Noneutherian mammals: monotremes and marsupials
Phylogenetically isolated from other mammals
| ||Time of divergence from other mammals||Unique reproductive pattern
|| extremely altricial young, choriovitelline placenta
- General characteristics of the order
- Morphologically unique
- Have many reptilian characteristics
- Birdlike skull with elongated rostrum
- No teeth - Chew food with the tongue and bony plate at roof of mouth (echidna) or roughened gums (platypus)
- Pectoral girdle splayed as in reptiles
- Pelvic girdle mammal-like
- Epipubic bones that come up from
the pelvis along the ventral surface
- Lay eggs
- Incubate them like birds
- Have mammary glands and make milk
- No nipples
- Milk is secreted onto the abdominal fur (platypus) or into a temporary pouch and licked off the skin (echidna)
- Long periods of maternal care
- 1 offspring/year
- Echidna - one cool thing!
- Convergence with other myrmecophagous species
- Australian species eats ants and termites; New Guinea species eats earthworms
- Tube-like rostrum covered with leathery skin
- Long tongue coated with mucous
- "Digging" limbs (short, powerful, claws)
- Platypus - two cool things!
- Convergence with other amphibious and aquatic species
- It's venomous! Read more here if you're interested.
- Only males are venomous, and only during breeding season
- Venom produced in thigh gland
- Venom delivered through keratin ankle spur on hind leg
- General characteristics:
- What used to be the "order Marsupialia" is now 7 separate orders
Phylogeny and biogeography
New classifiation system based on incisor teeth and digits.
- Order Diprotodontia (kangaroos) - Diprotodont dentition and syndactylus digits
- Order Didelphimorphia (Virginia opossum) - Polyprotodont dentition and didactylus digits
- Examples of convergence between marsupials and placental mammals
- Now is much lower than it once was...
- Massive extinctions in Australia that may be the result of colonization by aboriginal humans.
- Later, more extinctions when Europeans reached Australia
- Competition with domestic livestock
- Clearing of habitat for agriculture
- Introduction of domestic species (eg. cats)
- Introduction of diseases for which native species had no immunity
- Interesting extinct species: