how many animals have we discovered to now be extincted (no dinosaurs please)?

Answer 1

Approximately 99.9% of all species that have existed are extinct. That includes all the dinosaurs. There are approximately one million species alive on the planet today. I'll let you do the maths to work out how many species are extinct.

Answer 2

There is really no way to tell an exact number because we are still discovering prehistoric animals. Here is an interesting site you should browse through.

http://en.wikipedia.org/wiki/Extinct_animals