Skeleton, Skin and Scales

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Skeleton, Skin and Scales
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Skull
Evolutionary tendency
Fusion of skull bones
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Skull

• 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

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Neurocranium
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Branchiocranium
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Branchiocranium

• Mandibular Arch (cartil. dermal origin)
• Sharks
• Palatoquadrate Cartilage (top jaw)
• Meckels Cartilage (bottom jaw)
• Bony Fishes
• Premaxillae, Maxillae, Supramaxillae (top jaw)
• Dentary, Angular (bottom jaw)
• Palatine Arch (cartil. origin)

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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)

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Branchiocranium

• Branchial Arches (cartil. origin)
• Support gills (Ceratobranchial Epibranchial)
• Help chewing (Pharingeal bones)

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Lampreys
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Sharks
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Bony Fishes
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Jaw evolution hypothesis
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Viperfish mandible
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Protrusible mouth (ascending process on
premaxilla that slides along front of skull).
premaxilla
maxilla
mandible
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Jaw Suspension Evolution
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Vertebral Column
Precaudal
Caudal
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Fins

• Pectoral Girdle
• Not attached to vertebral column
• Attached to Skull
• Pelvic Girdle
• Not attached to vertebral column
• Caudal Fin
• Protocercal, heterocercal, homocercal

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Fins

• Median Fins
• Sharks
• Ceratotrichia (dermal)
• Radials (cartil.)

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Fins

• Median Fins
• Bony Fishes
• Ceratotrichia
• (in larval stages)
• Lepidotrichia (dermal)
• Pterygiophores (cartil.)

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Soft rays True Spines
soft segmented branched bilateral
hard and pointed unsegmented unbranched solid
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Skin
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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

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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)

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Scales
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