Parallel evolution is the independent evolution of similar traits, starting from a similar ancestral condition.

Frequently this is the situation in more closely related lineages, where several species respond to similar challenges in a similar way.

One of the most spectacular examples of parallel evolution is provided by the two main branches of the mammals, the placentals and marsupials, which have followed independent evolutionary pathways following the break-up of land-masses such as Gondwanaland roughly 100 million years ago.

In South America, marsupials and placentals shared the ecosystem (prior to the Great American Interchange); in Australia, marsupials prevailed; and in the Old World the placentals won out.

However, in all these localities mammals were small and filled only limited places in the ecosystem until the mass extinction of dinosaurs forty million years later.

At this time, mammals on all three landmasses began to take on a much wider variety of forms and roles.

While some forms were unique to each environment, surprisingly similar animals have often emerged in two or three of the separated continents.

Examples of these include the litopterns and horses, whose legs are difficult to distinguish; the European sabre-tooth tiger (Smilodon) and the South American marsupial sabre-tooth (Thylacosmilus); the Tasmanian wolf and the European wolf; likewise marsupial and placental moles, flying squirrels, and (arguably) mice..

For more information about the topic Parallel evolution, read the full article at Wikipedia.org, or see the following related articles:

Marsupial — Marsupials are mammals in which the female typically has a pouch in which it rears its young through early infancy. They differ from placental ...  > read more

Convergent evolution — In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar ...  > read more

Smilodon — Smilodon means knife tooth, an entirely appropriate name given its enormous fangs. The smilodon species are also known as Saber-Toothed Cats (which ...  > read more

Evolution of the horse — The evolution in the structure of their teeth, odd-toed limbs, obvious mobility of the upper lip, and other aspects, joins the horse to the ...  > read more

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