Learn more. The other third live mostly in South America A marsupial is born in a very incomplete state. Marsupials have an extra pubic bone, the epipubic bone, to support their pouch. Australian marsupials can be categorised by what they eat into 3 groups: Dasyurids - these are the meat-eating marsupials: quolls, the tamanian devil, tasmanian tiger, numbats, dunnarts, antechinus.
Peramelemorphs - these are the omnivorous marsupials: bilbies and bandicoots. Diprotodonts - these are the largely herbivorous marsupials: kangaroos, wallabies, possums, koalas, wombats. Back to top. Once in South America, marsupials and their close relatives had a field day, diversifying like crazy within 2 million to 3 million years after arriving, Beck said.
For instance, marsupials and their close relatives evolved into bear- and weasel-size carnivores, and one even evolved saber teeth. Others evolved to eat fruits and seeds. Many of these marsupials went extinct between then and now, but South America is still a marsupial hotspot today. There are more than species of opossums, seven species of shrew opossums and the adorable monito del monte Dromiciops gliroides , whose Spanish name translates to "little monkey of the mountain.
On a side note, within the last 1 million years, one of South America's opossums traveled north and now lives in North America. This is the Virginia opossum Didelphis virginiana , the only marsupial living north of Mexico, Beck said.
Also, opossums belong to a different order than possums. Possums are native to Australia and New Guinea, are closely related to kangaroos, and have a number of anatomical differences, such as enlarged lower incisors, that the South American opossum lacks, Beck said. So, how did marsupials get from South America to Australia?
Up until about 40 million to 35 million years ago, both South America and Australia were connected to Antarctica, forming one giant land mass. At that time, Antarctica wasn't covered with ice, but instead with a temperate rainforest, and "it was not a bad place to live," Beck said. It appears that marsupials and their relatives bounded down from South America, strode across Antarctica and wound up in Australia, Beck said.
There's even fossil evidence: On Antarctica's Seymour Island, there are fossils of marsupials and their relatives, including a close relative of the monito del monte, Beck said. The oldest fossil marsupials from Australia are found at a million-year-old site called Tingamarra, near the town of Murgon in Queensland, Beck said. Some of the fossil marsupials at Tingamarra are similar to those in South America. However, fast bipedal hopping is only an effective means of locomotion in deserts, grasslands and other open habitats free of overhanging woody vegetation , which became widespread in Australia much later, in the last 15 million years or so.
Hopping is similar to galloping in that energy is stored in elastic tendons between strides, so these gaits might be energetically equivalent solutions for fast or long-distance locomotion. Australian marsupials evolved in many ways to meet the challenges of drier habitats over the last 15 million years. Teeth, for example, reflect adaptive changes from browsing on woody vegetation in moist climates to grazing on grasses in arid climates. Kangaroo ancestors were quadrupedal walking on four legs most of the time in forested habitats and became progressively more bipedal as habitats dried out and opened up.
Well, I must confess a fondness for opossums New World marsupials , so much less charismatic than kangaroos and koalas, but with their own unique adaptations. Several opossum species, for example, eat venomous snakes. Snake-venom resistance is a biochemical, not a morphological adaptation, and it is another example of convergent evolution: besides opossums, mongooses and hedgehogs are also snake-venom resistant.
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