A defect in membranous ossification causes a rare syndrome called cleidocranial dysostosis. It is characterized by three cardinal features: (a) Varying degrees of aplasia of the clavicles; (b) increase in the transverse diameter of cranium, and (c) retardation in fontanelle ossification (Srivastava et al, 1971). It may be hereditary or environmental in origin. EXPLAIN PLS