The Collaborative International Dictionary of English v.0.48:

Platy \Plat"y\, a.
   Like a plate; consisting of plates.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Platy- \Plat"y-\
   A combining form from Gr. platy`s broad, wide, flat; as,
   platypus, platycephalous.
   [1913 Webster] Platycephalic