| DeathRitual#4977 |
He is my take on it. "the alchemist can have the tumor detach itself from his body as a separate creature vaguely resembling a kind of animal suitable for a familiar" does not actually specify if it is a animal but rather ' resembling'. So it's hard to use those details to prevent it from being whatever you want it to be. Meanwhile, it is clearly stated to be a familiar in the next line. "The tumor has all the abilities of the animal it resembles (for example, a batlike tumor can fly) and familiar abilities based on the alchemist’s caster level.
The only real issue with this coming into play with a Improved Familiar is the size of the creature rather than it's type. It specifies the size of the tumor is ,"The alchemist creates a Diminutive or Tiny tumor on his body".
Basically, if you can find a familiar that is tiny or Diminutive, then it should in theory work.