. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. $68 Biology of the Vertebrates cipital parts becoming reduced until they do not participate in the condylar surface (Fig. 482). Mammals and the higher therapsids have two condyles, on the exoccipitals only, the condylar region of the basioccipital disappear- ing although the bone itself is not lost as in amphibians (Fig. 509). In the ventral trough anterior to the basioccipital most mammals develop a row of three unpaired, median bones: basisphenoid, presp
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. $68 Biology of the Vertebrates cipital parts becoming reduced until they do not participate in the condylar surface (Fig. 482). Mammals and the higher therapsids have two condyles, on the exoccipitals only, the condylar region of the basioccipital disappear- ing although the bone itself is not lost as in amphibians (Fig. 509). In the ventral trough anterior to the basioccipital most mammals develop a row of three unpaired, median bones: basisphenoid, presphenoid, and mesethmoid, with the last-named forming the dorsal part of the nasal septum (Figs. 483 and 500). Extending dorsally into each orbit from the side of the presphenoid is an orbitosphenoid. In tetrapods other than mam- mals the anterior part of the trough usually remains cartilaginous as pre- sphenoid and mesethmoid bones do not develop. ^--Interparietal \_-â- Parietal _ A â Supraoccipital \ ^Squamosal â¢Petromastoid . __-|âExoccipital rC^ ^_AA>r--Tyrnpanic ^jjj^xnj_ Basisphenoid. Frontal Alisphenoid \^ r N^ Orbitosphenoid ^s^\ \ Pterygoid Xvâ- Nasal -/^02 My Nasoturbinal'^5 0\^^^[^<^~ Maxillary v^â- Dentary"' ^Basihyal Fig. 483. Composite mammalian skull. Investing bones in outline; re- placing bones, dotted. IâXII, locations of the exits of the cranial nerves. (After Weber.) \\ .'â â «,-â =?â Basioccipital ""â --Tympanohyal Premaxillary Palatine ^"--Stylohyal $ Epihyal ^~~ Ceratohyal *»^ ^Thyrohyal In the otic capsule three bones are commonly laid down: a dorsal epiotic; a ventral, anterior prootic; and a ventral, posterior opisthotic. In mammals these three usually fuse to form the petromastoid. In birds the prootic forms most of the ear capsule, while the small opisthotic fuses with the exoccipital, and the small epiotic with the supraoccipital. Among reptiles the prootics are usually separate bones while the opisthotics
Size: 2133px × 1172px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
