os·si·fy 
(ŏsə-fī′)
(ŏsə-fī′)v. os·si·fied, os·si·fy·ing, os·si·fies
v.intr.
1. To change into bone; become bony.
2. To become set in a rigidly conventional pattern: "The central ideas of liberalism have ossified" (Jeffrey Hart).
v.tr.
1. To convert (a membrane or cartilage, for example) into bone.
2. To mold into a rigidly conventional pattern.
[Latin os, oss-, bone; see ost- in the Appendix of Indo-European roots + -FY.]
os·sific (ŏ-sĭfĭk) adj.