Far from a complete list, this FAQ highlights several hundred of the more interesting examples of the thousands of historical species-to-species transitions documented in the fossil record at the time of writing. New examples are found almost every day, filling in our paleontological knowledge of life on Earth piece by piece. For brevity's sake, the author limited examples only to those lineages that left modern ancestors, which excludes the vast number of historical lineages we know about that did not. And, of course, this list only covers the Vertebrata subphylum, just a tiny portion of the enormous animal kingdom, not to mention life in general.

Also see Wikipedia's List of Transitional Fossils for more examples.

Great source!