grass starter having features that resemble both a Dicynodont on one hand, and the common toad on another, doesn't really hit home the start of the "Evolution of Life" trend. Just going through geologic time and the fossil record. The Dicynodont is Permian in age which is the oldest of the bunch so that checks out, however Turtwig the turtle has fossils as early as the Triassic, which precedes the earliest known fossils of geckos (Treecko) and sauropods (Chikorita) which are most common during the Jurassic. Snivy, as a snake with legs goes back to the Jurassic period in the fossil record, and finally Chespin the odd one out of the previous "known" trend of them being all reptiles or reptile-like, sits as a hedgehog, with origins only to the Eocene epoch, 50 My after the Cretaceous. So what does this all tell me? That there isn't a specific order of ages of these creatures, nor a natural progression of evolution.
I could go on, but I think I'm made my point here, trends like these and other similar fan-made trends for various other aspects of Pokemon hold very little water when The Pokemon Company seems more interested in their own agenda and with the Pokemon we have, that agenda is largely random, or rooted in other, more obvious inspirations that don't carry themselves between Pokemon generations.
