Marsupials (metatheria) Flashcards
What skeletal features differentiate the metatheria from the eutheria?
- Epipubic bones
- Pouch support, locomotion
- Not present in the Thylacine (Tasmanian tiger)
- Skull: Large face area but small brain case
- Rest is similar to primitive mammal
What dental features differentiate the metatheria from the eutheria?
More teeth than eutherians (placentals)
3 premolars and 4 molars (less premolars than placental)
4 or more lower incisors - polyprotodont
2 lower incisors - diprotodont
What is unique about the reproductive systems of marsupials?
- Female system is doubled! 2 vaginas
- Males have a bifurcate penis to correspond this
Describe how flexible marsupial reproduction can be
Due to paired vagigal system and median birthing vagina:
Can have newborn attached to nipple, a fertilised blastocyst in uterus and a young at foot!
Marsupial young are extremely ——-
Altrical = requires significant parental care
Describe the features of marsupial young
Altricial:
- No eye pigments, no eyelids
- Cartilaginous skeletal segments
- Separation of heart ventricles incomplete
- Locomotor system is developed just enough to allow them to crawl through mothers fur to the pouch (start suckling immediately)
- Olfactory system also developed to help them find the pouch
- Well developed tongue and mouth muscle = suckling
What are the benefits of having altricial young?
- Physiologic and energetic costs is reduced
- No need to protect the embryo from maternal immune system
- Less risk for the female (extended pregnancy, large embryo …)
- Flexible repro
Name 2 costs of having altricial young
- Increased parental care
- Higher predation risk
- Young at higher risk of infection/disease
Give some reasons why there are many convergences between mammals and marsupials
Biogeography, habitat, body size, diet, fertility
