In a new study, biologists laid to rest a century-old debate by confirming that a single species of frog, out of the more than 7,000 living today, has true teeth on its lower jaw. The culprit, a large marsupial frog named Gastrotheca guentheri, has puzzled scientists since its discovery in 1882 for possessing what appeared to be a complete set of jagged, daggerlike teeth on the top and bottom of its mouth.