[pirate] Ahar, it works like this mateys, we've always know 'bout thee scurvey rodents of South America, and big blighters they be. Ye see, South America was seperated from North America by varying degrees until about the pliocene, arrrr. Being thus seperated, it took on tremendously different fauna, Saouth America's most recent matey's had been Antarctica and Australia in the paleocene, so a wierd lot of landlubbers were aliven there.
In the miocene the marsupials, arrrr, dominated many of the niches to an extent seen only elsewhere in Australia. Elsewhere the marsupial's clunkier reproduction process, which limited their brain size, among other factors, meant that placental keel hauled them and replaced them.
What's this got to do with giant scurvey mice you ask? Well I'll tell you, me hearteys, in South America the niches that would have otherwise been taken by ungulates couldn't because there were no ungulates thar. Some fauna drifted ashore from North America, like primates, the monkeys being worthy seaman, and the little swabs going on the account in search of Southern Booty.
But fer the most part, different groups evolved to take status as dominant land mammals. Sometimes these groups displayed an uncanny resemblace to their nothern contemporaries. See the pyrotheres, remarkably elephant-like mammals. But the son-of a biscuit eater rodents take the cake.
Because rodent's be so adaptable, what were oncel little bilge rats became huge, think capybara on steroids. Today's guinea pigs and relatives are the descendants of this evolution, a shameful remenant of a family of rodents that got three fathoms long. Aye, t'was a great day for scurvey rats, the miocene.
This be the biggest and baddest of the bunch. A corsair rat, ready to take on any tree o' the Spanish main. if yee be interested in other Southern oddities, look into notoungulates, borhyeanids, giant sloths, phorusrhacids, glyptodonts, teratorns, liptoterns and thylacosmilids.
Lastly mateys take a look at yer little bilge rats. You see the potential? Arrr.
[/pirate]
