<prompt> Thinnest pa of the skullLambdoid sutureTemporal pa of bonePterionOcciput  <response>: The anterior pa of the floor of the temporal fossa is crossed by an H shaped suture where four bones,frontal,parietal,greater wing of sphenoid and temporal adjoin each other.This area is termed the pterion. REF.B D Chaurasias Human Anatomy VOL.3,Fouh edition 