I read in the Direct3D9 help (emphasis mine) :
Direct3D 9 supports points, lines, triangles, and grid primitives. These have been extended to support higher-order interpolation beyond linear. While triangles and lines have spatial extent, until now they were both rendered using linear interpolation. In Direct3D 9, Direct3D supports rendering of these primitive types using higher order, up to quintic, interpolation. Furthermore, a new quad primitive type is now supported. This new type can also be rendered with higher-order interpolation.
This leads me to believe that Direct3D9 supports quads, but I can't find anything resembling D3DPT_QUADLIST in the Direct3D9 include files, so is the help wrong, or am I missing something obvious here?