Maya has a Polygons reduce tool, but it doesnt realy do that good of a job.. Geometry gets kinda messed up...
and normally doesnt come out very clean, atleast with my expirence..

Probably best to just remodel what you have..

You could, Just start deleating edges, and left over Verts..but, it'd most likely be quicker to just click the cylinder button and change it to 8 in the imputs..lol

G