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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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Skull

evolutionary time

High #

bones

Low #

bones

Skull

Evolutionary tendency

Fusion of skull bones


Skull1

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




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)


Branchiocranium1
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)


Branchiocranium2
Branchiocranium

  • Branchial Arches (cartil. origin)

    • Support gills (Ceratobranchial & Epibranchial)

    • Help chewing (Pharingeal bones)







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

premaxilla

maxilla

mandible


Jaw suspension evolution

HYOSTYLIC slides along front of skull).

AMPHISTYLIC

AUTOSTYLIC

Jaw Suspension Evolution


Vertebral column
Vertebral Column slides along front of skull).

Precaudal

Caudal


Fins slides along front of skull).

  • Pectoral Girdle

    • Not attached to vertebral column

    • Attached to Skull

  • Pelvic Girdle

    • Not attached to vertebral column

  • Caudal Fin

    • Protocercal, heterocercal, homocercal


Fins slides along front of skull).

  • Median Fins

    • Sharks

      • Ceratotrichia (dermal)

      • Radials (cartil.)


Fins slides along front of skull).

  • Median Fins

    • Bony Fishes

      • Ceratotrichia

        (in larval stages)

      • Lepidotrichia (dermal)

      • Pterygiophores (cartil.)


Soft rays true spines
Soft rays True Spines slides along front of skull).

soft

segmented

branched

bilateral

hard and pointed

unsegmented

unbranched

solid


Skin slides along front of skull).


Scale types
Scale Types slides along front of skull).

  • 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
Scales slides along front of skull).

  • 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)


Scales1
Scales slides along front of skull).


PLACOID slides along front of skull).

COSMOID

GANOID


CYCLOID slides along front of skull).

CTENOID