The Radiation of Osteichthyes, the Bony Fish: ray-finned fish; lobe-finned fish; limbed vertebrates

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  • The Radiation of Osteichthyes, the Bony Fish: ray-finned fish; lobe-finned fish; limbed vertebrates
    • Diagnostics
      • Extensive exndoskeleton ossification
        • Endo and exo skeleton have succedded in vertebrate evollution
          • Perichondral ossification: bone arising from precursor cartilage develops on surface of cartilage
          • Endochondral ossification: bone develops from within cartilage mass as the cartilage template becomes degraded
        • Endo: Cartilage bones e.g. vertebrae, ribs, limb bones
        • Exo: Dermal bone e.g. skull roof bones, dentary, clavicle, gastralia, scale of fishes, osteoderm
        • Membrane bone e.g. centra of teleosts, sesamoid, orbitosphenoid of the Amphisbaenia
        • In osteichthyansthe neurocranium is a solid structure due to extensive ossification
          • Neurocranium is articulated with the palatoquadrate via an articulation (basipterygoid process)
      • Rooted teeth
        • Develop in dermal bones lining the margins of the mouth (upper premaxilla and mailla; lower dentary) as well as dermal bones that surround the primordial and embryonic upper palatoquadrate cartilage and lower Meckel's cartilage
        • Close integration of between dentine and enamel, built by specific sets of cells
      • Primitively 4-plated sclerotic ring
      • Medial adductor muscles in lower jaw (muscles of inside jaw attached to skull)
        • Since ancestor of ray fish... few bones have shifted very little, as their spatial relationship stays relatively the same
      • Conserved bone pattern in skull roof
      • Large bones in skull and pectoral girdle
      • Bony fin rays
        • Bony, bilaterally paired, segmented
        • Originate from modified scales?
        • usually composed of bone, but in early osteichthyans dentina dn enamel were also present (segmented and appear as a series of stacked disks)
        • Genes coded for production of certain proteins; it is suggested that the evolution of the tetrapod limb is related to the loss of these proteins
        • Support medians fins
      • Swim bladder (some fish; others it is now a lung)
        • Lungs were added to pre-existing gills
        • Swim bladders originated from modified lungs
      • Operculum
        • Protects gill chamber
      • Various scale types
        • Ganoid (gar; bowfins, bichirs, sturgeons)
          • Heavy and inflexible; rhomboid; peg and socket articulations; little or no overlap
          • Inner layer of scale is lamellar bone; a cosmine (dentine) layer is on top, then an enamel-like ganoine, which is then covered by ganoine
        • Cycloid (salmon; and roaches)
          • Leptoid
            • Grow through peripheral addition of concentric layer
            • Thin, flexible
            • Ctenoid (bass; perches, gobies)
        • Ctenoid (bass; perches, gobies)
        • Placoid (shark)
        • Leptoid
          • Grow through peripheral addition of concentric layer
          • Thin, flexible
      • Haemal arches protect blood vessels ventral to notochord (which isn't ossified). Ribs protect notochord in trunk region. Neural arches protect nerve chord dorsal to notochord
    • Supraneurals may extend from neural arches.
    • Intercalary ossifications form between neural or haemal arches

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