The Capybara (Hydrochoerus hydrochaeris) is the largest of all rodents. (It should be noted that the now extinct rodent Phoberomys pattersoni was significantly bigger.) Full-grown Capybaras reach between 105 and 135 cm in length, and weigh 35 to 65 kilos. They are native to most of the tropical and temperate parts of South America east of the Andes, always near water. It is the only member of its family, Hydrochoeridae. (...)
When Spanish missionaries first found Capybaras in Brazil during the 16th century, they wrote to the Pope for guidance, saying "there is an animal here that is scaly but also hairy, and spends time in the water (the capybara has webbed feet to facilitate its aquatic habit) but occasionally comes on land; can we classify it as a fish?" The question was significant, as the Catholic faith forbids eating meat during Lent. Having a second hand description of the animal (and not wanting the petitioners to turn away from Catholicism), the Pope agreed and declared the Capybara a fish. [continue]
That's from Wikiupedia's Capybara page, which I found through a link over here at Irish Elk. (And thanks, Irish Elk, for your kind comments about Mirabilis.ca.)
There are lots of good capybara photos here.
Related links:
Rainforest Live: Capybara
Animal Planet: Capybara
A capybara in South Africa