List compiled by Rebecca Jacobson. Read our full Science Wednesday report.
They have lungs, but they breathe completely through pores in their skin. Their name Cryptobranchus means "secret gill." They are the third largest species of salamanders in the world, growing to over two feet long and weighing over four pounds. Their closest relatives live in China and Japan, but hellbenders are the last of their genus. They can live into their 50s in captivity -- that's ancient for an amphibian. Unlike other salamanders, they can't regrow their limbs. Biologists "tagged" hellbender salamanders captured in the 1990s by clipping off one of the amphibian's toes. They are loyal to their rocks. An individual hellbender's range is less than half a square mile, and the salamanders have been found under the exact same rocks year after year. Males create and guard the nests but they also eat the eggs. Contrary to popular belief, they are not poisonous, but their teeth are still sharp enough to break human skin. They have an amazing sense of smell. Kim Terrell, a postdoctoral researcher at the Smithsonian's National Zoo, says a tiny drop of earthworm scent in a 40 gallon tank sends the hellbenders in her lab scrambling out from under their rocks looking for the food. They hunt like eels, lurking under heavy rocks and lunging at crayfish, worms, and small fish. And their gullet is enormous -- they can swallow fish almost as long as themselves. No one is sure how they got their name, but one theory is that fishermen named them hellbenders because they look "like they crawled out of hell and are bent on going back." They are also called "mud cats," "devil dogs" and "snot otters" -- named for the mucus they secrete through their skin when threatened. Fossil records date the existence of hellbender salamanders to more than 160 million years ago.