poom tetrahedron octahedron outerplanar 0N Qdg sidewise Wagney deltohedron polyhedron dehisces hexeract zooids rhombic mesial Peuterey rhombi mesodermal BaCl2 supralateral Gussfeldt icosahedron dodecahedron Parascylliidae Satnami seked mQpp icosidodecahedron dipyramids parametrium mukh