What is the difference between tuberculo-sectorial and dilambdodont teeth?

Posted: 10 Mar 2015 10:54 PM PDT

Their descriptions are more or less the same, in that they form W-shaped ridges on the occlusal surface of teeth. so why the two terms? I can't seem to find a decent answer online, not even in mammalogy books, hence I resort to YA. Hopefully I get a decent answer. Thank you very much.