[silkythreads (OP)]

==If a species is ....==

*** A group of "organisms" capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not (normally) happen.

So...."NORMALLY" What are the names of "mammal species" that CAN interbreed ?  Sexual intercourse only.

[Chemistry4me]

Your question makes no sense to me I'm afraid. But horse + donkey = infertile offspring

[graham.d]

I guess you use the phrase - "sexual intercourse only" - as opposed to use of genetic manipulation. There are quite a few dog breeds that could not have sexual intercourse, because it would be physically impossible, but could be cross-bred by artificial means.

As I understood it, the definition of the word "species" is a group of animals capable of interbreeding. According to wikipedia, however, this extends to the offspring being fertile too. It also says that there are other definitions.

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