Evolutionary changes in brain growth patterns and resultant skull base morphologies from sharks through humans (yellow arrows denote orientation of spinal cord and the foramen magnum).
Midsagittal spatial relationships of the human skull base skeletal elements and articulations in the late fetal period. Anteroposterior growth of the skull base depends on three synchondroses:
The short-faced animal model. Palatal view of cleaned and dried adult skulls of a cat (left), monkey (middle), and chimpanzee (right). Note the U-shaped dental arches and the shortened premaxillae relative to the other palatal components.
The long-faced animal model. Palatal view of cleaned and dried adult skulls (from left to right) of the rat, rabbit, dog, and baboon. Note the elongated premaxillae relative to the other palatal components and the reduced incisive foramen (if) in the dog and baboon skulls.
The "generic" animal model. Palatal view of cleaned and dried skulls of an adult rabbit (left) and rat (right). Note the elongated premaxillae (pm), the large incisive foramen (if), small maxillary and palatine components, and the V-shaped dental arch.
The "phylogenetically-closer" animal model. Lateral (occlusal) view of cleaned and dried skulls of an adult cat (top), dog (middle), and rhesus monkey (bottom). Note the multiple tooth classes, reduced post-canine diastema, and the interlocking "canine complex" in the cat and dog skulls.
Fitting appropriate animal models. Palatal view of a cleaned and dried adult human (left) and chimpanzee (right) skulls. Note the reduced incisive foramen (if), the U-shaped dental arch and the similarities in relativeproportions of the three palatal-midfacial components.