I think I had the same problem, but I had to rebase and disjoint few elements like shield and hands for other reasons (mainly due to badly done assembly by the previous owner).
A
very sharp and thin blade was my friend through the process, but I had to use extreme care and proceed very slowly. Don't remember how do you call one in English, but I used this:
https://www.shan.com.pl/noz-do-tapet-nozyk-ostrze-duzy-mf11318-z-metalowa-prowadnica-p-1478.html (shop link)
Now how to do it, because its not simply cutting:
* find a spot where a foot leaves a bit of space between the base and the model and it looks solid (since all lizards are digigrade that should be back of the foot most of the time), stay away from protruding elements, such as claws or you will damage them
* alternate between making a small cut targeting rather the base than the model (this way you will cut mostly the glue or base and not the lizard foot itself) and movement to increase the gap (watch out to not break the blade!)
* if the foot vs base area is big alternate not only the movements, but also between feet to damage the glue equally and to not damage the other foot if you suddenly succeed with the first one
At this point you should have a disjointed model and the base and the model feet will have a bit of excess glue or even basing material on them. Remove that with file if needed as you want to have a plane surface on the feet again.
Its not as scary as it looks first and once I did that with bases I did that with shields and even hands.