Skeleton Skin and Scales Skull Evolutionary tendency Fusion

Skull Evolutionary tendency Fusion of skull bones High # bones evolutionary time Low #

Skull • Neurocranium (brain case) – Chondrocranium (original cartilagenous braincase) – Dermatocranium (dermal bones

Branchiocranium • Mandibular Arch (cartil. & dermal origin) – Sharks • Palatoquadrate Cartilage (top

Branchiocranium • Hyoid Arch or Supensorium (cartil. Orig. ) – Provides support and attachment

Branchiocranium • Branchial Arches (cartil. origin) – Support gills (Ceratobranchial & Epibranchial) – Help

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

Jaw Suspension Evolution HYOSTYLIC AMPHISTYLIC AUTOSTYLIC

Fins • Pectoral Girdle – Not attached to vertebral column – Attached to Skull

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

Fins • Median Fins – Bony Fishes • Ceratotrichia (in larval stages) • Lepidotrichia

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

Scale Types • Placoid – – Sharks, rays and chimaeras dermal and epidermal origin

Scales • Ganoid – Sturgeons, paddlefish and gars – modified cosmoid scale – Two

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Skeleton, Skin and Scales

Skull Evolutionary tendency Fusion of skull bones High # bones evolutionary time Low # bones

Skull • Neurocranium (brain case) – Chondrocranium (original cartilagenous braincase) – Dermatocranium (dermal bones attached to skull) • Branchiocranium (endoskeletal arches, original gill arch supports) - Arches: - Mandibular Palatine Hyoid Opercular Branchial

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 mandible

Jaw Suspension Evolution HYOSTYLIC AMPHISTYLIC AUTOSTYLIC

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 rays soft segmented branched bilateral True Spines 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