Exept that it only has mammals in it. Wikipedia articles are pretty good for that too, having broader scope than just mammals. Starting from the Eukaryotes page and climbing up the evolutionary tree should work in finding what you are looking for taxonomically(such as following evolutionary paths from water to land or from reptile to mammal):
It depends on the article, but the Scientific stuff is often put there by professors and such who usually put up the references as well. Many of those taxonomy articles looked well-written and had references in them. I guess it depends on professor, but Wikipedia has been recommended as a source in some of the University physics courses I've attended to.
We in our History of Illustartion/animation/design essays are allowed to use any internet source, but we have to include the full URL, the author if possible, and the date we accessed it, in case it is changed/moved or updated.