posterior fontanelle posterior fontanelle the posterior fontanelle (lambdoid fontanelle, occipital fontanelle) is a gap between bones in the human skull (known as fontanelle), triangular in form and situated at the junction of the sagittal suture and lambdoidal suture. it generally closes in 6–8 weeks from birth. the cranial point in adults corresponding the fontanelle is called 'lambda' a delay in closure is associated with congenital hypothyroidism. posterior fontanelleskull at birth, showing frontal and occipital fonticulidetailsidentifierslatinfonticulus posteriorta98a02.1.00.029ta2433fma75440anatomical terminology