Skeleton skin and scales
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Skeleton, Skin and Scales. evolutionary time. High # bones. Low # bones. Skull. Evolutionary tendency. Fusion of skull bones. Neurocranium (brain case) Branchiocranium (endoskeletal arches, original gill arch supports). Chondrocranium (original cartilagenous braincase)

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Skeleton, Skin and Scales

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Skeleton, Skin and Scales


evolutionary time

High #

bones

Low #

bones

Skull

Evolutionary tendency

Fusion of skull bones


Neurocranium(brain case)

Branchiocranium (endoskeletal arches, original gill arch supports)

Chondrocranium(original cartilagenous braincase)

Dermatocranium (dermal bones attached to skull)

Arches:

Mandibular

Palatine

Hyoid

Opercular

Branchial

Skull


Neurocranium


Branchiocranium


Branchiocranium

  • Mandibular Arch (cartil. & dermal origin)

    • Sharks

      • Palatoquadrate Cartilage (top jaw)

      • Meckel´s Cartilage (bottom jaw)

    • Bony Fishes

      • Premaxillae, Maxillae, Supramaxillae (top jaw)

      • Dentary, Angular (bottom jaw)

  • Palatine Arch (cartil. origin)


Branchiocranium

  • Hyoid Arch or Supensorium (cartil. Orig.)

    • Provides support and attachment to skull.

      • lower jaw (Quadrate)

      • opercular apparatus

  • Opercular Arch (dermal origin)

    • Protects gills (Opercule)


Branchiocranium

  • Branchial Arches (cartil. origin)

    • Support gills (Ceratobranchial & Epibranchial)

    • Help chewing (Pharingeal bones)


Lampreys


Sharks


Bony Fishes


Jaw evolution hypothesis


Viperfish mandible


Protrusible mouth (ascending process on premaxilla that slides along front of skull).

premaxilla

maxilla

mandible


HYOSTYLIC

AMPHISTYLIC

AUTOSTYLIC

Jaw Suspension Evolution


Vertebral Column

Precaudal

Caudal


Fins

  • Pectoral Girdle

    • Not attached to vertebral column

    • Attached to Skull

  • Pelvic Girdle

    • Not attached to vertebral column

  • Caudal Fin

    • Protocercal, heterocercal, homocercal


Fins

  • Median Fins

    • Sharks

      • Ceratotrichia (dermal)

      • Radials (cartil.)


Fins

  • Median Fins

    • Bony Fishes

      • Ceratotrichia

        (in larval stages)

      • Lepidotrichia (dermal)

      • Pterygiophores (cartil.)


Soft raysTrue Spines

soft

segmented

branched

bilateral

hard and pointed

unsegmented

unbranched

solid


Skin


Scale Types

  • Placoid

    • Sharks, rays and chimaeras

    • dermal and epidermal origin

    • Irrigated pulp cavity + dentine + vitrodentine

    • homologous to vertebrate teeth

  • Cosmoid

    • Lungfishes

    • originated by fusion of placoid scales

    • Two bone layers + cosmine + vitrodentine


Scales

  • Ganoid

    • Sturgeons, paddlefish and gars

    • modified cosmoid scale

    • Two bone layers + dentine + ganoine

  • Cycloid and Ctenoid

    • Bony fishes

    • evolved from ganoid scale (loss of ganoine)

    • Almost all dermal

    • Overlapping (shingle-like)


Scales


PLACOID

COSMOID

GANOID


CYCLOID

CTENOID


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