Some turtles pee out their mouths; others breathe through their butts
Two recent news stories demonstrate that some turtles are wired backwards. According to the National Geographic, some species of soft shelled turtles in China pee out of their mouths. Researchers had previously noticed that the turtles had gill-like structures in their mouths, which they naturally assumed were used for additional breathing help when submerged in deep puddles and lakes.
However, it turns out that these "gills" are actually used for expelling urine. Scientists noticed that the turtles would frequently stick their heads into a puddle and waggle their tongues around. Obviously there would be no need to do this to breathe, since the turtles had fully functional lungs.
They purchased several turtles from a market, and kept them in tanks. After six days, the turtles had expelled very little urine from their backsides. But when the researchers gave the turtles a puddle of shallow water, bingo: the turtles stuck their heads in the water and waggled their tongues around, and used the water as a "mouth rinse" to expel urea.
