Figure 3.

Fusion of the upper lip in human (A) and chicken (B) embryos reveals structural similarities. Across amniotes, the face is assembled from five main craniofacial prominences: the frontonasal mass (fnm), lateral nasal prominence (lnp), medial nasal prominence (mnp), maxillary prominences (mxp) and the mandibular prominences (md). The primary palate (upper lip/beak and nasal cavities/nasal pits [np]) forms from the fusion of the maxillary and lateral nasal prominences with the medial nasal prominence (highlighted in blue), although there is some variation in this process across different lineages [92].