Marsupials Flashcards
(30 cards)
Where are marsupials found ?
In Australia and the southern hemisphere (New Guinea)
Where are the oldest marsupial fossils found ?
In present day china and north America.
How have we documented the ancestral spread of marsupials ?
Through molecular analysis, Studying the fossil record and use of tectonic models
Describe the relationship between the Australian and south American marsupial groups.
A Single South American marsupial became the ancestor of the Australian marsupials
(Australian marsupials, within wider group of SA marsupials)
When did marsupials evolve ?
168 ya, In the early cretaceous period.
Describe the adaptive radiation of marsupials.
Evolved in Laurasia (Europe, asia, N America)
crossed from S America to Antartica and then Australia
Continents then began to split leading to considerable adaption of marsupials in isolated habitats.
How were marsupials able to cross from South America to Australia ?
Gondwana, giant land mass linking South America, Antarctica and Australia
How many species exist in the modern day ?
300 species of marsupial
How many orders of marsupial ?
7
Give the causes of marsupial extinction 3 million years ago
Placental mammals are thought to have hunted some marsupials to extinction
Give an example of the extreme diversity found within the marsupials.
Planigale and Adult red kangaroo
(20,000 times heavier)
Huge weight difference!
Give an ecological equivalent of the marsupial Sugar glider, from Australia
Eutherian
Northern flying squirrel,
North America
Give an ecological equivalent of the Eutherian Spotted hyena
Marsupial
Tasmanian Devil
Both have sloped hindquarters, Big jaws
Give the ecological equivalent of the marsupial Kangaroo
Eutherian
Patagonian Mara
Give the ecologically equivalent mole species
Southern Marsupial Mole
European Eutherian Mole
Why are marsupial and eutherian equivalents, analogous not homologous ?
They are not ancestral features
Instead characteristics due to CONVERGENT evolution
Define analogous
Are comparable due to similar morphological features
Define Homologous
Shared ancestry between species
When did the Eutherians evolve from the Marsupials ?
In the late Jurassic, 140 million years ago
Describe the difference in uterus horns between Eutherians and marsupials.
Eutherians have a 1 horned uterus
Marsupials have 2, 3 horned uterus
To fully fertilise the 2 horned uterus, what have some marsupial males evolved ?
Doubled lobed penis
e.g. Kangaroos
Describe a marsupials placenta.
Short lived
Not intricate
Nutrients are exchanged via the egg sac
What are the Bandicoots ?
A marsupial group consisting of 20 species who have developed placentas
However they are much smaller and lack villi
Describe the gestation period of marsupials in comparison to that of the eutherian
Much shorter (13-35 days) Eutherians much longer (45-650d)
