Vertebrates

Major Clades

Hagfishes & Lampreys
  • ancient eel-like fish without jaws or a backbone (but do have vertebrae)
Cartilaginous Fishes (sharks & rays)
  • skeletons composed of cartilage
  • no swim bladders
Bony Fishes
  • have ossified (bony) endoskeletons
  • have swim bladders

3 clades:

  1. ray-finned fishes (most diverse vertebrate clade, ~27,000 species)
  2. lobe-finned fishes
  3. lung fishes
  4. 3rd lineage of lobefins gave rise to the land vertebrates
Amphibians (frogs, salamanders & caecilians)
  • live both on land and in water
  • most have poisonous skin
  • 6,150 species (most are frogs)
Reptiles
  • lay shelled eggs on land
    • amniotic fluid, shell keeps it from drying out
  • scales protect against desiccation (drying out)

^ further adaptation to life on land than amphibians

Ectothermic Reptiles (snakes, lizards, turtles & crocodilians)
Endothermic Reptiles (birds)
  • 10,000 species on earth
  • extant dinosaurs

Mammals

rodents, cats, ungulate, primates, whales

  • produce milk in mammary glands
  • hair (shared ancestral trait)
  • have highly efficient circulatory systems
  • kidneys (helps conserve water)

3 Types of Mammals

  1. monotremes: lack nipples but produce milk & lay eggs (EX: platypus & echidna)
  2. marsupials: give birth to live young early in development, so the young stay in a pouch (EX: kangaroos & koalas)
  3. placental mammals: have longer pregnancies & complex placentas
    • diversified 60-100 MYA
    • 5,010 species of placental mammals