. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. SKELETON. 79 In other ganoids (holosteans and crossopterygians) the skull is much like that of the teleosts, differing in the extension forward of the cranial cavity. There are. na FIG. 78.—Median section of skull of mackerel (Scomber) after Allis. For letters see fig. 68. one (Amia) or two (Polypterus) gular bones developed between the rami of the lower jaw, and in Polypterus parietals, frontals and nasals fuse with age, and there are numerous small bones in the cranial roof, developed along the lateral line c
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. SKELETON. 79 In other ganoids (holosteans and crossopterygians) the skull is much like that of the teleosts, differing in the extension forward of the cranial cavity. There are. na FIG. 78.—Median section of skull of mackerel (Scomber) after Allis. For letters see fig. 68. one (Amia) or two (Polypterus) gular bones developed between the rami of the lower jaw, and in Polypterus parietals, frontals and nasals fuse with age, and there are numerous small bones in the cranial roof, developed along the lateral line canals. Amia has several splenials in the lower jaw. TELEOSTS (fig. 76-80) have a consider- able range of skull structure. In the lower groups like siluroids and cyprinids, the chondrocranium is largely persistent and the cranial cavity extends into the eth- moid region as in the higher ganoids. In other teleosts the trabeculae are ap- proximate between the orbits (tropibasic) and develop a thin interorbital septum which limits the anterior ends of the cranial cavity. The cartilage bones are more numerous. All four occipitalia are present, the occipital condyle being formed by basi- and exoccipitals. Basi-, ali-, and orbitophenoids occur, and besides ecteth- moids a pair of mesethmoid ossifications. In the otic capsule there are usually pterotic and sphenotic ossifications. The cranial roof is largely formed by the frontals and parietals, the latter fre- quently separated by a strong process of the supraoccipital. Several of the car- tilage bones are visible from above. The roof of the mouth is formed by the large parasphenoid and the vomers. Premaxil- laries (rarely lacking) and maxillaries FlG 79.—Dorsal view of skull of mack- form the upper jaw, both usually bearing erel, Scomber, after Allis; letters as in fig. 68. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of thes
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