Diogenes Laertius was more of a biographer or historian of philosophy than an actual philosopher.  There were several philosophers in the ancient world named Diogenes.  On page 22 of the book he mentions another one, Diogenes of Apollonia.  

I think the most famous Diogenes was a guy that lived in the 4th century BC.  He was kind of a kook (in my opinion) who thought that men should reject society and live without any more luxuries than were absolutely necessary.  He lived in tub or barrel turned on its side.  Sounds like some envrio wackos (another editorial opinion) today.  Nevertheless, Alexander the Great is said to have respected him, and the two had a famous encounter. 

Chuck, you are right that Pythagoras was originally from Greece.  He was born on an island off the coast of what is now Turkey, then called Ionia.  As book points out, we aren't sure what he exactly did or thought, but if what they say about him is true, he deserves a lot of credit.  He thought that math one of the most fundamental things in the universe.  Things do happen in rhythms and patterns.  That's what modern physics is all about.  He recognized the relationship between numbers and music, and thought music to be an integral part of reality as well.  He took all this to a religious extreme, and his pantheistic religion was all wrong, but he does deserve credit for some insight.