The Later Developmental Features in the Skull of Sus barbatus barbatus

A bstract . Skull growth after eruption of the third permanent molar in Sus barbatus presents the following features:– Extension of maxilla accompanies eruption of the canine tooth. Following this additional growth takes place in the region of maxillary tuberosity. Meantime bodily size of the animal increases and there is a vertical expansion of upper or respiratory area of face. Fronto‐parietal forward growth overbalances maxillary extension, and face buckles down and back on cranium, as in the sheep, with sliding of zygomatic processes of malar and temporal on each other. This facial buckling terminates on closure of the coronal suture. Between the dates of closure of coronal and squamous sutures the swing of the face changes. There being no more growth above, that in the maxillary area causes the fronto‐nasal contour to increaae its forward concavity by adjustments in the hafting zone which runs from nasion to palato‐pterygoid plate. There is further sliding of malar and temporal zygomatic processes on each other, but it occurs in the reverse direction. Increase of the muscular scaffolding now occurs, more particularly for cranio‐vertebral musculature than for masticatory muscles. Zygomata move laterally. The lambdoid crests but not the sagittal enlarge. Some elongation of face follows by additions along the hafting line, mainly on the orbital side. Fronto‐nasal contour is not changed. The last skull modification is produced by great masticatory muscle development. Elevation of the sagittal crest exaggerates the already existing fronto‐nasal concavity, while extension and lateral movement of the zygomata indicate the increased size of the masticatory musculature. So‐called individual differences can thus be resolved into simple orderly growth changes,