[C] Teleostomi: Osteichthyes

• • Endoskeleton comprised mainly of bone
  • Reversal in more derived lineages
  • Gradual progress from cartilage to bone skeleton 
  • Gas-filled swim bladder for neutral buoyancy 
  • 2 Main Groups 
  • Actinopterygii (Ray-finned fishes)
  • Sarcopterygii (Lobe-finned fishes)
• Tiktaalik: the Fishapod 

  • Late Devonian sarcopterygian
  • An intermediate link between fishes and land vertebrates
  • Shallow-water lifestyle 
  • Dorsoventrally flattened skull
  • Loss of operculum - defines transition from gill-breathing to almost lung based breathing 
  • Forelimb-ish pectoral fins
  • Robust internal skeleton but terminate in fin rays
• Actinopterygii

  • Ray-finned because of their distinctive fins
  • Supported by numerous slender, endoskeletal lepidotrichia
• Actinopterygian Divisions (based on ossification)

  1. Chondrosteans
  2. Holosteans
  3. Teleosts
• Actinopterygian Divisions (Based on derivations)

  1. Palaeonisciformes
  2. Neopterygii
• In Neopterygii, the notochord was replaced by an increasingly ossified vertebrae
• Sarcopterygii

  • Paired fins rest at the end of internal bony elements and soft muscles
  • External nostrils opening internally to the mouth (choanae)
  • Two main groups (dipnoans, crossopterygians)
• Material coating sarcopterygian fins

  cosmine (cosmoid scales)
• Caudal fin symmetrical, with equal areas of lobes

  Diphycercal