A fire retardant is a substance that reduces flammability of fuels or delays their combustion. This includes chemical agents, but may also include substances that work by physical action, such as cooling the fuels, such as fire-fighting foams and fire-retardant gels.
These early mammals were small, insectivorous, nocturnal, hairy and warm-blooded. Warm-bloodedness is believed to have first evolved among the cynodonts, a late but successful group of mammal-like reptiles from which the mammals evolved.he Mammal-like Reptiles, or Therapsids first appeared about 285 million years ago near the begiining of the Permian which is well before the dinosaurs. They evolved quickly and many different groups arose.
As for it being specific to land mammals, my use of the word digits instead of fingers reveals that yes, it is not specific to land mammals. If you looked at the image in the convergent evolution link, you can see how fingers take form on the inside of a wing. Not all animals follow the 5 digit format, as you can also see in that picture, with the mammal creature, the bat, having a 5 digit format, with the pterosaur and bird differing.