Waterhouse's swamp rat (''Scapteromys tumidus'') is a semiaquatic

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

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from

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. It is found in southern

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and northern

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, where it lives in freshwater and salt marshes, as well as open grassland of the pampas. Its karyotype has 2n = 24, substantially lower than its closest relative '' S. aquaticus'' with 2n = 32.

References

Scapteromys Mammals described in 1837 {{Cricetidae-stub