Vertebrate Story 3b

• Vertebrates: Synapomorphies (shared derived characters)

  • multilayered epidermis (skin - many cells thick)
  • chambered heart (unidirectional flow )
  • well developed multipart brain (for brain, midbrain and hindbrain)
  • 10-12 cranial nerves and spinal motor nerves (concentrated nerves, not in protochordates)
  • neurons
  • neural crest
• Vertebrates: Neural Crest - neurulation

  • Vertebrates have face - protochordates do not
  • parts of cranium
  • adrenal tissue
  • cornea
  • melanocytes
  • -----------
  • Neural crest ->
  • part of meninx
  • thyroid (endostyle)
  • dental papilla
  • sensory ganglia
• Vertebrates: Skeleton (trends in evolution)

  Protochordates - No skeleton

  • Bony or cartilaginous skeleton
  • some taxa tend toward bone and others to cartilage
  • trend from dermal to internal skeleton (endoskeleton was previous cartilage but become ossified)
  • Cranium to protect brain and cranial sense organs
  • development varies in major taxa
• • Vertebrates: Skeletons (trends in evolution)
  • Trend for vertebrae to replace notochord in function
  • many primitive vertebrates lack apparent vertebrae hence the alternate taxon: Craniata (better than the name vertebrata)
  • agnathans with neural and or haemal arches
  • most jawed vertebrates with centra that displace the notochord
  • development and elaboration of the appendicular skeleton (jawed)
• Vertebrates: Skeletons (trends in evolution)

  • sharks mustve lost their bony skeleton, this could be becasue instead of dwelling at the ocean floor they are now higher swimmers
  • cranial kinesis
• Vertebrates: Skeletons (trends in evolution)

  • Axial Skeleton
  • more active lifestyle - evolution trend for centrum
  • axial compression resistance - better for swimming and locomotion, make it easier to support heavier body weights
  • Centrum - evolved independently, (sharks/ bony fish)
• Vertebrates: Skeletons (trends in evolution)

  • Appendicular Skeleton
  • no appendicular body in jawless vertebrates
• Vertebrate trends

  • more active lifestyle
  • larger body size
  • ciliary feeding to muscular pump
  • filter feeding to bulk feeding (jaws)
• Vertebrate history - know this

  
• Myxiniformes - hagfish (most primitive)

  • temperate marine
  • no scales or bones
  • no appendicular
  • cartilage in head
  • degenerative eyes (found in 100M deep waters, eyes not useful)
  • non practicing hermaphrodites (testes and ovaries)
• Myxiniformes - hagfish (most primitive)

  • isotonic to seawater - primitive characteristic
  • single median nostril
  • single semicircular canal
  • keratinous teeth on tongue
  • scavengers with slime glands (can knot itself)
• Petromyzontiformes - lamprey

  • keratinous teeth on tongue and oral disc
  • no tentacles
  • no slime gland
  • worldwide distribution
  • anadromous of FW
  • metamorphosis with ammocete larvae
  • many not parasitic FW
  • migrate upstream to mate then die
• Petromyzontiformes - lamprey

  • Sea lamprey - atlantic - now in the great lakes
  • caused major decline in lake trout and whitefish
  • extensive control measures now in place (5 million a year)
• Gnathostomata - living jawed vertebrates

  • loss of anteriormost pharyngeal arches
  • elaboration of one arch into jaws
  • palatoquadrate and Meckel's element
  • Elaboration of next arch to support the jaws (hyoid arch)

  
• Gnathostomata - living jawed vertebrates

  • includes all extant vertebrates other than cyclostomes
  • first appeared in silurian (400M years ago)
  • bony exoskeleton reduced (heaviness reduced)
  • Stomach becomes specialized
  • Appendicular skeleton and paired fins (pectoral and pelvic girdle)
  • adaptive radiation (massive diversity)
• Gnathostomata -

  Jaws

  • add form and strength to mouth
  • braced against cranium yet mobile
  • evolution of the new behaviour: bulk feeding
  • Paired fins
  • Paired fins - allow for precise control of movement and position
• Chondrichthyes - sharks

  • lost bone (agnathans have bone)
  • calcified cartilage but not true bone
  • no swim balder (use oils in liver)
  • Two lineages (Elasmobranchii and Holocephali )
  • Placoid scales structured similar to teeth
• Osteichthyes - probably evolved in fresh water

  • all extant gnathostomes except chondrichthyes
  • bony endoskeleton - synapomorphies
  • pair of ventral lungs primitively
  • cosmoid and ganoid scales primitively
  • trend to loss of enamel and reduction in weight
• Actinopterygii (ray -finned)

  • Ray finned fishes with fin rays supported by lepidotrichia
  • trends in symmetrical tail- types of tail - homatacrite (best for swimming
  • fused dorsal swim bladder in modern clades
  • Teleostei - 26000 species
  • Non- teleosts - 49 species
• Sarcopterygii

  • all extant Oseichthyes other than Actinopterygii
  • fins with internal skeleton of bone and muscles
  • Actinistia (Coelacanth) and Rhipidistia
• Rhipidistia

  • lungfishes (Dipnoi) and tetrapods
  • Labyrinthodont dentition (grooves in the teeth) with enamel folding inwards creating a ridged exterior
  • skeleton extends to the fin muscles also
• know this

  
• Tetrapods

  • limbs with digits (chiridium)
  • vertebrae with interlocking processes for support on land
  • vertebrae differentiated
  • Atlas - nod up and down
  • Axis_ left and right
• Lissamphibia

  • mucous and granular glands
  • loss of many bones, rigidification of skeleton
  • much variation in reproduction
  • Urodela=Caudata- some lost in lungs
  • Salientia - Anura - all lost tail
  • Gymnophiona - lost legs
• Amniotia

  • shelled egg with 3 extra embryonic membranes
  • Amnion - (protection)
  • Allantois - wastes, gas exchange
  • Chorion - gas exchange
  • embryonic cells grow around the cell and keeps the embryo protected
• Temporal openings

  
• Temporal openings across vertebrates

  
• Continued

  
• Sauropsida

  • testudinata- turtles
  • lepidosauria - lizards and snakes
  • archosauria - crocodiles and birds
• Aves

  • bipedal, forelimbs modified into wings
  • feathers, retain epidermal scales on legs
  • skull with a single occipital condyle - with the atlas - humans have 2
  • no urinary bladder, excrete uric acid in feces
  • expanded brain case, antorbital fenestra
  • pneumatic bones
  • diapsid
• Synapsid (Mammals)

  • Hair, sebaceous and sweat glads
  • skull with two occipital condyles
  • Inner ear with 3 ossicles
  • red blood cells without nuclei
  • primitive characteristic - glands make urea
  • mammals - first endotherms - high metabolism - used to be night dwellers and stay warm at night
• Synapsida (mammals)

  • monotremes (early jurassic) (3 species)
  • evolved north america (early cretaceous)