The improved familiar feat allows a higher level arcane spellcaster to get a, well, improved familiar. However the Special Abilities for these familiars is not listed.
For some of these (Celestial Hawk, Dire Rat, Fiendish Viper) the special ability is "obviously" the same as their non-upgraded version; but what about the others (Stirges, Elementals, etc) that have no mention in their monster description sa to any familiar bonuses.
Imps at least have a brief mention of some powers, but no indication as to their associated bonuses.
So the question is:
What special ability do non-templatised improved familiars give? None? Is it just a prestige thing?
Also; is my assumption that the templatised familiars give the same special ability as their normal creature type. Is this correct?