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

Skeleton, Skin and Scales


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


Skeleton skin and scales

Neurocranium


Skeleton skin and scales

Branchiocranium


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)


Lampreys

Lampreys


Sharks

Sharks


Bony fishes

Bony Fishes


Jaw evolution hypothesis

Jaw evolution hypothesis


Viperfish mandible

Viperfish mandible


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

AMPHISTYLIC

AUTOSTYLIC

Jaw Suspension Evolution


Vertebral column

Vertebral Column

Precaudal

Caudal


Skeleton skin and scales

Fins

  • Pectoral Girdle

    • Not attached to vertebral column

    • Attached to Skull

  • Pelvic Girdle

    • Not attached to vertebral column

  • Caudal Fin

    • Protocercal, heterocercal, homocercal


Skeleton skin and scales

Fins

  • Median Fins

    • Sharks

      • Ceratotrichia (dermal)

      • Radials (cartil.)


Skeleton skin and scales

Fins

  • Median Fins

    • Bony Fishes

      • Ceratotrichia

        (in larval stages)

      • Lepidotrichia (dermal)

      • Pterygiophores (cartil.)


Soft rays true spines

Soft raysTrue Spines

soft

segmented

branched

bilateral

hard and pointed

unsegmented

unbranched

solid


Skeleton skin and scales

Skin


Scale types

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

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)


Scales1

Scales


Skeleton skin and scales

PLACOID

COSMOID

GANOID


Skeleton skin and scales

CYCLOID

CTENOID


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