Noneutherian mammals: monotremes and marsupials

Phylogenetically isolated from other mammals

 Time of divergence from other mammalsUnique reproductive pattern
monotremes ~220 mya egg laying
marsupials ~175 mya extremely altricial young, choriovitelline placenta


I. Monotremes (Prototheria)

  1. General characteristics of the order

  1. Reproduction

  1. Echidna - one cool thing!



  2. Platypus - two cool things!

II. Marsupials (Metatheria)

  1. General characteristics:

  1. What used to be the "order Marsupialia" is now 7 separate orders

    Phylogeny and biogeography

    New classifiation system based on incisor teeth and digits.

    Examples



  1. Examples of convergence between marsupials and placental mammals

    Placental Marsupial
    cat quoll
    Artiodactyl
    skull
    kangaroo
    skull
    flying squirrel sugar glider
    mole marsupial moles (fossorial, insectivorous, vestigial eyes,
    no pinnae, robust forelimbs)
    marmot
    skull
    wombat
    (marmot-like teeth, minimal tail)
    wolf
    skull
    thylacine (see especially 3:57-4:40 of video)
    skull

  1. Diversity

    1. Now is much lower than it once was...
    2. Massive extinctions in Australia that may be the result of colonization by aboriginal humans.
    3. Later, more extinctions when Europeans reached Australia

      1. Competition with domestic livestock
      2. Clearing of habitat for agriculture
      3. Introduction of domestic species (eg. cats)
      4. Introduction of diseases for which native species had no immunity

    1. Interesting extinct species:

      Thylacoleo lion-sized, carnassial pair, retractile claws
      artist's rendering
      fossil skeleton
      Diprotodon Rhino-sized; largest marsupial ever known
      Museum recreation
      Skull
      Fossil skeleton
      Thylacosmilus sabre-tooth cat-like marsupial
      artist's rendering
      fossil skull