The coronal plane and the sagittal plane are examples of longitudinal planes. It is perpendicular to the coronal plane and sagittal plane. The anterior fontanelle is where the metopic, sagittal and coronal sutures meet. It allows three-dimensional evaluation of the axial, coronal and sagittal plane. The bregma is formed by the intersection of the sagittal and coronal sutures. They are also occasionally seen within the sagittal and coronal sutures. Instead, sharp "lines" are formed at the sagittal and transverse foci. The radius of the condyles' curvature in the sagittal plane becomes smaller toward the back. Its skull is long and low with strong occipital and sagittal crests. In upright vertebrates, the sacrum is capable of slight independent movement along the sagittal plane. It moves the foreflippers in a transverse, rather than a sagittal, fashion. Saddle joints are said to be biaxial, allowing movement in the sagittal and frontal planes. The degree of kyphosis can be measured by Cobb's angle and sagittal balance. The shell is typically bilaterally symmetrical, with the hinge lying in the sagittal plane. Its skull is narrow and elongated with a pronounced sagittal crest.