Gondwana ‘wellspring’ of mammalian evolution, not Laurasia: Research

Gondwana ‘wellspring’ of mammalian evolution, not Laurasia: Research

Subject :Science and Technology

Context:

• Mammals may have evolved in Gondwana, the southern landmass formed from the supercontinent Pangaea millions of years, rather than its northern counterpart Laurasia, according to new research.

More about the research:

• The researchers studied the molars of fossils found in Madagascar, South America and India and dated the fossils to be around 50 million yearsolder than similar remains found in the northern hemisphere.
  • Madagascar, South America and the Indian subcontinent were part of Gondwana along with Africa, South America and Australia
  • Europe, Asia (excluding India) and North America formed Laurasia.
• The research indicates that Theria (a subgroup of mammals) evolved in Gondwana, thriving and diversifying there for 50 million years before migrating to Asia during the early Cretaceous. Once they arrived in Asia they diversified rapidly, filling many ecological niches.
• Australia’s current status as a ‘marsupial paradise’ is proof that the findings could be true. The world’s smallest continent is home to the greatest mammalian diversity in the world, more than any other continent.
  • Half of the over 350 native mammals of Australia are marsupials including kangaroos, wombats, koalas, and Tasmanian devils.
  • There are also montremes and placentals like bats and rodents.
• The highest number of mammalian extinctions in the world has also happened in Australia.
  • Human habitation, the rapid rate of climate change, the destruction of habitat and the introduction of exotic species were responsible for this.

About mammals:

• Modern mammals consist of three subgroups:

1. Montremes,
2. Marsupials and
3. Placentals.

• Montremes are primitive mammals that lay large eggs and have a common opening for the urogenital and digestive systems. Montremes include the platypus and echidna of Australia.
• Marsupials are mammals whose young are born incompletely developed. They develop inside a pouch on the mother’s belly. Marsupials are mostly found in Australia and New Guinea.
• The third subgroup is placentals which carry the foetus until a late stage of development. Placentals comprise the majority of mammals including humans.