. Chordate morphology. Morphology (Animals); Chordata. sup squamosal frontal eta I parietal plisphenoid postporietal pterygoid palatine orbitosphenoid ^^^^| jugol squamosal alisphenoid basispherioid basioccipital exoccipital supraoccipital premaxilla. dentory^ basisphenoid exoccipital basioccipital supraoccipital Figure 3-16. Head skeleton of SO-mm foetal rabbit. A, lateral view; B, dorsal view with roof of left side removed; C, ventral view of skull, the lower |ow removed; D, medial v,ew of half of head. by the anteromedial center. A similar pattern appears to be followed by the rabbit
. Chordate morphology. Morphology (Animals); Chordata. sup squamosal frontal eta I parietal plisphenoid postporietal pterygoid palatine orbitosphenoid ^^^^| jugol squamosal alisphenoid basispherioid basioccipital exoccipital supraoccipital premaxilla. dentory^ basisphenoid exoccipital basioccipital supraoccipital Figure 3-16. Head skeleton of SO-mm foetal rabbit. A, lateral view; B, dorsal view with roof of left side removed; C, ventral view of skull, the lower |ow removed; D, medial v,ew of half of head. by the anteromedial center. A similar pattern appears to be followed by the rabbit (Figure 3-16). In man there are two or three pairs of centers enclosing the optic nerve foramen and extending medially to fuse at the midline. The third pair of centers, when present, is that in the pila pre- optica. The most medial pair is identified with the term presphenoid; however, since there is never a separate bone here in even young mammals (after weening), the term is superfluous. The "presphenoid" centers are best developed in the rat (Figure 3-17). In some insectivores there is ap- parently only one pair of centers for this bone, and this center appears in the preoptic pillar. These centers may re- main separated by the anterior part of the basisphenoid or join across the midline. There is some dermal extension of these centers in forming the definitive bone. The alisphenoids. orbitosphenoids, and pterygoids fuse 58 • OSTEOLOGY AND THE MAMMALIAN HEAD SKELETON. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jollie, Malcolm. New York, Reinhold
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