Changes

An excellent swimmer, the platypus spends much of its time foraging for [[food]] in water.  It swims with an alternating left-to-right paddling of its front feet.  Despite all four of its feet being webbed, its hindfeet remain held against its body, instead being used for steering (along with its tail) rather than propulsion.

An excellent swimmer, the platypus spends much of its time foraging for [[food]] in water.  It swims with an alternating left-to-right paddling of its front feet.  Despite all four of its feet being webbed, its hindfeet remain held against its body, instead being used for steering (along with its tail) rather than propulsion.

The platypus (and its fellow [[monotreme]] the [[echidna]]) was believed to have evolved in isolation 225 million years ago when the land mass that would become [[Australia]] (Gondwana) broke away from the other continents. This idea of [[evolution]] in isolation followed the theory of [[Darwin]], whose affinity for evolution may also have been influenced by his early studies of the platypus during his time on The Beagle.

The platypus (and its fellow [[monotreme]] the [[echidna]]) was believed to have evolved in isolation 225 million years ago when the land mass that would become [[Australia]] (Gondwana) broke away from the other continents. This idea of [[evolution]] in isolation followed the theory of [[Charles Darwin]], whose affinity for evolution may also have been influenced by his early studies of the platypus during his time on The Beagle.

However, the isolation theory was overturned when, in the early 1990s, three platypus teeth were discovered in South America - virtually identical to fossil platypus teeth found in Australia. (Marsupials, too, were once considered to be exclusive to Australia, but their [[fossils]] have now been found on every continent). Modern adult platypuses do not have [[teeth]], but the discovery of platypus fossils in Australia had already identified that their ancestors did indeed have unique and distinctive teeth.

However, the isolation theory was overturned when, in the early 1990s, three platypus teeth were discovered in South America - virtually identical to fossil platypus teeth found in Australia. (Marsupials, too, were once considered to be exclusive to Australia, but their [[fossils]] have now been found on every continent). Modern adult platypuses do not have [[teeth]], but the discovery of platypus fossils in Australia had already identified that their ancestors did indeed have unique and distinctive teeth.